"The size of the antiviral response is much greater than our previous estimates, and radically changes our perception of the T cell response to viruses," says Dr. Ahmed. "This research should prove very important for vaccine development, because you want a vaccine to induce a good response, and this research allows us to see directly what a good response is."

Dr. Ahmed believes the findings about virus-specific responses will most likely apply to viral infections in general, including infection with EBV (infectious mononucleosis), HIV and human T cell leukemia virus type 1 (HTLV-1), all of which are characterized by massive increases in the number of CD8+ T cells. "It is likely that most of the expanded CD8+ T cells in these infections are specific to those particular viruses also," he says.

Dr. Altman's initial findings have confirmed this prediction for HIV infection and he continues to actively pursue investigations of the CD8 T cell response to HIV in chronically infected patients on antiretroviral therapy.

One of the assays used in the study " tetramer staining " was developed by Dr. Altman while a researcher in the laboratory of Dr. Mark Davis at Stanford University. In the tetramer technique, small peptides (fragments of viral protein) of the virus are placed inside an MHC Class I (major histocompatibility complex) molecule. MHC Class I molecules are proteins that "present" pathogens to T cell receptors, which in turn recognize the pathogens and attack them.

A tetramer consists of four MHC molecules containing particular viral peptides. Labeled tetramers are then applied to a mixture of white blood cells and bind only to those CD8+ T cells that are specific for the MHC plus viral peptide combination.
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Contact: Holly Korschun
hkorsch@emory.edu
404/727-3990
Emory University Health Sciences Center
3-Jun-1998