Ovine brucellosis caused by Brucella ovis is a major cause of reproductive failure in sheep. This study aimed to evaluate transplacental infection and pathogenicity of B. ovis wild type strain ATCC 25,840 (WT B. ovis) and the candidate vaccine strain B. ovis Delta abcBA in pregnant mice. A total of 40 BALB/c mice were equally divided into 4 groups: (i) non immunized and uninfected control mice (3/10 mice became pregnant); (ii) non immunized and challenged with WT B. ovis (5/10 pregnant); (iii) inoculated only with B. ovis DabcBA (6/10 pregnant); (iv) immunized with B. ovis Delta abcBA and challenged with WT B. ovis (5/10 pregnant). Female mice bred, and five days after visualization of the vaginal plug, they were inoculated intraperitoneally (ip) with 100 mu L of sterile PBS, 100 mu L of 1 x 10(6) CFU of B. ovis Delta abcBA, or 100 mu L of 1 x 10(6) CFU of B. ovis WT, according to each group. At the 17th day of gestation, samples of spleen, liver, uterus, placenta, fetus and mammary gland were obtained for bacteriology, histopathology and immunohistochemistry. Non immunized mice challenged with B. ovis WT developed necrotizing placentitis as well as microgranulomas in the liver and spleen. These findings support the notion that B. ovis infection in pregnant mice induces lesions that are similar to those caused by B. abortus in the same animal model. B. ovis Delta abcBA was not recovered from any of the sampled organs, and it did not cause any gross or microscopic lesions, indicating that it is a safe and attenuated strain in this experimental model. In addition, B. ovis Delta abcBA was induced protective immunity as demonstrated by decreased numbers of B. ovis WT in the liver, uterus and fetuses of immunized mice after the challenge with B. ovis WT. (C) 2022 Elsevier Ltd. All rights reserved.
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