Genetic divergence between two sympatric species of the Lutzomyia longipalpis complex in the paralytic gene, a locus associated with insecticide resistance and lovesong production

The sandfly Lutzomyia longipalpis s.l. is the main vector of American Visceral Leishmaniasis. L. longipalpis s.l. is a species complex but until recently the existence of cryptic sibling species among Brazilian populations was a controversial issue. A fragment of paralytic (para), a voltage dependent sodium channel gene associated with insecticide resistance and courtship song production in Drosophila, was isolated and used as a molecular marker to study the divergence between two sympatric siblings of the L. longipalpis complex from Sobral, Brazil. The results revealed para as the first single locus DNA marker presenting fixed differences between the two species in this locality. In addition, two low frequency amino-acid changes in an otherwise very conserved region of the channel were observed, raising the possibility that it might be associated with incipient resistance in this vector. To the best of our knowledge, the present study represents the first population genetics analysis of insecticide resistance genes in this important leishmaniasis vector.

The IFN-³+874T/A gene polymorphism is associated with retinochoroiditis toxoplasmosis susceptibility

Toxoplasmosis is a worldwide zoonosis that generally produces an asymptomatic infection. In some cases, however, toxoplasmosis infection can lead to ocular damage. The immune system has a crucial role in both the course of the infection and in the evolution of toxoplasmosis disease. In particular, IFN-³ plays an important role in resistance to toxoplasmosis. Polymorphisms in genes encoding cytokines have been shown to have an association with susceptibility to parasitic diseases. The aim of this work was to analyse the occurrence of polymorphisms in the gene encoding IFN-³ (+874T/A) among Toxoplasma gondii seropositive individuals, including those with ocular lesions caused by the parasite, from a rural population of Santa Rita de Cássia, Barra Mansa, state of Rio de Janeiro, Brazil. Further, we verified which of these polymorphisms could be related to susceptibility to the development of ocular toxoplasmosis. This study included 34 individuals with ocular toxoplasmosis (ocular group) and 134 without ocular lesions (control group). The differences between A and T allele distributions were not statistically significant between the two groups. However, we observed that a higher frequency of individuals from the ocular group possessed the A/A genotype, when compared with the control group, suggesting that homozygocity for the A allele could enhance susceptibility to ocular toxoplasmosis in T. gondii infection.

Cl gene cluster encoding several small nucleolar RNAs: a comparison amongst trypanosomatids

Small nucleolar RNAs (snoRNAs) are small non-coding RNAs that modify RNA molecules such as rRNA and snRNA by guiding 2'-O-ribose methylation (C/D box snoRNA family) and pseudouridylation reactions (H/ACA snoRNA family). H/ACA snoRNAs are also involved in trans-splicing in trypanosomatids. The aims of this work were to characterise the Cl gene cluster that encodes several snoRNAs in Trypanosoma rangeli and compare it with clusters from Trypanosoma cruzi, Trypanosoma brucei, Leishmania major, Leishmania infantum, Leishmania braziliensis and Leptomonas collosoma. The T. rangeli Cl gene cluster is an 801 base pair (bp) repeat sequence that encodes three C/D (Cl1, Cl2 and Cl4) and three H/ACA (Cl3, Cl5 and Cl6) snoRNAs. In contrast to T. brucei, the Cl3 and Cl5 homologues have not been annotated in the Leishmania or T. cruzi genome projects (http//:www.genedb.org). Of note, snoRNA transcribed regions have a high degree of sequence identity among all species and share gene synteny. Collectively, these findings suggest that the Cl cluster could constitute an interesting target for therapeutic (gene silencing) or diagnostic intervention strategies (PCR-derived tools).

RFLP analysis of a PCR-amplified fragment of the 16S rRNA gene as a tool to identify Enterococcus strains

Restriction fragment length polymorphism (RFLP) analysis of a PCR-amplified fragment of the 16S rRNA gene was performed on reference strains belonging to 21 different enterococcal species and on 75 Enterococcus isolates recovered from poultry meat, pasteurised milk and fresh cheese. PCR amplification generated a 275 bp fragment, which was digested with three restriction endonucleases (DdeI, HaeIII, HinfI). The strains were divided into five groups (groups A-E) on the basis of their restriction patterns. Five biochemical tests (arabinose, arginine, manitol, methyl-β-D-glucopyranoside and raffinose) were then performed in addition to RFLP analysis to narrow the identification of enterococcal strains to the species level. PCR-RFLP, in conjunction with the selected biochemical tests, allowed the precise identification of the 21 species of Enterococcus included in the present study. This proposed method is relatively simple and rapid and can be useful as an adjunct tool for accurate identification of Enterococcus.