As shown by RFLP analysis, there is a high variability in the β-tubulin gene region of Leishmania sp. Such variability has been used in the identification of these parasites, establishing differences between subgenera of New World Leishmania. We have found a region of 500 bp (β500) upstream of the coding region of the β-tubulin gene that is present in all strains tested belonging to the L. (Viannia) subgenus. This region apparently is a repetitive sequence and we have shown that it is specific to the Leishmania (Viannia) subgenus. This sequence has no homology with the genomic DNA isolated from either the species belonging to the L. (Leishmania) subgenus or other Kinetoplastida, such as Trypanosoma cruzi, T. brucei, Leptomonas samueli, or Crithidia fasciculata. The β500 sequence showed sufficient variation to be used as a molecular marker in the identification of parasites. We established inter- and intrasubgenus differentiation and were able to discriminate at the species level in the Vianna subgenus. A PCR assay confirmed the specificity of the β500 sequence.

In the present study the gp63 gene locus was used as a target for genetic characterization of Leishmania parasites by 2 methods: (i) RFLP analysis with several restriction enzymes (gp63–RFLP), and (ii) intra-genic PCR amplification coupled with restriction analysis (PCR–RFLP). Both methods were applied to a large number of natural isolates belonging to 4 species of the subgenus Viannia, namely L. (V.) braziliensis, L. (V.) peruviana, L. (V.) guyanensis and L. (V.) lainsoni: reference stocks of subgenus Leishmania were included as outgroups. Multilocus isoenzyme typing (MLEE) was used as a reference. On the one hand gp63–RFLP evidenced an extensive polymorphism and revealed specific markers for subgenus, species and geographical populations: congruence with MLEE was demonstrated statistically. The particular interest of gp63–RFLP was illustrated by infra-specific polymorphism, because of the possible relationship with phenotype diversity. On the other hand intra-genic amplification was less resolutive than gp63–RFLP, but also allowed discrimination of the 2 subgenera (PCR alone) and all the species tested in the subgenus Viannia (PCR–RFLP). PCR–RFLP presents an important operational advantage as it allows genetic characterization of minute amounts of parasites, using Leishmania specific primers. The polymorphism revealed by gp63–RFLP and PCR–RFLP illustrates the very high genomic and genetic plasticity of gp63 genes.