447 – Differential CD8T/NK Cell-Mediated HIV-1 Control After TIGIT or KLRG1 Blockade and ART in hBLT Mice

Background

The combination of antiretroviral therapy (ART) and checkpoint receptor blockade may be an attractive strategy and to enhance immune responses, reduce persistent reservoirs and promote control of viral replication in people living with HIV-1 (PWH). Expression of inhibitory receptors TIGIT and KLRG1 has been linked to dysfunctional natural killer (NK) and CD8+ T cells, limiting the capacity to eliminate HIV-infected CD4+ T cells from PWH in vitro. However, the potential benefits of specific targeting TIGIT and KLRG1 in HIV-1 infection have not been evaluated in vivo.

Methods

Reconstituted humanized Bone, Marrow, Liver and Thymus (hBLT) mice (n=15) were intravenously infected with 5,000 TCID₅₀ HIV-1_JRCSF and n=5 mice remained uninfected. After 7 days, oral ART was administered to all infected animals for two weeks in combination with a weekly intraperitoneal injection of either human IgG1 isotypic control, aTIGIT or aKLRG1 mAbs (n=5 mice per group). Upon ART interruption (ATI), immunotherapy was maintained for two additional weeks. HIV-1 plasma viral load (pVL) was quantified at 3, 6, 10 and 13 days after ATI. NK and CD8+T cell subsets were analyzed longitudinally in blood and in the spleen by FACS.

Results

HIV-1 pVL was more significantly reduced to undetectable levels after co-administration of ART with aTIGIT (83%; p<0.0001), aKLRG1 (67%; p=0.0147) than combination with Isotype Abs (50%). Further, mice treated with aTIGIT (median pVL 1.515×10³ copies/mL) and aKLRG1 (median pVL 1.562×10³ copies/mL ) mAbs showed control of viral rebound compared to mice receiving Isotypic control Ab (median pVL 7.18×10³ copies/mL; p<0.0001 in both cases) at 6 days post-ATI. Moreover, histological detection of HIV-1 p24 in the spleen was significantly associated with rebound pVL (p=0.0076) at 10 days post-ATI and these infected cells were restricted to the white pulp in the aKLRG1 group (p=0.0286). Notably, aTIGIT treatment was associated with a increased splenic IFNg+TNFa+CD107a- CD8+ T cells (40% Isotype vs 80% aTIGIT, p<0.0001) and higher CD107a+ NKG2C+ CD57- NK cells associated with lower pVL (3% Isotype vs 17.10% aTIGIT; p=0.01) in these mice. In contrast, lower pVL in the aKLRG1 group was associated with increased Granzyme B+ CD8+ T cells (p=0.0083) and higher CD107a+ TNFa+ NK cells (p=0.04) in the spleen.

Conclusions

Differential modulation of NK and T cell by ART and TIGIT or KLRG1 blockade may be relevant for future immunotherapies against HIV-1.