Karyotype changes in cultivated tick cell lines

Background. Tick cell lines are an easy-to-handle system for the study of viral and bacterial infections and different aspects of tick physiology. However, long-term cultivation of tick cells can influence genome stability. The aim of our work was to analyze and compare the karyotypes of Ixodes scapularis, I. ricinus, and Ornithodoros moubata tick cell lines after long-term been in culture.

Methods. Mitotic spreads were prepared to count the number of chromosomes in ISE6, ISE18, IRE11, IRE/CTVM19, IRE/CTVM20, and OME/CTVM22 cell lines. The genome size of tick cell cultures was estimated by flow cytometry using propidium iodide staining.

Results. The modal chromosome numbers around 22 and around 48 were typical for both I. ricinus and I. scapularis cell lines and differed from the diploid chromosome number in Ixodesticks – 28. In the OME/CTVM22cell line, the modal chromosome number was 33, instead of 20 in Ornithodoros ticks. All tick cell lines had a larger genome size in compare to genomes of parental ticks.

Conclusions.Tick cell lines can be used for research purposes, however, differences in the internal processes between different cell populations should be taken into account.

Acknowledgments: We thank Lesley Bell-Sakyi and the Tick Cell Biobank for provision of the tick cell lines.