Chitosan based nanoformulation expressing miR-155 as a promising adjuvant to enhance Th1-biased immune responses

MiR-155 could act as a key modulator of different aspects of immune system including Th1 responses. In this study, we designed chitosan nanoparticles containing miR-155-expressing plasmid and explored their effects as an adjuvant to enhance Th1 responses for potential future application against intracellular pathogens. Nanoparticles were formulated by complex coacervation method and characterized for physicochemical and functional characteristics. Transfection efficiency in Raw 264.7 cells, effects on miR-155 target genes and NO production were evaluated. The prepared nanoparticles were co-administered as an adjuvant with ovalbumin to immunize mice and finally production of IFN-γ and IL-4 were measured by ELISA in splenocyte recall responses. The prepared nanoparticles had the mean size of 244 nm and zeta potential of +17 mV, respectively. Electrophoresis analysis indicated the high capability of nanoparticles to protect the plasmid from DNaseI degradation. Furthermore, nanoparticles showed an appropriate transfection efficiency in Raw 264.7 cells and could downregulate the expression of miR-155 target genes and also upregulate NO production. In vivo immunization examinations revealed successful shift of T cell responses toward Th1. Our data suggests the high potential of chitosan nanoparticles containing miR-155-expressing plasmid as an adjuvant for significantly enhanced Th1-biased immune responses upon immunization with a given antigen. [Display omitted] •MiR-155 CNPs showed a high transfection efficiency in Raw 264.7 macrophages.•MiR-155 CNPs significantly decreased miR-155 target genes expression.•MiR-155 CNPs induced NO production in the transfected Raw 264.7 macrophages.•MiR-155 CNPs induced a Th1-biased cellular immune response in the immunized mice.