NLRC4 Inflammasome-Driven Immunogenicity of a Recombinant MVA Mucosal Vaccine Encoding Flagellin

Abstract

Bacterial flagellin enhances innate and adaptive immune responses and is considered a promising adjuvant for the development of vaccines against infectious diseases and cancer. Antigen-presenting cells recognize flagellin with the extracellular TLR5 and the intracellular NLRC4 inflammasome-mediated pathway. The detailed cooperation of these innate pathways in the induction of the adaptive immune response following intranasal (i.n.) administration of a recombinant modified vaccinia virus Ankara (rMVA) vaccine encoding flagellin (rMVA-flagellin) is not known. rMVA-flagellin induced enhanced secretion of mucosal IL-1β and TNF-α resulting in elevated CTL and IgG2c antibody responses. Importantly, mucosal IgA responses were also significantly enhanced in both bronchoalveolar (BAL) and intestinal lavages accompanied by the increased migration of CD8+ T cells to the mesenteric lymph nodes (MLN). Nlrc4−/− rMVA-flagellin-immunized mice failed to enhance pulmonary CTL responses, IgG2c was lower, and IgA levels in the BAL or intestinal lavages were similar as those of control mice. Our results show the favorable adjuvant effect of rMVA-flagellin in the lung as well as the intestinal mucosa following i.n. administration with NLRC4 as the essential driver of this promising mucosal vaccine concept.

Combating COVID-19: MVA Vector Vaccines Applied to the Respiratory Tract as Promising Approach Toward Protective Immunity in the Lung

“…These findings are in agreement with observations of others identifying ovalbumin-specific IgA antibodies in the bronchoalveolar lavage fluid in mice intranasally immunized with MVA expressing ovalbumin ( 15 ). Others showed in non-human primates that aerosol immunization with recombinant MVA induced specific IgA in the genital tract ( 16 , 17 ) or T cells specific for the transgene in the lung ( 18 ).…”

The Role of Toll-Like Receptors in Oncotherapy

“…Pyroptosis is a proinflammatory reaction that induces programmed cell death and recognizes flagellin components to initiate the process. Researchers have found that flagellin triggers caspase 1-dependent activation of pyroptosis, which is mediated by TLR5 and the neuronal apoptosis inhibitory protein 5 (Naip5)/NLR family CARD domain-containing protein 4 (NLRC4) signaling pathway, to suppress breast cancer cell growth 10 . Additionally, the tumor suppressor p53 also modulates TLR signaling in cancer cells.…”

Inflammasome-Mediated Immunogenicity of Clinical and Experimental Vaccine Adjuvants

“…Vault NPs Large cytoplasmic ribonucleoprotein particles NLRP3 [32] Chitosan Biodegradable cationic polymer obtained from chitin NLRP3 [10,[33][34][35][36] Silica particles Biocompatible particles NLRP3 [37,38] Gold NPs Gold nanoparticles NLRP3 [39] Flagellin Used as recombinant protein, or encoded in virus replicon or DNA plasmid NLRC4 [40][41][42][43][44] DNA vaccines DNA plasmids or Aim2 encoded in vector as immunopotentiator AIM2 [45][46][47] CTB Cholera toxin B from Vibrio cholerae, added to an Ag, or as a DNA vaccine NLRP3, Pyrin [48][49][50] oxPAPC Oxidized 1-palmitoyl-2-arachidonoyl-snglycero-3-phosphorylcholine (generated during tissue damage)…”

“…Flagellin has also been assessed for adjuvanticity after administration of a recombinant modified vaccinia virus Ankara (rMVA) vaccine encoding the flagellin gene. Immunisation with rMVA-flagellin induced enhanced secretion of mucosal IL-1β and TNF-α, resulting in elevated T-cell and antibody responses, which were diminished in NLRC4 −/− mice [ 43 ]. Similarly, incorporating flagellin into the replicon of an alphavirus enhanced IgG1 and IgG2a/c titres, indicating an enhancement of Th1 and Th2 type responses.…”