Use of Refrigeration as a Practical means to Preserve Viability of in Vitro-Cultured IDE8 Tick Cells
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In vitro cultivation of the IDE8 cell line, derived from embryonic Ixodes scapularis ticks, constitutes an important system for the study of tick-borne pathogens, as these cells support growth of rickettsial species which are not normally transmitted by this tick. However, since cryopreservation of IDE8 cells is not always successful, there is a need to develop alternative ways to preserve these cells. In the present study, a suspension of IDE8 cells in culture medium was kept under refrigeration at 4°C for up to 60 days. Every 15 days, the suspension was mixed and aliquots were re-cultured in 2-ml tubes, under standardized conditions. In addition, three techniques for cryopreservation, using two different cryoprotectants (DMSO and glycerol), were evaluated. Medium changes were carried out every week and subculturing every 2 weeks. The development of cultures and their respective subcultures, after returning to standard culture temperature, was evaluated by percentage viability and by cellular morphology evaluated in Giemsa-stained cytocentrifuge smears. All cultures and subcultures appeared healthy, showing growth rates comparable to cultures that had not been kept under refrigeration. The results demonstrated that storage under refrigeration at 4°C is an efficient method for preservation of IDE8 cells for up to 60 days and that refrigeration may be preferable to cryopreservation for short-term preservation of IDE8 cells.
KeywordsIDE8 cells Ixodes scapularis In vitro culture
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This work received financial support from The National Council for Scientific and Technological Development, Brazil (CNPq), through the academic scholarship awarded to Ms. Camila V. Bastos. The authors thank Dr. Bell-Sakyi (CTVM, University of Edinburgh, UK) for providing IDE8 cultures and Dr. U.G. Munderloh (University of Minnesota, USA) for permission to use the cell line.
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