Structural studies on the lipopolysaccharide core of Proteus OX strains used in Weil–Felix test: a mass spectrometric approach

Recent Advances in the Immunologic Method Applied to Tick-Borne Diseases in Brazil

Zoonotic-origin infectious diseases are one of the major concerns of human and veterinary health systems. Ticks, as vectors of several zoonotic diseases, are ranked second only to mosquitoes as vectors. Many ticks’ transmitted infections are still endemic in the Americas, Europe, and Africa and represent approximately 17% of their infectious diseases population. Although our scientific capacity to identify and diagnose diseases is increasing, it remains a challenge in the case of tick-borne conditions. For example, in 2017, 160 cases of the Brazilian Spotted Fever (BSF, a tick-borne illness) were confirmed, alarming the notifiable diseases information system. Conversely, Brazilian borreliosis and ehrlichiosis do not require notification. Still, an increasing number of cases in humans and dogs have been reported in southeast and northeastern Brazil. Immunological methods applied to human and dog tick-borne diseases (TBD) show low sensitivity and specificity, cross-reactions, and false IgM positivity. Thus, the diagnosis and management of TBD are hampered by the personal tools and indirect markers used. Therefore, specific and rapid methods urgently need to be developed to diagnose the various types of tick-borne bacterial diseases. This review presents a brief historical perspective on the evolution of serological assays and recent advances in diagnostic tests for TBD (ehrlichiosis, BSF, and borreliosis) in humans and dogs, mainly applied in Brazil. Additionally, this review covers the emerging technologies available in diagnosing TBD, including biosensors, and discusses their potential for future use as gold standards in diagnosing these diseases.

The properties of chitosan complexes with smooth and rough forms of lipopolysaccharides on CHO-K1 cells

The negative charge of LPS molecule and the presence of fatty acids in lipid A structure make it capable of binding with chitosan. In the presented work we analyzed the interactions of chitosan with LPS of Burkholderia cepacia or Proteus mirabilis and biological effects of these complexes on CHO-K1 cells. We observed that the presence of O-polysaccharide part of LPS (S1959), core region (R110) or lack of fatty acids in lipid A increased binding affinity of endotoxin with chitosan. However, lipid A of B. cepacia or P. mirabilis R45 might interact with CHO-K1 cells membrane alone or mediated by chitosan, respectively. In conclusion, the presence of two (B. cepacia) or one (P. mirabilis R45) Ara4N residues in lipid A part, promoted binding to cell membrane of CHO-K1 cells, alone or in the presence of chitosan, respectively. Chitosan reduced biological potencies of P. mirabilis lipid A R45 structure and this effect depended on the presence of O-PS. Lipid A of B. cepacia induced oxidative DNA damage in CHO-K1 cells.

Structure and serology of O-antigens as the basis for classification of Proteus strains

This review is devoted to structural and serological characteristics of the O-antigens (O-polysaccharides) of the lipopolysaccharides of various Proteus species, which provide the basis for classifying Proteus strains to Oserogroups. The antigenic relationships of Proteus strains within and beyond the genus as well as their O-antigenrelated bioactivities are also discussed.

Lipopolysaccharides fromSerratia marcescens Possess One or Two 4-Amino-4-deoxy-L-arabinopyranose 1-Phosphate Residues in the Lipid A andD-glycero-D-talo-Oct-2-ulopyranosonic Acid in the Inner Core Region

The carbohydrate backbones of the core-lipid A region were characterized from the lipopolysaccharides (LPSs) of Serratia marcescens strains 111R (a rough mutant strain of serotype O29) and IFO 3735 (a smooth strain not serologically characterized but possessing the O-chain structure of serotype O19). The LPSs were degraded either by mild hydrazinolysis (de-O-acylation) and hot 4 M KOH (de-N-acylation), or by hydrolysis in 2 % aqueous acetic acid, or by deamination. Oligosaccharide phosphates were isolated by high-performance anion-exchange chromatography. Through the use of compositional analysis, electrospray ionization Fourier transform mass spectrometry, and 1H and 13C NMR spectroscopy applying various one- and two-dimensional experiments, we identified the structures of the carbohydrate backbones that contained D-glycero-D-talo-oct-2-ulopyranosonic acid and 4-amino-4-deoxy-L-arabinose 1-phosphate residues. We also identified some truncated structures for both strains. All sugars were D-configured pyranoses and alpha-linked, except where stated otherwise.

Structural characterization of complex bacterial glycolipids by Fourier transform mass spectrometry

Bacterial glycolipids are complex amphiphilic molecules which are on the one hand of utmost importance for the organization and function of bacterial membranes, and which on the other hand play a major role in the activation of cells of the innate and adaptive immune system of the host. Already small alterations of their chemical structure may influence the biological activity tremendously. Due to their intrinsic biological heterogeneity [number and type of fatty acids, saccharide structures, and substitution with e.g. phosphate (P), 2-aminoethyl- (pyro)phosphate groups (P-Etn) or 4-amino-4-deoxyarabinose (Ara4N)], separation of the different components are a prerequisite for unequivocal chemical and NMR structural analyses. In this contribution the structural information which can be obtained from heterogeneous samples of glycolipids by Fourier transform (FT) ion cyclotron resonance mass spectrometric methods is described. By means of recently analysed complex biological samples the possibilities of high resolution electrospray ionization FT-MS are demonstrated. Capillary skimmer dissociation, as well as tandem mass spectrometry MS/MS analysis utilizing collision-induced dissociation and infrared multiphoton dissociation, are compared and their advantages to provide structural information of diagnostic importance are discussed.

Application of electrospray ionization with Fourier transform ion cyclotron resonance mass spectrometry for structural screening of core oligosaccharides from lipopolysaccharides of the bacteria Proteus

Electrospray ionization with Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) was used for screening and structural elucidation of core oligosaccharides isolated from lipopolysaccharides of bacteria of the genus Proteus. Mass spectra allowed the determination of the molecular masses with high accuracy and the estimation of the chemical heterogeneity of the samples. They did not, however, provide sufficient information to identify structural details of the branched oligosaccharides. Therefore, various fragmentation techniques for determining such details were examined. Infrared multiphoton dissociation tandem mass spectrometry (IRMPD-MS/MS) experiments in negative ion mode resulted in cleavage between the structurally conserved inner core region and the variable outer core region. Positive ion capillary skimmer dissociation mass spectra showed numerous fragment ion peaks, including those corresponding to the subsequent cleavage of the glycosidic linkages starting from the non-reducing end of the oligosaccharide. Despite their complexity, these mass spectrometric studies allowed confirmation of previously determined Proteus lipopolysaccharide core structures, and identification of new related structures in other strains of these bacteria.