Studies on proliferative kidney disease using monoclonal antibody probes.

Abstract

Four monoclonal antibody (MAb) probes were produced which reacted against PK’X’ the causative agent of proliferative kidney disease in salmonids. Three of the MAbs appeared to be specific for carbohydrate epitopes whilst the fourth appeared to recognise a protein epitope. These probes were utilised to investigate the progression of the disease in rainbow trout, examine possible alternative hosts/ infective agents for the disease and to explore a novel method of purification for the PK’X’ cell. Purification of PK’X’ from kidney homogenates was investigated using immunomagnetism. The success of this was hampered by lymphocytes and macrophages adhering to the parasites’ surface. Incubations using detergents, trypsin, sonication and osmotic shock were employed to remove these cells with varying degrees of success. The course of the infection in rainbow trout was studied using immunohistochemistry on tissues sampled throughout the summer. This revealed that the antigenic characteristics of PK’X’ changed, with an intensification of staining of the carbohydrate binding MAbs on extrasporogonic stages and the protein binding MAb recognising secondary cells and sporogonic stages. Immunogold electron microscopy revealed that the carbohydrate binding MAbs were specific for the lysosomal membranes in the primary cell of the parasite whilst the protein binding MAb reacted to the surface of the secondary cell, vacuoles contained within it and this cell’s immediate surroundings. It was speculated that the extrasporogonic parasite undergoes autophagy with the development and release of the sporogonic stage. Aquatic oligochaetes from PKD enzootic rivers infected with Actinosporean species were studied using immunohistochemistry, electron microscopy and transmission experiments performed. However, the alternative host for the disease was not determined. Wild fish kidneys from PKD enzootic waters were tested with immunohistochemistry to determine the possible definitive host of PK’X’. An unidentified Sphaerospora sp. infecting Atlantic salmon reacted with all of the MAbs indicating a possible definitive host for the parasite.