Evaluation of the diagnostic potential and DIVA capability of recombinant LigBCon1-5 protein of Leptospira interrogans serovar Pomona in canine leptospirosis

Background: Canine leptospirosis is a serious public health concern. Aims: This study aims to investigate the feasibility of conserved first to fifth domains of recombinant Leptospira immunoglobulin like protein B antigen (rLigBCon1-5) as a serodiagnostic marker for detecting canine leptospirosis. Methods: A total of 340 unvaccinated canine serum samples were screened using microscopic agglutination test (MAT) and rLigBCon1-5 based immunoglobulin G (IgG) indirect-enzyme-linked immunosorbent assay (I-ELISA). Further, 60 vaccinated canine sera were screened using MAT and rLigBCon1-5 based latex agglutination test (LAT). Results: Microscopic agglutination test results revealed seropositivity of 28.6%. The relative sensitivity, specificity, and accuracy of IgG I-ELISA in comparison to MAT were 100%, 96.0%, and 97.2%, respectively. Out of 60 vaccinated sera, 46 sera reacted with MAT alone, and eight sera reacted by both tests, while six sera were non-reactive with both tests. Anti-LigB antibodies were detected in eight canine sera by rLigBCon1-5 based LAT. In five LAT reactive sera, agglutinins of locally circulating Leptospira serovars Grippotyphosa (n=4) and Australis (n=1) were detected. In three LAT reactive sera, agglutinins against Icterohaemorrhagiae (n=3) produced due to natural infection were present. Conclusion: Immunoglobulin G based indirect ELISA assay (IgG I-ELISA) can be employed as an alternative test instead of MAT. rLigBCon1-5 based LAT detected anti-LigB antibodies in eight vaccinated sera where the vaccine failure occurred partially or totally due to the limited efficacy spectrum of Nobivac® RL and cold chain breakage. This vaccine could not provide cross-protection against locally circulating Leptospira serovars. The recombinant LigBCon1-5 antigen based LAT possesses capability of differentiating infected from vaccinated individuals (DIVA capability) when employed as a pen-side test for detecting canine leptospirosis.