DAO 64:121-126 (2005)  -  doi:10.3354/dao064121

Humoral immune responses of the grouper Epinephelus akaara against the microsporidium Glugea epinephelusis

J. Y. Zhang1,4, Y. S. Wu2, H. B. Wu3, J. G. Wang1,*, A. H. Li1, M. Li2

1State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences,Wuhan, Hubei 430072, PR China
2Institute of Tropical Medicine, The First Military Medical University, Guangzhou, Guangdong 510515, PR China
3South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong 510301, PR China
4Graduate School of the Chinese Academy of Sciences, Beijing 100039, PR China
*Corresponding author. Email:

ABSTRACT: The humoral immune responses of grouper Epinephelus akaara to a natural infection with Glugea epinephelusis was studied by ELISA utilizing intact mature spores as the coated antigen. Results showed that a specific humoral immune response was elicited, but the intensity of infection (in terms of the number of cysts) was not related to the antibody level in naturally infected hosts. The differences in the antigenicity of intact mature spores and soluble spore proteins derived from cracked mature spores were also analyzed. Results suggested that similar antigen epitopes existed between the 2 groups. Additionally, antigen component patterns and the distribution of antigen with immunogenicity were investigated by using the western blot and the immunofluorescent antibody technique (IFAT). The new parasitic microsporidium has specific polypeptide patterns comparable to the reported fish microsporidians. The main antigenic substances are concentrated on the surface of spores, and are mostly located on the anterior and posterior end of the spore bodies. Most surface components of the G. epinephelusis spores are soluble. The potential role of the surface components in initiating infection was also discussed.

KEY WORDS: Glugea epinephelusis · Microsporidia · Epinephelus akaara · Humoral immune responses · antigenicity

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