| | |

David A. Leib, Ph.D.

Contact Information:

Professional Interests:

Since its establishment in 1990 my laboratory has studied the pathogenesis and biology of herpes simplex virus (HSV) with an emphasis on studying the interface of the virus and the host. The generation and use of recombinant viruses in a variety of models of infection followed by analysis with functional genomics and cytokine arrays has allowed us to determine the roles of viral and host factors in the outcome of infection. We have developed a number of reagents, techniques, and approaches. These include BACs to rapidly generate recombinant viruses, non-invasive bioluminescence technology to monitor spread and tropism of HSV in real time, and recombinant viruses that are effective as therapeutic vaccines for prevention of recurrent HSV infections (US Patent #5698431). We have also discovered roles for a number of viral genes in the evasion of innate and adaptive immunity, and of autophagy responses, and elucidated roles for host resistance pathways in the control of acute infection.

Herpes simplex virus is a common ocular pathogen causing a variety of diseases ranging from self-limiting dendritic epithelial keratitis, conjunctivitis, and blepharitis to necrotizing stromal keratitis. HSV exhibits two different modes of gene expression during its life cycle. During the replicative phase of infection all of its genes are expressed. During latency, however, viral gene expression is almost completely repressed. Our approach is to manipulate cloned viral genes and then introduce engineered mutations into the viral genome to generate recombinant viruses. We then use these recombinant viruses in vitro and in vivo to allow the study of viral pathogenesis at the molecular level.

VIRION HOST SHUTOFF (VHS), INNATE IMMUNITY AND VIRAL TROPISM
HSV rapidly shuts off protein synthesis in infected cells in part through the virion host shutoff protein or vhs. Vhs is a ribonuclease, inducing rapid destabilization of host mRNAs. We have demonstrated that vhs activity determines the outcome of infection in vivo by virtue of its ability to degrade viral dsRNA, to alter innate immune function, and to promote viral replication in vivo. Our ongoing work is determining how alterations in viral RNA turnover modulated by vhs affect double-stranded RNA sensing, and thereby the induction of the innate immune response. We are using functional genomic analysis in vivo and in vitro to determine the contribution of vhs to the specific alteration of host gene expression and elucidating the structural determinants that govern the immunomodulatory activity of vhs. Finally, using our real-time bioluminescent approaches, we are showing that the tropism of HSV is strongly shaped by innate immunity, with certain pathways being necessary for protection of the CNS, and others for prevention of generalized hematogenous spread.

INTERFACE BETWEEN HSV, XENOPHAGY, AND IMMUNITY
Autophagy is a constitutive cellular process in which cytoplasmic components are sequestered and degraded by the lysosome to generate metabolic precursors, to remove damaged organelles and altered intracellular components. If the autophagic vacuole also engulfs and destroys invading pathogens, the process is known as xenophagy. Three important aspects of the pathogenesis of HSV are being studied. First, we are determining the role of xenophagy in the pathogenesis of HSV-1. Second, we are exploring mechanisms by which viral genes subvert the host innate xenophagy and interferon (IFN)-mediated antiviral responses. Third, we are determining the impact of two HSV proteins on the regulation of xenophagy and antigen presentation. Our work is demonstrating that xenophagy is a critical process for the protection of the host from infection through both innate and adaptive immune responses, and that subversion of xenophagy is a pivotal determinant of HSV pathogenesis.

Grant Information:

Principal Investigator, NEI RO1 09083 “Viral and host factors in herpetic reactivation", Funded 1992-2013.

Principal Investigator, NEI RO1 10707 "HSV-induced RNA degradation in pathogenesis", Funded 1994-2014.