Complexes of RNA and cationic peptides for transfection and for immunostimulation

A method of inducing or enhancing an innate immune response in a subject in need thereof, comprising administering to the subject a complexed ribonucleic acid (RNA) comprising at least one RNA molecule complexed with one or more oligopeptides, wherein the at least one RNA molecule is not covalently bound to the one or more oligopeptides, wherein the nitrogen/phosphate ratio (N/P-ratio) of the RNA to the one or more oligopeptides is in the range of 0.75-25, and wherein the oligopeptide is 8 to 15 amino acids in length and comprises the following formula:

• (Arg)l;(Lys)m;(His )n;(Orn)o;(Xaa)x (formula I)
• wherein
• l+m+n+o+x=8-15, and
• l, m, n or o independently of each other is any number selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, provided that the overall content of Arg, Lys, His and Orn represents at least 50% of all amino acids of the oligopeptide;
• and
• Xaa is any amino acid selected from native or non-native amino acids except Arg, Lys, His or Orn;
• and
• x is any number selected from 0, 1, 2, 3, 4, 5, 6, 7, or 8, provided, that the overall content of Xaa does not exceed 50% of all amino acids of the oligopeptide.