New Herpes Vaccine Shows Promise
Despite the prevalence of herpes and its effect on human health, an approved vaccine that cures HSV-1 or HSV-2 has yet to exist. That may soon change, however, as a new study reports success in the development of a vaccine that makes the virus more susceptible to the body’s immune system.
A Little Herpes Background
Health experts in virology tell us that the herpesvirus is an infectious agent belonging to the virus family Herpesviridae and is particularly insidious in that it causes both latent and lytic infections in a wide range of animals and humans resulting in nearly uncontrollable spread throughout human history. In short, the virus hides from our immune system and attacks both overtly and covertly.
The history of the herpesviruses is that it has been infecting and codiverging with vertebrate hosts for hundreds of millions of years. Geneticists have traced primate simplex viruses as far back as the most recent common ancestor of New World monkeys, Old World monkeys, and apes.
Herpes exists in a variety of strains. There are at least 8 herpesvirus types currently known to infect humans: Herpes simplex viruses (types 1 and 2), varicella-zoster virus, Epstein-Barr virus, Kaposi's sarcoma-associated herpesvirus and human cytomegalovirus.
Genital herpes is the most common sexually transmitted disease in the U.S. The herpes simplex virus is categorized into 2 types: herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2). HSV-1 is mainly transmitted by oral-to-oral contact to cause oral herpes (which can include symptoms known as “cold sores”), but can also cause genital herpes—you do the math. HSV-2 is a sexually transmitted infection that causes genital herpes.
Fighting Fire With Fire Using a Modified Virus
While both HSV-1 and HSV-2 infections are incurable, it is a manageable condition and is typically limited to anti-viral medications to lessen the effects of an outbreak. Today, however, scientists report that a potential vaccine containing a genetically-edited form of the herpes simplex virus might be the key toward a cure or prevention by giving our immune system the help it needs in building a response to infection.
According to a news release from the University of Nebraska-Lincoln, scientists recently published their latest herpes research findings in the journal Nature Vaccines that they have found a way to keep the virus from getting into the nervous system, which is the reason why the herpesvirus remains so well hidden and elusive to our immune system.
The news release explains that, “…after infecting mucosal tissues of the mouth or genitourinary tract, HSV works its way to the tips of sensory nerves that transmit signals responsible for the sensations of pain, touch and the like. With the help of a specialized molecular switch, the virus then breaks into the nerve cell, hitching a ride on the molecular equivalent of a trolley car that transports it along a nerve fiber and into the nucleus of a sensory neuron. Whereas the mucosal infection is soon cleared by the immune response, the infected neurons become a sanctuary from the body’s immune system, with HSV leaving only when stirred by rises in steroids or other stress-elevated hormones in the host.”
To prevent HSV from reaching the safety of the nervous system, the researchers in the aforementioned study chose to approach the problem by modifying a viral protein that they believe is responsible for the virus’s ability to travel along nerve fibers; but, not adversely affect the virus so much that it could no longer infect and trigger an immune response.
In other words, the researchers needed to create a version of the herpes virus that was still viable and relatively healthy, but an easy target for the immune system to recognize and attack. This would then prime the immune system against a new or recurring herpes infection from a non-modified herpes virus being passed from person to person.
“You can keep the virus from getting into the nervous system,” said Gary Pickard, professor of veterinary medicine and biomedical sciences at Nebraska and a co-author of the study. “That’s not that hard to do by making broadly debilitating mutations. But when you knock down the virus so much that it doesn’t replicate well, you are not rewarded with a robust immune response that can protect you from future exposures.”
When mice were inoculated with a herpes simplex virus type 1 virus with a modification in its genome referred to as the “R2 region,” the researchers found that their new construct performed well as a vaccine; and, that it was an improvement over earlier vaccines developed that proved to be less effective when other regions of the virus genome were targeted.
“So it’s the same story over and over again: Either your subunit vaccine doesn’t present enough antigens, or you make the live virus essentially so sick that it doesn’t work really well to generate an immune response,” Pickard said. “That’s why we’re so optimistic about our R2 platform, because it avoids all those problems.”
With the success of the modified HSV-1 vaccine, it was time to see if it would work on herpes simplex virus type 2 as well.
When tested on guinea pigs, however, not all of the inoculated lab animals proved to be protected following an infection with HSV-2. But it was an improvement, as viral shedding (when the virus goes from its latent state to an infectious state, typically—but not always—manifested as infectious lesions on the skin) showed to be significantly reduced in the inoculated animals.
“The fact that the viral shedding was knocked down so much with the R2 vaccine is really important, because it’s the viral shedding—even if it doesn’t cause lesions—that can then pass on the virus,” Pickard said. “If you have genital herpes, you can pass that on to your significant other, not knowing that you’re doing it. It’s very problematic. So the fact that the shedding was knocked down so much is a really good sign.”
The researchers report that they are now working on creating a modified HSV-2 virus to create a vaccine that will promote an immune response against HSV-2 infection.
Timothy Boyer has a Ph.D. in Molecular and Cellular Biology from the University of Arizona. For 20+ years he has been employed as a freelance health and science writer. Today, with an eye on the latest news, Timothy continues writing about science with a focus on what you need to know for healthier living. For continual updates about health, you can also follow Timothy on Twitter at TimBoyerWrites.
Image Source: Courtesy of Centers for Disease Control and Prevention Wikimedia public domain image.
“Vaccine shows promise against herpes virus” Nebraska Today 06 Nov. 2020.
“The R2 non-neuroinvasive HSV-1 vaccine affords protection from genital HSV-2 infections in a guinea pig model” Bernstein, D.I., Cardin, R.D., Smith, G.A. et al. Nature Vaccines 5, 104; published 06 November 2020.