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Published on: May 23, 2021
ECA-immunogenicity of Proteus mirabilis strains
Katarzyna Anna Duda1, Katarzyna Teresa Duda, Agnieszka Beczała
1Department of Microbiology, Faculty of Biology and Environment Protection, University of Silesia, Katowice, Poland.
Introduction:
Bacteria of the genus Proteus are opportunistic pathogens and cause mainly urinary tract infections. They also play a role in the pathogenesis of reactive arthritis (RA). Patients suffering from Yersinia-triggered RA often carry high titers of antibodies specific to enterobacterial common antigen (ECA). The immunogenicity of ECA has not received much attention thus far and studies have focused mainly on the ECA of Escherichia coli and Yersinia enterocolitica. In this paper the ECA-immunogenicity of Proteus mirabilis is elucidated using two wild-type strains (S1959 and O28) as well as their rough (R) derivative strains R110/1959, which expresses lipopolysaccharide (LPS) with a full core, and R4/O28, which expresses LPS with only an inner core.
Materials And Methods:
Rabbit polyclonal antisera were produced by immunization with boiled suspensions of the four P. mirabilis strains. The antisera were tested for the presence of antibodies specific to ECA by Western blotting using glycerophospholipid- linked ECA (ECA(PG)) of Salmonella montevideo as antigen. Lipopolysaccharide (LPS) was isolated from the four strains by the hot phenol/water procedure in which ECA(PG) is co-extracted with LPS and by the phenol/chloroform/petroleum ether extraction that results in the isolation of LPS and/or LPS-linked ECA (ECA(LPS)) free of ECA(PG). The LPS preparations were tested for the presence of ECA by Western blotting using ECA-specific antibodies.
Results:
The results demonstrated that all four P. mirabilis strains were ECA immunogenic. The rabbit antisera immunized by the four strains all contained ECA-specific antibodies. Analysis of the LPS preparations demonstrated that the P. mirabilis wild-type strains O28 and S1959 and the Ra mutant strain R110/1959 expressed ECA(LPS), suggesting that it induced the anti-ECA antibody responses. Only the presence of ECA(PG) could be demonstrated in the Rc mutant strain R4/O28.
Conclusions:
These results therefore suggest that, similar to E. coli, LPS with a full core is also required as the acceptor of ECA for P. mirabilis strains to produce ECA(LPS). Since ECA(PG) is not immunogenic unless combined with some proteins, it is likely that ECA(PG)-protein complexes formed during the intravenous immunization with the Rc mutant strain R4/O28.
Insights
Proteus mirabilis strains are immunogenic, producing antibodies against enterobacterial common antigen (ECA). A full lipopolysaccharide (LPS) core is necessary for P. mirabilis to express ECA, linking it to potential roles in reactive arthritis.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Proteus species are opportunistic pathogens linked to urinary tract infections and reactive arthritis.
- Enterobacterial common antigen (ECA) is implicated in Yersinia-triggered reactive arthritis, but its immunogenicity in Proteus is understudied.
- Previous research focused on ECA from Escherichia coli and Yersinia enterocolitica.
Purpose of the Study:
- To investigate the immunogenicity of enterobacterial common antigen (ECA) in Proteus mirabilis.
- To explore the role of lipopolysaccharide (LPS) structure in ECA expression and immunogenicity in P. mirabilis.
Main Methods:
- Production of rabbit polyclonal antisera against four P. mirabilis strains (two wild-type, two rough mutants).
- Western blotting was used to detect ECA-specific antibodies in antisera and ECA presence in LPS preparations.
- Lipopolysaccharide (LPS) and LPS-linked ECA (ECA(LPS)) were isolated using hot phenol/water and phenol/chloroform/petroleum ether methods.
Main Results:
- All four P. mirabilis strains demonstrated ECA immunogenicity, with antisera containing ECA-specific antibodies.
- Wild-type and Ra mutant strains (R110/1959) expressed ECA(LPS), indicating its role in inducing anti-ECA responses.
- The Rc mutant strain (R4/O28) primarily expressed glycerophospholipid-linked ECA (ECA(PG)), not ECA(LPS).
Conclusions:
- A full lipopolysaccharide (LPS) core acts as an acceptor for ECA in P. mirabilis, similar to E. coli, to form immunogenic ECA(LPS).
- The immunogenicity of ECA(PG) in the Rc mutant likely involves complex formation with proteins during immunization.
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