Regulation of Eco-Tropic Human Immunodeficiency Virus Type-1-infection by Sterile Alpha Motif and Histidine-Aspartic Domain Containing Protein-1 in a Microglial Cell Line: A novel in vitro model for studying HIV infection and latency in microglia

Microglia are considered the main human immunodeficiency virus (HIV) reservoirs in the central nervous system (CNS) due to their ability to become productively infected, produce new infectious HIV virions, and support HIV latency. The anatomical location of microglia necessitates the use of in vitro HIV infection models. However, currently available in vitro models are laced with limitations, including their (1) low resemblance to primary human microglia, (2) suboptimal infection rates, (3) poor experimental tractability, and (4) low affordability. Therefore, we sought to develop a new in vitro infection model that addresses these concerns. Here, we confirmed that microglia express sterile alpha motif and histidine-aspartic domain-containing protein-1 (SAMHD1), an antiviral mechanism that opposes HIV replication. We show that administration of simian immunodeficiency virus (SIV)-derived Vpx virus-like particles (VLPs) can reduce the levels of SAMHD1, thus allowing for increased infectivity in EcoHIV-infected CHME5 microglial cell line. With this model, we achieved high initial infection rates of 33.70% (SD 5.22%). We could also track the cells using eGFP expression during active replication, latency, and latency reversal. Further, we developed a CHME5-EcoHIV + cell line using fluorescence-activated cell sorting (FACS). We confirmed that only 18.40% (SD 7.64) of infected CHME5 exhibit latency reversal following their exposure to conventional latency reversing agents (LRAs). Our novel microglia infection model saves researchers time and money and, due to its ease of use, can rapidly contribute to curative research in the field.