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Studies on immunity to Haemophilus pleuropneumoniae infections in mice
Abstract:
A murine model of experimentally induced Haemophilus pleuropneumoniae respiratory tract infections was developed and used to evaluate the efficacy of bacterins. Various doses of 3 H pleuropneumoniae strains (serotype 1 and 5) were administered intranasally (IN) to groups of anesthetized Swiss White mice. The accumulated mortality per group at 5 days after they were inoculated was used to calculate the median lethal dose (LD50), which ranged between 1.4 x 10(6) and 5.4 x 10(7) bacteria. There was correlation between dose administered, incubation period of the disease, and mortality. The induction of H pleuropneumoniae disease in the mouse was reproducible and resembled that of naturally occurring porcine Haemophilus pleuropneumonia. The murine model of exposure was used to evaluate the efficacy of H pleuropneumoniae serotype 5 (strain B78-3760) bacterins administered subcutaneously (SC) and IN. Vaccination by SC route induced slightly higher titers of specific seroagglutinins, compared with the response induced by the IN route, and the former was more effective in protecting mice against IN challenge with H pleuropneumoniae. However, vaccination was not efficacious in mice given a challenge dose greater than 1.2 LD50. The percentage survival rates in the SC and IN vaccinated mice were significantly greater than in the control groups at P less than 0.01 and P less than 0.05, respectively.
Insights
A new mouse model effectively mimics porcine Haemophilus pleuropneumonia. Vaccination showed protection against this respiratory infection, though efficacy decreased with higher bacterial challenge doses.
Area of Science:
- Veterinary Microbiology
- Infectious Diseases
- Animal Models
Background:
- Haemophilus pleuropneumoniae causes significant respiratory disease in swine.
- Developing reliable animal models is crucial for evaluating vaccine efficacy.
Purpose of the Study:
- To establish a reproducible murine model for Haemophilus pleuropneumonia.
- To assess the efficacy of bacterins against H. pleuropneumoniae infection in mice.
Main Methods:
- Induction of respiratory tract infections in Swiss White mice using intranasal inoculation of H. pleuropneumoniae strains.
- Determination of median lethal dose (LD50) and evaluation of mortality, incubation period, and disease progression.
- Administration of H. pleuropneumoniae serotype 5 bacterins via subcutaneous (SC) and intranasal (IN) routes, followed by IN challenge.
Main Results:
- A reproducible murine model was established, mirroring porcine disease characteristics.
- Subcutaneous vaccination induced higher seroagglutinin titers and offered better protection than intranasal vaccination.
- Vaccine efficacy was limited when challenge doses exceeded 1.2 LD50, though vaccinated groups showed significantly higher survival rates than controls.
Conclusions:
- The developed murine model is suitable for studying H. pleuropneumoniae pathogenesis and vaccine efficacy.
- Bacterin vaccination provides partial protection against H. pleuropneumoniae, with subcutaneous administration being more effective.
- Further research is needed to enhance vaccine efficacy against higher challenge doses.