Sequences of VS-spanning synthetic peptides tested in this study. Synthetic peptides spanning three of the four MOMP VSs and used in our experiments are shown. VSs as described by Kaltenboeck et al. (11) are delimited by vertical bars. Amino acids shared by serovar E and other serovars are in boldface. Peptides that stimulated Th cells primed with the serovar E MOMP are shown as filled bars, and nonstimulatory peptides are shown as unfilled bars. VSs of different serovars exhibit substantial differences in amino acid composition while containing short segments of conserved amino acids (boldface). In addition, insertions of one or two amino acids within VSs of some non-E serovars have the effect of displacing segments of conserved amino acids in the C-terminal direction relative to the serovar E sequence. The stimulatory epitope of peptide 47-67 is within CS1 and is not VS specific, while the other five stimulatory peptides contain VS-specific epitopes (see text).

Serovar-specific responses of T-MOMP′ cells to MOMP VS peptides. T-MOMP′ cells were primed in vitro with serovar E MOMP, and proliferation assays were performed as described in the legend to Fig. 2. The responses to the serovar E peptides were compared with those to the corresponding peptides derived from serovars F, I, and J. Tetanus toxoid (TT) was used as a negative control for antigen (Ag) specificity, and MOMP CS peptide 249-265 was used as a positive control, to which a great majority of infected subjects respond regardless of the infecting serovar. HLA class II-matched LCLs derived from the following subjects were used as APCs: A and E, STD76; B, STD27; C, STD43; D and G, STD70; F, STD36. Absence of error bars indicates standard deviations too small to show on the scale used. ∗, 0.01 < P < 0.025; ∗∗, 0.001 < P < 0.01; ∗∗∗, P < 0.001.

Identification of Th cell-stimulatory peptides located in MOMP VSs. Proliferation of T-MOMP′ cells in response to synthetic peptides that overlap MOMP VS segments by at least seven amino acids (Fig. 1) is shown. T-MOMP′ cells primed in vitro with the C. trachomatis serovar E MOMP were tested in proliferation assays as previously described (14). Data shown for STD 70 were obtained with T-MOMP′ cells prepared from three independent blood samples (C, D, and E). HLA class II-matched LCLs derived from the following C. trachomatis-infected subjects were used as APCs as follows: A, STD 32; B and G, STD 76; F, STD 36; G, STD 76; H, STD 27. In addition, an LCL from uninfected control subject STD 64 was used as APCs for C, D, and E. The statistical significance of differences in [³H]thymidine incorporation in the presence and absence of peptides was evaluated with Student's t test corrected for small sample numbers and unequal variances. ∗, 0.025 < P < 0.05; ∗∗, 0.01 < P < 0.025; ∗∗∗, P < 0.01. Absence of error bars indicates variances too small to show on the scale used. Ag, antigen.