Expression and immunologic characterization of recombinant heat shock protein 58 of Leptospira species: A major target antigen of the humoral immune response

A clone of Leptospira interrogans serovar lai that was isolated by immunosc reening of a genomic lambda library with sera from convalescent patients wi th leptospirosis directed expression of a unique 62-kDa protein in Escheric hia coli. When examined by SDS-PAGE, the protein comigrated with an immunod ominant protein present in leptospiral cell lysate. Determination of the nu cleotide sequence of the 2.7-kb insert DNA identified two genes homologous to the hsp58 and hsp10 of L. interrogans serovar copenhageni reported previ ously. The overexpressed recombinant Hsp58 protein was purified and used to immunize a rabbit to produce a polyclonal antibody, Immunoblot analysis us ing the rabbit anti-Hsp58 G antibodies showed that the 62-kDa protein was c ommonly present in lysates of other serovars of leptospires, consistent wit h the strong sequence conservation between the hsp58 genes of the two serov ars. Immunoglobulin G antibodies to the Hsp58 were specifically detected by ELISA in 82% of sera (18/22) from patients with leptospirosis. Deletion an alysis of the recombinant Hsp58 protein indicated that a strong antigenic d eterminant for humoral immune response is located between amino acids 360 a nd 380 (DREKLQERLAKLAGGVAVIHV) of Hsp58, which are highly conserved among t he GroEL family. The strong sequence conservation of the Hsp58 among leptos pires and its importance as a major target for the humoral immune response warrant further studies of its potential pathogenetic role.