One of cause of industrial loss in grouper cultured is VNN attack. VNN causes retinopathy and encephalopathy which having wide host range. It is included one of epidemic disease almost in the world and inscribed in OIE (Office International des Epizooties). VNN is reported to attack some fish species as Japanese parrot fish (Oplegnathus fasciatus), redspotted grouper (Epinephelus akaara), striped jack (Pseudocaranxdentex), Japanese flounder (Paralichthys olivaeeus), tiger puffer (Takifugu rubripes), kelp grouper (Epinephelus moara) and barfin flounder (Verasper moseri), barramundi (Lates calcarifer), turbot (Scophthalmus maximus) and sea bass (Dicentrarchus labrax).
Humpback Grouper In Indonesia, it is reported that VNN has attacked most of grouper cultured with mortality of 100%. In East Java, seeding industry also get a loss as result of VNN attack in seed stadium and even in adult (data is not publicized). The symptom is fish whirling, happened sleeping dead or fish resides in base like death and existence of unnatural fish behavior symptom.
Important role of defense system of grouper to VNN is receptor protein expressed at part of grouper body. VNN target on grouper are eye, brain, kidney, flesh, liver and also gill. In this research, it will be seen VNN infection in grouper brain as agent that is very endangers because VNN can weaken fish nervous system so that fish will loss nervous control, happened weakness of motion, and finally death. The role of nervous cells to VNN agent is target of protein receptor which is important to neutralize VNN besides other organ as heart and kidney that functions for circulation and osmoregulation of blood in body fish.
Something that causes the mechanism of this viral infection is the bonding between VNN adhesin and its receptor molecule in grouper organs. Viral adhesin can be in the form of viral basic component namely coat protein and nucleic acid. Coat protein of VNN is primary factor in mechanism of virus infect the host (humpback grouper) where the protein have a role in attachment of viral to host receptor. It has been known that one of adhesin of VNN is haemaglutinin. Further development both adhesin and its receptor can be exploited to produce a protein material for a diagnostic tools to virus infection and so its prevention for fish cultured industry. For this purpose, the research objective is to identify how a role and expression of receptor protein from grouper brain, heart and kidney mediated by nervous, heart and nephrose cells in infection mechanism of VNN.
Characteristics of the humpback grouper, Cromileptes altivelis Common names: Humpback grouper, panther grouper, mouse grouper, highfin grouper. Size and age: Max size 70.0 cm TL. Environment: Reef-associated; marine; depth range 2–40 m. Climate: Tropical; 32°N - 23°S, 88°E - 168°E Importance: Juveniles are commonly caught for the aquarium trade while adults are utilized as a food fish. Very high value in China Hong Kong SAR live fish markets. Resilience: Low, minimum population doubling time 4.5–14 years. Biology and ecology: Generally inhabits lagoon and seaward reefs and are typically found in dead or silty areas. Also found around coral reefs and in tide pools. Growth is very slow. Feed on small fishes and crustaceans.