[Development of new methods for the diagnosis of nasopharyngeal carcinoma].

OBJECTIVE: Development of new methods, ELISA and immunostrip test, for the diagnosis of nasopharyngeal carcinoma. METHODS: The engineering purified antigens coat plate or absorb on nitrocellulose filter. The plate and diagnostic strips carrying antigens were used for detection of IgG antibody in the sera from nasopharyngeal carcinoma patients and outpatients patients. RESULTS: 127 cases sera from nasopharyngeal carcinoma patients were parallel detected TK/IgG antibody by ELISA and immunostrips. The TK/IgG antibody are all positive in the 127 cases of nasopharyngeal carcinoma patients. 55 cases show positive by ELISA, 58 cases positive by immunostrips in 247cases sera from outpatient. The antibody positive rate to early antigen p54 lower then to TK. Conclusion ELISA and imuunostrips are sensitive and specific means for detection of the IgG antibody to TK of EBV and the diagnosis of nasopharyngeal carcinoma.

Preparation of monoclonal antibody against HPT and its application to detecting marker protein in genetically modified rice.

OBJECTIVE: To produce the monoclonal antibodies (mAbs) against hygromycin B phosphotransferase (HPT) and to develop immunoassay based on mAbs for biosafety assessment of HPT in genetically modified rice (GM rice). METHODS: BALB/c mice were immunized with purified recombinant 6His. HPT protein, and the conventional hybridoma technology was used to generate the monoclonal hybridoma cells. ELISA and Western blot were used to analyze the specificity of mAbs recognizing HPT and the cross reaction with other proteins. A double-Ab sandwich ELISA method was established to detect HPT expression level in the sck gene-modified rice plants. RESULTS: Four hybridomas, named F1, D4-2, D4-4, and D4-5, producing the mAbs against HPT were successfully obtained with the titer of ascetic mAbs ranging from 1x10(-4) to 1x10(-5). Identification of subclass showed that all the produced mAbs belonged to IgG1. Western blot showed specific binding reaction between the mAbs to the HPT proteins expressed in the GM rice. A double sandwich ELISA coated with anti-HPT polyclonal antibody was established with mAbs as sandwich antibody, which showed a sensitivity of 30ng/mL and did not crossreact with other proteins. The expression level of HPT in the leaves of sck-transformed lines was detected (80-150ng/mL). But HPT protein in the grain and seed of GM rice could not be detected using this ELISA assay. CONCLUSION: Anti-HPT mAbs prepared herein have a high specificity and can be used for rapid assay of HPT antigen. The expression level of HPT in the GM rice grain and seed is lower than our ELISA detection limit.

Stability of SARS coronavirus in human specimens and environment and its sensitivity to heating and UV irradiation.

OBJECTIVE: The causal agent for SARS is considered as a novel coronavirus that has never been described both in human and animals previously. The stability of SARS coronavirus in human specimens and in environments was studied. METHODS: Using a SARS coronavirus strain CoV-P9, which was isolated from pharyngeal swab of a probable SARS case in Beijing, its stability in mimic human specimens and in mimic environment including surfaces of commonly used materials or in household conditions, as well as its resistance to temperature and UV irradiation were analyzed. A total of 10(6) TCID50 viruses were placed in each tested condition, and changes of the viral infectivity in samples after treatments were measured by evaluating cytopathic effect (CPE) in cell line Vero-E6 at 48 h after infection. RESULTS: The results showed that SARS coronavirus in the testing condition could survive in serum, 1:20 diluted sputum and feces for at least 96 h, whereas it could remain alive in urine for at least 72 h with a low level of infectivity. The survival abilities on the surfaces of eight different materials and in water were quite comparable, revealing reduction of infectivity after 72 to 96 h exposure. Viruses stayed stable at 4 degrees C, at room temperature (20 degrees C) and at 37 degrees C for at least 2 h without remarkable change in the infectious ability in cells, but were converted to be non-infectious after 90-, 60- and 30-min exposure at 56 degrees C, at 67 degrees C and at 75 degrees C, respectively. Irradiation of UV for 60 min on the virus in culture medium resulted in the destruction of viral infectivity at an undetectable level. CONCLUSION: The survival ability of SARS coronavirus in human specimens and in environments seems to be relatively strong. Heating and UV irradiation can efficiently eliminate the viral infectivity.

[Expression, purification and diagnostic application of EBV TK kinase].

BACKGROUND: To find a rapid and sensitive method for early diagnosis of nasopharyngeal carcinoma by using EBV TK kinase. METHODS: Prokaryotic expression plasmid pRSETTK was constructed. EBV TK kinase was highly expressed in E.coil BL21 (DE3). The authors identified specificity of TK kinase by Western blot, then used purified TK kinase in ELISA to detect the IgG antibody in the serum of NPC patients. RESULTS: Specific IgG antibody against TK kinase was found in the serum of NPC patients. The specificity and sensitivity of TK kinase were both 100% in Western blot and were 98.0% and 93.4% respectively in ELISA. CONCLUSIONS: The EBV TK kinase showed high specificity and sensitivity in ELISA, therefore it can be used for early diagnosis of NPC