Molecular cloning and characterization of a novel peptidase fromTrichinella spiralisand protective immunity elicited by the peptidase in BALB/c mice

In our previous studies, a novelT. spiralispeptidase (TsP) was identified among the excretory/secretory (ES) proteins ofT. spiralisintestinal infective larvae (IIL) andT. spiralisat the adult worm (AW) stage using immunoproteomics, but the biological function of TsP in the life cycle ofT. spiralisis not clear. The objective of this study was to investigate the biological properties and functions of TsP in larval intrusion and protective immunity induced by immunization with rTsP. The complete TsP cDNA sequence was cloned and expressed. The results of RT-PCR, indirect immunofluorescence assay (IIFA) and western blotting revealed that TsP is a surface and secretory protein expressed inT. spiralisat different stages (muscle larvae, IIL, AWs and newborn larvae) that is principally localized at the epicuticle of the nematode. rTsP facilitated the larval intrusion of intestinal epithelial cells (IECs) and intestinal mucosa, whereas anti-rTsP antibodies suppressed larval intrusion; these facilitative and suppressive roles were dose-dependently related to rTsP or anti-rTsP antibodies. Immunization of mice with rTsP triggered an obvious humoral immune response (high levels of IgG, IgG1/IgG2a, and sIgA) and also elicited systemic (spleen) and intestinal local mucosal (mesenteric lymph node) cellular immune responses, as demonstrated by an evident increase in the cytokines IFN-gamma and IL-4. Immunization of mice with rTsP reduced the numbers of intestinal adult worms by 38.6% and muscle larvae by 41.93%. These results demonstrate that TsP plays a vital role in the intrusion, development and survival ofT. spiralisin hosts and is a promising candidate target molecule for anti-Trichinellavaccines.