Sea Lice Vaccines for Salmonid Aquaculture

Final Report

Pfizer Canada Inc

AIMAP 2011-P01

Executive Summary:

Sea lice infestations present a significant challenge to aquaculturists, veterinary clinicians and vaccine developers. Sea lice feed on blood, skin and mucus and can cause severe damage to their hosts that result in reduced product value and in severe cases death. This leads to significant downgrade of products which can be extremely costly to the farmer. These parasites have been estimated to cost the salmon aquaculture industry as much as US $480 million world-wide based on the FAO Fisheries and Aquaculture Information and Statistics Service. It is believed that this estimate represents 6% to 10% of the value of production for the countries affected. Recent controversial data has also suggested that sea lice might have played a significant role in the collapse of wild salmonid populations in both Europe and Canada; if true the economic costs would be greater than initially predicted. Currently chemical treatments are primarily used to control infestations, however this also presents several disadvantages including toxicities, drug tolerance, environmental impacts, negative consumer perception, availability, and not the least of which is cost. Vaccination presents an alternative to chemical use that addresses many of these disadvantages.

Recent R&D at Pfizer Animal Health, Pfizer Canada Inc (Pfizer) has identified an excellent set of vaccine candidates. The goal of this project is to complete the remaining development, pre-commercial manufacturing, and regulatory work required to license a vaccine for the control of sea lice infestations of farmed salmon in Canada.

Over the past year, the candidate vaccine antigens were tested at the renowned international aquaculture center Fundacion de Chile, which is a well established center regularly used by numerous companies to run trials, in particular sea lice. However, the trial results did not show any significant reduction in the vaccinated groups. Although these results were negative, it does not mean that the antigens are not protective. The original antigens were taken mostly from Lepeophtheirus salmonis but tested against Caligus rogercresseyi. Although homology is significant between the two species, there still exists a level of variability. Therefore, in order to fully understand if the candidates are protective it is important to test them against the same species (L. salmonis), which they were taken from. It is important to note that Fundacion de Chile was selected as our initial trial site since no other facility in Canada was available to test our candidates.

An agreement with St. Andrews Biological Station, NB has been established, to run the same trial using L. salmonis (the main species found in Canadian waters) as the target species. The St. Andrews Biological Station has vast experience in sea lice husbandry and sea lice challenge models, which makes it an excellent location to test our vaccine candidates.

Pfizer understands how important a sea lice vaccine is to Canada and to the international aquaculture community. As a result, we are fully committed to this project and are determined to ensure that it is completed according to the proposed objectives. 

Introduction:

The success of aquaculture is largely dependent on the control of fish pathogens, which includes a diverse spectrum of viruses, bacteria, fungi and parasites. Successful management strategies generally require a variety of approaches for disease control one of the most important being the deployment of efficacious and cost-effective vaccines. Vaccines range in complexity from inactivated cells to highly complex biotechnology-derived products. The most difficult pathogens such as parasites require complex vaccine designs for which few vaccine models have been developed. Currently there are commercially available fin-fish vaccines for some bacterial and viral diseases but none for parasites. Historically, Pfizer has excelled at the development of cost-effective subunit vaccines for aquaculture.

Pfizer R&D has identified and tested several targets that we strongly believe would form the basis of a novel vaccine against the most prevalent salmon louse, L.salmonis. This basic research work has taken place over the course of several years working collaboratively with our research partners and with considerable financial investment. We were able to successfully demonstrated initial proof of concept at the NRC IMB in Halifax and at Marine Harvest's test facilities in Scotland. The logical next steps in the development of a commercial vaccine would be to systematize the proof of concept, manufacture commercial scale pre-license serials and field test a commercial product.

Methods:

1. Validate proof of concept
   
   Confirmation trials of preliminary results following vaccination with candidate target antigens. Throughout the trial, a number of fish will be removed, anaesthetised, and the number of sea lice attached and its stage will be determined. Experiment will be completed in triplicate tanks.
   
   Validation of proof of concept was initially tested at the Contract research Organization Fundacion Chile located in Puerto Mont, Chile. This renowned international aquaculture center is well recognized in the aquaculture community, and is regularly used by international companies to test numerous vaccines including sea lice.
   
   
2. Completion of dosage optimization studies
   
   A second trial will be completed for the purpose of establishing the final dose required for protection. In this study, the candidate vaccine will tested in three different doses. Throughout the trial, a number of fish will be removed, anaesthetised, and the number of sea lice attached and its stage will be determined. Experiment will be completed in triplicate tanks.
   
   
3. Completion of a secondary trial for the validation of proof of concept using L. salmonis
   
   We intend on completing a secondary trial to confirm and to ensure that the antigens tested above protect against L. salmonis which is the primary species in Canadian waters. The trial will take place at St. Andrews Biological Station in New Brunswick beginning in the winter of 2011.
   
   
4. Continuation of the Development of an in-vitro potency release test
   
   Once the proof-of-concept has been validated using in vivo testing methods, an in vitro test method will be developed and worked on throughout the first year (completion in December 2012) in order to carry out vaccine potency testing on the final product without the use of research animals. The in vitro test will be established.
   
   
5. Prepare Regulatory Documentation (Master Seed Report/Dossier)
   
   The Master Seed of the vaccine strain will be developed and QC tested at either Pfizer Animal Health, Pfizer Canada Inc. or at one of the two CRO being used (Fundacion Chile and St. Andrews Biological Station). The dossier on the sea lice vaccine product will be compiled and submitted to CFIA for approval. Once approved as a product, the Master Seed will be submitted to CFIA's Biologic Evaluation Laboratory for validation of results and final approval of seed.
   
   
6. Submit data for approval for Outline of Production (CFIA)
   
   The outline of production, which details the method for large-scale production of the vaccine product, will be developed in collaboration with the contract manufacturers. Once large-scale production has been optimized and the outline of production developed it will be submitted to CFIA for approval.

Results:

1. Validate proof of concept.
   
   Over the past year, the candidate vaccine antigens were tested at the renowned international aquaculture center Fundacion de Chile, which is a well established center regularly used by numerous companies to run trials, in particular sea lice. However, the trial results did not show significant reduction in the vaccinated groups. Although these results were negative, it does not mean that the antigens are not protective. The original antigens were taken mostly from L. salmonis but tested against C.rogercresseyi. Although homology is significant between the two species, there still exists a level of variability. Therefore, in order to fully understand if the candidates are protective it is important to test them against the same species (L. salmonis), which they were taken from.
   
   The decision to seek out an international aquaculture center and initially test in C. rogercresseyi was the lack of facilities with a fully established model that could accommodate us in such short notice.
   
   
2. Completion of dosage optimization studies.
   
   The proposed dosing study was not able to proceed since the results from objective 1 were not significant. In order to proceed with this objective we will need to confirm proof of concept in objective 3.
   
   
3. Completion of a secondary trial for the validation of proof of concept using L. salmonis
   
   An agreement with St. Andrews Biological Station has been established, to run the same trial in objective 1 using L. salmonis (the main species found in Canadian waters) as the target species. The trial has begun and will be completed by early March 2012. The St. Andrews biological station has vast experience in sea lice husbandry and sea lice challenge models, which makes it an excellent location to test our vaccine candidates.
   
   
4. Continuation of the Development of an in-vitro potency release test. Prepare Regulatory Documentation (Master Seed Report/Dossier).
   
   Due to the results in objective 1, this objective was not able to proceed.
   
   
5. Prepare Regulatory Documentation (Master Seed Report/Dossier).
   
   Due to the results in objective 1, this objective was not able to proceed.
   
   
6. Submit data for approval for Outline of Production (CFIA).
   
   Due to the results in objective 1, this objective was not able to proceed.

Conclusion:

Since we were not able to establish confirmation of proof-of-concept through our trial at the renowned Fundacion Chile aquaculture center, we had to delay the completion of objectives 2, 4-6. These objectives will now depend on a second trial (Objective 3), which is currently underway at St. Andrews Biological Station. Once proof-of-concept is confirmed, we will then proceed with the remaining objectives.

The decision to seek out an international aquaculture center and initially test in C. rogercresseyi, instead of completing these studies in a Canada, was the lack of facilities with a fully established model that could accommodate us in such short notice, after it was decided not to pursue our own model.