Salmonid cryptobiosis is caused by the haemoflagellate, Cryptobia Trypanoplasma salmosit-
ica Katz 1951. The parasite has been reported from all species of Pacific Oncorhynchus spp. on the west coast of North America. It is recognized as a lethal pathogen in semi-natural and intensive salmon culture facilities, and there is no chemotherapy against the parasite. Innate and acquired immunity have been successfully exploited to experimentally protect susceptible fish. The third approach in the protective strategy is to use monoclonal antibody technology to develop a sensitive technique for the detection of parasite antigen, and to identify a protective monoclonal
. antibody and its epitope. A murine IgG3 monoclonal antibody MAb-007 against the 47 kDa
polypeptide of C. salmositica was used to develop an antigen-capture ELISA diagnostic technique. The reactions were negative before infection or vaccination, but were positive 1–9 weeks after infection with the pathogen or vaccination with an attenuated strain. MAb-007 recognizes a cytoplasmic epitope, which is excretedrsecreted by living parasites. Another murine monoclonal
. antibody MAb-001 , an IgG1, was produced against an outer surface 200 kDa membrane
. glycoprotein Cs-gp200 . This glycoprotein epitope is specific to C. salmositica, and attaches to
the surface membrane by a phospholipid anchor. MAb-001 agglutinates the parasite but does not fix complement. The antibody inhibits the activities of both cysteine and metallo-proteases from the pathogen. Parasites coated with MAb-001 do not multiply in culture, and they die in about 3 weeks. The infectivity of antibody-coated parasite to fish was also significantly decreased. Also, MAb-001 injected intraperitoneally into fish with acute disease significantly lowered the para-
. sitaemias 60–80% within 48 h. This monoclonal antibody is species specific.