Preliminary Functional Study Of MucR And VjbR Genes Of Brucella Canis

Brucellosis is a serious zoonosis.Brucella canis mainly infects dogs and is one of 6classical species of Brucella.Brucella canis is easily overlooked because of its weak virulence and relatively low pathogenicity.With the aging of human society,the number of pet dogs kept increasing,the threat of canine brucellosis to public health safety and animal welfare cannot be ignored.In order to understand the prevalence of canine brucellosis in China and explore the pathogenic mechanism of Brucella canis,this study investigated the prevalence of canine brucellosis in some areas of China,and studied the functions of the muc R and vjb R of Brucella canis,and evaluated the protection of?vjb R against Brucella canis in mouse model.Serological tests were performed on 768 dog sera from Beijing,Shaanxi,Liaoning,and Shandong.The results showed that the rough seroprevalence in Beijing was 1.15%,the rough seroprevalence in Shaanxi was 8.24%,the rough seroprevalence in Shandong was 2.02%,and no positive was detected in Liaoning province.The smooth seroprevalence in Beijing was 1.53%,the smooth seroprevalence in Shaanxi was 2.35%,the smooth seroprevalence in Shandong was 2.02%,and no positive was detected in Liaoning province.The function of muc R and vjb R of Brucella canis was studied.The results showed that the virulence of muc R and vjb R mutant strains of Brucella canis was significantly lower than that of wild strain in cell infection model and mouse infection model.The deletion of vjb R affected the expression of type IV secretion system and the transcription of flagellum genes of Brucella canis,while the deletion of muc R not only affected the sensitivity of Brucella to various stress environments and?-lactam antibiotics,it also affected the expression of genes in translation,ribosome structure,signal transduction,energy transformation,intracellular transport and so on.Studies on the immune protection of?vjb R at different doses showed that high dose(3×10~7 CFU)of?vjb R could induce effective protection against Brucella canis,but not against smooth Brucella.In summary,this study investigated the prevalence of canine brucellosis in some areas of China,revealed the important roles of vjb R and muc R in the regulation of bacterial tolerance to stress and the expression of virulence genes.At the same time,the protection of?vjb R against Brucella canis is evaluated.This study provided data support for revealing pathogenic mechanism of Brucella canis and screening candidates of canine brucellosis vaccine.