Researchers at the Trudeau Institute, New York, have found two important components that may help improve cellular immunity against influenza virus.
David L. Woodland, project leader and president of the institute, said: "It has become apparent that protective cellular immunity to viruses like influenza requires white blood cells to be pre-positioned in the lungs, the site of initial infection."
This approach has led to efforts to develop vaccines that persuade cells to localize in the respiratory tract.
Woodland added: "That, however, has turned out to be difficult, because we don't fully understand the signals that direct immune cell migration to distinct locations in the body."
Woodland and colleagues have begun to shed light on this important question. The team has discovered that two distinct signals are required to instruct virus-fighting white blood cells, known as T cells, to migrate into the lungs.
The first T cell is residual antigen (needed to stimulate antibodies) that remains in the lymph nodes for weeks after the initial infection has been cleared.
The second is an "imprinting event" that instructs the T cells to specifically seek a target organ (in the case of flu, the lung).
This imprinting event directs the T cells to where the original infectious agent entered the body and, importantly, where the cells need to go to fight future infections.
This new information has major implications for future vaccine research and could lead to the development of vaccines designed to promote immunity to respiratory infections.
The study has appeared in the current issue of the Journal of Experimental Medicine.