Experimental Vaccine May Control Genital Herpes as Effectively as Pills

According to a recent study presented at the 2016 annual meeting of the Infectious Diseases Society of America (IDWeek), held from October 26 to 30, in New Orleans, Louisiana, three injections of an experimental vaccine may help to control genital herpes as effectively as taking daily antiviral pills for one year does.

Lisa K. McNeil, PhD, from Genocea Biosciences, Cambridge, Massachusetts, and colleagues presented 12-month data from the Phase 2a trial of the genital herpes immunotherapy GEN-003, showing that it durably reduces herpes simplex virus (HSV)-2 shedding and clinical disease for up to 12 months after dosing.

Genital herpes is a sexually transmitted disease (STD) caused by HSV-1 or HSV-2. This common STD is mostly associated with HSV-2 infection, which affects more than 400 million people aged 15 to 49 years worldwide, including many Americans; however, HSV-1 is also an important cause of genital herpes, which is estimated to affect about 140 million people in the same age group.

Although HSV recurrence and viral shedding rates vary widely, “[d]ata suggest that both B and T cell immunity are critical for control of reactivation of viral replication and disease,” the authors write, “but correlates of protection are unknown.”

Dr. McNeil and colleagues conducted a study in 310 people with symptomatic genital herpes, randomizing them to one of seven groups—six dosing groups and a placebo group. Participants received three intramuscular injections, three weeks apart, of one of the six GEN-003 dose combinations or placebo. The researchers tested participants’ antibody responses at baseline, as well as periodically throughout the study. They also collected genital swabs from participants twice daily for 28-day periods before and after the third injection, and at 6 and 12 months. Participants also recorded the days on which genital lesions were present.

The researchers previously selected the 60 μg per protein / 50 μg of adjuvant dose as the best for use in upcoming Phase 3 trials. In the group of participants that received this dose combination in the current study, the experimental vaccine induced a polyfunctional T cell response that peaked at day 8 and persisted through at least day 50. Participants had significantly increased antigen-specific IgG titers that persisted at least 3-fold higher than baseline level at 12 months; mean neutralizing antibody titers also increased and remained more than 2-fold higher than baseline level at 12 months.

According to the researchers, these immune responses were accompanied by significant clinical improvements: compared with baseline, viral shedding was reduced by 66%, and genital lesion rate was reduced by 65%. And 30% of participants remained lesion free for 12 months after receiving the injections.

A follow-up study is now enrolling participants to examine the long-term efficacy and immunogenicity of GEN-003 in individuals with genital HSV-2 infection.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.