Detection of anti-leptospiral antibodies in the serum of animals using recombinant Leptospira GroEL-based latex agglutination test.

Leptospirosis is a global zoonosis with significant implications for public and animal health. Effective diagnosis and timely intervention are crucial for preventing severe complications and managing chronic carriage of pathogenic Leptospira infection in animals. The heat shock protein GroEL of Leptospira has been identified as a promising candidate due to its ability to elicit high antibody responses and provide long-lasting immunity in both acute and chronic phases of infection. This study explores the diagnostic potential of recombinant GroEL (rGroEL) protein in a Latex Agglutination Test (LAT) for detecting anti-leptospiral antibodies in the sera of animals. The groEL coding gene, devoid of its signal peptide, was amplified from pathogenic Leptospira interrogans serovar Hardjprajitno, cloned into a pETite vector, and expressed in Escherichia coli. Characterisation of the expressed rGroEL protein was carried out by SDS-PAGE and Western blot, which confirmed its specific molecular weight of ∼60 kDa protein. Ni-NTA purified rGroEL protein was used to adsorb latex beads, for preparing the sensitized beads which were then assessed as diagnostic antigen in LAT (rGroEL-LAT). Evaluation against the Microscopic Agglutination Test (MAT) revealed a relative diagnostic sensitivity (DSn) of 95.69 % and specificity (DSp) of 93.13 % with an accuracy of 94.33 % for detecting anti-leptospiral antibodies in the sera of animals. This is the first study to utilize the rGroEL protein in a latex agglutination test (rGroEL-LAT), which offers a simple, rapid, and effective screening test. With further exhaustive validation, rGroEL-LAT has the potential to be implemented as a diagnostic tool at field-level laboratories with resource-limited settings.