Fig 2. Immunization of mice with f88M2e2-16 phages results in robust anti-M2e specific serum IgG responses.

(A-D) Groups of female BALB/c mice (n = 10 per group) were intraperitoneally vaccinated with antigens in the presence of incomplete Freund’s adjuvant via the intraperitoneal route. Purified phages were administered at 10¹⁰ tetracycline transducing units (f88M2e2-16 and f88ctr groups). As a positive control, one group was immunized with 10 μg M2eHBc per vaccination. A PBS plus adjuvant was included as a negative control. Blood was collected 10 days after priming and each boost injection and serum was prepared and tested in ELISA. (A) Anti-f88 total IgG titration following priming and boosting. (B) Anti-human consensus M2e total IgG following priming and boosting. (C) Anti-human consensus M2e IgG1 and (D) IgG2a endpoint titration following priming and boosting. Endpoint serum IgG titers after the third boost were determined from BALB/c mice that had been immunized with 10¹⁰ tetracycline transducing units of f88ctr, 10¹⁰ tetracycline transducing units f88M2e2-16 or 10 μg of avian M2e-HBc using ELISA plates coated with M2e peptides from different influenza A virus strains: (E) M2e from A/swine/Ontario/42729A/01 (sOnM2e), (F) M2e from A/chicken/HongKong/258/1997 (cHKM2e), (G) M2e from A/chicken/Vietnam/36/2004 (cVNM2e). In A-D error bars represent standard deviations.