Figure 2. Route of immunization with M2e-MAPs determines systemic and respiratory tract responses.

BALB/c mice were immunized with K2 and adjuvants or adjuvants alone either intranasally (i.n.) or into the tailbase (s.c.) as described above. (A) M2e-specific Abs in the bronchio-alveolar lavage (BAL) fluid after third vaccination were determined by ELISA on M2e-peptide (n = 3 mice/group). (B) Sera were collected 3–4 weeks after the indicated number of immunizations and measured by ELISA for binding to M2e-peptide and HeLa-M2 cells. (C) Mice were euthanized after third vaccination and cells from lungs and bone marrow (BM) seeded onto ELISPOT plates coated with M2e-peptide. Plates were developed with anti-mouse IgG or IgA. Results from 4–6 mice from 2 independent experiments are expressed as mean counts (± SEM). (D) Groups of mice were challenged with influenza virus A/X31 (1000 TCID₅₀/5 µL) and infectious virus in the lungs determined 5 days after challenge.