AK-2011 strain for the development of a vaccine against equine rhinopneumonitis

Equine rhinopneumonitis is an acute, highly contagious disease found virtually worldwide. The purpose of the studies presented in this paper is to develop a technology for the manufacture of a cell-derived equine rhinopneumonitis vaccine, as well as to assess the safety and immunogenicity of the newly developed vaccine in laboratory animals model. The object of the studies was the AK-2011 strain isolated from the horses suffering from rhinopneumonitis during an outbreak of abortions. The viability of the AK-2011 strain was assessed using a continuous line of calf trachea cells, a continuous line of calf kidney cells, a continuous line of sheep kidney cells, a continuous line of bovine kidney cells, a continuous line of green monkey kidney cells, a continuous line of Syrian hamster kidney cells, a primary trypsinized culture of horse kidney cells grown in tubes and flasks and the AK-2011 laboratory strain of equine rhinopneumonitis virus with biological activity of 6.0 lg TCID50/cm3. Sequencing and polymerase chain reaction analysis were performed. The virus isolated from the ORF68 gene in Kazakhstan appeared to be the most similar to the T-953 and 2222-03 strains isolated in the USA and Australia, respectively, in terms of phylogenetics. As to primary infections, cytopathic effects (CPEs) induced by the AK-2011 virus stain (dilution 10(1)) in calf trachea and horse kidney cell cultures were stable from the first to tenth passages, with biological activity of 5.75-6.00 lg TCID50/cm3. CPEs caused by the virus were apparent on days 2-3, further developed intensively and extended to 60-80% of the cell monolayer on days 5-7. The vaccine results can be used to immunize horses on farms against rhinopneumonia, and horses should be immunized twice with an interval of 2-3 months.