Studying NeuroHIV and addictive substances in a human microglia-neuron chimera mouse model - PROJECT SUMMARY HIV and substance use disorder (SUD) alter brain functions, but current in vitro and in vivo models fail to replicate the complexity and sanctuary role of the central nervous system (CNS) accurately. New preclinical models that appropriately incorporate relevant human CNS cell types targeted by HIV and addictive substances are urgently needed. The long-term goal is to enable deep molecular phenotyping of NeuroHIV to develop targeted therapeutic and potentially curative strategies for people with HIV and SUD. The overall objectives of this application are to establish a novel mouse model for NeuroHIV that mimics the human CNS environment and characterize the impact of ART and addictive substances on HIV persistence and neuroinflammation to validate this model for preclinical research. These objectives will be accomplished in a two-phase, milestone-driven approach. In the exploratory phase (R61), Aim 1, a chimeric humanized microglia-neural cell (huMGN) mouse model that includes human microglia, neurons, and astrocytes, differentiated from induced pluripotent stem cells (iPSCs) will be developed in human macrophage colony stimulating factor 1 knock-in (hCSF1KI) SCID mice. In this model, human microglia fully replace murine microglia while human neurons and astrocytes are engrafted locally at the implantation site. The functionality of key CNS cell types, blood-brain barrier (BBB) integrity, as well as reproducibility with iPSCs from diverse genders and ethnicities will be thoroughly evaluated before optimizing HIV infection with different CCR5-tropic viral strains using systemic and localized infection routes. Viral loads, neuropathology, and inflammation in distinct CNS cell types will be assessed and compared to mice with CCR5∆32-iPSC-derived engraftments. By the end of the R61 phase, the team will have established a robust model with reproducible engraftment success rates (≥70%) across diverse iPSCs and identified ≥1 optimal HIV infection protocol with infection rates ≥3% in relevant CNS cell types to progress to the R33 phase. In this phase, Aim 2 will introduce different ART regimens into infected mice and examine treatment effects on viral replication, latent reservoir size, BBB integrity, and neuroinflammation. In Aim 3, infected huMGN mice will be exposed to intravenous morphine, and its effect on viral load, neuroinflammation, and BBB integrity will be assessed and compared to mice treated with µ-opioid receptor (MOR) antagonist or engrafted with ∆MOR iPSCs. Further, single-cell transcriptomics will assess whether the model faithfully reproduces molecular alterations observed in human brains in the NIDA SCORCH program. The central hypothesis is that a highly reproducible in vivo model of NeuroHIV can be established that is responsive to ART and is specifically designed to study HIV-associated neurocognitive disorders in the context of SUD. The project, led by a multidisciplinary team with complementary expertise in neuroscience, HIV biology, and clinical research, and a track record of successful collaborations, will enable new CNS-tailored therapeutics and viral eradication treatments for people living with HIV and SUD.
