Altered Surrogate Markers of Inflammation in Perinatal HIV-Exposed Children with Caries

Abstract

Objective:

Dental caries is associated with immunologic response, yet its association with hematologic parameters and inflammatory markers is unclear. This study aimed to examine the relationship between some surrogate markers of inflammation and dental caries in the context of perinatal exposure to human immunodeficiency virus (HIV).

Methods:

This cross-sectional study involved 2 groups of children aged 4 to 11 y who were (1) HIV exposed but uninfected (HEU) and (2) HIV unexposed/uninfected (HUU) and recruited from HIV pediatric and child outpatient clinics, respectively, at a tertiary health facility in Nigeria. Medical records were reviewed, and trained dentists conducted oral and dental examinations. Five milliliters of EDTA blood was obtained and used for CD4 and CD8 and complete blood analysis, from which other inflammatory markers such as the neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), systemic inflammatory index (SII), CD4/CD8 ratio were calculated using referenced formulas.

Results:

In total, 245 (125 HEU and 120 HUU) children with a mean (standard deviation) age of 7 (2) y were included in this study. No differences in caries experience were observed in both groups of children (38 children [16%] were caries affected; 19 [16%] and 19 [15%] from the HEU and HUU groups, respectively). Examining the relationship between studied inflammatory markers and caries showed that leucocyte counts were slightly lower in caries-affected children compared with their caries-free counterparts (P = 0.05). Lower levels of neutrophils (P = 0.04) and higher levels of lymphocytes (P = 0.02) were associated with caries prevalence. Although not significant, NLR, PLR, and SII were lower in caries-affected children.

Conclusion:

Caries is associated with leucocytes and some of its subsets in both groups of children and independent of perinatal HIV exposure, highlighting the potential of evaluating inflammatory markers in caries prevention, treatment, and research.

Knowledge Transfer Statement:

This study provides evidence that a relationship exists between dental caries, HIV exposure, and inflammation using affordable methods and advocates the inclusion of these markers in caries care in resource-limited settings.

Introduction

Dental caries is a complex and chronic disease that contributes to the burden of oral diseases worldwide. Dental caries remains a global public health concern despite various interventional oral health policies and programs (Sofola et al. 2014). Dental caries is a common disease with a worldwide prevalence of 35% for all ages combined and has been reported to affect about half of preschool-aged children worldwide (Uribe et al. 2021). There are several thoughts on this prevalence between developed and developing countries as sociodemographic and socioeconomic factors have been implicated to affect the incidence of dental caries (Sofola et al. 2014; Kolay and Satish 2019). The prevalence of dental caries among school-aged children in Nigeria is unclear because of no recent national survey. However, available data on dental caries are from surveys conducted within specific towns and cities and place its prevalence between 13.9% and 17.4% (Sofola et al. 2014; Oyedele et al. 2019; Folayan et al. 2022). Dental caries occurs when the enamel and dentin undergo demineralization by organic acid produced by the activities of bacteria in dental plaque resulting from the anaerobic metabolism of sugars derived from diets (Bilbilova 2020). This anaerobic metabolism of sugars and fermentable carbohydrates alters the oral microbiota, leading to altered pH balance and a host inflammatory response. The distorted microbiota will often lead to a host inflammatory response to microbial challenges, which, if not attended to, may lead to other orodental diseases such as gingivitis, periodontitis, and caries (Gambhir et al. 2012; Goldberg et al. 2015). The innate immune response, which protects the dentin-pulp complex, can also lead to high inflammation and mobilization of soluble antimicrobial proteins and immune cells to the infection site (Gambhir et al. 2012; Gitalis et al. 2019).

Many studies have demonstrated the link between immunosuppression, particularly in human immunodeficiency virus (HIV), and some oral disorders such as dental caries with elevated inflammatory markers (Joosab et al. 2012; Rajonson et al. 2017; Coker et al. 2018). Significant changes in the composition and taxonomic abundance of bacterial communities may result from HIV infection and the ensuing loss of CD4 cells, which can upset the equilibrium between host immunity and the endogenous microbiota. The health of the oral tissue and the local immune system may be further affected by these changes in the microbiota, increasing sensitivity to harmful microorganisms and perhaps contributing to HIV-related oral illnesses (Goldberg et al. 2015). The effective use of antiretroviral therapy (ART) has given rise to an increasing population of children exposed perinatally to HIV, and these children born to mothers living with HIV are at risk of developing illnesses attributable to a weakened host immune system (Jumare et al. 2019). A novel study conducted by our research team showed that HIV infection affects the oral microbiome of affected children, with the effect of perinatal exposure (without infection) being transient, depending mainly on immune status (Coker et al. 2018; Coker et al. 2020). Our other previous studies have reported an increase in the incidence of dental caries among HIV-exposed uninfected (HEU) children than their unexposed uninfected counterparts (Coker et al. 2021; Akhigbe et al. 2022). Although the link between HIV perinatal exposure and caries in the context of inflammation is unknown, the involvement of white blood cells (WBCs) and their subsets in both conditions has been established; therefore, this is part of the reason for this study (Maganti 2020; Duguma et al. 2021).

In the host immune responses to caries, the role of neutrophils in the saliva is given due regard because they are the first cells that enter the gingival sulcus through the blood and hence the cells in the front line of defense (Gitalis et al. 2019). Therefore, to effectively mitigate oral bacterial infections such as caries, neutrophils must play their complete roles, including transendothelial migration, chemotaxis, opsonization, and phagocytosis, with the resultant release of enzymes such as matrix metalloproteinase, collagenase, and gelatinase (Fiorellin et al. 2011; Gitalis et al. 2019).

The vital role of neutrophils in caries underscores a high need for neutrophil activity as well as the activity of other systemic inflammatory markers to be monitored in patients with dental caries. However, a recent study that examined at the association between differential leucocyte count and dental caries revealed that there is a negative correlation between dental caries and the neutrophil count, and a positive correlation was observed between dental caries and eosinophil, monocyte, lymphocyte, and basophil counts (Maganti 2020). Also, the need to monitor the immune-inflammatory response in dental caries is reasonable, as recent evidence suggests a positive correlation between dental caries and periodontitis. Patients with dental caries, periodontitis, and odontogenic infections are at high risk of oral complications if not followed up, and these conditions may also lead to other systemic diseases (Dogruel et al. 2017; Maganti 2020).

Although there are several studies on the role of systemic immune-inflammatory markers in the development of odontogenic infection, as well as the influence of periodontitis on some of these inflammatory markers, there is a paucity of data on the role of these markers in dental caries (Dogruel et al. 2017; Acharya et al. 2019). Some markers of inflammation, such as the platelet-lymphocyte ratio (PLR), monocyte-lymphocyte ratio, and neutrophil-lymphocyte ratio (NLR), have been identified as potential markers of inflammation in various conditions such as cardiovascular conditions and cancer, including oral cavity cancer (Gunduz et al. 2015; Liu et al. 2015; Oylumlu et al. 2015). Although several studies have associated dental caries with anemia, malnutrition, weight loss, and poor quality of life, there are knowledge gaps on the relationship between dental caries and other hematologic parameters apart from hemoglobin (Sokal-Gutierrez et al. 2016; So et al. 2017). Also, cytokines and inflammatory factors from pulpitis and dental caries–related abscesses can suppress erythropoiesis, as they are released from damaged tissues (Tang et al. 2013). It is believed that this could also affect the production of other blood cells and their components. Therefore, the main objective of this study is to investigate the relationship between dental caries and some hematologic indices in the context of perinatal HIV exposure and also assess the level of some surrogate markers of inflammation in school-aged children living in sub-Saharan Africa with caries and perinatal HIV exposure.

Materials and Methods

Study Population and Setting

This cross-sectional study involved participants aged 4 to 11 y from pediatric medical care at the University of Benin Teaching Hospital, a tertiary referral hospital in Edo State, Southern Nigeria, known for its expertise in managing diverse disease conditions. Details of the cohort (DOMHaIN study) from which this subset was enrolled have been previously described (Coker et al. 2021; Akhigbe et al. 2022). Briefly, after enrollment, participants were examined for caries by calibrated dentists. Figure 1 summarizes participants’ recruitment and data collection procedures that occurred during the period between October 2018 and August 2019. Children infected with HIV and hepatitis B virus (HBV) were excluded from this study. A total of 245 children from the DOMHaIN study cohort who had all the parameters required for this study were enrolled into the study and grouped into categories of either HEU and HIV unexposed-uninfected (HUU). Demographics in this group did not significantly differ from those of the entire group.

Figure 1.

Flowchart of the study participant recruitment process. The figure shows the highlights of how participants for this study were recruited from the DOMHaIN study cohort (inclusion and exclusion criteria) and data obtained from the participants.

Ethical Consideration

This research project was authorized by the institutional review boards at the University of Maryland, Baltimore (HP-00084081), Rutgers State University of New Jersey (Pro2019002047), and the University of Benin Teaching Hospital, Benin City, Nigeria (ADM/E22/A/VOL. VII/14713). Parents, guardians, and caregivers were informed about study activities, and informed consent was obtained before recruitment.

Inclusion and Exclusion Criteria

Children aged 4 to 11 y whose parents or caregivers gave informed consent were invited to participate in the study. Children infected with HIV or HBV or with either physical, clinical, or mental incapacity were excluded.

Sample Size

The sample size used in this study followed the sample size of the DOMHaIN study; however, 245 participants with the complete set of data for caries, complete blood count, and inflammatory markers were recruited for this study. For statistical significance and power of 0.05 and 0.80, respectively, a sample size of n = 245 would ensure that the 95% confidence interval for the mean difference in WBC levels would have a margin of error of no more than three units (3%) comparing caries-affected with caries-free children given the standard deviation of 0.05 (5%) observed in our previous study (Coker et al. 2018).

Data Collection and Measures

Medical and dental history, demographic data, and oral health/caries assessment data were obtained using a well-structured questionnaire from all participants in this study.

Complete Blood Cell Count Analysis and Estimation of Markers of Inflammation

Five milliliters of whole blood was obtained from each participant and dispensed in EDTA containers for complete blood cell count analysis. Complete (full) blood count analysis was done to assess the hematologic indices of participants using Sysmex KP300 following the manufacturer’s instructions. Inflammatory markers such as NLR, PLR, and systemic immune-inflammatory index (SII) were calculated from the obtained parameter of the full blood count as previously described (Idemudia et al. 2021). Briefly, NLR was calculated as the ratio of the neutrophil count to lymphocyte count; PLR was calculated as the ratio of the platelet count to lymphocyte count. The SII was defined as follows: SII = neutrophil × platelet/lymphocyte.

Oral and Dental Examination and Caries Assessment

The examination of the head and neck, oral mucous membranes, lymph nodes, caries, and missing teeth was carried out by trained and qualified dentists. Intraoral examination was performed to determine the presence or absence of caries and their severity using the World Health Organization (WHO) criteria for the assessment of caries; the International Caries Detection and Assessment scores and the decayed, missing, and filled teeth (DMFT) indices were calculated (WHO 1997; Gugnani et al. 2011). Radiographs were not used to determine caries definitively or to determine the affectation of the pulp. Dentists were trained to examine, calibrate, and effectively diagnose and differentiate between sound surfaces and noncavitated caries lesions as previously described (Coker et al. 2021; Akhigbe et al. 2022).

Statistical Analysis

Using the statistical program SPSS Statistics for Windows, version 25 (IBM Corporation) and Graph Pad Prism 9.5.0 for Windows 7 (Graph Pad Software), the obtained data were analyzed using the chi-square (χ²) test, Student’s t test, 2-way analysis of variance (with heterogeneity and normality checks done), and Spearman’s correlation. The categorical variables were presented as numbers and percentages in brackets and continuous variables as the mean ± standard error of the mean. A P value of <0.05 was considered significant for all statistical tests.

Results

A total of 245 children were enrolled in the study, of whom 125 were HEU and 120 HUU. It was observed in the survey that caries was present in 15.2% and 15.8% of HEU and HUU, respectively. There was no significant association between HIV exposure status and caries development (P = 0.89). The study had 114 females and 131 males, with 20.2% and 11.5% having caries, respectively. There was some evidence of an association between sex and the development of caries (P = 0.06). However, other sociodemographic characteristics such as the mother’s educational status, age group, anemia status, and delivery method examined in the study had no association with dental caries (Table 1).

Table 1.

Sociodemographic Characteristics of the Study Population with Relation to Caries Status.

Characteristic	Variable	Number Tested	Caries Present, n (%)	P Value
Group	HEU	125	19 (15.2)	0.89
	HUU	120	19 (15.8)
Gender	Female	114	23 (20.2)	0.06
	Male	131	15 (11.5)
Mothers’ educational status	Above secondary	91	11 (12.1)	0.09
	Never schooled	18	0 (0.0)
	Primary	37	8 (21.6)
	Secondary	99	19 (19.2)
Age group	≤6 y	79	12 (15.2)	0.92
	>6 y	166	26 (15.7)
Anemia status	Anemic	176	28 (15.9)	0.78
	Nonanemic	69	10 (14.5)
Delivery method	Vaginal	198	33 (16.7)	0.62
	Cesarean section	40	4 (0.1)
	Assisted vaginal delivery	1	0 (0.0)
	Emergency cesarean section	6	1 (16.7)

HEU, HIV exposed but uninfected; HUU, HIV unexposed/uninfected.

The study examined hematologic indices with caries status among all study participants, which revealed that there was a slight reduction in the total WBC count (P = 0.05) and neutrophil count (P = 0.04) in caries-affected children compared with caries-free children (Table 2). Although there was no significant difference in the levels of other hematologic indices such as red blood cell (RBC) count, hemoglobin concentration, hematocrit, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and platelet count when comparing caries-affected with caries-free children, lymphocyte count was significantly higher in caries-affected (56.8% ± 2.3%) compared with caries-free (51.2% ± 0.9%) children (P = 0.02; Table 2). The effects of caries on some surrogate markers of inflammation, such as CD4 count, CD8 count, CD4/CD8 ratio, NLR, PLR, SII, and mean platelet volume, were compared in this study. There was no significant difference in their levels in caries-affected children and caries-free children (Table 2).

Table 2.

Examining the Association between Surrogate Markers of Inflammation and Dental Caries Status for All Participants.

	Caries Affected	Caries Free
Parameter	n = 38	n = 207	P Value
Total white blood cell count (×103 cells/µL)	5.5 ± 0.3	6.5 ± 0.2	0.05
Red blood cell count (×106 cells/µL)	4.4 ± 0.1	4.7 ± 0.2	0.66
Hemoglobin concentration (g/dL)	11.5 ± 0.2	11.3 ± 0.1	0.43
Hematocrit (PCV) (%)	34.7 ± 0.5	34.2 ± 0.3	0.39
MCV (fL)	78.5 ± 0.9	77.2 ± 0.4	0.25
MCH (pg)	26.0 ± 0.5	25.5 ± 0.2	0.29
MCHC (g/dL)	33.1 ± 0.3	33.1 ± 0.2	0.90
Platelet count (×103 cells/µL)	310.6 ± 15.6	332.3 ± 12.9	0.48
Lymphocyte count (%)	56.8 ± 2.3	51.2 ± 0.9	0.02
Neutrophil count (%)	35.0 ± 2.2	39.7 ± 0.9	0.04
CD4 count (cells/µL)	1,029.5 ± 60.0	1,048.3 ± 35.3	0.83
CD8 count (cells/µL)	584.8 ± 41.4	614.1 ± 21.7	0.58
CD4/CD8 ratio	2.0 ± 0.1	2.1 ± 0.2	0.77
NLR	0.7 ± 0.1	1.0 ± 0.1	0.11
PLR	109.9 ± 6.1	115.2 ± 4.9	0.66
SII	248.5 ± 39.8	322.0 ± 24.1	0.21
MPV	10.6 ± 0.2	10.6 ± 0.1	0.44

MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin concentration; MCV, mean corpuscular volume; MPV, mean platelet volume; NLR, neutrophil-lymphocyte ratio; PLR, platelet-lymphocyte ratio; PCV, packed cell volume; SII, systemic immune-inflammatory index.

Values = mean ± standard error of the mean (SEM).

Analysis of the combined impact of perinatal HIV exposure and dental caries on the studied hematologic parameters and markers of inflammation revealed that there was no significant interaction of perinatal HIV exposure and caries status with the levels of all studied parameters (Table 3).

Table 3.

Examining the Association between Surrogate Markers of Inflammation and Dental Caries Status by Perinatal HIV Exposure.

	HEU		HUU
	Caries Affected	Caries Free	Caries Affected	Caries Free
Parameter	n = 19	n = 106	n = 19	n = 101	P Value a
Total white blood cells count (×103 cells/µL)	5.4 ± 0.4	6.1 ± 0.2	5.6 ± 0.5	7.0 ± 0.4	0.47
Red blood cell count (×106 cells/µL)	4.5 ± 0.1	4.5 ± 0.1	4.4 ± 0.1	4.9 ± 0.5	0.51
Hemoglobin concentration (g/dL)	11.5 ± 0.2	11.5 ± 0.1	11.4 ± 0.3	11.1 ± 0.1	0.63
Hematocrit (PCV) (%)	34.9 ± 0.6	34.5 ± 0.3	34.5 ± 0.9	33.9 ± 0.4	0.91
MCV (fL)	77.6 ± 1.5	77.6 ± 0.6	79.3 ± 1.1	76.8 ± 0.6	0.37
MCH (pg)	25.6 ± 0.8	25.8 ± 0.3	26.4 ± 0.6	25.1 ± 0.3	0.20
MCHC (g/dL)	33.0 ± 0.4	33.2 ± 0.2	33.2 ± 0.3	32.9 ± 0.3	0.39
Platelet count (×103 cells/µL)	313.2 ± 19.4	311.2 ± 9.3	307.9 ± 25.1	354.5 ± 24.5	0.46
Lymphocyte count (%)	56.9 ± 3.5	51.9 ± 1.3	56.7 ± 3.0	50.5 ± 1.4	0.80
Neutrophil count (%)	35.9 ± 3.5	39.6 ± 1.3	34.1 ± 2.8	39.8 ± 1.2	0.57
CD4 count	937.0 ± 66.9	1,024.3 ± 42.0	1,122.0 ± 96.9	1,073.5 ± 57.6	0.51
CD8 count	548.6 ± 57.3	611.0 ± 28.5	621.0 ± 60.2	617.3 ± 33.0	0.56
CD4/CD8 ratio	2.0 ± 0.2	2.1 ± 0.3	2.0 ± 0.2	2.1 ± 0.2	0.96
NLR	0.8 ± 0.1	1.0 ± 0.1	0.7 ± 0.1	1.0 ± 0.1	0.79
PLR	112.5 ± 8.5	112.7 ± 5.2	107.4 ± 9.1	117.8 ± 8.3	0.76
SII	252.6 ± 48.8	291.9 ± 29.4	244.4 ± 64.2	353.7 ± 38.6	0.62
MPV	10.5 ± 0.2	10.5 ± 0.12	10.7 ± 0.3	10.6 ± 0.1	0.99

Values = mean ± standard error of the mean (SEM).

HEU, HIV exposed but uninfected; HUU, HIV unexposed/uninfected; MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin concentration; MCV, mean corpuscular volume; MPV, mean platelet volume; NLR, neutrophil-lymphocyte ratio; PLR, platelet-lymphocyte ratio; PCV, packed cell volume; SII, systemic immune-inflammatory index.

^aP values are adjusted for gender.

Evaluation of the impact of perinatal HIV exposure on the hematologic parameters and markers of inflammation studied revealed that there was no significant difference in the levels of most parameters when comparing the HEU and HUU groups apart from hemoglobin concentration, which was significantly higher in children in the HEU group than in children in the HUU group (P = 0.05), and total leucocyte (WBC) count, which was significantly lower in children in the HUU group than in children in the HUU group (P = 0.03). All other markers did not differ significantly between HEU children and HUU children (Fig. 2).

Figure 2.

Comparison of surrogate markers of inflammation with status of perinatal HIV exposure among study participants. The studied parameters were compared with HIV exposure status (HIV exposed but uninfected [HEU] and HIV unexposed/uninfected [HUU]) using Student’s t test, and a P value of 0.2 was used as the threshold to select the figures for presentation. The parameters within this threshold are hemoglobin concentration (Hb Conc; P = 0.05), total leucocyte count (WBC; P = 0.03), mean corpuscular hemoglobin (MCH; P = 0.19), and platelet count (PLT; P = 0.11) as shown. SE, standard error.

There was no significant difference in the DMFT scores of the subjects with caries among the HEU population (1.88 ± 0.72) and HUU population (2.63 ± 0.96) in this study. There was also no significant correlation between most of the studied hematologic indices and markers of inflammation with DMFT scores of participants apart from lymphocyte count, which showed a significant positive correlation with DMFT scores (P = 0.04; Appendix Table).

Discussion

To the best of our knowledge, this is among the first studies examining the potential bidirectional relationship between immunologic and hematologic parameters and dental caries and the differences observed based on whether children were perinatally exposed to HIV. We found an association between some of the studied markers and caries in both children perinatally exposed to HIV and those not perinatally exposed.

Dental caries, a microbial and infectious disease that leads to demineralization of enamel and dentin over time, is often triggered by inflammatory responses. Several studies have shown that perinatal HIV infection and exposure affect immunologic and hematologic parameters (Schramm et al. 2010). Hematologic and immunologic parameters are fundamental components of systemic health, so understanding their relationship with caries (dental health) is critical, particularly in perinatal HIV exposure (Awulachew et al. 2020).

Although most children in this study were anemic given the hemoglobin concentrations, we observed that caries had no significant association with RBC indices (blood count, hemoglobin concentration, hematocrit value, MCV, MCH, and MCHC). These findings differ from those of a previous report (Hamamcılar et al. 2019), which showed a relationship between RBC indices and oral/dental health problems, and recent studies have also closely linked iron deficiency anemia with the risk for dental caries (Tang et al. 2013; Sofola et al. 2014). The fact that participants in our study were screened clinically for symptoms of iron deficiency anemia and other confounding factors that could affect blood cell indices before inclusion in this cohort study might account for this observed result. In contrast, there was a slight reduction in the total WBC count of caries-affected children compared with their caries-free counterparts. Previous studies suggest that caries is associated with anemia for various reasons in a bidirectional sense. Specifically, caries might contribute to anemia due to poor nutrition and insufficient iron intake. However, from early caries to fulminant cellulitis, dental infections have no impact on the RBCs directly (Hamamcılar et al. 2019). Dietary variables, genetic (congenital) factors, environmental factors, inflammatory processes, and other factors can contribute to anemia and other blood disorders. Persistent inflammation may boost cytokine production, notably caused by pulpitis and tooth abscesses. Chronic anemia may be spurred by cytokines such as interleukin-1 that prevent the bone marrow’s epitopes from functioning. However, anemia, which can be an hypoproliferative disorder due to the reduced plasma iron concentration, was not prevalent in our study, as iron may have been released from other extraneous sources such as the reticuloendothelial iron storage to make up.

Although there is a paucity of data on the relationship between leucocyte count and dental caries, the observed slight reduction in the leucocyte counts of caries-affected children is consistent with a previous study by Maganti (2020). Although this reduction was not pathogenic, it is a well-known fact that leucocytes constantly engage in immunosurveillance in healthy tissue, which is a continual sampling of their surroundings to detect pathogenic microbes. Due to the escalation of the inflammatory process when infections are found, their numbers rapidly increase. During this response, leukocytes from the circulatory system are stimulated to stick to endothelial cells lining blood vessels before moving out of the blood vessel to the site of infection; this may be the reason behind the reduced leucocyte count in children with caries observed in this study.

Our study also revealed a significantly higher lymphocyte count and a lower neutrophil count among the children with dental caries compared with their caries-free counterparts. This difference was further substantiated by the significant positive correlation of lymphocyte count with the DMFT scores in this study. This may be because neutrophils are the first-line cells to be drawn to an inflamed tissue to capture and eliminate invasive germs; this is followed by monocytes, which leads to the development of macrophages, thereby resulting in the depletion of neutrophils in the systemic circulation (Gitalis et al. 2019). Therefore, the observed higher lymphocyte count in caries-affected children in this study may be a mere compensatory mechanism due to caries, especially as lymphocytes are primarily involved in responses in chronic infections, and neutrophils and lymphocytes are known to have reversed effects in most disease states.

Although there was a reduction in the levels of all studied markers in caries-affected children, none were significant. To our knowledge, this study is the first to evaluate the relationship between dental caries and some of these surrogate inflammatory markers. The NLR, PLR, and systemic immune inflammatory index (SII) stand out as new biomarkers of inflammation as they are helpful indicators that forecast disease progression and mortality in several inflammatory diseases. From the literature, the observed reduction of these markers in caries-affected children confirms that caries, although an inflammatory disease, does not induce high systemic inflammation since there were no significant difference in the markers, especially PLR (Acharya et al. 2019).

Reports from our group (Coker et al. 2018; Coker et al. 2021; Akhigbe et al. 2022) and others (Faé et al. 2023) suggest a higher caries burden in children perinatally infected with HIV (likely due to immune and salivary dysfunction). In previous reports, we did not observe a difference in caries experience when comparing the HEU and HUU groups. As before, this study reports no significant differences in caries experience comparing HEU and HUU groups in this age group. Nevertheless, according to recent research, compared with their HUU contemporaries, HEU infants’ developing immune systems differ early in life (Faé et al. 2023). Against this background, our study sought to examine the effect of perinatal HIV exposure on the relationship between hematologic and surrogate inflammatory markers and dental caries in school-aged children. Although total leucocyte counts were lower among caries-affected children in the HEU group and caries-affected children in the HUU group compared with the other groups, there were no significant differences. Considering the limited data availability and the unique nature of this study, it appears to be the first of its kind to explore the potential relationship between caries and leucocyte count in children exposed or unexposed to HIV. While the paucity of data hinders a comprehensive discussion, the preliminary findings suggest a noteworthy association between caries and leucocyte count. However, it is crucial to note that the recent study conducted by Azab and Aljefari (2022), which investigated the impact of caries on RBC parameters, presents contrasting results to our study.

Moreover, the observed inconsistency in the HIV-exposed group raises an intriguing point. It is plausible that HIV exposure could be a confounding factor influencing the relationship between caries and leucocyte count in this specific subgroup. This necessitates a call for further in-depth studies. Prior research has demonstrated that infants exposed to HIV and ART exhibit lower neutrophil counts compared with their unexposed counterparts, and this effect can persist for up to 8 y of life (Faé et al. 2023). This noteworthy finding in our study may provide an explanation for why the combined effect of HIV exposure and caries became unnoticed compared with the observed significantly decreased platelet counts and neutrophil count of caries-affected HUU children than their caries-free counterparts, as all the children included in this study were within that age (European Collaborative Study 2004; Faé et al. 2023).

While evaluating the relationship between perinatal HIV exposure and the studied markers (Fig. 2), it was evident that all parameters, except for hemoglobin concentrations and WBC counts, of the other markers exhibited no significant differences. Specifically, the hematologic markers were notably higher in the HEU group, whereas the WBC counts were significantly lower compared with that of the HUU group. These findings, particularly regarding WBC counts, are consistent with previous research (Obumneme-Anyim et al. 2016; Rotheram-Borus et al. 2021), which has reported alterations in the immune system and hematologic parameters in HEU neonates. The observed changes, characterized by reduced levels of hematologic parameters in the HEU group compared with the HUU group, have been linked to both in utero exposure to HIV proteins and the prolonged exposure to combination ART (Obumneme-Anyim et al. 2016; Rotheram-Borus et al. 2021).

In essence, the results of this study align with existing literature, affirming that perinatal HIV exposure can have a discernible impact on hematologic markers in neonates. The observed variations, especially in WBC counts, support the notion that alterations in immune system parameters are associated with both exposure to HIV proteins during pregnancy and extended ART use (Obumneme-Anyim et al. 2016). However, the finding of significantly higher hemoglobin levels in children in the HEU group compared with children in the HUU group in our study diverges from the majority of existing studies, in which hemoglobin was found to be reduced in HEU compared with HUU groups (Shah 2013; Obumneme-Anyim et al. 2016; Rotheram-Borus et al. 2021). This disparity could be attributed to the consistent health education provided to mothers living with HIV of the children in the HEU group, emphasizing the importance of a well-balanced diet rich in protein and blood-enhancing nutrients such as vegetables and soya beans powder. These nutritional recommendations, readily available within the clinic, may have positively influenced the feeding habits of the children born to mothers living with HIV, leading to higher hemoglobin levels in the HEU group. In addition, our study is distinctive in focusing on a cohort of children aged between 4 and 11 y, which differs from the age ranges in most previous studies. This unique age group might contribute to the observed variation, especially considering that sociodemographic characteristics were similar among the study participants. However, the level of education of mothers was not objective enough to ascertain the level of adherence to the use of recommended diet and nutritional requirements by participants to have resulted in this difference; hence, more studies may be needed in this regard.

In our study, we also observed no significant difference in the mean DMFT scores of children in the HEU group and children in the HUU group, as noted in other studies (Coker et al. 2018; Moscicki et al. 2019). Although there was no significant correlation of DMFT scores with the markers of inflammation studied, the observed significant differences in the values of the markers of inflammation of caries-affected children from that of caries-free children in both HIV-exposed and unexposed group is because caries is an inflammatory disorder and would require more studies.

The main limitation of our study is the sample size, as not all participants from the DOMHaIN cohort were included in this analysis. Nevertheless, this random subset provides unique and valuable insight in the potential association between markers and caries in a well-characterized cohort of HEU and HUU children. While we were unable to further analyze conventional markers of inflammation such as cytokines, we believe that this is a foundation for further investigations.

Conclusion

Our study has shown that leucocytes and some of their subsets (neutrophils and lymphocytes) are associated with caries. While the overall impact of perinatal HIV exposure on this relationship is negligible, large, comprehensive studies are needed to clarify further the role perinatal HIV exposure might play. However, we posit a strong, possibly bidirectional, relationship between key inflammatory mediators and caries. These markers could be included as a likely parameter in studies exploring the oral-systemic relationship. In combination with other inflammatory mediators, NLR, PLR, and SII may help stratify the severity of caries, particularly in lieu of a detailed dental examination and a screening tool for a wide population of children uninfected with caries.