Isolation and Characterization of a Variant Psedorabies Virus HNXY and Construction of rHNXY-∆/∆.

The outbreak of pseudorabies in China, caused by more virulent pseudorabies virus (PRV) than the classical strains, has led to considerable economic losses. In this study, PRV strain HNXY was isolated from the Henan province of China in 2015 from the pig farm with severe reproductive failure in sows and a high mortality in piglets. The 50% tissue culture infectious doses (TCID) of HNXY in Vero cells were examined to be 10/mL, and the neutralisation titer against Bartha-K61 was significantly higher than against HNXY when tested with the serum from Bartha-K61 vaccinated pigs. The 50% lethal doses (LD) of HNXY to six-week-old BALB/c mice and two-month-old PRV-free pigs were both 10 TCID. HNXY was classified as genotype II, and numerous amino acid variations were found in gB, gE, gC, gD, TK, and RR1 proteins, compared with PRV from other countries or those prevalent in China before 2012. The attenuated rHNXY-∆TK/∆gE was further constructed, which presented significantly smaller plaques than HNXY, as well as the similar growth kinetics. rHNXY-∆/∆ was confirmed to be non-pathogenic to six-week-old BALB/c mice and zero-day-old piglets. This study isolated updated PRV promising to develop into a new vaccine candidate.