Inactivated meningococci and pertussis bacteria are immunogenic and act asmucosal adjuvants for a nasal inactivated influenza virus vaccine

Whole killed meningococci (Nm) and pertussis bacteria (Bp) were tested for mucosal immunogenicity and as mucosal adjuvants for an inactivated influenz a virus vaccine given intranasally to unanaesthetized mice. Virus was given alone, or simply mixed with one of the bacterial preparations, in four dos es at weekly intervals. The virus alone induced low but significant increas es of influenza-specific IgG antibodies iu serum measured by ELISA, whereas IgA responses in serum and saliva were insignificant compared to non-immun ized controls. With Bp or Nm admired, serum Ige and IgA and salivary IgA re sponses to the influenza virus were substantially augmented (P < 0.005). Ho wever, this adjuvant effect of the bacterial preparations was not significa nt for responses in the intestine as measured by antibodies in faeces. Anti body responses to Bp itself but not to Nm, were inhibited by the admixture of the virus vaccine. Moreover, the pertussis preparation induced salivary antibodies which cross-reacted with Nm. Whole-cell bacteria with inherent s trong mucosal immunogenicity may also possess mucosal adjuvanticity for adm ired particulate antigens which are weakly immunogenic by the nasal route. (C) 2000 Elsevier Science Ltd, All rights reserved.