Lysosome release is active HIV-infected macrophages, suggesting membrane repair to counteract perforin-mediated killing 2894

Description Compared to HIV-infected CD4+ T cells, macrophages are more resistant to NK cell and cytotoxic T lymphocyte (CTL)-mediated killing, but the mechanism of resistance is unclear. As melanoma cells use lysosome release to repair perforin pores to escape CTL attack, we hypothesized that HIV-infected macrophages do the same to protect them from NKs and CTL. To test this hypothesis, monocytes from PBMC were differentiated into macrophages and CD4+ T cells were activated using anti-CD3/CD28, then infected with HIV, CRISPR-edited to knockout (KO) β2-microglobulin (B2M) (NK cell trigger), or peptide-loaded (CTL trigger). Co-cultures with NKs and CTL were analyzed via flow cytometry and microscopy. NK and CTL-mediated killing is perforin-dependent, and assays with purified perforin suggest that macrophages are also more resistant to perforin-mediated lysis. In response to NK or CTL attack, as well as purified perforin, surface CD107a (a marker of lysosome release) increased on infected, B2M-KO, and peptide-loaded macrophages, but not CD4+ T cells. Like melanoma cells, this could contribute to perforin pore repair and resistance to killing. As lysosomal release is observed in B2M-KO and peptide-loaded macrophages, this resistance mechanism may represent an intrinsic trait of macrophages rather than a viral-mediated response, which could render macrophages a perfect “hide out” for various pathogens, such as Mycobacterium tuberculosis and human cytomegalovirus.