Non-replicating vaccines, such as those based on recombinant proteins, require adjuvants and delivery systems, which have thus far depended on mimicking pathogen danger signals and strong pro-inflammatory responses. In search of a safer and more efficacious alternative, we tested whether vaccinations with influenza recombinant hemagglutinin (HA) mixed with a novel vegetable oil in water emulsion adjuvant (Natural Immune-enhancing Delivery System, NIDS), based on the immune-enhancing synergy of vitamins A and E and a catechin, could protect against intra-nasal challenge with live influenza virus. Vaccinations of inbred Brag Albino strain c (BALB/c) mice, with HA mixed with NIDS compared to other adjuvants, i.e., a squalene oil in water emulsion (Sq. oil), and the Toll Like Receptor 3 (TLR3) agonist Poly (I:C), induced significantly lower select innate pro-inflammatory responses in serum, but induced significantly higher adaptive antibody and splenic T Helper 1 (TH1) or TH2, but not TH17, responses. Vaccinations with NIDS protected against infection, as measured by clinical scores, lung viral loads, and serum hemagglutination inhibition titers. The NIDS exhibited a strong dose sparing effect and the adjuvant action of NIDS was intact in the outbred CD1 mice. Importantly, vaccinations with the Sq. oil, but not NIDS, induced a significantly higher Serum Amyloid P component, an acute phase reactant secreted by hepatocytes, and total serum IgE. Thus, the NIDS may be used as a clinically safer and more efficacious vaccine adjuvant against influenza, and potentially other infectious diseases.
Keywords: adjuvant; catechin; flavonoid; immunity; influenza; natural; vaccine; vitamin A; vitamin E.