Characterisation of the Proteome of Leptospira interrogans Serovar Canicola as a Resource for the Identification of Common Serovar Immunogenic Proteins

Over 230 serovars of Leptospira interrogans have been identified; however few have been completely characterised. The aim of this study was to characterise the proteome of serovar Canicola and to compare this against the serovars of Copenhageni and Pomona. 2D-LC/MS analysis identified 1653 Leptospira proteins in serovar Canicola; 60 of these proteins were common to Copenhageni and Pomona, 16 of which are known to be immunogenic. This study provides the first reported proteome for serovar Canicola and suggests that proteomic comparison of different serovars could be used as a tool for identification of novel target molecules for vaccine development. 1. Introduction L. interrogans is a spirochete responsible for leptospirosis and Weil’s disease. Over 230 pathogenic serovars have been identified [1], each potentially fatal if left untreated. Leptospirosis continues to be a significant threat to food producing animals; in 2010 of the 8,681 suspected serum samples examined in the UK by the Animal Health and Veterinary Laboratories Agencies (AHVLA) 2,946 [2] were identified as being seropositive for Leptospira. Approximately 59% (1736) of these seropositive samples were derived from dogs and the majority of these (69%) were positive for serovar Canicola, which to date has not been fully characterised using genomics or proteomics. Whilst the mortality rate associated with leptospirosis remains low, due to its susceptibility to antibiotics [3] and the routine vaccination of domestic and farm animals, initial clinical signs such as cessation of milk production and miscarriage [4] can be commercially damaging to the dairy farming industry. Vaccination represents an effective treatment strategy for prevention of the disease; however the vaccines currently available are all serovar specific. Serological methods for identification of Leptospira serovars, such as the microscopic agglutination test (MAT), are well established. Whilst being effective these are extremely time consuming and require access to a large Leptospira strain/antiserum collection [5], to which many third world countries do not necessarily have access; this in conjunction with the limited public profile of leptospirosis often leads to misdiagnosis and general under reporting of infection. In addition false positive results using the MAT have been reported due to the prior vaccination of test subjects [6]. Genetic classification systems for L. interrogans are not routinely utilised as genetically different species are often found to be serologically identical [5] which leads to poor reproducibility