Protection of goldfish against Ichthyophthirius multifiliis by immunization with a recombinant vaccine

Abstract

A 316 bp gene fragment containing a potential antigenic epitope of the 48 kDa immobilization antigen of Ichthyophthirius multifiliis (i-AgI) was assembled from six synthetic oligonucleotides and cloned into a bacterial expression vector pGEX2T. The gene construct was introduced into Escherichia coli and the glutathione S-transferase-iAgI (GST-iAgI) fusion protein was successfully expressed. Antisera against GST-iAgI fusion protein from catfish showed a positive reaction with a tomites protein of about 48 kDa, suggesting that the recombinant protein contains an antigenic epitope of i-AgI. Naive goldfish that were immunized with purified GST-iAgI fusion protein were challenged with a lethal dose of infectious tomites of I. multifiliis. The results showed that the average survival rate of the immunized fish was 95% as compared to 55% for the control fish. All these findings suggest that the recombinant GST-iAgI fusion protein can be used as a potential vaccine against the infection of I. multifiliis.