Improved efficacy of DNA vaccination against breast cancer by boosting with the repeat beta-hCG C-terminal peptide carried by mycobacterial heat-shock protein HSP65.

Studies have demonstrated that active-specific immunotherapy has potential for controlling mammary tumor progression. Human chorionic gonadotropin (hCG) is expressed and extremely sensitive, easily detectable and highly correlated with breast cancer. We developed a gene vaccine using a plasmid vector to deliver the six copies of 10-amino acid residues of beta-hCG 109-118 and beta hCG C-terminal 37-amino acid (CTP37). BALB/c female mice were immunized with a combination of pCR-HBc-X6-betahCGCTP37 DNA vaccine and HSP-X6-betahCGCTP37 protein vaccine. pCR-HBc-X6-betahCGCTP37 DNA vaccine were injected intramuscularly three times, on days -46,-25 and -11 and HSP-X6-betahCGCTP37 protein were applied two times, 21 and 14 days before tumor cell challenge. We assessed a combined DNA and protein vaccine for its effect of against murine EMT6 mammary tumor cells. In this study, animals vaccinated DNA vaccination boosting with the repeat beta-hCG C-terminal peptide carried by mycobacterial heat-shock protein HSP65 induced higher avidity antibodies and effectively inhibited the growth of tumor, compared with treatment using DNA alone or BCG priming HSP-X6-betahCGCTP37 protein boosting. The data presented demonstrate that improve immunogenicity of DNA vaccination by boosting with the repeat beta-hCG C-terminal peptide carried by mycobacterial heat-shock protein HSP65, which should prove useful in the development of new DNA vaccine against growth factors for cancer immunotherapy.