Recombinant E2 protein enhances protective efficacy of inactivated bovine viral diarrhea virus 2 vaccine in a goat model

Abstract

Background: Inactivated and subunit bovine viral diarrhea virus (BVDV) vaccines have shown limited protective efficacy. This study aimed to evaluate the effectiveness of a vaccine containing both inactivated BVDV (iBVDV) and baculovirus-expressed recombinant E2 (rE2), an important BVDV antigen with strongly neutralizing epitopes.

Results: Four groups of goats were immunized twice with one of four vaccine preparations: 1) iBVDV+rE2, 2) rE2, 3) iBVDV, and 4) saline, and challenged with BVDV. For goats vaccinated with the iBVDV+rE2 vaccine, no viremia was observed after challenge, and clinical signs, pyrexia, and leukopenia were reduced compared to the saline group. In contrast, for goats vaccinated with either iBVDV or rE2 alone, viremia was still detectable.

Conclusion: The combination of iBVDV and rE2 elicited stronger protective immune responses against BVDV than iBVDV or rE2 alone.

Keywords: BVDV; E2; Inactivated vaccine; Subunit vaccine.

Fig. 1

Cloning and expression of the BVDV E2 gene. The E2 gene of BVDV/TW2008 was cloned for expression in a baculovirus expression system and the sequence was compared to that of other BVDV-2 strains (a). Expression and quantitation recombinant E2 (rE2) was done using SDS-PAGE analysis (b). Antigenicity was verified using bovine convalescent anti-serum (c)

Fig. 2

Antibody response in goats immunized with BVDV vaccines. Goats were immunized twice intramuscularly with four different vaccine formulations: 1) iBVDV+rE2, 2) rE2, 3) iBVDV, and 4) saline. Total anti-BVDV IgG levels were analyzed by ELISA. Data represent means ± SD. Differences between groups were analyzed by Duncan’s significance test (Different letters indicate significant difference at p < 0.05)

Fig. 3

T-cell proliferation assay of PBMC from goats immunized with BVDV vaccines. Goats were immunized twice intramuscularly with four different vaccine formulations: 1) iBVDV+rE2, 2) rE2, 3) iBVDV, and 4) saline. PBMC from blood were isolated and stimulated with inactivated BVDV or Con A (as a positive control). Proliferation extent was measured and stimulation index (SI) calculated. Data represent means ± SD. Differences between groups were analyzed by Duncan’s significance test and different letters indicate significant difference at p < 0.05

Fig. 4

Leukopenia of immunized goats following BVDV challenge. Goats were immunized twice intramuscularly with four different vaccine formulations: 1) iBVDV+rE2, 2) rE2, 3) iBVDV, and 4) saline, and challenged with 1 × 10⁸ FAID₅₀ BVDV/TW 2014 4 weeks after primary immunization. Number of white blood cells in blood was counted. Means are presented

Fig. 5

Pyrexia of immunized goats following BVDV challenge. Goats were immunized twice intramuscularly with four different vaccine formulations: 1) iBVDV+rE2, 2) rE2, 3) iBVDV, and 4) saline, and challenged with 1 × 10⁸ FAID₅₀ BVDV/TW 2014 4 weeks after primary immunization. Rectal temperatures after challenge were recorded. Means are presented

Fig. 6

Mean daily clinical scores of immunized goats following BVDV challenge. Goats were immunized twice intramuscularly with four different vaccine formulations: 1) iBVDV+rE2, 2) rE2, 3) iBVDV, and 4) saline, and challenged with 1 × 10⁸ FAID₅₀ BVDV/TW 2014 4 weeks after primary immunization. Clinical signs were recorded and mean daily clinical scores calculated