The Role of Epstein-Barr Virus Infection and the Immunocompetence of Patients with Nasopharyngeal Cancer

Abstract

Seral IgA titer to gene products of Epstein-Barr virus is prevalently elevated in patients with nasopharyngeal carcinoma, an indication of EBV infection. Pathologically, tumor infiltrating lymphocytes that could be attracted by the presence of EBY in the NPC cells also increased immensely in the neighborhood of tumor nest. In a glance, EBV seemed to induce both cellular and humoral immune response. However, the immunocompetence of patients inversely decreased following the progression of the disease. Interleukin-l0 (IL-l0), a potent cytokine synthesis inhibitory factor, suppresses function of T cells and NK cells ns well as that of monocytes and macrophages, the major components of cellular immune response. Besides its suppression on cellular immunity, IL-b stimulates B cells to enhance their viability, cell proliferation, class II MHC expression and immunoglobulin secretion, a hallmark of humoral immune response. Interestingly, sequence of a EBV late gene, UCIIF1, is highly homologous to that of both mouse and human IL-10(BCRF1 gene product is now designated as vIL-10). It may exert a similar function like that of JL-10. The activity of vIL-10 may explain the unusual seral phenomena and the aggregated non-functional lymphocytes surrounding the tumor nest. Anthor factor affecting the cellular immunity is the presence of soluble interleukin-2 receptor (sIL-2R) that will compete with the membrane-bound IL-2R and desensitize the immune response. With these leads, the authors will discuss the subject ”the role of Epstein-Barr virus infection and the immunocompetence of patients with nasopharyngeal cancer” in the following catogories: EBV-associated diseases and oncogenesis, virus-cell interaction, cell culture model, synergistic effect between viral and other risk factors, latent infection or the reactivated infection, and abrogation of immunocompetence and tumor progression. Hopefully, the discussion will delineate the plausible reason for the decreasing immunocompetence in patients with NPC and will provide a better explanation for the clinical phenomena as well as the theoretical base for the future design of immunotherapy, gene therapy and immuno-gene therapy.