Features of the humoral immune response when using protein immobilized on the surface of nano- and microparticles based on poly(lactic acid)

The study is aimed at evaluating the influence of composition and size of micro- and nanoparticles (MPs and NPs) on the immunogenicity of protein antigen associated with them. For comparative analysis, MPs and NPs based on poly(lactic acid) (PLA) and block copolymer of poly(ethylene glycol) with poly(lactic acid) (PEG-b-PLA) were obtained. Recombinant human beta2-microglobulin fusion protein with superfolder green fluorescent protein (β2M-sfGFP) was used for covalent modification of all types of polymer particles. Immobilization of the model protein β2M-sfGFP was carried out on the surface of the particles through the reaction of activated esters with the amino groups of the protein. Immunization of mice using complex antigen (β2M-sfGFP protein immobilized on the surface of MPs and NPs of different compositions) was carried out in four steps. Immunogenicity was assessed by the level of specific antibodies to sfGFP using enzyme-linked immunoassay. The results showed a significant increase in antibody levels in the control groups, which were immunized with a mixture of model protein and particles of different nature and sizes, compared to the experimental groups, which were immunized with conjugates of the corresponding particles with model protein. In the experimental groups, the highest number of specific antibodies was detected in the case of immunization of mice with the conjugate of protein and PLA or PEG-b-PLA-based NPs. The introduction of PEG block into the PLA composition did not significantly affect the immunogenicity of the protein, while the particle size was of significant importance. PLA- or PEG-b-PLA-based NPs showed higher immunogenicity compared to MPs of the same compositions, which can be used for practical purposes to develop vaccines (NP-protein) or ” trapping systems” (MP-protein) that bind infiltrating viruses.