The HSV-1 live attenuated VC2 vaccine provides protection against HSV-2 genital infection in the guinea pig model of genital herpes

Background

Although development of an HSV vaccine is a priority there is currently no vaccine available. The recent failure of subunit vaccines suggest that presentation of more antigens via a live attenuated vaccine may be required for protection. We therefore evaluated VC2, a live attenuated HSV vaccine, engineered to be unable to enter into neuronal axons.

Methods

VC2 pathogenesis was first evaluated in guinea pigs following intravaginal inoculation. VC2 was then evaluated as a prophylactic and therapeutic vaccine and compared protection to a gD2 vaccine adjuvanted with MPL/Alum in the guinea pig model of genital HSV-2. The guinea pig model allows evaluation of acute and recurrent disease, as well as vaginal shedding acutely and during episodes of recurrent activation.

Results

VC2 was significantly attenuated in guinea pigs compared to the wild type strain, 17syn+. It replicated poorly at the inoculation site, did not produce any genital disease and rarely infected the neural tissue. After prophylactic vaccination, the VC2 vaccine decreased the clinical severity of acute and recurrent HSV-2 disease and shedding and decreased the quantity of virus in the DRGs. When compared to gD2+MPL/Alum, VC2 was somewhat more effective especially as it relates to neural tissue infection. VC2 was not effective as a therapeutic vaccine.

Conclusion

The live attenuated prophylactic HSV vaccine, VC2, was effective in the guinea pig model of genital HSV-2. Its decreased ability to infect neural tissues provides advantages over other live attenuated vaccines.