Antigenic characterization of Sphaerospora dicentrarchi (Myxosporea : Bivalvulida), a parasite from European sea bass Dicentrarchus labrax (Teleostei: Serranidae)

The biochemical composition of Sphaerospora dicentrarchi was studied. Perio date and Proteinase K treatments as well as lectin blots were used to analy se carbohydrate terminals. Zymography was applied to detect proteases. Four polyclonal antisera, raised against S. dicentrarchi (RaSdic), S, testicula ris (RaStest), Ceratomyxa labracis (RaClab) and C. sparusaurati (RaCspr), w ere used in SDS polyacrylamide gel electrophoresis and immunoblot. Bands wi th molecular weight (MW) between 32 and 130 kDa were detected by electropho resis. After Proteinase K treatment, apparent digestion of bands heavier th an 43 kDa took place. RaSdic and RaStest detected similar bands with MW bet ween 20 and 50 kDa, whereas RaClab and RaCspr recognized bands between 50 a nd 140 kDa. The 50 kDa band was recognized by all the polyclonal antisera, suggesting that it could correspond to an antigen shared by several myxospo rean parasites. Four proteases were observed by zymography. From the 5 lect ins assayed, binding was only observed using Con-A, which detected 2 bands of 96 and 78 kDa. Periodate treatment did not produce any effect on the bin ding of RaSdic and RaStest, but a high decrease of intensity in the antibod y binding occurred at a concentration of 10 and 20 mM periodate when RaClab and RaCspr were tested. These results give information on the antigenic co mposition of S. dicentrarchi which could be useful for further diagnostic o r immunoprevention studies.