Essential immunogens in human pertussis: the role of fimbriae.

After the decline in pertussis vaccination in Britain from the mid-1970s, isolates possessing agglutinogen 2 (types 1.2.3 and 1.2) have replaced type 1.3 as the predominant serotypes. These agglutinogen-2 strains are fimbriate, and their predominance in non-vaccinated communities may result from enhanced attachment to mucosal cells. However, type 1.3 cells are not fimbriate; and, because agglutinogen 3 is essential in fully effective whole-cell vaccine, a subcellular vaccine prepared from fimbriae alone (agglutinogen 2) would probably be inadequate. The mouse can be killed with type 1 strains, devoid of agglutinogens 2 and 3, and is therefore not a suitable model for ensuring that pertussis vaccine contains these essential immunogens.