Immunological and Therapeutic Strategies against Salmonid Cryptobiosis

[摘要] Salmonid cryptobiosis is caused by the haemoflagellate,Cryptobia salmositica. Clinical signs of the disease in salmon (Oncorhynchusspp.) include exophthalmia, general oedema, abdominal distension with ascites, anaemia, and anorexia. The disease-causing factor is a metalloprotease and the monoclonal antibody (mAb-001) against it is therapeutic. MAb-001 does not fix complement but agglutinates the parasite. Some brook charr,Salvelinus fontinaliscannot be infected (Cryptobia-resistant); this resistance is controlled by a dominant Mendelian locus and is inherited. InCryptobia-resistant charr the pathogen is lysed via the Alternative Pathway of Complement Activation. However, some charr can be infected and they have high parasitaemias with no disease (Cryptobia-tolerant). In infectedCryptobia-tolerant charr the metalloprotease is neutralized by a natural antiprotease,α2 macroglobulin. Two vaccines have been developed. A single dose of the attenuated vaccine protects 100% of salmonids (juveniles and adults) for at least 24 months. Complement fixing antibody production and cell-mediated responsein vaccinated fish rise significantly after challenge. Fish injected with the DNA vaccine initially have slight anaemias butthey recover and have agglutinating antibodies. On challenge, DNA-vaccinated fish have lower parasitaemias, delayed peakparasitaemias and faster recoveries. Isometamidium chloride is therapeutic against the pathogen and its effectiveness isincreased after conjugation to antibodies.

[学科分类] 基础医学