CHARACTERIZATION OF KTY-06 FIELD PRRS STRAIN ISOLATED IN VIETNAM AND EVALUATION OF ANTIBODY PRODUCING OF THE INACTIVATED VIRUS IN PIG

Abstract

    KTY-06 virus strain was isolated from 2-week-old piglet in a PRRS outbreak in Northern Vietnam in 2015 that had clinical signs, gross findings, and microsopic lesions specific with HP-PRRS. Results of a phylogenetic analysis of the open reading frame 5 region of the KTY-06 strain showed it to be a North American genotype and classified into sublineage 8.7, in which highly pathogenic Chinese PRRSV strains are also clustered. Passaging in Marc-145 cells, KTY-06 gradually induced 35% up to 100% CPE between 36 to 60 hours post inoculation. The titer of KTY-06 was 1.74 X 10⁵ TClD₅₀/25μl. Of which, titer of the free viaises in the supernatant was higher than the titer of the cell associated virusese. Formalin-inactivated KTY-06 was able to stimulate pigs to produce specific antibodies against PRRSV. The immune response was detectable 14 day post immunization (dpi) (S/P ratio was 0.697 ± 0.271), peaked at 42 dpi (S/P ratio was 1.197 ±, p.256), and then declined at 49 dpi. The results suggest that KTY-06 was a candidate for strain selection for producing PRRS vaccine.