[A variant of DDRT-PCR using anchored mini-exon primers for identification of differentially expressed sequences in Leishmania infantum].

Abstract

Leishmania infantum (L.i) is responsible for visceral (VL) or cutaneous (CL) leishmaniasis. Previous studies done in Honduras by differential display reverse transcriptase-polymerase chain reaction (DDRT-PCR) failed to demonstrate differences in expression profiles among L. infantum VL and CL parasites. For purpose of comparing expression among L. infantum isolates in Tunisia, a variant of this technique adapted from a commercial kit was developed involving pairs of random and anchored mini-exon primers for isolation and identification of differentially displayed cDNAs. To assess the efficiency of this variant, 34 pairs were applied to 2 consecutive dilutions of cDNAs from promastigotes at end of in vitro exponential growth of 2 visceral (LV50) and cutaneous (DREP14) isolates from Tunisia, thus increasing chance for observing differences among the cDNAs. Profiles were compared and analyzed as regards number and phenotype of bands displayed in 4 types of highly similar amplification profiles among the 2 cDNAs; 26 primer pair combinations generated in total 6.8% differentially displayed bands that had variable intensities or were present/absent, in comparable proportions in the 2 isolates. Analysis further demonstrated differences in amplification efficiency of some primers, emphasizing on qualitative and quantitative impact of relative proximity of the priming sites. Nine present/absent bands were cloned, sequenced and analyzed in silico. Mismatches at priming sites seem to underlie amplification of such bands. Only five products could be referred to annotated gene. Among the genes identified, we list histone H4, largely known to be differentially expressed among L.i stages, and "NTF2-like" for which overexpression in one cDNA was here confirmed. To conclude, the variant developed could be used further in Leishmania expression analysis with appropriate cautions about false positives.