We may be a听step closer to getting rid of genital herpes. Two vaccines are about to progress to clinical trials after proving to be safe and effective in guinea pigs and monkeys.
Genital herpes is a sexually-transmitted infection that affects more than one in six people aged 14 to 49 in the US. It is usually caused by a strain of the听herpes simplex virus, called HSV-2, which burrows into the skin and produces painful sores. The virus then permanently lodges in nerve cells and causes periodic flare-ups.
Previous efforts to develop a herpes vaccine have failed. One of the most promising contenders 鈥� a vaccine called GEN-003 鈥� was abandoned in September after underperforming in clinical trials.
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Part of the problem is that preclinical research is usually done in mice, which are not good models for human herpes, says听听at Louisiana State University in Baton Rouge. That is why his team has tested a new vaccine using guinea pig and monkey models.
The vaccine is an engineered version of herpes simplex virus that helps train the immune system to fight the real thing.听The part that normally allows the virus to enter nerve cells has been removed so that it cannot permanently lodge in the body.
Prevent and treat
A recent guinea pig study found that the vaccine provided complete protection against genital herpes. None of the nine vaccinated animals developed symptoms of the disease after they were exposed to a highly-infectious strain of herpes simplex virus.
A soon-to-be-published study found that the vaccine was also able to treat genital herpes in guinea pigs that were already infected. 鈥淚t didn鈥檛 eliminate the virus but boosted the immune system to prevent its reactivation,鈥� says Kousoulas.
In addition, the vaccine also performed well with no adverse side effects in monkeys. The team is now hoping to start a human trial within a year. 鈥淲e think it has tremendous potential as both a preventative and therapeutic vaccine,鈥� says Kousoulas.
Work in mice suggests that the vaccine may also protect against HSV-1. If this turns out to be true for people, the vaccine should also defend against cold sores.
Potent alternative
Another promising vaccine is being developed by听听at the University of Pennsylvania. It contains three protein fragments of the herpes simplex virus that are also designed to beef up the immune system without causing symptoms.
Last year, Friedman鈥檚 team showed that their vaccine听听in a study of 85 guinea pigs and 6 monkeys. They are currently tweaking the vaccine to make it work even better and are hoping to start human trials in 18 months. The aim of the vaccine is to prevent herpes rather than to treat it.
Kousoulas believes his team鈥檚 vaccine may work better because it contains a live virus rather than protein听fragments. Live vaccines are already in routine clinical use for protecting people against the related herpes zoster virus, which causes chicken pox and shingles. In contrast, previous herpes vaccines containing protein fragments 鈥� like GEN-003 鈥� have not worked as well.
However, Friedman believes the excellent preclinical results suggest the particular proteins in his team鈥檚 vaccine may be more potent. Their vaccine may also be safer than Kousoulas鈥� vaccine because it isn鈥檛 live, he says. 鈥淗uman trials will be required to assess which approach, if any, will work in people,鈥� he says.
The vaccines could become available within five years if they pass clinical trials, says Kousoulas.
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