Comparison of lymphocystis disease virus (LCDV) isolates obtained from different marine fish species and geographical areas

Seven lymphocystis disease viruses isolated from dab, flounder and plaice in Northern Europe, and from gilt-head sea bream, Senegalese sole and blackspot sea bream in Southern Europe have been comparatively studied by inoculation on different fish cell lines. Viral isolates induced cytopathic effects (CPE) only on fibroblastic cells, and differences in the incubation time necessary to develop CPE, as well as in viral titre were observed in relation to the geographical area of isolation rather than to the host fish species. In addition, the pattern of the major viral proteins from different fish species in the same area was similar; however, North European isolates showed three major proteins which were absent in the South European viruses. Immunohistochemistry techniques were used to detect LCDV in infected cells, the antibody used (developed against a gilt-head sea bream LCDV) did not react with any of the North European isolates, whereas those cells infected with the South European isolates showed an intensive labelling. The results suggest that these viral isolates constitute two homogeneous groups referring to the geographical area of isolation, rather than to the fish species affected.