Characterization of the Genotypes, Phenotypes and Neurotropism of the HIV-1 Envelope glycoproteins from two highly Neurotoxic CSF-derived isolates

HIV-1 enters the central nervous system (CNS) early after systemic infection, leading to a variety of neurocognitive and motor impairments referred as HIV-1 associated neurocognitive disorders (HAND). Perivascular macrophages and microglia cells support productive viral infection in the brain allowing the virus to subsequently adapt to the CNS environment. Our goal is to elucidate the role of the HIV-1 envelope glycoprotein (Env) during HIV-1 infection in the CNS. We obtained viruses derived from the cerebrospinal fluid (CSF) of two HIV-1-infected individuals with HIV-1-associated dementia, the most severe form of HAND. These isolates are macrophage tropic and highly neurotoxic. We amplified Env genes using single genome amplification and performed extensive genotypic and phenotypic characterization. Interestingly, we found a mixture of Env genotypes and diverse phenotypes, such as macrophage and non-macrophage tropic Env, various degrees of fusogenicity, ability to use low levels of CD4, reduced sensitivity to entry and fusion inhibitors, and neutralization by antibody against the conserved CD4 binding site. Finally, we did not find specific correlations between genetic determinants and the above reported phenotypes. Importantly, in the context of isogenic recombinant viruses, some Env were able to mediate infection of macrophages and lead to the production of conditioned medium that induces neurotoxicity in primary pure neuronal cultures. In addition, we assessed whether the supernatants of the infected macrophages with viruses expressing Env that generates neurotoxicity affected other cells such as astrocytes, microglia and microvasculature endothelial cells. We found that recombinant viruses expressing the related envelopes did not infect such cells, but morphological changes were induced. The conditioned media also increased the permeability of microvasculature endothelial cells. The effects were likely caused by combinations of elevated levels of glutamate, soluble gp120 and diverse secretion profiles of cytokines, chemokines and pro-apoptotic proteins that differed within monocytes donors. We conclude that a subset of the Jago and Doge envelopes show neurotropic phenotypes representative of viruses that adapt better to the CNS microenvironment.