Analysis of biomarkers after intramuscular injection of Vaxfectin®-formulated hCMV gB plasmid DNA

Cationic lipids have been used as delivery systems to enhance the performance of vaccines and immunotherapeutics. However, little is known about the effect of administration of cationic lipid-formulated vaccines on gene expression. This study used DNA microarrays (39,000 transcripts) to characterize early changes in gene expression patterns in mouse muscle 1 and 2 days after intramuscular (IM) injection of a hCMV gB plasmid DNA (pDNA) vaccine formulated with the cationic lipid system Vaxfectin®; gene expression profiles were compared to those obtained after IM injection of pDNA in PBS. Analysis of the DNA microarray data indicated that approximately 1% of the represented transcripts were modulated at least 2-fold compared to the PBS samples at both time points. Functional analysis of the modulated genes revealed that transcripts involved in antigen processing and presentation, apoptosis and the Toll-like receptor pathway were significantly enriched. In addition, confirmation of local and systemic modulation of subsets of biomarkers was achieved using Real-Time PCR and Cytometric Bead Assays. Time course and magnitude of cellular infiltration (F4/80+ and CD11b+ cells) to the injection site was changed in response to formulation of hCMVgB pDNA with Vaxfectin®. Since the expression level of the pDNA-encoded transgene in the muscle was not affected by formulation Vaxfectin® mechanism of action is expected to rely primarily on modulation of immune pathways and not on an increase in transfection of the antigen-encoding pDNA. Taken together, these data help explain the Vaxfectin®-dependent robust enhancement of immune responses.