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, includes coursework on basic/advanced principles
of immunology and ethics of research. Finally, I will attend national/international conferences to receive feedback
from external scientists on my research and engage with others performing cutting edge research.
