FIG. 3.

Quantitation of chlamydial protein-specific antibodies in human sera by ELISA. Sera from 10 human patients diagnosed with C. trachomatis urogenital tract infection were examined in an ELISA for levels of antibodies to the fusion proteins GST-CPAF, GST-MOMP, and GST-HSP60. Individual sera were fivefold serially diluted, as indicated along the bottom of the figure, and the results were expressed as mean OD values ± standard deviation. Asterisks indicate statistically significant differences in OD values between CPAF and MOMP antibodies (P < 0.01 at 1:500 and 1:2,500; P < 0.05 at 1:12,500). Statistical analysis was done as described in the legend to Fig. 2. The lysates made from bacteria expressing GST alone were used as negative antigen controls. None of the serum samples showed any significant binding to the control antigens (data not shown).