Deletion of the GI-2 integrase and the wbkA flanking transposase improves the stability of Brucella melitensis Rev 1 vaccine
نویسندگان
چکیده
Brucella melitensis Rev 1 is the best vaccine available for the prophylaxis of small ruminant brucellosis and, indirectly, for reducing human brucellosis. However, Rev 1 shows anomalously high rates of spontaneous dissociation from smooth (S) to rough (R) bacteria, the latter being inefficacious as vaccines. This S-R instability results from the loss of the O-polysaccharide. To overcome this problem, we investigated whether some recently described mechanisms promoting mutations in O-polysaccharide genes were involved in Rev 1 S-R dissociation. We found that a proportion of Rev 1 R mutants result from genome rearrangements affecting the wbo O-polysaccharide loci of genomic island GI-2 and the wbkA O-polysaccharide glycosyltransferase gene of the wbk region. Accordingly, we mutated the GI-2 int gene and the wbk IS transposase involved in those arrangements, and found that these Rev 1 mutants maintained the S phenotype and showed lower dissociation levels. Combining these two mutations resulted in a strain (Rev 2) displaying a 95% decrease in dissociation with respect to parental Rev 1 under conditions promoting dissociation. Rev 2 did not differ from Rev 1 in the characteristics used in Rev 1 typing (growth rate, colonial size, reactivity with O-polysaccharide antibodies, phage, dye and antibiotic susceptibility). Moreover, Rev 2 and Rev 1 showed similar attenuation and afforded similar protection in the mouse model of brucellosis vaccines. We conclude that mutations targeting genes and DNA sequences involved in spontaneous O-polysaccharide loss enhance the stability of a critical vaccine phenotype and complement the empirical stabilization precautions taken during S Brucella vaccine production.
منابع مشابه
Evaluation on stability process of Brucella melitensis - Rev. 1 vaccine in Iran
According to the reports of WHO, stability of Rev.1 vaccine should take more than one year, while the expiring date for the vaccine produced in Iran is 3 to 4 months, therefore any attempt to elongate the stability of this vaccine can solve many problems of the production including the request of Veterinary Organization of Iran in this regard. The objective of this study was to increase the sta...
متن کاملCloning and molecular characterization of Omp31 gene from Brucella melitensis Rev 1 strain
Brucellosis, caused by the genus Brucella bacterium, is a well-known infection among domestic animals. Considering the serious economic and medical consequences of this infection, various preventive efforts have been made through using recombinant vaccines, based on outer membrane protein (OMP) antigens of Brucella species. The objective of the present study was to clone, analyze the sequence, ...
متن کاملSpontaneous excision of the O-polysaccharide wbkA glycosyltranferase gene is a cause of dissociation of smooth to rough Brucella colonies.
The brucellae are Gram-negative pathogens that cause brucellosis, a zoonosis of worldwide importance. The genus Brucella includes smooth and rough species that differ in that they carry smooth and rough lipopolysaccharides, respectively. Brucella abortus, B. melitensis, and B. suis are typical smooth species. However, these smooth brucellae dissociate into rough mutants devoid of the lipopolysa...
متن کاملIsolation, cloning and expression of the Brucella melitensis Omp31 gene
Brucellosis is a zoonotic disease transmitted to humans either from animals or from their products.Although brucellosis can be found worldwide, the Mediterranean Basin, South and Central America, EasternEurope, Asia, Africa, the Caribbean, and the Middle East have currently been listed as high-risk regions. Thegenus Brucella is classified in at least nine species. Brucella melitensis is the glo...
متن کامل