Selenium Deficiency Increases Severity of Flu Virus in Mice

If young mice are given a diet deficient in selenium and subsequently exposed to a human influenza virus, they get a more severe case of flu than animals fed adequate amounts of this essential trace element.

That’s the finding of a collaborative study by researchers at the University of North Carolina (UNC) in Chapel Hill; Nestle Research Center in Lausanne, Switzerland; and the Agricultural Research Service (ARS) in Beltsville, Md. And it follows the pattern seen in earlier studies with a lesser known virus. This indicates that a selenium deficiency can increase the virulence of a variety of viruses.

The researchers reported today in the FASEB Journal on the web that the mice getting selenium-deficient diets developed significantly more lung pathology than the animals getting ample selenium. The deficient mice had significantly more inflammation in their lungs, and the inflammation lasted much longer.

Selenium is a critical part of a major antioxidant enzyme that humans and animals produce to protect delicate cellular components against damage from oxygen free radicals. Americans get ample selenium in their diets, according to ARS nutritionist Orville A. Levander. Good sources include Brazil nuts, whole grain products and meat. But deficiencies can occur in parts of China, New Zealand and other nations where agricultural soils lack this element.

Levander collaborated with study leader Melinda A. Beck, a viral immunologist at UNC’s departments of Pediatrics and Nutrition, on this and the earlier studies. The researchers suspect that the influenza virus mutated to a more virulent form in the selenium-deficient animals because these animals lack antioxidant protection from the selenium-containing enzyme--glutathione peroxidase.

In 1995, the researchers reported that a normally harmless coxsackie virus mutated into a heart-damaging pathogen in selenium-deficient mice, but not in selenium- adequate mice. Beck and collaborators are now looking for mutations in the influenza virus genome.

ARS is the U.S. Department of Agriculture’s primary scientific research agency.

Scientific contact: Orville A. Levander, ARS Nutrient Requirements and Functions Laboratory, Beltsville, Md., phone (301) 504-8504, fax (301) 504-9062, levander@307.bhnrc.usda.gov.