Ribosomal protein L27 contributes to virulence and maduramicin resistance in Eimeria tenella

Coccidiosis, which is primarily caused by Eimeria spp., poses a persistent challenge to poultry health and production worldwide. The emergence and spread of drug-resistant strains have significantly compromised the efficacy of anticoccidial therapies. We previously used RNA-seq to demonstrate that ribosomal protein L27 is differentially expressed in drug-sensitive and maduramicin-resistant strains of E. tenella (EtRPL27). In the present study, an RT–qPCR analysis showed that its expression is stage-specific, with the highest levels in sporozoites and second-generation merozoites. Immunofluorescence revealed both the cytoplasmic and partial surface localization of EtRPL27. Notably, EtRPL27 transcript levels were significantly elevated in a maduramicin-resistant strain relative to the drug-sensitive strain. Functional assays showed that anti-EtRPL27 antibodies inhibited the invasion of sporozoites, whereas the transgenic overexpression of EtRPL27 enhanced both the invasion efficiency and pathogenicity of E. tenella in chickens. Importantly, EtRPL27 overexpression reduced its sensitivity to maduramicin, evident as increased oocyst output and a higher anticoccidial index. Resistance classification based on standard indices confirmed moderate-to-high resistance levels in the EtRPL27-overexpressing strain. These findings demonstrate that EtRPL27 is closely associated with both virulence and maduramicin resistance in E. tenella, indicating its potential utility as a molecular marker and therapeutic target.