Abstract
Background/ObjectivesVaccination is the most important tool for controlling brucellosis, but currently there is no vaccine available for canine brucellosis, which is a zoonotic disease of worldwide distribution caused by Brucella canis. This study aimed to evaluate protection and immune response induced by Brucella ovis ΔabcBA (BoΔabcBA) encapsulated with alginate against the challenge with Brucella canis in mice and to assess the safety of this strain for dogs.MethodsIntracellular growth of the vaccine strain BoΔabcBA was assessed in canine and ovine macrophages. Protection induced by BoΔabcBA against virulent Brucella canis was evaluated in the mouse model. Safety of the vaccine strain BoΔabcBA was assessed in experimentally inoculated dogs.ResultsWild type B. ovis and B. canis had similar internalization and intracellular multiplication profiles in both canine and ovine macrophages. The BoΔabcBA strain had an attenuated phenotype in both canine and ovine macrophages. Immunization of BALB/c mice with alginate-encapsulated BoΔabcBA (108 CFU) induced lymphocyte proliferation, production of IL-10 and IFN-γ, and protected against experimental challenge with B. canis. Dogs immunized with alginate-encapsulated BoΔabcBA (109 CFU) seroconverted, and had no hematologic, biochemical or clinical changes. Furthermore, BoΔabcBA was not detected by isolation or PCR performed using blood, semen, urine samples or vaginal swabs at any time point over the course of this study. BoΔabcBA was isolated from lymph nodes near to the site of inoculation in two dogs at 22 weeks post immunization.ConclusionEncapsulated BoΔabcBA protected mice against experimental B. canis infection, and it is safe for dogs. Therefore, B. ovis ΔabcBA has potential as a vaccine candidate for canine brucellosis prevention.
Highlights
Canine brucellosis is a zoonotic disease caused by Brucella canis [1]
Considering that B. ovis is not pathogenic for humans and dogs as well as the structural similarities between B. canis and B. ovis, which have a naturally rough LPS [27], this study aimed to evaluate the protective capacity of the B. ovis vaccine candidate strain (B. ovis ΔabcBA–with deletion of abcA and abcB genes from the B. ovis pathogenicity island 1 (BOPI-1)) against B. canis infection in mice and to evaluate the safety of this vaccine strain in dogs
To evaluate the potential for internalization and survival of BoΔabcBA, primary canine and ovine macrophages were infected with wild type (WT) B. canis, WT B. ovis, or BoΔabcBA (Fig 1)
Summary
Canine brucellosis is a zoonotic disease caused by Brucella canis [1]. Infection is associated with reproductive disease characterized by outbreaks of abortion, conception failure, or epididymitis and orchitis in males [2,3]. Human brucellosis due to B. canis is considered infrequent and less pathogenic when compared to other Brucella species [4], the close contact between dogs and humans makes the zoonotic risk posed by B. canis highly significant under a public health perspective [5]. In the Americas, Asia and Africa, canine brucellosis is considered endemic in dogs [6]. In certain countries such as the United Kingdom [7] and Sweden [8], B. canis infection in dogs is less frequent
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