Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 1998
Publication Date: N/A
Interpretive Summary: Healthy pigs are able to resist infections because they quickly mount an protective immune response. Cytokines such as porcine interferon-gamma (PoIFN-g) are major factors in these protective responses against viral and protozoan parasitic infections. This manuscript describes the development of five monoclonal antibodies (mAbs) for PoIFN-g and the development of a sensitive, specific PoIFN-g sandwich ELISA. Assays confirmed that these mAb reacted with PoIFN-g, but not with rPoIL-2 or rPoIL-10, and that 3 mAbs were able to neutralize PoIFN-g bioactivity. Use of the sandwich ELISA tests showed that peripheral blood mononuclear cells (PBMC) from all pigs tested produced IFN-g when stimulated with mitogen but only PBMC obtained from pigs which had previously been vaccinated against pseudorabies virus (PrV) produced IFN-g in response to stimulation with this virus. Thus, measurements of IFN-g production appears to be a good indicator of anti- viral immunologic memory. Future tests will determine whether measurements of IFN-g levels will be predictive of protection against parasitic infections. Because the reagents for this assay will be widely available, this test could be used by many scientists to determine whether IFN-g is produced in other swine diseases or after specific vaccinations.
Five monoclonal antibodies (mAbs) specific for porcine interferon-gamma (PoIFN-g) were isolated and utilized to develop a PoIFN-g sandwich ELISA. Specific reactivity of each mAb with E. coli derived recombinant PoIFN-2, but not with rPoIL-2 or rPoIL-10, was confirmed in an indirect ELISA and in Western blots. Competitive ELISA's showed that mAbs P2A4 and P2C11 bound an epitope which was not recognized by mAbs P2G10, P1B7 or P2F6. The latter three mAbs were able to neutralize the ability of natural and recombinant PoIFN-g to induce the de novo expression of class II MHC antigens on porcine endothelial cells. To simplify the detection of biologically active porcine IFN-g, a sandwich ELISA was developed using the mAb P2G10 as a capture antibody and mAb P2C11 as the detecting reagent. The sensitivity of the assay for PoIFN-g ranged from 1 to 50 ng/ml. Peripheral blood mononuclear cells (PBMC) from all pigs tested produced IFN-g when stimulated with either mitogen (PHA) or superantigen (SEB). In contrast, only PBMC obtained from pigs which had previously been vaccinated against PrV produced IFN-g in response to stimulation with this virus. Interestingly, cultures with the highest lymphoproliferative response did not necessarily have the highest level of IFN-g production. Furthermore, for recall viral antigen, the lymphoproliferative response decreased with time after immunization, whereas the IFN-g response increased. Thus, measurement of IFN-g production appears to be a good indicator of anti-viral immunological memory.