The OmpA-Like Protein Loa22 Is Essential for Leptospiral Virulence

Children's Hospital Boston, United States of America
PLoS Pathogens (Impact Factor: 7.56). 08/2007; 3(7):e97. DOI: 10.1371/journal.ppat.0030097
Source: PubMed


Author Summary

The spirochetes, which include medically important pathogens such as the causative agents of Lyme disease, syphilis, and leptospirosis, constitute an evolutionarily unique group of bacteria. Leptospirosis is a zoonotic disease that causes a high rate of mortality and morbidity in humans and animals throughout the world each year. The year 2007 marks the centenary of the discovery of the causative agent of leptospirosis, Leptospira interrogans. Until now, the genetic obstacles posed by leptospires (principally, the difficulties in generating targeted mutants) have hampered the identification of virulence genes. In this study, we describe an avirulent mutant in a pathogenic Leptospira that was obtained via disruption of loa22, a gene that encodes an outer membrane protein containing an OmpA domain. This mutation resulted in an avirulent mutant in the guinea pig model, and reintroduction of loa22 into the mutant restored Leptospira's ability to kill guinea pigs. Our results therefore indicate that loa22 is a virulence determinant that is, to our knowledge, the first identified for this pathogen.


Available from: Albert I Ko, Sep 24, 2014
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    • "In addition, vesicles were not detected from the cells of the Soft morphotype that possess gliding motility, according to the spreading of colonies. Indeed, OmpA has been demonstrated to act as an adhesin and invasin, for example in Pasteurella multocida[35], several E. coli strains [36], Neisseria gonorrhea[32], Leptospira interrogans (causative agent of leptospirosis) [37], Riemerella anatipestifer (pathogen of domestic ducks) [38] and many other pathogens [39]. The protein has a strong immunogenic capacity [36,40]. "
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    ABSTRACT: Background Flavobacterium columnare (Bacteroidetes) is the causative agent of columnaris disease in farmed freshwater fish around the world. The bacterium forms three colony morphotypes (Rhizoid, Rough and Soft), but the differences of the morphotypes are poorly known. We studied the virulence of the morphotypes produced by F. columnare strain B067 in rainbow trout (Onconrhynchus mykiss) and used high-resolution scanning electron microscopy to identify the fine structures of the cells grown in liquid and on agar. We also analysed the proteins secreted extracellularly and in membrane vesicles to identify possible virulence factors. Results Only the Rhizoid morphotype was virulent in rainbow trout. Under electron microscopy, the cells of Rhizoid and Soft morphotypes were observed to display an organised structure within the colony, whereas in the Rough type this internal organisation was absent. Planktonic cells of the Rhizoid and Rough morphotypes produced large membrane vesicles that were not seen on the cells of the Soft morphotype. The vesicles were purified and analysed. Two proteins with predicted functions were identified, OmpA and SprF. Furthermore, the Rhizoid morphotype secreted a notable amount of a small, unidentified 13 kDa protein absent in the Rough and Soft morphotypes, indicating an association with bacterial virulence. Conclusions Our results suggest three factors that are associated with the virulence of F. columnare: the coordinated organisation of cells, a secreted protein and outer membrane vesicles. The internal organisation of the cells within a colony may be associated with bacterial gliding motility, which has been suggested to be connected with virulence in F. columnare. The function of the secreted 13 kDa protein by the cells of the virulent morphotype cells remains unknown. The membrane vesicles might be connected with the adhesion of cells to the surfaces and could also carry potential virulence factors. Indeed, OmpA is a virulence factor in several bacterial pathogens, often linked with adhesion and invasion, and SprF is a protein connected with gliding motility and the protein secretion of flavobacteria.
    BMC Microbiology 06/2014; 14(1):170. DOI:10.1186/1471-2180-14-170 · 2.73 Impact Factor
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    • "Several virulence factors have been shown potential for the development of diagnostic assays for leptospirosis, including proteins OmpL1 (Haake et al. 1993), Lig (Leptospiral immunoglobulin-like) (Matsunaga et al. 2003), LenA/LenD (Stevenson et al. 2007), Loa22 (Ristow et al. 2007) and subsurface lipoprotein 32 (LipL32) (Haake et al. 2000; Pinne and Haake 2013). Among these proteins, LipL32 is the most abundant antigen found in the leptospiral total protein profile and highly conserved among the pathogenic Leptospira species but has no orthologs in the saprophyte Leptospira (Haake et al. 2000). "
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    ABSTRACT: The production of recombinant LipL32 protein using Escherichia coli has been used extensively for the development of vaccines and diagnostic tests for leptospirosis. However, E. coli has demonstrated limitations, including low yield and lack of post-translational modifications. In this study, rLipL32 was produced in eukaryotic expression system (Pichia pastoris) and evaluated the antigen by enzyme-linked immunosorbent assay (ELISA). The yield obtained from the culture supernatant reached 270 mg/L and ELISA showed an accuracy of 95.34%. In summary, the production of rLipL32 using P. pastoris did not impair the antigenic characteristics of this antigen and ensured its use for detecting the leptospiral antibodies in swine sera.
    Brazilian Archives of Biology and Technology 12/2013; 57(AHEAD). DOI:10.1590/S1516-89132014005000001 · 0.55 Impact Factor
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    • "The random transposon mutagenesis in Loa22 gene by Himar1 insertion led to a complete loss of virulence in the guinea pig disease model. This proved to be a real breakthrough of identifying Loa22 as a virulence determinant which satisfied Koch's molecular postulates (Ristow et al., 2007). However, later studies on comparative genome sequence analysis of the saprophyte Leptospira biflexa revealed that pathogenic Loa22 gene has an ortholog with 73% similarity in L. biflexa and its presence in the saprophytic species suggests that it is involved in survival rather than being a direct virulence factor. "
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    ABSTRACT: Abstract Pathogenic Leptospira species are important human and animal pathogen that causes leptospirosis, with more than half a million cases reported annually but little is known regarding the true incidence of leptospirosis due to the limitations in diagnosis. Proteins embedded in the outer membrane are found to be prime drug targets due to its key role as receptors for cellular communication and gatekeepers for iron and substrate transport across cell membranes. The major key issues to be addressed to overcome the disease burden of leptospirosis are: need to identify the genes that turn on in vivo; development of rapid diagnostic methods to facilitate the early diagnosis and to develop a universal vaccine. Recent whole genome sequencing of Leptospira species and development of in silico analysis tools have led to the identification of a large number of leptospiral virulence genes, metabolic pathways and surface protein secretion systems that represent potential new targets for the development of anti-leptospiral drug, vaccine and diagnostic strategies. This review surveys the different types of outer membrane proteins (OMPs) of Leptospira and combines all the novel features of OMPs reported till date and put forth some views for future research.
    Critical Reviews in Microbiology 05/2013; 41(1). DOI:10.3109/1040841X.2013.787387 · 6.02 Impact Factor
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