Antigenic and immunogenic changes due to mutation of sgene of HBV

AIM: To investigate the change of immunological characteristics of HBsAg caused by the mutation at codon 145 of HBsAg using DNA-based immunization.METHODS: Plasmids expressing mutant and wild type envelope antigens were transfected into human hepatocellular carcinoma cells via electrotransformation. The antigenicity of HBsAg was studied with EIA and immunocytochemical staining. Then plasmids were used to immunize 5 C57BL/6 mice. Sera of mice were detected for anti-HBs and anti-preS2with ELISA. RESULTS: The mutant HBsAg could be detected by native antibody in EIA and immunocytochemical study. But the A(450nm) value of the mutant HBsAg in the supernatant was apparently lower than that of the wild-type. Both mutant and native HBsAg expression plasmid could stimulate a strong humoral immune response to HBsAg and preS2 antigen in mice. Protective antibodies against HBsAg elicited by the native HBsAg occurred earlier than that elicited by the mutant HBsAg about one to two weeks. The occurrence of protective antibodies against preS2 antigen was one to two weeks earlier than that of anti-HBs.CONCLUSION: The amino acid substitution causes changes of the antigenicity and immunogenicity of HBsAg, but mutant HBsAg can still induce a protective humoral immune responsein mice.

Fas ligand expression in colon cancer:A possible mechanism of tumor immune privilege

AIM: To detect the expression of Fas ligand (FasL) in colon cancer tissues and cell lines and analyze the function of FasL-expressing colon cancer cells in inducing Fas-sensitive T lymphocyte apoptosis. METHODS: Ninety surgically resected colon cancer tissues and 15 hepatic metastasis specimens were investigatedby immunohistochemical method with normal colon mucosa and colon adenoma as control. The relationship between FasL expression and pathologic features was also analyzed.FasL expression of 4 colon cancer cell lines, SW620, Lovo, LS-174T and SW1116, were detected by Western blotting assay. The function of FasL expressed on colon cancer cells was determined by coculture assay with Jurkat T lymphocytes, the apoptotic rate of which was detectedby flow cytometry assay.RESULTS: Fifty-six (62.22%) cases of all the 90 colon cancer tissues and all (100%) the liver metastasis specimens expressed FasL, significantly higher than normal colon mucosa and colonic adenoma. Higher expression of FasL was found in more advanced stage of colon cancer and in cancer tissues with lymphatic or hepatic metastasis.All the colon cancer cell lines were found to express FasL.After coculture with the SW1116 cells for 24 h with an effector: target ratio 10:1, the rate of apoptosis of Jurkat cells rose from 1.9% to 21.0%.CONCLUSION: The expression of FasL is upregulated in colon cancer and the functionally expressed FasL can induce apoptosis of Fas-expressing T lymphocytes.