Brain Invasion by CD4⁺ T Cells Infected with a Transmitted/Founder HIV-1_BJZS7 During Acute Stage in Humanized Mice

Human immunodeficiency virus (HIV)-associated neurocognitive disorder (HAND) is one of the common causes of cognitive dysfunction and morbidity among infected patients. However, to date, it remains unknown if a transmitted/founder (T/F) HIV-1 leads to neurological disorders during acute phase of infection. Since it is impossible to answer this question in humans, we studied NOD.Cg-Prkdc scid Il2rgtm1Wjl/SzJ mice (NSG) reconstituted with human PBMC (NSG-HuPBL), followed by the peritoneal challenge with the chronic HIV-1_JR-FL and the T/F HIV-1_BJZS7, respectively. By measuring viral load, P24 antigenemia and P24⁺ cells in peripheral blood and various tissue compartments, we found that systemic infections were rapidly established in NSG-HuPBL mice by both HIV-1 strains. Although comparable peripheral viral loads were detected during acute infection, the T/F virus appeared to cause less CD4⁺ T cell loss and less numbers of infected cells in different organs and tissue compartments. Both viruses, however, invaded brains with P24⁺/CD3⁺ T cells detected primarily in meninges, cerebral cortex and perivascular areas. Critically, brain infections with HIV-1_JR-FL but not with HIV-1_BJZS7 resulted in damaged neurons together with activated microgliosis and astrocytosis as determined by significantly increased numbers of Iba1⁺ microglial cells and GFAP⁺ astrocytes, respectively. The increased Iba1⁺ microglia was correlated positively with levels of P24 antigenemia and negatively with numbers of NeuN⁺ neurons in brains of infected animals. Our findings, therefore, indicate the establishment of two useful NSG-HuPBL models, which may facilitate future investigation of mechanisms underlying HIV-1-induced microgliosis and astrocytosis.