NOVEL MECHANISMS OF VIRAL RESERVOIR ERADICATION TO ACHIEVE HIV CURE
Anti-retroviral therapy (ART) effectiveness has turned HIV infection into a chronic disease with a significant reduction in viremia seen in people living with HIV (PLWH). However, curative therapy remains elusive due to the inability to eradicate viral reservoirs, perpetuating the virus in PLWH. The most examined and well-characterized viral reservoirs are different populations of circulating CD4+ T lymphocytes, mainly due to easy access to blood. However, there is no reliable quantification of viral reservoirs in tissues or other cell types, including myeloid cells. Only recently, phylogenetic analysis of reactivating viruses indicates that viral rebound cannot be explained only by viral reactivation of CD4+ T cells; thus, alternative cell types such as myeloid cells need to be considered and fully examined.
Our data using post-mortem brain samples from individuals under long-term ART indicates that microglia/macrophages are the brain's main viral reservoirs. Importantly, residual viral mRNA and protein production was detected in these cells. To examine the mechanism of HIV infection, silencing, and reactivation, we have generated a protocol to induce long-term latency using primary cells (microglia and macrophages) with excellent reproducibility and response reactivating agents. Further, using laser capture microdissection (LCM), we isolated cells containing HIV-integrated DNA from the brains of HIV-infected individuals under long-term ART (a similar approach was taken for the in vitro cultures) and identified by proteomics a unique set of enzymes upregulated in the latently infected microglia/macrophages as compared to neighboring uninfected cells. This unique proteome profile is associated with unusual energy sources such as glutamate and glutamine instead of glucose and lipids to produce energy and long-term survival. Glutamate and glutamine are the brain's major neurotransmitters and provide an unlimited energy source for viral brain reservoirs. More importantly, we identified that myeloid viral reservoirs lose the capacity to switch between different carbon sources compared to uninfected cells. Thus, blocking glutamate/glutamine transport, glutamine synthetase and/or glutaminase activity, or overloading the system with α-Keto-Glutarate (α-KG) induces up to 90% killing of myeloid viral reservoirs even in the absence of viral replication or reactivation. Our hypothesis is that “brain myeloid viral reservoirs have a unique metabolic signature that can be exploited to eradicate them from the brain.” We expect to eliminate viral reservoirs in different tissues by targeting their unique metabolic pathways to achieve a functional cure.