Viruses Mingle To Escape The Immune System

Antiviral immunity has been studied for decades with efforts focused on interactions between infected cells and the viruses, few studies have focussed on interactions between the viruses, or the relationship between viruses or variants of the same virus.

As published in the journal Nature Microbiology the team experimented on the vesicular stomatitis virus which typically targets horses and cattle but can jump to infect humans that care for the animal hosts. Methods used by VSV to avoid the immune system were evaluated to examine how it can survive the effects of interferon. 

The immune system responds to viral infections in many ways including increasing body temperature and releasing pro-inflammatory agents; the first agents to target viruses are interferons that are signalling proteins which interfere with the virus’s ability to infect cells. 

The researchers developed a theory of virus social evolution based on their findings, suggesting that natural selection leads to the appearance of viral variants that block interferon. Viruses evolved and have developed methods to avoid interferon activity, while employing these methods they also change the adaptation of other members of given viral populations. This study showed the relationship between viruses playing roles in the adaptation of interferon resistant variants and the evolution of these pathogens involving a social process. 

Using mice, cultured cells, and computer simulations the team evaluated internal interactions of vesicular stomatitis and found evidence of social interactions between different viruses; interferon stimulating viruses check the fitness of other pathogens within the vicinity, if they find others that can block interferons the stimulating viruses mingle with the resistant counterparts to evolve the ability to shut down protective proteins. If the viruses shut down interferon this also decreases its ability to produce more of its kind, thus sacrificing makes the interferon blocking ability and altruistic trait. 

Findings suggest that viral researchers may be able to apply ecological and social principles of more complex animals to viruses, which may make it easier to predict behaviors of viruses and develop methods to disrupt interactions between viral pathogens. 

“In this work we show the altruistic capacity of the viruses, in which certain paths of escape from the immune system can be selected, although they may have a cost for viruses that encode this character,” said Domingo-Calap.