protection from the plague.
Yersinia pestis , which causes plague, is one of two bacteria
NIAID / NIH
the doctors consider them harmless hitchhikers at best and dangerous at worst pathogens. But a new study in mice shows that the herpes virus, which most of us relate to life, can have a surprising benefit: They provide protection against pathogenic bacteria, including the one that causes the plague. The effect is a rare example of a beneficial relationship between a virus and its host, the researchers say.
Eight human herpesviruses are known, and most people are infected with several of them at an early age. They can cause serious illness: Cytomegalovirus (CMV), for example, can blind people with weakened immune systems, and the Epstein-Barr virus (EBV) can cause tumors. But in most cases, herpes becomes latent: They just hang in the body, never leaving but never make trouble
A key player in maintaining this balance is a host molecule called interferon -γ (IFN. -γ). But not everything he does. IFN-γ also helps fight bacterial infection by activating macrophages, a type of white blood cell that engulfs microbes. So viral immunologist Herbert Virgin of Washington University School of Medicine in St. Louis, Missouri, said that mice latently infected may be more resistant to bacterial infection, because these mice had higher blood levels IFN-γ.
The intuition was vindicated, at least two of the three herpesvirus subfamilies. The mice latently infected with a so-called b -herpesviruses or gammaherpesvirus were highly resistant to infection Listeria monocytogenes , a food-borne microbe, and with Yersinia pestis , the plague bacteria, Virgin and his colleagues found. (The control animals developed a severe infection after exposure to either bug.) Latent infection with the third subfamily - alphaherpesvirus -. Do not offer such protection, reports the team tomorrow Nature
determine whether the same is true in humans will be a challenge, says Virgin, if only because it will be difficult to find enough people who have never been infected with beta- or gammaherpesvirus. But if the virus also protect humans, researchers would need to look in a new way, says Virgin. After coevolving with their hosts for 100 million years, "one could say they are part of our normal flora," he said, as the microbes living in our guts. And vaccines being developed against CMV and EBV can be studied more carefully, he notes, as they may increase the long-term risk of bacterial infections.
There are some other examples of a pathogen avert another says Jacob Koella, which studies host-parasite evolution at Imperial College London. for instance, schistosomiasis, a parasitic disease, appears to protect the host against malaria. But this is the first example of a do-good virus, he said . Yet many more of these evolutionary compromise may exist Koella predicted ". It is something that not enough people think "
Related site
- An introduction to the eight human herpesvirus known
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