Efficacy of phase I and phase II Coxiella burnetii bacterin vaccines in a pregnant ewe challenge model

Publisher
MDPI (Multidisciplinary Digital Publishing Institute)
Abstract
The bacterium Coxiella burnetii (C. burnetti) can cause the disease Q-fever in a wide array of animal hosts. Ruminants, including sheep, are thought to play a pivotal role in the transmission of C. burnetti to humans; however, the only existing livestock vaccine Coxevac (CEVA), a killed bacterin vaccine based on phase I C. burnetti strain Nine-Mile, is only approved for use in goats and cattle. In this study a pregnant ewe challenge model was used to determine the protective effects of Coxevac and an experimental bacterin vaccine based on phase II C. burnetti against C. burnetti challenge. Prior to mating, ewes (n=20 per group) were vaccinated subcutaneously with either Coxevac, or the phase II vaccine, or were left unvaccinated. A subset of pregnant ewes (n=6, all carrying twins or triplets) from each group was then challenged 151 days later (~100 days of gestation) with 106 infectious mouse doses of C. burnetti, Nine-Mile strain RSA493. Both vaccines used in this study provided protection against C. burnetti challenge as measured by reductions in bacterial shedding in faeces, milk and vaginal mucus, and by production of healthy offspring, compared to unvaccinated controls. This work highlights that the phase I vaccine Coxevac can protect ewes against the detrimental effects of C. burnetti infection. Furthermore, the phase II vaccine formulation used in this study provided comparable levels of protection against bacterial challenge and may offer a safer and cost-effective alternative to the currently licensed C. burnetti vaccine.
Year
2023
Category
Refereed journal
Output Tags
BB/R019975/1