T-cell epitopes in variable segments of Chlamydia trachomatis major outer membrane protein elicit serovar-specific immune responses in infected humans.

We previously identified 18 stimulatory Chlamydia trachomatis major outer membrane protein (MOMP) peptides containing at least 23 epitopes presented with various HLA class II allotypes. Only one peptide contained an epitope localized in a variable segment (VS2). Continued studies reported here identified a total of five VS peptides containing T-cell epitopes that are distributed among MOMPs VS1, VS2, and VS4. Only MOMP-primed T-cell cultures from subjects infected with serovar E responded to the serovar E VS peptides, while the response of such cultures to constant-segment peptides was independent of the infecting serovar. Furthermore, MOMP-primed T cells proliferated in response only to the VS peptides encoded in serovar E but not to the corresponding peptides derived from serovar F, I, or J, confirming that these responses were serovar specific.