A new inactivated BVDV genotype I and II vaccine - An immunisation and challenge study with BVDV genotype I

An inactivated vaccine containing BVDV I and II strains (PT810; BVDV I, and 890; BVDV II) and using different adjuvants and antigen dosages was tested in a cattle challenge model. Groups of six healthy, seronegative cattle we re vaccinated twice with a low dose (10(6.6) TCID50 PT810 and 10(7.2) TCID5 0 890) vaccine with the adjuvant Bay R1005 or a high dose (10(7.8) TCID50 P T810 and 10(8.2) TCID50 890) vaccine with two different adjuvants (Bay R100 5 or Polygen). Thirty-eight days after the second vaccination, immunised an imals (n = 18) and non-vaccinated control animals (n = 3) were challenged i ntranasally with 10(6) TCID50 BVDV strain PT810. For a period of 16 days, v irus was isolated from blood leukocytes and nasal swabs, and neutralising a ntibody titres were determined. The induction of antibodies following immunisation was strongly dependent o n the antigen dosage in the vaccine. The high dose formulation induced high serum neutralising antibody titres against both genotypes of up to 32 000 after the second immunisation. Animals with neutralising antibody titres >5 12 (n = 14) did not show any marked leukopenia after challenge and only ver y little or no virus could be isolated from blood leukocytes and/or nasal s wabs when compared to control cattle. Furthermore, some of these animals di d not show any boost of neutralising or even NS3-specific antibodies, which renders viral replication unlikely and thus would prevent infection of the fetus. Both adjuvants (Bay R1005 or Polygen) were similarly efficient and induced nearly identical antibody responses. In contrast, four of the six l ow dosage vaccinates had a marked leukopenia and viraemia as well as detect able nasal virus shedding for several days. We conclude that the selected strains and the system of vaccine preparation with high BVDV antigen dosages and highly efficient new adjuvants provide an effective means of protection against BVDV I infections. Investigations to demonstrate the protection against BVDV II infections, the duration of i mmunity and the ability of fetal protection by using the high dose vaccine in a fetal challenge model will follow. (C) 2000 Elsevier Science B.V. All rights reserved.