Mutual interactions between DTaP-IPV and Haemophilus influenzae type b (Hib)-conjugated vaccines in laboratory animal models

Potency and/or immunogenicity of three different Haemophilus influenzae typ e b-conjugated vaccines (Hib) and a DTaP-IPV vaccine alone, and their mutua l interactions in DTaP-IPV-Hib combination was tested. In a mouse model, on ly combination of Act-Hib, in which tetanus toroid (TT) was as active as no n-conjugated TT, significantly increased the immunogenicity and potency of TT component of DTaP-IPV vaccine. Also, only combination of Hib-TITER, ire which CRM197 was used as the carrier with DTaP-IPV, increased the potency o f diphtheria toroid (DT) component of DTaP-IPV vaccine significantly. It sh ows that the additive effect of tested Hib vaccines on immunogenicity and/o r potency of TT and DT was mostly due to the existence of TT and CRM197, re spectively, as the carrier in the mentioned Hib vaccines. No difference was shown in inoculation of DTaP-IPV and Hib conjugated vaccines in the same s yringe or at separate sites. DTaP-IPV had dual effects on anti-l-lib capsular polysaccharide (HibCP) res ponses to Hib vaccines in the mouse model. This duality was probably relate d to the carrier B-cell epitopes activity of Hib conjugated vaccines. The immunogenicity of TT component of Act-Hib and Amvax Hib-TT in the guine a pig model was shown and combination of mentioned Hib vaccines with DTaP-I PV, remarkably increased anti-TT antibody responses to the TT component of DTaP-IPV vaccine. These confirmed our results in the mouse model. Using two different protocols to evaluate the guinea pig model for inductio n of anti-HibCP immunity showed that a "long interval" protocol does not ha ve any advantage over the "shorl interval" protocol. Also, combination of D TaP-IPV with Hib vaccines did not have any noticeable effect on anti-HibCP antibodies in the guinea pig model. Taken together, our observations in laboratory animal models may facilitate a better understanding of the mutual interactions between the different an tigen components of a combined vaccine such as DTaP-IPV-Hib vaccine. (C) 19 99 The International Association for Biologicals.