A novel capsular polysaccharide from /Rhizobium rubi/ strain DSM 30149

Rhizobium rubi, strain DSM 30149, is a Gram negative phytopathogenic bacterium which produces a linear polysaccharide with the following repeating unit: [4)-α-L-Rhap-(1→3)-α-L-Rhap-(1→2)-β-L-3OMe-Rhap-(1→]n This new structure was determined by spectroscopical and chemical methods. It presents similar lipophilic features reported for another strain of R. rubi. These contrast with features already known for capsular polysaccharide species from symbiontic members of the Rhizobiaceae family, namely highly anionic polymers

A Bacterial Lipooligosaccharide that Naturally Mimics the Epitope of the HIV-Neutralizing Antibody 2G12 as a Template for Vaccine Design

The broadly neutralizing antibody 2G12 binds a fairly conserved cluster of oligomannose sugars on the HIV surface glycoprotein gp120, which has led to the hypothesis that these sugars pose potential vaccine targets. Here, we present the chemical analysis, antigenicity, and immunogenicity of a bacterial lipooligosaccharide (LOS) comprised of a manno-oligosaccharide sequence analogous to the 2G12 epitope. Antigenic similarity of the LOS to oligomannose was evidenced by 2G12 binding to the LOS and the inability of sera elicited against synthetic oligomannosides, but incapable of binding natural oligomannose, to bind the LOS. Immunization with heat-killed bacteria yielded epitope-specific serum antibodies with the capacity to bind soluble gp120. Although these sera did not exhibit specific anti- HIV activity, our data suggest that this LOS may find utility as a template for the design of glycoconjugates to target HIV

Occurrence and structure of cyclic Enterobacterial Common Antigen in Escherichia coli O157:H−

Abstract Two cyclic forms of the Enterobacterial Common Antigen were isolated from Escherichia coli O157:H−. These antigenic determinants were purified from the biomass through extensive chemical, enzymatic and chromatographic procedures whereas MALDI MS spectrometry indicated their cyclic nature with a polymerization degree of 4 or 5. The two species, denoted as ECACYC-4 and ECACYC-5, were assigned by NMR and showed no further substitution with other appendages such as acetyl groups as usually described for similar cyclic antigens from other Enterobacteriacea

Complete lipooligosaccharide structure of the clinical isolate Acinetobacter baumannii, strain SMAL

Acinetobacter baumannii is a pathogenic organism that posesses a serious health threat because of the occurrence of the large number of (multi)drug-resistant strains. It can persist for prolonged periods in the hospital environment, infecting debilitated or immune-compromised patients. In this context, the endotoxin portion of the lipopolysaccharide, the lipid A, plays an important role in the pathogenesis of this bacterium, because it triggers the innate immune response and contributes to the inflammation state of the patient. In this study, the complete structure of the lipooligosaccharide has been determined. The saccharide backbone of the molecule was disclosed through chemical and spectroscopic analysis, whereas the lipid A moiety required detailed MS spectrometry and chemical investigations. The oligosaccharide backbone was found to be similar to that of A. baumannii ATCC 19606, although the LOS from the SMAL strain presented an enhanced zwitterionic character. The lipid A moiety comprises a heterogeneous and complex mixture of molecules: it possesses a conserved diphosphorylated disaccharide backbone substituted by three to seven fatty acids. The hexaacylated species appeared as the most abundant, and its chemical features, namely the number and the types of fatty acids, indicates its potential endotoxic activity