Serological characterization of the core region of lipopolysaccharides of rough Proteus sp. strains

Abstract

Introduction: Both smooth and rough Proteus sp. strains can be found. The latter are characterized by their lack of an O--polysaccharide chain in the lipopolysaccharide (LPS) molecule, which makes them suitable for obtaining anti-core sera. Using this kind of material enables identifying fragments of the Proteus LPS core region that might be involved in cross-reactions. To date only a few similar epitopes have been established for the genus Proteus. Materials and Methods: Polyclonal rabbit antisera directed against three rough strains of Proteus sp. were tested by enzymelinked immunosorbent assay (ELISA) with a set of LPSs. The reactivity of the selected cross-reactive and homologous systems was checked by the Western blot technique and by a passive immunohemolysis assay preceded by the absorption of each antiserum with appropriate cross-reactive and homologous alkalized LPSs. Results: On the basis of the ELISA results, 19 cross-reactive antigens were selected among which both smooth and rough LPS forms were found. All the observed reactions involved the core region of the LPS. Using the antisera absorbed with the appropriate LPSs allowed identification of four groups of antigens with serologically identical core regions. Conclusions:Comparing the results of the serological studies with the known chemical structures of the core regions of the LPSs used enabled the identification of a few core oligosaccharide fragments probably involved in the observed cross-reactions. All were located in the most distal part of LPS core region, which made them more easily recognized by specific antibodies.

Classification of Proteus penneri lipopolysaccharides into core region serotypes

“…In previous serological studies, sera specific to appropriate P. penneri strains were tested with a set of 40 P. penneri LPSs and the core region serospecificity for the majority of those antigens was determined [16, 17, 19, 20]. In the present work, the reactivities of the core regions of P. penneri LPSs 2, 11, 12, 13, 16, 17, 18, 19, 24, 26, 28, 31, 35, 36, 38, 60, 63, 75, 100, 103, 107, 112, 114, 115 and 124 with five sera specific to the strains P. penneri 17, 103 (with defined structures of LPS core regions [11]), 28, 60 and 124 were analyzed by ELISA and Western blot and classified into core serotypes.…”

“…4) [11]. The previous serological studies conducted with the use of the P. penneri 13 antiserum showed its strong cross-reactivity with P. penneri 12, 124, 26 and 112 LPSs, reacting to the same reactivity titer (1:16.000) as P. penneri 13 LPS [16]. To confirm the previously obtained results, the P. penneri 13, 26 and 112 LPSs were additionally selected to be included in the present work.…”

“…LPS core region structures of: a P. penneri 12, b P. penneri 13 and c P. penneri 26 LPSs [11, 16]; Ara p 4N, 4-amino-4-deoxy- l -arabinopyranose; GalA, galacturonic acid; GalN, galactosamine; Glc, glucose; dd -Hep, d - glycero - d - manno -heptose; Kdo, 3-deoxy- d - manno -oct-2-ulosonic acid; and P Etn, 2-aminoethyl phosphate…”

“…Alkali-treated LPSs used for passive immunohemolysis (PIH) were obtained by LPS saponification with 0.25 M NaOH (2 h, 56 °C) and precipitation with 96 % ethanol [16]. …”

“…strain. The antiserum titer was determined by PIH as the last antiserum dilution resulting in 50 % hemolysis [16].

By the LPS on bacterial cells

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