Proteomic analysis of Trichinella spiralis adult worm excretory-secretory proteins recognized by early infection sera

At the intestinal stage of a Trichinella spiralis (T. spiralis) infection, the excretory-secretory (ES) antigens produced by adult worms (AWs) result in an early exposure to the host's immune system and elicit the production of specific antibodies; the AW ES proteins might provide early diagnostic markers of trichinellosis. The aim of this study was to identify early serodiagnostic markers from T. spiralis AW ES antigens. T. spiralis AWs were collected at 72 h post infection, and their ES antigens were analysed by SDS-PAGE and Western blot. Then, the immunoreactive bands were subjected to shotgun LC-MS/MS and bioinformatics analyses. Our results showed that only one protein band (33 kDa) was recognized by the sera of mice infected with T. spiralis at 8 days after infection. The shotgun LC-MS/MS analysis identified 23 proteins that were then clustered into 10 types; these proteins had molecular weights of 28.13-71.62 kDa and pI 5.05-9.20. Certain enzymes (e.g., serine protease, adult-specific deoxyribonuclease [DNase] II, peptidase S1A subfamily, and multi cystatin-like domain protein) were found to be highly represented. The functions of the 10 proteins were further analysed: of the 6 annotated proteins, 3 had serine hydrolase activity and 2 had DNase II activity. These results provide a valuable basis for identifying early diagnostic antigens and vaccine candidates for trichinellosis.