Complementary activation of peripheral natural killer cell immunity in nasopharyngeal carcinoma.

NK cells and alphabeta- and gammadelta-CTL play important roles in cellular immunity against tumors. We previously demonstrated that NPC patients have a quantitative and qualitative deficit in gammadelta-CTL and EBV-specific alphabeta-CTL when compared to normal subjects and NPC long-term survivors. In this study we report further observations of a complementary activation of peripheral NK cells in NPC patients. The NK cells in these patients, compared to those of healthy subjects and NPC survivors, were preferentially activated in response to the stimulation of myeloma cell line XG-7 and expanded in the presence of exogenous IL-2. The production of IFN-gamma was lowest in the patient group, whereas IL-12, IL-15 and TNF-alpha were produced in higher levels in patients than in the donors and survivors. The cytolytic effect of the NK cells against NPC cells in the patient group was also higher than that of the donors and survivors. Furthermore, the patients at later stages of NPC had lower gammadelta-CTL activity but higher NK cytotoxicity towards NPC targets, with higher production of IL-12, IL-15 and TNF-alpha but lower production of IFN-gamma than in patients at earlier stages. This might be part of a triggered compensatory re-activation of the innate immunity, believed to be mediated through various cytokines and chemokines when adaptive T cell immunity is breached. Together, these data suggest complementary roles of innate and adaptive immune response in tumor immunity where NK cells, gammadelta- and alphabeta-CTL compensate for the deficits of one another at different stages of tumor invasion.

Epstein-Barr virus serology in early detection and screening of nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is a common cancer among Chinese, especially Southern Chinese; except for a few other ethnic groups with moderate incidence, it is otherwise a rare cancer in the world. NPC has a male dominance of about 3:1 and mainly afflicts people in mid-life. There is now compelling evidences to suggest that Epstein-Barr virus (EBV), a category I human tumor virus defined by UICC (International Agency for Research on Cancer) in 1997, is a causal agent of NPC and is most likely to be involved in the multi-step and multi-factorial development of NPC. In this article, the role of EBV in pathogenesis of NPC is reviewed briefly, and principle applications of EBV antibodies and EBV DNA as markers of NPC are outlined. Based on current knowledge of EBV antibody responses by NPC and taking available testing technologies into account, serologic screening strategy to facilitate efficient early detection of NPC is formulated.

Study on sero-diagnosis of nasopharyngeal carcinoma using a dual antibody test against recombinant Epstein-Barr virus antigens.

BACKGROUND & OBJECTIVE: The aim of this study was to optimize a dual-antibody assay for sero-diagnosis of nasopharyngeal carcinoma(NPC) by evaluating 4 Epstein-Barr virus(EBV) antigen-based enzyme-linked immunosorbent assays(ELISAs). METHODS: The serum samples of 57 pretreated NPC patients and 58 apparently healthy adults in Guangzhou were collected. The levels of anti-EBV antibody in the sera were tested by 4 ELISAs, which were developed using fusion proteins of glutathione transferase and EBV specific recombinant antigens, namely, EBNA1-IgA, EBNA1-IgG, Zta-IgA, and Zta-IgG. RESULTS: When evaluated individually, the sensitivity(0.9123) and negative predictive value(0.9074) of EBNA1-IgA were the highest among the 4 ELISAs tested. Zta-IgA test had the highest individual accuracy rate(pi, 0.8870) and Youden index(J, 0.7738). The dual positives for EBNA1-IgA and Zta-IgA were the highest among the 4 dual positives when paired ELISAs were evaluated. Five NPC patients with negative reaction to EBNA1-IgA showed positive reaction of Zta-IgA, and 7 NPC patients with negative reaction to Zta-IgA showed positive reaction of EBNA1-IgA. CONCLUSION: The EBNA1-IgA assay is more suitable than the other 3 ELISAs(EBNA1-IgG, Zta-IgA, and Zta-IgG) when used individually for serological diagnosis of NPC. When two assays are combined, EBNA1-IgA and Zta-IgA have complementary effect on serological diagnosis for NPC and is thus an optimal combination of serum antibody assays.

Peripheral gamma delta T-cell deficit in nasopharyngeal carcinoma.

Previous studies identified CD56(+) and CD56(-) subsets of peripheral gamma delta T cells from healthy donors. Both subsets responded to stimulation by a myeloma cell line, XG-7 and undergo vigorous ex vivo expansion in the presence of exogenous IL-2. They are cytotoxic for different tumor targets including nasopharyngeal carcinoma, but they differ from one another in that the CD56(-) subset has an additional growth requirement for IL-7 and exhibited greater cytotoxicity against nasopharyngeal carcinoma (NPC) targets. These immune cells were further shown to retard tumor growth in a nude mice NPC model. To assess if these immune cells might contribute to host defense against NPC, we compared gamma delta T-cell status of NPC patients with healthy donors and survivors who had been in clinical remission of the cancer. It was found that peripheral gamma delta T cells of patients were impaired in their response to the stimulatory effects of XG-7 and exhibited weak or essentially no cytotoxicity for the NPC targets. The deficits were present in early and advanced stages of the cancer but were restored among survivors after successful treatment of the cancer. These findings support a role for peripheral gamma delta T cells in host defense against NPC. It was noted that these immune cells comprise less than 5% of peripheral blood monocytic cells and hence it was not surprising that this component of host defense was breached early in the development of the cancer.

A single dose of oral DNA immunization delivered by attenuated Salmonella typhimurium down-regulates transgene expression in HBsAg transgenic mice.

The efficacy of immunization with Salmonella typhimurium aroA to deliver the plasmid pRc/CMV-HBsAg (i.e. an oral DNA vaccine) was compared with that of intramuscular immunization with the same plasmid DNA, and with recombinant HBsAg protein, in a HBsAg transgenic mouse model. A single dose of oral DNA vaccine evoked vigorous Th1 cell and CTL responses and production of IgG2 subclass of anti-HBs after 2 weeks, and this was accompanied by a transient hepatitic flare with elevated alanine aminotransferase in the first 3 weeks. Concomitantly, the level of HBsAg-mRNA in liver tissues decreased by more than fourfold and viral-antigen expression was curtailed markedly in hepatocytes compared with controls. Hepatitic flare subsided after 3 weeks, but suppression of the transgene expression was continued in the absence of overt liver pathology for the remaining duration of the experiment (i.e. 12 weeks), and possibly beyond. The other vaccines could also break immune tolerance, but this was achieved only after repeated booster doses of the respective vaccines, and they did not affect transgene expression, or induce hepatic flare. We previously showed in non-transgenic mice that immunization by the oral DNA vaccine is achieved by an active intestinal infection with a bacterial carrier that is an adept intracellular parasite, and the immune response to the vaccination is orchestrated by phagocytic APC. Our present findings further implicated that the combined effects of an innate and a specific immune response induced by oral DNA vaccination are crucial in down-regulating HBsAg-transgene expression in hepatocytes.