A Brucella melitensis H38ΔwbkF rough mutant protects against Brucella ovis in rams

Rev1Δwzm vaccine candidate is safe in young and adult sheep and protects against Brucella ovis infection in rams

Small ruminants affected by brucellosis, caused mainly by Brucella melitensis and B. ovis, suffer reproductive disorders, leading to significant economic losses worldwide. Vaccination is an essential tool to prevent the disease in ovine and caprine livestock, but the only vaccine recommended to date is B. melitensis Rev1, which in sheep is only safe for use in lambs aged 3-4 months. This restriction poses considerable practical challenges for the implementation of Rev1 in countries with endemic brucellosis and/or limited resources, where there is a need for mass vaccination with a safe vaccine to control the disease in both animals and humans. We recently developed a B. melitensis strain Rev1Δwzm showing superior vaccine properties in mice and safety in pregnant ewes. Here, we report that Rev1Δwzm (i) is safe in young and adult sheep, both male and female; (ii) induces a transient serological response in the Rose Bengal test in ≤50 % of sheep, confirmed to some extent by the complement fixation test, and a stronger, more persistent anti- rough-LPS response; and (iii) protects rams against a B. ovis challenge 25 weeks after vaccination. To resolve the problem of serological interference, the use of green fluorescent protein tagging strategy allowed us to identify vaccinated sheep with only a single inoculation. These results, together with the previously reported safety in pregnant ewes, position Rev1Δwzm as a firm vaccine candidate and a promising alternative to Rev1. Further experiments are warranted to assess its efficacy against B. melitensis in pregnant ewes.

Investigating the pathogens associated with Dermacentor nuttalli and its global distribution: A study integrating metagenomic sequencing, meta-analysis and niche modeling

Dermacentor nuttalli, a member of family Ixodidae and genus Dermacentor, is predominantly found in North Asia. It transmits various pathogens of human and animal diseases, such as Lymphocytic choriomeningitis mammarenavirus and Brucella ovis, leading to severe symptoms in patients and posing serious hazards to livestock husbandry. To profile pathogen abundances of wild D. nuttalli, metagenomic sequencing was performed of four field-collected tick samples, revealing that Rickettsia, Streptomyces, and Pseudomonas were the most abundant bacterial genera in D. nuttalli. Specifically, four nearly complete Rickettsia genomes were assembled, closely relative to Rickettsia conorii subsp. raoultii. Then, a comprehensive meta-analysis was performed to evaluate its potential threats based on detected pathogens and geographical distribution positions reported in literature, reference books, related websites, and field surveys. At least 48 pathogens were identified, including 20 species of bacteria, seven species of eukaryota, and 21 species of virus. Notably, Rickettsia conorii subsp. raoultii, Coxiella burnetii, and Brucella ovis displayed remarkably high positivity rates, which were known to cause infectious diseases in both humans and livestock. Currently, the primary distribution of D. nuttalli spans China, Mongolia, and Russia. However, an additional 14 countries in Asia and America that may also be affected by D. nuttalli were identified in our niche model, despite no previous reports of its presence in these areas. This study provides comprehensive data and analysis on the pathogens carried by D. nuttalli, along with documented and potential distribution, suggesting an emerging threat to public health and animal husbandry. Therefore, there is a need for heightened surveillance and thorough investigation of D. nuttalli.

Clearance of bacteria from lymph nodes in sheep immunized with Brucella suis S2 vaccine is associated with M1 macrophage activation

Ovine brucellosis is a global zoonotic disease of sheep caused by Brucella melitensis, which inflicts a significant burden on human and animal health. Brucella suis strain S2 (B. suis S2) is a smooth live attenuated vaccine for the prevention of ovine brucellosis in China. However, no previous studies have assessed the immunogenicity of B. suis S2 vaccine after oral immunization in sheep. Here, we attempted to evaluate the ovine immune response over the course of B. suis S2 immunization and to identify in vivo predictors for vaccine development. Body temperature, serum Brucella antibodies, serum cytokines (IL-12p70 and interferon [IFN]-γ), and bacterial load in the mandibular lymph nodes (LN), superficial cervical LN, superficial inguinal LN, and spleen were investigated to determine the safety and efficacy of the vaccine. The abnormal body temperature of sheep occurred within 8 days post-infection (dpi). Brucella suis S2 persisted for a short time (< 21 dpi) in the mandibular LN. The highest level of IL-12p70 was observed at 9 dpi, whereas serum IFN-γ levels peaked at 12 dpi. Transcriptome analysis and quantitative reverse transcription PCR were performed to determine gene expression profiles in the mandibular LN of sheep. Antigen processing and presentation pathway was the dominant pathway related to the dataset. Our studies suggest that the immune response in ovine LN resembled type 1 immunity with the secretion of IL-12p70 and IFN-γ after B.suis S2 immunization and the vaccine may eliminate Brucella via stimulation of M1 macrophages through the course of Th cells.

Pathogenesis of Brucella ovis in pregnant mice and protection induced by the candidate vaccine strain B. Ovis ΔabcBA

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 ΔabcBA 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 ΔabcBA (6/10 pregnant); (iv) immunized with B.ovis ΔabcBA 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 µL of sterile PBS, 100 µL of 1 × 10⁶ CFU of B.ovis ΔabcBA, or 100 µL of 1 × 10⁶ 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 ΔabcBA 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 ΔabcBA 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.