An important mechanism for stimulating the protective immune response following seasonal flu vaccinations, is now clearly identified by scientists.
While seasonal influenza vaccines protect 60 to 90 percent of healthy adults from "the flu," the mechanisms providing that protection are still not well understood.
The study led by Octavio Ramilo, MD, chief of Infectious Diseases and an investigator in the Center for Vaccines and Immunity at Nationwide Children's Hospital and professor of Pediatrics at The Ohio State University (OSU) College of Medicine, and Hideki Ueno, MD, PhD, an investigator at the Baylor Institute for Immunology Research at Baylor University, demonstrated how certain T cells in the blood are stimulated to provide protective antibody responses with seasonal flu vaccines.
Blood samples before and after influenza vaccination from three groups of healthy study participants were analyzed for antibody responses.
The groups included two sets of adults, one receiving flu vaccines during the 2009-2010 winter and the other receiving vaccination during the 2011-2012 winter. The third group included children receiving the flu vaccine during the 2010-2011 winter.
Analyses showed a temporary increase in a unique subset of helper T cells expressing the co-stimulator molecule ICOS adds to the immune response by helping B cells produce influenza-specific antibodies.
Results indicated that at day seven following the administration of a flu vaccine in all groups, stimulated T cells were evident, contributing to the development of the immune response.
The T cells positively correlated with increased antibodies against each flu virus strain examined, with the exception in the children's group against the swine-origin H1N1 virus.
Further experiments demonstrated that this unique subset of helper T cells can boost production of existing antibodies that fight flu by stimulating memory B cells, but do not help production of new antibodies by naive B cells.
The study has been published in Science Translational Medicine.