Infant mouse model of E. coli diarrhoea: clinical protection induced by vaccination of the mothers.
Protection of infant mice against experimental E. coli B41 diarrhoea by immunization of the mothers with homologous E. coli strain was studied. The influence of the number, dose, route and moment of vaccination(s) on protection, measured by the reduced mortality rate of infant mice during the 15 days following oral challenge, was tested. The highest dose of vaccine, namely 10(8) formalin-killed E. coli by parenteral routes or 3 X 10(9) live E. coli by peroral (p.o.) route resulted in the best effect, whatever the immunization procedure used. A single vaccination of the mothers mainly delayed death without marked reduction of the mortality rate. Subcutaneous (s.c.) immunization with 10(8) formalin-killed E. coli was nevertheless more efficient than p.o. vaccination with 3 X 10(8) live E. coli. Equal levels of protection were observed when the above s.c. vaccination occurred either 15 days before the onset of gestation or on the 8th day or 15th day. In contrast, the p.o. immunization resulted in no effect when done on the 15th day of gestation. Great improvement in protection was obtained with two vaccinations, when priming occurred 15 days before the onset of gestation and boosting on the 8th day, except with two combined p.o. vaccinations with 3 X 10(8) live E. coli. Both dosages of priming and boosting seemed to matter. Peroral, subcutaneous or intraperitoneal priming with about 10(8) E. coli resulted in nearly equal effects, when boosting occurred subcutaneously with 10(8) killed E. coli. However, i.p. priming probably resulted in some non-specific effect, as shown by the slower clinical evolution of the controls. A tenfold dosage increase in p.o. priming alone led to the best protective effect observed when boosting was done three weeks after priming. The occurrence of s.c. boosting one week later, namely four weeks after priming, markedly improved protection with every route tested, and more particularly with the s.c. one. However, complete protection was never obtained. Protective effect was mostly transmitted after birth by the colostrum and the milk of the immune mothers, as demonstrated by cross-fostering experiments. Using the best immunization procedures, variability of the model was studied, by repeating experiments several times. Clinical evolution of the controls was very similar from one experiment to another, whatever the route and the moment of immunizations. In contrast, vaccinated groups showed variations which increased with time, especially on and after seven days following inoculation. Clinical evolution of individual litters belonging to the same experimental group indicated that each mother did not equally respond to the vaccination.
D000818:Animals; D000831:Animals, Newborn; D001428:Bacterial Vaccines / Q000008:administration & dosage; D003967:Diarrhea / Q000276:immunology / Q000517:prevention & control*; D004195:Disease Models, Animal; D004306:Dose-Response Relationship, Immunologic; D004926:Escherichia coli / Q000276:immunology; D004927:Escherichia coli Infections / Q000276:immunology / Q000517:prevention & control*; D005260:Female; D007112:Immunity, Maternally-Acquired; D007117:Immunization, Secondary; D051379:Mice; D011247:Pregnancy; D013997:Time Factors; D014611:Vaccination / Q000379:methods
D001428:Bacterial Vaccines