A new study reveals that the reason candidate vaccines for H7N9 influenza have failed to elicit strong immune responses may be due to immune camouflage.
One of the ways by which the immune system detects infection is by presenting short peptides derived from the pathogen to T-cells, which distinguish between foreign and self antigens. The study shows that the H7N9 hemagglutinin (HA) surface protein has evolved a set of mutations that make it similar to human proteins, and the presented peptides thus resemble self antigens. The H7N9 influenza strain appears to effectively camouflage itself from the immune system.
“The original observation of low H7N9 T-cell epitope content was made before any data were available on vaccine efficacy,” says senior author Prof. Anne S. De Groot, Director of the Institute for Immunology and Informatics at the University of Rhode Island and CEO at EpiVax, Inc. “It turns out that we were absolutely correct. By comparison with H1N1 and H3N1, H7N9 vaccines are far less immunogenic.”
Prof. De Groot’s research team has developed a computational tool, JanusMatrix, capable of determining whether a given viral protein is similar to any human protein in residues relevant for antigen presentation.