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. 2020 Nov 19;15(11):e0242513. doi: 10.1371/journal.pone.0242513

In utero exposure to protease inhibitor-based antiretroviral regimens delays growth and developmental milestones in mice

Ambalika Sarkar 1, Kayode Balogun 1, Monica S Guzman Lenis 1, Sebastian Acosta 1, Howard T Mount 2,3, Lena Serghides 1,3,4,5,*
Editor: Jean-Léon Thomas6
PMCID: PMC7676697  PMID: 33211746

Abstract

Antiretroviral therapy (ART) in pregnancy has dramatically reduced HIV vertical transmission rates. Consequently, there is a growing number of children that are HIV exposed uninfected (CHEUs). Studies suggest that CHEUs exposed in utero to ART may experience developmental delays compared to their peers. We investigated the effects of in utero ART exposure on perinatal neurodevelopment in mice, through assessment of developmental milestones. Developmental milestone tests (parallel to reflex testing in human infants) are reflective of brain maturity and useful in predicting later behavioral outcomes. We hypothesized that ART in pregnancy alters the in utero environment and thereby alters developmental milestone outcomes in pups. Throughout pregnancy, dams were treated with boosted-atazanavir combined with either abacavir/lamivudine (ATV/r/ABC/3TC), or tenofovir/emtricitabine (ATV/r/TDF/FTC), or water as control. Pups were assessed daily for general somatic growth and on a battery of tests for primitive reflexes including surface-righting, negative-geotaxis, cliff-aversion, rooting, ear-twitch, auditory-reflex, forelimb-grasp, air-righting, behaviors in the neonatal open field, and olfactory test. In utero exposure to either ART regimen delayed somatic growth in offspring and evoked significant delays in the development of negative geotaxis, cliff-aversion, and ear-twitch reflexes. Exposure to ATV/r/ABC/3TC was also associated with olfactory deficits in male and forelimb grasp deficits in female pups. To explore whether delays persisted into adulthood we assessed performance in the open field test. We observed no significant differences between treatment arm for males. In females, ATV/r/TDF/FTC exposure was associated with lower total distance travelled and less ambulatory time in the centre, while ATV/r/ABC/3TC exposure was associated with higher resting times compared to controls. In utero PI-based ART exposure delays the appearance of primitive reflexes that involve vestibular and sensory-motor pathways in a mouse model. Our findings suggest that ART could be disrupting the normal progress/maturation of the underlying neurocircuits and encourage further investigation for underlying mechanisms.

Introduction

The use of ART in pregnancy has enabled a radical reduction in HIV vertical transmission [1]. Consequently, there is now a large and rapidly increasing number of children that are HIV-exposed uninfected (CHEUs). The number of CHEUs exposed in utero to ART is estimated at over 10 million globally and is increasing by 1.5 million each year [2]. In Canada, CHEUs under 12 years of age number at 2,500 and the population is growing by 200–300 annually [2]. Although most CHEUs are in good health, concerns remain about the effects of in utero exposure to ARTs for which, pregnancy-relevant safety/toxicity data are limited. Observational cohort studies suggest that CHEUs may be at increased risk of adverse health outcomes including higher incidence of pre-term birth and growth restriction [3], poorer early-life height and weight growth outcomes [4], increased morbidity and mortality in the first year of life [5], increased susceptibility to infection [6, 7], language and cognitive delays [8, 9], retention of primitive reflexes [10], and other neurological impairments [11, 12]. An observed decline in IQ scores in CHEUs followed in a longitudinal study at 3.5 and 5.5 years of age suggested that some of the negative effects of ART exposure, may not be visible in infancy but may emerge over time [13]. Systematic reviewing of literature has identified delayed cognitive and executive developments in CHEUs [14, 15]. Delayed emergence of language, hearing, and lower scores in socioemotional domains on the Bayley Scale III have been observed in several studies, particularly in CHEUs exposed to protease inhibitor (PI)-based regimens [11, 12, 16]. Investigating neurocognitive outcomes in CHEUs is challenging and results can be influenced by confounding factors such like HIV disease severity, maternal mental health, and education level, family environment and socioeconomic status [15, 17]. In fact, methodological shortcomings such as absence of appropriate control groups in many studies have rendered them inconclusive. However, after careful adjustment for confounding factors, evidence suggests that in utero ART (U-ART) exposure comprising of various classes of antiretrovirals are capable of delaying growth and neurocognitive development in CHEUs.

Delayed emergence of neurocognitive abilities generally indicates delayed growth/maturation of the underlying neurocircuits [18]. For early prediction of disabilities that may emerge later in life, it is important first and foremost to identify delays in the development of postnatal milestones in newborns exposed to ART in utero. We hypothesized that ART in pregnancy alters the in-utero environment for the developing fetal brain, which in turn leads to altered developmental milestone outcomes in neonates. To test this hypothesis we used a mouse model of in utero ART exposure and examined the effects of two nucleoside reverse transcriptase inhibitor (NRTI) backbones abacavir plus lamivudine (ABC/3TC) and tenofovir disoproxil fumarate plus emtricitabine (TDF/FTC) in combination with the ritonavir-boosted PI atazanavir (ATV/r), on somatic growth and primitive reflexes in mouse pups. Both these combination regimens are recommended for use in pregnancy, and ATV/r exposure has been linked to delayed language and socio-emotional development in CHEU cohort studies [11, 12, 16]. Using a mouse-model allowed us to examine the effects of U-ART in offspring in the absence of maternal, environmental, and HIV-related confounders.

Materials and methods

Animals

C57BL/6J mice, 10 males, 50 females (Jackson Laboratories, USA) were used for breeding at 10 weeks of age (1 male × 2 females, per cage). Animals were maintained under standard laboratory conditions with ad-libitum access to food and water and 12 h light/dark cycle. All animal experiments were performed with the approval of the Toronto Centre for Phenogenomics (TCP) Animal Care Committee, based on national guidelines of the Canadian Council for Animal Care (CCAC).

Treatment of the dams

Female mice were trained for oral gavage (feeding needle size: 20Gx38 mm) with water for a week prior to mating, to avoid losing pregnancy from gavage related stress. The morning after mating (gestational day (GD) 0.5), plugged females were separated from males, randomly assigned to one of the two treatment arms and administered either ABC/3TC+ATV/r (100/50mg/kg/day + 50/16.6mg/kg/day) or TDF/FTC+ATV/r (33.3/50mg/kg/day + 50/16.6mg/kg/day) by oral gavage, or control which received an equal volume of water. Drugs were acquired by prescription, crushed, and suspended in sterile water. Dosing was determined through previous experiments [19] and is known to lead to peripheral drug levels equivalent to those seen in pregnant women. On GD18, pregnant dams were separated into individual cages where they delivered their litters. Upon delivery of litters (Postnatal day 0), dams stopped receiving treatment. On P1 large litters were culled down to 6 pups/litter in order to maintain uniformity in handling time during testing.

Pup handling

From postnatal day 1 (P1) onwards, pups were assessed daily for appearance of developmental milestones as described by Hill et al, 2008 [20]. Dams were gently removed from their home cages and held in a separate room while each litter was tested. Litters were removed from the cages and placed in weighing boats, lined with tissue papers and were kept on heating pads to ensure that pups retained their body temperatures. Pups in each litter were individually weighed and measured for body length and visually examined for somatic developments: appearance of fur, teeth, opening of eyes and pinna detachment. Each day (between 10:00–15:00hrs), each pup was evaluated on a battery of tests that assessed reflex development and attainment of milestones that were appropriate for their age (S1 Fig), by individuals blind to treatment groups, working in pairs. After testing, pups were returned to their nests and reunited with the dams. A total of 145 pups (83 males and 62 females) from 25 different litters were tested for developmental milestones. Pups were allowed to grow into adulthood after completion of the milestones study. At 2 months of age, animals were tested for activity in the open field test (OFT).

Developmental milestone procedure

Surface righting (P1-P13): Pups were individually held on their backs (supine position), with paws facing upwards. Time taken by pups to flip over onto their abdomens (acquire prone position) were noted. Test was terminated if the pup failed to turn over within 30 seconds. Surface righting was measured once daily until the pup could right itself in less than 1second for two consecutive days. A mature response is expected between P8–P10 [21]. The human equivalent of this test is the tonic labyrinthine reflex seen in babies between 0–6 months of age [22].

Negative geotaxis (P1-P14): Pups were individually placed on a wire mesh set at a 45° angle with heads facing downwards. Time taken to turn around by 180° and move upwards was recorded. Test was repeated daily until pups passed in <30s for two consecutive days. Mature response in this test is expected by P3–P5 [20].

Cliff aversion (P1-P14): Pups were positioned on the edge of a small box with forepaws and the snout hanging over the edge. Time taken to turn and crawl away from the edge was noted. Test was repeated daily until pups passed in <30s for two consecutive days. Mature response expected by P4–P5 [20, 23].

Rooting (P1-P12): Pups were gently stroked with the twisted filament of a cotton tip applicator along the side of the head. A positive response was noted if the pup moved its head toward the filament. Test was repeated daily until pups responded correctly for two consecutive days. Mature response in this test is expected by P4–P5 [20, 21]. The human equivalent of this is the rooting reflex (for suckling) observed in babies between 0–4 months of age [24, 25]

Forelimb grasp (P4-P14): Pups were held with their forelimbs grasping a wire bar, while hindlimbs were not in touch with any surface. Length of time pups were able to hold onto the bar and remain suspended was noted. Test was repeated daily until pups were able to stay suspended for a minimum of 1s for two consecutive days. Mature response expected by P8-P9 [20, 21]. The human equivalent for this is the palmar grasp reflex observed in babies between 0–5 months of age [25, 26]

Auditory startle (P7-P18): Pups were individually exposed to an acoustic stimulus (hand clapping, 10 inches away from the pup). The first day on which pups responded with a quick involuntary jump was noted. Mature response expected by P10-P14 [20]. The humans, startle reflexes are observed between 0–5 months of age [26].

Ear twitch (P7-P15): The fine filament of a cotton tip applicator is gently brushed against the tip of the pup’s ear. Positive responses were noted if pups responded by flattening their ears. Test was repeated daily until pups responded correctly for two consecutive days. Mature response expected by P9–P10 [20].

Open field traversal (P8-P21): Tests straight line walking in pups, as opposed to pivoting. Each pup was placed at the centre of a circular arena (diameter = 13cm). Latency to move out of the arena was recorded. Test was repeated daily until pups walked out of the arena in <30s for two consecutive days. A mature response in this test is expected by P10-P13 [27].

Air righting (P8-P21): Pups were held on their backs (with four paws turning upwards), 10cm above a cotton pad, and released. Reflex was considered mature when the pup turned its body during the fall and landed on its paws. Test was repeated daily until pups landed on all four paws for two consecutive days. Mature response in this test is expected by P10-P12 [20].

Olfaction (the homing test): On P11, individual pups were transferred to a test cage layered two-third with clean and one-third with soiled bedding from the home-cage. The pup was placed in the middle of the chamber and allowed to wander. Homing was considered successful if the pup moved over and stayed in the portion of the cage that contained soiled home-cage bedding within 2.5 mins [21].

Open field test in adulthood

Control and U-ART animals (n = 12–17 per group, per sex) were tested for general activity and anxiety-like behavior in the open field using Activity Monitor (Med Associates Inc, Fairfax, USA). Horizontal and vertical activity of mice were monitored by photo-beam channels in the open field (40 × 40 × 40 cm), for a period of 15 mins. A centre (20 x 20 x 20 cm) and a periphery were demarcated virtually within the open filed arena using the Activity Monitor software. Automated tracking was used to score time spent and distance moved in the centre and in the periphery of the arena, vertical (rearing) activity, resting time and speed of movement of the mice.

Statistical analysis

An N = 83 male and N = 62 female pups from 6–10 different litters were assessed per arm for all developmental milestone tests. Data are presented as means with standard errors. All analyses were performed stratified by sex. Using a mixed-effects model that included treatment as a fixed effect and litter as a random effect, we explored associations between developmental outcomes and treatment accounting for litter effects. Differences in weight and length were assessed for each day, stratified by sex, accounting for litter effects as above. Differences in the homing test were examined using chi-square test. An N = 12–17 per sex per arm were used in the OFT. Statistical difference in the OFT were assessed using one way ANOVA with Bonferroni multiple comparison test. A p<0.05 was deemed significant. STATA v.13.0 (StataCorp Ltd., USA) and Prism v.5 were used for all analyses. All raw data are provided in S1 Data.

Results

We assessed pups daily for physical growth parameters and on a battery of tests for primitive reflexes including surface-righting, negative-geotaxis, cliff-aversion, rooting, ear-twitch, auditory-reflex, forelimb-grasp and air-righting, and for behaviors in the neonatal open field, and olfactory test. Given the fact that key developmental milestones are conserved between different mammalian species [28, 29], we have provided a comparison of the major neurodevelopmental events in mice and humans in Fig 1 along with the timeline of our treatments and tests, for better contextualization of the study presented here.

Fig 1. Comparative timelines of neurodevelopment and reflex maturation in mice and humans.

Fig 1

Shown is the timeline for major neurodevelopmental events and reflex maturation in mice (A) and in humans (B) and a schematic representation for the experimental design in mice (A). Pregnant dams received ART from embryonic day 0.5 to E20 (till birth of pups). Developmental milestones were assessed in pups daily from P1 to P21. Being altricial in nature, a considerable amount of neurodevelopment occurs in mice pups postnatally. Timing of neurogenesis, maturation and migration of neuronal processes have been depicted using shaded rectangles for both species. Postnatal days on which mature responses are normally expected for specific reflex tests in mice have been shown with pointers in (A). Comparable reflexes in human infants and the timing for maturation and disappearance of these reflexes have been shown in (B).

Mortality

Since increased mortality in the first year of life has been observed with CHEUs we first examined pup survival in the post-natal period [2]. We observed no mortality in the control group, with all pups surviving for the entirety of the experiment. In the ATV/r/ABC/3TC group we observed a 3% mortality rate (2 of 66 pups, 2 of 9 litters with at least one mortality) and in the ATV/r/TDF/FTC groups we observed a 6.4% mortality rate (5 of 78 pups, 4 of 10 litters with at least one mortality). The mortality rate did not differ significantly between groups (p = 0.14 by χ2 test). All pup death occurred on P0, with no pup loss observed after P0 in any group.

Somatic development

Somatic development was assessed in control and U-ART pups by measuring body weights, body lengths, and visual inspection for detachment of pinna, the appearance of fur, opening of eyes, and eruption of incisors.

Pups exposed in utero to ATV/r/ABC/3TC and ATV/r/TDF/FTC showed significantly lower birth weights as compared to controls (Fig 2A–2C). Weights of male pups exposed to ATV/r/ABC/3TC were lower than that of controls on P1 (p = 0.002). Similarly, weights of male pups exposed to ATV/r/TDF/FTC were significantly lower than that of controls on P1 (p = 0.001) and P2 (p = 0.019) (Fig 2A). Weights of female pups exposed to ATV/r/ABC/3TC or ATV/r/TDF/FTC were significantly lower than that of controls on P1 (p = 0.001, p<0.0001 respectively) and P2 (p = 0.05, p = 0.039 respectively) (Fig 2C). U-ART pup body weights in both sexes reached control levels by P3 (Fig 2B and 2D).

Fig 2. Pups exposed in-utero to ART are born small and weigh less for gestational age.

Fig 2

Pup weight and length were assessed daily from postnatal day 1–21. Weight for the first 5 day is shown in (A) for males and (C) for females. Weight for the entire course is shown in (B) for males and (D) for females. Length is shown in (E) for males and (F) for females. Data are mean ± SEM (n = 11–34 pups/group). A mixed effects model was used to examine differences at each day between control and treatment arms (fixed effect) accounting for litter effects (random effect). *p<0.05 vs. control. ATV/r, ritonavir-boosted atazanavir; ABC, abacavir; 3TC, lamivudine; TDF, tenofovir; FTC, emtricitabine; CTRL, control.

No remarkable difference in body length was observed between groups in male pups exposed to either treatment regimens (Fig 2E). Body lengths of female pups exposed to ATV/r/ABC/3TC were significantly lower than that of controls from P1 (p = 0.03) till P5 (p = 0.043) (Fig 2F). Body length did not differ in females exposed to ATV/r/TDF/FTC compared to control (Fig 2F).

In C57BL/6 mice, the expected timeline for detachment of pinna is P3-P4, for appearance of fur is P6-P7, for eruption of incisors is P10-P12 and for opening of the eyes is P11-P13 [30], and this coincided with findings in our control group. Delay in detachment of pinna was observed in the ATV/r/ABC/3TC exposed female pups (p = 0.004) and the ATV/r/TDF/FTC exposed male (p<0.0001) and female (p = 0.002) pups (Fig 3A). No significant differences were observed between treatment groups in appearance of fur (Fig 3B), opening of eyes (Fig 3C), and incisors eruption (Fig 3D).

Fig 3. In-utero exposure to ART delays somatic development.

Fig 3

Postnatal day of pinna detachment (A), fur appearance (B), eye opening (C), incisor eruption (D) for male and female pups exposed in-utero to control (CTRL, white bars), ATV/r/ABC/3TC (light grey bars), or ATV/r/TDF/FTC (dark grey bars). Data are mean ± SEM (n = 11–34 pups/group). A mixed effects model was used to examine differences between control and treatment arms (fixed effect) accounting for litter effects (random effect) stratified by sex. *p<0.05 compared to control males. $p<0.05 compared to control females. ATV/r, ritonavir-boosted atazanavir; ABC, abacavir; 3TC, lamivudine; TDF, tenofovir; FTC, emtricitabine; CTRL, control.

Taken together, our results show that U-ART pups are born small for gestational age and have delayed somatic growth during the first two postnatal days. U-ART pups managed to catch-up with the controls in measures of somatic growth around P3. A slight delay in pinna detachment was observed but generally, somatic development milestones in U-ART pups were similar to controls.

Development of primitive reflexes

We assessed the development of neurological reflexes in U-ART and control pups. In utero exposure to ATV/r/ABC/3TC and ATV/r/TDF/FTC delayed the emergence of negative-geotaxis and cliff-aversion reflexes in male and female pups (Fig 4A and 4B). Mature responses are expected in these tests normally by P4 and P5 respectively [20, 23], as seen in our control group. In most U-ART pups, mature responses were not observed before P6. In utero exposure to ATV/r/ABC/3TC delayed emergence of negative-geotaxis in male pups approximately by 2 days (p = 0.01) and in females by 2.5 days (p = 0.001) (Fig 4A). Similarly, exposure to ATV/r/TDF/FTC delayed the appearance of negative-geotaxis in male pups approximately by 2 days (p = 0.008) and in females by 2.5 days (p = 0.001) (Fig 4A). In utero exposure to ATV/r/ABC/3TC delayed emergence of cliff-aversion in males (p = 0.012) and females (p = 0.004) approximately by 2 days (Fig 4B). Similarly, in utero exposure to ATV/r/TDF/FTC delayed the appearance of cliff-aversion in both males (p = 0.012) and females (p = 0.004) approximately by 2 days (Fig 4B).

Fig 4. In-utero exposure to ART delays development of certain primitive reflexes.

Fig 4

Postnatal day of successful acquisition of negative geotaxis reflex (A), cliff aversion reflex (B), rooting reflex (C), ear twitch reflex (D), and forelimb grasp reflex (E) for male and female pups exposed in-utero to control (CTRL, white bars), ATV/r/ABC/3TC (light grey bars), or ATV/r/TDF/FTC (dark grey bars). Data are mean ± SEM (n = 11–34 pups/group). A mixed effects model was used to examine differences between control and treatment arms (fixed effect) accounting for litter effects (random effect) stratified by sex. *p<0.05 compared to control males. $p<0.05 compared to control females. Percentage of pups that successfully completed or failed the olfaction homing test on postnatal day 11 is shown in (F). * p<0.05 vs. control by chi-squared test. ATV/r, ritonavir-boosted atazanavir; ABC, abacavir; 3TC, lamivudine; TDF, tenofovir; FTC, emtricitabine; CTRL, control.

Development of rooting, a tactile reflex, was delayed selectively in the male pups exposed in utero to ATV/r/ABC/3TC (p = 0.023) or ATV/r/TDF/FTC (p = 0.017) approximately by a day (Fig 4C). In female pups, rooting was unaffected by exposure to either treatment regimens (Fig 4C).

Development of ear twitch, another tactile reflex, was also delayed in the male pups exposed to ATV/r/TDF/FTC (p = 0.001) and in females exposed to ATV/r/ABC/3TC (p = 0.028) as well as ATV/r/TDF/FTC (p = 0.001) (Fig 4D) by 1–1.5 days.

In utero exposure to ATV/r/ABC/3TC delayed the development of forelimb grasp reflex, selectively in females (p = 0.002) approximately by a day (Fig 4E). Forelimb grasp was not affected in males exposed to either treatment regimen.

Performance in the homing test, an olfaction test, was poorer than control in U-ART males, although only male pups exposed to ATV/r/ABC/3TC reached significance (p = 0.01) (Fig 4F).

A few primitive reflexes were unaltered by U-ART. No significant differences were noted between treatment groups for the appearance of surface-righting, auditory-reflex, air-righting, and straight-line walking, assessed by open field traversal test (Fig 5).

Fig 5. In-utero exposure to ART does not disrupt the development of every primitive reflex.

Fig 5

Postnatal day of successful acquisition of surface righting reflex (A), auditory reflex (B), air righting reflex (C), and open field traversal (D) for male and female pups exposed in-utero to control (CTRL, white bars), ATV/r/ABC/3TC (light grey bars), or ATV/r/TDF/FTC (dark grey bars). Data are mean ± SEM (n = 11–34 pups/group). A mixed effects model was used to examine differences between control and treatment arms (fixed effect) accounting for litter effects (random effect) stratified by sex. No statistically significant differences were observed. ATV/r, ritonavir-boosted atazanavir; ABC, abacavir; 3TC, lamivudine; TDF, tenofovir; FTC, emtricitabine; CTRL, control.

Taken together, our results show that U-ART regimens induced delays in the development of certain primitive reflexes, especially the ones that are reflective of sensory-motor, tactile, and neuro-muscular developments of the nervous system. A summary of the findings is shown in Table 1.

Table 1. Summary of differences in developmental milestone findings for each ART regimen compared to control.

Days delay vs. control ATV/r/ABC/3TC ATV/r/TDF/FTC
Male Female Male Female
Negative geotaxis 2 days delay 2.5 days delay 2 days delay 2.5 days delay
Cliff aversion 2 days delay 2 days delay 2 days delay 2 days delay
Rooting 1 day delay No delay 1 day delay No delay
Outer ear opening No delay 0.5 day delay 0.5 day delay 0.5 day delay
Ear twitch No delay 1 day delay 1.5 days delay 1.5 days delay
Forelimb grasp No delay 1 day delay No delay No delay
Surface righting No delay No delay No delay No delay
Air righting No delay No delay No delay No delay
Auditory reflex No delay No delay No delay No delay
Open field traversal No delay No delay No delay No delay
Eyes opening No delay No delay No delay No delay
Incisors eruption No delay No delay No delay No delay
Fur appearance No delay No delay No delay No delay
Olfaction Deficit present No deficit No deficit No deficit

ATV/r, ritonavir-boosted atazanavir; ABC, abacavir; 3TC, lamivudine; TDF, tenofovir; FTC, emtricitabine.

Behavioural performance in adulthood on the OFT

To investigate the consequences of delayed milestones development in adulthood, we tested mice for general activity, exploration, speed of locomotion, and anxiety-like behavior in the OFT. Our results showed no significant differences between treatment arms for speed, total distance moved, distance and ambulatory time in the centre and the peripheral zones of the arena, and rearing and resting (Fig 6A–6H) in males. In females, no significant differences were noted between treatment groups for speed of locomotion (Fig 6A) and rearing (vertical counts) (Fig 6G). Differences were observed in total distance moved in the entire arena (p = 0.03) (Fig 6B), in the centre (p = 0.06) (Fig 6C) and in the periphery (p = 0.04) (Fig 6D), ambulatory time spent in the centre (p = 0.03) (Fig 6E) and in periphery (p = 0.07) (Fig 6F) for females. After correcting for multiple comparisons, the ATV/r/TDF/FTC exposed females demonstrated significantly lower total distance travelled and less ambulatory time in the centre compared to controls. Differences were also observed in resting time in females (p = 0.03, Fig 6H), with significantly higher resting times observed in the ATV/r/ABC/3TC exposed females compared to controls.

Fig 6. In-utero exposure to ART alters behaviour in the open field test in adulthood.

Fig 6

Speed of locomotion (A), total distance moved (B), distance moved in the centre of the arena (C), distance moved in the periphery (D), ambulatory time in the centre of the arena (E), ambulatory time in the periphery (F), rearing time (G), and resting time (H) for male and female mice exposed in-utero to control (CTRL, white bars), ATV/r/ABC/3TC (light grey bars), or ATV/r/TDF/FTC (dark grey bars). Data are mean ± SEM (n = 12–17 mice/group). One-way ANOVA with Bonferroni multiple comparisons tests was used to examine differences between control and treatment arms for each sex. $ indicates p<0.05 compared to control females. ATV/r, ritonavir-boosted atazanavir; ABC, abacavir; 3TC, lamivudine; TDF, tenofovir; FTC, emtricitabine; CTRL, control.

Discussion

We have shown here for the first time that gestational exposure to PI-based antiretroviral regimens delays somatic growth and the appearance of primitive reflexes in mouse pups. Pups of either sex, exposed to ATV/r/ABC/3TC, and ATV/r/ TDF/FTC exhibited lower birth weights, body lengths, and delays in the appearance of negative-geotaxis and cliff-aversion reflexes. Exposure to either regimen delayed the appearance of rooting reflex in the male pups. Exposure to ATV/r/ABC/3TC alone delayed appearance of the olfactory reflex in males and forelimb grasp in female pups. Exposure to ATV/r/TDF/FTC delayed outer ear detachment and ear-twitch response in both sexes. Surface-righting, air-righting, auditory-reflex, and open field traversal were unaffected by either regimen. The appearance of fur, eyes, and incisors were also not affected by in utero exposure to either regimen.

In our study, we treated pregnant dams with clinically relevant doses of ATV/r/ABC/3TC and ATV/r/TDF/FTC from GD 0.5 till delivery; a time window that approximately corresponds to gestational weeks (GW) 1–24 in humans [28, 29]. Perturbations of the in utero environment during the first trimester of pregnancy are known to have life-long impacts on offspring brain and behavior [31]. First-trimester exposure to PI-based ARTs have indeed been associated with higher incidences of abnormalities related to growth [32], sensory [33] and neurocognitive behaviors [34] in CHEUs.

Key developmental events that mark this critical period are conserved in mammals. This allows translation of early neurodevelopmental milestones between species (Fig 1). For instance, developmental milestones such as neurulation begins on GD9–9.5 in mice and GD24-28 in humans. Neurogenesis, gliogenesis, synaptogenesis, and myelination continue postnatally in both species. At P10 the rodent brain is comparable to that of a term infant and by P20, it corresponds to that of a human, 2–3 years old [28]. Certain developmental processes such as maturation of specific neuronal regions can be temporally correlated to the appearance / disappearance of primitive reflexes in neonates [35]. For example, cortical inhibition of the brain stem around 3 months of age is known to correspond to the disappearance of palmer grasp in babies, a reflex similar to forelimb grasp in rodents and non-human primates [36, 37]. Owing to the conservation of developmental events, the age at which certain behaviors occur in rodents can be mapped onto that of humans.

Mice exposed to ATV/r/ABC/3TC and ATV/r/ TDF/FTC were born with significantly lower birth weight and length compared to controls. These signs of retarded somatic growth, however, lasted only till P3. Our results corroborate clinical findings that have shown HEU infants to have significantly lower body weights and lengths at birth [3, 4], with catch up growth by 6 months of age [4], although some studies have shown persistent growth defects in CHEUs [31]. Differences in the type of ART exposure and socioeconomic factors may explain these differences. Slower postnatal growth was also seen previously in CD1 mice exposed to AZT and 3TC [38]. Low birth weight or being born small for gestational age (SGA) may be indicators of altered in utero environments and/or placental insufficiencies [39]. Maternal treatment with ARTs could influence the fetus directly (mitochondrial and neuronal toxicity) [40, 41], or indirectly (altered maternal hormonal systems and placental environment) [42] and thereby regulate growth. Growth restricted and pre-term infants are known to have higher predispositions for neurobehavioral and intellectual disabilities related to learning, cognition, and socialization [43]. CHEUs, having higher incidences of SGA, are also known to have worse neurocognitive outcomes when compared to unexposed children [3, 44].

A small dip in the body weights of control pups, both males and females were observed transiently at P3, although a concomitant decline in body length was not observed in these pups. It is possible that the transient weight loss (thinning, but not stunting) may have occurred due to insufficient feeding/nursing/hydration of these pups on that day.

Our data suggest that reflex ontogeny is disrupted in pups exposed in utero to ATV/r/ABC/3TC and ATV/r/TDF/FTC. We assessed sensory-motor reflex development in our pups by testing for surface-righting, air-righting, negative-geotaxis, and cliff-aversion. We observed delays in negative-geotaxis and cliff-aversion with U-ART, but no delays in the righting reflexes. A mature response in all four of these tests requires coordination between the vestibular system, muscles, and spine, but surface-righting, negative-geotaxis, and cliff-aversion additionally require inputs of tactile sensations via whiskers to the somatosensory cortex [45]. For surface-righting, pups utilize sensory information from proprioceptive-tactile sources as well as from vestibular sources. For air-righting on the other hand, pups are dependent primarily on their vestibular systems [46]. The difference in timing of maturation of surface (P8) versus air-righting (P11) reflexes is reflective of the relative difference in the maturation of tactile versus the vestibular systems [46]. Both types of righting reflexes, negative-geotaxis and cliff-aversion, require the concurrent development of strength and coordination, and a delay in appearance of these reflexes could also indicate retarded muscular development and growth. Our results showed no effect of U-ART on either type of righting reflex. Interestingly, both U-ART regimens delayed the appearance of negative-geotaxis and cliff-aversion; reflexes that are dependent partly on tactile inputs to the somatosensory neural pathways [45].

Somatosensory pathway maturation was also assessed via testing for rooting reflex. Rooting, a response to tactile stimulation of the skin and whiskers on the snout was delayed by both regimens, albeit only in the male pups. Although it is difficult to pinpoint why the regimens affected the male offspring selectively for this reflex, one may speculate that the regimens impacted the underlying neurocircuitry differently in the two sexes, by neurohormonal interferences at a critical developmental phase. Given that male placentas are more responsive to changes in the maternal environment, such as maternal exposure to drugs [47], maternal ART may have impacted the male fetuses differently from the females. Previous studies suggest sex differences for the effects of gestational exposure to other NRTI regimens. In utero exposure of CD1 mice to AZT [48], 3TC [49] and AZT+3TC [38] from GD10 to GD21 delayed emergence of pole grasp reflex in males [48] and was associated with deficits in social interaction only in females at P35 [38]. Corroborating these findings, we show here a delay in the emergence of forelimb grasp selectively in female pups exposed to ATV/r/ABC/3TC treatment. Differences between ours and previous findings could be due to differences in drug regimens, duration of treatment, and strain of mice used. Collectively, the sex divergent effects of various U-ART regimens on several milestone tests strengthens the idea that U-ARTs can affect offspring neurodevelopment based on offspring sex.

Further, we show that ATV/r/ABC/3TC exposure impairs olfaction in male pups in the homing test. Failure in neonatal homing test is a hallmark for olfactory deficits in rodent models of autism spectrum disorder [50, 51]. In fact, impaired olfaction is considered a vulnerability marker for several psychiatric disorders including autism, schizophrenia and depression [52]. Because of the vast network and direct connectivity of the olfactory tract to various brain regions including the entorhinal cortex, the hippocampus, and the amygdala, a variety of vital activities such as feeding, reproduction, social behavior and memory rely on the sense of smell and are intricately interlinked. The olfactory system is also closely linked to the immune system [53]. An early impairment in olfaction could be a tell-tale sign for more deficits in other neuro-behavioral areas in the future. A significant increase in the odds for an autism spectrum diagnosis in CHEUs compared to unexposed children was reported in a retrospective study in British Columbia Canada, although an association with U-ART exposure was not observed [54].

ATV/r/ABC/3TC and ATV/r/TDF/FTC had mutually exclusive effects on some of the milestones tested. For example, concurrent delays in the opening of the outer ear and the emergence of ear-twitch responses were observed in the ATV/r/TDF/FTC group only. These effects were not observed in the ATV/r/ABC/3TC exposed group. Since ATV/r was common to both regimens, we speculate that differences in the effects of the two regimens may have risen due to differences in the composition of the NRTI backbones. Although ABC, 3TC, TDF, and FTC are all nucleos(t)ide analogs, they are different molecular entities. These viral reverse transcriptase inhibitors are known to interrupt mtDNA replication through host mitochondrial DNA-polymerase-γ (mtDNA-pol-γ) binding. Most of the clinical manifestations of NRTI toxicities resemble mitochondrial diseases resulting from mutations in mtDNA [55, 56]. Neurological disorders associated with mitochondrial dysfunction have been reported in CHEUs exposed to NRTIs [5760]. Differences in pharmacokinetics and the binding affinities of the different NRTIs to mtDNA-pol-γ [61] may explain the differences observed in their effects on the milestones tested.

We further showed that consequences of prenatal exposure to ART persist beyond postnatal ages, into adulthood. Exposure to ATV/r/TDF/FTC lowered the levels of exploration and activity in the open field in female mice. Resting or idle time was also found to be higher in females exposed to ATV/r/ABC/3TC. Although not anxiety-like, the behavioral phenotype evident in U-ART females was one of lowered overall exploration of the arena and increased resting/ idling. Decreased exploration in the OFT has been linked to abnormalities in neurotransmitter systems that regulate locomotion [62, 63], motivation and stress response [64], such as the dopaminergic, cholinergic and serotonergic systems and brain areas like the hippocampus [64], striatum and cortex [62, 63]. One previous study, testing AZT+3TC exposed CD1 mice on OFT in adulthood, had shown increased rearing and no changes in general locomotion [65]. Our results show that U-ART is not without consequences on behavior in adulthood, although the observed defects are minor. Further investigation into the long-term effects of U-ART on brain and behavior is merited.

There are several strengths to our study. We have identified the adverse effects of U-ART on early development, in the absence of clinical and socioeconomic confounding factors. Drug levels used in our study, mimic levels seen in pregnant women. Considering sex as a variable in all our investigations, we have highlighted the sex divergent effects of U-ART. The limitations of our study include the lack of HIV infection in the dams, which is not reflective of the clinical scenario. HIV infection can also alter the in utero environment and thus likely modifies the effects on perinatal ART exposure in CHEUs. Further, in our model, we only expose the pups to ART in utero, a time window that maps to GW1-24 in humans. While this time period encompasses fetal neurogenesis and migration it does not encompass the degree of maturation that occurs in human pregnancy. Thus, our results may underestimate the clinical impact.

Conclusions

The major novel finding in our study is that mice exposed in utero to ATV/r/ABC/3TC and ATV/r/TDF/FTC exhibit delays in the development of milestones, particularly in reflexes that require the ability for dynamic postural adjustments, muscular strength and are dependent on whisker based tactile stimulation of somatosensory pathways. These findings are potentially indicative of disrupted underlying neurocircuitry. The rate of maturation in mice during the first postnatal month being 150 times that of humans [66], our work suggests that even minor delays in mouse reflex developments, when extrapolated onto the human timescale, could translate into weeks or months of delay. Clinical studies have associated in utero exposure of AZT, 3TC, and nevirapine to retention (delayed disappearance) of primitive reflexes in CHEUs by several months [10]. Our work, therefore, highlights the need for investigating the persistence and the etiology of the effects of U-ART, for better understanding of the spectrum of health issues that may affect CHEUs, and for better optimization of perinatal anti-HIV regimens.

Supporting information

S1 Fig. Example of a data sheet for recording observations for the assessments of developmental milestones.

The shaded boxes mark the tests that were performed on each day. Tests were done in a sequence that was age appropriate for mice pups.

(TIF)

S1 Data. Complete raw data set.

(XLSX)

Abbreviations

3TC

lamivudine

ABC

abacavir

ART

antiretroviral therapy

ATV/r

ritonavir-boosted atazanavir

CHEUs

children that are HIV-exposed uninfected

FTC

emtricitabine

GD

gestational day

GW

gestational weeks

NRTI

nucleoside reverse transcriptase inhibitor

P1

postnatal day 1

PI

protease inhibitor

TDF

tenofovir

U-ART

in utero antiretroviral therapy

Data Availability

All relevant data are within the paper and its Supporting Information files.

Funding Statement

This work was supported by the Canadian Foundation for AIDS Research (Grant 27-010) and the Canadian Institutes of Health Research (CIHR HIV/AIDS Comorbidities Prevention and Healthy Living –Team Grant) awarded to LS. KB was supported by a CIHR Canadian HIV Trials Network fellowship.

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Decision Letter 0

Jean-Léon Thomas

2 Sep 2020

PONE-D-20-20335

In utero exposure to protease inhibitor-based antiretroviral regimens disrupts growth and developmental milestones in mice

PLOS ONE

Dear Dr. Serghides,

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Reviewer #1: Yes

Reviewer #2: Partly

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Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #2: Yes

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5. Review Comments to the Author

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Reviewer #1: In this study, Sarkar et al demonstrated for the first time using a mouse model that an antiretroviral therapy (ART), which is commonly used in pregnant women to prevent the vertical transmission of HIV-1, delays growth and neurocognitive development of the offspring, as has been suggested in humans. Therefore, this study may serve for understanding the underlying mechanisms for the adverse effects and further optimization of the ART regimens during pregnancy. The manuscript is written quite clearly and comprehensively. I have only a few suggestions.

1. In Fig. 2A and C, the body weight of both control male and female mice decreased from day 2 to day3 post-birth, although the body lengths (Fig. 2E and F) kept growing during the period. This looks unnatural for me and probably also for the readers. It is better to clarify in the manuscript whether this is commonly observed in normal pups and if not, better to address/suggest why it has happened.

2. There are some sentences in the text that “no difference (differences) was (were) observed between …”. It would be better to add words such as no “significant” difference or no “remarkable” difference etc because there are more or less differences between the groups in the data.

Reviewer #2: Sarkar et al. demonstrated that U-ART treatment delayed the development of pups via mouse model. In this manuscript, the authors utilized various development indicator to monitor the pups growth after U-ART. The results showed that the somatic development and certain primitive reflexes seemed delayed in U-ART pups. (Fig.2 &Fig.4).

Some questions were raised here after reviewing these results,

1. According to the results shown in Fig. 2-3, U-ART pups seemed to reach the average body weight and other somatic development before weaning. Did these results reflect the fact in human cases? Because the authors used “disrupt” in the title, the results did not show a significant disruption of development, for example, somatic defect, what is the fact in the human cases? Development delayed or some defects were observed in the U-ADT infants?

2. Because the authors mentioned that the mortality was higher in the first year in human cases, did the authors try to count the viability of pups between control and U-ART groups?

3. Since the development indicators cannot reflect too many differences in control and U-ART pups, did the authors try to infect with pathogens or bacterial stimulators (e.g LPS) to see if the U-ART groups were more susceptible to infections?

4. If the authors extend the monitoring window after weaning and more examinations can be utilized in the experiment, such as behavior tests, is it possible to see more differences between control and U-ART groups?

5. The author mentioned that the mtDNA is affected because of ART treatment, is it possible to do more investigation in mtDNA in U-ART pups?

Although the novelty of this manuscript is quite unique, the data here seems to be descriptive and preliminary.

**********

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Reviewer #1: No

Reviewer #2: No

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PLoS One. 2020 Nov 19;15(11):e0242513. doi: 10.1371/journal.pone.0242513.r002

Author response to Decision Letter 0


19 Oct 2020

Responses to Reviewers:

Reviewer #1: In this study, Sarkar et al demonstrated for the first time using a mouse model that an antiretroviral therapy (ART), which is commonly used in pregnant women to prevent the vertical transmission of HIV-1, delays growth and neurocognitive development of the offspring, as has been suggested in humans. Therefore, this study may serve for understanding the underlying mechanisms for the adverse effects and further optimization of the ART regimens during pregnancy. The manuscript is written quite clearly and comprehensively. I have only a

few suggestions.

1. In Fig. 2A and C, the body weight of both control male and female mice decreased from day 2 to day3 post-birth, although the body lengths (Fig. 2E and F) kept growing during the period. This looks unnatural for me and probably also for the readers. It is better to clarify in the manuscript whether this is commonly observed in normal pups and if not, better to address / suggest why it has happened.

In response to the reviewer’s comment we re-examined the body weight data for all pups. The decline in weight seen on day 3 in the controls was driven by 2 litters, which lost weight on day 3. This weight loss was transient and the pups recovered in weight on subsequent days.

Literature supports strong correlations between pup’s body weight and dam’s lactation, dam’s food intake, home cage temperature and relative humidity [1, 2]. These papers show that increases in body heat generation in lactating dams, and increase in relative humidity in cage, lowers food intake transiently which corresponds to transient dips in pup body weights. This happens in spurts across the postnatal period, with the first spurt being around P3 [2]. It is most likely that the dip in weight visible in our graph at P3 in our control group, with no concomitant decrease seen in body lengths, is merely an aberration, which could have been caused due to a transient decrease in nursing / feeding / hydration of the pups by the two dams.

We thank the reviewer for raising this question. It gave us a chance to clarify this issue in our manuscript. We have now added an explanation in the revised Discussion page 19 line 389-392.

2. There are some sentences in the text that ‘no difference (differences) was (were) observed between…’. It would be better to add words such as no ‘significant’ difference or no remarkable difference’ etc because there are more or less differences between the groups in the data.

We have now changed our sentences from ‘no differences were observed’ to ‘no remarkable or significant differences were observed’ wherever applicable, as per the reviewer’s recommendation. We have made these changes under ‘Results’ section lines 216, 236, and 294.

Reviewer #2: Sarkar et al. demonstrated that U-ART treatment delayed the development of pups via mouse model. In this manuscript, the authors utilized various development indicator to monitor the pups growth after U-ART. The results showed that the somatic development and certain primitive reflexes seemed delayed in U-ART pups. (Fig.2 & Fig.4).

Some questions were raised here after reviewing these results,

1. According to the results shown in Fig. 2-3, U-ART pups seemed to reach the average body weight and other somatic development before weaning. Did these results reflect the fact in human cases?

Several studies have reported delayed increase in body weight and other somatic developments in infants that are HEU (Reviewed in Wedderburn et al, 2019 [3]). Most studies that followed HEU children for the first 2 years of their lives have reported delayed somatic developments such as: lower birth weight [4], lower weight-for-age Z scores [5], lower length-for-age Z (LAZ) scores [6], three-fold higher incidences of stunting [7, 8], and higher incidences of microcephaly (head circumference-for-age Z scores) [5, 9]. While most studies have shown somatic growth delays to continue till about 2 years of life, the Powis et al study from Botswana had shown lower WAZ amongst HEU infants improved rapidly in the first 2 months of life and reached the expected average-for-age values by 6 months of age.

Similar to some of the findings listed above, especially Powis et al, our study in mice also shows that U-ART pups reach average body weight and other somatic developments before the time of weaning.

Another potentially interesting concurrence between our data and that from HEU studies is that it took longer for U-ART pups (particularly in female pups) to catch up in length to the controls, as compared to weight. This coincides with evidence of lower LAZ persisting at 6 months [8] and 2 years of age for HEU children [6].

Because the authors used ‘disrupt’ in the title, the results did not show a significant disruption of development, for example, somatic defect, what is the fact in the human cases? Development delayed or some defects were observed in the U-ART infants?

We agree with the reviewer that the phenotype we are reporting here is more of ‘delayed growth and delayed development’, rather than one of ‘permanent disruption or defect’. Therefore, we have now removed the word ‘disrupts’ from the title of our paper and replaced it with ‘delays growth and developmental milestones’.

2. Because the authors mentioned that the mortality was higher in the first year in human cases, did the authors try to count the viability of pups between control and U-ART groups?

We thank the reviewer for raising this question. We did record mortality of pups in each of the treatment arms on the day of birth (P0) and throughout the course of the experiments. Of the 42 pups born in the control group, 0 were found dead on P0 (0% mortality). Of the 66 pups born in the KVX group, 2 were found to be dead (3% mortality). Of the 78 pups born in the TRV group, 5 were found to be dead (6.4% mortality) on P0. No mortality was observed after P0. The difference in mortality between groups did not reach significance (chi-squared test, p=0.14). We have added these data to the Results section of the revised paper (line 195-202).

Mortality amongst HEUs has been shown to be higher in resource limited settings, especially in cases where confounding factors such poor socio-economic status, malnutrition and unhygienic living conditions exist. HEUs are known to have a weaker immune system and respond poorly to infectious diseases [10]. It is possible that we did not observe significantly higher mortality in U-ART pups because of the controlled and pathogen free laboratory conditions in which they were raised.

3. Since the development indicators cannot reflect too many differences in control and U-ART pups, did the authors try to infect with pathogens or bacterial stimulators (e.g LPS) to see if the U-ART groups were more susceptible to infections?

We thank the reviewer for suggesting this very interesting experiment. However, in this paper we have tried to showcase only the early postnatal growth and behavioral characteristics (reflex maturation) of U-ART pups. We tried to concentrate on the neurodevelopmental delays that ensue in-utero ART exposure, which could be indicators for more robust behavioral abnormalities, later in life. Infecting U-ART pups with pathogens or bacterial stimulators to monitor their immune responses, susceptibility to infections, mortality rates etc, would be a deviation from the objectives of this paper. Experiments along the lines suggested by the reviewer are some of the future directions of our project and are beyond the scope of the current paper.

4. If the authors extend the monitoring window after weaning and more examinations can be utilized in the experiment, such as behavior tests, is it possible to see more differences between control and U-ART groups?

To address this question, we extended our study and performed additional behavioral experiments on our animals in adulthood. We performed the open field test to investigate general activity, locomotion and anxiety-like behavior in U-ART animals at 2 months of age. As has been pointed out by the reviewer, we did see more differences between the control and U-ART animals at this age. These new data have been added to the revised manuscript – see Figure 6, Methods line 153-160, Results line 318-331, and Discussion line 453-465 of the revised manuscript.

Our results showed that exposure to ATV/r/TDF/FTC had an effect on exploration levels in the open field in female mice (Figure 6), a decline in total distance moved in the open filed and distance moved in the centre. While a decline in total distance moved in the entire arena does not signify anxiety-like behavior, it indicates a decline in locomotion / motivation for exploration overall. A significant decline in ambulatory time spent in the centre was also noted in ATV/r/ TDF/FTC exposed females. Resting or idle time was also found to be higher in females exposed to ATV/r/ABC/3TC. Similar to our results from the post-natal period, we observed a sex difference in the effects of U-ART once again in adulthood. In males, no significant differences were observed in any of the measures in either U-ART exposed arms, compared to controls. We have discussed possible reasons for observation of sex differences in effects of U-ART under our revised Discussion.

5. The author mentioned that the mtDNA is affected because of ART treatment, is it possible to do more investigation in mtDNA in U-ART pups?

The effect of ART on mtDNA is well investigated and has been reviewed extensively [11]. It is possible to carry out several experiments to check for the effects of ART on mtDNA in U-ART pups. mtDNA integrity and mtDNA transcript levels can be checked for in mitochondrial lysates obtained from control versus U-ART mice tissue. However, such experiments would require careful and purposeful planning and collection of tissue in a systematic way. Unfortunately, this is not possible with our current experimental setup. We thank the reviewer for raising this question and it certainly provides impetus for future investigations.

Although the novelty of this manuscript is quite unique, the data here seems to be descriptive and preliminary.

We agree with the reviewer that our study is descriptive. However, our experiments include a sufficient number of animals, we have examined a large number of developmental milestones and somatic characteristics, and we have performed analyses based on pup sex. We have now, following the reviewer’s excellent suggestion, also expanded to include a behavioural test in adulthood. While we agree that our data are not mechanistic but rather descriptive, we respectfully disagree that they are preliminary.

References:

1. Król E, Murphy M, Speakman JR. Limits to sustained energy intake. X. Effects of fur removal on reproductive performance in laboratory mice. J Exp Biol. 2007;210(Pt 23):4233-4243. doi:10.1242/jeb.009779

2. Spangenberg E, Wallenbeck A, Eklöf AC, Carlstedt-Duke J, Tjäder S. Housing breeding mice in three different IVC systems: maternal performance and pup development. Lab Anim. 2014;48(3):193-206. doi:10.1177/0023677214531569

3. Wedderburn CJ, Evans C, Yeung S, Gibb DM, Donald KA, Prendergast AJ. Growth and Neurodevelopment of HIV-Exposed Uninfected Children: a Conceptual Framework. Curr HIV/AIDS Rep. 2019;16(6):501-513. doi:10.1007/s11904-019-00459-0

4. Dara JS, Hanna DB, Anastos K, Wright R, Herold BC. Low Birth Weight in Human Immunodeficiency Virus-Exposed Uninfected Infants in Bronx, New York. J Pediatric Infect Dis Soc. 2018;7(2):e24-e29. doi:10.1093/jpids/pix111

5. Evans C, Chasekwa B, Ntozini R, Majo FD, Mutasa K, Tavengwa N, et al. Surviving and thriving? Outcomes of HIV-exposed children in rural Zimbabwe. Conference on Retroviruses and Opportunistic Infections (CROI); 4th–7th March; Seattle (WA)2019

6. le Roux SM, Abrams EJ, Donald KA, Brittain K, Phillips TK, Nguyen KK, et al. Growth trajectories of breastfed HIV-exposed uninfected and HIV-unexposed children under conditions of universal maternal antiretroviral therapy: a prospective study. Lancet Child Adolesc Health. 2019;3(4):234–44.

7. Sudfeld CR, Lei Q, Chinyanga Y, et al. Linear Growth Faltering Among HIV-Exposed Uninfected Children. J Acquir Immune Defic Syndr. 2016;73(2):182-189. doi:10.1097/QAI.0000000000001034

8. Powis KM, Smeaton L, Ogwu A, et al. Effects of in utero antiretroviral exposure on longitudinal growth of HIV-exposed uninfected infants in Botswana. J Acquir Immune Defic Syndr. 2011;56:131–8.

9. Spaulding AB, Yu Q, Civitello L, et al. Neurologic Outcomes in HIV-Exposed/Uninfected Infants Exposed to Antiretroviral Drugs During Pregnancy in Latin America and the Caribbean. AIDS Res Hum Retroviruses. 2016;32(4):349-356. doi:10.1089/AID.2015.0254

10. Afran L, Garcia Knight M, Nduati E, Urban BC, Heyderman RS, Rowland-Jones SL. HIV-exposed uninfected children: a growing population with a vulnerable immune system. Clin Exp Immunol. 2014;176(1):11‐22. doi:10.1111/cei.12251

11. Pinti M, Salomoni P, Cossarizza A. Anti-HIV drugs and the mitochondria. Biochim Biophys Acta. 2006;1757(5-6):700-707. doi:10.1016/j.bbabio.2006.05.001

Decision Letter 1

Jean-Léon Thomas

4 Nov 2020

In utero exposure to protease inhibitor-based antiretroviral regimens delays growth and developmental milestones in mice

PONE-D-20-20335R1

Dear Dr. Serghides,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Jean-Léon Thomas

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The authors have responded well to each of the Reviewers' comments and improved the manuscript accordingly. There are no further comments from this Reviewer.

Reviewer #2: The authors answered all the comment point to point and also did more experiments to strengthen the data in the manuscript.

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If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

Acceptance letter

Jean-Léon Thomas

10 Nov 2020

PONE-D-20-20335R1

In utero exposure to protease inhibitor-based antiretroviral regimens delays growth and developmental milestones in mice

Dear Dr. Serghides:

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    S1 Fig. Example of a data sheet for recording observations for the assessments of developmental milestones.

    The shaded boxes mark the tests that were performed on each day. Tests were done in a sequence that was age appropriate for mice pups.

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    S1 Data. Complete raw data set.

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