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Polymerase chain reaction has for the first time been shown to be applicable to indication of Leptospira interrogans in the organs of infected animals with acute or chronic leptospirosis (on the model of golden syrian hamsters). Polymerase chain reaction is superior to microscopic and bacteriological analyses in identification of leptospirae in organ suspensions. The sensitivity of the technique is 1-10 cells per sample in studies of kidney or brain suspensions or 100-1000 cells in studies of liver suspensions.
Mol Gen Mikrobiol Virusol
PMID:[A polymerase chain reaction method for studying host persistence of pathogenic leptospira]. 813 45

Two highly sensitive test systems G and B, based on the polymerase chain reaction, were developed for indication of pathogenic Leptospira interrogans, including the serovariants appearing during outbreaks in polytypical foci of leptospirosis in the tropical zone of China. These test systems can be used for rapid diagnosis of leptospirosis in humans in foci with different etiological structure.
Mol Gen Mikrobiol Virusol 1997
PMID:[Development of polymerase chain reaction-based test systems for detecting leptospira in polytypical leptospirosis foci]. 941 Dec 14

Leptospira spp. offer many advantages as model bacteria for the study of spirochaetes. However, homologous recombination between introduced DNA and the corresponding chromosomal loci has never been demonstrated. A unique feature of spirochaetes is the presence of endoflagella between the outer membrane sheath and the cell cylinder. We chose the flaB flagellin gene, constituting the flagellar core, as a target for gene inactivation in the saprophyte Leptospira biflexa. The amino acid sequence of the FlaB protein of L. biflexa was most similar to those of spirochaetes Brachyspira hyodysenteriae (agent of swine dysentery), Leptospira interrogans (agent of leptospirosis) and Treponema pallidum (agent of syphilis). A suicide vector containing the L. biflexa flaB gene disrupted by a kanamycin marker was UV irradiated or alkali denatured before electroporation. This methodology allowed the selection of many kanamycin-resistant colonies resulting from single and double cross-over events at the flaB locus. The double recombinant mutants are non-motile, as visualized in both liquid and semi-solid media. In addition, a flaB mutant selected for further analysis was shown to be deficient in endoflagella by electron microscopy. However, most of the transformants had resulted from a single homologous recombination event, giving rise to the integration of the suicide vector. We evaluated the effect of the sacB and rpsL genes in L. biflexa as potential counterselectable markers for allelic exchange, and then used the rpsL system for the positive selection of flaB double recombinants in a streptomycin-resistant strain. Like the flaB mutant studied above, the Strr double cross-over mutant was non-motile and deficient in endoflagella. Our results demonstrate that FlaB is involved in flagella assembly and motility. They also show the feasibility of performing allelic replacement in Leptospira spp. by homologous recombination.
Mol Microbiol 2001 Apr
PMID:First evidence for gene replacement in Leptospira spp. Inactivation of L. biflexa flaB results in non-motile mutants deficient in endoflagella. 1129 86

Proteins with bacterial immunoglobulin-like (Big) domains, such as the Yersinia pseudotuberculosis invasin and Escherichia coli intimin, are surface-expressed proteins that mediate host mammalian cell invasion or attachment. Here, we report the identification and characterization of a new family of Big domain proteins, referred to as Lig (leptospiral Ig-like) proteins, in pathogenic Leptospira. Screening of L. interrogans and L. kirschneri expression libraries with sera from leptospirosis patients identified 13 lambda phage clones that encode tandem repeats of the 90 amino acid Big domain. Two lig genes, designated ligA and ligB, and one pseudogene, ligC, were identified. The ligA and ligB genes encode amino-terminal lipoprotein signal peptides followed by 10 or 11 Big domain repeats and, in the case of ligB, a unique carboxy-terminal non-repeat domain. The organization of ligC is similar to that of ligB but contains mutations that disrupt the reading frame. The lig sequences are present in pathogenic but not saprophytic Leptospira species. LigA and LigB are expressed by a variety of virulent leptospiral strains. Loss of Lig protein and RNA transcript expression is correlated with the observed loss of virulence during culture attenuation of pathogenic strains. High-pressure freeze substitution followed by immunocytochemical electron microscopy confirmed that the Lig proteins were localized to the bacterial surface. Immunoblot studies with patient sera found that the Lig proteins are a major antigen recognized during the acute host infection. These observations demonstrate that the Lig proteins are a newly identified surface protein of pathogenic Leptospira, which by analogy to other bacterial immunoglobulin superfamily virulence factors, may play a role in host cell attachment and invasion during leptospiral pathogenesis.
Mol Microbiol 2003 Aug
PMID:Pathogenic Leptospira species express surface-exposed proteins belonging to the bacterial immunoglobulin superfamily. 1289 19

Leptospira borgpetersenii, one of the causative agents of leptospirosis in both animals and humans, is a bacterial pathogen with characteristic motility that is mediated by the rotation of two periplasmic flagella (PF). The flaB gene coding for a core polypeptide subunit of PF was previously characterized by sequence analysis of its open reading frame (ORF) (M. Lin, J Biochem Mol Biol Biophys 2:181-187, 1999). The present study was undertaken to isolate and clone the uncharacterized sequence upstream of the flaB gene by using a PCR-based genome walking procedure. This has resulted in a 1470-bp genomic DNA sequence in which an 846-bp ORF coding for a 281-amino acid polypeptide (31.3 kDa) is identified 455 bp upstream from the flaB start codon. The encoded protein exhibits 72% amino acid identity to the deduced FlaB protein sequence of L. borgpetersenii and a high degree of sequence homology to the FlaB proteins of other spirochaetes. This has demonstrated for the first time that a second flaB gene homolog is present in a Leptospira species. The newly identified gene is designated flaB1, and the previously cloned flaB renamed flaB2. Within the intergenic sequence between flaB1 and flaB2, a potential stem-loop structure (12-bp inverted repeats) was identified 25 bp downstream of the flaB1 stop codon; this could serve as a transcription terminator for the flaB1 mRNA. Three E. coli-like promoter regions (I, II, and III) for binding Esigma(70), a regulatory sequence uncommonly found in flagellar genes, were predicted upstream of the flaB2 ORF. Only promoter region II contains a promoter that is functional in E. coli, as revealed at phenotypic and transcriptional levels by its capability of directing the expression of the chloramphenicol acetyltransferase (CAT) gene in the promoter probe vector pKK232-8. These observations may suggest that flaB1 and flaB2 are transcribed separately and do not form a transcriptional operon controlled by a single promoter.
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PMID:Identification of a second flagellin gene and functional characterization of a sigma70-like promoter upstream of a Leptospira borgpetersenii flaB gene. 1505 84

Leptospirosis is globally important infectious disease affecting almost all mammals. Pathogenic Leptospira encodes immunoglobulin-like protein (Lig) that is found to express only during infection. We report the development of conventional and real time PCR assays targeting lig genes of leptospires for the early diagnosis of leptospirosis. Sensitivity of the newly designed Lig1/Lig2 primers for conventional PCR was compared with previously published primers LP1/LP2 and G1/G2. G1/G2 primers amplified the target DNA from all the serovars including non-pathogenic Leptospira biflexa whereas LP1/LP2 and Lig1/Lig2 primers amplified only pathogenic leptospires. Diagnostic PCR assay was also developed for the detection of pathogenic Leptospira interrogans in urine samples. We obtained the highest sensitivity in PCR using our Lig1/Lig2 primers with a detection of 6 leptospires. A rapid and sensitive lig-based real time PCR assay was also developed with a detection range of 10-10(7) gene copies. To evaluate the early diagnosis for leptospirosis, we compared the culture with conventional and real time PCR for the detection of spirochetes in experimentally infected hamsters during a time-course study. Culture of infected hamster tissues detected the presence of leptospires from Day 2 of infection but not on the day of infection or Day 1, whereas conventional PCR and real time PCR detected the leptospires from the day of infection. Hence, conventional and real time PCR with lig primers would be a sensitive and rapid tool for early diagnosis of leptospirosis.
Mol Cell Probes 2005 Apr
PMID:Evaluation of lig-based conventional and real time PCR for the detection of pathogenic leptospires. 1568 Feb 12

Leptospirosis is a bacterial zoonotic disease that remains a public health problem worldwide. Unfortunately, the current gold standard test used for the serological diagnosis of leptospirosis has some drawbacks and there is no vaccine available for successful prevention of leptospirosis in humans. Therefore, recent research on leptospirosis has focused mainly on identifying leptospiral immunogens to be used for diagnostics and vaccine development. This review provides a brief summary of recent proteomic studies applied to leptospirosis. These studies were conducted with two major aims: to characterize outer membrane proteins using a classical proteomics approach and to identify potential leptospiral immunogens using an immunoproteomics approach. The results obtained from these studies may lead to the development of earlier and more accurate diagnostic test(s) and vaccine discovery.
Expert Rev Mol Diagn 2008 Jan
PMID:Proteomics in leptospirosis research: towards molecular diagnostics and vaccine development. 1808 30

In this study, the full lipL21 gene fragment encoding outer membrane protein LipL21 was cloned from L. interrogans serovar Lai and inserted into eukaryotic expression vector pcDNA3.1(+). The guinea pigs were immunized with pcDNA3.1(+)-lipL21, pcDNA3.1(+) or PBS. Six weeks after the second immunization, the splenocytes were isolated to detect their proliferative ability by lymphocyte transformation experiments. In addition, microscopic agglutination test was used for quantitative detection of specific antibodies. The rest guinea pigs were challenged intraperitoneally with L. interogans sorevar Lai. Then, protective effect was evaluated on the basis of survival and histopathological lesions in the kidneys, lungs, and liver. The lipL21 gene was successfully expressed in COS-7 cells through recombinant pcDNA3.1(+)-lipL21. The titer of specific antibodies substantially increased, and the stimulation index of splenocytes increased significantly. Hence, the pcDNA3.1(+)-lipL21 could protect the immunized guinea pigs from homotypic Leptospira infection. Furthermore, no obvious pathologic changes were observed in the pcDNA3.1(+)-lipL21 immunized guinea pigs. The results showed that the protective effect with pathogenic strains of Leptospira was shared by LipL21 mediated through a plasmid vector. Consequently, these results indicated that the lipL21 DNA vaccine was a promising candidate for the prevention of leptospirosis.
Cell Mol Immunol 2008 Oct
PMID:Protection of guinea pigs against Leptospira interrogans serovar Lai by LipL21 DNA vaccine. 1895 63

Spirochetes of the genus Leptospira cause leptospirosis in humans and animals worldwide. Proteins exposed on the bacterial cell surface are implicated in the pathogenesis of leptospirosis. However, the biological role of the majority of these proteins is unknown; this is principally due to the lack of genetic systems for investigating Leptospira and the absence of any structural information on leptospiral antigens. To address this, we have determined the 2.0-A-resolution structure of the lipoprotein LipL32, the most abundant outer-membrane and surface protein present exclusively in pathogenic Leptospira species. The extracellular domain of LipL32 revealed a compact, globular, "jelly-roll" fold from which projected an unusual extended beta-hairpin that served as a principal mediator of the observed crystallographic dimer. Two acid-rich patches were also identified as potential binding sites for positively charged ligands, such as laminin, to which LipL32 has a propensity to bind. Although LipL32 shared no significant sequence identity to any known protein, it possessed structural homology to the adhesins that bind components of the extracellular matrix, suggesting that LipL32 functions in an analogous manner. Moreover, the structure provides a framework for understanding the immunological role of this major surface lipoprotein.
J Mol Biol 2009 Apr 17
PMID:Crystal structure of LipL32, the most abundant surface protein of pathogenic Leptospira spp. 1923 79

Leptospirosis, a spirochaetal zoonotic disease caused by Leptospira, has been recognized as an important emerging infectious disease. LipL32 is the major exposed outer membrane protein found exclusively in pathogenic leptospires, where it accounts for up to 75% of the total outer membrane proteins. It is highly immunogenic, and recent studies have implicated LipL32 as an extracellular matrix binding protein, interacting with collagens, fibronectin, and laminin. In order to better understand the biological role and the structural requirements for the function of this important lipoprotein, we have determined the 2.25-A-resolution structure of recombinant LipL32 protein corresponding to residues 21-272 of the wild-type protein (LipL32(21-272)). The LipL32(21-272) monomer is made of a jelly-roll fold core from which several peripheral secondary structures protrude. LipL32(21-272) is structurally similar to several other jelly-roll proteins, some of which bind calcium ions and extracellular matrix proteins. Indeed, spectroscopic data (circular dichroism, intrinsic tryptophan fluorescence, and extrinsic 1-amino-2-naphthol-4-sulfonic acid fluorescence) confirmed the calcium-binding properties of LipL32(21-272). Ca(2+) binding resulted in a significant increase in the thermal stability of the protein, and binding was specific for Ca(2+) as no structural or stability perturbations were observed for Mg(2+), Zn(2+), or Cu(2+). Careful examination of the crystallographic structure suggests the locations of putative regions that could mediate Ca(2+) binding as well as binding to other interacting host proteins, such as collagens, fibronectin, and laminin.
J Mol Biol 2009 Jul 24
PMID:Structure and calcium-binding activity of LipL32, the major surface antigen of pathogenic Leptospira sp. 1947 85


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