Protection of Cattle against Epizootic Bovine Abortion (EBA) Using a Live Pajaroellobacter abortibovis Vaccine - PubMed (original) (raw)

Protection of Cattle against Epizootic Bovine Abortion (EBA) Using a Live Pajaroellobacter abortibovis Vaccine

Myra T Blanchard et al. Vaccines (Basel). 2022.

Abstract

Epizootic bovine abortion (EBA) is an arthropod-borne bacterial disease that causes significant economic loss for cattle producers in the western United States. The etiologic agent, Pajaroellobacter abortibovis, is an intracellular pathogen that has yet to be cultivated in vitro, thereby requiring novel methodologies for vaccine development. A vaccine candidate, using live _P. abortibovis_-infected cells (_P.a_-LIC) harvested from mouse spleens, was tested in beef cattle. Over the course of two safety studies and four efficacy trials, safety risks were evaluated, and dosage and potencies refined. No incidence of anaphylaxis, recognized health issues or significant impact upon conception rates were noted. Vaccination did result in subclinical skin reactions. Early fetal losses were noted in two trials and were significant when the vaccine was administered within 21 days prior to conception. Administration of the EBA agent (EBAA) vaccine as a single dose, at a potency of 500 _P.a_-LIC, 56 days prior to breeding, provided 100% protection with no early fetal losses. Seroconversion occurred in all animals following EBAA vaccination and corresponded well with protection of the fetus from epizootic bovine abortion.

Keywords: EBAA vaccine; Pajaroellobacter abortibovis; early fetal losses; epizootic bovine abortion (EBA); foothill abortion; indirect fluorescent antibody test (IFAT); serology.

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Conflict of interest statement

All authors declare no potential conflict of interest with respect to the research, authorship, and/or publication of this article. The vaccine will not be produced for commercial distribution by either the University of California or University of Nevada, nor are there monetary incentives to the authors or their institutions in association with potential vaccine sales.

Figures

Figure 1

Figure 1

Histological sections of dermis (A-1,B-1,C-1), deep dermis (DD; A-1,B-1,C-1 and A-2,B-2) and underlying muscle (M; A-2,B-2,C-2) from samples collected in Safety Study #1 from either control (A) or EBAA vaccine injection sites (B,C) at 21 days post-inoculation (H&E, 2×). Intervals between last palpable lesions and sample collection were (B) 14 days and (C) 1 day. Inserts (B-1,C-1) focus on perivascular mononuclear inflammatory cell infiltrates within the DD, consisting primarily of lymphocytes and plasma cells (40×).

Figure 2

Figure 2

Areas (L × W) of palpable injection site reactions over time (days post-vaccination; DPV) in individual cattle from Safety Study #2 following inoculation with one of two EBAA vaccine serials. Potencies of serials were (A) 8700 or (B) 6000 _P.a._-LIC with group sizes of five animals each.

Figure 3

Figure 3

Temporal appearance of injection site reactions (Rx) following inoculation of EBAA vaccine. Vaccine potency varied and is provided at the top of each graph. Data from Graph (A) was derived from Safety Study #2 while data from Graphs (B,C) were derived from Efficacy Trial #4. First-time reactions in individual animals are depicted in blue and persisting reactions depicted in gray.

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