Defective monocyte enzymatic function and an inhibitory immune phenotype in HIV-exposed uninfected African infants in the era of antiretroviral therapy.

BACKGROUND: HIV-Exposed Uninfected (HEU) infants are a rapidly expanding population in sub-Saharan Africa, highly susceptible to encapsulated bacterial disease in the first year of life. The mechanism of this increased risk is still poorly understood. We investigated if HIV-exposure dysregulates HEU immunity, vaccine-antibody production and human herpes virus (HHV) amplify this effect.

METHODS: 34 HIV-infected and 44 HIV-uninfected pregnant women were recruited into the birth cohort, followed up to 6 weeks of age; and 43 HIV-infected and 61 HIV-uninfected mother-infant pairs into a longitudinal infant cohort, at either: 5-7 to 14-15; or 14-15 to 18-23 weeks of age. We compared monocyte function, innate and adaptive immune cell phenotype, and vaccine-induced antibody responses between HEU and HU infants.

RESULTS: We demonstrate altered monocyte phagosomal function and B cell subset homeostasis, and lower vaccine-induced anti-Haemophilus influenzae type b (Hib) and anti-Tetanus Toxoid (TT) IgG titers in HEU compared to HU infants. HHV infection was similar between HEU and HU infants.

CONCLUSION: In the era of antiretroviral therapy (ART)-mediated viral suppression, HIV-exposure may dysregulate monocyte and B cell function, during the vulnerable period of immune maturation. This may contribute to the high rates of invasive bacterial disease and pneumonia in HEU infants.