# Characterizing mechanisms by which HIV-infected macrophages neutralize NK cell effector functions to facilitate their persistence > **NIH NIH F31** · UNIV OF MASSACHUSETTS MED SCH WORCESTER · 2024 · $36,369 ## Abstract Project Summary In the context of human immunodeficiency virus (HIV), both CD4+ T cells and macrophages contribute to the viral reservoir within people living with HIV on combination antiretroviral therapy. Natural killer (NK) cells are the major cytolytic cells of the innate immune system, and their failure to effectively eliminate infected cells allows propagation and persistence of infection. In in vitro models of infection, HIV-infected macrophages are more resistant to NK cell-mediated killing than their CD4+ T cell counterparts, implicating macrophage-specific mechanisms of resistance. However, these mechanisms have yet to be determined. The overall objective of this proposal is to define macrophage-specific mechanisms that facilitate increased resistance to NK cell- mediated killing. The central hypothesis is that HIV-infected macrophages resist NK cell-mediated killing by reducing immediate NK cell lytic function, and antagonizing death receptor signaling. To address this hypothesis, the following aims will be pursued: Specific Aim #1 will characterize release of HIV-infected macrophage lysosomal granules towards NK cells. Published work shows that melanoma cells being targeted by CD8+ cytolytic T lymphocytes release their lysosomes at the immunological synapse to degrade perforin, protecting them from elimination. To measure lysosome release, the investigators used CD107a, which lines the membrane of lysosomes and lytic granules and is surface-exposed following degranulation. My preliminary data shows that HIV-infected macrophages increase surface CD107a expression upon co-culture with autologous NK cells. Therefore, I will investigate whether this mechanism is also being used by HIV-infected macrophages to neutralize NK cell degranulation. Specific Aim #2 will define mechanisms of HIV-infected macrophage resistance to NK cell FasL-mediated killing. Preliminary data shows that HIV-infected macrophages, but not CD4+ T cells, are not susceptible to apoptosis induced by incubation with recombinant FasL, despite both cells expressing the receptor, Fas. I will investigate whether this resistance is due to increased anti-apoptotic activity of cFLIP, which regulates caspase-8 activity. To complement these experiments, I will analyze published single- cell RNA-sequencing (scRNA-seq) datasets of human tissues to determine tissue resident macrophage expression of cFLIP and other anti-apoptotic proteins. I will compare these results to scRNA-seq that I will perform on my monocyte-derived macrophages as a comparator. Results from these studies will elucidate how HIV-infected macrophages escape NK cell-mediated killing and will ultimately inform clinical strategies utilizing NK cells to control pathogenesis. The work outlined above will be conducted at the University of Massachusetts Chan Medical School, within the Immunology and Microbiology Ph.D. program. The training plan, which will help me achieve my goal of becoming an independent investigator,... ## Key facts - **NIH application ID:** 11009219 - **Project number:** 1F31AI184128-01A1 - **Recipient organization:** UNIV OF MASSACHUSETTS MED SCH WORCESTER - **Principal Investigator:** Paula Grasberger - **Activity code:** F31 (R01, R21, SBIR, etc.) - **Funding institute:** NIH - **Fiscal year:** 2024 - **Award amount:** $36,369 - **Award type:** 1 - **Project period:** 2024-07-18 → 2027-07-17 ## Primary source NIH RePORTER: https://reporter.nih.gov/project-details/11009219 ## Citation > US National Institutes of Health, RePORTER application 11009219, Characterizing mechanisms by which HIV-infected macrophages neutralize NK cell effector functions to facilitate their persistence (1F31AI184128-01A1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/11009219. Licensed CC0. --- *[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*