The Impact of Natural Sequence Variation in HSV-2 Gamma 34.5 on Neurovirulence

PROJECT SUMMARY Approximately 14,000 neonates are infected with herpes simplex virus (HSV) each year. In stark contrast to adult HSV infections, which are typically asymptomatic or limited to recurrent lesions at mucosal surfaces, more than half of infected neonates experience an invasive infection of the central nervous system. These infections typically cause encephalitis and parenchymal damage, leading to a high risk of permanent neurodevelopmental deficits or immediate death. The factors that drive severe HSV neurological infections in neonates remain poorly understood. While adults can be predisposed to HSV encephalitis due to host innate immune defects, such defects do not explain neonatal disease. This critical gap in our knowledge presents a barrier to the development of effective therapies that protect the neonatal brain. Thus, the overarching goal is to determine the viral factors that promote severe HSV neurological infections in human neonates. Recently, an unbiased analysis of clinical HSV-2 genomes revealed two sequence variations of interest in the 34.5 gene that correlate with neurovirulence. These sequence variations in 34.5 are unique to clinical isolates that cause the most severe neurological disease both in human neonates and murine models of encephalitis. The goal of this proposal is to determine how natural variations in the HSV-2 34.5 gene contribute to neurovirulence and neurological disease outcomes in neonates. The central hypothesis is that 34.5 sequence variation impacts the ability of HSV-2 ICP34.5 and  isoforms to bind host immune proteins, and thereby impacts neurovirulence in vivo. Aim 1 will identify binding partners of the HSV-2 ICP34.5 and  isoforms, and will elucidate how natural amino acid sequence variation in these proteins impacts their ability to bind host targets in neurons. These findings are expected to uncover key host proteins underlying the innate and adaptive immune responses to HSV-2 infection in the neonatal brain. In Aim 2, mutant HSV-2 viruses will be constructed to determine the impact of natural 34.5 sequence variation on neurovirulence in mice. Successful completion of these Aims will bridge a crucial gap in the mechanistic understanding of HSV-2 neurological infections in neonates. The findings of this study will help to guide the development of novel therapies that prevent permanent damage to the neonatal brain. These Aims will serve as a framework for a three-year training plan designed to provide Mr. Miller with expertise in in vitro and in vivo models of viral neurovirulence, and tools for viral manipulation and mutagenesis. The mentors for this award include Dr. Lisa Akhtar, a physician-scientist and expert in human neurological infections and animal models of encephalitis, and Dr. Greg Smith, an internationally recognized leader in neurovirulence, mutagenesis, and vaccine development. This complementary team will be fully dedicated to developing Mr. Miller’s (1) foundational knowledge, (2) laboratory and data analysis skills, (3) scientific communication skills, and (4) mentoring skills which will be essential to his development into a future leader in neurovirology. Mr. Miller will also benefit from the unparalleled resources and mentorship available at Northwestern University.