Decrease of virus receptors during highly pathogenic H5N1 virus infection in humans and other mammals.

Highly pathogenic avian influenza H5N1 virus causes a severe, often fatal, pneumonia in humans. The tropism and pathogenesis of highly pathogenic avian influenza H5N1 virus can partly be explained by the presence of H5N1 virus receptors in the human alveoli, which are the site of inflammation during pneumonia. Although studies on the distribution of influenza virus receptors in normal respiratory tract tissues have provided significant insights into the cell tropism and pathogenesis of influenza viruses, the distribution of influenza virus receptors have not been studied during influenza virus infection. Therefore, we studied the distribution of H5N1 virus receptors, by virus and lectin histochemistry, during highly pathogenic avian influenza H5N1 virus infection in alveolar tissues of humans, macaques, ferrets, and cats. In all species, we observed a decrease of H5N1 virus receptors in influenza virus-infected and neighboring cells. The observed decrease of H5N1 virus receptors was associated with the presence of MxA, a known marker for interferon activity. Taken together, our data suggest that the decrease of H5N1 virus receptors might be part of a defense mechanism that limits viral replication in the lower respiratory tract.