Development of a genetically modified nontoxigenic Pasteurella multocida toxin as a candidate for use in vaccines against progressive atrophic rhinitis in pigs.
OBJECTIVE
To construct a genetically modified nontoxigenic Pasteurella multocida toxin (PMT) and examine its immunoprotective activity against challenge exposure with wild-type PMT in pigs.


METHODS
5 healthy pigs.


METHODS
A nontoxigenic PMT was created by replacing the serine at position 1164 with alanine (S1164A) and the cysteine at position 1165 with serine (C1165S). Toxic activity was determined by use of the guinea pig skin test and mouse lethality test. Three pigs were vaccinated twice with the modified PMT, and the remaining 2 pigs served as nonvaccinated control animals. Vaccinated and control pigs were challenge exposed with wild-type PMT. Pigs were euthanatized and necropsied on day 14 after challenge exposure. Turbinate atrophy was examined macroscopically and assigned a score. Serum anti-PMT antibodies were determined by use of an ELISA.


RESULTS
The genetically modified PMT was characterized by a total lack of toxic activity. Pigs vaccinated with the modified PMT became seropositive; in contrast, control pigs remained seronegative. Necropsy revealed that the 2 control pigs had moderate and severe turbinate atrophy, respectively, whereas the 3 vaccinated pigs did not have any lesions in the turbinates or abnormalities in other organs.


CONCLUSIONS
Modification by use of S1164A and C1165S leads to a complete loss of toxic effects of PMT without impairment of the ability to induce protective immunity in pigs. Analysis of these results suggests that genetically modified PMT may represent a good candidate for use in developing a vaccine against progressive atrophic rhinitis in pigs.
To
Ho
H
Nippon Institute for Biological Science, 9-2221-1 Shinmachi, Ome, Tokyo 198-0024, Japan.
Someno
Shuichi
S
Nagai
Shinya
S
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000633:toxicity; D001427:Bacterial Toxins / Q000096:biosynthesis / Q000235:genetics* / Q000633:toxicity; D001428:Bacterial Vaccines / Q000096:biosynthesis / Q000633:toxicity; D004926:Escherichia coli; D006168:Guinea Pigs; D051379:Mice; D016979:Pasteurella multocida / Q000276:immunology*; D012222:Rhinitis, Atrophic / Q000517:prevention & control / Q000662:veterinary*; D013552:Swine; D013553:Swine Diseases / Q000517:prevention & control*; D014614:Vaccines, Synthetic / Q000096:biosynthesis / Q000633:toxicity
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D001428:Bacterial Vaccines; C062258:Pasteurella multocida toxin; D014614:Vaccines, Synthetic