Immunosuppression to Blame for Oral Microbiota Change in Children With HIV

Bacterial changes in the oral cavity from immunosuppression, not HIV itself, are more likely to blame for the greater incidence of oral caries in children aged 6 months to 6 years, reports a study from the Department of Oral Biology at the Rutgers University School of Dental Medicine published last month in Scientific Reports. The study attempted to address a knowledge gap on how HIV or perinatal exposure to HIV can alter salivary microbial composition.

These findings contradict recent study results that demonstrate HIV is to blame for the overall higher risk of dental cavities, according to a press release on the Rutgers results. They also “debunked our hypothesis, but it's very exciting as it raises new ones,'' stated Modupe Coker, MDS, MPH, PhD, lead study author and an epidemiologist and professor at Rutgers Dental, in the release. “HIV infection alone might not be a significant risk factor, which was the assumption. Immune status, function, and competency play a much bigger role.”

Samples of saliva, to determine oral microbiota, and blood, for white blood cell levels, were collected from 296 children aged 6 months to 6 years who were under the care of the HIV/AIDS pediatric clinic at the University of Benin Teaching Hospital (UBTH) in Benin City, Nigeria; were referred for study inclusion through their mothers receiving care at the adult antiretroviral clinic at UBTH; or were receiving care at well-baby/child pediatric clinics. These children fell into 1 of 3 groups:

• HIV positive/infected since birth (HI; n = 94)
• Exposed to HIV through their mothers but uninfected (HEU; n = 98)
• Unexposed to HIV, uninfected (HUU; n = 94)

Following 16S ribosomal RNA gene sequencing on the 286 saliva samples (for 11,252,869 sequences), immune status was shown to have a stronger association with bacterial profiles (P < .001) than perinatal HIV infection among the HI group compared with the HEU (P = .04) and HUU (P = .11) groups. In addition, those in the HI group who had normal immune levels thanks to antiviral treatment had a lower prevalence of cavities compared with the HIV-negative children with weakened immune systems.

The mean (SD) age of the children was 40.2 (21) months, and their mean CD4 lymphocyte count was 1129 (554) cells/mm3; close to one-third (31.5) were on antiretroviral treatment, which “has been shown to significantly impact the composition of salivary microbiota,” the authors noted; and a plurality (34.3%) were both formula and breast fed.

Children in the HI group were also shown to have lower CD4 counts and percentages with more oral caries and diseases (P < .05), and CD4 percentage “remained significantly associated with diversity distance matrices in the <36-months and >36-month age groups.

The most prevalent oral bacteria overall were Streptococcus, Actinomyces, Rothia, Leptotrichia, Prevotella, Veillonella, Neisseria, Porphyromonas, Fusobacterium, Corynebacterium, and Granulicatella. Among these genus:

• Rothia mucilaginosa was more prevalent in younger children with a low CD4 percentage.
• Actinomyces sp., Porphyromonas pasteri, and Prevotella nanceiensis were more prevalent in older children with a low CD4 percentage.
• Actinomyces sp. and R mucilaginosa (q < 0.1) and P pasteri, P nanceiensis, and C durum (P < .05; q > .01) in higher numbers were all positively associated with an increase in dental caries.

“Our results suggest that, although there are some taxonomic differences when comparing salivary microbiota of HI and HEU children from unexposed and uninfected counterparts (HUU children), immunosuppression had a more pronounced effect on salivary bacterial composition,” the authors noted. “Oral microbes maintain a delicate balance during health, but this balance might be compromised with immunosuppression leading to conditions (like dental caries) that could manifest in the oral cavity.”

Larger longitudinal studies that examine supra- and subgingival placque and viral load assessments are required, they noted, as well as studies of the temporal microbial, behavioral, and environmental factors that may increase dental disease risk.

Reference

Coker MO, Mongodin EF, El-Kamary, SS, et al. Immune status, and not HIV infection of exposure, drives the development of the oral microbiota. Scientific Reports. Published online July 2, 2020. doi:10.1111/resp.13877