TLR9-Activating DNA Up-Regulates ZAP70 via Sustained PKB Induction in IgM+ B Cells

Inactivated influenza vaccines have two formulations, whole- and split-virion types; however, how differential formulations impact their booster effects remain unknown. In this study, we demonstrate that whole-virion vaccines recall two waves of Ab responses, early T cell–independent (TI) and late T cell–dependent responses, whereas split-virion vaccines elicit the late T cell–dependent response only. Notably, higher-affinity Abs with improved neutralizing activity are provided from the early TI response, which emphasizes the important contribution of the formulation-dependent response in the protective immunity. Moreover, we show that the early TI response completely requires B cell–intrinsic TLR7 signaling, which can be delivered through viral RNAs within whole-virion vaccine. Thus, our results indicate that TLR agonists in whole-virion type improve recall Ab responses by directly targeting memory B cells, a finding with important implications for vaccine strategies aimed at the prompt recall of high-affinity neutralizing Abs.

Section: Discussionsupporting

confidence: 75%

Whole-Virion Influenza Vaccine Recalls an Early Burst of High-Affinity Memory B Cell Response through TLR Signaling

Onodera

Hosono

Odagiri

et al. 2016

“…Previously non CpG ODNs with phosphorothioate backbones but not with phosphodiester backbones were shown to be capable of triggering intracellular signaling pathways and inducing interleukin synthesis (33, 34). It has also been reported that phosphorothioate modified synthetic ODN’s may penetrate into cytoplasm and carry out various biological activities by binding to cytoplasmic proteins (35).…”

Section: Discussionmentioning

confidence: 99%

B Cells Produce Type 1 IFNs in Response to the TLR9 Agonist CpG-A Conjugated to Cationic Lipids

Akkaya

Miozzo

et al. 2017

B cells express the innate receptor, toll-like receptor 9 (TLR9), which signals in response to unmethylated CpG sequences in microbial DNA. Of the two major classes of CpG-containing oligonucleotides, CpG-A appears restricted to inducing type 1 interferon (type 1 IFN) in innate immune cells and CpG-B to activating B cells to proliferate and produce antibodies and inflammatory cytokines. Although CpGs are candidates for adjuvants to boost innate and adaptive immunity, our understanding of the effect of CpG-A and CpG-B on B cell responses is incomplete. Here we show that both CpG-B and CpG-A activated B cells in vitro to proliferate, secrete antibodies and IL-6 and that neither CpG-B nor CpG-A alone induced type 1 IFN production. However, when incorporated into the cationic lipid, DOTAP, CpG-A, but not CpG-B induced a type 1 IFN response in B cells in vitro and in vivo. We provide evidence that differences in the function of CpG-A and CpG-B may be related to their intracellular trafficking in B cells. These findings fill an important gap in our understanding of the B cell response to CpGs with implications for the use of CpG-A and CpG-B as immunomodulators.

“…LPS-mediated B cell proliferation is defective in mice lacking the p85a regulatory subunit of PI3K (42), and mTOR inhibition blocks both BCR and LPS-mediated proliferation and S6 kinase activation (43). In addition, the PI3K/Akt pathway has also been shown to play a critical role in CpG-mediated human B cell activation (44). Our findings indicate that mTOR was activated downstream of TLR7 in naive B cells, and its activation was markedly impaired in tolerant B cells (Fig.…”

Section: Discussionmentioning

confidence: 99%

Type I IFN Receptor and the B Cell Antigen Receptor Regulate TLR7 Responses via Distinct Molecular Mechanisms

Poovassery

Bishop

2012

Toll-like receptor 7 (TLR7) signals to B cells are critically involved in the innate immune response to microbes, as well as pathogenesis of autoimmune diseases, but the molecular mechanisms that normally regulate these responses are incompletely understood. We previously reported that repeated stimulation through TLR7 induces a state of hyporesponsiveness (TLR tolerance) in both human and mouse B cells, characterized by marked inhibition of particular signaling pathways. BCR signals prevent and overcome TLR7 tolerance. Because optimal responses to TLR7 in B cells require type I IFN, we investigated whether BCR-mediated effects on TLR7 tolerance are mediated by type I IFN receptor (IFNAR) signals. Surprisingly, although BCR-mediated reversal of TLR7 tolerance was IFNAR independent, IFNAR signals alone also blocked TLR7 tolerance, despite enhancing TLR7 expression. Both BCR and IFNAR signals restored the phosphorylation of the transcriptional regulator c-Jun, but only BCR signals blocked the tolerance-mediated inhibition of JNK. Both BCR and IFNAR-mediated regulation was dependent on activation of the PI3K/Akt/mammalian target of rapamycin signaling pathway, indicating a central role for this axis in integrating TLR7, BCR, and IFNAR signals in B cells. These new findings reveal distinct and overlapping signaling mechanisms used by BCR and IFNAR in the regulation of TLR7 tolerance and activation.