Canadian regulatory requirements for recombinant fish vaccines.

In Canada, veterinary biological products derived by using conventional and new techniques of biotechnology are licensed and regulated under the Health of Animals Act and Regulations. Biological products include vaccines, bacterins, bacterin-toxoids and diagnostic kits which are used for the prevention, treatment or diagnosis of infectious diseases in all species of animals, including fish. Veterinary biologicals are licensed on the basis of fulfillment of four criteria: purity, potency, safety and efficacy. A risk-based approach is used to evaluate the safety of the product in target species, as well as non-target species, humans and the environment. On the basis of biological characteristics, biotechnology derived veterinary biologicals have been divided into two broad categories, high and low risk products. The paper describes the regulatory framework for the licensing of veterinary biologicals in Canada, with emphasis on the regulatory considerations for recombinant fish vaccines. Stages of movement of the product from research in a contained laboratory facility to a fully licensed product for free sale are discussed. The requirements for field testing and environmental assessment involved in these stages are highlighted. Manufacturers and researchers who intend to commercialize experimental vaccines are encouraged to consult with the Veterinary Biologics and Biotechnology Section early in the product development process so that the research data and quality assurance documentation are consistent with regulatory requirements.

Epitope specificity of the protective immune response induced by individual bovine herpesvirus-1 glycoproteins.

Affinity-purified bovine herpesvirus-1 (BHV-1) glycoproteins gI, gIII and gIV, as well as a virus-free BHV-1-infected cell lysate were injected intramuscularly into seronegative calves. All immunized animals developed specific serum-neutralizing antibodies and they were fully protected from disease, using a BHV-1/Pasteurella haemolytica challenge model. After challenge, viral replication in the nasal passages was significantly reduced in animals vaccinated with gIV (10,000-fold) or BHV-1-infected cell lysate (450,000-fold) but just slightly reduced in animals immunized with gI (500-fold) or gIII (25-fold). All of the known epitopes of the glycoproteins were retained during the affinity-purification or preparation of the cell lysate. The high level of protection induced by gIV and the virus-infected cell lysate in particular indicates the potential of glycoprotein gIV as a subunit vaccine, ideally in combination with component(s) from the cell lysate, which may mediate cellular immune responses.

Monoclonal antibodies to bovine coronavirus glycoproteins E2 and E3: demonstration of in vivo virus-neutralizing activity.

Six monoclonal antibodies (MAbs) to bovine coronavirus (BCV, Quebec isolate) E2 and E3 glycoproteins which were found previously to be neutralizing in vitro were examined for virus-neutralizing activity in vivo. Surgically ligated intestinal loops of newborn colostrum-deprived calves were virus-inoculated, mock-infected or inoculated with a mixture of virus and antibody. Of the six BCV-specific MAbs, four were found to be protective against a virulent field isolate of BCV, as indicated by a reduction in villous atrophy. These MAbs were specific to antigenic domain A and antigenic domains A1 and A2 on the E2 and E3 glycoproteins respectively. MAbs to antigenic domains B and C on the E2 and E3 glycoproteins, respectively, were not protective.

Clinical and pathological evaluation of sulbactam/ampicillin for treatment of experimental bovine pneumonic pasteurellosis.

An experiment was conducted to evaluate the efficacy of sulbactam/ampicillin for treatment of bovine pneumonic pasteurellosis. Twenty-one Hereford calves were experimentally infected with bovine herpesvirus-1 and an ampicillin-resistant strain of Pasteurella haemolytica, then treated for three days with either sulbactam/ampicillin, chloramphenicol, or a placebo. The treatments were evaluated by comparing clinical illness scores, total sick days, weight changes, mortality rates, and postmortem lung scores between treatment groups. Both antibiotics were highly effective in reducing respiratory disease in the experimentally infected calves. The clinical response to sulbactam/ampicillin treatment was comparable with that of chloramphenicol and was significantly improved compared with the response to the placebo treatment. These findings suggest that the efficacy of sulbactam/ampicillin may be comparable to that of chloramphenicol for treatment of pneumonic pasteurellosis involving ampicillin-resistant strains of P. haemolytica.

Protection of cattle from bovine herpesvirus type I (BHV-1) infection by immunization with individual viral glycoproteins.

The major glycoproteins gI, gIII, and gIV of bovine herpesvirus-1 (BHV-1) were found to induce high levels of antibody in cattle which could neutralize virus and participate in antibody-dependent cell cytotoxicity of BHV-1-infected cells. Immunized animals were fully protected from disease, using a BHV-1/Pasteurella haemolytica aerosol challenge model but not from infection with the virus. Thus, virus could still replicate in the nasal passages of immunized animals, although to a lesser extent than in placebo-treated animals or animals immunized with a commercial killed whole virus vaccine. Systemic spread of the virus in immunized animals did not appear to occur since there was not a dramatic alteration of leukocyte function following challenge. These results suggest that any one of the three major BHV-1 glycoproteins may be useful as a subunit vaccine either individually or in combination.

Use of recombinant bovine alpha 1 interferon in reducing respiratory disease induced by bovine herpesvirus type 1.

Intranasal or intramuscular treatment of calves with recombinant bovine alpha 1 interferon before challenge with bovine herpesvirus type 1 and Pasteurella haemolytica reduced clinical signs, number of sick days, lung lesions, and weight loss. The effective dose was determined to be relatively broad within the range of 1 to 50 mg per animal. No adverse effects were observed even at high doses of interferon (50 mg per animal). Administration before virus infection was more effective than administration at the same time as virus infection. Although interferon administration had dramatic effects on the survival of animals, it did not have much effect on virus secretion in the upper respiratory tract. Therefore, the mechanism by which interferon reduces the susceptibility of animals to viral-bacterial synergy was postulated to be via its immunomodulatory effects.