A compound found in red wine and chocolate stops the replication of poxviruses.
Researchers working at Kansas State University in Manhattan as well as the Centers for Disease Control and Prevention (CDC) tested various concentrations of resveratrol in human cells infected with the vaccinia virus.
This is a close relative of the virus that causes smallpox and it also formed the vaccine that eradicated the deadly human disease.
At high concentrations, resveratrol stopped vaccinia from multiplying itself in the early phase of infection, thereby preventing the virus from spreading to other cells.
The concentrations of resveratrol that the researchers used were much higher than those that occur naturally in food.
The team also found that resveratrol had a similar effect on monkeypox, which is a deadly and contagious poxvirus that has caused outbreaks in Africa.
These two sets of results suggest that resveratrol "has a good chance of inhibiting all poxviruses," says first study author Dr. Shuai Cao, who researches resveratrol and its effect on viruses in the Division of Biology at Kansas State University.
The authors report their findings in the journal Frontiers in Microbiology.
Resveratrol has many biological properties
Resveratrol is a compound that occurs naturally in many strongly colored food plants — such as grapes, cocoa beans, blueberries, and peanuts — and has been found to have antioxidant, anticancer, antiviral, and hormonal properties.
Scientists' interest in resveratrol began in 1992, when researchers suggested that the reason that French people had relatively low levels of heart disease despite enjoying a diet high in saturated fat was because of their penchant for red wine.
Since that point, thousands of studies have examined the "French paradox" and resveratrol has become widely known as the "red wine compound."
However, evidence about the health benefits of resveratrol is also conflicting. For instance, a 2014 study of a large group of Italians found that a diet rich in resveratrol neither increased lifespan nor protected against cardiovascular disease and cancer.
Resveratrol stopped DNA replication
In the new study paper, the authors note that while we know that resveratrol can either aid or block "replication of a number of viruses," we know little about its effect on poxviruses.
However, it would be useful to have such knowledge because, even though smallpox has been eradicated, other poxviruses "continue to cause serious diseases," and some forms are being developed to carry vaccines and to treat cancer.
"In order for a poxvirus to infect a host," explains co-author Anil Pant, a doctoral student in biology at Kansas State University, "it has to first enter a cell and make a lot of copies of its genome inside the host cell."
Their study showed that resveratrol stops vaccinia virus from replicating its DNA and genome.
The authors note that resveratrol's ability to inhibit the virus is not related to vaccinia's N1 protein, which is a potential "binding target" for resveratrol.
"Further experiments," they add, "demonstrated that resveratrol had little effect on [vaccinia virus] early gene expression, while it suppressed [vaccinia virus] DNA synthesis, and subsequently post-replicative gene expression."
Resveratrol likely inhibits other poxviruses
Dr. Cao says that many poxviruses "infect many species" and have "similar mechanisms to replicate their DNA."
Therefore, since their experiments showed that resveratrol can stop vaccinia and monkeypox from replicating, "it should be able to inhibit other poxviruses as well," Dr. Cao adds.
Vaccinia virus, which has proven its value in the eradication of smallpox, is not only an ideal model for studying in the laboratory; it is also being used in the development of cancer treatments and those that fight other viruses.
The researchers suggest that their findings will "prompt further investigation" into the effects of resveratrol on other phases of virus replication and clarification of the mechanisms involved.
"Our research may be a stepping stone to using resveratrol as a complementary treatment for viruses during a time of growing concern over drug resistance."