United Immunity, Co., Ltd., a biotech company developing pullulan-based Myeloid Targeting Platform™, with its partners from the University of Tokyo, Kyoto University, Nagasaki University and Aichi Cancer Center announced today the publication of preclinical data demonstrating that pullulan nanoparticle (PNP, shown as PNG in the article) actively delivers the spike (S) protein of SARS-CoV-2 to antigen-presenting medullary macrophages through the selective binding to the C-type lectin receptor SIGN-R1 (mouse equivalent of human DC-SIGN). PNP vaccination strongly enhanced the induction of specific CD8+ T cells and thereby prevented viral infection. The study was published in the journal npj Vaccines on September 18.
In a K18-hACE2 mouse model of SARS-CoV-2 infection, PNP:RBD vaccine significantly decreased the viral load and prolonged the survival in a CD8+ T cell- and B cell-dependent manner. T cell receptor (TCR) repertoire analysis revealed that although the vaccine induced T cells at various frequencies, low frequency specific T cells mainly promoted virus clearance. Thus, the induction of specific CD8+ T cells that respond quickly to viral infection, even at low frequencies, is important for vaccine efficacy and can be achieved by SIGN-R1+ medullary macrophage-targeted antigen delivery.
Dr. Naozumi Harada, co-author and Chairman of United Immunity commented “we foresee that our PNP technology as well as our corresponding pullulan-coated lipid nanoparticle will be applicable to vaccines against a wide variety of infectious diseases”. PDF