Characterisation of outer membrane protein of Leptospira borgpetersenii serovar Hardjo

Outer membrane protein (OMP) from Leptospira borgpetersenii serovar Hardjo, grown under different cultural conditions, was extracted and characterized for its polypeptide composition and serodiagnostic ability. SDS-PAGE revealed that the detergent insoluble (SI) fraction of OMP from cells grown at the ideal temperature (29C) composed of 5 major polypeptide bands (77, 42.6, 36, 28.8 and 22.5), 4 minor bands (59.5, 47.4, 41.6 and 32 kDa) and 3 very faint bands. In the soluble fraction (SS), different bands were visible, of these 32 kDa and 41 kDa proteins Were the most prominant. Cells grown at 22C did not express the minor 18 kDa protein but over expression of 77 kDa was observed. Growth at 38C did not express any additional protein but an enhanced expression of a 31 kDa protein was visible. Change in iron concentration in culture medium did not change the protein profile. Use of OMP as an antigen for conducting ELISA on convalescent animal sera (1:100) revealed that as compared to Microscopic Agglutination Test, it had a Sensitivity and specificity of 100% and 86.4%, respectively.