The aims of the project are :

Production of monoclonal and polyclonal antibodies against the causative ageing of proliferative kidney disease (PKD);
Elucidation of aspects of life-cycle and epidemiology of the causative agent;
Initial assessment of isolated antigens for their immunogenic and protective properties for use in later vaccine development.
Proliferative kidney disease (PKD) is a seasonal condition affecting salmonids. The development of a PKD vaccine requires in depth knowledge of the PK'X' parasite causing the disease, in terms of its life cycle and surface antigens. Specific antibody probes to PK'X' are being developed so that these aspects of the parasite can be elucidated.

Field samples were collected and PK'X' cells partially purified from host kidney cells. These were then utilized in transmission studies to extend the seasonal availability of PK'X' and to provide an antigen source to immunize mice and rabbits for the production of antibodies.

Polyclonal and monoclonal antibody probes were produced against PK'X' and were used as the basis for rapid diagnostic tests for PKD. PK'X' infected tissues from European and North American salmonids were treated with Mab 12. Parasites from all the species reacted with the monoclonal antibody probe indicating that PK'X' found in different host species and from different continents share similar antigenic structures. Similar studies were also performed using lectin probes GS-1.

The binding site(s) for monoclonal antibody on PKX is currently unknown. Preliminary studies using periodate oxidation and lectin inhibition methods suggest that Mab 12 binds to a carbohydrate moiety which may resemble, in part, the binding site for the lectin GS-1.

Life cycle studies have confirmed that infectivity is associated with sediments. Filtration of sediments indicated that infectivity was present in only 2 fractions, 1 larger than 500 m in size and the other smaller than 50 m. It is likely that the larger fraction represents an intermediate host and that the smaller (20 to 25 m) is the infective stage of the parasite released by the intermediate host. Transmission studies using oligochaete worms found in the sediments have so far been unsuccessful.

Finally, a sampling programme has been performed to assess the possible role of native fish in the epizootiology of PKD.
The programme will be carried out in 4 phases:

Isolation and purification of PKD causative agent;
Production of monoclonal and polyclonal antibodies;
Assessment of isolated antigens;
Life-cycle investigations.

The aims will be pursued by purifying antigens of the causative agent. Various methods for isolation and culture will be evaluated. Specific poly and monoclonal antibodies will be produced and immuno-assays for identifying the causative organism developed. Isolated antigens will undergo primary assessment for their immunogenic and protective properties. Investigation of aspects of the life cycle of the causative agent will be investigated once specific labelling of the parasite has been achieved.