Host nutritional selenium status as a driving force for influenza virus mutations

Previous work from our laboratory has demonstrated that infection with influenza A/Bangkok/1/79 (H3N2), a relatively mild strain of the virus, caused much more severe pneumonitis in selenium (Se)-deficient mice than in Se-adequate mice. Here we report that the increased virulence observed in the Se-deficient mice is due to mutations in the influenza virus genome, resulting in a more virulent genotype. Most of the mutations occurred in the gene for the M1 matrix protein, an internal protein that is thought to be relatively stable. A total of 29 nucleotide changes were observed in this gene, and all 29 changes were identical in three separate isolates taken from three different Se-deficient mice. In contrast, only one to three mutations were seen in the genes for the hemagglutinin or neuraminidase proteins, surface antigens that are known to be highly variable. Once the mutations have occurred, even hosts with normal nutritional status are susceptible to the newly virulent strain. This work, in conjunction with our earlier work with coxsackievirus, shows that specific nutritional deficiencies can have a profound impact on the genome of RNA viruses. Poor nutritional status in the host may contribute to the emergence of new viral strains