Purification of serotype 2 fimbriae of Bordetella pertussis and their identification as a mouse protective antigen.

Fimbriae were removed from Bordetella pertussis by mechanical shearing and purified by successive precipitations with ammonium sulfate, pH 6.0 phosphate buffer, and magnesium chloride. Electron microscopy showed the purified fimbriae to be long filamentous structures (5 nm in diameter) which aggregated into bundles at pH 6.0. Sodium dodecyl sulfate gel electrophoresis of the purified fimbriae gave a single protein subunit with a molecular weight of 22,000. The purified fimbriae did not have hemagglutinating activity when assayed with a variety of erythrocytes and were shown to be antigenically and structurally distinct from the filamentous hemagglutinin of B. pertussis. The purified fimbriae were identified as serotype 2 agglutinogens as antibody to the purified fimbriae agglutinated B. pertussis strains serotyped as 1.2.4, 1.2.3, or 1.2.3.6, but did not agglutinate serotypes 1.3.6. Immunization of mice with the purified fimbriae (14 micrograms) protected them from a lethal respiratory infection with strain 18323 (agglutinogen serotype 1.2.3.4.6) or with strain 432 (serotype 1.3.6). Immunization of mice with purified fimbriae containing 0.02% LPF also protected them from a lethal intracerebral infection with 18323. The ED50 was about 13 micrograms. Fimbriae containing less than 0.005% LPF did not protect mice from intracerebral challenge.