2518. Development And Characterization Of Human Microglial Models To Elucidate HIV Transmission Events And Pathogenesis

BACKGROUND: HIV-associated neurocognitive disorders cause significant morbidity and mortality despite the advent of antiretroviral therapy. An understanding of fundamental mechanisms underlying HIV infection and transmission events in the central nervous system (CNS) is needed. Microglia are resident myeloid cells that are readily infected by HIV and may constitute a CNS reservoir. We evaluated and compared existing microglial cell lines and primary cell-derived microglia as potential model systems for studying HIV-microglia interactions. METHODS: We cultured two immortalized human microglial lines (HMC3, C20) and developed two primary microglial models: induced microglia (iMG) derived from primary human monocytes; and microglial-like cells (iMGL) differentiated from induced pluripotent stem cells (iPSCs). We compared these four microglial cell types to commercially available fetal microglia (PM) for a microglial comparator, and monocyte-derived macrophages as a non-microglial comparator cell. Each cell type was evaluated for the presence of typical myeloid and microglia-specific markers by flow cytometry and immunofluorescence microscopy. HIV infection was performed using macrophage-tropic HIV or VSV-G-pseudotyped HIV. RESULTS: After differentiation, the iMG and iMGL displayed characteristic microglial morphology: a spindle shape and a reduction in the central body, along with ramified cell processes. Flow cytometry revealed significant differences in surface markers among the cell types. iMG and iMGL displayed CD11b, CD45, CXCR4, CCR5 and lack of expression of CD4 and CX3CR1. In contrast, HMC3, C20, and PM were negative for CD11b, CD45, CX3CR1, CD4, CXCR4. Immunostaining showed that iMG and iMGL were positive for microglial markers TMEM119 and P2RY12. RNA Seq analysis is currently underway to determine gene expression differences between the microglial cell lines and our microglia models. In preliminary results, iMG and iMGL were both readily infected with HIV, and comparison with other lines is ongoing. CONCLUSION: There is no standard model available for defining the molecular and cellular events involved in HIV infection of microglia. Significant differences in microgial markers and in HIV receptor and coreceptor levels were noted in this study. iMG and iMGL appear to be viable microglial models susceptible to HIV infection. DISCLOSURES: All authors: No reported disclosures.