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Failure of ribosomes from nonencapsulated Pasteurella multocida to protect CF-1 mice
Abstract:
Monomeric ribosomes (70S) were isolated from nonencapsulated Pasteurella multocida strain X-73 by mechanical disruption and by chemical lysis. Contamination of the initial preparations by lipopolysaccharide (LPS) was evident by gel immunodiffusion. Gel filtration chromatography of the 70S ribosomes resulted in ribosomes with LPS contamination below the concentration that was detected by gel immunodiffusion, but chickens vaccinated with these preparations responded serologically to LPS by producing a detectable titer of passive hemagglutination antibody. Washing the 70S ribosomes through 0.5 M NH4Cl and 30% sucrose rendered them virtually free of contamination by LPS as evidenced by lack of passive hemagglutination titer. Ribosomes were evaluated as protective immunogens in CF-1 mice. Two inoculations (14 days apart) at each dosage level of 0.4, 40.0, and 400 microgram/mouse were given. At 21 days after vaccination, the mice were challenge exposed with encapsulated P multocida X-73 cells. None of the ribosomal preparations (crude or purified) protected against challenge exposure. Killed whole nonencapsulated cells did protect against challenge exposure. In contrast to numerous reports on the effectiveness of ribosomes as protective immunogens, ribosomes from nonencapsulated P multocida cells were not protective immunogens in mice challenge exposed with encapsulated cells under these conditions.
Insights
Ribosomes from nonencapsulated Pasteurella multocida did not protect mice from infection. Further purification removed lipopolysaccharide (LPS) but did not enhance protective immunity in this study.
Area of Science:
- Bacteriology
- Immunology
- Vaccine Development
Background:
- Pasteurella multocida is a significant pathogen causing various diseases in animals.
- Ribosomes have been explored as potential vaccine candidates due to their immunogenic properties.
- Nonencapsulated strains of P. multocida may possess different antigenic profiles compared to encapsulated strains.
Purpose of the Study:
- To investigate the protective efficacy of ribosomes isolated from nonencapsulated Pasteurella multocida as a vaccine.
- To assess the impact of lipopolysaccharide (LPS) contamination on ribosomal vaccine effectiveness.
- To compare the immunogenicity of purified and crude ribosomal preparations.
Main Methods:
- Isolation of monomeric (70S) ribosomes from nonencapsulated P. multocida strain X-73.
- Purification of ribosomes using gel filtration chromatography and washing with NH4Cl and sucrose.
- Vaccination of mice with varying doses of ribosomal preparations followed by challenge exposure with encapsulated P. multocida.
Main Results:
- Crude and purified ribosomal preparations from nonencapsulated P. multocida did not confer protection against challenge with encapsulated P. multocida.
- Chickens vaccinated with LPS-contaminated ribosomes produced antibodies against LPS.
- Purification significantly reduced LPS contamination, evidenced by a lack of passive hemagglutination titer.
- Killed whole nonencapsulated cells provided protection, indicating the viability of the bacterial source.
Conclusions:
- Ribosomes derived from nonencapsulated P. multocida were ineffective as protective immunogens in mice under the tested conditions.
- LPS contamination in ribosomal vaccines can elicit a serological response but does not guarantee protection against encapsulated strains.
- Further research is needed to understand the limitations of ribosomal vaccines from nonencapsulated bacteria.