Search

Canarypox virus recombinant vaccines have a unique efficacy and safety profile for the vaccinated host because the canarypox virus is non-replicative in mammalian hosts. After the vaccination of a mammalian species, recombinant canarypox viruses express the inserted genes but cannot multiply in the host. They stimulate a strong immune response in the absence of any virus amplification in the host or any viral spread into the environment. A new canarypox-based recombinant vaccine is the canarypox-feline leukaemia virus (FeLV) vaccine (EURIFEL FeLV; Merial) that expresses the FeLV env and gag protective genes. This paper describes experiments which demonstrate that it is effective against any oronasal FeLV challenge. The protection was shown to be solid against an oronasal challenge one year after the initial vaccination, and was effective against a very severe 'in-contact' challenge. Furthermore, the canarypox virus-FeLV vaccine was effective without an adjuvant.

Six bitches free of canine herpesvirus 1 (CHV-1) were vaccinated against the virus; a first injection was given 10 days after the presumed date of mating and a second six weeks later. Six similar bitches were left unvaccinated as controls, and all the pups were challenged oronasally with a virulent strain of CHV-1 at three days of age. All the vaccinated bitches seroconverted and had high antibody titres when the puppies were challenged, but the control bitches remained seronegative. In the control group, 62 per cent (18 of 29) of the pups died of CHV-1-induced disease; most of them showed typical clinical signs and macroscopic lesions, and CHV-1 infection was confirmed by the isolation of the virus or by PCR. None of the puppies in the vaccinated group died of CHV-1 infection. The efficacy of the vaccine was confirmed in CHV-1-positive breeding units. The rate of pregnancy tended to be higher in vaccinated bitches and the mortality of pups before weaning was significantly reduced in the litters born to vaccinated bitches.

A new, simple, rapid and accurate culture technique is described for a semi-quantitative analysis of cellular viremia in FIV-infected cats. This assay can be carried out with small amounts of whole blood, and is based on the detection of FIV core gag antigen, which is released in culture supernatants. The amount of core antigen produced is measured with an enzyme-linked immunoassay using specific monoclonal antibodies. This whole blood technique (WB method) was compared with a culture method using isolated peripheral blood mononuclear cells (PBMC method). FIV could be detected in whole blood of all experimentally infected cats, but not from uninfected cats. This assay offers a number of advantages (small blood samples required, no leukocyte separation and lymphocyte purification procedures) and its reproducibility is very good. It provides a convenient in vitro cellular assay for viral semi-quantitation, well adapted for monitoring efficacy of prototype FIV vaccines or experimental antiviral drugs. Also, it could facilitate the study of the pathogenesis of FIV-related progressive immunodepression. Finally, it offers an alternative to serological techniques for diagnostic purposes in several circumstances: early viremia, maternal antibodies.

Two recombinant herpesviruses of turkey (HVT) expressing the VP2 protein of infectious bursal disease virus (IBDV or Gumboro disease virus) have been constructed: vHVT001 and vHVT002. The VP2 open reading frame was inserted at the locus of the small subunit of ribonucleotide reductase gene (HSV-1 UL40 homolog) without any exogenous promoter in vHVT001 and at the locus of gl gene (HSV-1 US7 homolog) under the control of the human cytomegalovirus immediate-early promoter in vHVT002. The isolation of these recombinant viruses indicated that the deleted genes were not required for replication of HVT in chicken embryo fibroblasts. Efficacy of these recombinant viruses against IBDV strain 52/70 and Marek's disease virus (MDV strain RB1B) virulent challenges was evaluated in chickens vaccinated at 1 day of age. In the IBDV challenge, a good protection against mortality and bursal gross lesion was observed in vHVT002-vaccinated chickens: 100% with 10(5) PFU dose and 60% with 10(4) PFU dose; in contrast, only a weak level of protection was achieved after vaccination with vHVT001. Protection levels against MDV challenge obtained with vHVT001 and vHVT002 were low (around 10%) compared to that induced by the parental HVT (84%). In spite of the low protection level against MDV, this is the first report which describes induction of full protection against IBDV with a single inoculation of a recombinant virus.