Abstract
Investigation was made on the resistance to intranasal challenge with thevirulent strain of Mycoplasma pulmonis of mice vaccinated intranasally or intramuscularlywith the formalin-killed organisms. The protective effect of vaccination was evaluated bycomparing the clinical appearance, establishment of organisms in the respiratory tract, and development of pneumonia between these mice and those unvaccinated and servingas controls. A significant protection was observed after either intranasal or intramuscularvaccination. No relationship was shown between such protective effect and serum anti-body titer. Intranasal vaccination could inhibit the establishment of organisms in therespiratory tract without causing a remarkable increase in antibody titer. In contrast, theprevention of pneumonia was observed after intramuscular vaccination resulting in producLion of high antibody Liter. These findings suggested that the mechanisms to inhibit theestablishment of organisms in the respiratory epithelium might be separate from thoseto prevent the occurrence of pneumonia.
