Sometimes a virus lies dormant inside a host cell. Other times, the virus destroys everything.

According to a new study, whether a virus lies idle or goes on the attack depends on how the virus' DNA is packaged.

The research, published this week in the journal eLife, could also explain the behavior human-infecting viruses.

"I found for the first time that the mechanics of how DNA is packaged inside a virus determine the course of infection," Alex Evilevitch, professor of pathobiology at the University of Illinois, said in a news release.

When viruses invade bacteria, they follow one of two pathways, "lytic" and "latent."

Lytic viral infections seize the host cell's resources and use them to quickly replicate. The multiplying virus eats the cell and invades the next host, repeating the process.

When a virus is latent, its DNA incorporates itself into the host cell's genome. When the cell divides, the virus' DNA is copied along with the cell's genome.

"The many viral infections that we carry can remain latent for a very long time. Sometimes they go lytic, and that's when we develop symptoms," Evilevitch said.

Evilevitch and his colleagues set out to identify what causes a virus to switch from latent to lytic.

Many studies have focused on the shape and behavior of protein capsids, which protect viral DNA and smuggle it into host cells.

For the latest study, Evilevitch used isothermal titration calorimetry to measure the stresses and strains exerted on viral DNA molecules prior to being injected into a host cell.

Isothermal titration calorimetry, ITC, measures small thermal energy changes in a system. To better understand differences between viral infection pathways, Evilevitch and his research partners tracked thermal energy changes as thousands of viral particles as they interacted with bacteria cells.

ITC measurements revealed two distinct patterns. A large spike in thermal energy revealed the hundreds of viruses simultaneously injecting their DNA in the bacteria cells. The second pattern featured slow, sporadic infections.

The data showed latent infections are synchronous, while lytic infects invade in an uncoordinated fashion. Irregular infections quickly killed their host cells. Synchronized infections preserved their host cells.

In followup experiments, scientists found an increase in temperature triggered an increase in synchronous infections. Researchers determined heat made virus DNA molecules more flexible and fluid. An increase extracellular magnesium ion concentrations had a similar impact.

"The DNA becomes more flexible; it has more of a fluid character," Evilevitch said. "As a result, it's more likely to be ejected -- like toothpaste out of a tube. But if it's solid, it's going to get stuck inside the tube."

The research shows environmental conditions can alter the mechanics of virus DNA, which influence the infection pathway. In the future, researchers could manipulate virus DNA to prevent an infection from becoming lytic.

Related Links
Epidemics on Earth - Bird Flu, HIV/AIDS, Ebola

Tweet

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

China culls 38,000 pigs as swine fever spreads
Beijing (AFP) Sept 2, 2018
More than 38,000 pigs have been culled across China, state media said Sunday, as the world's largest pork producer scrambles to contain an outbreak of African swine fever. The disease has been discovered in five Chinese provinces, the official Xinhua news service reported, quoting statistics from the country's ministry of agriculture. China reported its first case of the disease in August in northeast Liaoning province. Since then the disease has moved south, with cases discovered as far as ... read more