Peptides Associated with Monensin Resistance in Sporozoites of Eimeria tenella (Coccidia)

Abstract

Resistance to monensin in the sporozoites of a laboratory strain (WIS) of Eimeria tenella was amplified by treating free sporozoites with increased monensin levels in vitro, followed by propagation of these treated sporozoites in chickens. The parent strain of WIS and its subsequent lines developed from the treatment of monensin at 1, 5, or 25 micrograms/ml were designated as WIS(0), WIS(1), WIS(5), or WIS(25), respectively. The penetration rate of sporozoites into primary chicken kidney cell cultures showed that the sensitivity of sporozoites to the treatment of monensin at 1 and 5 micrograms/ml was significantly reduced in the WIS(25) line in comparison with the WIS(0) line. When native polyacrylamide gel electrophoresis (PAGE) was conducted, a change in the relative mobility of a protein band was found in the protein samples of these coccidial lines. Sodium dodecyl sulfate PAGE revealed that 2 peptides with molecular weights of approximately 50.0 and 31.4 kDa were present in the sporozoites of resistant lines but undetectable in their WIS-parent sporozoites. Derivation of the resistant lines from a drug-sensitive parent line gave strong support to a link between the appearance of the peptides and resistance to ionophores in this strain of E. tenella.