A recombinant bovine herpesvirus-4 vectored vaccine delivered via intranasal nebulization elicits viral neutralizing antibody titers in cattle

Abstract

Recombinant herpesvirus vaccine vectors offer distinct advantages in next-generation vaccine development, primarily due to the ability to establish persistent infections to provide sustainable antigen responses in the host. Recombinant bovine herpesvirus-4 (BoHV-4) has been previously shown to elicit protective immunity in model laboratory animal species against a variety of pathogens. For the first time, we describe the induction of antigen-specific immune responses to two delivered antigens in the host species after intranasal nebulization of recombinant BoHV-4 expressing the chimeric peptide containing the bovine viral diarrhea virus (BVDV) glycoprotein E2 and the bovine herpesvirus 1 (BoHV-1) glycoprotein D (BoHV-4-A-CMV-IgK-gE2gD-TM). In this study, four cattle were immunized via intranasal nebulization with the recombinant BoHV-4 construct. Two of the cattle were previously infected with wild-type BoHV-4, and both developed detectable serologic responses to BVDV and BoHV-1. All four immunized cattle developed detectable viral neutralizing antibody responses to BVDV, and one steer developed a transient viral neutralizing response to BoHV-1. Approximately one year after immunization, immunosuppressive doses of the glucocorticoid dexamethasone were administered intravenously to all four cattle. Within two weeks of immunosuppression, all animals developed viral neutralizing antibody responses to BoHV-1, and all animals maintained BVDV viral neutralizing capacity. Overall, nebulization of BoHV-4-A-CMV-IgK-gE2gD-TM persistently infects cattle, is capable of eliciting antigen-specific immunity following immunization, including in the presence of pre-existing BoHV-4 immunity, and recrudescence of the virus boosts the immune response to BoHV-4-vectored antigens. These results indicate that BoHV-4 is a viable and attractive vaccine delivery platform for use in cattle.

Fig 1. Antibody responses to antigens in each steer.

Data trends were fit by Loess (degree = 2, smoothing = 0.3), and original data are shown as symbols. The solid gray lines indicate positive cut-off values as suggested by the kit manufacturer for each respective ELISA kit, and the dotted grey line indicates the positive cut-off value as calculated for the geographical region. Steers 1 (blue) and 2 (red) (top) were WT-BoHV-4- infected (wt +) and steers 3 (green) and 4 (brown) (bottom) were immunized only with BoHV-4-A-CMV-IgK-gE2gD-TM (wt -). WT-BoHV-4 infection is indicated in the first 24 weeks, immunization with BoHV-4-A-CMV-IgK-gE2gD-TM occurred at week 24, and dexamethasone-induced suppression took place during week 77. Panel A. BoHV-4 antibody percent positivity as determined by indirect ELISA. Panel B. BVDV antibody response as determined by VN. Panel C. BoHV-1 antibody response as determined by indirect ELISA. Panel D. BoHV-1 antibody response as determined by VN.