Leishmania mexicana mexicana: genetic heterogeneity of mexican isolates revealed by restriction length polymorphism analysis of kinetoplast DNA

Leishmania mexicana mexicana isolates from 23 patients with localized, diffuse, and an atypical "pseudodiffuse" form of cutaneous leishmaniasis were obtained in various endemic regions of Mexico. Restriction fragment length polymorphism analysis of kinetoplast DNA was done with nine different endonucleases in addition to an in vitro growth pattern analysis. We found that the 23 L. mexicana mexicana isolates could be consistently classified into six groups, according to the endonuclease digestion patterns obtained with HaeIII, HpaII, and MseI. Whereas localized cutaneous leishmaniasis isolates could have any of five patterns, diffuse cutaneous leishmaniasis showed only two patterns and pseudodiffuse cutaneous leishmaniasis consistently showed only one pattern. Thus, a clear correlation among digestion pattern, clinical disease, and geographical localization was obtained for the pseudodiffuse cutaneous leishmaniasis group. Additionally, the L. mexicana mexicana isolates could be differentiated into fast- and slow-growing groups. Diffuse cutaneous leishmaniasis isolates were found to be fast growing, whereas localized cutaneous leishmaniasis isolates fell into both categories. In contrast, all pseudo diffuse cutaneous leishmaniasis isolates were slow growing. Here we report the first study in which distinct and persistent genotypic characteristics of kinetoplast DNA heterogeneity within the L. mexicana mexicana species could be directly correlated with clinical disease and its growth behavior, suggesting that a distinctive restriction pattern could have important biological implications. Additionally, this study sheds new light on the biological significance of parasite kinetoplast DNA, since the heterogeneity seems not to be random but to form a distinct pattern.