Sunday, June 15th, 2008.

Journal of Medical Virology. 2008 Jun 12;80(8):1497-1504. [Epub ahead of print] [Link]

Coleman S, Gibbs A, Butchart E, Mason MD, Jasani B, Tabi Z.

Velindre Hospital, Velindre NHS Trust, Cardiff, United Kingdom.

Abstract

The continued presence of simian virus 40 (SV40), a monkey polyomavirus, in man is confirmed by the regular detection of SV40-specific antibodies in 5-10% of children who are unlikely to have received contaminated polio-vaccines. The aim of our experiments was to find cellular immunological evidence of SV40 infection in humans by testing memory T cell responses to SV40 large T antigen (Tag). As there is some indication that the virus may be present in malignant pleural mesothelioma (MPM) cells, we analyzed T cell responses in MPM patients and in healthy donors. The frequencies of responding T cells to overlapping Tag peptides were tested by cytokine flow cytometry. CD8⁺ T cells from 4 of 32 MPM patients responded (above twofold of control) to SV40 Tag peptides, while no positive responses were detected in 12 healthy donors. Within SV40 Tag we identified three 15 amino acid-long immunogenic sequences and one 9 amino acid-long T cell epitope (p138) (138FPSELLSFL146), the latter including a HLA-B7-restriction motif. T cell responses to p138 were SV40-specific as T cells stimulated with p138 did not cross-react with the corresponding sequences of Tag of human polyomaviruses BKV and JCV. Similarly, the relevant BKV and JCV Tag peptides did not generate T cell responses against SV40 TAg p138. Peptide-stimulated T cells also killed SV40 Tag-transfected target cells. This article demonstrates the presence, and provides a detailed analysis, of SV40-specific T cell memory in man.

Keywords: polyomavirus, T cell memory, epitope search, SV40.

Glossary

flow cytometry

(flow cy-tom-uh-tree) a test of tumor tissue to see how fast the tumor cells are reproducing and whether the tumor cells contain a normal or abnormal amount of DNA. This test is used to help predict how aggressive a cancer is likely to be. (See also ploidy, DNA, S-phase fraction.)

detection

finding disease. Early detection means that the disease is found at an early stage, before it has grown large or spread to other sites. Note many forms of cancer can reach an advanced stage without causing symptoms. Mammography can help to find breast cancer early, and the PSA blood test is useful in finding prostate cancer.

cytokine

(site-o-kyne) a product of cells of the immune system that may stimulate immunity and cause the regression of some cancers.

cell

the basic unit of which all living things are made. Cells replace themselves by splitting and forming new cells (mitosis). The processes that control the formation of new cells and the death of old cells are disrupted in cancer.

antigen

(an-tuh-jen) a substance that causes the body's immune system to react. This reaction often involves production of antibodies. For example, the immune system's response to antigens that are part of bacteria and viruses helps people resist infections. Cancer cells have certain antigens that can be found by laboratory tests. They are important in cancer diagnosis and in watching response to treatment. Other cancer cell antigens play a role in immune reactions that may help the body's resistance against cancer.

virus

very small organisms that cause infections. Viruses are too small to be seen with a regular microscope. They reproduce only in living cells.

mesothelioma

a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.

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