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Faculty
Research InterestsHIV establishes a chronic infection, and leads inexorably to the development of AIDS despite the acquisition of an anti-HIV immune response. My laboratory is interested in understanding the factors that allow HIV to thwart the immune system. Thus far, we have found that HIV evades the cytotoxic T lymphocyte (CTL) arm of the immune response by limiting presentation of viral antigens. This is accomplished by downmodulating MHC-I protein, which is required for immune recognition. Downmodulation of MHC-I occurs through the action of the HIV Nef protein. Work from our laboratory has indicated that the HIV Nef protein downmodulates MHC-I by physically interacting with specific amino acid sequences located in the MHC-I cytoplasmic tail. The specificity of this interaction allows Nef to selectively downmodulate MHC-I allotypes important for CTL recognition, while maintaining the expression of MHC-I allotypes that protect cells from natural killer cell recognition. Once bound, Nef allows the transport of MHC-I molecules into the Golgi apparatus, but then prevents their expression on the cell surface. As a result, MHC-I accumulates in the trans-Golgi network of Nef-expressing cells. We have also learned that the effects of Nef are cell-type-specific in that Nef is much more active in T cells, a natural target for HIV infection. This observation is important because current models derived from non-T cell systems, have led to the incorrect conclusion that Nef functions exclusively by accelerating MHC-I enodocytosis. Thus, our studies have uncovered a key, previously overlooked mechanism for MHC-I downmodulation and immune evasion by HIV. In addition, we have found that HIV limits antigen expression through the action of HIV Rev. The Rev protein normally functions by allowing late gene product mRNAs to exit the nucleus. Thus, the amount of Rev activity in the cell determines the relative amount of late gene product expression, the main source of CTL antigens. We have found that naturally occurring Rev alleles vary in their activity level and that those with less activity result in infected cells that are resistant to CTL lysis. These alleles are selected early in disease when the immune system is more active. Later on in disease, more active alleles emerge once the immune system has been destroyed and selective pressure wanes. In sum, the combined effects of Nef and Rev dramatically limit antigen presentation early in HIV disease when HIV must combat a highly active anti-HIV immune response. Education5/85 B.A. Wellesley College, Wellesley, MA. 5/93 M.D., Ph.D. Johns Hopkins University School of Medicine, Postgraduate Training7/93-6/94 Intern, Internal Medicine 7/94-6/95 Resident, Internal Medicine 7/96-7/98 Research Fellow, Medicine 7/96-7/98 Postdoctoral Fellow, laboratory of Dr. David Baltimore Honors and AwardsCRC Press Freshman Chemistry Award for Achievement in Chemistry 1984 Phi Beta Kappa 1985 Medical Scientist Training Program Award 1982 1985 M.A. Cartland Shackford Medical Fellowship 1985 Wellesley College Trustee Scholar Award for Study in Medicine 1985 Wellesley College Durant Scholar 1985 B.A., Summa cum laude with departmental honors in Molecular Biology; Thesis: "Characterization of the Interleukin-1 Gene." 1993 Johns Hopkins' University Young Investigator's Certificate of Merit Research Award 1996-1997 Howard Hughes Medical Institute Postdoctoral Research Fellowship for Physicians 1997-2001 NIH Mentored Clinical Scientist Development Award 1998 Biomedical Scholars Program Award, University of Michigan 1998 Massachusetts Infectious Disease Society Maxwell Finland Young Investigator Award for Excellence in Research 1999 Pew Scholars Award Center For AIDS Research Development Award Plenary speaker, American Association of Immunology Symposium on Microbial Invasion 2003 Padykula Lecturer, Wellesley College, Wellesley, MA 2003 Plenary speaker, 2004 Keystone Symposia on Molecular Mechanisms of HIV Pathogenesis 2004 Chair of the plenary session, Nef Function, 2004 Keystone Symposia on Molecular Mechanisms Recent PublicationsCollins, K.L., Chen, B.K., Kalams, S.A., Walker, B.D., Baltimore, D. (1998). The HIV-1 Nef protein protects infected primary human cells from CTLs. Nature, 391:397-401. Collins, K.L. and Nabel G.J., (1999). Naturally attenuated HIV strains: lessons for AIDS vaccines and treatments. N Engl J Med, 340; 1756-1757. Collins, K.L. and Baltimore, D. (1999). HIV's evasion of the cellular immune response. Immunologic Reviews, 168. Swann, S.A., Williams, M., Story, C.M., Bobbitt, K. R., Keesler, R., Collins, K.L. (2001). HIV-1 Nef blocks transport of MHC class I antigens to the cell surface via a PI 3-kinase-dependent pathway. Virology, 282, 267-277. Paulson, E., Tran, C., Collins, K., Fruh, K., (2001) KSHV-K5 inhibits phosphorylation of the Major Histocompatibility Complex class I cytoplasmic tail. Virology, 288, 369-378. Collins, K.L., (2002) Retroviral Reviews, Trends in Immunology, 23 (2), 111. Williams, M., Roethe, J., Kasper, M.R., Fleis, R., Przybycin, C.G., Collins, K.L., (2002) Direct binding of HIV-1 Nef to the MHC-I cytoplasmic tail disrupts MHC-I trafficking, J. Virol. 76 (23); 12173-12184. Fleis, R., Filzen, T. and Collins, K.L., (2002) Species-specific effects of HIV-1 Nef-mediated MHC-I downmodulation, Virology, 303; 120-129. Collins,K. L. (2002) How HIV evades CTL recognition, Current HIV Research, 1; 31-41. Kasper, M.R., and Collins, K.L., (2003) Nef-mediated disruption of MHC-I transport to the cell surface in T cells, J. Virol., 77 (5) 3041-3049. Bobbitt, K.R., Addo, M.M, Altfeld, M., Filzen, T., Onafuwa, A.A., Walker, B.D. and Collins, K.L., (2003) Rev activity determines sensitivity of HIV-infected primary T cells to anti-Gag CTL killing, Immunity, 18 (2) 289-299. (highlighted in Nature Reviews Immunology 3, (2003; 266-267). Collins, K.L., (2004) Resistance of HIV-infected cells to cytotoxic T lymphocytes. Microbes Infect 5; 494-500. Roeth, J.F., Kasper, M.R., Williams, M., Filzen, T.F., and Collins, K. L., (2004) HIV-1 Nef re-directs MHC-I from the TGN to lysosomes by stabilizing an interaction between MHC-I and AP-1. J Cell Biol 167(5); 903-13. Williams, M., Roeth, J.F., and Collins, K.L., (2005) HIV-1 Nef domains required for disruption of MHC-I trafficking are also necessary for co-precipitation of Nef with HLA-A2. J Virol 79(1); 632-6. Kasper, M.R., Williams, M., Xie, D., Fleis, R. and Collins, K.L., (2005) HIV-1 Nef disrupts viral antigen presentation early in the secretory pathway by preferentially binding hypo-phosphorylated MHC-I cytoplasmic tails. J Biol Chem 280(13): 121840-12848. Thammavongsa, V., Raghuraman, G., Filzen, T.M., Collins, K.L. and Raghavan, M. (2006) HLA-B44 polymorphisms at position 116 of the heavy chain influence TAP complex binding via an effect on peptide occupancy. J Immunol 177(5): 3150-3161. Wonderlich ER, Williams M, Collins KL.
The tyrosine binding pocket in the adaptor protein 1 (AP-1) mu1 subunit is
necessary for Nef to recruit AP-1 to the major histocompatibility complex class I Schaefer MR, Williams M, Kulpa DA, Blakely PK, Yaffee AQ, Collins KL.
A Novel Trafficking Signal within the HLA-C Cytoplasmic Tail Allows Regulated
Expression upon Differentiation of Macrophages.
Lab Projects By mechanisms that are not well understood, HIV is able to evade the cytolytic T cell (CTL) arm of the immune system. Escape from the CTL response allows persistent infection and contributes significantly to disease progression. A clear understanding of the means by which the virus accomplishes this would allow the development of novel antiviral therapies. We have explored the possibility that HIV encodes a factor that protects infected cells from CTLs. To accomplish this, we developed a flow cytometric technique for detecting cell killing that was sensitive enough to detect the minority of living HIV-infected cells amongst a mixed population. This methodology employed an HIV molecular clone that encoded a marker protein (placental alkaline phosphatase, PLAP) in its genome. Infected cells were distinguished by the expression of PLAP on their surface. Killed cells were distinguished from live cells by their flow cytometric light scatter parameters and by their differential permeability to fluorescent dyes. We used this assay to demonstrate that cells infected with an HIV-1 encoding a mutant nef gene were readily recognized and killed by anti-HIV CTL clones. However, HIV-infected cells expressing the nef gene were resistant to CTL-mediated lysis. A monoclonal antibody specific to MHC class I HLA-A2 revealed that expression of a functional nef gene resulted in a dramatic decrease in MHC class I HLA-A2 antigens on primary T cells. Those infected cells that had maximally downregulated MHC class I were most resistant to CTLs. The protective effect of nef could be reversed by exogenously adding an excess of specific peptide epitope. This demonstrated that protection was achieved via a reduced density of viral peptide epitope secondary to a reduction in MHC class I levels. Exogenous antigen reversed the effects of Nef by binding to residual MHC class I antigens on the cell surface and sensitizing the cell CTL killing. Thus we have learned that HIV Nef functions by reducing the density of MHC class I-epitope complexes on the infected cell surface and thereby protecting it from CTL recognition. Future experimentation will focus on determining whether other viral factors influence CTL recognition, determining the structural elements of Nef important for MHC class I downmodulation. Additional Lab LinksDepartment of Microbiology and Immunology Cellular and Molecular Biology Program Graduate Program in Immunology
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