To optimize
polynucleotide vaccinations for protective antitumor immunity we used a self-replicating
RNA vaccine in which Semliki Forest virus replicase drives
RNA expression of the lacZ gene coding for
beta-galactosidase as model
tumor-associated
antigen (TAA). This was compared with replicase-deficient control
RNA and with lacZ
DNA plasmids with respect to gene expression in vitro and in vivo and for vaccination using the mouse ear pinna as an optimal immunization site. In vitro, the highest expression was observed with self-replicating
RNA. Gene expression following pinna inoculation of either non-replicating
DNA plasmids or self-replicating
RNA was similar, lasting for 2-3 weeks. Higher antibody responses were obtained with
RNA than with
DNA. beta-Gal
peptide specific CTL memory responses to lacZ
DNA or
RNA lasted for more than 6 weeks while respective responses induced by lacZ-transfected
tumor cells lasted for only 2 weeks. To achieve a protective response against lacZ
tumor cells with self-replicating
RNA about a 100-fold lower dose of
polynucleotide was sufficient in comparison to
DNA. The extent of protective antitumor immunity not only depended on the gene dose used for vaccination, but also on the aggressiveness of the lacZ-transfected
tumor line used for challenge. In comparison to lacZ-transfected
tumor cells as
vaccines, polynucleotide vaccination also demonstrated superiority with regard to cross-protection. Protective antitumor immunity could be strongly increased upon co-inoculation of lacZ
DNA with
IL-2 DNA or
IL-12 RNA.
IL-2 DNA, but not
IL-12 RNA, also augmented the CTL response while
IL-12 RNA, but not
IL-2 DNA, reduced the antibody response. These results demonstrate efficient protective antitumor immunity after intra-pinna lacZ TAA
polynucleotide vaccination and show additional immunomodulatory effects by co-administration of
cytokine polynucleotides.