Development of leptospiral outer membrane protein-based dot-ELISA assays and immunoprofiling for diagnosis of acute canine leptospirosis

The present study was carried out to evaluate outer membrane protein (OMP)-based relatively simple dot-ELISA assays for the diagnosis of acute canine leptospirosis and to identify the differential expression of leptospiral OMPs for identifying the markers of acute infection, if any. Among 91 canine serum samples screened, 63 samples were found to be positive by MAT. All the samples were tested by OMP-based IgM and IgG dot ELISAs. The sensitivities of IgM and IgG dot ELISA in comparison to MAT (titer: >= 1: 400) were found to be 100%, whereas the specificities were found to be 89.71% and 45.31%, respectively. IgM and IgG immunoblotting of OMPs was standardized and tested with the MAT-positive samples. IgM immunoblotting of leptospiral OMP revealed proteins of 18, 21, and 32 kDa as major reactors. With IgG, proteins of 32, 41, and 66 kDa were recognized as major reactors and an 86-kDa protein was identified as a minor reactor. The 32-kDa protein was the predominant reactor in both IgM and IgG immunoblots. Thus, a combination of 18-, 21-, and 32-kDa proteins could be a good choice for the detection of IgM antibodies indicative of acute infection while that of 32-, 41-, and 66-kDa proteins could be employed for seroepidemiological studies.