[Preparation antibodies against recombinant bovine IFN-gamma and development of sandwich ELISA for bovine IFN-gamma detection].

This study was aimed to establish ELISA for recombinant bovine IFN-gamma (BovIFN-gamma) detection and provide a new method for diagnosis of pathogenic infection. The total RNA was isolated from peripheral blood leucocytes cultured with PHA mitogen stimulation. Then bovine IFN-gamma (BovIFN-gamma) gene cDNA was amplified by RT-PCR and cloned into pET28a to obtain the expression plasmid designated as pETBovIFN-gamma. The pETBovlFN-gamma was further transformed into competent E. coli BL21 cells and a 18kD His-tagged protein as expected was expressed after IPTG induction. By using purified recombinant BovIFN-gamma as antigen and lymphocyte-hybridoma technique, four hybridoma cell lines which stably secreted monoclonal antibodies against rBovIFN-gamma were generated, designated as A7, A10, G6, and G10. The immunoglobin subset was identified as IgG1 . Western-blotting analysis and ELISA demonstrated that the monoclonal antibodies secreted by all the four hybridoma cell lines could react specifically to the recombinant BovIFN-gamma, but not irrelative proteins such as Ag85B, ESAT-6-CFP-10 and GM-CSF, suggesting that the four hybridoma cell lines were rBovIFN-gamma specific monoclonal antibodies. A sandwich ELISA was established by using A10 secreted monoclonal antibody and rabbit polyclonal antibodies against BovIFN-gamma, HRP labeled goat anti-rabbit IgG. The results indicated that the sensitivity was 2ng/mL. This sandwich ELISA to detect BovIFN-gamma paved the way to develop a sensitive method for specific infection detection such as bovine tuberculosis diagnosis.

[Expression of hemagglutinin of avian influenza virus (AIV) and its application in diagnosis of AIV H9 subtype].

In order to differently diagnose avian influenza virus (AIV) subtypes, the HA gene of AIV H9 subtype was cloned, expressed and utilized in an enzyme-linked immunoad sorbent assay (ELISA). HA gene (1683bp) of H9N2 AIV was amplified by RT-PCR from a strain of field isolated H9N2 AIV, and its identity was confirmed by sequencing. The HA gene was subcloned into prokaryotic expression vector pGEX-KG with its secretion signal sequence removed. The expressed HA-GST fusion protein in E. coli BL21 was characterized by SDS-PAGE and western blotting analysis as a 90kD protein with immunogenicity. The fusion protein was present primarily in inclusion bodies and was purified via denaturation and renenaturation. The HA-GST fusion protein was used to establish an indirect ELISA for the detection of antibodies to H9 subtypes of AIV. The assay has 91.57% specificity to H9 AIV, 92.31% sensitivity and excellent reduplication. It could be used to differently detect antibodies to H9 AIV.