H7N9 influenza vaccine failure due to “immune camouflage”

Researchers have explained how H7N9 influenza hides from the human immune system.

H7N9 vaccine development has become a priority for public health officials due to its high rate of lethality and pandemic potential. However, candidate vaccines have failed to elicit a strong immune response necessary to protect from infection. A study has revealed that it may be due to immune camouflage.

The study by Anne S. De Groot, Director of the Institute for Immunology and Informatics at the University of Rhode Island, and CEO at EpiVax, and colleagues shows that the H7N9 haemagglutinin (HA) surface protein has evolved a set of mutations that make it similar to human protein. These mutations appear to effectively camouflage the pathogen from the immune system.

H7N9 vaccines far less immunogenic

Computer tools developed by De Groot were able to predict the efficacy of new vaccines. “Our prediction that H7N9 vaccines would have low efficacy was made before any clinical data were available,” De Groot explained. “We were absolutely correct: in comparison with H1N1 and H3N1, H7N9 vaccines are far less immunogenic.”

De Groot’s research team has developed a computational tool, JanusMatrix, which is capable of determining whether a viral protein is similar to human protein. It turns out that HA from H7N9, but not from other investigated influenza strains, shows high similarity to several human proteins.

These findings have the potential to impact vaccine development. “It could explain why some candidate vaccines for pathogens that have co-evolved with human beings – like M. tuberculosis and HIV – do not work well. This research suggests that ‘tweaking’ pathogen proteins to remove those camouflaging sequences would result in more effective vaccines,” concluded De Groot.