Intranasal delivery of influenza subunit vaccine formulated with GEM particles as an adjuvant

Abstract

Nasal administration of influenza vaccine has the potential to facilitate influenza control and prevention. However, when administered intranasally (i.n.), commercially available inactivated vaccines only generate systemic and mucosal immune responses if strong adjuvants are used, which are often associated with safety problems. We describe the successful use of a safe adjuvant Gram-positive enhancer matrix (GEM) particles derived from the food-grade bacterium Lactococcus lactis for i.n. vaccination with subunit influenza vaccine in mice. It is shown that simple admixing of the vaccine with the GEM particles results in a strongly enhanced immune response. Already after one booster, the i.n. delivered GEM subunit vaccine resulted in hemagglutination inhibition titers in serum at a level equal to the conventional intramuscular (i.m.) route. Moreover, i.n. immunization with GEM subunit vaccine elicited superior mucosal and Th1 skewed immune responses compared to those induced by i.m. and i.n. administered subunit vaccine alone. In conclusion, GEM particles act as a potent adjuvant for i.n. influenza immunization.

Fig. 1

Subunit antigen-specific HI titers in mice immunized three times. a Comparative analysis of HI titers in different groups, i.e., i.m., i.n., and i.n. + GEM at 0, 28, and 42 days after the first immunization. b Comparative analysis of HI titers between three groups, i.e., i.m., i.n., and i.n. + GEM at 42 days after first immunization. The numbers above the columns indicate the number of responders per group

Fig. 2

Subunit antigen-specific total serum IgG titers in mice immunized three times. a Comparative analysis of total serum IgG titers in different groups, i.e., i.m., i.n., and i.n. + GEM at 0, 28, and 42 days after the first immunization. b Comparative analysis of total serum IgG titers between three groups, i.e., i.m., i.n., and i.n. + GEM at 42 days after first immunization. **p < 0.01

Fig. 3

Subunit antigen-specific total serum IgA titers in mice immunized i.m., i.n., and i.n. + GEM. The numbers above the columns indicate the number of responders per group

Fig. 4

Subunit antigen-specific sIgA titers in nasal (a) and lung lavages (b) of mice immunized i.m., i.n., and i.n. + GEM. The numbers above the columns indicate the number of responders per group

Fig. 5

Subunit antigen-specific serum IgG subtype titers in sera of mice immunized i.m., i.n., and i.n. + GEM. The IgG1 (a), IgG2a (b), and IgG2b (c) titers were determined. *p < 0.05

Fig. 6

The type of the immune response was determined by the cytokine release profile, i.e., IL-4 (a) and IFN-γ (b) in mice immunized. i.m., i.n., and i.n. + GEM. *p < 0.05