We established an ELISPOT for bovine interferon-gamma (BoIFN-γ), and applied it in the diagnosis of bovine tuberculosis (bTB). Monoclonal antibodies that can bind with native BoIFN-γ were screened as the coating antibody and detecting antibody. After optimization of detecting conditions including coating antibody concentration, cell number, and detecting antibody concentration, the ELISPOT assay was established. Peripheral mononuclear cells (PBMCs) isolated from 30 cows were co-cultured with PPD, and detected with the ELISPOT assay. The optimal conditions of ELISPOT assay were 2.5 μg/mL coating antibody 2G5, 2.5 x 10(5) cells/well, and 1 μg/mL detecting antibody Bio-5E11. In these 30 cows tested both with the ELISPOT assay and the BOVIGAM kit, 11 cows were proved to be positive in ELISOPT assay with the sensitivity of 78.6%, and 12 cows were proved to be negative in ELISOPT assay with the specificity of 75%. The ELISPOT assay for BoIFN-γ could be used to detect bTB efficiently and it might be an alternative method for the diagnosis of bTB.
Animals ; Antibodies, Monoclonal ; Cattle ; Enzyme-Linked Immunospot Assay ; veterinary ; Female ; Interferon-gamma ; isolation & purification ; Sensitivity and Specificity ; Tuberculosis, Bovine ; diagnosis

Bovine interferon-gamma (BoIFN-gamma) gene was amplified by reverse transcription polymerase chain reaction (RT-PCR) from total RNA of bovine spleen lymphocytes stimulated with ConA. The products of RT-PCR were cloned into pVAX1 vector, positive recombinant clone was identified by restriction enzyme digestion and sequencing. The recombinant plasmid pVAX1-BolFN-gamma was transfected into COS-7 cells mediated by lipofectine, indirect immunofluorescent assay analysis confirmed that rBoIFN-gamma was expressed in COS-7 cells. BoIFN-gamma gene (without signal peptide) was cloned into pET-30a(+) and pGEX-6p-1 vector, and transformed into the Escherichia coli cells. After optimizing the induction condition, SDS-PAGE analysis showed that the expression products were all found in soluble form and had a molecular weight of 23 kDa and 43 kDa respectively. BoLFN-gamma precursor gene (with signal peptide) was cloned into transfer vector pFastBac 1, and transformated into DH10Bac E. coli cells. By site-specific transposition, BoIFN-gamma gene was integrated into shuttle vector Bacmid, and transfected into the Sf9 insect cells mediated by lipofectine to produce recombinant baculovirus. Indirect immunofluorescent assay analysis confirmed that rBac-BoLFN-gamma was expressed successfully in Baculovirus vector system. The antiviral activities of rHis-BoIFN-gamma, rGST-BoIFN-gamma and rBac-BoIFN-gamma were up to 8.389 x10(7) U/mg, 6.554 x10(5) U/mg and 4.096 x 10(4) U/mL respectively, which were analyzed in MDBK/VSV system. A sandwich ELISA was established using monoclonal antibodies 3E6 and 5G4, which can detect BoIFN-gamma in quantity and provide a useful method for the clinical practice and research of BolFN-gamma.
Animals ; Antiviral Agents ; pharmacology ; Baculoviridae ; genetics ; metabolism ; COS Cells ; Cattle ; Cercopithecus aethiops ; Escherichia coli ; genetics ; metabolism ; Genetic Vectors ; genetics ; Interferon-gamma ; biosynthesis ; genetics ; pharmacology ; Recombinant Proteins ; biosynthesis ; genetics ; pharmacology ; Transfection