Evaluation of the DNA vaccine against classical swine fever with a special consideration of the phenotypic analysis of blood leukocytes

The aim of the study was the evaluation of DNA vaccine against CSF and the estimation of its safety, protection value and immunogenicity. Piglets were vaccinated with the gene encoding the gp55 glycoprotein of CSFV with signal sequence and without the transmembrane region. For comparison the whole gene of gp55 glycoprotein and the DNA of plasmid vector only were used. For the challenge virulent Washington strain of CSFV was used. Clinical observations, body temperature and the immune response (haematological and FAGS analyses, presence of virus-specific antibodies) were monitored. The presence of the virus antigen in blood, nasal swabs and organs of dead animals was checked by virus isolation, antigen ELISA and PCR methods. Only pigs vaccinated with the first construct were protected from the challenge, however, two-day fever > 40 degreesC was registered. In other groups typical clinical and pathological symptoms accompanied by significant leukopenia were evidenced.