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Cell wall glycolipids from Corynebacterium pseudotuberculosis strains with different virulences differ in terms of composition and immune recognition.

ABSTRACT: Caseous lymphadenitis (CLA) is an infectious disease caused by Corynebacterium pseudotuberculosis in small ruminants and is characterized by the development of granulomas in the lymph nodes, spleen, liver, and lungs. Although little is known about the host-pathogen relationship of this bacterium, it was previously reported that the pathogen's lipids are important for its taxonomic classification and survival inside macrophages. However, there are no studies regarding the composition of these molecules. In this study, cell wall glycolipids from two C. pseudotuberculosis strains presenting different virulence profiles were purified and its composition was characterized. A difference was observed between the electrophoretic and chromatogram profiles for cell wall components from the two strains, mainly among molecules with low molecular weights. IgM from sheep with acute CLA recognized antigens with an estimated molecular weight of 11 kDa of the low-pathogenicity strain, while low-molecular weight antigens from the high-pathogenicity strain presented a lower recognition by these antibodies. Mass spectrometry analysis showed that the cell wall of the high-pathogenicity strain contained glycolipids with high amounts of unsaturated fatty acids and glycerophosphoinositols, which may contribute to the capacity of this strain to cause severe disease. In conclusion, it is indicated that cell wall non-protein antigens can play a key role in C. pseudotuberculosis virulence.

SUBMITTER: Reboucas MF

PROVIDER: S-EPMC7688822 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Seven genomes of Corynebacterium pseudotuberculosis biovar equi were sequenced on the Ion Torrent PGM platform, generating high-quality scaffolds over 2.35 Mbp. This bacterium is the causative agent of disease known as "pigeon fever" which commonly affects horses worldwide. The pangenome of biovar equi was calculated and two phylogenomic approaches were used to identify clustering patterns within Corynebacterium genus. Furthermore, other comparative analyses were performed including the prediction of genomic islands and prophages, and SNP-based phylogeny. In the phylogenomic tree, C. pseudotuberculosis was divided into two distinct clades, one formed by nitrate non-reducing species (biovar ovis) and another formed by nitrate-reducing species (biovar equi). In the latter group, the strains isolated from California were more related to each other, while the strains CIP 52.97 and 1/06-A formed the outermost clade of the biovar equi. A total of 1,355 core genes were identified, corresponding to 42.5% of the pangenome. This pangenome has one of the smallest core genomes described in the literature, suggesting a high genetic variability of biovar equi of C. pseudotuberculosis. The analysis of the similarity between the resistance islands identified a higher proximity between the strains that caused more severe infectious conditions (infection in the internal organs). Pathogenicity islands were largely conserved between strains. Several genes that modulate the pathogenicity of C. pseudotuberculosis were described including peptidases, recombination enzymes, micoside synthesis enzymes, bacteriocins with antimicrobial activity and several others. Finally, no genotypic differences were observed between the strains that caused the three different types of infection (external abscess formation, infection with abscess formation in the internal organs, and ulcerative lymphangitis). Instead, it was noted that there is a higher phenetic correlation between strains isolated at California compared to the other strains. Additionally, high variability of resistance islands suggests gene acquisition through several events of horizontal gene transfer.

Project description:BACKGROUND: Pan-genomic studies aim, for instance, at defining the core, dispensable and unique genes within a species. A pan-genomics study for vaccine design tries to assess the best candidates for a vaccine against a specific pathogen. In this context, rather than studying genes predicted to be exported in a single genome, with pan-genomics it is possible to study genes present in different strains within the same species, such as virulence factors. The target organism of this pan-genomic work here presented is Corynebacterium pseudotuberculosis, the etiologic agent of caseous lymphadenitis (CLA) in goat and sheep, which causes significant economic losses in those herds around the world. Currently, only a few antigens against CLA are known as being the basis of commercial and still ineffective vaccines. In this regard, the here presented work analyses, in silico, five C. pseudotuberculosis genomes and gathers data to predict common exported proteins in all five genomes. These candidates were also compared to two recent C. pseudotuberculosis in vitro exoproteome results. RESULTS: The complete genome of five C. pseudotuberculosis strains (1002, C231, I19, FRC41 and PAT10) were submitted to pan-genomics analysis, yielding 306, 59 and 12 gene sets, respectively, representing the core, dispensable and unique in silico predicted exported pan-genomes. These sets bear 150 genes classified as secreted (SEC) and 227 as potentially surface exposed (PSE). Our findings suggest that the main C. pseudotuberculosis in vitro exoproteome could be greater, appended by a fraction of the 35 proteins formerly predicted as making part of the variant in vitro exoproteome. These genomes were manually curated for correct methionine initiation and redeposited with a total of 1885 homogenized genes. CONCLUSIONS: The in silico prediction of exported proteins has allowed to define a list of putative vaccine candidate genes present in all five complete C. pseudotuberculosis genomes. Moreover, it has also been possible to define the in silico predicted dispensable and unique C. pseudotuberculosis exported proteins. These results provide in silico evidence to further guide experiments in the areas of vaccines, diagnosis and drugs. The work here presented is the first whole C. pseudotuberculosis in silico predicted pan-exoproteome completed till today.

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Cell wall glycolipids from Corynebacterium pseudotuberculosis strains with different virulences differ in terms of composition and immune recognition.

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