RESUMO
Recombinant Drosophila S2 cells have been used for the expression of many proteins of medical interest. However, membrane-attached glycoproteins, which commonly exhibit lower expression levels compared to soluble proteins, may require special procedures in order to attain high levels of expression. In this study, two S2 cell population enrichment methods (antibiotic and immunomagnetic selection) were evaluated for their ability to enhance expression of the membrane-anchored rabies virus glycoprotein (RVGP). Quantification of RVGP production and determination of its cDNA copy number in transformed cells showed that both enrichment methods increased RVGP expression without significantly affecting its gene copy number. More interestingly, RVGP mRNA levels measured after cycloheximide treatment were poorly correlated with glycoprotein levels. Both enrichment methods enhanced expression of RVGP by recombinant S2 cells, with the highest level of expression achieved using immunomagnetic selection.
RESUMO
The present study shows the humoral and cellular aspects of immune response generated by a recombinant rabies virus glycoprotein (rRVGP) as compared to those generated by viral vector carrying the RNA coding for this protein (RVGP-RNA). The rRVGP was synthesized by stably transfected Drosophila melanogaster Schneider 2 (S2) cells and the RVGP-RNA was carried by a recombinant Semiliki Forest Virus (SFV-RVGP). The data show that protein as well as the RNA vaccine was capable of inducing reasonably acceptable levels of antibodies as compared to the optimized commercial whole virus vaccine. As expected, the RNA vaccine was clearly more effective than the protein vaccines in inducing a cellular immune response, as evaluated by the IgG2a/IgG1 ratio and synthesis of interferon gamma (IFNγ) and interleukin 2 (IL2). Our study supports the importance of vaccine designing taking into consideration the concept of DNA/RNA ability to induce an effective cell immune response.
