Design, characterization and preclinical efficacy of a cationic lipid adjuvant for influenza split vaccine.

We prepared a series of cationic lipid vesicles comprising a cationic cholesterol derivative, DC-Chol with or without a neutral phospholipid, DOPC or DOPE. The vesicles were tested for their ability to bind and adjuvant split inactivated influenza vaccines. We found that DC-Chol-containing liposomes are capable to strongly bind influenza vaccine antigens upon simple mixing with the vaccine. The resulting formulations induced robust anti-influenza immune responses both after s.c. and i.n. administration in BALB/c mice while neutral Cholesterol/DOPC liposomes displayed virtually no stable antigen binding and no adjuvant effect. The parenteral adjuvant effect of DC-Chol on trivalent split influenza vaccines was then confirmed in outbred mice and monkeys. Among the most potent formulations tested, a simple mixture of the vaccine with a microfluidized dispersion of DC-Chol in an aqueous buffer is being considered for further development to produce an improved influenza vaccine.