Exploring Mechanisms Behind Immune Dysfunction in People Living with HIV on ART
Open Access DepositedHuman immunodeficiency virus (HIV) is a retrovirus that is harbored in multiple cellular reservoirs throughout the human body. In these cellular reservoirs, HIV can integrate into the host genome and hide out “silently” in a state known as HIV latency. While current antiretroviral therapy (ART) reduces plasma levels of HIV to undetectable levels and extends the lives of people living with HIV (PWH), it is not curative. HIV can escape ART through latency or hiding in ART-inaccessible sites. While initially expected that HIV maintains latency during ART, recent studies have highlighted continuous immune activation and inflammation despite ART, perhaps due to low-level replication in certain reservoirs and/or HIV-induced immune dysfunction. In this thesis, I explore the mechanisms behind this immune dysfunction through (1) platelet-mediated NK cell dysfunction and (2) microglia-mediated HIV-associated neurocognitive disorders. First, investigating platelet-mediated NK cell dysfunction, I developed a novel platelet isolation protocol from buffy coats to conduct autologous platelet-NK complexing experiments. Specifically investigating platelet-NK complexes (PNKCs) in PWH, we find elevated PNKCs with unique phenotypes, including elevated CD69 and reduced Nkp46. Additionally, NK cells from PWOH that are expanded in the presence of PNKCs have elevated CD69 expression and reduced NKp46 expression, mimicking the dysfunctional phenotypes of NK cells in PWH. In an in vivo simian immunodeficiency virus (SIV)-infected Rhesus macaque (RM) model, the %PNKCs were positively correlated with both plasma and cerebrospinal fluid (CSF) viral loads, suggesting a role of PNKCs in disease progression. This correlation is abolished if RMs are treated with monoclonal antibody, inclacumab, which targets platelet-mediated P-selectin interactions with other cells. With this research, we propose that chronic exposure of NK cells to platelets during HIV infection can contribute to NK cell dysfunction. To investigate the role of microglia in HIV-associated neurocognitive disorders (HAND), current in vitro HIV infection models in microglia have limitations including their (1) low resemblance to primary microglia, (2) suboptimal infection rates, (3) poor experimental tractability, and (4) less affordability. So, we developed a novel in vitro HIV infection model to address these concerns. We (1) confirmed the expression of HIV receptors on CHME5 microglia (2) increased infection using Vpx virus-like particles (VLPs), which promote SAMHD1 degradation (3) utilize EcoHIV-eGFP virus for infection, and (4) follow active infection into latency and reactivation in as little as 11 days. This infection model will be an important low-cost in vitro infection model in which the full course of HIV infection can be observed in microglia in a short amount of time. With this new model, researchers can more rapidly investigate the role of microglia in HAND. This thesis work provides important background for future research into chronic inflammation during HIV infection. Specifically, the role that platelets may play in promoting immune cell dysfunctions (such as NK cells), and a novel model that can be used to study HIV infection in microglia in vitro. Future studies might investigate the role of PNKCs in HIV disease progression and severity, how platelet interactions with NK cells could make NK cells more likely to extravasate across endothelial barriers (including the blood brain barrier), the use of platelet inhibitors as HIV therapeutics, and how platelet-mediated NK dysfunction could affect NK-based therapeutics for HIV.
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Ostermeier_gwu_0075A_17464.pdf | 2025-12-11 | Open Access |
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