Composition comprises a virus-like particle, which is built from more molecules of viral capsid proteins and contains a RNA-interference-inducing molecule. Independent claims are included for: (1) producing the composition, comprising assembling the viral capsid protein to virus-like protein in the presence of RNA-interference-inducing molecules； (2) introducing RNA-interference-inducing molecule into a target cell, comprising assembling the viral capsid protein to virus-like protein in the presence of the RNA-interference-inducing molecule, contacting the virus-like protein loaded with the RNA-interference-inducing molecules with the target cells under the condition in which an absorption of the RNA-interference-inducing molecules takes place into the target cells； (3) down regulation of at least a gene in the target cell, comprising providing the composition, contacting the composition with the target cell under the condition in which an absorption of the RNA-interference-inducing molecule takes place into the target cell； (4) a test kit for introducing the RNA-interference-inducing molecule into the target cells, comprising the composition； (5) a pharmaceutical composition comprising virus-like protein and RNA-interference-inducing molecule and optionally standard buffer, auxiliary materials, additives and/or diluting agents； (6) a modified polyoma JC virus-VP1 capsid protein comprising nuclear localization signal so that coding of nucleic acid or virus-like protein composition containing the modified capsid protein, takes place； (7) a virus-like protein composition, where the virus-like protein contains an immunostimulatory nucleic acid optionally in combination with polypeptide- or peptide-immunogen, an aptamer or a small interfering DNA molecule； and (8) a polyoma JC virus-VP1 capsid protein at which at least a heterologous binding partner e.g. a polypeptide, is bound over the amino acid residue lys-60 and/or lys-164. ACTIVITY : None given. MECHANISM OF ACTION
