Could HSV-1 vaccine give immunity against genital HSV-2 infection?

 Herpes simplex virus (HSV) is categorized into 2 types: HSV-1 and HSV-2. HSV-1 is mainly transmitted orally and causes oral herpes (also known as “cold sores”) whereas HSV-2, a sexually transmitted virus, causes genital herpes. Both infections are fairly common and contagious but there is no vaccine available for either yet. There has been an ongoing effort to develop a HSV vaccine but none have come to fruition so far. To date, multiple approaches to developing a HSV vaccine have been taken including subunit, live attenuated, inactivated, DNA, disabled single-cycle and vectored vaccines. One big challenge has been the fact that attenuated HSV strains propagate poorly, eliciting an insufficient immune response.

Bernstein et al. used a guinea pig model of genital HSV-2 to test the efficacy of R2 vaccine. The R2 vaccine contains live attenuated type 1 Herpes simplex virus that is unable to invade the nervous system. The investigators used three routes of inoculation of the R2 vaccine: intramuscular, intradermal and intravaginal. They found that the R2 vaccine replicated in the genital tract without infecting the neural tissue and causing any disease. Out of the three routes used to administer the vaccine, the intradermal route proved to be the most effective at inducing viral replication and production of neutralizing antibodies. The conclusion from this paper is that a vaccine containing the live attenuated form of HSV that has been disabled from invading the nervous system has a promise of being an effective vaccine for Herpes simplex viruses. The development of a HSV vaccine would be a game-changer given HSV-1 and HSV-2 caused 3.7 billion and 491 million infections worldwide respectively. 

-Bethel 

References

• https://www.nature.com/articles/s41541-020-00254-8

• https://www.who.int/news-room/fact-sheets/detail/herpes-simplex-virus