Serological diagnosis of canine leptospirosis using a chimeric protein based on bacterial surface antigens

Leptospirosis, caused by pathogenic spirochetes of the genus Leptospira, is a re-emerging infectious disease of global significance that poses serious challenges to both human and veterinary health. Advances in diagnostic methods are essential to better understand the complex epidemiology of leptospirosis and to control its transmission, particularly from subclinically infected reservoir hosts. In this context, the use of recombinant proteins in serological diagnostics has emerged as a promising alternative to overcome the limitations of current methods for diagnosing canine leptospirosis.

This study aimed to produce a recombinant chimeric protein derived from leptospiral membrane proteins for use in serological diagnosis of canine leptospirosis.

The rLEPTO1 protein was designed based on surface proteins relevant to Leptospira infection and evaluated using enzyme-linked immunosorbent assay (ELISA) to detect IgM and IgG antibodies in canine serum samples. A total of 120 serum samples were included. Of these, 113 had been previously classified by MAT (IgG: 59 MAT-positive and 52 MAT-negative; IgM: 53 MAT-positive and 54 MAT-negative). In addition, seven serum samples from clinically healthy dogs were included as negative controls and analyzed in both assays.

rLEPTO1 demonstrated a significant ability to discriminate between MAT-positive and MAT-negative samples, detecting IgM and IgG antibodies with sensitivity and specificity of 74.58% and 94.92%, respectively, for IgG-ELISA, and 73.58% and 93.44%, respectively, for IgM-ELISA. Higher sensitivity was observed in samples with elevated MAT titers, consistent with increased antibody levels in these samples.

The rLEPTO1 protein effectively distinguished positive from negative serum samples by ELISA, showing good specificity and moderate sensitivity, and supports its potential as a complementary tool for the serological diagnosis of canine leptospirosis.