Evaluation of a novel outer membrane surface-exposed protein, LIC13341 of Leptospira, as an adhesin and serodiagnostic candidate marker for leptospirosis.

The outer membrane proteins of the pathogen are targeted to understand host-pathogen interactions and are central to the development of diagnostics. We report that Leptospira interrogans serovar Copenhageni strain Fiocruz L1-130 contains a gene LIC13341 that encodes a conserved outer membrane/periplasmic lipoprotein. The gene LIC13341 was cloned into expression vector pET28a and the recombinant LIC13341 (r-LIC13341) protein was purified from Escherichia coli BL21 (DE3) using affinity chromatography. The secondary structure of the purified r-LIC13341 protein featured a typical β-strand when observed by circular dichroism spectroscopy. Immunoblotting using antibodies raised against r-LIC13341 in BALB/c mice can detect LIC13341 expression in the Leptospira lysates and suggested that antigen LIC13341 is immunogenic. Phase separation and protease assays determined that LIC13341 is a surface-exposed outer membrane protein of Leptospira. The r-LIC13341 can bind to a wide spectrum of host extracellular matrices (ECMs). The specific adherence of Leptospira to laminin and hyaluronic acid of the ECM was competitively inhibited in the presence of r-LIC13341. The enzyme-linked immunosorbent assay and immunoblot performed using human or bovine leptospirosis serum (n=50) recognized r-LIC13341, suggesting that LIC13341 is expressed in diverse hosts during Leptospira infection. Thus, the present finding suggests that the Leptospira LIC13341 antigen is a versatile outer membrane adhesin of diagnostic importance.