Enzyme-linked immunosorbent assay for immunoglobulin G antibody to Pasteurella multocida in rabbits.

Three antigen preparations of Pasteurella multocida, lipopolysaccharide antigen, boiled-cell extract antigen, and boiled whole-bacterium antigen, were used in an enzyme-linked immunosorbent assay (ELISA) to detect rabbit immunoglobulin G antibody to P. multocida. The sensitivity of each antigen preparation was compared by using sera from P. multocida-infected and uninfected rabbits and sera from two rabbits immunized with different serotypes of P. multocida. In the ELISA, all three antigen preparations detected high titers of antibodies in infected rabbits and markedly lower levels in uninfected rabbits. When whole-bacterium or boiled-cell extract antigens were used, the ELISA detected antibodies in sera from both immunized rabbits, but with lipopolysaccharide antigen, only antibody to the homologous serotype was detected. Sera absorbed with P. multocida and Bordetella bronchiseptica, another respiratory pathogen of rabbits, revealed that antibodies detected in the ELISA did not cross-react. Since the lipopolysaccharide antigen was more difficult to prepare and may be type specific, and since the whole-bacterium antigen was the least sensitive, the boiled-cell extract was chosen as the best antigen preparation to use in the ELISA.

Safety and efficacy of a streptomycin dependent live Pasteurella multocida vaccine in rabbits.

The safety of and protection provided by a streptomycin dependent live Pasteurella multocida (serotype 12:A) vaccine was evaluated in New Zealand white rabbits. The vaccine strain was isolated from two of twelve rabbits 24 hours after intranasal administration. Streptomycin independent P. multocida isolates were not recovered for 4 weeks after vaccination, indicating a lack of reversion to the wild type. Thirty days after a single intranasal administration of vaccine, eight rabbits were challenged with either P. multocida serotype 3:A or serotype 12:A. Eight non-vaccinated rabbits were challenged in the same manner. Vaccinated rabbits challenged with serotype 12:A had nasal infections for only 2 weeks following challenge. Vaccinated rabbits challenged with serotype 3:A developed chronic nasal infections but were protected from severe disease. Immunoglobulin A or G antibodies against P. multocida were not detected after vaccination in nasal lavages or sera using an enzyme-linked immunosorbent assay. However, both antibodies increased following challenge with either serotype 3:A or serotype 12:A. These studies indicated that the streptomycin dependent pasteurella strain colonized rabbits briefly and was genetically stable in vivo. The results in challenged rabbits suggest that the vaccine provided protection against chronic infection by a homologous pasteurella serotype and protection against severe disease by a heterologous pasteurella serotype.