Characterization of Cellular and Humoral Immunity to Commercial Cattle BVDV Vaccines in White-Tailed Deer

Abstract

Background/objectives: White-tailed deer (Odocoileus virginianus) (WTD) play a central role at the human-livestock-wildlife interface, given their contribution to the spread of diseases that can affect livestock. These include a variety of bacterial, viral, and prion diseases with significant economic impact. Given the implications for WTD as potential reservoirs for a variety of diseases, methods for prevention and disease control in WTD are an important consideration.

Methods: Using commercial livestock vaccines against bovine viral diarrhea virus (BVDV) in killed and modified live formulations, we test the ability of WTD to develop humoral and cellular immune responses following vaccination.

Results: We demonstrate that, similar to cattle, WTD develop humoral immune responses to both killed and modified live formulations.

Conclusions: As the farmed deer industry and the use of livestock vaccines in non-approved species grow, this type of information will help inform and develop improved husbandry and veterinary care practices. Additionally, while we were unable to detect cell-mediated immune responses to the vaccine, we established PrimeFlow as a method to detect IFN-γ responses in specific T cell populations, adding another level of resolution to our ability to understand WTD immune responses.

Keywords: BVDV; PrimeFlow; bovine viral diarrhea virus; immune responses; vaccines; white-tailed deer.

Figure 1

Serological responses to KV and MLV vaccines in serum of vaccinated white-tailed deer. Serum samples were collected at the indicated timepoints following vaccination and boost and assessed via virus neutralization assay. Neutralizing titers were determined for BVDV-1 (A) and BVDV-2 (B). Titers are expressed as the reciprocal (anti-log base 10) of the highest serum dilution able to inhibit CPE in the monolayer. * Indicates statistical significance (p ≤ 0.05).

Figure 2

Distribution of peripheral T cell subsets following vaccination of white-tailed deer with commercial vaccines. Peripheral blood mononuclear cells (PBMC) were isolated from whole blood samples and assessed via flow cytometry for the frequency of CD4, CD8, and γσ T cells using flow cytometry. Shown are representative dot plots (A) for forward scatter (FSC) vs. side scatter (SSC), singlet discrimination, CD4, CD8, and γδ gating. Overall frequency of T cell subsets control (open circle), KV-vaccinated deer (orange), and MLV-vaccinated deer (blue) (B). Values indicate mean frequency ± SEM.

Figure 3

Detection of intracellular IFN-γ mRNA in white-tailed deer T cells using PrimeFlow. Peripheral blood mononuclear cells were isolated from whole blood samples and were either left unstimulated or stimulated with PMA/Ionomycin to induce cytokine production. PrimeFlow and flow cytometry were utilized to assess IFN-γ mRNA expression from CD4, CD8, and γδ T cells. Shown are the representative dot plots (A) of total PBMCs with and without PMA/Ionomycin stimulation, demonstrating the presence of IFN-γ mRNA staining. The frequencies of IFN-γ mRNA-positive CD4 (B), CD8 (C), and γδ (D) T cells from PBMCs collected from control (open circles), KV-vaccinated deer (orange circles), and MLV-vaccinated deer (blue circles) and stimulated with PMA/Ionomycin are shown. Values indicate mean frequency ± SEM.

Figure 4

Assessment of BVDV-specific IFN-γ T cell responses from vaccinated white-tailed deer. Peripheral blood mononuclear cells were isolated from whole blood at 8 weeks post-vaccination and were left unstimulated or were stimulated with BVDV-1 or BVDV-2a in vitro. Using PrimeFlow and flow cytometry, the frequency and number of IFN-γ mRNA-expressing CD4 (A,B), CD8 (C,D), and γδ (E,F) T cells from control (open circles), KV-vaccinated (orange circles), and MLV-vaccinated (blue circles) were assessed. Values indicated mean frequency ± SEM.