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Characterization of polyagglutinating and surface antigens in Pseudomonas aeruginosa
Abstract:
Mutants of Pseudomonas aeruginosa PAC1R (serotype O:3) which were resistant to bacteriophage D were isolated and shown to react with O:5d, O:9 and O:13 antisera as well as O:3. Antisera to the parent strain and to the three polyagglutinating (PA) mutants also showed cross-reactions. The mutants differed from the parent strain in their lipopolysaccharide (LPS) composition. The LPS from two of the three mutants yielded high molecular weight polysaccharide fractions. Although the high molecular weight fraction from one of the mutants contained the amino sugars and other components characteristic of the O:3 serotype strains, its mobility on Sephadex G75 was different from that of the parent strain. The high molecular weight material from the second mutant lacked the O-antigenic determinants but these were present in a semi-rough LPS fraction. The third mutant appeared rough and completely lacked the O-antigenic components. These three mutants were compared with the parent strain and with a non-agglutinating LPS-defective mutant which lacked both O-antigenic side chains and all neutral sugars in the outer core. Agglutination with absorbed sera and haemagglutination using purified LPS and ELISA detection suggested that wall components other than LPS were responsible for some of the cross-reactions observed. The components responsible were detected after SDS-PAGE of crude outer membrane fractions by a combination of Coomassie blue and silver-staining and antigenic components were detected by immunoelectrophoresis and ELISA-linked immunoblotting of the gels. The main antigenic determinants detected by antiserum to the parent strain were in the high molecular weight O-polysaccharide fractions and in the semirough fractions of the LPS, with some activity due to the H protein of the outer membrane. O:5d antisera reacted with unidentified high molecular weight polysaccharide fractions. Cross-reactions with the O:9 antiserum appeared to be due mainly to the F porin and, to a lesser extent, to the G and E proteins of the outer membrane. O:13 antiserum reacted with high molecular weight polysaccharide fractions but also with the rough core and F and H protein. Cross-reactivity of the other three mutant antisera could largely be interpreted in terms of the outer membrane components exposed in each strain. One reacted strongly with the F porin and the rough core, while the others reacted with a number of protein and LPS-derived fractions.(ABSTRACT TRUNCATED AT 400 WORDS)
Insights
Pseudomonas aeruginosa mutants showed altered lipopolysaccharide (LPS) composition, leading to cross-reactions with different antisera. Outer membrane proteins, not just LPS, were identified as key contributors to these antigenic cross-reactions.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Pseudomonas aeruginosa serotyping is crucial for epidemiological tracking and vaccine development.
- Lipopolysaccharide (LPS) is a primary antigen used for serotyping, but cross-reactions can complicate identification.
- Bacteriophage resistance can be linked to alterations in surface antigens like LPS.
Purpose of the Study:
- To investigate the antigenic properties of Pseudomonas aeruginosa mutants resistant to bacteriophage D.
- To identify the specific components responsible for observed cross-reactions between parent strains and mutants.
- To elucidate the role of lipopolysaccharide (LPS) and outer membrane proteins in serological cross-reactivity.
Main Methods:
- Isolation and characterization of bacteriophage-resistant Pseudomonas aeruginosa mutants.
- Analysis of lipopolysaccharide (LPS) composition and molecular weight using techniques like Sephadex G75 chromatography.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), immunoelectrophoresis, and ELISA-linked immunoblotting to identify antigenic components in outer membrane fractions.
Main Results:
- Mutants exhibited altered LPS composition, with some retaining high molecular weight polysaccharide fractions and others showing rough LPS or lacking O-antigenic components.
- Cross-reactions were not solely due to LPS; outer membrane proteins, including F porin and H protein, were identified as significant contributors.
- Specific antisera cross-reacted with various LPS fractions and outer membrane proteins, indicating complex antigenic relationships.
Conclusions:
- Serological cross-reactions in Pseudomonas aeruginosa are influenced by both LPS structure and the presence of specific outer membrane proteins.
- Outer membrane proteins play a critical role in the antigenic profile of Pseudomonas aeruginosa, contributing to observed cross-reactivity.
- Understanding these complex antigenic interactions is vital for accurate serotyping and the development of effective immunodiagnostics and vaccines.