Better understanding of T cell response

Swedish and U.K. researchers report that an apparently "acute" human viral infection can cause a persistent, activated CD8+ T cell response a long time after patients have recovered.

The team said the sustained response to parvovirus B19, traditionally not thought to be a true persistent infection, indicates that the virus likely remains in the patient's body long after symptoms have cleared up.

The findings, reported in the open access journal PLoS Medicine, give a better understanding of the body's T cell response and have important implications for vaccine development and treatment of this viral infection.

Human parvovirus B19 can cause a wide range of conditions depending on the patient's immunologic and hematologic status. In people with, for example, sickle cell anemia, infection can cause severe aplastic anemia, where the bone marrow stops making blood completely for a time. In a normal person, parvovirus B19 infection is often asymptomatic but can result in long-term arthritis. In pregnant women, it can cause intrauterine fetal death.

The team of researchers from the Karolinska Institute, Stockholm, Sweden, and University of Oxford, Oxford, U.K., said that traditionally, clearance of acute infection has been associated with the lifelong emergence of antiviral IgG. But there has been increasing evidence for an important role for cellular immune responses, which suggests there might be more to the way the body deals with this virus.

The team studied two groups of people: 11 who had been recently infected and five who had the virus many years ago. The CD8+ T cell responses "increased in magnitude over the first year post infection despite resolution of clinical symptoms and control of viraemia," say the authors. However, patients tested many years after infection had lower frequencies of B19 specific T cells

The likely explanation for the body's immune response "is through low level antigen exposure," suggest the authors, and they conclude that these findings should be considered during vaccine development.

http://www.plosmedicine.org/