Overview of current efforts
2.1. Biological feasibility for vaccine development There are no vaccines currently available for HSV infection, but the pipeline is rich with candidates in various phases of development. Vaccines are currently being developed both to prevent HSV-2 infection (preventive) and to treat HSV-2 infection (therapeutic). While most HSV vaccine research has prioritized HSV-2 rather than HSV-1, HSV-2 vaccines may also have benefits in preventing or treating HSV-1 infection given the homology between these viruses.
There are several lines of evidence that an HSV vaccine is feasible:
1. There is a safe and efficacious vaccine for varicella zoster virus (VZV), a closely related alpha-herpesvirus. Both a liveattenuated vaccine for preventive (prevention of varicella “chicken pox”) and therapeutic (prevention of herpes zoster or “shingles”) indications have been developed [27]. In addition, a subunit vaccine with a novel adjuvant was shown to prevent herpes zoster with 97% efficacy in a recent Phase III clinical trial [28].
2. Whether protective genital mucosal immunity could be induced by an intramuscular (IM) vaccination has been a concerning unknown for the HSV vaccine field. The development of the human papillomavirus (HPV) vaccine provides ample proof of concept that an IM vaccine can be highly efficacious against a mucosal genital viral pathogens [29].