Institute for Clinical and Translational Science

Targeting the mucosal immune system of the genital tract (GT) with subunit vaccines failed to induce potent and durable local CD8⁺ T cell immunity, crucial for protection against many sexually transmitted viral (STV) pathogens, including herpes simplex virus type 2 (HSV-2) that causes genital herpes. In this study, we aimed to investigate the potential of a novel lipopeptide/adenovirus type 5 (Lipo/rAdv5) prime/boost mucosal vaccine for induction of CD8⁺ T cell immunity to protect the female genital tract from herpes. The lipopeptide and the rAdv5 vaccine express the immunodominant HSV-2 CD8⁺ T cell epitope (gB_498-505) and both were delivered intravaginally (IVAG) in the progesterone-induced B6 mouse model of genital herpes. Compared to its homologous lipopeptide/lipopeptide (Lipo/Lipo); the Lipo/rAdv5 prime/boost immunized mice: (i) developed potent and sustained HSV-specific CD8⁺ T cells, detected in both the GT draining nodes (GT-DLN) and in the vaginal mucosa (VM); (ii) had significantly lower virus titers; (iii) had decreased overt signs of genital herpes disease; and (iv) did not succumb to lethal infection (p < 0.005), following intravaginal HSV-2 challenge. Polyfunctional CD8⁺ T cells, producing IFN-γ, TNF-α and IL-2 and exhibiting cytotoxic activity, were associated with protection (p < 0.005). The protective CD8⁺ T cell response was significantly compromised in the absence of the adaptor myeloid differentiation factor 88 (MyD88) (p = 0.0001). Taken together, these findings indicate that targeting the VM with a Lipo/rAdv5 prime/boost vaccine elicits a potent, MyD88-dependent, and long-lasting mucosal CD8⁺ T cell protective immunity against sexually transmitted herpes infection and disease.