Recognition of the microbiota by Nod2 contributes to the oral adjuvant activity of cholera toxin through the induction of interleukin‐1β

Abstract

The role of symbiotic bacteria in the development of antigen-specific immunity remains poorly understood. Previous studies showed that sensing of symbiotic bacteria by nucleotide-binding oligomerization domaincontaining protein 2 (Nod2) regulates antibody responses in response to nasal immunization with antigen and cholera toxin (CT). In this study, we examined the role of the microbiota in the adjuvant activity of CT induced after oral immunization with antigen. Germ-free (GF) mice showed impaired production of antibody responses and T-cell-specific cytokines after oral immunization when compared with that observed in conventionally raised mice. Similar to GF mice, Nod2-deficient mice showed reduced humoral responses upon oral immunization with antigen and CT. Treatment with CT enhanced the production of interleukin-1b (IL-1b), but not tumor necrosis factor-a or IL-12p40, induced by stimulation of dendritic cells with muramyl dipeptide, the Nod2 ligand. Mechanistically, the enhanced production of IL-1b induced by muramyl dipeptide and CT stimulation required Nod2 and was mediated by both increased synthesis of pro-IL-1b and caspase-1 activation. Furthermore, antigen-specific antibody and cytokine responses induced by CT were impaired in orally immunized IL-1b-deficient mice. Collectively, our results indicate that Nod2 stimulation by symbiotic bacteria contributes to optimal CT-mediated antigen-specific oral vaccination through the induction of IL-1b production.

Understanding Host Immunity and the Gut Microbiota Inspires the New Development of Vaccines and Adjuvants

“…The adjuvanticity of CT was not abrogated in MyD88 −/− mouse, suggesting that the effect of CT is not dependent on TLR signaling. Furthermore, the necessity of NOD2 was also observed in the context of oral CT administration [87]. This report further supports the importance of the microbe-NOD2 axis and indicates that IL-1β is required for the adjuvant activity of CT. IL-1β produced by DCs dictates the differentiation of CD4 + T cells into Tfh cells [88]; in turn, Tfh cells support the proliferation and activation of B cells through germinal center reactions [89].…”

Immunomodulation by the Commensal Microbiome During Immune-Targeted Interventions: Focus on Cancer Immune Checkpoint Inhibitor Therapy and Vaccination

“…The outcomes of ICI and immunization are also influenced by MAMPs, including flagellin, unmethylated CpG DNA, peptidoglycan, muramyl dipeptide, and polysaccharides (6,83,126,129). MAMPs directly and indirectly modulate activation and differentiation of immune cells (236)(237)(238), and synthetic MAMPs are already used as exogenous adjuvants during immunization to activate the immune system.…”

“…Similarly, endogenous MAMPs may also promote T cell function as costimulatory molecules (241)(242)(243)(244)(245). B and T cell functions are also indirectly influenced by MAMP-mediated modulation of APC maturation, leading to altered interactions and production of cytokines and chemokines (5,6,83,129,246,247). By understanding the role endogenous MAMPs play in outcomes of ICI and vaccination, we may be able to identify key MAMPs and host pathways that promote immunotherapy response, which could lead to development of novel vaccine adjuvants or ICI co-therapies.…”

“…Other studies suggest the microbiota are required to supply immune receptor ligands for the activity of mucosal adjuvants. Two independent groups have employed immunization with albumin and cholera toxin (CTx) to demonstrate that germ-free or antibiotic-treated mice have decreased antibody responses, which are rescued by supplementation with microbial molecules ( 128 , 129 , 132 ). Both groups demonstrated that CTx potentiates immune receptor signaling, which require the presence of microbial molecules for full signaling activation in response to CTx.…”

Vaccine Hyporesponse Induced By Individual Antibiotic Treatment In Mice And Non-Human Primates Is Diminished Upon Recovery Of The Gut Microbiome

“…Studies have suggested some correlation between microbiome and vaccine responses (e.g. inflammation and microbial secondary bile acids) (2,22,(25)(26)(27)(28), but they have yet to focus on microbiome perturbation with recovery dynamics in mice or non-human primates (NHPs). Here we begin to address this knowledge gap by characterizing the dynamics of vaccine hyporesponse associated with antibiotic-mediated microbiome perturbation and recovery in mice as well as non-human primates.…”