Fig. 3
PrtA immunization increased the antigen-specific immunoglobulin titer and responses. a Sera, nasal washes, saliva, and the BALF were collected from the PrtA1/curdlan-immunized group and the adjuvant control group after three vaccinations (n ≥ 4). Sera and BALF were also collected from mice immunized with PrtA1 protein alone (n = 3). The antigen-specific Ig titer was measured using PrtA-specific ELISA. IgG and IgA were distinguished by an isotype-specific secondary antibody. The reciprocal log2 of the last dilution yielded an OD of 0.2 at 450 nm for sera IgG and 0.1 for the others. *p < 0.05; **p < 0.01; # p < 0.01 compared with PrtA1/curdlan, Student’s t-test. NA, not analyzed. b PrtA-specific IgG subclasses were determined by modified mouse Ig isotyping ELISA (n ≥ 4). **p < 0.01, Student’s t-test. c Sera from immunized mice, but not adjuvant control mice, induced pneumococcal-bound Ig in D39, but not in TIGR4. The sera were pooled from at least four mice in either immunized or adjuvant control group. Rabbit anti-CWPS antisera were used as a control. Bacterial cell-bound IgG was detected using FITC-anti-mouse IgG or FITC-anti-rabbit IgG antibodies and analyzed by flow cytometry