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

Summary HIV-Exposed Uninfected (HEU) infants are a rapidly expanding population in sub-Saharan Africa and are highly susceptible to disease caused by encapsulated bacteria in the first year of life. The mechanism of this increased risk is still poorly understood. We therefore investigated if HIV exposure dysregulates HEU infant immunity and if this is amplified by human herpes virus infection (HHV). Here, we compared monocyte enzymatic function, innate and adaptive immune cell phenotype, and vaccine-induced antibody responses between HEU and HUU infants. 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 HUU infants. There was no difference in the prevalence of HHV infection between HEU and HUU infants. Our findings suggest that even in the era of antiretroviral therapy (ART)-mediated viral suppression, HIV exposure dysregulates monocyte and B cell function during a vulnerable period of immune maturation in infancy. This may contribute to the high rates of invasive bacterial disease and pneumonia in HEU infants.