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Murine immunoprotective activity of Klebsiella pneumoniae cell surface preparations: comparative study with ribosomal
Abstract:
Cell surface preparations and ribosomal preparations were extracted from Klebsiella pneumoniae. Agar gel diffusion with antisera to cell surface preparations or ribosomal preparations indicated common antigenic components among the preparations. Lipopolysaccharide and capsular polysaccharide were identified in the cell surface preparations. These results and the previous identification of lipopolysaccharide and capsular polysaccharide in ribosomal preparations suggest that these antigens are responsible for the immunochemical cross-reactivity observed among these two bacterial extracts. Active protection could be induced in mice by these two preparations. On a dry-weight basis, cell surface preparations provided better immunoprotective activity than did ribosomal preparations. However, the 50% protective dose of both preparations is practically the same on the basis of their capsular polysaccharide content. These results are consistent with the hypothesis that the immunoprotective moiety of ribosomal preparations is the contaminating cell surface antigens. Furthermore, the low level of nucleotidic components detected in purified cell surface preparations led us to infer that the immunoprotective activity of capsular polysaccharide may not be dependent on the adjuvant activity of ribonucleic acid. The involvement of capsular polysaccharide in the immunoprotective capacity of cell surface preparations is demonstrated either by using a degradation of this antigen by K. pneumoniae bacteriophage K2-associated glycanase or by using a preparation extracted from a noncapsulated mutant of K. pneumoniae. Nevertheless, the low protective ability of purified capsular polysaccharides is in contrast to its greater activity when induced in bacterial cell surface preparations. The protective activity of K. pneumoniae capsular polysaccharide may be dependent on its association with other surface antigenic components present in cell surface preparations or may be dependent on its native form in the bacterial cell surface.
Insights
Cell surface and ribosomal preparations from Klebsiella pneumoniae share common antigens, with capsular polysaccharide being key for protection. Cell surface antigens likely contaminate ribosomal preparations, explaining cross-reactivity and immunoprotection.
Area of Science:
- Immunology
- Microbiology
- Bacteriology
Background:
- Klebsiella pneumoniae possesses cell surface and ribosomal components that elicit immune responses.
- Previous studies identified lipopolysaccharide and capsular polysaccharide in both cell surface and ribosomal preparations.
Purpose of the Study:
- To investigate the antigenic relationship between cell surface and ribosomal preparations of Klebsiella pneumoniae.
- To determine the role of specific antigens, particularly capsular polysaccharide, in the immunoprotective capacity of these preparations.
Main Methods:
- Extraction of cell surface and ribosomal preparations from Klebsiella pneumoniae.
- Agar gel diffusion assays to assess antigenic similarities.
- Induction of active protection in mice using bacterial preparations.
- Enzymatic degradation of capsular polysaccharide and use of non-encapsulated mutants.
Main Results:
- Common antigenic components were detected between cell surface and ribosomal preparations.
- Lipopolysaccharide and capsular polysaccharide were identified as major antigens.
- Both preparations induced active protection in mice, with cell surface preparations showing higher activity on a dry-weight basis.
- Immunoprotective activity correlated with capsular polysaccharide content, suggesting it as the primary protective antigen.
Conclusions:
- The immunochemical cross-reactivity and immunoprotective activity of ribosomal preparations are likely due to contaminating cell surface antigens, primarily capsular polysaccharide.
- The protective capacity of capsular polysaccharide may depend on its association with other surface antigens or its native form within the bacterial cell surface.