EtG6PI Is Implicated in Host Cell Invasion and Maduramycin Resistance in Eimeria tenella

Chicken coccidiosis, caused by obligate intracellular protozoa of the genus Eimeria, inflicts substantial economic losses on the global poultry industry. The extensive use of anticoccidial drugs has led to widespread resistance, underscoring the need for molecular markers associated with this resistance. Our previous RNA-seq analysis revealed differential expressions of glucose-6-phosphate isomerase (EtG6PI) between drug-sensitive (DS) and maduramycin-resistant (MRR) strains of Eimeria tenella. In this study, we examined EtG6PI expression across developmental stages using qPCR and Western blotting, finding that both transcription and translation peaked in second-generation merozoites. Furthermore, EtG6PI expression was significantly upregulated in MRR strains in a dose-dependent manner and was also elevated in field isolates exhibiting maduramycin resistance. Indirect immunofluorescence localized EtG6PI to the parasite surface, cytoplasm, and parasitophorous vacuole membrane (PVM), with signal intensity increasing during intracellular development. In addition, anti-rEtG6PI polyclonal antibodies significantly inhibited sporozoite invasion of host cells in vitro. These results indicate that EtG6PI plays a role in host cell invasion, a process essential for parasite proliferation, and is associated with maduramycin resistance in E. tenella, supporting its potential as a biomarker for resistance detection in field settings.