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  • The Role of Nef in HIV Pathogenesis

    Faculty Involved:


    The major determinants of HIV pathogenesis leading to AIDS remain unclear.  However, a growing body of experimental evidence suggests that the HIV/SIV protein Nef plays a key role in virus-induced pathogenesis. Understanding the viral and cellular determinants underlying pathogenesis leading to AIDS is a critical step in finding new targets for therapy to slow or stop progression to AIDS.  

    For the past fourteen years, Dr. Vincent Bond’s lab in collaboration with Dr. Michael Powell’s lab has investigated the role played by extracellular Nef, secreted from HIV (or SIV/HIV-2) infected cells in exosomes (exNef), in pathogenesis leading to AIDS. This work has entailed molecular genetics, computation chemistry using supercomputer modeling, translational/ population studies involving patient plasma analysis, humanized mouse studies of infection with collaborators at University of California, Davis, and Emory CFAR Clinical Core, immunological analysis of human infection and nonhuman primate infections with collaborators at Emory/Yerkes Primate Center. A body of literature developed from this collaborative funded research has begun to uncover the detailed mechanism(s) by which the Nef protein is released from viral-infected cells in exosomal vesicles that result in, depending on the cell type, (i) activation-induced cell death, or (ii) gene dysregulation leading to unscheduled immune activation, both in bystander cells. These uncovered mechanisms are capable of leading to immune depletion/dysfunction causing pathogenesis leading to AIDS. 

    This research program has highlighted a potential new target for AIDS therapy, and at least one therapeutic peptide inhibitor. Additionally, understanding the role of mechanisms underlying the cellular secretion pathway in the HIV lifecycle will open new avenues of study into this basic and important cellular function, and into other disease processes (e.g., cancer).  

    Relevant HIV publications:

    1.  James, C.O., Huang, M-B., Khan, M., Garcia-Barrio, M., Powell, M.D., & Bond, V.C. 2004.  Extracellular Nef Protein Targets CD4+ T Cells for Apoptosis by Interacting with CXCR4 Surface Receptors.  JVI 78(6): 3099-3109. PMC353732
    2.  Huang, M-B., Jin, L., James, C.O., Khan, M., Powell, M.D., & Bond, V.C.  2004.  Characterization of Nef-CXCR4 interactions important for apoptosis induction.  JVI 78(20):  11084-11096. PMC521796
    3.  Huang, M-B., James, C.O., Powell, M.D., & Bond, V.C. 2008. Apoptotic Peptides Derived from HIV-1 Nef Induce Lymphocyte Depletion in Mice.  Ethnicity and Disease. 2008 Spring; 18(2 Supplement 2): S2-S7. PMC3218084
    4.  Campbell, T.D., Khan, M., Huang, M-B., Bond, V.C., & Powell, M.D. 2008.  HIV-1 Nef protein is secreted into Vesicles that can fuse with Target Cells and Virions. Ethnicity and Disease. 2008 Spring; 18(2 Supplement 2): S2-S9. NIHMS336460
    5. Ali, S.A., Huang, M-B., Campbell, P.E., Roth, W.W., Campbell, T., Khan, M., Newman, G., Villinger, F., Powell, M.D., & Bond, V.C.  2010. Genetic Characterization of HIV Type 1 Nef-Induced Vesicle Secretion. AIDS Res. Hum. Retro-viruses 26(2): 173-192. PMC2835390 
    6. Raymond, A.D., Campbell-Sims, T.C., Khan, M., Lang, M., Huang, M-B., Bond, V.C., & Powell, M.D. 2011. HIV-1 Nef is released from Infected Cells in CD45+ Microvesicles and is Present in the Plasma of HIV-infected Individuals.  AIDS Research and Human Retroviruses Feb; 27(2):167-78. PMC3064529
    7. Shelton, M.N., Huang, M-B., Ali, S.A., Powell, M.D., and Bond, V.C. 2012. SMR-derived peptide disrupts HIV-1 Nef’s interaction with mortalin and blocks virus and Nef exosome release. J Virol. Jan, 86(1): 406-19. PMC3255900.
    8. Campbell,P.E.; Isayev,O; Ali,S.A.; Roth,W.W.; Huang,M.-B.; Powell,M.D.; Leszczynski,J; Bond,V.C.. Validation of a Novel Secretory Modification Region (SMR) of HIV-1 Nef Using Cohort Sequence Analysis and Molecular Modeling. Journal of Molecular Modeling. 2012. Oct, 18(10): 4603-4613. PMC3469780.
    9.  Kalra,H., Simpson,R., Li,H., Aikawa,E., Altevogt,P., Askenase,P., Bond,V.C., Borras,F., Breakefield,X., et al. Vesiclepedia: A compendium for extracellular vesicles with continuous community annotation. 2012. PLOS Biology. December 2012; 10(12): e1001450. PMC3525526
    10.  Shelton,M.N., Huang, Ming B., Ali,S., Johnson, K., Roth, W., Powell,M., Bond, V.C. Peptide-based Identification of Functional Motifs and their Binding Partners. 2013. J. Vis. Exp. (76), e50362, doi:10.3791/50362.

    Relevant Cancer Publications:

    1. Bumpers, H.L., Huang, M-B., Powell, M., Grizzle, W.E., Lillard, J., Okoli, J., and Bond, V.C. Effects of HIV-1 nef, a cytotoxic viral protein, on the growth of primary colorectal cancer.  Cancer Biology and Therapy 4(1).
    2. Harrington III, W., Bond, V.C., Huang, M-B., Powell, M., Lillard, J., Manne, U., Bumpers, H. 2009. HIV nef-M1 effects on colorectal cancer growth in tumor induced spleens and hepatic metastasis. Mol Cell Pharm, 1(2): 85-91. PMC2851221
    3. Harvey Bumpers, Ming-Bo Huang, Venkat Katkoori, Manne Upender, Vincent Bond. Nef-M1, a CXCR4 Peptide Antagonist Enhances Apoptosis and Inhibits Primary Tumor Growth and Metastasis in Breast Cancer.  (2013). Journal of Cancer Therapy 4(4): 896-906.

    Relevant Patents:

    Full Patents
    1. Tumor Cytotoxicity Induced by Modulators of the CXCR4 Receptor. USP 7,312,305.  This invention relates to the use of HIV-1-, HIV-2-, SIV- or FIV- associated gp120 molecules as therapeutic agents against epithelial carcinomas.  12/25/2007.

    2. Modulating Vaccine against HIV-1 Nef Protein Induced Lymphocyte Depletion.  2011.  USP 7,943,139.  This invention relates to the use of identified apoptotic motif sequences in HIV Nef as targets for a vaccine that would block Nef apoptotic motif driven pathogenesis.

    3. Method for Treating AIDS or Cancer by Inhibiting the Secretion of Microparticles. 04/30/2013. USP 8,431,530; continuation patent: 07/02/2013, USP 8,476,237. Relates to the medical treatment and, in particular, to a method for treating AIDS or cancer by inhibiting the secretion of microparticles. Continuation Patent Application 13/693,507 (1013-168); Continuation Patent Application 13/621,597 (1013-161)

    Patent Application
    1. Antimicrobial Compositions and Methods of Use Thereof.  Utility Patent Application No. 13/267,977 (2011). Relates to the medical treatment and, in particular, to antimicrobial compositions and method for treating microbial infections.

    2. Compositions and Methods for Exosome Targeted Expression.  13/327,244. 2011. Relates to methods of producing exosomes and exosome targeted expression of fusion proteins with predefined sequence of interest for therapeutic and diagnostic uses.

    Other Relevant Items:

    1. From Journal of Video Experimentation: Employing techniques, developed by the Nef Pathogenesis group and described in this video, which utilize the unique properties of specific short peptides derived from motifs found in full-length proteins, one may accelerate the identification of functional motifs in proteins and the development of peptide-based inhibitors.

    2. Your Health Connection is a resource for you, designed to help you find good health outcomes.  The program is produced by WCLK and the Center for Cancer Research and Therapeutic Development at Clark Atlanta University. Your Health Connection takes a look at HIV-AIDS and the cancers often associated with the disease.

    Nef Involvement in HIVAN

    Faculty Involved:

    HIV-associated nephropathy (HIVAN) is a kidney disease affecting predominantly African Americans (AA) who can progress to end stage renal failure. The exact cause of the disease is unknown. We found that endothelin-1 (ET-1), implicated in renal and cardiovascular disease, was increased in plasma from both HIVAN and African American HIV+ patients and was associated with a single nucleotide polymorphism, Lys198Asn, in the endothelin-1 gene (p=0.001). In addition, preproendothelin-1 (ppET-1) and endothelin converting enzyme-1 (ECE-1) mRNA expressions were up-regulated in HIVAN and AA HIV + patients. ppET-1 is proteolytically cleaved into big ET-1 which is then converted to the active ET-1 peptide by ECE-1. An increase in either ppET-1 or ECE-1 could lead to increased ET-1 levels observed in HIVAN patients. Renal biopsies from HIVAN patients stained positive for endothelin-1 indicating the presence of the peptide in the kidneys of these patients.

    Peripheral blood derived macrophages from HIVAN patients stimulated with HIV Nef for 4 hours significantly increased ECE-1 mRNA when compared to the Nef-induced ECE-1 mRNA by cells from healthy donors and other HIV + patients (P<0.03 and P<0.01 respectively)(fig 3). In addition, Nef treatment significantly increased ECE-1 mRNA in macrophages from AA HIV + donors when compared to cells from healthy donors and other HIV + donors (P<0.006 and P<0.001 respectively). HIV gp120 did not induce any detectable ECE-1 mRNA from any of the donor's cells. Further, we found that macrophages from HIVAN and AA HIV+ patients treated with Nef or LPS displayed significantly higher expression of ppET-1 mRNA when compared to cells from healthy donors or other HIV + patients macrophages treated with either Nef or LPS (P<0.01 for both)( fig 4). HIV Nef treatment induced a significantly higher amount of ppET-1 mRNA from HIVAN donors when compared to other HIV+ patients (5.6 copies/106 copies 18S rRNA and 1.0 copies, respectively; P<0.05). No significant differences were observed in ppET-1 expression when cells were treated with HIV-1 gp120.

    Thus, this evidence suggests (i) ET-1 plays a role in the pathogenesis of HIV-associated nephropathy, and (ii) an endothelin-1 polymorphism may predispose HIV infected African Americans to the development of renal disease. Further, and most significantly to the relationship between these projects, (iii) the evidence points to HIV Nef protein as the stimulus of increased expression of ppET-1 and ECE-1 in a subpopulation of African-Americans. As mentioned above, an increase in either ppET-1 or ECE-1 could lead to increased ET-1 levels observed in HIVAN patients. And increased ET-1 has already been shown to be implicated in renal and cardiovascular disease in non-HIV infected patients.