Attenuation of defined Brucella melitensis wboA mutants.

Rough Brucella mutants have been sought as vaccine candidates because they do not induce seroconversion. In this study, two defined nonreverting rough mutants were derived from virulent Brucella melitensis strain 16M: a wboA deletion mutant designated WRR51 and a wboA purEK dual deletion mutant designated WRRP1. Strain WRRP1 exhibited reduced survival in human monocyte-derived macrophages (hMDMs) compared with parent strain WRR51 or with ΔpurEK strain WR201. Strain WRRP1 persisted for 1 week or less in BALB/c mice after intraperitoneal infection, while less severe attenuation was exhibited by the two single mutants in this model. Trans complementation of wboA restored the survival of WRR51 in hMDMs comparable to strain 16M and the survival of WRRP1 comparable to strain WR201.