Neuropathogenesis of Simian Immunodeficiency Virus in Neonatal Rhesus Macaques

Abstract

Neonatal human immunodeficiency virus (HIV) infection usually occurs intrapartum or postpartum and results in a higher incidence of neurological dysfunction than is seen in adults. To explore the neuropathogenesis of neonatal HIV infection, we infected neonatal macaques with simian immunodeficiency virus (SIV) and followed the course of infection focusing on early time points. Infected neonates had decreased brain growth and mild histological changes in brain that resembled those seen in pediatric AIDS, including perivascular infiltrates of mononuclear cells, mineralization of vessels in the basal ganglia, and gliosis. The perivascular lesions and gliosis were associated with the presence of occasional infected cells that required in situ hybridization with radiolabeled riboprobes for detection. Using this technique, SIV-infected cells were detected in the brain parenchyma within 7 days of infection. These findings were confirmed by nested PCR for SIVgag DNA in brain and RT-PCR for viral RNA in cerebrospinal fluid. Together, these techniques revealed SIV infection of the CNS in 12 of 13 neonates infected with SIVmac239, 3 of 3 infected with SIVmac251, and 2 of 2 infected with SIVmac239/316. The prevalence of CNS infection was indistinguishable from that of older animals infected with the same dose and stock of virus, but neonates appeared to have fewer infected cells in the CNS and detecting them required more sensitive techniques. This observation was true regardless of inoculum and despite the fact that neonates had equal or greater viral loads in the periphery compared with older animals. These data suggest that maturation-dependent host factors have a major impact on the neuropathogenesis of pediatric AIDS.

Cell Tropism of Simian Immunodeficiency Virus in Culture Is Not Predictive of in Vivo Tropism or Pathogenesis

“…35 Briefly, for RNA in situ hybridization formalin-fixed, paraffin-embedded tissue sections were pretreated in a microwave with citrate buffer (antigen unmasking solution; Vector Laboratories, Burlingame, CA) for 20 minutes at high power according to the manufacturer's instructions. Thereafter, sections were thoroughly washed, placed in a humidified chamber, and prehybridized at 45°C with hybridization buffer (containing 50% of formamide with denatured herring sperm DNA and yeast tRNA at 10 mg/ml each).…”

Simian Immunodeficiency Virus Infection in Neonatal Macaques

“…In situ hybridization for SIV was performed as previously described (13,43). To semiquantitate infected cells in tissues, sections were examined by light microscopy and positive cells were counted at ϫ100 magnification.…”

“…Mean viral loads in these neonates have previously been published elsewhere (43). Individual data are shown here for comparison with changes in T cells in tissues.…”

Macaques with Rapid Disease Progression and Simian Immunodeficiency Virus Encephalitis Have a Unique Cytokine Profile in Peripheral Lymphoid Tissues

“…The diagnosis of SIV encephalitis (SIVE) in infected animals was based on the presence of perivascular accumulations of macrophages and multinucleated giant cells and by virus infection within the central nervous system (CNS) demonstrated by in situ hybridization as previously described (14)(15)(16)31). Riboprobes for virus localization were kindly provided by Vanessa Hirsch and Charles Brown, National Institute of Allergy and Infectious Diseases, Rockville, Md., and have been described elsewhere (11).…”