Vaccine shortages are a major obstacle to influenza pandemic preparedness. Increasing vaccine efficiency provides a potentially effective way to overcome this problem. Specifically, using single-dose immunization to induce protective immunity is an attractive approach to emergency/massive vaccination. In this report, we propose a novel nanoemulsion comprised of the bioresorbable polymer, SpanR85, and squalene forming a ready-to-use adjuvant, called PELC. After formulation with PELC, inactivated H5N1 virus was intramuscularly administered to mice via a single injection. The data demonstrate that inactivated virus containing 0.5 μg hemagglutinin (HA) and formulated with PELC induced more potent antigen-specific antibodies, hemagglutination inhibition, and virus neutralization than non-adjuvanted inactivated virus containing 5 μg HA. In addition, T-cell proliferative responses, as well as interferon-γ (IFN-γ) and interleukin-4 (IL-4) secretion were significantly enhanced after immunization with PELC-adjuvanted inactivated virus. These results indicate that PELC can be used for effective single-dose immunization and could thus play an important role in influenza pandemic preparedness.
