Immunogenicity of an inactivated Chinese bovine viral diarrhea virus 1a (BVDV 1a) vaccine cross protects from BVDV 1b infection in young calves.

Bovine viral diarrhea virus (BVDV) 1a and 1b strains are the predominant subgenotypes in China. Because of the genetic and antigenic variability among different BVDV strains, a vaccine effective in one region may fail to protect against infections caused by different virus strains in another region. No BVDV vaccine developed with the predominant strains in China are available. In this study, the immunogenicity of an inactivated Chinese BVDV 1a NM01 vaccine strain was evaluated by challenging with a Chinese BVDV 1b JL strain. Ten 2-4-month-old calves were intramuscularly vaccinated with a single dose of the vaccine strain and boosted with same dose three weeks after the first vaccination, with five mock immunized calves serving as a control group. The average titer of neutralization antibody to BVDV 1a and BVDV 1b of immunized calves reached 1:410 and 1:96, respectively, at 21 days post the second vaccination. Twenty-one days post the second vaccination, all calves were challenged with strain JL. The clinical signs, such as the temperature and leukopenia of the immunized calves and viral shedding, were significantly less than the mock immunized calves after challenging with the virulent BVDV 1b strain, indicating that the BVDV 1a vaccine strain elicited efficacious protection against the endemic BVDV 1b strain in China. To the best of our knowledge, this is the first report of an inactivated BVDV vaccine which demonstrated effective cross-protection against BVDV type 1b infection in China.