The Graduate School of Veterinary Medicine, Hokkaido University
Doi
Abstract
In the present study, we employed flow cytometry to evaluate the level of parasitemia of Babesia
gibsoni infecting canine erythrocytes in vivo and in vitro by using fluorescent nucleic acid
staining. Peripheral blood samples from a B. gibsoni-infected dog and cultured B. gibsoni parasitizing
in canine erythrocytes were stained with a membrane-permeable fluorescent nucleic
acid stain, SYTO16. In this study, we utilized normal canine erythrocytes (LK erythrocytes)
and canine erythrocytes containing high concentrations of potassium, reduced glutathione,
and some free amino acids (HK erythrocytes) as host cells for culture. Parasitized cells in vivo
were discriminated completely from unparasitized cells and a correlation (r = 0.998) between
the percentage of SYTO16-positive cells and parasitemia in vivo was observed. On the other
hand, erythrocytes in vitro could not be divided clearly into parasitized and unparasitized cells.
However, when LK erythrocytes were used as host cells, the percentage of SYTO16-positive
cells was almost the same as, and was well correlated (r = 0.932) with, the level of parasitemia.
When HK erythrocytes were used as host cells, the percentage of SYTO16-positive cells was almost
half of, but was correlated (r = 0.982) with, the level of parasitemia. Therefore, we attempted
to observe the changes in the percentage of parasitized cells after treatment with antiprotozoal
drug or mitochondria inhibitors by using flow cytometry. The changes in the percentage
of SYTO16-positive cells corresponded well with the changes of the level of parasitemia
when the parasites in HK erythrocytes were cultured with each compound. The present results
suggest that flow cytometric detection using SYTO16 is a rapid and reliable method for monitoring
parasitemia both in vivo and in vitro