Researchers develop vaccine strategy for genital herpes

Yale researchers have developed a new model for vaccination against genital herpes, a disease for which there has been no cure and no effective immunisation. Their study appears in the advance online publication of Nature.

Genital herpes, known formally as herpes simplex virus (HSV), is a mostly sexually transmitted infection (STI) that accounts for significant disease and morbidity.

Until now, most efforts to develop a vaccine have focused on the immune system's antibodies, or T cells, circulating through the body. When T cells encounter foreign invaders such as bacteria or viruses, they learn to recognise them and mount ever-stronger immune responses to fight them. But efforts to harness these circulating T cells have not been effective in organs such as the vagina, intestines, lung airways, and central nervous system, which restrict the entry of these ''memory'' T cells.

To investigate an alternative approach, the Yale team focused instead on peripheral tissue in the female genital tract, where viral exposure occurs. The challenge was to recruit virus-specific T cells into the vaginal mucosa without triggering a potentially harmful inflammatory response of the immune system.

Working with mice, they explored a two-part vaccine strategy they call ''prime and pull.'' The ''priming'' involved conventional vaccination to elicit a system-wide T cell response. The ''pulling'' involved recruitment of activated T cells directly into the vaginal tissue, via topical application, of chemokines - substances that help mobilize the immune cells.

They found that the recruited T cells were able to establish a long-term niche and offer protective immunity against genital herpes by reducing the spread of HSV into the sensory neurons.