Differential glycosaminoglycan binding of Chlamydia trachomatis OmcB protein from serovars E and LGV

We recently showed that OmcB protein from Chlamydia trachomatis serovar LGV1 functions as an adhesin. In this study, we produced Escherichia coli expressing OmcB from serovar E and compared this OmcB to OmcB from serovar LGV1. Infectivity inhibition assays carried out with serovars LGV1 and E of C. trachomatis in the presence of recombinant OmcB showed considerable (similar to 60%) inhibition of infectivity. In the presence of heparan sulphate, there was significant inhibition (68 %) of adherence of E. coli expressing OmcB from serovar LGV1 only. In a further experiment, recombinant OmcB from serovar LGV1 showed minimal binding to glycosaminoglycan (GAG)-deficient cells, whilst to the same cells, recombinant OmcB from serovar E showed binding equal to that to the wild-type cells. Our experiments strongly suggest that OmcB from serovar E, in contrast to that from serovar LGV1, is not binding to host cells through a GAG-dependent mechanism.