Organization of H locus conserved repeats in Leishmania (Viannia) braziliensis correlates with lack of gene amplification and drug resistance

Abstract

Resistance to antimonials is a major problem when treating visceral leishmaniasis in India and has already been described for New World parasites. Clinical response to meglumine antimoniate in patients infected with parasites of the Viannia sub-genus can be widely variable, suggesting the presence of mechanisms of drug resistance. In this work, we have compared L. major and L. braziliensis mutants selected in different drugs. The cross-resistance profiles of some cell lines resembled those of mutants bearing H locus amplicons. However, amplified episomal molecules were exclusively detected in L. major mutants. The analysis of the L. braziliensis H region revealed a strong conservation of gene synteny. The typical intergenic repeats that are believed to mediate the amplification of the H locus in species of the Leishmania sub-genus are partially conserved in the Viannia species. The conservation of these non-coding elements in equivalent positions in both species is indicative of their relevance within this locus. The absence of amplicons in L. braziliensis suggests that this species may not favour extra-chromosomal gene amplification as a source of phenotypic heterogeneity and fitness maintenance in changing environments.

Comparison of gene expression patterns amongLeishmania braziliensisclinical isolates showing a differentin vitrosusceptibility to pentavalent antimony

“…The comparative genomic analysis of L. major, L. infantum and L. braziliensis (Peacock Smith et al 2007) showed the presence of a putative RNAi machinery in the latter species, which might have an effect on gene expression regulation. In line with this, the comparison of the organization of the H locus conserved repeats between L. braziliensis and L. major resistant mutants did not show amplified episomal molecules in L. braziliensis (Dias et al 2007). Furthermore, we cannot exclude that point mutations in important functional sites could be also related to resistance in L. braziliensis.…”

Molecular characterization of the MRPA transporter and antimony uptake in four New World Leishmania spp. susceptible and resistant to antimony

“…Sampaio and Traub-Cseko (2003) reported the presence of amplification of the biopterin transporter in a linear and stable chromosome of 245 kb in L. braziliensis (M2903 strain). However, the results obtained by Dias et al (2007) suggest that in L. braziliensis the generation of amplicons is not a common phenomenon when this specie is subjected to drug pressure. Nevertheless, our results in antimony-resistant L. braziliensis line indicate that extrachromosomal amplification of the MRPA gene may occur, corroborating the data of Sampaio and Traub-Cseko (2003).…”

Antimony Resistance inLeishmania, Focusing on Experimental Research

“…This locus is flanked at each side by repeated sequences of 1389 bp that present a sequence homology of 100% in a L. infantum strain selected for SbIII resistance [60]. These repeats were also found on the same chromosome of L. major and L. braziliensis [96]. However, in L. mexicana selected for AsIII resistance, it was located in a linear amplicon [95].…”

“…MRPA gene is frequently amplified/overexpressed in strains resistant to heavy metals [60, 83]. The level of resistance is associated with this amplification as demonstrated by a comparative study between in vitro selected L. major and L. braziliensis strains to antimonials [96]. In fact, resistance was associated to H-circle amplification in L. major but not in L. braziliensis and the latter remained significantly more sensitive to antimony.…”