Characterization of Biological Activities of Brucella melitensis Lipopolysaccharide

Abstract

Brucella are Gram-negative intracellular pathogens which survive within a variety of cells including macrophages and maintain a long-lasting interaction with the host cells (11,15). The infection leads to acute and chronic inflammation related to the brisk interaction of Brucella-derived products, such as lipopolysaccharide (LPS) with the host cells. In fact, Brucella LPS is reported to act as a virulence factor of the infection (19,22). Most wild-type Brucella have smooth type LPS (S-LPS) consisting of three domains: lipid A, core oligosaccharide, and O-specific polysaccharide (21). Among Brucella LPSs, LPS from B. abortus has been extensively characterized (reviewed in 22). The lipid A moiety of B. abortus LPS has a fatty acid composition quite distinct from that of enterobacterial LPS. Specifically, the lipid A moiety of B. abortus LPS possesses a diaminoglucose backbone, and the acyl groups are longer (C18-19, C28) and are only linked to the core by amide bounds (22,30). Further, the O antigen of Brucella LPS is a homopolymer of perosamine (4,6-dideoxy-4-formamido-d-mannopyranosyl) (3, 27, 37). The biological activities such as cytokine production and lethality of S-LPS and rough types of LPS (R-LPS) from various Brucella strains are reported to be lower than those of enterobacterial LPS (4,14,25,29). The lower endotoxicity seems to be responsible for the unique lipid A structure of Brucella LPS. Thus, LPS from B. abortus has been studied as a representative of Brucella. On the other hand, B. melitensis is another main pathogenic species for humans worldwide (6). However, the chemical structure of B. melitensis LPS is not as fully clarified as that of B. abortus LPS. Further, there is no systemic study on the biological activities of B. melitensis LPS, although some biological activities are reported (7,(23)(24)(25). In the present study, we compared the biological activities of B. melitensis LPS with those of enterobacterial LPS in order to characterize the biological activities of B. melitensis LPS. Materials and Methods LPS.Crude LPS preparation was extracted from B. melitensis 16M (biotype 1). Briefly, washed cells of B. melitensis were autoclaved at 120 C for 30 min. After removal of the cell debris by centrifugation, the crude LPS fraction was precipitated with methanol, dialyzed and freeze-dried. For further purification, the LPS preparation was digested with DNase I, RNase and pro- Characterization of Biological Activities of

Modulation of the Bovine Trophoblastic Innate Immune Response byBrucella abortus

“…Supporting this notion, a recent study demonstrated that Salmonella enterica serotype Typhimurium induces higher levels of cytokines during the early stages of infection in mice; this is in contrast to B. abortus infection in the same model, which results in the induction of low levels of cytokines (4). This mild inflammatory response triggered by B. abortus in comparison to those seen for other gram-negative bacteria is at least in part due to the structure of its LPS, which is impaired for signaling through the TLR4 (11,18,26,45).…”

“…TLRs signal through an adapter molecule, MyD88, to activate the NF-B pathway, resulting in cytokine induction and regulation of costimulatory molecules (30, 44). However, Brucella LPS is not a strong agonist of TLR4, which favors evasion of the host innate immunity (4,11,18,26,45). Conversely, Brucella lipoproteins, which are TLR2 ligands, have a proinflammatory effect (17).…”

Persistence of an atherogenic lipid profile after treatment of acute infection with brucella

“…Indeed, TNFa is considered as one potent inhibitor of Lp-PLA 2 secretion ( 59 ). On the other hand, total plasma Lp-PLA 2 activity may increase in response to Brucella-derived products, such as lipopolysaccharide (LPS) ( 60 ). LPS increases Lp-PLA 2 mRNA expression in several macrophagerich tissues ( 60 ).…”

“…On the other hand, total plasma Lp-PLA 2 activity may increase in response to Brucella-derived products, such as lipopolysaccharide (LPS) ( 60 ). LPS increases Lp-PLA 2 mRNA expression in several macrophagerich tissues ( 60 ). Moreover, a previous study indicated the presence of anti-PAF antibodies in patients with Brucella ( 61 ).…”

“…During infection and infl ammation, serum PON1 activity decreases as a result of changes in synthesis and/or secretion of HDL particles and ApoAI ( 48,(50)(51)(52). Moreover, PON1 activity may decrease in response to Brucella-derived products, such as LPS ( 60 ). Indeed, serum PON1 activity decreases following endotoxin (LPS) administration in Syrian hamsters ( 65 ).…”