Carp pox, a putative viral disease exotic to North America, occurred in golden ide 1 yr after the fish were imported into the United States from the Federal Republic of Germany. The raised, white, plaque-like lesions, which occurred on about 5% of the fish, healed spontaneously and caused no mortality. Electron micrographs showed herpesvirus-like particles associated with lesion specimens; however, no infectious viruses were detected in tests with seven warmwater fish cell lines.

A hybridoma cell line that continually secretes antibody against infectious hematopoietic necrosis virus was developed and designated M-IHNV-W1. Antibodies in culture fluids were concentrated and purified by Protein A Sepharose CL-4B affinity chromatography. The immunoglobulin was isotyped as IgG 2b with a kappa light chain. The IgG was specific for infectious hematopoietic necrosis virus and had binding activity but low neutralizing activity. Little cross-reactivity occurred with viral hemorrhagic septicemia or infectious pancreatic necrosis viruses.

Affinity purified monoclonal antibody was biotinylated and used with avidin-labeled peroxidase in an immunoblot assay to detect infectious hematopoietic necrosis virus (IHNV). The procedure proved capable of detecting the virus a titers a s low as ca 10"laque forming units (PFUs) ml-' of cell culture fluid, which corresponds to about 102 PFUs spotted onto the immunoblot assay matrix. Time course studies showed that the detection of IHNV antigen in cell culture by inlmunoblot assay was directly related to the concentration of virus in the inoculum and that positive in~munoblot reactions coincided with the appearance of cytopathic changes in inoculated cell cultures. We used the immunoblot assay to detect and identify IHNV antigen in medium from cells inoculated with ovarian fluids. Immunoblot assay was not suitable for detecting IHNV in raw ovarian fluid. When ovarian fluids from IHNV-negative chinook salmon Oncorhynchus tshawytscha and steelhead trout 0. mykiss were assayed by the immunoblot method, false positive reactions results from the binding of monoclonal antibody to some of the ovarian fluid proteins. The advantages and limitations of the assay are discussed.

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Differential incorporation of uridine and uracil was used to assay for mycoplasma contamination in five fish cell lines: bluegill fry (BF-2), chinook salmon embryo {CHSE-214), epithelioma papillosum cyprini (EPC), fathead minnow (FHM) and rainbow trout gonad (RTG-2). The method was not suitable for monitoring BF-2, CHSE-214, FHM, and RTG-2 cell lines because they incorporated uracil. Differential incorporation of uridine and uracil may be applicable for screening EPC cells because only this cell line could distinguish cultures experimentally infected with Mycoplasma orale from cultures known to be free from microbial contaminants.Correspondence; Dr P. E. McAllister,