USE OF SYNTHETIC ANTIGENS IMPROVES DETECTION BY ENZYME-LINKED-IMMUNOSORBENT-ASSAY OF ANTIBODIES AGAINST ABORTIGENIC CHLAMYDIA-PSITTACI IN RUMINANTS

Synthetic peptide antigens were prepared for use in enzyme-linked immu nosorbent assays (ELISAs) to detect serum antibodies against abortigen ic strains of Chlamydia psittaci in livestock, Peptide antigens were i dentified with C. psittaci B577-immune sera by solid-phase scanning of overlapping octapeptides of variable domains (VDs) of the major outer membrane protein of C. psittaci serovar 1 (omp1 type C. psittaci B577 ), Two VD 4 regions and one VD 2 region were strongly reactive with al l C, psittaci B577 antisera, Peptides encompassing these regions were synthesized with biotin and a serine-glycine-serine-glycine spacer at the N terminus and were attached to streptavidin-coated microtiter pla tes, In direct ELISAs with these plates, the synthetic peptides reacte d with C, psittaci B577 antisera, but not with sera from specific-path ogen-free animals. Serum specimens from 40 sheep and 40 cattle, obtain ed from herds with abortion problems, were screened for antibodies by these C, psittaci B577 peptide ELISAs and an ELISA with recombinant, g enus-specific Chlamydia lipopolysaccharide (LPS) antigen, Results from these newly developed ELISAs were compared to those from the referenc e C, psittaci B577 elementary body (EB) ELISA and the Chlamydia comple ment fixation test (CFT), The C, psittaci B577 peptide ELISAs, the LPS ELISA, and the EB ELISA correctly identified the presence or absence of antibodies against chlamydiae in all sheep and bovine sera, The Chl amydia CFT, which is the most widely accepted serodiagnostic method fo r chlamydial infections in animals, correctly identified the presence or absence of antibodies against chlamydiae in only 78 and 4.9% of she ep and bovine sera, respectively, These results suggest that the C, ps ittaci B577-peptide and Chlamydia LPS ELISAs are superior for the sero diagnosis of ruminant infections with abortigenic chlamydiae, since th ey are more sensitive than the CFT, they are easy to standardize, and they use readily available synthetic antigens instead of organism-deri ved CFT antigen.