Polymorphism of the gene encoding a major Polar Tube Protein PTP1 in two microsporidia of the genus Encephalitozoon

Isolates of 2 microsporidian species from the genus Encephalitozoon (E. cun iculi and E. hellem) were compared by analysis of DNA amplified from a gene region encoding the repeat domain of a polar tube protein (PTP1). Sequence data obtained for 11 E. cuniculi isolates from 5 different mammalian hosts well support the existence of 3 previously designated strains. Strain type III was characterized by a lack of a 78 bp repeat, producing an amplicon o f reduced size. Strain type II differed from strain type I by 3 nucleotide substitutions so that AvaII digestion of the corresponding PCR products pro vided distinct restriction patterns. Surprisingly, the comparison of 2 huma n isolates of E. hellem belonging to the same rDNA ITS genotype shows a hig h level of heterogeneity through numerous point mutations and variation in PTP1 repeat number. Further characterization of additional E. hellem isolat es based on PTP1 sequence polymorphisms should be of interest for tracing s ources of infection.