Increasing the Yield of Eimeria tenella Oocysts in Cell Culture

Abstract

Eimeria tenella sporozoites were inoculated into partially confluent primary chick kidney cell cultures. Counts were made of the number of intracellular sporozoites at 4 and 24 hr, and oocysts at 6 and 7 days in cultures inoculated and maintained under a variety of conditions. By using ( 1 ) a single medium composed of 90% Hanks' balanced salt solution, 5% lactalbumin hydrolysate (2.5% solution in Hanks' BSS), and 5% fetal calf serum for growth of cells, inoculation of sporozoites, and maintenance of cells, (2) sporozoite suspensions free of debris, and (3) 10 rather than 2 ml of media for maintaining the cultures, an OI (oocyst index, or relationship between intracellular oocysts at 6 or 7 days and sporozoites at 4 hr) was obtained that was nearly 7 times greater than that obtained using the procedure previously described (Doran, 1970c). In a previous report (Doran, 1970c), it was shown that Eimeria tenella undergoes its complete life cycle from excysted sporozoites to viable oocysts in primaly cell cultures of embryonic and nonembiyonic chick kidney. This report pertains to the effect of media, size of the sporozoite inoculum, and sporozoite inocula freed of debris (oocyst and sporocyst walls), on infection of primary chick kidney cells and subsequent production of oocysts. It shows how a greater yield of oocysts is obtained by altering the growth conditions for cells and eliminating certain of the procedures previously used. MATERIALS AND METHODS