Abstract
Global elimination of pediatric human immunodeficiency virus (HIV) infections will require the development of novel immune-based approaches, and understanding infant immunity to HIV is critical to guide the rational design of these intervention strategies. Despite their immunological immaturity, chronically HIV-infected children develop broadly neutralizing antibodies (bnAbs) more frequently and earlier than adults do. However, the ontogeny of humoral responses during acute HIV infection is poorly defined in infants and challenging to study in human cohorts due to the presence of maternal antibodies. To further our understanding of age-related differences in the development of HIV-specific immunity during acute infection, we evaluated the generation of virus-specific humoral immune responses in infant (n = 6) and adult (n = 12) rhesus macaques (RMs) infected with a transmitted/founder (T/F) simian-human immunodeficiency virus (SHIV) (SHIV.C.CH505 [CH505]). The plasma HIV envelope-specific IgG antibody kinetics were similar in SHIV-infected infant and adult RMs, with no significant differences in the magnitude or breadth of these responses. Interestingly, autologous tier 2 virus neutralization responses also developed with similar frequencies and kinetics in infant and adult RMs, despite infants exhibiting significantly higher follicular T helper cell (Tfh) and germinal center B cell frequencies than adults. Finally, we show that plasma viral load was the strongest predictor of the development of autologous virus neutralization in both age groups. Our results indicate that the humoral immune response to SHIV infection develops with similar kinetics among infant and adult RMs, suggesting that the early-life immune system is equipped to respond to HIV-1 and promote the production of neutralizing HIV antibodies.IMPORTANCE There is a lack of understanding of how the maturation of the infant immune system influences immunity to HIV infection or how these responses differ from those of adults. Improving our knowledge of infant HIV immunity will help guide antiviral intervention strategies that take advantage of the unique infant immune environment to successfully elicit protective immune responses. We utilized a rhesus macaque model of SHIV infection as a tool to distinguish the differences in HIV humoral immunity in infants versus adults. Here, we demonstrate that the kinetics and quality of the infant humoral immune response to HIV are highly comparable to those of adults during the early phase of infection, despite distinct differences in their Tfh responses, indicating that slightly different mechanisms may drive infant and adult humoral immunity.