Aquaculture Aquaculture 158 (1997) I-10 Protection of goldfish against Ichthyophthirius multifiliis by immunization with a recombinant vaccine Jiangyan He, Zhan Yin, Guoliang Xu, Zhiyuan Gong, Toong Jin Lam, Yoke Min Sin * School of Biological Sciences, National Unic,ersity of Singapore, IO Kent Ridge Crescent, Singapore 119260, Singapore Accepted 21 March 1997 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQ Abstract A 3 I6 bp gene fragment containing a potential antigenic epitope of the 48 kDa immobilization antigen of Ichth_vophthirius multifiliis (i-AgI) was assembled from six synthetic ohgonucleotides and cloned into a bacterial expression vector pGEX2T. The gene construct was introduced into Escherichiu coli and the glutathione S-transferase-iAgI (GST-iAg1) fusion protein was success- fully expressed. Antisera against GST-iAg1 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-iAg1 fusion protein were challenged with a lethal dose of infectious tomites of I. mulrijiliis. 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-iAg1 fusion protein can be used as a potential vaccine against the infection of I. multi@Iiis. 0 1997 Published by Elsevier Science B.V. Keywords: lchth,vophthirius multifiliis; Immune protection; Recombinant vaccine 1. Introduction Ichthyophthirius mulitifiliis Fouquet 1876 is a ciliated protozoan parasite that is commonly found in gills and dermis of freshwater fish. The disease induced by the parasite is known as white-spot or ‘ich’, which has caused heavy economic losses in * Corresponding author. Fax: 65 7792486. E-mail: sbssinym@nus.sg. 0044-8486/97/$17.00 0 1997 Published by Elsevier Science B.V. All rights reserved PII SOO44-8486(97)00074-4