DNA Damage and NK cell recognition of HIV-infected cells

Frederic Delebecque, UC Berkeley

HIV has infected more than 60 million people worldwide ands has led to more than 23 million deaths. At present, there are about 40 million people who are living with HIV infection, and there were 5 million new infections in 2004. As part of the innate immune system, natural killer (NK) cells might have an important role in host defense against HIV infection, as well as in the control of HIV replication in vivo. In this regard, it is important to understand how NK cells and HIV interact. Recent studies demonstrate that an important class of proteins that stimulate NK cells, called NKG2D ligands, are upregulated in cells infected with certain viruses and other pathogens, as well as in tumor cells. The NKG2D ligands bind to the NKG2D stimulatory receptor expressed by NK cells and some T cells. In tumor cells, expression of these ligands has been shown to be a consequence of the activation of the DNA damage response pathway. Other studies show that HIV can activate the DNA damage pathway as a result of the action of viral proteins, such as viral protein R (VPR) and integrase (IN). Therefore, induction of the DNA damage response by HIV VPR and IN may play a role in sensitizing infected cells to attack by NK cells. Using wildtype and mutant HIV-1, as well as retroviral vectors that direct the expression of VPR and IN, we propose to determine the role of VPR, IN and the DNA damage response in upregulating NKG2D ligands in cells infected with HIV-1. To assess the role of the DNA damage response, various steps in the DNA damage pathway will be blocked in fibroblasts before infecting the cells. The ATM (ataxia telangiectasia mutated) and ATR (ATM- and Rad3-related) protein kinases or two downstream transducer proteins in the pathway, Chk1 and Chk2, will be inhibited with specific siRNAs or pharmacological inhibitors. Upregulation of ligands at the mRNA level and at the cell surface, and sensitivity to NK cells will be assessed.

The long-term aim of this project is to identify how proteins, made as a result of a major stress-pathway, can enhance NK cell responses to HIV-1, and how such knowledge can be used to develop therapies to reduce the development of AIDS.