Departmental Address
MMI - Room E5148
Research and Professional Experience
One area of research in my laboratory is to understand the molecular mechanisms of HIV-1 pathogenesis. It is known that people infected with HIV-1 can have dramatically different outcomes. Some infected people develop AIDS quickly while others remain asymptomatic for years. Although the host immune response may account for the observed differences, evidence suggests that properties of HIV-1 area also responsible. Persons who acquire the virus from sick people also develop disease quickly, whereas others who acquire the virus from people who have remained healthy for years also stay healthy for 7-10 years. Recently, we have identified regions in the Env protein of HIV-1 gp120 that affect the cytopathogenicity of different HIV-1 strains. Although the viruses replicated efficiently in primary CD4+ T lymphocytes, certain viruses did not kill these cells, while others did. Experiments will be carried out to determine the mechanism of CD4+ cell killing and gp120 sequence variations. Since some of these regions of gp120 also induce neutralization antibodies, our study will generate useful information for the design of an effective HIV vaccine.
Another goal of our research is to study the mechanism of HIV assembly and entry, using biochemical, genetic, cellular and molecular biological techniques. Present studies have concentrated on the mechanism of packaging of various viral proteins (including Gag, Env and regulatory proteins) into mature HIV virions and the function of these proteins in virus entry. Genetic studies have revealed that the matrix protein and transmembrane protein are important for the incorporation of viral Env proteins into mature HIV-1 virions and for virus infectivity. Further studies will concentrate on tGag and Env protein intracellular targeting and interaction. Assembly of HIV virions requires correct targeting of viral structural proteins Gag, Pol, Env, and regulatory proteins Vpr and/or Vpx to the site of virus budding. These processes involve interactions between different viral and cellular proteins which are the fundamental issues of cell biology. Our studies will identify new targets for design of anti-HIV inhibition.
An understanding of the mechanisms by which effective cytotoxic T lymphocytes (CTL) can be elicited against internal virion proteins of HIV-1 such as Gag and Pol is essential to the development of a safe and effective HIV vaccine. This is because antibodies to these internal virion proteins will have little effect on the neutralization of HIV-1 virions. On the other hand, effective CTL response to these viral proteins will eliminate virus-infected cells, therefore preventing the spread of virus infection. To induce effective CTL responses, these viral proteins have to be Endogenously synthesized. This can be achieved by using live-attenuated virus, virus expression vector such as vaccinia, or DNA vaccines. DNA vaccines represent a novel means of expressing antigens in vivo for the generation of host immune responses, particularly CTL. Unfortunately, expression of HIV-1 Gag protein has been hampered by the stringent requirement of co-expression with other viral components, such as Rev and RRE. Furthermore, even with Rev and RRE, expression of HIV-1 Gag is negligible in Murine cells. These problems have limited our ability to address a key issue of how to generate effective CTL response to Gag using a mouse model. In order to overcome this problem, we have constructed a novel DNA expression vector and a recombinant Sindbis vector, which enables us to express Gag protein in a Rev and RRE independent and species independent fashion. More importantly, these strategies will allow us to systematically evaluate the expression of different forms of HIV-1 Gag and the immune responses against these Gag molecules in the Murine system.
Keywords
Molecular Microbiology and Immunology, molecular mechanisms of HIV-1 pathogenesis. It is known that people infected with HIV-1 can have dramatically different outcomes
Selected Publications
Vaccine related:
Qiu JT, Dettenhofer M, Tian C, August T, Pavlakis G, Yu XF. Evaluation of Novel HIV-1 Gag DNA Vaccines for Protein Expression in Mammalian Cells and the Induction of Immune Responses. J. Virol. 73: 9145-9152 (1999).
Qiu JT, Liu B, Chunjuan Tian, George N. Pavlakis, and Xiao-Fang Yu. Enhancing primary and secondary cellular immune responses against HIV-1 Gag by DNA expression vectors that target Gag antigen to different cellular compartments. J. Virol. 74:5997-6005 (2000).
Sucheep Piyasirisilp, Francine E. McCutchan, Jean K. Carr, Eric Sanders-Buell, Deborah Birx, Wei Liu, Jie Chen, Ralf Wagner, Hans Wolf, Yiming Shao, Shenghan Lai, Chris Beyrer and Yu XF. Recent outbreak of HIV-1 infection in southern China was initiated by two highly homogeneous, geographically separated HIV-1 strains: circulating recombinant form AE and a novel BC recombinant. J. Virol. 74:11286-11295 (2000).
Wei Kong, Chunjuan Tian, Bindong Liu, and Xiao-Fang Yu. Stable expression of primary HIV-1 structural gene products by a noncytopathic sindbis virus vector. J. Virol. 76:11434-11439 (2002).
Basic HIV Virology:
Dettenhofer M, Yu XF. Proline Mutations in HIV-1 p6Gag Reveal a Cell Type-Dependent Defect in the Retention of Pol Proteins and Membrane Closure in Virions. J. Virol. 73: 4696-4704 (1999).
Lee YM, Liu B, Yu XF. Formation of Virus Assembly Intermediate Complexes in the Cytoplasm and Their Association with Membranes by the Wild-Type and Assembly-Defective Mutant HIV-1. J. Virol. 73: 5654-5662 (1999).
Markus Dettenhofer, Shan Cen, Bradley A. Carlson, Lawrence Kleiman, and Yu XF. HIV-1 Vif, a regulator of RNA structure and its role in Reverse Transcription. J. Virol. 74:8938-8945 (2000).
Markus Dettenhofer and Yu XF. Characterization of the biosynthesis of HIV-1 Env from infected T-cells and the Effects of Glucose Trimming of Env on Virion Infectivity. J. Biol. Chem. 276:5985-5991 (2001)
