The effect of Pickering emulsion adjuvants on the immune efficacy of the COVID-19 polypeptide vaccine

Pickering emulsions were prepared by phacoemulsification in an ice water bath with squalene as the oil phase and an aluminum adjuvant as the particle stabilizer.The effects of formulation and process conditions on the size and distribution of the Pickering emulsions were investigated.Pickering emulsions prepared under the optimal prescription and process conditions were mixed with a peptide antigen to obtain a peptide vaccine.The optimal prescription and process condition of the Pickering emulsion is as follows:squalene as the oil phase,ultra-pure water as the water phase with 5 mg/mL aluminum adjuvant,and an ultrasonication time of 4 min at 200 W power.BALB/c mice were immunized with the peptide vaccine,and the ability of the Pickering emulsion as an immunological adjuvant to improve the efficacy of the peptide vaccine was evaluated.Under optimal conditions,a Pickering emulsion with a small particle size(430.8 nm),uniform distribution(polydispersion index of 16.9%),and zeta potential of 31.5 mV,was obtained.Immunological results showed that the serum specific antibody level in the vaccinated group reached 1×104 after three immunizations.The proportion of CD4+T cells and CD4/CD8 cells was significantly higher(P<0.05)in the vaccinated groups than the blank control group.Further,cytokine(TNF-𝛼)secretion decreased in the aluminum adjuvant and Pickering emulsion groups but increased in the Freund’s adjuvant group.All three vaccinated groups of mice exhibited low but detectable levels of IFN-𝛾secretion.

Hyaluronan is a natural and effective immunological adjuvant for protein-based vaccines

One of the main goals of vaccine research is the development of adjuvants that can enhance immune responses and are both safe and biocompatible.We explored the application of the natural polymer hyaluronan(HA)as a promising immunological adjuvant for protein-based vaccines.Chemical conjugation of HA to antigens strongly increased their immunogenicity,reduced booster requirements,and allowed antigen dose sparing.HA-based bioconjugates stimulated robust and long-lasting humoral responses without the addition of other immunostimulatory compounds and proved highly efficient when compared to other adjuvants.Due to its intrinsic biocompatibility,HA allowed the exploitation of different injection routes and did not induce inflammation at the inoculation site.This polymer promoted rapid translocation of the antigen to draining lymph nodes,thus facilitating encounters with antigen-presenting cells.Overall,HA can be regarded as an effective and biocompatible adjuvant to be exploited for the design of a wide variety of vaccines.