Genetic diversity of the Leptospiral immunoglobulin-like (Lig) genes in pathogenic Leptospira spp.

Recent serologic, immunoprotection, and pathogenesis studies identified the Lig proteins as key virulence determinants in interactions of leptospiral pathogens with the mammalian host. We examined the sequence variation and recombination patterns of ligA, ligB, and ligC among 10 pathogenic strains from five Leptospira species. All strains were found to have intact ligB genes and genetic drift accounting for most of the ligB genetic diversity observed. The ligA gene was found exclusively in L. interrogans and L. kirschneri strains, and was created from ligB by a two-step partial gene duplication process. The aminoterminal domain of LigB and the LigA paralog were essentially identical (98.5 ± 0.8% mean identity) in strains with both genes. Like ligB, ligC gene variation also followed phylogenetic patterns, suggesting an early gene duplication event. However, ligC is a pseudogene in several strains, suggesting that LigC is not essential for virulence. Two ligB genes and one ligC gene had mosaic compositions and evidence for recombination events between related Leptospira species was also found for some ligA genes. In conclusion, the results presented here indicate that Lig diversity has important ramifications for the selection of Lig polypeptides for use in diagnosis and as vaccine candidates. This sequence information will aid the identification of highly conserved regions within the Lig proteins and improve upon the performance characteristics of the Lig proteins in diagnostic assays and in subunit vaccine formulations with the potential to confer heterologous protection.     

Effets de différents antioxydants sur la lipoperoxydation in vitro initiée par le radical °OH

Rationale and ObjectiveThe study of the oxidative stress remains an analytical challenge and a model of lipid peroxidation is described for this purpose: it is based on a hydrogen peroxide- porphyrin mix as an °OH generator and artificial «plasma» as acceptor.Materials and MethodsLipid peroxidation is assessed by the measurement of true malondialdehyde with a specific HPLC-UV method. This model is used for checking the role of four antioxidants, the first one being a hydrophilic compound (Trolox) and the others natural lipophilic molecules (α tocophérol, β carotene and lycopene).ResultsA linear relationship between concentrations and inhibition of MDA production is shown for the four compounds.ConclusionThis model, easy to handle, could therefore be useful for testing in vitro both hydrophilic and lipophilic antioxidants.     

Chromatin interactions in differentiating keratinocytes reveal novel atopic dermatitis– and psoriasis-associated genes

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