Differential CD8+ T/NK cell-mediated reduction of HIV-1 replication after combination of ART with TIGIT or KLRG1 blockade in humanized mice

Expression of TIGIT and KLRG1 has been associated to an exhausted, dysfunctional state in natural killer (NK) and CD8+ T cells from people with HIV-1 (PWH), limiting the efficacy of immunotherapies aiming at achieving a functional cure of the infection. Antiretroviral therapy (ART) does not completely reverse this immune exhaustion, and its combination with blockade of immune checkpoint receptors such as TIGIT and KLRG1 could be a promising strategy to promote control of viral replication in PWH. However, the impact of targeting these two immune checkpoint receptors has not been evaluated in vivo. In this study, we used a humanized Bone Marrow, Liver and Thymus (hBLT) mouse model of HIV-1 infection to study the impact of ART in combination with aTIGIT or aKLRG1 or a bispecific aTIGIT/aKLRG1 mAbs. Our results indicated that combination of ART with either aTIGIT or aKLRG1 mAbs led to faster reduction of HIV-1 pVL. Furthermore, viral rebound after ART interruption (ATI) was delayed in mice treated with aTIGIT and aKLRG1 mAbs. Histological detection of HIV-1 p24 in the spleen was restricted to the white pulp in the aKLRG1 mAb-treated group, which correlated with higher infiltration of IFN{gamma}+ CD8+ T cells in these histological regions and with increased cytotoxic CD107a+ Granzyme B+ CD8+ T cells in the spleen. In contrast, control of HIV-1 replication induced by the aTIGIT mAb was associated with an increased splenic CD107a+ IFN{gamma}+ NKG2C+ CD57-adaptive NK cells. In contrast, combination of ART with a bispecific aTIGIT/aKLRG1 mAb was unable to efficiently suppress viral replication or delay viral rebound after ATI, potentially by inducing apoptosis of adaptive NKG2C+ NK. Together, these results suggest that combination of ART with individual TIGIT or KLRG1 blockade may be a promising immunotherapy strategy against HIV-1 by eliciting differential immune control mechanisms.