GENOTYPIC POLYMORPHISMS IN EXPERIMENTAL METASTATIC DERMAL LEISHMANIASIS

Molecular karyotype and kDNA restriction analyses were utilized to exa mine the genetic heterogeneity and plasticity of the Leishmania (Viann ia) guyanensis strain WHI/BR/78/M5313, composed of metastatic and non- metastatic populations. Cloning revealed that the strain was constitut ed by multiple closely related populations that were distinguishable b y restriction fragment polymorphisms in kDNA. Size polymorphisms in mo lecular karyotype were not detected. Passage of clones in hamsters and recovery of parasites from cutaneous metastatic lesions yielded evide nce of further genetic heterogeneity among some of the progeny populat ions. Overall, six kDNA minicircle restriction patterns or schizodemes were observed among clones, subclones and progeny. Although the possi bility that population heterogeneity was not resolved by cloning canno t be ruled out, subcloning and kDNA restriction analysis to determine whether the putative clones consisted of homogeneous populations showe d the schizodeme of subclones of 3 out of 4 clones to be identical to the clone of origin, while a subclone of the fourth had a co-efficient of similarity of 0.95. Metastasis did not segregate with a particular schizodeme: all six restriction profiles were represented among popul ations isolated from metastatic lesions and some clones with the same restriction profile did not produce metastatic lesions. The strain fro m which the clones, subclones and progeny were derived had a kDNA rest riction pattern identical to the most prevalent schizodeme (38%) among these subpopulations. This finding together with the reappearance of the repertoire of schizodemes found among clones in the populations re covered from metastatic lesions in hamsters inoculated with a single c lone, suggest that sequence polymorphisms in kDNA can emerge during in fection.