Determination of some biological characteristics and evaluation of immunogenicity of two parvovirus isolates in Vietnam

Abstract

In this study, two highly virulent strains (VC5 and TX7) among 32 parvovirus strains isolated from six provinces (Thai Binh, Thanh Hoa, Binh Dinh, Dak Lak, Binh Duong, and Dong Nai) (prior to the administrative merger) were selected to determine some biological characteristics and assess the immunogenicity. Sequence analysis of the NS1 gene fragment revealed that both VC5 and TX7 strains belong to the porcine parvovirus 1 (PPV1) type and share 99.70% nucleotide sequence identity with the PPV1 strain from China (PPV1-0225-L-SD). The optimal culture conditions for the two porcine parvovirus (PPV) strains on PK15 cells were EMEM medium supplemented with 5% FBS and 1% Penicillin-Streptomycin antibiotic (Pen/Strep), incubated at 37°C and 5% CO₂. 21 days after the second immunisation, the average HI titer of the immunised pigs was 7.33 and 7.66 log2 for the VC5 and TX7 immunised groups, respectively, while no antibodies were detected in the control group. Upon challenge with a highly virulent parvovirus strain, over 80% of the fetuses in the immunised groups survived, and less than 10% of the fetuses were detected with PPV. In contrast, in the control group, 100% of the fetuses died, with 75% showing signs of
mummification and 90% testing positive for PPV.