Humoral immune responses of antibacterial hemocyanin (Ab-Hcy) in mud crab, Scylla serrata

Hemocyanins are large extracellular respiratory proteins distributed within the hemolymph of arthropods, molluscs and larval stages of certain insects. In the present study, we characterized the humoral immune functions of cation specific antibacterial hemocyanin (Ab-Hcy) from mud crab, S. serrata. The bacteriolytic activity of Ab-Hcy was against pathogenic and non-pathogenic to crustaceans which includes, Bacillus sp. N1, B. flexus N3, E. coli, P. aeruginosa, V. harveyi, V. parahaemolyticus and V. vulnificus and also expressed bacteriostatic activity against E. coli, B. flexus N3 and V. harveyi. The agglutination activity of Ab-Hcy ranged from 4-16 against B. flexus N3, E. coli, V. harveyi and V. vulnificus and Ab-Hcy also agglutinated with rat and human O erythrocytes (HA titer: 2). The Ab-Hcy lysed the panel of mammalian erythrocytes and strong hemolytic activity of 1.40, 1.28 and 1.22 units.min(-1) . mg protein(-1) against human A, B and O erythrocytes respectively. It was also found that the Ab-Hcy possess phenoloxidase (PO) activity by oxidizing L-DOPA. These results suggest that Ab-Hcy from the serumofmud crab, S. serrata, is capable of performing multiple humoral immune functions in addition to oxygen transportation. Statement of relevance: This manuscript deals with the humoral immune functions, particularly antibacterial property of hemocyanin in crustacean. In this paper we report the different type of antibacterial activity and other humoral immune functions of a hemocyanin isolated from the serum of mud crab, Scylla serrata. This work will help to understand the role of respiratory molecule in immune system, also will be helpful improve disease free crustacean aquaculture industry. And we also state this research work is relevant and suitable to publish in the Journal Aquaculture. (C) 2016 Elsevier B.V. All rights reserved.