Study on the immunological heterogeneity of Clostridium botulinum B type toxin.

The toxins prepared by dialysis-culture method from proteolytic (P) and nonproteolytic (NP) strains of C. botulinum were different. NP toxins from 3 strains (American, Japanese and Polish) showed a higher activation ratio, lower protein nitrogen content, and lower neutralization rate compared with P toxins. Antitoxic titers of rabbit anti-P and especially anti-NP sera were always higher when titrated with NP than with P toxins. The values of the regression coefficients in neutralization experiments were not dependent on the sera preparations, but only on the toxins. The difference between the common slope b for several sera tested against P and NP toxins was statistically significant. A difference between the passive protection of mice against P and NP toxins was observed only at very low levels of unitage. These results suggested immunological heterogeneity of B type botulinum toxin. However, for practical purposes, it is not necessary to supplement therapeutic antitoxin with a factor which neutralizes NP toxin.