Heterogeneity within the first constant segment of the major outer membrane protein gene in Chlamydia trachomatis serovar D/Da distinguishes 2 lineages.

Restriction fragment length polymorphism of the major outer membrane protein gene (ompl) was studied in 73 epidemiologically unrelated Chlamydia trachomatis serovar D (n = 64) and Da (n = 9) strains isolated between 1983 and 1991 in various european countries from patients suffering from sexually transmitted diseases, as well as 3 reference strains D/IC-Cal-8 (USA), D/UW3 (UK) and Da/TW-448 (Taiwan). Among these strains, 5 different genotypic groups were distinguished: 3 for the serovar D strains and 2 for the serovar Da strains. Comparisons of the complete ompl nucleotide sequence of 1 member of each group revealed 2 distinct lineages, independently of the D/Da classification, presumably as the result of an intragenic DNA recombination event within the first constant segment. The observed ompl genetic diversity of serovar D/Da strains in regions involved in T- and B-cell responses might add another level of complexity to the design of a subunit vaccine.