A panel of six monoclonal antibodies (MAbs) against eel virus European (EVE) isolated from eel (Anguilla japonica) with branchionephritis was established in the present study. These systems have been applied for a rapid identification and presumptive serotyping of aquatic birnavirus isolates using western immunoblot assay. Amongst these six MAbs, four were demonstrated to be able to react with viralγ-polypeptide, whereas the other two were specific to viralβ-polypeptide. Three MAbs identified epitopes that were highly conserved among members of AB serotype. One MAb recognized an epitope present on AB and SP serotype strains. Two MAbs exhibit the common epitopes observed on AB, SP and VR299 serotypes of infectious pancreatic necrosis virus (IPNV). One of these two MAbs could react with all aquatic birnavirus isolates from various areas including Asia, North America and Europe. Six isolates from Asia exhibiting five varying reaction patterns were demonstrated to be distinct from AB, SP and VR299 serotypes.
Infestation of juvenile gnathiids, Gnathia sp., on the branchial chamber wall of two species of stingrays, Dasyatis akajei and D. matsubarai, caused proliferative inflammation of dermal tissue, and a heavy disruption of epithelia and smooth muscles. In addition to congestion of hemolytic blood cells, a prominent aggregation of heterophils, macrophages engaged in active phagocytosis, and plasma cells was also seen. It is of interest to note that evidence of a remarkable propagation of bacilli was encountered on the surface of the gnathiids and on the injured mucosal coat of the host fish. Besides a lot of blood sucking by gnathiids, bacterial infection might be one of the causes of host fish death or debility.
Aeromonas salmonicida salmoysin was detoxified by heating at 37°C for 24 h, at 60°C for 30 min, at 100°C for 5 min, or heating at 37 or 60°C for 30 min with 0.4 % (v/v) formalin. These detoxified salmolysins and native salmolysin reacted with rabbit anti-native salmolysin serum. Juvenile white-spotted char (Salvelinus leucomaenis) were immunized two times at two-week intervals by intramuscular injection of salmolysin which was detoxified by heating at 60°C for 30 min. Mortalities of immunized and control fishes after challenge were 28.6 and 62.5 %, respectively. An antibody to salmolysin was detected in immunized fish sera, but not detected in control fish sera.These results indicate that detoxified salmolysin is an effective immunogen for the prevention of furunculosis in white-spotted char.
An outbreak of so-called dropsy occurred among juvenile Japanese char, Salvelinus leucomaenis, in the hatchery of Okutama Branch, the Tokyo Metropolitan Fisheries Experiment Station in April 1990. More than 90% of 20, 000 juvenile char showed dropsy, and numerous bacterial colonies were observed on the gill surface of the fish under microscope. Examination of Bouin or formalinefixed samples revealed that such bacterial colonies were also associated with outbreaks of dropsy in juvenile char in other places in April 1988 and February 1990. We found that 1% salt water bath for 1 hour is effective to eliminate the bacteria from the gills of diseased fish, and a continuous treatment for 8 days with 1 % salt water bath is effective to cure the dropsy. These results suggest that the bacteria observed on the gills might be the causative agent of the dropsy of juvenile Japanese char, but all attempts of infection trials failed to substantiate it. Further works concerning the relationships between bacterial attachment and dropsy will be required.
Effects of various concentrations of specific immune serum on phagocytosis and phagocytosisassociated chemiluminescent (CL) responses were investigated with sheep red blood cells (SRBC) and rainbow trout (Oncorhynchus mykiss) phagocytic cells. When heat-inactivated rainbow trout anti-SRBC serum was used to opsonize SRBC, rates of phagocytic ingestion of SRBC by phagocytes increased with lower dilutions of the antiserum, and CL activities also rose with lower dilutions of the antiserum. The number of phagocytized SRBC per phagocyte increased in response to concentrations of the antiserum. These results indicate that CL response correlates with phagocytosis of which the activity depends on the concentration of specific immune serum used as an opsonin.
The existence of glycogen phosphorylase and glycogen synthetase was histochemically demonstrated in the neutrophils of eel (Anguilla japonica) under inflammatory condition by the reaction of polysaccharide derived from glucose-1-phosphate or uridine diphosphate glucose with iodine and PAS, respectively. The enzyme activities were also determined in the peripheral and pronephros neutrophils obtained from the fish after an intraperitoneal injection of formalinkilled Edwardsiella tarda or physiological saline. The activity of the glycogen phosphorylase was measured by the amount of the released inorganic phosphate from glucose-1-phosphate, and that of the glycogen synthetase by the amount of the released uridine diphosphate from uridine diphosphate glucose. In the pronephros neutrophils from the fish injected with formalin-killed E. tarda, the reaction of glycogen phosphorylase became prominent between 24 and 48 hours after injection, while that of glycogen synthetase increased conspicuously from 3 hours. But there were no significant differences in the reactions of two enzymes between the control fish injected with physiological saline and normal fish. The activities of glycogen phosphorylase and glycogen synthetase in the peripheral neutrophils did not differ between the bacteria-injected and control fish, but those, especially D-form of glycogen synthetase, in the pronephros neutrophils were greatly increased in the bacteria-injected fish. From the results of histochemical reactions and enzyme activities of these two enzymes, it is suggested that the increase in glycogen contents of neutrophils under inflammatory condition resulted from the activation of D-form of glycogen synthetase which had been achieved in the pronephron before being emigrated into the peripheral blood.