DAO 29:67-72 (1997)  -  doi:10.3354/dao029067

In vivo neutralization of Cryptobia salmositica metallo-protease by alpha2-macroglobulin in the blood of rainbow trout Oncorhynchus mykiss and in brook charr Salvelinus fontinalis

Zuo X, Woo PTK

Cryptobia salmositica infects both rainbow trout Oncorhynchus mykiss and brook charr Salvelinus fontinalis, but it does not cause disease (e.g. anaemia) in brook charr. The natural antiprotease, alpha2-macroglobulin (alpha2-M), was found in the blood of rainbow trout and brook charr, but it had much higher activity in brook charr. Under in vivo conditions, alpha2-M of trout and charr were neutralized by C. salmositica extracellular protease. The onset and persistence of anaemia in infected rainbow trout were related to low levels of alpha2-M. Infected brook charr did not develop anaemia as alpha2-M remained high during the infection. Secreted metallo-protease of C. salmositica was detected in the blood of infected rainbow trout when its alpha2-M was low and the fish was anaemic; however, metallo-protease was not detected in infected brook charr. We suggest that host alpha2-M plays an important role in defense against cryptobiosis by inhibiting the activity of metallo-protease secreted by the pathogenic C. salmositica.


alpha2-macroglobulin · Oncorhynchus mykiss · Salvelinus fontinalis · Cryptobia salmositica · Protease


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