A Novel Prime/Pull Therapeutic Vaccine Strategy to Prevent Recurrent Genital Herpes

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PROJECT SUMMARY/ABSTRACT Genital herpes simplex type virus-2 (HSV-2) infection affects over 60 million people in the U.S. and over 536 million worldwide. An FDA-approved genital herpes vaccine is currently unavailable. After primary infection of the vaginal mucocutaneous tissue (VMC), the virus spreads and establishes latency in sensory neurons of regional dorsal root ganglia (DRG). The virus reactivates sporadically from latency and sheds back in the genital tract, where it can cause severe recurrent lesions. Our long-term goal is to develop a therapeutic vaccine to prevent recurrent genital herpes. Over the last 5 years, we have made significant progress in identifying candidate HSV-2 antigens and characterizing the phenotype and function of antiviral CD4+ and CD8+ T cells that associate with protection in seropositive women and in the guinea pig recurrent genital herpes model: (A) We found that two HSV-2 tegument virion proteins (VP16 and VP22) and two ribonucleotide reductase subunit proteins, (RR1 and RR2) are mainly targeted by CD4+ and CD8+ T cells from “naturally” protected asymptomatic women (those who, despite being infected, never develop recurrent genital herpes); (B) Similarly, VP16, VP22, RR1, and RR2 proteins were the main HSV-2 antigens recognized by tissue-resident CD4+ and CD8+ T cells that reside in DRG and VMC of protected asymptomatic guinea pigs; (C) Phenotypic and transcriptomic RNA- Seq profiling of DRG- and healed VMC-resident CD4+ and CD8+ T cells in protected guinea pigs show that they bear all the hallmarks of functional tissue-resident CXCR3+CD4+ and CXCR3+CD8+ T cells; (D) While therapeutic vaccination with RR2 antigen produced strong protection in HSV-2 infected guinea pigs, the VP16, VP22 and RR1 antigens provided modest protection; and (E) Treatment of HSV-2 infected guinea pigs with a neurotropic adeno-associated virus vector (AAV8) expressing the guinea pig CXCL11 chemokine (a CXCR3 ligand) boosted the number of CD4+ and CD8+ T cells specifically in infected DRG and VMC and improved protection. Based on these published and preliminary results, we hypothesize that boosting strong and long-lasting antiviral tissue- resident CD4+ and CD8+ T cell responses locally in DRG and VMC would produce a more robust/sustained protection against HSV-2 reactivation and shedding and reduce recurrent genital herpes. To test this hypothesis, we propose two Specific Aims: Aim 1. To evaluate the safety and protective efficacy, in the guinea pig genital herpes model, of an innovative prime/pull therapeutic vaccine approach that consists of: (1) Priming T cells with VP16, VP22, RR1, and RR2 antigens; and (2) “Pulling” primed T cells into infected DRG and VMC tissues by a local delivery of T-cell attracting chemokines, CXCL9, CXCL10 and/or CXCL11, using a neurotropic AAV8 vector. Aim 2. To determine whether increasing the number and function of antiviral tissue-resident CD4+ and CD8+ T cells within: (1) DRG (central neuronal immunity); and (2) VMC (peripheral epithelial immunity) correlates with protection against genital herpes. The goal of this pre-clinical study is to bring a prime/pull vaccine to clinic.