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The Journal of Infectious Diseases logoLink to The Journal of Infectious Diseases
. 2025 Sep 24;233(2):247–256. doi: 10.1093/infdis/jiaf461

Fostemsavir Decreases the Levels of Anti-gp120 CD4-Induced Antibodies in Heavily Treatment-Experienced People With HIV

Mehdi Benlarbi 1,2,#, Jonathan Richard 3,4,#, Tommaso Clemente 5, Catherine Bourassa 6, William D Tolbert 7, Manyu Prakash 8, Monika Chandravanshi 9, Andrew Clark 10, Marzena Pazgier 11, Madeleine Durand 12,13, Antonella Castagna 14,15,✉,3, Andrés Finzi 16,17,✉,3
PMCID: PMC13017758  PMID: 40990223

Abstract

Background

Heavily treatment-experienced (HTE) people with HIV (PWH) have limited antiretroviral therapy (ART) treatment options, putting them at greater risk of unfavorable human immunodeficiency virus 1 (HIV-1) disease progression. Fostemsavir (BMS-663068) efficiently suppressed viremia and increased CD4 count when combined with other antiretrovirals in HTE PWH. Its active metabolite, temsavir (BMS-626529, GSK2616713), binds a conserved pocket within the envelope glycoprotein (Env) CD4 binding site and prevents CD4-induced conformational changes. Temsavir effect on Env conformation profoundly alters its glycosylation and cleavage, thereby modifying its antigenicity and reducing gp120 shedding. Here we evaluated if fostemsavir treatment in PWH modulated the levels of nonneutralizing gp120 CD4-induced (CD4i) antibodies (Abs) associated with CD4 depletion in vitro and in PWH.

Methods

We measured the levels of anti-gp120 CD4i Abs in plasma samples taken before and after fostemsavir treatment in HTE participants from the BRIGHTE trial and the PRESTIGIO registry and compared them to those of a control ART-treated group from the SAILING trial.

Results

We observed a significant decline of anti-gp120 CD4i Abs in the 2 fostemsavir-treated HTE groups, but not in the control group. Moreover, this effect was unique to anti-gp120 CD4i Abs, as no significant changes were observed in the levels of antibodies targeting Gag. Functionally, this decline in CD4i Abs was associated with a reduced capacity of plasma to recognize and eliminate uninfected primary CD4+ T cells coated with soluble gp120.

Conclusions

Altogether, fostemsavir may provide additional immune benefits to PWH, beyond blocking viral entry, by reducing anti-gp120 CD4i Abs levels.

Clinical Trials Registration

NCT04098315, NCT01231516, and NCT02362503.

Keywords: HIV-1, heavily treatment-experienced, multidrug resistance, fostemsavir, CD4 count, soluble gp120, CD4-induced antibodies, ADCC, bystander cells

Anti-gp120 CD4-induced antibodies are associated with CD4 depletion in vitro and in heavily treatment-experienced people with HIV. Fostemsavir treatment reduces the levels of these antibodies in these individuals.

Graphical Abstract

Graphical Abstract.

Graphical Abstract

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(See the Editorial Commentary by Kogilwaimath and Utay on pages 223–6.)

Combinatorial antiretroviral therapy (ART) leads to durable suppression of human immunodeficiency virus 1 (HIV-1) replication in people with HIV (PWH) [1]. With antiretroviral therapy, HIV-associated mortality and morbidity have steadily decreased, improving life expectancy for PWH [2, 3]. While the development of less toxic and more potent ART eased the management of HIV infection, some PWH do not achieve viral suppression with ART [4]. This may be due to multiclass resistance, intolerance, or drug-drug interactions, putting them at greater risk of unfavorable HIV-1 disease progression [5, 6].

In 2020, fostemsavir (FTR, BMS-663068, GSK3684934, Rukobia) was approved for heavily treatment-experienced (HTE) PWH [7]. Fostemsavir is the first and only Food and Drug Administration-approved HIV-1 envelope glycoprotein (Env)-directed attachment inhibitor [8]. It efficiently suppresses viremia and increases CD4 count when used in PWH failing their current ART regimen [9, 10]. Its active metabolite temsavir (TMR, BMS-626529, GSK2616713), binds to a conserved pocket under the Env β20-β21 loop and within the Phe43 cavity that partially overlaps the CD4 binding site [11, 12]. This molecule prevents Env-CD4 interaction, stabilizes Env in the “closed” state 1 conformation, and blocks CD4-induced conformational changes [13, 14]. Notably, TMR's effect on Env conformation was shown to profoundly alter Env glycosylation and processing at physiological concentration, thereby impacting its overall antigenicity [15, 16]. Furthermore, TMR inhibits the immunomodulatory activities of the soluble form of the Env gp120 subunit (sgp120) by blocking the sgp120-CD4 interaction, reducing gp120 shedding, and modifying sgp120 antigenicity [17].

It has been observed that sgp120 released from productively infected cells sensitizes uninfected bystander CD4+ T cells to Antibody-Dependent Cellular Cytotoxicity (ADCC) responses mediated by nonneutralizing antibodies (nnAbs) present in the plasma of PWH [17–19]. These CD4-induced (CD4i) nnAbs do not recognize the unliganded “closed” Env trimer; however, they can bind to conserved occluded epitopes that are exposed upon gp120 shedding [20, 21]. Binding of sgp120 to CD4 further exposes these epitopes, rendering uninfected bystander CD4+ T cells a prime target for nnAbs-mediated killing via ADCC responses [17–19 , 22]. We recently observed that a specific family of nnAbs, the anti-cluster A Abs, were associated with a decline in CD4 counts in ART-treated PWH [23]. Moreover, sgp120 can be detected in the plasma of PWH with undetectable viral loads and is associated with inflammation and immune dysfunction [24, 25].

Interestingly, beyond suppressing viral replication, long-lasting immune benefits such as a marked reduction in inflammatory biomarkers and CD4 count increase were observed upon fostemsavir treatment [26–28]. In this study, we evaluated whether fostemsavir treatment, through its effect on Env, could modulate the levels of anti-gp120 CD4i nnAbs in PWH. We measured the levels of these antibodies in plasma samples from the BRIGHTE trial [9] and the PRESTIGIO registry [29] before and after fostemsavir treatment. We compared these responses to that of a control ART-treated group from the SAILING trial [30]. We also measured the levels of antibodies against another viral protein, Gag, that is not targeted by fostemsavir. Finally, we evaluated if modulation of nnAbs levels could have an impact on the recognition and ADCC-mediated killing of sgp120-coated bystander primary CD4+ T cells.

METHODS

Ethics Statement

Written informed consent was obtained from all study participants. Research adhered to the ethical guidelines of Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM) and was reviewed and approved by the CRCHUM institutional review board (ethics committee, approval number MP-02–2024-11734). The PRESTIGIO registry was approved on 14 December 2017 (ClinicalTrials.gov, NCT04098315), and research adhered to the standards indicated by the Declaration of Helsinki. SAILING (ClinicalTrials.gov, NCT01231516) and BRIGHTE (ClinicalTrials.gov, NCT02362503) trials were performed in accordance with the Declaration of Helsinki.

Cell Lines and Primary Cells

FreeStyle 293F cells (Thermo Fisher Scientific) were grown in FreeStyle 293F medium (Thermo Fisher Scientific) to a density of 1 × 106 cells/mL at 37°C with 8% CO2 with regular agitation (150 rpm). Primary human peripheral blood mononuclear cells (PBMCs) and CD4+ T cells were isolated, activated, and cultured as previously described [20]. Briefly, PBMCs from an uninfected control, 1 male (47 years of age), was obtained by leukapheresis. Ficoll-Paque density gradient isolations were cryopreserved in liquid nitrogen until further use. CD4+ T lymphocytes were purified from resting PBMCs by negative selection using immunomagnetic beads per the manufacturer's instructions (StemCell Technologies). These cells were then activated with phytohemagglutinin-L (10 mg/mL) for 48 hours and maintained in Roswell Park Memorial Institute (RPMI) 1640 complete medium supplemented with recombinant interleukin 2 (rIL-2; 100 U/mL).

Antibodies and PWH Plasma

Goat anti-human IgG (H + L) antibodies precoupled to Alexa Fluor 647 (Invitrogen) was used as secondary Abs in flow cytometry experiments. For enzyme-linked immunosorbent assays (ELISAs), goat anti-human or anti-rabbit IgG precoupled to horseradish peroxidase (HRP; Invitrogen) was used. EDTA plasma from BRIGHTE trial, PRESTIGIO registry, and SAILING trial were collected, heat inactivated, and stored at −80°C until used for flow cytometry and ELISA. Inclusion criteria for the BRIGHTE study participants included HIV-1 subtype B infection, HIV sensitive to fostemsavir at baseline, low baseline CD4 counts (20–200 cells/mL) with a CD4 count recovery over time reaching above 400 cells/mL at last visit (> 48 weeks), and time to first instance of virologic suppression ≥ 48 weeks. Inclusion criteria for the SAILING study participants included use of enfuvirtide in prior ART, minimum of 4 to 5 class resistance at the time of screening, a low baseline CD4 count (20–200 cells/mL) with a CD4 count recovery over time reaching above 400 cells/mL at last visit (> 48 weeks), and time to first instance of virologic suppression ≥ 48 weeks. Based on these criteria we obtained matched plasma samples from day 1 and weeks 8 and 12 to measure the levels of antibodies. Inclusion criteria for the PRESTIGIO registry participants were the availability of matched samples before and after fostemsavir treatment.

Protein Production and Purification

Production and purification of monomeric soluble HIV-1YU2 gp120 and gp120 ΔV1V2V3V5 (termed gp120core) has been described elsewhere [25, 31, 32]. FreeStyle 293F cells were transfected with the gp120 expressor using ExpiFectamine 293 transfection reagent, as directed by the manufacturer (Thermo Fisher Scientific). One week later, cells were pelleted, and supernatants were filtered using a 0.22-μm pore size filter (Thermo Fisher Scientific). Recombinant gp120 was purified by nickel affinity columns, as directed by the manufacturer (Thermo Fisher Scientific). Monomeric gp120 was subsequently purified by fast protein liquid chromatography (FPLC), as previously reported [31] by using an ÄKTAprime Plus FPLC with a HiLoad 16/60 Superdex 200 PG (GE Healthcare). Purified gp120 was dialyzed against phosphate-buffered saline (PBS) and stored in aliquots at −80°C until further use. To assess purity, recombinant proteins were loaded on nonreducing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) gels and stained with Coomassie blue.

Enzyme-Linked Immunosorbent Assay

The ELISAs used in this study have been described elsewhere [25, 32]. For measurement of anti-gp120 CD4i antibodies and anti-cluster A antibodies, wells were coated with gp120core [33] or stabilized gp120 inner domain ID2 [34], respectively, at a concentration of 0.1 µg/mL in PBS. As a negative control, wells were coated in parallel with BSA (0.1 µg/mL in PBS). After blocking, the cluster A-specific A32 mAb (1 µg/mL) or diluted plasma 1:1000 from PWH or uninfected individuals was added to the well and detection of plasma antibodies was performed using HRP-conjugated goat anti-human IgG (Invitrogen) at a dilution of 1:3000. HRP enzyme activity was determined after the addition of a 1:1 mix of Western Lightning oxidizing and luminol reagents (Perkin Elmer Life Sciences). Light emission was measured with an LB942 Tri-Star luminometer (Berthold Technologies). Signal obtained with BSA was subtracted for each plasma and values were then normalized to the signal obtained with A32 mAb present in each plate. The positivity threshold was established using the following formula: mean of 10 plasmas from uninfected donors + (3 standard deviation of the mean of the 10 plasmas from uninfected donors).

For measurement of anti-p24 antibodies, wells were coated with recombinant HXB2 p24 protein (0.1 µg/mL; NIH AIDS reagent program No. ARP-13137), in parallel with BSA (0.1 µg/mL). After blocking, rabbit anti-HIV p24 antiserum (1:5000; NIH AIDS reagent program No. ARP-4250) or diluted plasma (1:1000) from PWH or uninfected individuals was added to the well. Detection of plasma antibodies was performed using HRP-conjugated goat-anti-human IgG or HRP-conjugated goat-anti rabbit IgG (1:3000; Invitrogen). The signal was measured as described above and signal obtained with BSA was subtracted for each plasma and values were then normalized to the signal obtained with rabbit anti-HIV p24 antiserum present in each plate. The positivity threshold was established using the following formula: mean of 10 plasmas from uninfected donors + (3 standard deviation of the mean of the 10 plasmas from uninfected donors).

Coculture Assay With sgp120-Coated CD4+ T Cells

Briefly, 100 ng/mL of monomeric recombinant HIVYU2 gp120 was added to activated primary CD4+ T cells resuspended at 1 × 106 cells/mL for 30 minutes at 37°C, 5% CO2. Following 2 washes with complete RPMI-1640 media, these sgp120-coated cells were stained with eFluor450 dye (1:1000 dilution; Invitrogen) for 15 minutes at room temperature. In parallel, autologous uncoated CD4+ T cells were stained with carboxyfluorescein succinimidyl ester (CFSE) dye (1:1000 dilution; Invitrogen) for 15 minutes at room temperature and washed twice with complete RPMI-1640 media. Uncoated cells (CFSE+eFluor450−) were mixed with coated cells (CFSE−eFluor450+) at a 1:1 ratio. These target cells were subsequently stained with PWH plasma (1:4000 dilution) followed with appropriate secondary Abs. To measure ADCC responses, autologous PBMCs effectors cells were stained with the eFluor670 cell marker (eBioscience). PBMCs were added to target cells (in the presence of PWH plasma at a 1:4000 dilution) at an effector to target ratio of 10:1 in 96-well V-bottom plates (Corning) and subsequently centrifuged for 1 minute at 300g. The cells were incubated at 37°C, 5% CO2 for 5 to 6 hours before being fixed with a PBS-formaldehyde solution (2% formaldehyde final concentration). The percentage of ADCC responses directed against the sgp120 coated cell population (eFluor450+CFSE−) was calculated with the following formula: ((percentage of eFluor450+CFSE− cells in the target + PBMCs condition) − (percentage of eFluor450+CFSE− cells in the target + PBMCs + plasma condition))/(percentage of eFluor450+CFSE− cells in the target alone condition). Samples were acquired on an LSRII cytometer (BD Biosciences), and data analysis was performed using FlowJo version 10.8.1 (Tree Star).

Statistical Analyses

Every variable was tested for statistical normality, and this information was used to apply the appropriate (parametric or nonparametric) statistical test and descriptive statistics. For all analyses, P values < .05 were considered significant. Analyses were done using GraphPad Prism version 10.4.0.

RESULTS

Participants

To evaluate the impact of fostemsavir on nonneutralizing anti-gp120 CD4i levels, we used plasma samples from 3 independent cohorts of HTE PWH taken before and after ART regimen change (Table 1). As a control ART-treated group, we included 7 participants from the SAILING trial [30]. In this noninferiority study evaluating integrase-strand transfer inhibitors (INSTIs) efficacy, HTE participants were randomly assigned to once-daily dolutegravir or twice-daily raltegravir. For the fostemsavir-treated groups, we included 12 participants with 2- or 3-drug-class-resistant HIV from the BRIGHTE trial [9]. In this trial evaluating the efficacy of fostemsavir in HTE, participants were assigned to add 600 mg fostemsavir twice daily to their current failing regimen. For both trials, we obtained paired samples taken on day 1 (before ART regimen change) and at week 8 or 12 after treatment. Lastly, we included 14 HTE participants with 4-drug-class-resistant HIV from the PRESTIGIO registry, who received the recommended fostemsavir dose together with an optimized background therapy in a real-world setting [29].

Table 1.

Characteristics of Participants Evaluated in This Study

Characteristic SAILING
Control (n = 7)		 BRIGHTE
FTR (n = 12)		 PRESTIGIO
FTR (n = 14)
Day 1 Week 8–12 P valuea Day 1 Week 8–12 P valuea Pre-FTR Follow-up P valuea
Age, y, mean (IQR) NA NA NA 48.67 (21–66) NA 47.6 (18–61) 52.2 (21–71) NA
Male sex, n (%) NA NA NA 11 (91.6) NA 12 (85.7) NA
CD4 count, cells/mL, mean (SD) 90.6 (70.2) 199 (57.2) .0004 66.8 (76.5) 126.3 (87.7) .0057 612 (373.2) 563.3 (393) .4796
Viral load, copies/mL, mean (SD) 497 850 (484 093) 91.25 (35.4) .0346 104 042 (123 535) 2432 (5133) .0005 23 757 (45 876) 20 660 (76 992) .1953
Undetectable viremia <50 copies/mL, n (%) 0 (0) 1 (14.3) > .9999 0 (0) 0 (0) > .9999 6 (42.9) 10 (71.4) .2519
FTR duration, wk, mean (IQR) NA NA NA NA 9 (8–12) NA NA 108.8 (32.9–149.4) NA
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Abbreviations: FTR, fostemsavir; IQR, interquartile range; n, number of participants; NA, not applicable.

a P value obtained by Fisher exact test for categorial variables and a paired t test or Wilcoxon matched-pairs test for continuous variables. P values are comparison between matched visits.

The demographics and clinical parameters at baseline and after ART regimen change are summarized in Table 1. For both SAILING and BRIGHTE participants, a significant decrease in viral load and an increase in CD4 counts were observed. At the time points analyzed, most participants did not reach undetectable viremia. For PRESTIGIO participants, no significant differences were observed after fostemsavir treatment, albeit more participants reached undetectable viremia. Participants from the PRESTIGIO registry had higher baseline CD4 counts and lower viral loads compared to participants from both SAILING and BRIGHTE trials. Owing to its real-world setting design, the duration of fostemsavir treatment among PRESTIGIO participants was quite heterogenous compared to the SAILING and BRIGHTE participants, with an interquartile range of 32.9–149.4 weeks and a minimum-maximum of 1.7–374.3 weeks (Table 1). They also had an overall longer duration of fostemsavir treatment.

Levels of Anti-gp120 CD4i Abs After Fostemsavir Treatment in Heavily Treatment-Experienced PWH

In vitro, TMR impact on Env conformation leads to modulation of its glycosylation and cleavage, thereby modifying its antigenicity and reducing gp120 shedding [15–17]. We first evaluated the impact of fostemsavir treatment of PWH on anti-gp120 CD4i Abs levels. To do this, we measured the level of antibodies targeting the HIV-1 Env gp120core. This CD4-bound stabilized gp120 readily exposes highly conserved CD4i epitopes that are normally occluded in the native Env trimer [33]. Strikingly, we observed a significant decrease in anti-gp120 CD4i Abs levels in both groups receiving fostemsavir (BRIGHTE and PRESTIGIO), but not in the control ART-treated group (SAILING) (Figure 1A).

Figure 1.

Figure 1.

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Fostemsavir treatment decreases the levels of anti-gp120 CD4-induced nonneutralizing Abs in heavily treatment-experienced people with HIV. Paired plasma samples taken before or after treatment with fostemsavir (BRIGHTE, PRESTIGIO) or with an INSTI (SAILING) were tested by ELISA for measurement of (A) anti-gp120 CD4-induced antibodies, (B) anti-cluster A antibodies, and (C) anti-p24 antibodies. The dotted line represents the seropositivity threshold calculated using plasma from uninfected controls. Statistical significance before and after treatment was tested using a paired t test or a Wilcoxon matched-pairs rank test, and P values are shown. Abbreviations: Abs, antibodies; ELISA, enzyme-linked immunosorbent assay; FTR, fostemsavir; INSTI, integrase strand transfer inhibitor; RLU, relative light unit.

We also evaluated the levels of nonneutralizing anti-cluster A antibodies using an engineered stabilized gp120 inner domain 2 protein (ID2), which exposes only the cluster A region [34]. We recently reported a negative association between the plasma levels of this family of ADCC-mediating nnAbs and CD4 counts in ART-treated PWH [23]. We observed a significant decline in anti-cluster A Abs for PRESTIGIO participants, but not for the other 2 groups (Figure 1B). To rule out the possibility that this decrease in anti-gp120 CD4i Abs is due to a decrease in viral load, we measured antibodies against another viral protein not targeted by fostemsavir (Gag p24 antigen). We did not observe any significant differences in anti-p24 Abs after fostemsavir treatment (Figure 1C).

Recognition and ADCC Responses Against sgp120-Coated Bystander Cells After Fostemsavir Treatment in Heavily Treatment-Experienced PWH

It has been reported that anti-gp120 CD4i Abs commonly detected in the plasma of PWH can mediate ADCC responses against uninfected bystander CD4+ T cells coated with sgp120 [17, 18, 23]. We thus evaluated whether the decrease in anti-gp120 CD4i Abs levels observed after fostemsavir treatment in PWH could reduce the plasma's capacity to recognize and eliminate sgp120-coated uninfected bystander CD4+ T cells via ADCC. Briefly, using a modified flow-cytometry–based coculture assay [17, 23], primary CD4+ T cells isolated from an uninfected control were coated with recombinant monomeric sgp120, stained with an eFluor450 dye and then cocultured with autologous uncoated cells stained with a CFSE dye (Supplementary Figure 1A). Plasma binding to the sgp120-coated eFluor450+CFSE− cells was evaluated using flow cytometry (Supplementary Figure 1B and 1C). ADCC-mediated elimination of the sgp120-coated eFluor450+CFSE− cells was also measured after incubation with autologous PBMCs.

Concomitant with a decrease in anti-gp120 CD4i Abs by ELISA, we observed that fostemsavir treatment in PWH reduced their plasma's capacity to recognize primary CD4+ T cells coated with sgp120 (Figure 2A). We did not observe this diminution in the control group. Functionally, this decrease in Abs was also associated with a reduced capacity to eliminate sgp120-coated uninfected bystander cells via ADCC (Figure 2B). These results suggest that fostemsavir's effect on Env conformation reduces the levels of nonneutralizing antibodies in plasma from PWH, thereby decreasing their capacity to recognize and eliminate sgp120-coated uninfected bystander CD4+ T cells via ADCC.

Figure 2.

Figure 2.

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Fostemsavir treatment decreases the recognition and ADCC-mediated killing of sgp120-coated primary CD4+ T cells by plasma from heavily treatment-experienced people with HIV. A, Recognition and (B) ADCC-mediated elimination of sgp120-coated primary CD4+ T cells by paired plasma samples taken before or after treatment with fostemsavir (BRIGHTE, PRESTIGIO) or with an INSTI (SAILING). A and B, Activated primary CD4+ T cells were coated with sgp120 and then stained with the eFluor450 dye. These coated cells were then cocultured with uncoated (eFluor450−CFSE+ cells) at a 1:1 ratio. Target cells were subsequently stained with paired plasma from the different cohorts and either analyzed by flow cytometry or used in the ADCC assay. The dotted line represents the seropositivity threshold calculated using plasma from uninfected controls. Statistical significance before and after treatment was tested using a paired t test or a Wilcoxon matched-pairs rank test, and P values are shown. Abbreviations: ADCC, antibody-dependent cellular cytotoxicity; CFSE, carboxyfluorescein succinimidyl ester; FTR, fostemsavir; INSTI, integrase strand transfer inhibitor; MFI, mean fluorescence intensity.

CD4 Counts Recovery After Fostemsavir Treatment in Heavily Treatment-Experienced PWH Is Associated With a Decline in Anti-gp120 CD4i Abs

We recently observed that nonneutralizing anti-gp120 cluster A Abs were associated with a decline in CD4 counts in ART-treated PWH [23]. We wondered whether the decline in anti-gp120 CD4i Abs observed upon fostemsavir treatment in PWH was associated with the CD4 counts. We performed univariate analysis between the fold-change in anti-gp120 CD4i nnAbs with the fold-change in CD4 counts before and after fostemsavir treatment. Interestingly, we observed that a decrease in anti-gp120 CD4i Abs was significantly associated with an increase in CD4 count in both groups receiving fostemsavir, but not in the SAILING control group (Figure 3A). Concomitant with a decrease in anti-cluster A Abs in the PRESTIGIO cohort, we observed a significant association between the decline in anti-cluster A Abs and the restoration in CD4 counts after fostemsavir treatment (Figure 3B). These effects were specific to anti-gp120 CD4i Abs, as we did not observe any significant associations with the fold change in anti-p24 antibodies (Figure 3C). These results suggest that CD4 restoration following fostemsavir (but not INSTI) treatment in HTE PWH may be linked to a decrease in ADCC-mediating anti-gp120 CD4i nnAbs.

Figure 3.

Figure 3.

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Decline in anti-gp120 CD4-induced Abs correlates with CD4 recovery after fostemsavir treatment in heavily treatment-experienced people with HIV. Correlations between the fold change of CD4+ T-cell counts and antibody levels before and after treatment with fostemsavir (BRIGHTE, PRESTIGIO) or with an INSTI (SAILING). Correlations are shown for (A) anti-gp120 CD4-induced antibodies, (B) anti-cluster A antibodies, and (C) anti-p24 antibodies. Fold changes represent the value after treatment divided by the respective value before treatment. The bold line represents a simple linear regression with the 95% confidence bands shaded in grey. Correlation coefficients and P values were calculated using Spearman or Pearson rank correlations. Abbreviations: Abs, antibodies; CD4i, CD4 induced; FTR, fostemsavir; INSTI, integrase strand transfer inhibitor.

DISCUSSION

Despite the development of potent antiretroviral options, and a comparative life expectancy, there remains a 15-year gap in comorbidity-free years with and without HIV infection [2]. Bolstering the immune landscape and minimizing the chronic impact of inflammation could be key to closing this gap [35, 36]. Fostemsavir is the first in class small molecule gp120-inhibitor approved for HTE PWH [7]. Clinical benefits were observed in HTE PWH upon fostemsavir treatment, notably by decreasing viremia and increasing CD4 counts [27]. It was previously observed that the unique mechanism of action of TMR, the active metabolite of fostemsavir, could significantly alter the Env maturation's process, thereby modifying its antigenicity and reducing gp120 shedding [13, 16, 17]. In this study, we evaluated in 2 independent cohorts whether fostemsavir treatment, through its effect on Env conformation, could modulate the levels of nonneutralizing anti-gp120 CD4i Abs associated with CD4 depletion in vitro and in vivo [18, 23].

We observed that plasma samples from participants receiving fostemsavir both in the BRIGHTE trial and in the real-life setting of the PRESTIGIO registry had a significant decline in anti-gp120 CD4i Abs. This was specific to anti-gp120 CD4i Abs, as we did not see this decrease with anti-p24 Abs nor with control ART-treated HTE participants from the SAILING trial, despite a significant reduction in viremia. It is well established that nonneutralizing anti-gp120 Abs are readily and preferentially elicited upon HIV infection [37–39 ]. Despite high levels of these Abs, they are not able to control HIV infection because they do not bind the unliganded Env trimer present at the surface of viral particles or productively infected cells [40, 41]. Elicitation of these nnAbs may be explained by the presence of sgp120 released from infected cells. We recently reported a positive association between the levels of anti-gp120 cluster A Abs with the viral reservoir in aviremic participants [25]. Whether fostemsavir treatment could affect the levels of anti-gp120 CD4i Abs by modulating the viral reservoir warrants further studies. Moreover, monomeric sgp120 has been shown to preferentially elicit nnAbs in vivo [32, 42–44]. Interestingly, it was observed that administration of Env trimers complexed with TMR could reduce the elicitation of nnAbs and favor the generation of broadly neutralizing Abs in animal models [45]. Thus, fostemsavir may reduce the levels of anti-gp120 CD4i by significantly altering sgp120 antigenicity and/or by reducing sgp120 levels in PWH, preventing the induction and persistence of anti-gp120 B cells responses.

While these nnAbs do not neutralize viral particles, they are able to recognize shed gp120 bound to the CD4 on uninfected bystander CD4+ T cells, leading to cell death via ADCC responses [18, 19, 46]. We recently reported that nonneutralizing anti-cluster A Abs were negatively associated with the CD4 counts in ART-treated PWH [23, 25]. Here we observed that by reducing anti-gp120 CD4i Abs levels, fostemsavir treatment reduced the capacity of plasma to recognize and mediate ADCC responses against sgp120-coated primary CD4+ T cells. Moreover, we observed that the decline in anti-gp120 CD4i Abs and anti-cluster A Abs following fostemsavir treatment was associated with CD4 counts recovery. It is well established that a sustained low CD4 count in virally suppressed PWH is associated with the development of comorbidities [47]. Whether fostemsavir could have a similar impact on anti-gp120 CD4i Abs, anti-cluster A Abs, and CD4 counts in long-term virally suppressed PWH needs to be addressed.

Several reports have observed long-lasting immunological benefits associated with the use of fostemsavir in HTE PWH within the BRIGHTE trial [26–28]. In one of these studies, fostemsavir treatment reduced the levels of inflammatory markers such as soluble CD14, soluble CD163, and D-dimer [28]. Interestingly, in the OPERA cohort, it was observed that fostemsavir treatment in virally suppressed PWH with low CD4 counts led to an improvement in the CD4 counts [48]. Whether this is related to the effect of TMR on Env conformation and/or by blocking sgp120 immunomodulatory properties remains to be determined.

Altogether, our study highlights a novel role for fostemsavir beyond suppressing viral replication in PWH. Because nearly all PWH have nonneutralizing anti-gp120 CD4i Abs, which are associated with CD4 depletion [23, 39], fostemsavir treatment could provide immunological benefits even in non-HTE PWH.

Supplementary Material

jiaf461_Supplementary_Data
jiaf461_supplementary_data.jpeg (4.6MB, jpeg)

Notes

 Acknowledgment. The authors thank the Centre de Recherche du CHUM BSL3 and Flow Cytometry platforms.

Author contributions. M. B., J. R., and A. F. contributed conceptualization, methodology, visualization, and wrote the original draft. M. B., J. R., and C. B. performed investigations. M. B., J. R., T. C., C. B., W. D. T., M. Pr., A. Cl., M. Pa., M. D., A. Ca., and A. F. contributed resources. M. B. and J. R. performed formal analysis. M. B., J. R., M. Pa., M. D., A. Ca., and A. F. contributed supervision. M. D. and A. F. contributed funding acquisition. M. B., J. R., T. C., C. B., W. D. T., M. Pr., A. Cl., M. Pa., M. D., A. C., and A. F. reviewed and edited the manuscript.

Disclaimer. The views expressed in this manuscript are those of the authors and do not reflect the official policy or position of the Uniformed Services University, the US Army, the Department of Defense, or the US government. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Data availability. All relevant data files of this study will be made available to qualified researchers upon approval of a reasonable request to the lead contact author Andrés Finzi (andres.finzi@umontreal.ca).

Financial support. This work was supported by the Canadian Institutes of Health Research (grant number 197728 Team Grant); the Canada Foundation for Innovation (grant number 41027 to A. F.); the National Institutes of Health (grant numbers R01AI148379 and R01AI17653 to A. F., R01AI174908, R01AI150322, and R01AI186809 to A. F. and M. P., P01AI162242 to M. P., and UM1AI164562 ERASE to A. F.). The study was partially supported by ViiV to analyze the SAILING and BRIGHTE samples. M. D. received a clinician-researcher salary award from Fonds de Recherche du Québec-Santé. M. B. is the recipient of a doctoral Canadian Institutes of Health Research fellowship (grant number FBD-193357).

Contributor Information

Mehdi Benlarbi, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Axe immunopathologie, Montréal, Quebec, Canada; Département de Microbiologie, Infectiologie, et Immunologie, Université de Montréal, Montréal, Quebec, Canada.

Jonathan Richard, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Axe immunopathologie, Montréal, Quebec, Canada; Département de Microbiologie, Infectiologie, et Immunologie, Université de Montréal, Montréal, Quebec, Canada.

Tommaso Clemente, Infectious Diseases, Istituto di Ricovero e Cura a Carattere Scientifico San Raffaele Scientific Institute, Milan, Italy.

Catherine Bourassa, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Axe immunopathologie, Montréal, Quebec, Canada.

William D Tolbert, Infectious Disease Division, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.

Manyu Prakash, ViiV Healthcare, London, United Kingdom.

Monika Chandravanshi, Infectious Disease Division, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.

Andrew Clark, ViiV Healthcare, London, United Kingdom.

Marzena Pazgier, Infectious Disease Division, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.

Madeleine Durand, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Axe immunopathologie, Montréal, Quebec, Canada; Department of Medicine, Faculty of Medicine, Centre Hospitalier de l’Université de Montréal, Montréal, Quebec, Canada.

Antonella Castagna, Infectious Diseases, Istituto di Ricovero e Cura a Carattere Scientifico San Raffaele Scientific Institute, Milan, Italy; Vita-Salute University, San Raffaele Scientific Institute, Milan, Italy.

Andrés Finzi, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Axe immunopathologie, Montréal, Quebec, Canada; Département de Microbiologie, Infectiologie, et Immunologie, Université de Montréal, Montréal, Quebec, Canada.

Supplementary Data

Supplementary materials are available at The Journal of Infectious Diseases online (http://jid.oxfordjournals.org/). Supplementary materials consist of data provided by the author that are published to benefit the reader. The posted materials are not copyedited. The contents of all supplementary data are the sole responsibility of the authors. Questions or messages regarding errors should be addressed to the author.

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