The human immune system can "remember" invading pathogens, such as viruses, and can recognize intruders from previous infections and respond more quickly and robustly.

The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, has awarded a $2 million, five-year grant to Ken Oestreich, an assistant professor at the Virginia Tech Carilion Research Institute, to study immunological memory.

Importance of immune for more effective vaccine

"We want to know how memory cells form as part of the immune response," said Oestreich, who also serves as an assistant professor in both the Department of Biomedical Sciences and Pathobiology at the Virginia-Maryland College of Veterinary Medicine and the Department of Internal Medicine at the Virginia Tech Carilion School of Medicine.

"Understanding how these cells form is critical for the design of more effective vaccines, as well as new therapies that capitalize on the body's natural defense system," said Oestreich

In response to infection by intracellular pathogens, such as influenza, the immune system triggers a boost in the number of specialized immune cells available to fight infection. Called effector T cells, these soldiers differentiate into two classes to battle influenza: T helper 1 (Th1) and T follicular helper (Tfh) cells.

Oestreich and his team previously discovered that, despite their different functions, these T cell populations might be developmentally linked. These two effector cell types perform distinct duties as part of an immune response.

Th1 cells help coordinate the responses of other immune cells at the site of infection, while Tfh cells help other cells make antibodies specifically designed to eliminate the pathogen.

As the immune system eliminates the infection, the large population of defending cells is no longer needed, and their numbers wane. However, a small number of cells are left behind. These cells transition from actively fighting to a passive state.

This means that if the body sees the same pathogen during a future infection, the memory effector T cells bounce back into action, wiping out the disease so efficiently that the host often does not even develop symptoms.

It's unclear, though, whether memory cells arise directly from the fighting effector T cells, or whether they form as a separate set of cells during infection. It was previously thought that they use the same battle plan as before, where memory Th1 cells fight at the site of infection, while memory Tfh cells work with other cells to produce antibodies needed to defeat the invader.

"We are questioning that now," Oestreich said. "We have good preliminary evidence suggesting that Th1 cells can give rise to Tfh cells and that they may transform into memory T cell populations."

"We are investigating whether Th1 cells can give rise to memory cells," Oestreich said. "This would mean that memory populations can come directly from effector cells, allowing them to switch roles as needed during an immune response."