Lack of nutrient turns flu nasty

From San Diego, at Nutrition Week

A dietary deficiency in an essential trace mineral may cause a usually harmless strain of the flu to mutate into a virulent pathogen.

Studies have suggested that pathogens called coxsackieviruses might be more likely to mutate in hosts that are short on selenium, a metal involved in producing protective compounds called antioxidants. Recent research suggests a similar tendency toward mutation for at least one strain of influenza virus, says Melinda A. Beck of the University of North Carolina in Chapel Hill.

Beck infected mice with influenza strain A/Bangkok/1/79. Some of the infected animals received diets deficient in selenium.

Concentrations of virus antibodies in the blood–an indication of the severity of an infection–were similar in all the mice. Nevertheless, selenium-deficient mice experienced more serious symptoms, such as lung damage, than did other mice.

Beck then removed some viruses from the lungs of selenium-deficient mice and injected them into healthy mice getting normal amounts of selenium. Like the nutrient-deficient mice, these animals also become ill, suggesting that the virus itself was at fault, not the animals’ immune response.

Beck compared the genome of the original flu strain with genomes of strains isolated from the infected animals in both diet groups. One gene showed many more changes when it came from a viral strain in selenium-deprived animals. That gene produces a protein called matrix 1, which has been associated with the flu virus’ virulence.

Craig J. McClain of the University of Louisville in Kentucky calls Beck’s research “thought-provoking.” Nutrient deficiencies might have led to the rise of other potent viruses, such as HIV, he suggests.

Selenium deficiency is prevalent in China, where many worldwide outbreaks of the flu originate, Beck adds.