8 - How does the influenza virus jump from animals to humans?

Summary

As shown by the 2009 Swine Flu outbreak, the influenza epidemics are often caused by human-adapted influenza viruses originally infecting other animals. The influenza viruses infect host cells through the specific interaction between the viral hemagglutinin protein and the sugar molecules attached to the host cell membrane (called glycans). The molecular mechanism of the host switch for Avian influenza viruses was thus believed to be related to the mutations that occurred in the viral hemagglutinin protein that changed its binding specificity from avian-specific glyans to human-specific glycans. This theory, however, is not fully consistent with the epidemic observations of several influenza strains. I will introduce the bioinformatics approaches to the analysis of glycan array experiments that revealed the glycan structural pattern recognized by the hemagglutinin from viruses with different host specificities. The glycan motif finding algorithm adopted here is an extension of the commonly used protein/DNA sequence motif finding algorithms, which works for the trees (representing glycan structures) rather than strings (as protein or DNA sequences).

Introduction

The recent outbreak of “swine flu” is not the first flu pandemic (i.e. the spread of an infectious disease in the human population across a large region) in human history. Three worldwide outbreaks of influenza flu occurred in the twentieth century, in 1918, 1957, and 1968, respectively. “Spanish flu” is known as the most deadly natural disaster, which swept around the world in 1918 and killed about 50–100 million people.