title: Activation of the RIG-I pathway during influenza vaccination enhances the germinal center reaction, promotes T follicular helper cell induction, and provides a dose-sparing effect and protective immunity.
abstract: Pattern recognition receptors (PRR) sense certain molecular patterns uniquely expressed by pathogens. Retinoic-acid-inducible gene I (RIG-I) is a cytosolic PRR that senses viral nucleic acids and induces innate immune activation and secretion of type I interferons (IFNs). Here, using influenza vaccine antigens, we investigated the consequences of activating the RIG-I pathway for antigen-specific adaptive immune responses. We found that mice immunized with influenza vaccine antigens coadministered with 5'ppp-double-stranded RNA (dsRNA), a RIG-I ligand, developed robust levels of hemagglutination-inhibiting antibodies, enhanced germinal center reaction, and T follicular helper cell responses. In addition, RIG-I activation enhanced antibody affinity maturation and plasma cell responses in the draining lymph nodes, spleen, and bone marrow and conferred protective immunity against virus challenge. Importantly, activation of the RIG-I pathway was able to reduce the antigen requirement by 10- to 100-fold in inducing optimal influenza-specific cellular and humoral responses, including protective immunity. The effects induced by 5'ppp-dsRNA were significantly dependent on type I IFN and IPS-1 (an adapter protein downstream of the RIG-I pathway) signaling but were independent of the MyD88- and TLR3-mediated pathways. Our results show that activation of the RIG-I-like receptor pathway programs the innate immunity to achieve qualitatively and quantitatively enhanced protective cellular adaptive immune responses even at low antigen doses, and this indicates the potential utility of RIG-I ligands as molecular adjuvants for viral vaccines.
  
  
  OBJECTIVE
  The recently discovered RNA helicase family of RIG-I-like receptors (RLRs) is a critical component of host defense mechanisms responsible for detecting viruses and triggering innate antiviral cytokines that help control viral replication and dissemination. In this study, we show that the RLR pathway can be effectively exploited to enhance adaptive immunity and protective immune memory against viral infection. Our results show that activation of the RIG-I pathway along with influenza vaccination programs the innate immunity to induce qualitatively and quantitatively superior protective adaptive immunity against pandemic influenza viruses. More importantly, RIG-I activation at the time of vaccination allows induction of robust adaptive responses even at low vaccine antigen doses. These results highlight the potential utility of exploiting the RIG-I pathway to enhance viral-vaccine-specific immunity and have broader implications for designing better vaccines in general.
authors.affiliation: Department of Pediatrics and Emory Vaccine Center, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Raveendra R
authors.initials: RR
authors.lastname: Kulkarni
authors.affiliation: Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Mohammed Ata Ur
authors.initials: MA
authors.lastname: Rasheed
authors.affiliation: Department of Pediatrics and Emory Vaccine Center, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Siddhartha Kumar
authors.initials: SK
authors.lastname: Bhaumik
authors.affiliation: Immunology and Pathogenesis Branch, Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: Priya
authors.initials: P
authors.lastname: Ranjan
authors.affiliation: Immunology and Pathogenesis Branch, Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: Weiping
authors.initials: W
authors.lastname: Cao
authors.affiliation: Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Carl
authors.initials: C
authors.lastname: Davis
authors.affiliation: Department of Pediatrics and Emory Vaccine Center, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Krishna
authors.initials: K
authors.lastname: Marisetti
authors.affiliation: Department of Immunology, University of Washington School of Medicine, Seattle, Washington, USA.
authors.forename: Sunil
authors.initials: S
authors.lastname: Thomas
authors.affiliation: Immunology and Pathogenesis Branch, Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: Shivaprakash
authors.initials: S
authors.lastname: Gangappa
authors.affiliation: Immunology and Pathogenesis Branch, Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA murali.kaja@emory.edu ssambhara@cdc.gov.
authors.forename: Suryaprakash
authors.initials: S
authors.lastname: Sambhara
authors.affiliation: Department of Pediatrics and Emory Vaccine Center, Emory University School of Medicine, Atlanta, Georgia, USA ICGEB-Emory Vaccine Center, International Center for Genetic Engineering and Biotechnology, New Delhi, India murali.kaja@emory.edu ssambhara@cdc.gov.
authors.forename: Kaja
authors.initials: K
authors.lastname: Murali-Krishna
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D049109:Cell Proliferation; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D004195:Disease Models, Animal; D018858:Germinal Center / Q000276:immunology*; D006385:Hemagglutination Inhibition Tests; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009976:Orthomyxoviridae Infections / Q000276:immunology / Q000517:prevention & control; D012330:RNA, Double-Stranded / Q000008:administration & dosage*; D015398:Signal Transduction; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000502:physiology; D014611:Vaccination / Q000379:methods
chemical_list: D000276:Adjuvants, Immunologic; D000914:Antibodies, Viral; D007252:Influenza Vaccines; D012330:RNA, Double-Stranded; C503356:Ddx58 protein, mouse; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases