EtMIC3 and its receptors BAG1 and ENDOUL are essential for site-specific invasion of Eimeria tenella in chickens

Abstract

Avian coccidian parasites exhibit a high degree of site specificity in different Eimeria species. Although the underlying mechanism is unclear, an increasing body of evidence suggests that site specificity is due to the interaction between microneme proteins (MICs) and their receptors on the surface of target host cells. In this study, the binding ability of E. tenella MICs (EtMICs) to different intestinal tissue was observed by immunofluorescence to identify the key surface molecule on the parasite responsible for the site specificity. Subsequently, we identified the corresponding host-cell receptors by yeast two-hybrid screening and glutathione-S-transferase pull-down experiments and the distribution of these receptors was observed by immunofluorescence in chicken intestinal tissues. Finally, we evaluated the efficacy of receptor antiserum against the infection of E. tenella in chickens. The results showed that EtMIC3 could only bind to the caecum while EtMIC1, EtMIC2, and EtAMA1 did not bind to any other intestinal tissues. Anti-serum to EtMIC3 was able to block the invasion of sporozoites with a blocking rate of 66.3%. The receptors for EtMIC3 were BCL2-associated athanogene 1 (BAG1) and Endonuclease polyU-specific-like (ENDOUL), which were mainly distributed in the caecum. BAG1 and ENDOUL receptor antiserum reduced weight loss and oocyst output following E. tenella infection, showing partial inhibition of E. tenella infection. These data elucidate the mechanism of site specificity for Eimeria infection and reveal a potential therapeutic avenue.

Dual RNA-Seq transcriptome analysis of chicken macrophage-like cells (HD11) infected in vitro with Eimeria tenella

“…MIC, we found a similar pattern to the other E. tenella genes, some were strongly downregulated across time points such as two versions of AMA1 , and others appeared to be focused in the merozoites, such as AMA1_iso1 and EtMIC3 . Interestingly, EtMIC3 has been pointed out as important for E. tenella tissue specificity to the caecum (Li et al ., 2020 ). In the case of the AMA1 paralogues, AMA1 and AMA1_iso2 both were expressed across all time points in the present study, though downregulated, while AMA1_iso1 was almost exclusively expressed in the late time points.…”

Protective Efficacy of Rhomboid-Like Protein 3 as a Candidate Antigen Against Eimeria maxima in Chickens

“…The proteins involved in host-cell invasion have been proposed as promising vaccine candidates ( Vermeulen, 1998 ). Microneme proteins (MICs), for example, function in the adhesion to the host cell during invasion by coccidian parasites and exhibit promising protective efficacy against infection by Eimeria species ( Carruthers and Tomley, 2008 ; Cowper et al, 2012 ; Li et al, 2020 ). Lai et al (2011) reported that MIC3 from Eimeria tenella (EtMIC3) contributed greatly to the cecal tissue tropism of E. tenella in early invasion ( Lai et al, 2011 ).…”

Specific EtMIC3-binding peptides inhibit Eimeria tenella sporozoites entry into host cells

“…It has been shown that EtMIC3 protein consists of seven microneme adhesive repeats (MARs), including four highly conserved internal repeats and three divergent external repeats [ 7 , 25 ]. EtMIC3 contributes to guiding and binding sporozoites to the invasion site in chicken intestinal tract by recognizing BCL2-associated athanogene 1 (BAG1) and Endonuclease polyU-specific-like (ENDOUL) [ 26 ], and sialylated glycans [ 12 , 13 ]. It was reported that AMA1-binding peptides effectively inhibited T. gondii, P. falciparum and E. tenella invasion into host cells [ 14 , 27 , 28 ].…”