Pediatric HIV infection remains a global health crisis with a worldwide infection rate of 2.5 million (WHO, Geneva Switzerland, 2009). Children are much more susceptible to HIV-1 neurological impairments than adults, which is exacerbated by co-infections. A major obstacle in pediatric HIV research is sample access. The proposed studies take advantage of ongoing pediatric SIV pathogenesis and vaccine studies to test the hypothesis that pediatric SIV infection diminishes neuronal populations and neurogenesis in the hippocampus. Newborn rhesus macaques (Macaca mulatta) that received intravenous inoculation of highly virulent SIVmac251 (n=3) or vehicle (control n=4) were used in this study. After a 6–18 week survival time, the animals were sacrificed and the brains prepared for quantitative histopathological analysis. Systematic sections through the hippocampus were either Nissl stained or immunostained for doublecortin (DCX+), a putative marker of neurogenesis. Using design-based stereology, we report a 42% reduction in the pyramidal neuron population of the CA1, CA2, and CA3 fields of the hippocampus (p < 0.05) in SIV-infected infants. The DCX+ neuronal population was also significantly reduced within the dentate gyrus of the hippocampus. The loss of hippocampal neurons and neurogenic capacity may contribute to the rapid neurocognitive decline associated with pediatric HIV infection. These data suggest that pediatric SIV infection, which leads to significant neuronal loss in the hippocampus within 3 months, closely models a subset of pediatric HIV infections with rapid progression
