Purpose: Oligodeoxynucleotides containing unmethylated CpG dinucleotides induce innate and adaptive immunity throughToll-like receptor 9 (TLR9). In the present study, we have examined the ability of a novel agonist of TLR9, called immunomodulatory oligonucleotide (IMO), to enhance effects of a HER-2/neu plasmid DNA electroporation/adenovirus (DNA-EP/Ad) vaccine. Experimental Design: BALB/NeuTmice were treated with DNA-EP vaccine alone, IMO alone, or the combination of two agents starting at week 13, when all mice showed mammary neoplasia. Tumor growth and survival were documented. Antibody and CD8 + T-cell responses were determined. Peptide microarray analysis of sera was carried out to identify immunoreactive epitopes. Additionally, microCTand microPET imaging was carried out in an advanced-stage tumor model starting treatment at week 17 in BALB/NeuTmice. Results: The combination of DNA-EP and IMO resulted in significant tumor regression or delay to tumor progression. 2-Deoxy-2-[ 18F]fluoro-D-glucose microPETand microCT imaging of mice showed reduced tumor size in the DNA-EP/IMO combination treatment group. Mice treated with the combination produced greater antibody titers with IgG 2a isotype switch and antibody- dependent cellular cytotoxicity activity than did mice treated with DNA-EP vaccine. An immunogenic B-cell linear epitope, r70, within the HER-2 dimerization domain was identified through microarray analysis. Heterologous DNA-EP/Ad vaccination combined with IMO increased mice survival. Conclusion: The combination of HER-2/neu genetic vaccine and novel agonist of TLR9 had potent antitumor activity associated with antibody isotype switch and antibody-dependent cellular cytotoxicity activities. These results support possible clinical trials of the combination of DNA-EP/Ad-based cancer vaccines and IMO.
ASJC Scopus subject areas
- Cancer Research