Differential Dynamics of HIV Infection in Humanized MISTRG versus MITRG Mice

Humanized mice are a powerful tool to study HIV in vivo. The recently generated mouse strains MITRG and MISTRG, which differ in human SIRPα expression, support an improved human myeloid lineage development from human hematopoietic stem and progenitor cells. The rationale of the study was the characterization of the two mouse strains during an HIV infection with CCR5- and CXCR4-tropic viruses. Upon HIV infection, we observed HIV dissemination and sustained viral load over 20 wk in peripheral blood in both reconstituted mouse strains. However, HIV RNA levels were significantly lower in MITRG mice compared with MISTRG mice during the first 8 wk postinfection. HIV-infected MISTRG mice showed lymphocyte activation and changes in lymphocyte subsets in blood and spleen, recapitulating hallmarks of HIV infection in humans. Depletion of murine tissue-resident macrophages in MITRG mice led to significantly elevated viral loads, and lymphocyte levels were similar to those in HIV-infected MISTRG mice. Depletion of CD8+ T cells in MISTRG mice before HIV infection resulted in substantially decreased CD4+ T cell levels, indicating functionality of human CD8+ T cells; depletion of CD4+CD8+ thymocytes may have contributed, in part, to the latter finding. In summary, MITRG and MISTRG mice represent novel HIV mouse models, despite differential HIV dynamics