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1. Molecular Mechanism of HIV-1 Infection of Resting CD4 T cells

A major current focus of my laboratory is on the molecular interaction of HIV-1 with human resting CD4 T cells. We are particularly interested in HIV-1 interaction with the chemokine co-receptor CXCR4 in mediating actin cytoskeletal rearrangement required for viral intracellular migration.

In the past, our studies have focused on several aspects of virus-CD4 T cell interaction at the cortical actin layer. We studied the effects of viral envelope signaling on the actin rearrangement of resting CD4 T cells. These studies led to the discovery that treatment of resting CD4 T cells with gp120 or HIV-1 triggers the polymerization and depolymerization of filamentous actin (F-actin) in the cortical region. We also identified cofilin as a molecular target of CXCR4 signaling triggered by HIV gp120 to promote the cortical actin dynamics. On the basis of our studies, we proposed a molecular model suggesting a direct involvement of the cortical actin and cofilin in viral latent infection of resting T cells (Figure 1) (1-2).

Figure 1. Model of chemokine signaling and actin dynamics in HIV infection of CD4+ T cells. (A and B) Engagement of viral gp120 with the receptor/co-receptor on CD4+ T cells results in activation of the Rac1-PAK-LIMK-Cofilin pathway and actin polymerization which transiently block receptor internalization to facilitate fusion. (C) Following entry of the viral core, the pre-integration complex (PIC) undergoes reverse transcription and nuclear migration possibly in association with actin. Nuclear migration is further facilitated by activation of cofilin and the Rac1-WAVE2-Arp2/3 pathway, which promotes actin treadmilling and pushes the viral PIC to the nucleus.

My laboratory will continue to focus on studying molecular details of how HIV interacts with the cortical actin cytoskeleton in human resting CD4 T cells. This is an important, yet largely unexplored research field. Although our previous studies have established a role of the cortical actin in HIV latent infection of resting T cells, the molecular mechanisms are currently not defined. Mapping these molecular events is fundamental to establishing a framework for understanding the early events in viral infection of CD4 T cells.

2. Pre-integration Transcription of HIV-1 DNA

In addition to studying HIV interaction with actin, my laboratory is currently also studying pre-integration transcription. In the past, we have demonstrated that pre-integration transcription is a normal process occurring during HIV-1 infection of CD4 T cells and macrophages (3-7). We are in the process of identifying the non-integrated, transcribing HIV DNA templates (Figure 2).

Figure 2. Pre-integration transcription of HIV-1. Viral transcription in the absence of integration generates all classes of viral transcripts, but only early proteins such as Tat, Rev, and Nef are synthesized at low levels. Tat and Nef can modulate cellular conditions. Viral replication does not occur without integration, but infection by a second virus can rescue the unintegrated viral genomes.

3. Development of a Rev-dependent Lentiviral Vector Targeting HIV-1 Infection

My laboratory has developed a Rev-dependent lentiviral vector to target HIV-infected macrophages and T cells, using a bacterial toxin, anthrolysin O from Bacillus anthracis (8-10). We are in the process of constructing a series of Rev-dependent vectors carrying a variety of bacterial toxins and human apoptotic genes to induce the decay of viral reservoirs in infected macrophages and T cells (Figure 3).

Figure 3. Fluorescent microscopy of GFP expression in macrophages infected with HIV-1 and the Rev-dependent GFP lentiviral vector. Cells were infected with HIV-1 (AD8) and then infected with the Rev-dependent lentivirus vNL-GFP-RRE-SA. Infected cells were examined with fluorescent microscopy. The left and right panels show the bright and green fluorescent fields of the same cells. Red arrows indicate an HIV-1-infected cell expressing the GFP-protein.

References

Yoder, A., D. Yu, L. Dong, S. R. Iyer, X. Xu, J. Kelly, J. Liu, W. Wang, P. J. Vorster, L. Agulto, D. A. Stephany, J. N. Cooper, J. W. Marsh and Y. Wu. 2008. HIV-1 envelope-CXCR4 interaction activates cofilin to overcome cortical actin restriction in resting CD4 T cells. Cell, 134:782-792.
Spear, M., J. Guo and Y. Wu. 2013. Novel anti-HIV therapeutics targeting chemokine receptors and actin regulatory pathways. Immunological Reviews, 256 (1), 300-312.
Wu, Y. and J. W. Marsh. 2001. Selective transcription and modulation of resting T cell activity by preintegrated HIV DNA. Science 293(5534), 1503-6.
Wu, Y. and J. W. Marsh. 2003. Early transcription from nonintegrated DNA in human immunodeficiency virus infection. J. Virol 77(19), 10376-10382.
Wu, Y. and J. Marsh. 2003. Gene transcription in HIV infection. Microbes and Infection 5,1023-27.
Wu, Y. 2004. HIV-1 gene expression: lessons from provirus and non-integrated DNA. Retrovirology 1:13 (highly accessed)
Kelly, J., H. Beddall, D. Yu, J. W. Marsh and Y. Wu. 2008. Human macrophages support persistent transcription from unintegrated HIV-1 DNA. Virology 372(2), 300-12.
Young, J., Z. Tang, Q. Yu, D. Yu, and Y. Wu. 2008. Selective killing of HIV-1-positive macrophages and T cells by a Rev-dependent lentivirus carrying anthrolysin O from Bacillus anthracis. Retrovirology 5:36 (highly accessed)
Wu, Y., M. H. Beddall and J. W. Marsh 2007. Rev-dependent indicator T cell line. Current HIV Research. 5(4), 394-402
Wu, Y., M. H. Beddall and J. W. Marsh. 2007. Rev-dependent expression vector. Retrovirology 4:12

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Department of Molecular and Microbiology
National Center for Biodefense & Infectious Diseases
George Mason University
10900 University Drive
Manassas, VA 20110

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