Rough mutants defective in core and O-polysaccharide synthesis and export induce antibodies reacting in an indirect ELISA with smooth lipopolysaccharide and are less effective than Rev 1 vaccine against Brucella melitensis infection of sheep

Brucellosis at the animal/ecosystem/human interface at the beginning of the 21st century

“…In controlled experiments, a single dose of Rev 1 induces 80-100% protection against challenges infecting 100% of unvaccinated controls (Barrio et al, 2009). It has a low cost (5D cents per dose when applied conjunctivally).…”

“…First, the O-polysaccharide is critical for Brucella virulence and R mutants may be over attenuated and induce insufficient protection. Secondly, it is known that ruminants vaccinated with R vaccines develop antibodies to the O-polysaccharide when exposed to virulent S brucellae (Barrio et al, 2009;Moriyon et al, 2004). Thus, healthy vaccinated animals in endemic areas may be not so readily differentiated by S-LPS tests from the infected ones.…”

“…However, core epitopes become exposed upon adsorption of S-LPS to plastics and are also present and accessible in the polysaccharides obtained by acid hydrolysis of S-LPS. Thus, immunization with Brucella R mutants generates antibodies reacting in immunosorbent assays or in fluid phase assays that use S-LPS or hydrolytic polysaccharides (several indirect or competitive ELISAs and the fluorescence polarization assay) (Barrio et al, 2009). These limitations have been confirmed using both spontaneous R mutants and genetically designed R vaccines.…”

Lipopolysaccharide as a target for brucellosis vaccine design

“…Also, mutants devoid of the O-PS (i.e. rough mutants) have been extensively investigated [18][19][20][21] (see rough vaccines below).…”

“…The O-PS is involved also in Brucella virulence: it contributes to complement resistance and, more important, critically modulates bacterial entry into cells so that its removal causes attenuation. Nevertheless, vaccines devoid of this LPS section (the so-called Brucella rough vaccines) do not completely solve the diagnostic problems and are considerably less protective than S19 or Rev 1 [19,21] possibly because their severely affected entry into host cells results in over attenuation. On the other hand, low endotoxicity, reduced bactericidal peptide binding and poor complement activation speak of peculiarities in the sections that in typical LPS carry the PAMP triggering TLR4-MD2 mediated responses.…”