In vivo application of RNA leads to induction of specific cytotoxic T lymphocytes and antibodies

To study the efficiency of RNA-based vaccines, RNA coding for the model ant igen beta-galactosidase (beta-gal) was transcribed in vitro from a lacZ gen e flanked by stabilizing Xenopus laevis beta-globin 5' and 3' sequences and was protected from RNase degradation by condensation with the polycationic peptide protamine. The liposome-encapsulated condensed RNA-peptide complex , the condensed RNA-peptide complex without liposome or naked, unprotected RNA, was injected into BALB/c (H-2(d)) mice. All preparations led to protei n expression in the local tissue, activation of L-d-restricted specific cyt otoxic T lymphocytes (CTL) and production of IgG antibodies reactive agains t beta-gal. RNA-triggered CTL were as efficient in the lysis of lacZ-transf ected target cells as CTL triggered by a lacZ-DNA eukaryotic expression vec tor. Immunization with RNA transcribed from a cDNA library from the beta-ga l-expressing cell line P13.1 again led to beta-gal-specific CTL and IgG ind uction. Thus, both naked and protected RNA can be used to elicit a specific immune response in vivo, whereby the protected RNA is stable in vitro for a longer period of time. RNA vaccines can be produced in high amounts and h ave the same major advantages as DNA vaccines but lack the potentially harm ful effect of DNA integration into the genome.