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 ( Et RPL27). 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 Et RPL27. Notably, Et RPL27 transcript levels were significantly elevated in a maduramicin-resistant strain relative to the drug-sensitive strain. Functional assays showed that anti- Et RPL27 antibodies inhibited the invasion of sporozoites, whereas the transgenic overexpression of Et RPL27 enhanced both the invasion efficiency and pathogenicity of E. tenella in chickens. Importantly, Et RPL27 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 Et RPL27-overexpressing strain. These findings demonstrate that Et RPL27 is closely associated with both virulence and maduramicin resistance in E. tenella, indicating its potential utility as a molecular marker and therapeutic target.