Writing in the Aug. 29 issue of The New England Journal of Medicine, Dr. Jeffrey A. Frelinger, Kenan professor and chairman of microbiology and immunology in the School of Medicine, and postdoctoral researcher Dr. Lawal Garba said despite substantial interest today "in the durability of immune responses following smallpox vaccination," little direct or quantifiable evidence of such durability exists.

"It's a question that's been largely unexamined," said Frelinger, who mentioned reports suggesting that the standard vaccine, which contains live vaccinia virus but not smallpox, or variola, virus, could protect against lethal infection in people vaccinated 50 years previously.

Vaccinia vaccine triggers an immune response to orthopoxviruses that can infect humans, such as monkeypox, cowpox, vaccinia and variola. During the course of another investigation, Frelinger and Garba tested blood samples from 13 laboratory workers who had been vaccinated according to federal guidelines because they work with vaccinia virus. Four had been vaccinated less than five years ago. Another nine individuals had been vaccinated either between five and 35 years previously or more than 35 years ago.

The researchers tested the strength of each individual's CD8 T cell response to vaccinia exposure by counting the number of cells that respond to vaccinia by production of interferon-gamma.

In the body's cellular immune response, CD8 T cells are a type of cytotoxic T lymphocyte, or CTL, white cells that kill other body cells that have been infected by a foreign organism. CTLs recognize surface markers on other cells in the body that label those cells for destruction. In this way, CTLs help keep virus-infected cells in check. CD8 T cells produce interferon-gamma
'"/>

Contact: Leslie Lang
llang@med.unc.edu
919-843-9687
University of North Carolina School of Medicine
28-Aug-2002