The Herpes Advantage: When One Infection Protects Against Another

“Every cloud has a silver lining,” that’s what people say sometimes. But they are not thinking about VHS at the moment. HSV or the herpes simplex virus can be unpleasant, but the viruses that trigger it and other related illnesses can have a benefit. At least in mice, they provide bacterial resistance against diseases like bubonic plague.

Herpes is just one of several itchy, blistering infections, caused by the group of viruses that are aptly called herpes viruses. Eight members of the group of viruses infect humans and cause various diseases, including chickenpox, shingles, glandular fever, and indeed herpes itself.

Almost everyone contracts one of these viruses during their childhood. But the group of viruses will remain in the body permanently; not just for the holidays. After your immune system fights off the primary infection, the virus enters a dormant phase called “latency.” It remains hidden, with no apparent symptoms. But it is likely to reactivate at any moment.

In this way, herpes viruses are like parasites for life, guaranteeing their own survival and causing damage to the health of their host. In extreme cases, latent viruses can cause chronic inflammation, which in turn can lead to autoimmune diseases or some forms of cancer.

But there is also a silver lining to herpes. Erik Barton and his colleagues at the University of Washington School of Medicine found that once infected, mice entered the latent phase and became surprisingly resistant to certain types of bacteria. Unlike their susceptible and uninfected peers, they are even capable of fighting off the fatal plague bug, Yersinia pestis.

In mice, at least, dormant herpes viruses become paying tenants rather than squatters – resistance to bacteria is their rent. The latent phase is vital to the effect of resistance, and Barton discovered that a mutant herpes virus infects but provides nothing in return for its host.

Viruses work by putting the immune system on alert. The effect is like generating a terror alert, causing an intensified level of security where the body is ready to protect itself from any threat. Viruses activate the release of cytokines at high levels. Cytokines are chemicals of the immune system. These molecules, which include IFN-g (interferon-gamma) and TNF-a (tumor necrosis factor alpha), help coordinate defense against infection.

These chemicals trigger macrophages, a white blood cell. These cell killers consume invading bacteria and digest them. They are activated in large quantities in latent stage herpes virus-infected mice. This sequence is the immune system’s way of protecting us against various bacterial invaders. However, in Barton’s study, protection was initiated by viruses and persisted longer than usual. Good for mice.

What do we gain from these viruses? Will it have the same effect on us as mice? Barton thinks so. In their research, two different strains, gHV68 (murine gammaherpesvirus 68) and MCMV (murine cytomegalovirus), had a similar effect. He thinks that giving bacterial resistance is a universal characteristic of all herpes viruses.