Antigen delivery by filamentous bacteriophage fd displaying an anti‐DEC‐205 single‐chain variable fragment confers adjuvanticity by triggering a TLR9‐mediated immune response

• Published in: EMBO molecular medicine 2015-07, Vol.7 (7), p.973-988
• Main Authors: Sartorius, Rossella, D'Apice, Luciana, Trovato, Maria, Cuccaro, Fausta, Costa, Valerio, De Leo, Maria Giovanna, Marzullo, Vincenzo Manuel, Biondo, Carmelo, D'Auria, Sabato, De Matteis, Maria Antonietta, Ciccodicola, Alfredo, De Berardinis, Piergiuseppe
• Format: Article
• Language: English
• Subjects: Adjuvants, Immunologic - metabolism; Animals; antigen delivery; Antigens - immunology; Antigens - metabolism; Antigens, CD - immunology; Antigens, CD - metabolism; CD8-Positive T-Lymphocytes - immunology; Cell Surface Display Techniques; Cells, Cultured; DEC‐205; dendritic cells; Dendritic Cells - immunology; Drug Carriers; EMBO19; EMBO23; filamentous bacteriophage; Gene Expression Profiling; Immunity, Innate; Inovirus - genetics; Lectins, C-Type - immunology; Lectins, C-Type - metabolism; Mice, Inbred C57BL; Minor Histocompatibility Antigens; Receptors, Cell Surface - immunology; Receptors, Cell Surface - metabolism; Research Article; Single-Chain Antibodies - immunology; Single-Chain Antibodies - metabolism; TLR9; Toll-Like Receptor 9 - metabolism
• ISSN: 1757-4676; 1757-4684
• DOI: 10.15252/emmm.201404525

Filamentous bacteriophage fd particles delivering antigenic determinants via DEC‐205 (fdsc‐αDEC) represent a powerful delivery system that induces CD8 + T‐cell responses even when administered in the absence of adjuvants or maturation stimuli for dendritic cells. In order to investigate the mechanisms of this activity, RNA‐Sequencing of fd‐pulsed dendritic cells was performed. A significant differential expression of genes involved in innate immunity, co‐stimulation and cytokine production was observed. In agreement with these findings, we demonstrate that induction of proinflammatory cytokines and type I interferon by fdsc‐αDEC was MYD88 mediated and TLR9 dependent. We also found that fdsc‐αDEC is delivered into LAMP‐1‐positive compartments and co‐localizes with TLR9. Thus, phage particles containing a single‐strand DNA genome rich in CpG motifs delivered via DEC‐205 are able to intercept and trigger the active TLR9 innate immune receptor into late endosome/lysosomes and to enhance the immunogenicity of the displayed antigenic determinants. These findings make fd bacteriophage a valuable tool for immunization without administering exogenous adjuvants. Synopsis Filamentous fd bacteriophages engineered to display antigens and targeted to dendritic cells via DEC‐205 activate both innate and adaptive immune responses and are an attractive immunization system avoiding administration of exogenous adjuvants. Antigens displayed on anti‐DEC‐205‐targeted bacteriophages are efficiently cross‐presented by DCs. fd virions targeted to DCs via DEC‐205 are delivered to endolysosomal compartments where they co‐localize with active TLR9. Transcriptome analysis using RNA‐Seq of bacteriophage‐pulsed DCs elucidates the signature induced by fd anti‐DEC‐205‐based vaccine and showed the up‐regulation of gene pathways involved in the innate and adaptive immune responses. Production of pro‐inflammatory cytokines and type I interferon is induced in DC‐targeted bacteriophage fd particles displaying anti‐DEC‐205 scFv and abolished in MyD88 −/− and Tlr9 −/− mice. fdsc‐αDEC bacteriophages combine adjuvanticity and ability to activate specific immune responses, and may thus represent a relevant option in vaccinology. Graphical Abstract Filamentous fd bacteriophages engineered to display antigens and targeted to dendritic cells via DEC‐205 activate both innate and adaptive immune responses and are an attractive immunization system avoiding administration of exogenous adjuvants.