Different humoral immune response to Chlamydia trachomatis major outer membrane protein variable domains I and IV in Chlamydia-infected patients withor without reactive arthritis

Objective. The possibility that some bacterial-specific factor(s) may play a role in triggering Chlamydia trachomatis reactive arthritis was investiga ted. Methods, Since the variable domains of the major outer membrane protein (MO MP) contain the serovar-determining epitopes of C trachomatis, the ability of serum IgG to recognize peptides mimicking these epitopes was determined in 2 groups of infected patients, one with and the other without reactive a rthritis. Because asymptomatic C trachomatis infections are frequent, and n onspecific reactions due to inflammation could be observed, this study was also performed with samples from healthy blood donors and from patients wit h inflammatory arthritis unrelated to C trachomatis infection. Results, A predominant reactivity against peptides duplicating the J serova r-specific epitopes was only observed in the group of patients with reactiv e arthritis. For positive samples, differences between the two groups of C trachomatis-infected patients were clearly observed. The mean numbers of po sitive responses obtained for each of the 7 peptides of the MOMP domain I o r each of the 8 peptides of the MOMP domain IV were significantly higher fo r samples from patients with reactive arthritis (4.7 and 6) than for those from patients with only C trachomatis urogenital infection (1.3 and 2.9). Conclusion. Patients with reactive arthritis had a pattern of reactivities that was compatible with infection by several serotypes of bacteria. Repeat ed exposures to C trachomatis might therefore be involved in the developmen t of the disease.