AAV-delivered HIV inhibitors for SHIV therapy

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PROJECT SUMMARY More 10% of the new infections in the United States were from contaminated needle sharing among people who inject drugs (PWID). Importantly, only about 50% of men and 57% of women of the PWID group had suppressed viremia. Despite the lack of a sterilizing HIV-1 cure, antiretroviral drug therapies (ART) effectively suppress viral replication in people living with HIV-1. One limitation of ART is that these small molecule drugs cannot eliminate the viral reservoir. Broadly neutralizing antibodies (bNAbs) could supplement ART and be used to reduce the viral reservoir. Several studies have shown that a single dose of a bNAb can decrease viremia in HIV-1 infected individuals, with viral rebound occurring as the bNAb concentration decreases. Adeno-associated virus (AAV) vectors may provide the means for long-term expression of bNAbs at concentrations capable of maintaining viral suppression via intramuscular inoculations. However, we and others have shown that the emergence of anti-drug antibodies (ADA) to bNAbs limits their overall expression. Here, we show that we have made significant strides overcome this host immune response. First is through utilizing immune checkpoints that regulate immune system pathways. We observed a 21-fold increase in concentrations of the HIV-1 bNAb 10-1074 in rhesus macaques when macaques were co-inoculated with an AAV vector encoding rhesus macaque PD-L1. Second, we have developed a novel, HIV-1 entry inhibitor, eCD4-Ig, which tends to be more tolerated in rhesus macaques when expressed from AAV vectors. Unlike bNAbs, we have shown that AAV vectors encoding eCD4-Ig can express the inhibitor in macaques for over a year and the ADA response against eCD4-Ig decreases over time. Because eCD4-Ig neutralizes all HIV-1, HIV-2, and SIV isolates and is difficult to escape, it may be useful when included in a therapy strategy. Our pilot studies show that low concentrations AAV-expressed eCD4-Ig can suppress SHIV infection in rhesus macaques for two years, yet viremia is still detectable. This proposal combines our AAV advancements into a single strategy to determine whether AAV-expressed inhibitors can suppress a SHIV infection and reduce the viral reservoir. In Aim 1, we will assess the therapeutic efficacy of the combination of AAV-delivered eCD4-Ig and 10-1074 after ART is lifted in SHIV-infected rhesus macaques. In Aim 2, we will determine whether suppressing an established SHIV infection with AAV- delivered eCD4-Ig and 10-1074 results in a quantitatively different viral reservoir compared to ART. In Aim 3, we will improve the safety of AAV gene therapy by developing an irreversible “kill-switch” to turn off transgene expression.