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BackgroundLeptospirosis is caused by pathogenic spirochetes of the genus Leptospira spp. This zoonotic disease is distributed globally and affects domestic animals, including cattle. Leptospira interrogans serogroup Sejroe serovar Hardjo and Leptospira borgpetersenii serogroup Sejroe serovar Hardjo remain important species associated with this reproductive disease in livestock production. Previous studies on Brazilian livestock have reported that L. interrogans serovar Hardjo is the most prevalent leptospiral agent in this country and is related to clinical signs of leptospirosis, which lead to economic losses in production. Here, we described the isolation of three clinical strains (Norma, Lagoa and Bolivia) obtained from leptospirosis outbreaks that occurred in Minas Gerais state in 1994 and 2008.ResultsSerological and molecular typing using housekeeping (secY and 16SrRNA) and rfb locus (ORF22 and ORF36) genes were applied for the identification and comparative analysis of Leptospira spp. Our results identified the three isolates as L. interrogans serogroup Sejroe serovar Hardjo and confirmed the occurrence of this bacterial strain in Brazilian livestock. Genetic analysis using ORF22 and ORF36 grouped the Leptospira into serogroup Sejroe and subtype Hardjoprajitno. Genetic approaches were also applied to compare distinct serovars of L. interrogans strains by verifying the copy numbers of the IS1500 and IS1533 insertion sequences (ISs). The IS1500 copy number varied among the analyzed L. interrogans strains.ConclusionThis study provides evidence that L. interrogans serogroup Sejroe serovar Hardjo subtype Hardjoprajitno causes bovine leptospirosis in Brazilian production. The molecular results suggested that rfb locus (ORF22 and ORF36) could improve epidemiological studies by allowing the identification of Leptospira spp. at the serogroup level. Additionally, the IS1500 and IS1533 IS copy number analysis suggested distinct genomic features among closely related leptospiral strains.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-017-1081-9) contains supplementary material, which is available to authorized users.

A severe re-emergingzoonosis, leptospirosis, is caused by pathogenic spirochetes of the genus Leptospira. Several studies have identified leptospiral surface proteins with the ability to bind ECM and plasma components, which could mediate adhesion and invasion through the hosts. It has been shown that Mce of pathogenic Leptospira spp. is an RGD (Arg-Gly-Asp)-motif-dependent virulence factor, responsible for infection of cells and animals. In the present article, we decided to further study the repertoire of the Mce activities in leptospiral biological properties. We report that the recombinant Mce is a broad-spectrum ECM-binding protein, capable of interacting with laminin, cellular and plasma fibronectin and collagen IV. Dose--r-esponse interaction was observed for all the components, fulfilling ligand--receptor requirements. Mce is a PLG binding protein capable to recruit this component from NHS, generating PLA in the presence of PLG activator. Binding of Mce was also observed with the leukocyte cell receptors αLβ2 [(CD11a/CD18)-LFA-1] and αMβ2 [(CD11b/CD18)-Mac-1], suggesting the involvement of this protein in the host immune response. Indeed, virulent Leptospira L1-130 was capable of binding both integrins, whereas culture-attenuated M-20 strain only bind to αMβ2 [(CD11b/CD18)-Mac-1]. To the best of our knowledge, this is the first work to describe that Mce surface protein could mediate the attachment of Leptospira interrogans to human cell receptors αLβ2(CD11a/CD18) and αMβ2(CD11b/CD18).

Um surto de leptospirose foi observado em bovinos leiteiros em Santo Antônio do Monte, Minas Gerais. O rebanho apresentava reações positivas anti-leptospira sorovar Hardjo no teste de microaglutinação (MAT) e havia sido vacinado anteriormente com vacina experimental contendo a sorovariedade Hardjo. O MAT revelou 48,06% dos bovinos positivos para sorovariedade Hardjo genótipo Hardjobovis, 36,82% para sorovariedade Hardjo genótipo Hardjoprajitno. Os animais apresentavam aborto e mastite com presença de sangue no leite. A presente pesquisa teve como objetivos isolar as sorovariedades existentes a partir da urina de vacas sorologicamente positivas, elaborar uma vacina experimental com as sorovariedades isoladas no rebanho, avaliar a eficiência do programa de vacinação por um período de dois anos por meio da sorologia do rebanho. Foi isolada Leptospira spp. a partir da urina de duas vacas com sinais sugestivos da doença. As amostras isoladas foram identificadas pela sorologia com anticorpos monoclonais e seqüenciamento do gene 16S rRNA como pertencentes à espécie Leptospira interrogans, sorogrupo Sejroe, sorovariedade Hardjo e genótipo Hardjoprajitno. O uso da vacina autógena foi eficaz no controle da leptospirose no rebanho no período de dois anos. Os resultados da sorologia revelaram ausência de animais positivos na última prova realizada no rebanho.

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