Lisa N. Akhtar, Ph.D. - US grants

DESCRIPTION (provided by applicant): HIV Associated Dementia (HAD) is a strikingly debilitating neurological consequence of HIV infection. Although its cause is still unclear, it is thought that HIV replication within immune cells of the Central Nervous System (CMS) results in their dysfunction, leading indirectly to neuronal death. While Interferon (IFN) (3, a cytokine mediator of the innate immune response in the brain, has been shown to be effective at preventing HIV replication, the effect is transient. HIV is eventually able to overcome its antiviral effects and resume replication, an event which heralds progression to HAD. Therefore, it is critical that the mechanism by which HIV evades this protective immune response be determined. Recently, numerous viral and bacterial pathogens, including HIV, have been shown to induce the expression of a family of negative regulators of cytokine function, the Suppressors Of Cytokine Signaling (SOCS). The goal of this proposal is to determine whether SOCS protein expression in the HIV-infected brain mediates the loss of IFN(3's ability to suppress HIV replication, and therefore promotes progression to HAD. First, it must be determined whether SOCS expression occurs in the HIV-infected brain. This will be examined in vivo by evaluation of SOCS protein expression in post-mortem HAD brain tissue. In addition, HIV Tat-treatment of CNS-relevant primary human and murine cells will be used in vitro to determine the mechanism of SOCS induction. Second, it must be determined whether SOCS protein expression functions to inhibit IFN(3 signaling, and thereby promote HIV replication in the brain. IFN0 signaling will be examined in vitro, in primary human and murine cells, at the level of STAT phosphorylation, target gene induction, and inhibition of HIV replication. The effect of both SOCS protein overexpression and deficiency will be evaluated to determine whether SOCS expression is sufficient to mediate inhibition of IFN(3's antiviral response. These studies will provide novel insight into the mechanism by which HIV is able to evade the innate immune system in the CNS. PUBLIC HEALTH RELEVANCE: This work seeks to determine whether HIV replication in the brain, and therefore progression to HIV Associated Dementia (HAD), is aided by Suppressor Of Cytokine Signaling (SOCS) proteins. Defining the potential mechanism by which these proteins allows HIV to evade the brain's protective immune response will allow for the development of therapies to strengthen this defense.

Project Summary This proposal describes a five-year training plan for the development of an independent research career focused on the virus-host interactions that dictate susceptibility of the pediatric brain to infection. Specifically, the applicant strives to elucidate how viral genetic variation influences neurovirulence, both by altering viral function and inducing immune escape. The applicant is an attending Infectious Diseases physician at the Children's Hospital of Philadelphia (CHOP) with previous PhD training in basic neuroimmunology. The goals for this award are to develop and refine the essential skills that will be required for a successful career as an independent investigator, including expertise in sequencing and bioinformatic analysis of large genetic data sets, viral genome editing, and neurologically-relevant in vitro and in vivo models of viral infection. The mentors for this award include Dr. Matthew Weitzman, an internationally recognized leader in the field of virus-host interactions, and Dr. Dennis Kolson, a physician-scientist and expert in mechanisms of neurovirulence. To add depth and breadth to the scientific career guidance of the applicant, a scientific advisory committee is composed of scientists and physician-scientists from diverse and complementary fields. Dr. Akhtar will also benefit from the unparalleled resources and mentorship available at both CHOP and the University of Pennsylvania. The proposed research focuses on the role of viral genetic variability in determining the clinical manifestations of neonatal herpes simplex virus (HSV) disease, particularly the ability to infect the neonatal brain. HSV infection of the neonatal brain causes severe encephalitis and permanent neurologic deficits, but the factors that promote central nervous system (CNS) infection are not known. Recent studies show that substantial genetic variability exists within HSV genomes, but have not evaluated how these variations impact viral growth characteristics or human disease manifestations. Successful completion of the studies proposed will identify HSV genetic variations associated with neonatal CNS disease, determine their impact on viral spread between neurons, and their ability to alter progression to CNS infection. This will be accomplished by large-scale viral genomic sequencing to identify variations most frequently associated with CNS disease, followed by creation of mutant viruses to determine the individual impact of identified variations on viral spread between the simplified neuronal connections of in vitro chamber assays, and the complex neuronal circuits of the murine retina. The studies outlined in this proposal will provide the first insights into how variations in the neonatal HSV genome impact neurovirulence and the development of CNS disease.