Detection of Antibodies by Immunoblotting Using Chlamydia trachomatis Serovars

: We compared reactivity between Chlamydia serovar antigens and sera from 18 patients using immunoblotting (IB) and enzyme-linked immunosorbent assay (ELISA). The antigens used were Chlamydia trachomatis serovar L2, D, E, and C organisms for IB and synthetic peptides derived from C, E, G, and L2-VDIV genes for ELISA. Eleven of 12 sera collected from Chlamydia antigen-positive women with cervicitis strongly reacted with C. trachomatis serovar E, as did one serum with serovar C in immunoblotting profiles. ELISA coated individually with peptides E and C strongly reacted with the sera of 6 different patients. The IB result between serovar L2, D, E, and C and sera from the 6 other women patients showed reactivity at E > or = D > or = L2 > or = C. ELISA using a synthetic peptide mixture including C, E, G and L2 peptides gave positive results for all 18 sera. These results indicate that IB sensitivity differes with the C. trachomatis serovar antigen used and that certain cases may produce inconsistent results between IB and ELISA. Results of ELISA and IB are thus not always consistent, indicating that different synthetic peptides should be used in ELISA for detecting of low-level C. trachomatis antibodies.