Maintenance of the HIV Reservoir Is Antagonized by Selective BCL2 Inhibition

Abstract

Decay of the HIV reservoir is slowed over time in part by expansion of the pool of HIV-infected cells. This expansion reflects homeostatic proliferation of infected cells by interleukin-7 (IL-7) or antigenic stimulation, as well as new rounds of infection of susceptible target cells. As novel therapies are being developed to accelerate the decay of the latent HIV reservoir, it will be important to identify interventions that prevent expansion and/or repopulation of the latent HIV reservoir. Our previous studies showed that HIV protease cleaves the host protein procaspase 8 to generate Casp8p41, which can bind and activate Bak to induce apoptosis of infected cells. In circumstances where expression of the anti-apoptotic protein BCL2 is high, Casp8p41 instead binds BCL2, and cell death does not occur. This effect can be overcome by treating cells with the clinically approved BCL2 antagonist venetoclax, which prevents Casp8p41 from binding BCL2, thereby allowing Casp8p41 to bind Bak and kill the infected cell. Here we assess whether the events that maintain the HIV reservoir are also antagonized by venetoclax. Using the J-Lat 10.6 model of persistent infection, we demonstrate that proliferation and HIV expression are countered by the use of venetoclax, which causes preferential killing of the HIV-expressing cells. Similarly, during new rounds of infection of primary CD4 T cells, venetoclax causes selective killing of HIV-infected cells, resulting in decreased numbers of HIV DNA-containing cells. Cure of HIV infection requires an intervention that reduces the HIV reservoir size. A variety of approaches are being tested for their ability to impact HIV reservoir size. Even if successful, however, these approaches will need to be combined with additional complementary approaches that prevent replenishment or repopulation of the HIV reservoir. Our previous studies have shown that the FDA-approved BCL2 antagonist venetoclax has a beneficial effect on the HIV reservoir size following HIV reactivation. Here we demonstrate that venetoclax also has a beneficial effect on HIV reservoir size in a model of homeostatic proliferation of HIV as well as in acute spreading infection of HIV in primary CD4 T cells. These results suggest that venetoclax, either alone or in combination with other approaches to reducing HIV reservoir size, is a compound worthy of further study for its effects on HIV reservoir size.

Getting the “Kill” into “Shock and Kill”: Strategies to Eliminate Latent HIV

“…Whether combinations of Bcl-2 inhibitors like Venetoclax with LRAs that do not induce maximal T-cell stimulation also lead to the death of latently infected cells remains unclear. Interestingly, Venetoclax also leads to the selective killing of HIV infected primary T-cells during productive infection in vitro (Cummins et al, 2017) and therefore Venetoclax could also potentially be used to reduce the establishment of latency.…”

“…Fourth, the effect of these compounds on dividing and non-dividing cells should be evaluated to determine how effectively various HIV infected cell types will be cleared. To this end, a recent study found that the Bcl-2 inhibitor Venetoclax induced apoptosis of the latently infected J-Lat10.6 T cell line model (Cummins et al, 2017), in which the J-Lat10.6 cells proliferate slowly in the absence of stimulation. While Venetoclax can induce apoptosis in both dividing and non-dividing HIV infected T cells, it will be important to evaluate the impact of any kill compounds on diverse cell types to ascertain selective clearance of HIV infected cells.…”

Systems analysis by mass cytometry identifies susceptibility of latent HIV-infected T cells to targeting of p38 and mTOR pathways

“…Recently, cellular survival programs governed by BIRC5, a molecular inhibitor of apoptosis, were shown to support long-term survival of HIVinfected CD4+ T cells (63). Moreover, the Bcl-2 family has long been implicated in balancing lowlevel HIV virus production with cell survival (64)(65)(66)(67). We further showed that reactivating infected (p24+) cells express higher levels of anti-apoptotic p-Bad than latently infected (p24-) cells, suggesting that activation of viral protein expression may complicate eradication efforts.…”

Targeting apoptosis pathways in infections

“…Similarly, targeting BCL-2 with the BH3-mimetic compound ABT-199 induces apoptosis of T-cells harboring latent but also productive HIV infections. 133 This reduces the HIV reservoir and the spreading of infections in ex vivo models. Inducing apoptosis also decreases hepatitis B viral loads in preclinical infection models.…”