Scientists supported by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), have identified a defect in the immune response of people with the skin condition atopic dermatitis that puts them at risk of developing serious complications following smallpox vaccination.
Led by Donald Y.M. Leung, M.D., Ph.D., of the National Jewish Medical and Research Center in Denver, the researchers used laboratory-grown human skin cells to show that an immune system protein called LL-37 is critical in controlling replication of vaccinia virus, the live virus that is the key component in standard smallpox vaccine.
The investigators are part of NIAID's Atopic Dermatitis and Vaccinia Network, which was created in 2004 to integrate clinical and animal research aimed at reducing the risk of eczema vaccinatum, a potentially deadly complication of smallpox vaccination. Eczema vaccinatum occurs almost exclusively in people who have a history of atopic dermatitis, a common, non-contagious skin disorder also known as eczema.
"This new research, the first to be published by Atopic Dermatitis and Vaccinia Network scientists, illuminates one potential mechanism leading to eczema vaccinatum and improves our understanding of the immune responses to smallpox vaccine of people with atopic dermatitis," says NIAID Director Anthony S. Fauci, M.D.
Published in this month's issue of Immunity, the study details how the overproduction in skin cells of inflammation-promoting molecules called interleukin-4 and interleukin-13 (IL-4 and IL-13) hampers LL-37 activity in people with atopic dermatitis. LL-37, a small protein produced in skin cells, is part of the body's first line of defense against invaders. Earlier research by Dr. Leung and his colleagues suggested that LL-37 is critical in controlling the spread of vaccinia virus.
In the current study, the investigators used skin samples taken from people with atopic dermatitis (as well as samples taken from healthy volunteers without skin disease and from people with another skin condition called psoriasis) to further investigate how dysfunctions in the immune response of people with eczema set the stage for eczema vaccinatum. When exposed to vaccinia virus, the skin samples from healthy volunteers and from those with psoriasis reacted by producing more LL-37. As a result, the replication of the virus was controlled and eventually halted. In contrast, LL-37 production was minimal in skin samples from people with atopic dermatitis and vaccinia replication was poorly controlled. Next, the scientists exposed skin samples from people with atopic dermatitis to vaccinia, and then added LL-37. With the LL-37 supplement, the skin cells successfully controlled the viral replication.