Molecular characterization of a putative serine protease from Trichinella spiralis and its elicited immune protection

Ge Ge Sun,Yan Yan Song,Zhong Quan Wang,Xin Qi,Chen Xi Hu,Xi Zhang,Ruo Dan Liu,Peng Jiang,Fan Yang,Jing Cui,Hua Nan Ren

doi:10.1186/s13567-018-0555-5

Abstract

In our previous work, a Trichinella spiralis putative serine protease (TsSP) was identified from ES products of T. spiralis intestinal infective larvae (IIL) and adult worms (AW) by immunoproteomics: it was highly expressed in IIL compared with muscle larvae (ML). In this study, the TsSP biological characteristics in larval invasion and growth were identified and its potential as a vaccine target against Trichinella infection were investigated. Expression of TsSP at various developmental phases (newborn larvae, ML, IIL, and AW) was detected by qPCR, immunofluorescent test and Western blotting. The rTsSP could specifically bind to the intestinal epithelial cell (IEC) membrane and enter into the cytoplasm. Anti-rTsSP serum suppressed the larval invasion of enterocytes in a dose-dependent mode, and killed newborn and ML of T. spiralis, decreased larval infectivity and development in the host by an ADCC-mediated mechanism. Immunization of mice with rTsSP produced a Th2 predominant immune response, and resulted in a 52.70% reduction of adult worms at 5 days post-infection (dpi) and a 52.10% reduction of muscle larvae at 42 dpi. The results revealed there was an interaction between TsSP and the host’s IEC; TsSP might be a pivotal protein for the invading, growing and parasiting of this nematode in the host. Vaccination of mice with rTsSP elicited immune protection, and TsSP is a potential target molecule for vaccines against enteral Trichinella infection.

Highlights

Trichinellosis is an important zoonotic parasitic disease worldwide, especially in developing countries [1]
The infective larvae (IIL) were separated from the intestines of mice infected orally with 5000 muscle larvae (ML) at 6 hours post-infection, and adult worms (AW) was isolated from the intestines at 3 and 6 dpi, respectively
Results quantitative PCR (qPCR) analysis of Trichinella spiralis putative serine protease (TsSP) gene transcription at different stages The TsSP gene transcription in various stages of T. spiralis was determined by qPCR

Summary

Introduction

Trichinellosis is an important zoonotic parasitic disease worldwide, especially in developing countries [1]. Trichinella infection in animals and humans is recorded in 66 countries all over the world, and has been regarded as an emerging or re-emerging zoonotic disease [3]. Trichinella spiralis is the major etiological agent of Trichinella infection in humans, and its main reservoir is domestic pigs [4]. In China, 15 outbreaks of human trichinellosis were reported during 2004–2009, pork and pork-related products were the main sources of infection [5,6,7]. Trichinella infection in domestic pigs is a major public hygiene problem and hazard animal food safety [8]. There are increasing cosmopolitan demands for reliable preventive measures for Trichinella infection in food animals to ensure meat safety [9]. The exploitation of vaccines to prevent domestic swine from Trichinella infection is a promising measure for the control of this zoonosis [10,11,12,13]

Methods

Results

Conclusion