1. Vaccine properties of Brucella melitensis 16MΔwzm and reactivation of placental infection in pregnant sheep.
- Author
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Zabalza-Baranguá, A., Poveda-Urkixo, I., Mena-Bueno, S., Ramírez, G.A., De Bolle, X., and Grilló, M.J.
- Subjects
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BRUCELLA melitensis , *SHEEP , *PLACENTA , *ROSE bengal , *ZOONOSES , *SHEEP farming - Abstract
Brucellosis, a worldwide zoonotic disease, is endemic in many developing countries. Besides causing significant economic losses for the livestock industry, it has severe consequences for human health. In endemic regions, small ruminants infected by Brucella melitensis are the main source of human brucellosis. Rev1, the only vaccine currently recommended to control the disease in sheep and goats, has several drawbacks. Rough lipopolysaccharide (R-LPS) mutants have been tested as alternatives, but most lack efficacy. Those in the Wzm/Wzt system responsible for O-polysaccharide export to the periplasm have been proposed as promising vaccine candidates, although to date they have been scarcely investigated in the natural host. In the present work, we studied the biological properties of a 16MΔ wzm in-frame deletion mutant, including its safety in pregnant mice and sheep. In mice, 16MΔ wzm prevented placental and fetal infections before parturition and protected against B. melitensis and Brucella ovis infections. In sheep, 16MΔ wzm was equally safe in lambs, rams, and non-pregnant ewes, inducing some transient Rose Bengal reactions (<7 weeks). The serological reactions occurred earlier and more strongly in pregnant than in non-pregnant ewes and were significantly reduced when conjunctival rather than subcutaneous vaccination was used. In ewes vaccinated at mid-pregnancy, 16MΔ wzm was not shed in vaginal discharges during the pregnancy and did not induce abortions/stillbirths. However, some ewes showed a transitory reactivation of infection in placentas and/or milk at parturition, accompanied by a seroconversion in smooth LPS (S-LPS) and/or R-LPS tests. Overall, 16MΔ wzm can be considered as a safe vaccine for lambs, rams, and non-pregnant ewes, but its use at mid-pregnancy should be avoided to prevent vaccine dissemination at parturition. If the efficacy results against B. melitensis and B. ovis observed in mice are confirmed by further studies in the natural host, 16MΔ wzm could constitute a useful vaccine. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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