Velpandi Ayyavoo - US grants

DESCRIPTION: (Adapted from Applicant's Abstract) Development of a safe, effective and affordable vaccine for HIV-1 is potentially the most efficient means of controlling HIV-1 infection worldwide. However, the genetic and biological variability of HIV-1 represents significant obstacles for vaccine development. Recent evidence indicates that CTLs may play a role in clearing viremia during primary infection and maintaining a disease-free state in HIV-1-infected patients. Thus, efforts to develop an HIV vaccine should focus on eliciting a broad cross-reactive CTL response as one major component. One promising approach to generating an effective CTL response in vivo is through the use of DNA vaccination. Current efforts using HIV-1 env and gag/pol DNA constructs as immunogens suggest that additional vaccine components are needed to confer broad protection. Therefore, a putative HIV-1 vaccine might benefit by inclusion of additional immunogenic targets. In addition to the structural and enzymatic proteins, HIV-1 also contains regulatory and accessory genes. These genes are highly conserved in vivo and may provide additional targets for CTL responses. We hypothesize that such targets could induce a broad virus-specific CTL response that could help to limit viral escape and confer protection against viral challenge. To use the accessory genes as part of a multicomponent vaccine, we have engineered a novel construct that expresses HIV-1 accessory genes vif, vpu, and nef under the control of a single promoter. To test the "proof of concept" we propose the following aims: (1) We will immunize human HLA-A2 transgenic mouse and evaluate the cellular immune responses using HIV-1 infected human targets; (2) we will use a non-human primate model to test the ability of this vaccine construct to confer protection either alone or in combination with env and gag/pol vaccine constructs. We hypothesize that cell-mediated responses induced by the accessory genes may include broader recognition of divergent HIV-1 clades and should be useful in both prophylactic as well as therapeutic vaccination schemes against HIV-1.

DESCRIPTION (provided by applicant): The central objective of this project is to understand the role of Vpr in HIV-1 immunopathogenesis and disease progression. The Applicant proposes to evaluate the mechanisms of Vpr-mediated regulation of CD4+ T cell and macrophage responses, and to assess the possibility that Vpr modulates the in vivo immune response to viral infection. Specifically, the research team will: (1) investigate the direct effects of Vpr on antigen presenting cells and T cells in vitro; (2) determine the extent to which Vpr mediates immune dysregulation using an in vitro immunization model; (3) identify the domains of Vpr involved in mediating these immune functions using Vpr mutants. The proposed studies will lead to an understanding of how Vpr modulates basic cellular events in these important immune cell types and how it may regulate immune functions in vitro and in vivo.

DESCRIPTION (provided by applicant): HIV-1 associated neuropathogenesis is characterized by two distinct observations. The first concerns the notable cognitive and motor dysfunction in HIV-1 infected individuals. The second relates to the lack of infection of neurons by HIV-1. This suggests that the dementia in AIDS patients might be the result of a combination of both direct and indirect effects of HIV-1 encoded proteins (Env, Tat, Nef and Vpr) and host cellular factors. The mechanisms underlying the onset and progression of dementia are poorly understood. The goal of this application is to elucidate the contribution of HIV-1 Vpr to neuropathogenesis. In the infected individuals, Vpr is present in cell-associated, virion-associated and cell and virion-free forms. Further, the ability to traverse through cell membrane endows Vpr the potential to cause damage directly in uninfected bystanders such as neurons. Furthermore, Vpr is also known to indirectly dysregulate bystander cells through cellular factors released from infected target cells. Based on this, we hypothesize that Vpr has the potential to contribute to neuronal apoptosis and dysfunction. To elucidate the molecular events underlying dementia, we propose to analyze the effects of Vpr using appropriate human primary cells in culture as a model. To achieve these goals we propose to: (i) determine the mechanism(s) involved in Vpr mediated neuronal loss and dysfunction directly;(ii) identify the cellular cofactors and neuroinflammatory molecules differentially regulated by Vpr in target cells;and (iii) identify the structure-function relation of Vpr to neuropathogenesis using naturally occurring Vpr variants from CNS compartment. PUBLIC HEALTH RELEVANCE: Dramatic improvements in treating HIV-1 infected individuals have been attained with Highly Active Anti-Retroviral Therapy (HAART), and despite the availability of HAART, neurocognitive disorders affect 50-70% of the HIV-1 infected individuals. High incidence of HIV-Associated Dementia (HAD) is due to the neuronal dysfunction caused by the viral proteins as well as the inflammatory factors released by the infected cells into the local environment. Therefore, a combination therapy targeting both viral and neuroinflammatory factors would be desirable. This study focuses on understanding the role of viral and host cellular factors in neuropathogenesis toward identifying novel targets and designing new therapeutics against HIV-1 in the central nervous system.