Background
Natural killer (NK) cells respond rapidly in early HIV-1 infection. HIV-1 suppression and functional cure strategies can be developed by exploiting the intrinsic function of NK cells in recognizing HIV-infected cells. In our previous work, we profiled the phenotype of human primary NK cells responsive to autologous HIV-1-infected CD4+ T cells in vitro. We characterized the patterns of NK cell ligand expression on CD4+ T cells at baseline and after infection with a panel of transmitted/founder HIV-1 strains to identify key receptor-ligand pairings for HIV recognition by NK cells. With CRISPR editing in CD4+ T cells to knockout the NKp30 ligand B7-H6, or the NKG2D ligands MICB or ULBP2, we observed reduction in NK cell responses to HIV-infected cells in some donors. We hypothesized that the function of human primary NK cells of targeting HIV can be enhanced by overexpressing NKp30 and NKG2D and further improved by expressing CARs that are designed based on these two activating NK cell receptors.
Methods
We transfected primary NK cells from peripheral blood of health donors with charge-altering releasable transporters (CARTs) to deliver mRNAs that encode unmodified NKp30 or NKG2D and a panel of CARs with the extracellular domain of NKp30. We also co-transfected NK cells with GFP mRNA to distinguish the cells that express the exogenous genes (GFP+) from the ones that naturally express NKp30 and NKG2D (GFP–). We evaluated the function of NK cells by co-culturing them with CD4+ T cells and detecting the degranulation marker CD107a and the production of cytokines IFNγ and TNFα in NK cells with flow cytometry and compared the function of GFP+ and GFP– NK cells.
Results
Overexpression of NKp30 or NKG2D in NK cells enhanced their function of targeting both HIV-infected cells and activated mock-infected autologous CD4+ T cells, but not resting CD4+ T cells, which do not express ligands of NKp30 and NKG2D. Multiple NKp30 CARs outperformed unmodified NKp30.
Conclusions
Together with our previous work, the results of our study indicate that receptor-ligand pairs including NKp30:B7-H6 and NKG2D:MICB/ULBP2 facilitate NK cell recognition of HIV-infected cells. Human primary NK cells can be engineered with NKp30-based CARs for improved function of targeting HIV. Our work suggests that NK cell activation through NKp30 and NKG2D can be exploited for designing strategies of cell therapy in conjunction with HIV Env-targeting CARs to treat HIV infection.
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