Eimeria Tenella Rhoptry Neck Protein 2 Plays a Key Role in the Process of Invading the Host Intestinal Epithelium

Abstract

The Apicomplexa parasitic phylum rhoptry neck protein 2 (RON2) plays a key role in the process of invading host cells. Eimeria tenella, an intracellular protozoan shares a similar conserved invasion pattern. However, whether E. tenella RON2 participates in the process of invading the host intestinal epithelium is poorly understood. In this study, the sequence of EtRON2 was analyzed and expressed. The expression of the truncated extracellular N-terminal fragment of EtRON2 (403-700 aa, designated EtRON2403-700) with a molecular mass of 38.3 kDa. EtRON2 in the sporozoite protein was detected at 151.4 kDa by rabbit anti-rEtRON2403-700 antibody. Immunofluorescence results showed that EtRON2 was mainly localized to the nucleus and apex of the E. tenella sporozoite. qPCR results showed that the highest expression level of EtRON2 was detected in sporulated oocysts compared with other developmental stages of E. tenella. In vitro invasion inhibition assays showed that the capacity of sporozoites to invade DF-1 cells was significantly inhibited after pretreatment with the rabbit anti-rEtRON2403-700 antibody. Silencing the EtRON2 gene by RNA interference (RNAi) significantly decreased the expression levels of EtRON2, resulting in the inhibition of sporozoite invasion of the host cells both in vivo and in vitro. Recombinant EtRON2403-700 (rEtRON2403-700) immunizes chicks effectively against E. tenella infection by inducing humoral immunity and upregulating CD8+ T lymphocytes. In conclusion, the results of this study demonstrated that EtRON2 plays a key role in E. tenella invasion of the host intestinal epithelium and provides a potential target for vaccines against E. tenella infection.

Keywords: Eimeria tenella, rhoptry neck protein 2, invasion protein, RNAi, immunoprotection