Isoenzyme Analysis of Babesia microti Infections in Humans

ABSTRACT. We used high-resolution polyacrylamide gradient gel electrophoresis (PGGE) to separate four babesial enzymes to aid in the identification of two Babesia microti isolates established in hamsters. The isolates were compared to two different hamster passages of the “Gray” strain. All isoenzyme patterns from the two isolates and the “Gray” strain were similar except glucose phosphate isomerase (GPI) from one of the “Gray” strain passages. It showed a polymorphic GPI pattern as opposed to a monomorphic GPI pattern seen in the other “Gray” strain passage and the two isolates. The observed differences suggested (i) that some populations of B. microti are capable of having polymorphic GPI, (ii) that the “Gray” strain originally contained (and may still contain) a heterogenous population of B. microti, and (iii) that the population possessing polymorphic GPI was selected over that with monomorphic GPI. This information was obtained by a PGGE method that eliminated hemoglobin from gels and allowed, for the first time, detection of babesial leucine amino peptidase (LAP) and isocitrate dehydrogenase (IDH). In addition, this method provided molecular weight estimations on babesial GPI, LAP, IDH, and glutamate dehydrogenase (GDH), and it proved useful in the identification and characterization of the B. microti isolates.