Vaccine adjuvant is conferred on the substance that helps to enhance
antigen-specific immune response. Here we investigated the disintegration characteristics and
immunotherapy potency of an emulsified delivery system comprising bioresorbable
polymer poly(
ethylene glycol)-
polylactide (
PEG-PLA),
phosphate buffer saline (PBS), and metabolizable oil
squalane.
PEG-PLA-stabilized oil-in-water
emulsions show good stability at 4 °C and at room temperature. At 37 °C,
squalane/
PEG-PLA/PBS
emulsion with oil/aqueous weight ratio of 7/3 (denominated PELA73) was stable for 6 weeks without phase separation. As
PEG-PLA being degraded, 30% of free oil at the surface layer and 10% of water at the bottom disassociated from the PELA73
emulsion were found after 3 months. A MALDI-TOF MS study directly on the DIOS plate enables us to identify low molecular weight components released during degradation. Our results confirm the loss of PLA moiety of the emulsifier
PEG-PLA directly affected the stability of
PEG-PLA-stabilized
emulsion, leading to
emulsion disintegration and
squalane/water phase separation. As adjuvant for
cancer immunotherapeutic use, an HPV16 E7
peptide antigen formulated with PELA73 plus immunostimulatory CpG molecules could strongly enhance
antigen-specific T-cell responses as well as anti-
tumor ability with respected to non-formulated or
Alum-formulated
peptide. Accordingly, these advances may be a potential immunoregulatory strategy in manipulating the immune responses induced by
tumor-associated
antigens.