Role of HIV-1 Nef and Vpu in viral replication and CD4+ T cell depletion. Public Deposited

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  • March 19, 2019
Creator
  • Watkins, Richard
    • Affiliation: School of Medicine, Department of Microbiology and Immunology
Abstract
  • HIV-1, within its 9-gene genome, encodes a set of accessory proteins regarded as nonessential for in vitro replication, but that are critical for optimal viral replication in vivo. Specifically, Nef and Vpu, two proteins with some overlap in function, have been implicated in robust viral replication and disease progression. As part of my dissertation I used an LAI with a simple frame-shift in nef, ablating the expression of Nef, and demonstrated the in vivo pressure to restore the nef ORF. I went on to show, that the protein resulting from the reopening of the nef ORF was defective for CD4 downmodulation. Mice infected with LAI containing these in vivo generated nefs displayed reduced viral loads and the CD4 depletion compared to mice infected with wild type LAI. When the infections with a more severally defective nef that was irreversibly inactivated are compared to infections with LAI containing Nefs defective for CD4 downmodulation, I found that nearly 50% of the pathogenic phenotype of wild type LAI could be attributed to Nef's ability to downmodulate surface expression of CD4. I also examined the role that Vpu plays in replication and CD4+ T cell depletion during an LAI infection in BLT-humanized mice. These investigations demonstrate that Vpu is required for rapid CD4+ T cell depletion and high viral loads. Of interest is that Vpu-defective HIV-1 expressing no Vpu and HIV-1 expressing Nef specifically lacking the ability to downmodulate CD4 have strikingly similar replicative and pathogenic phenotypes. I also examined the contribution nef makes to high viral loads and CD4+ T cell depletion during the infection of the CCR5-tropic virus, HIV-1 JRCSF. Mice infected with JRCSF expressing defective nefs have lower viral loads and maintain a higher percentage of their CD4+ T cells than mice infected with wild type JRCSF. I also demonstrate that like LAI, JRCSF expressing a frame-shifted nef restores the nef ORF. I show in this dissertation that the Nef produced by one of these in vivo-generated nef mutants is also specifically defective for CD4 downregulation. I also performed a longitudinal analysis of peripheral blood CD8+ T cell activation to demonstrate that Nef is required for increased T cell activation during JRCSF infection. My dissertation demonstrates that the high viral loads and CD4+ T cell depletion seenduring HIV infection depends on the presence of Nef and Vpu. Specifically, Nef has a critical role in determining the outcome of infection. The presence of Nef is required for immune activation, which may explain differences in pathogenic outcomes.
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  • In Copyright
Advisor
  • Swanstrom, Ronald
  • Baric, Ralph S.
  • Margolis, David
  • Garcia-Martinez, J. Victor
  • De Paris, Kristina
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2014
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  • Chapel Hill, NC
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