18S rRNA sequences of Leishmania enriettii promastigote and amastigote

Fluorescent Leishmania species: development of stable GFP expression and its application for in vitro and in vivo studies

Reporter genes have proved to be an excellent tool for studying disease progression. Recently, the green fluorescent protein (GFP) ability to quantitatively monitor gene expression has been demonstrated in different organisms. This report describes the use of Leishmania tarentolae (L. tarentolae) expression system (LEXSY) for high and stable levels of GFP production in different Leishmania species including L. tarentolae, L. major and L. infantum. The DNA expression cassette (pLEXSY-EGFP) was integrated into the chromosomal ssu locus of Leishmania strains through homologous recombination. Fluorescent microscopic image showed that GFP transgenes can be abundantly and stably expressed in promastigote and amastigote stages of parasites. Furthermore, flow cytometry analysis indicated a clear quantitative distinction between wild type and transgenic Leishmania strains at both promastigote and amastigote forms. Our data showed that the footpad lesions with GFP-transfected L. major are progressive over time by using fluorescence small-animal imaging system. Consequently, the utilization of stable GFP-transfected Leishmania species will be appropriate for in vitro and in vivo screening of anti-leishmanial drugs and vaccine development as well as understanding the biology of the host-parasite interactions at the cellular level.

Description of Perkinsus andrewsi n. sp. isolated from the Baltic clam (Macoma balthica) by characterization of the ribosomal RNA locus, and development of a species-specific PCR-based diagnostic assay

A Perkinsus species was isolated from the baltic clam Macoma balthica and an in vitro culture established under conditions described for P. marinus. As reported previously, morphological features remarkable enough to clearly indicate that this isolate is a distinct Perkinsus species were lacking. In this study, regions of the rRNA locus (NTS, 18S, ITS1, 5.8S, and ITS2) of this isolate were cloned, sequenced, and compared by alignment with those available for other Perkinsus species and isolates. Sequence data from the rRNA locus and species-specific PCR assays indicated not only that Perkinsus sp. from M. balthica was not P. marinus, but it was different from P. atlanticus and P. olseni. The degree of difference was comparable to or greater than differences between accepted Perkinsus species. In particular, NTS sequence and length were dramatically different from that of P. marinus and P. atlanticus. Therefore, we formally propose to designate the Perkinsus sp. from M. balthica as a separate species, P. andrewsi n. sp. Primers based on P. andrewsi NTS sequence were used to develop a PCR-based diagnostic assay that was validated for species-specificity and sensitivity. PCR-based assays specific for either P. andrewsi or P. marinus were used to test for their presence in bivalve species sympatric to M. balthica. Although isolated from M. balthica, P. andrewsi was also detected in the oyster Crassostrea virginica and clams Macoma mitchelli and Mercenaria mercenaria, and could coexist with P. marinus in all four bivalve species tested.

Multi-site DNA polymorphism analyses of Leishmania isolates define their genotypes predicting clinical epidemiology of leishmaniasis in a specific region

Leishmania isolates from 57 cases of human cutaneous (CL), human visceral (VL), and canine visceral (CVL) leishmaniasis in Turkey were grouped by multi-site DNA polymorphism analyses into five genotypes. The initial grouping was based on DNA heterogeneity of the faster-evolving mitochondrion (kinetoplast) minicircles and the intergenic regions of two nuclear repetitive genes. Taxonomic affiliation and phylogenetic relationships of the five genotypes were inferred by comparing them with reference species for sequence heterogeneity in a approximately 1.4 kb conserved single-copy gene, encoding N-acetylglucosamine-1-phosphate transferase (NAGT). Alignment of the available sequences revealed no gap, but up to 7% scattered base substitutions, suggesting that this functionally important gene is a suitable marker. Three genotypes are completely identical to the NAGTs of the reference species, identifying them as L. infantum, L. tropica. and L. major, respectively. The remaining two are recognized as L. major NAGT variants with one and four base substitutions, respectively. As expected, Maximum Likelihood analysis of the NAGT sequences separates them into three clades, corresponding to the three species. The majority of the isolates obtained are L. infantum and L. tropica, which have been known to cause infantile VL and anthroponotic CL in western and southeastern Turkey, respectively. Unexpected is the finding of Leishmania major variants and their dispersal, possibly as previously unrecognized clinico-epidemiologic entities of CL and VL.