Abstract
In Japan, inactivated whole virus particle influenza vaccines (WPV) were used until 1971, while split vaccines (SV) have been used since 1972 to the present day. Both of vaccines are prepared by infecting chicken eggs (white Leghorn breed) with influenza virus and then using the urine solution of the infected eggs as the vaccine stock solution. Although WPV has the advantage of being more immunogenic than SV, it has the disadvantage of being more pyrogenic. However, while SV has an excellent safety profile, it is known that the ability to induce antibodies against influenza viruses is low in children without a history of influenza vaccination, and in elderly people with weakened immune systems. Therefore, the development of a vaccine with high immunogenicity and low adverse reactions is desired.
We are focusing on reducing febrile reactions in order to develop a highly effective influenza vaccine with reduced side effects of WPV. Extracellular vesicles (EVs) are basically produced by any cell and contain information transmitting substances such as proteins, lipids, and nucleic acids derived from the cells that produce them. They perform physiological functions in various parts of the body by circulating through the blood. We revealed by electron microscopy that WPV was contaminated with EVs derived from chicken eggs. We also found that WPV from which EVs had been removed by hypotonic solution treatment had high antibody-inducing ability and low pyrogenicity.
To identify the molecules involved in the febrile reaction of EVs contaminating the WPV preparation, EVs were isolated from WPV by Optiprep density gradient centrifugation. The composition of EVs was then analysed by microarray and nanoLC-MS/MS to identify white leghorn-derived microRNAs and proteins selectively contained in EVs in WPV. The contribution of each identified molecule to the febrile reaction and the mechanism are currently being verified.
