Genetic basis underlying the serological affinity of leptospiral serovars from serogroups Sejroe, Mini and Hebdomadis

https://doi.org/10.1016/j.meegid.2022.105345Get rights and content
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Highlights

  • Leptospiral samples of serogroup Sejroe share unique genes in the rfb locus.

  • rfb locus of serogroups Sejroe, Mini and Hebdomadis share similar gene organization.

  • The similarity in their rfb locus structure is linked to their serological affinity.

  • rfb locus genes that discern between Sejroe, Mini and Hebdomadis were identified.

  • The finding could aid the leptospiral sero-identification using molecular approach.

Abstract

Leptospirosis is a widely distributed zoonosis caused by pathogenic strains of bacteria of the genus Leptospira (Phylum Spirochaetes). Its agents are commonly classified based on their antigenic characteristics into serogroups and serovars, which are relevant for epidemiologic studies and vaccine development. Serological tests are considered laborious and require a specialized infrastructure. Some molecular methods have been proposed to accelerate these procedures, but they still can not replace the immunological tests, thus requiring a further understanding of the genetic basis underlying the serological classification. In this work, we focused on elucidating the genetic factors determinant for the serogroup Sejroe, which is one of the most prevalent serogroups in livestock. For this, we conducted a comparative analysis using >700 leptospiral genomic samples available in the public database. The analysis showed that the genes comprising the rfb locus are the main genetic factors associated with the serological classification. Samples from the serogroup Sejroe have an rfb locus with a conserved gene composition that differs from most other serogroups. Hebdomadis and Mini were the only serogroups whose samples have an rfb locus with similar gene composition to those from serogroup Sejroe, corroborating with the serological affinity shared by them. Finally, we could determine a small region in the rfb locus in which each of those three serogroups can be distinguished by its gene composition. This is the first work that uses an extensive repertoire of genomic data of leptospiral samples to elucidate the molecular basis of the serological classification and open the road to more reliable strategies based on molecular methods for serodiagnosis.

Keywords

Cross-reactions
Leptospirosis
Lipopolysaccharides
O antigens
rfb locus

Abbreviations

SHM
Sejroe/Hebdomadis/Mini
SVR
SHM rfb variable region

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