Abstract
Abortion and reproductive failures induced by Brucella are the main symptoms of animal brucellosis. Laboratory animal models are essential tools of research to study the Brucella pathogenesis before experimentation in natural hosts. To extend the existing knowledge, we studied B. melitensis 16M (virulent) and Rev1 (attenuated) as well as B. suis bv2 infections in pregnant mice. Here, we report new information about kinetics of infection (in spleens, blood, placentas, vaginal shedding, and foetuses), serum cytokine profiles, and histopathological features in placentas and the litter throughout mice pregnancy. Both B. melitensis strains showed a marked placental tropism and reduced viability of pups (mainly in 16M infections), which was preceded by an intense Th1-immune response during placental development. In contrast, B. suis bv2 displayed lower placental tropism, mild proinflammatory immune response, and scarce bacterial transmission to the litter, thus allowing foetal viability. Overall, our studies revealed three different smooth Brucella patterns of placental and foetal pathogenesis in mice, providing a useful animal model for experimental brucellosis.
Highlights
Smooth Brucella Strains in Mice.Brucellosis is a widespread zoonosis caused by Gram-negative Brucella, facultative intracellular bacteria, which are classified in different species according to their preferred host
We evaluated the ability of B. melitensis 16M, Rev1, and B. suis bv2 to infect
B. melitensis virulent and attenuated strains displayed similar cytotoxicity between them and significantly higher (p ≤ 0.05) than that displayed by B. suis bv2 (Figure 1d)
Summary
Brucellosis is a widespread zoonosis caused by Gram-negative Brucella, facultative intracellular bacteria, which are classified in different species according to their preferred host. B. melitensis (small ruminants), B. abortus (cattle), and B. suis (swine) are the most pathogenic species according to their zoonotic potential and economic impact on livestock production [1]. Due to Brucella tropism for trophoblast cells in placenta, abortion and infertility are the most common symptoms in wildlife and domestic animals [2]. Placentitis, induced by replicative bacteria, leads to vaginal excretion and aborted foetuses, which contributes to pathogen transmission [3]. Recent reports have highlighted the importance of the metabolic pathways and nutritional conditions in the niche for Brucella infection [4,5]; the underlying mechanism of Brucella placental tropism remains unknown [6]
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