- Fim2 and Fim3 from Bordetella pertussis only protect against the infection from their respective producer strains

CASTUMA C.; GRAIEB A; GAILLARD ME,; BOTTERO D.; HOZBOR D.

Baltimore - EEUU

Simposio; Ninth International Bordetella Symposium.; 2010

Fimbriae are one of the B. pertussis virulence factors involved in the attachment of bacteria to host tissues. B. pertussis produces two serologically distinct Fimbriae, Fim2 and Fim3 whose expression is regulated by the bvg locus and also by a phase variation mechanism so that any strain may produce Fim2, Fim3 or Fim2 and Fim3. The protective properties of Fimbriae are well known since their inclusion in acellular vaccines greatly increases the efficacy of the formulations. Most of the data collected all around the world indicate that Fim2 strains prevail in unvaccinated populations while they are largely displaced by Fim3 strains when vaccination is introduced . These results could suggest a strain antigenic divergence driven by the differential selective pressures  from Fim2 and Fim3 according to their immunogenic properties. The complexity of this scenario is further increased by the possibility of in vivo phase variation (4). Despite the many epidemiological data, little is known about the functional properties of both serotypes.The aim of the present work is to purify the Fim2 and Fim3 proteins and to perform functional assays with them in order to further characterize their immunoprotective properties.PURIFICATION OF FIM2 AND FIM3 consist of precipitation with polyethyleneglycol , treatment with urea, heat and  new precipitation with polyethyleneglycol. Functional assays were performed by intranasal challenge in the Mouse Model.In agreement with reports published many years ago, the results presented here show the protective role of both Fimbria serotypes . The co purification of Fimbria with LPS seems to enhance the protein protective capacity as seen when comparing TLR4 competent mice and TLR4 deficient mice (C3H/HeJ ). On the other hand, the cross protection assay reveals that the immunization with each fimbria serotype decreases the number of recovered bacteria only against the challenge with the producer strain. This last result is in contrast with that reported by Robinson et al 1987 in which Fim 3 protected against the infection from all serotypes. The authors purified Fim3, but not Fim 2, by the same method used in these studies, which is known to also extract LPS.