DETECTION OF SPECIFIC ANTIBODIES DIRECTED AGAINST A CONSISTENTLY EXPRESSED SURFACE-ANTIGEN OF MYCOPLASMA-GALLISEPTICUM USING A MONOCLONAL BLOCKING ENZYME-LINKED-IMMUNOSORBENT-ASSAY

Sera from 14 groups of chickens inoculated with different laboratory a nd field strains of Mycoplasma gallisepticum (MG) were used to compare the diagnostic potential of the hemagglutination-inhibition (HI) test and a recently developed monoclonal blocking enzyme-linked immunosorb ent assay (ELISA). HI was performed with strain A5969, commonly used a s hemagglutinating antigen, and it could detect 62.7% of the inoculate d chickens as positive. Of all sera, 83% proved to be positive when ex amined with the blocking ELISA. The difference between the sensitiviti es of the two methods was due to group-specific insensitivity of the H I test. None of the sera from groups inoculated with strains K 1501, K 1503, K 503, or K 703 and only half of the sera hem groups inoculated with K 1453 or 236C could inhibit the activity of the A5969 hemagglut inating antigen, indicating antigenic differences between these challe nge strains and the diagnostic strain. ELISA detected MG-specific anti bodies in every group of sera, although inoculation with variant strai ns K 503 or K 703 resulted in lower level of antibody production than inoculation with other strains. The monoclonal blocking ELISA can be u seful in the serological diagnosis of MG infections, because it is bas ed on a consistently expressed, specific region of MG.