IgG mediated protection elicited by △A146 Ply against Streptococcus pneumoniae infections in murine models / 中华微生物学和免疫学杂志

ABSTRACT

Objective To evaluate whether immunization with △A146 Ply could confer protections against pneumococcal infections in murine models and to reveal the possible role of △A146 Ply-specific IgG in the protection elicited.MethodsBALB/c mice were immunized intraperitoneally with △A146 Ply or PBS plus alum.Fourteen days after the third immunization,mice were intranasally challenged with serotype 14 and 19F Streptococcus pneumoniae.Three days after inoculation,lungs were removed from mice and homogenized in PBS,followed by plated on red cell plates.Viable bacteria were counted after overnight incubation.As to the sepsis models,vaccinated mice were challenged intraperitoneally with different dosage bacteria of D39 and serotype 3 strain.The numbers of CFU log10 were compared by Mann Whitney U test and survival rates were analyzed using log-rank test.Passive protection was used to evaluate the role of △A146 Ply-specific IgG in the protection against otherwise lethal infection resulted from D39.Results ELISA analysis demonstrated higher titer specific antibody responses to △A146 Ply was produced after 3 times immunization.Mice boosted twice with △A146 Ply survived significantly longer than that for mice boosted once with △A146 Ply in Alum adjuvant,which were significantly longer than that of control group.Immunization with △A146 Ply was effective in reducing the numbers of pneumococcal strain 31614(serotype 14) and 31693(serotype 19F),which resulted in 50-and 20-fold decreases in bacterial load in the lungs respectively when compared to control protein-immunized mice.60% of vaccinated mice survived the infection with pneumococcal D39 of 1200 CFU.60% protection was achieved when mice intraperitoneally infected with D39 and received △A146 Ply-specific IgG,whereas no mice survived the infection when they were passively administered with △A146 Ply-specific IgG depleted antisera.Conclusion Immunization with △A146 Ply could confer protection against pneumococcal infections,and protection elicited was mediated by △A146 Ply-specific IgG.