A study by Irish scientists has shown, for the first time, direct evidence of cellular movement between the lung and gastrointestinal (GI) tract. This discovery may potentially lead to the design of new vaccines against infections such as HIV and E Coli.

The study, a collaboration between researchers at Trinity College Dublin (TCD) and the Icahn School of Medicine at Mount Sinai (MSSM) in New York, found new routes of cellular traffic to the GI tract.

The movement of immune cells to the GI tract is critical for the body's defence against infections; therefore, studying the mechanisms by which immune cells are directed to the GI tract is the key to developing new vaccines against mucosal infections such as HIV.

This could broaden the potential vaccinations available to tackle such infections.

Traditionally, vaccines are administered via injection but opening up needle-free, particularly mucosal routes, is valuable because it can enhance patient compliance and facilitate the induction of stronger immune responses at the site of infection.

The human immune system has a type of cell called the dendritic cell (DC), which is responsible for inducing immune responses during infections. These cells orchestrate the movement of lymphocytes to various compartments in the body, a key event in the immune response.

Current theories suggested that only intestinal dendritic cells had the capacity to endow lymphocytes with the capacity to travel to the small and large intestine to fight infection. However, the research teams have shown for the first time that dendritic cells in the lung can strongly promote homing of lymphocytes to the intestine.

The Dublin and New York research groups targeted dendritic cells in the lung via a nasally administered immunization, which resulted in a successful immune response being activated against a highly infectious strain of salmonella.

The results also showed that using this pathway the immunisation was significantly more potent at triggering the immune response to salmonella than an orally administered vaccine, which would have selectively targeted dendritic cells in the gut.

Dr Ed Lavelle, Associate Professor in Immunology in the School of Biochemistry and Immunology, TCD said: "These are very exciting findings which may provide opportunities to develop novel vaccine strategies for gastrointestinal infections. While oral vaccination can be effective the option of vaccination in the respiratory tract could be invaluable in cases where the oral route is not optimal."

This work is a major collaboration between three centres including the Icahn School of Medicine at Mount Sinai New York, The Rockefeller University New York and Trinity College Dublin.

The study was recently published in the leading peer reviewed medical journal, The Journal of Experimental Medicine.