Chlamydia trachomatis antigens recognized in women with tubal factor infertility, normal fertility, and acute infection

Abstract

Objective: To identify Chlamydia trachomatis antigens associated with tubal factor infertility and acute infection.

Methods: A C trachomatis proteome array was used to compare antibody profiles among women with tubal factor infertility, normal fertility, and acute C trachomatis infection.

Results: Thirteen immunodominant antigens reacted with 50% or more sera from all women (n=73). Six C trachomatis antigens were uniquely recognized in women with tubal factor infertility. Combining fragmentation of the six antigens with serum sample dilution, chlamydial antigens HSP60, CT376, CT557, and CT443 could discriminate between women with tubal factor infertility and women with normal fertility with a sensitivity of 63% (95% confidence interval [CI] 0.41-0.77) and specificity of 100% (95% CI 0.91-1), respectively. These antigens were designated as tubal factor infertility-associated antigens. However, these tubal factor antigens were unable to distinguish tubal factor infertility patients from those with acute infection. A combination of CT875 and CT147 distinguished women with acute infection from all other C trachomatis-exposed women with a detection sensitivity of 63% (95% CI 0.41-0.77) and specificity of 100% (95% CI 0.95-1), respectively. Thus, CT875 and CT147 were designated as acute infection-associated antigens.

Conclusion: A sequential screening of antibodies against panels of C trachomatis antigens can be used to identify women with tubal factor infertility and acute C trachomatis infection.

Level of evidence: II.

Fig. 1. Reactivity of 908 C. trachomatis fusion proteins with 73 sera from 3 different groups of women

GST fusion proteins representing 908 C. trachomatis ORFs were each reacted with serum samples from women with tubal factor infertility (TFI in red, n=24), normal fertility (FC in yellow, n=25), or acute infection (STI in green, n=24). Any reaction with an OD ≥ mean + 2 SDs calculated from the same plate was determined positive, which was used to calculate positive recognition frequency (Freq). The positive OD values were expressed as binding intensity in increasing brightness of fluorescent color while the negative OD values were always in black, as indicated at the bottom of panel D. The 908 ORFs encoded by C. trachomatis genome and plasmid were listed first in order of ORFs from CT001 to pCT08 (panel A), and then in order of recognition frequency from high (H) to low (L) (panels B–D).

Fig. 2. Reactivity patterns of antigens preferentially recognized by TFI women with serum samples from STI women

Antigens HSP60, CT376, CT557, CT443FL (full length), and CT443F11 (fragment 11; X-axis) were reacted with each of the 73 human sera from tubal factor infertility (TFI, panels a & b), fertile control (FC, panels c & d) and sexually transmitted infection (STI, panels e & f) groups (Y-axis). The human sera were used at either 1:1000 (panels a, c and e) or 1:10,000 (b, d and f) dilution. Each horizontal bar indicates a positive reactivity as determined based on the mean plus 2 standard deviations. Unique reactivities between an antigen and a TFI serum are marked with stars. The reactivity frequencies of CT443FL and CT443F11 with TFI (panles a & b) and FC (panel c) sera were marked accordingly. Note that antigens preferentially recognized by TFI sera were also highly reactive with STI sera.

Fig. 3. Reactivity patterns of 13 antigens with STI women samples

When human sera were diluted at 1:10,000 dilution, 13 antigens (listed at top and bottom of the figure) completely lost reactivity with either TFI or FC women samples but each maintained certain level of reactivity with STI samples (panel A). The patterns of the reactivity of the 13 antigens with 24 STI samples are shown in panel B. Each horizontal bar indicates a positive reactivity. Sera reacting uniquely with CT875 and CT147 are marked with a star. Please note that CT875 and CT147 (highlighted in bold face) detected 15 out of the 24 STI sera with a sensitivity of 63% while maintaining 100% specificity.

Fig. 4. Diagram for proposed patient testing

Individuals screened positive for antibodies to Chlamydia trachomatis (I^o) will be subjected to a second screen for antibodies to tubal factor infertility (TFI)-associated antigens (Ags; II^o). Those positive for anti-TFI Ag antibodies will be further screened for antibodies to antigens associated with acute infection or sexually transmitted infection (STI; III^o). If positive, these are the acutely infected patients. If negative, the patients likely have tubal factor infertility. Shaded boxes indicate C. trachomatis infection.