PROJECT SUMMARY Human herpes simplex virus 2 (HSV-2) is a sexually transmitted pathogen affecting 500 million people worldwide. Most of the global burden of HSV-2 disease results from the virus’s ability to establish chronic infections, characterized by recurrent anogenital ulcerative disease. The severity of symptoms experienced by those with chronic HSV-2 infection is highly variable, a feature of the disease which remains unexplained. While prior research has focused primarily on the role of the host in mediating the severity of chronic HSV-2 infection, evidence from studies both in animal models and humans suggests that the virus may also play an important role. The objective of this proposal is to improve our understanding of the pathogenesis of chronic HSV-2 infection by investigating the impact of viral factors on the severity of symptoms experienced by infected persons. The proposal consists of three aims. In Aim 1, Dr. Casto will perform a genotype-phenotype association study to scan the HSV-2 genome for genetic variants that are associated with disease severity. This aim will use genome sequence data for 100 HSV-2 samples from individuals with severe HSV-2 disease (cases) and for 100 samples from individuals with mild disease (controls). Some genetically-mediated traits are determined by many variants each with small effect. Such variants can be difficult to identify in genotype- phenotype association studies, so Dr. Casto will also assess for other intrinsic differences among HSV-2 samples that correspond to disease severity. In Aim 2, she will assess for differences in viral gene expression that are associated with disease severity by comparing the abundance of individual viral transcripts between viruses from cases and from controls grown in vitro. She will also compare viral transcript abundance in biopsies of HSV-2 lesions from cases and controls. In Aim 3, she will assess whether viruses from cases cause more severe disease in an animal model than viruses from controls. The results of this work will provide the first insights into the role of viral factors in determining the severity of chronic HSV-2 disease, insights that will help dictate the future direction of research in this field. Dr. Casto is an Acting Instructor/Senior Fellow Trainee in the Division of Allergy and Infectious Diseases at the University of Washington. She and her mentors have devised a comprehensive career development plan that includes: 1) Regular meetings with mentors to discuss research progress and career development; 2) Acquisition of the skills needed to perform in vitro and in vivo experiments with HSV; 3) Focused coursework that augments Dr. Casto’s skills in biostatistics, bioinformatics, and data analysis; 4) Attendance of seminars and workshops to develop Dr. Casto’s abilities in scientific communication and laboratory management; 5) Participation in local, national, and international conferences which will allow Dr. Casto to present her research...