Differing Protective Effects of Acellular Pertussis Vaccines in Neonatal and Young Mice in a Murine Model of Respiratory Infection.

Abstract

The protective effects on neonatal (3.5 weeks old) and young mice (7 weeks old) of eight pertussis vaccines prepared from various components at various concentrations were investigated in a murine model of respiratory infection (aerosol challenge model). Neonatal mice were more sensitive than young mice to infection by Bordetella pertussis after aerosol challenge. In young mice with all vaccines, there were significant differences between immunized mice and control mice. The efficacy of vaccines was increased by the inclusion of additional filamentous hemagglutinin (FHA), pertussis toxin (PT), or pertactin (PRN) in the basic vaccine (FHA : PT : PRN, 7 : 2 : 1, w/w). An elevated level of FHA strongly increased the efficacy of the vaccine in young mice. It was, however, more difficult to induce protection against B. pertussis in neonatal mice than in young mice, irrespective of the levels of the various components in the vaccines. Our data suggest that pertussis vaccines are less effective in neonatal mice than in young mice, as assessed by the aerosol challenge model.