Poke Weed Mitogen Requires Toll-Like Receptor Ligands for Proliferative Activity in Human and Murine B Lymphocytes

Poke weed mitogen (PWM), a lectin purified from Phytolacca americana is frequently used as a B cell-specific stimulus to trigger proliferation and immunoglobulin secretion. In the present study we investigated the mechanisms underlying the B cell stimulatory capacity of PWM. Strikingly, we observed that highly purified PWM preparations failed to induce B cell proliferation. By contrast, commercially available PWM preparations with B cell activity contained Toll-like receptor (TLR) ligands such as TLR2-active lipoproteins, lipopolysaccharide and DNA of bacterial origin. We show that these microbial substances contribute to the stimulatory activity of PWM. Additional experimental data highlight the capacity of PWM to enable B cell activation by immunostimulatory DNA. Based on these findings we propose that the lectin sensitizes B cells for TLR stimulation as described for B cell receptor ligation and that B cell mitogenicity of PWM preparations results from synergistic activity of the poke weed lectin and microbial TLR ligands present in the PWM preparations

Driving change in dtap batch release testing

The complexity of vaccine manufacturing has raised the need to drive standardization and quality control requirements as well as batch release of vaccines. The purpose of release testing is to ensure that efficacy and safety of the vaccine product are maintained in all batches. Classical testing includes challenge experiments in animals that provide proof of vaccine potency and identify subpotent vaccines. However, novel concepts such as “consistency testing” question the continued need for in vivo experiments and propose to implement rigorous QC for lot-to-lot consistency testing with other methods at an earlier stage. Please click Download on the upper right corner to see the full abstract

A 5-year look-back at the notification and management of vaccine supply shortages in Germany

Background: Unavailability of vaccines endangers the overall goal to protect individuals and whole populations against infections. Methods: The German notification system includes the publication of vaccine supply shortages reported by marketing authorisation holders (MAH), information on the availability of alternative vaccine products, guidance for physicians providing vaccinations and an unavailability reporting tool to monitor regional distribution issues. Aim: This study provides a retrospective analysis of supply issues and measures in the context of European and global vaccine supply constraints. Results: between October 2015 and December 2020, the 250 notifications concerned all types of vaccines (54 products). Most shortages were caused by increased demand associated with immigration in Germany in 2015 and 2016, new or extended vaccine recommendations, increased awareness, or changes in global immunisation programmes. Shortages of a duration up to 30 days were mitigated using existing storage capacities. Longer shortages, triggered by high demand on a national level, were mitigated using alternative products and re-allocation; in a few cases, vaccines were imported. However, for long lasting supply shortages associated with increased global demand, often occurring in combination with manufacturing issues, few compensatory mechanisms were available. Nevertheless, only few critical incidents were identified: (i) shortage of hexavalent vaccines endangering neonatal immunisation programmes in 2015;(ii) distribution issues with influenza vaccines in 2018; and (iii) unmet demand for pneumococcal and influenza vaccines during the coronavirus disease (COVID)-19 pandemic. Conclusion: Vaccine product shortages in Germany resemble those present in neighbouring EU states and often reflect increased global demand not matched by manufacturing capacities.Peer Reviewe

Impact of rifaximin on the frequency and characteristics of spontaneous bacterial peritonitis in patients with liver cirrhosis and ascites

BACKGROUND: Rifaximin is a non-absorbable antibiotic used to prevent relapses of hepatic encephalopathy which may also be a candidate for prophylaxis of spontaneous bacterial peritonitis (SBP). AIM: To detect the impact of rifaximin on the occurrence and characteristics of SBP. METHODS: We prospectively studied all hospitalized patients that underwent a diagnostic paracentesis in our department from March 2012 to April 2013 for SBP and recorded all clinical data including type of SBP prophylaxis, prior use of rifaximin, concomitant complications of cirrhosis, as well as laboratory results and bacteriological findings. Patients were divided into the following three groups: no antibiotic prophylaxis, prophylaxis with rifaximin or with systemically absorbed antibiotic prophylaxis. RESULTS: Our study cohort comprised 152 patients with advanced liver cirrhosis, 32 of whom developed SBP during the study period. As expected, our study groups differed regarding a history of hepatic encephalopathy and SBP before inclusion into the study. None of the 17 patients on systemic antibiotic prophylaxis developed SBP while 8/27 patients on rifaximin and 24/108 without prophylaxis had SBP (p = 0.02 and p = 0.04 versus systemic antibiotics, respectively). In general, episodes of SBP were similar for patients treated with rifaximin and those without any prophylaxis. However, Escherichia coli and enterococci were dominant in the ascites of patients without any prophylaxis, while mostly klebsiella species were recovered from the ascites samples in the rifaximin group. CONCLUSION: Rifaximin pretreatment did not lead to a reduction of SBP occurrence in hospitalized patients with advanced liver disease. However, the bacterial species causing SBP were changed by rifaximin

T cell-independent, TLR-induced IL-12p70 production in primary human monocytes

IL-12p70 is a key cytokine for the induction of Th1 immune responses. IL-12p70 production in myeloid cells is thought to be strictly controlled by T cell help. In this work we demonstrate that primary human monocytes can produce IL-12p70 in the absence of T cell help. We show that human monocytes express TLR4 and TLR8 but lack TLR3 and TLR7 even after preincubation with type I IFN. Simultaneous stimulation of TLR4 and TLR8 induced IL-12p70 in primary human monocytes. IL-12p70 production in peripheral blood myeloid dendritic cells required combined stimulation of TLR7/8 ligands together with TLR4 or with TLR3 ligands. In the presence of T cell-derived IL-4, but not IFN-gamma, stimulation with TLR7/8 ligands was sufficient to stimulate IL-12p70 production. In monocytes, type I IFN was required but not sufficient to costimulate IL-12p70 induction by TLR8 ligation. Furthermore, TLR8 ligation inhibited LPS-induced IL-10 in monocytes, and LPS alone gained the ability to stimulate IL-12p70 in monocytes when the IL-10 receptor was blocked. Together, these results demonstrate that monocytes are licensed to synthesize IL-12p70 through type I IFN provided via the Toll/IL-1R domain-containing adaptor inducing IFN-beta pathway and the inhibition of IL-10, both provided by combined stimulation with TLR4 and TLR8 ligands, triggering a potent Th1 response before T cell help is established

TLR1/2, TLR7, and TLR9 Signals Directly Activate Human Peripheral Blood Naive and Memory B Cell Subsets to Produce Cytokines, Chemokines, and Hematopoietic Growth Factors

Recently, it has been reported that using multiple signals, murine and human B cells secrete several cytokines with pro-inflammatory and immunoregulatory properties. We present the first comprehensive analysis of 24 cytokines, chemokines, and hematopoietic growth factors production by purified human peripheral blood B cells (CD19+), and naive (CD19+CD27-) and memory (CD19+CD27+) B cells in response to direct and exclusive signaling provided by toll-like receptor (TLR) ligands Pam3CSK (TLR1/TLR2), Imiquimod (TLR7), and GpG-ODN2006 (TLR9). All three TLR ligands stimulated B cells (CD19+) to produce cytokines IL-1α, IL-1β, IL-6, TNF-α, IL-13, and IL-10, and chemokines MIP-1α, MIP-1β, MCP-1, IP-10, and IL-8. However, GM-CSF and G-CSF production was predominantly induced by TLR2 agonist. Most cytokines/chemokines/hematopoietic growth factors were predominantly or exclusively produced by memory B cells, and in general, TLR2 signal was more powerful than signal provided viaTLR7 and TLR9. No significant secretion of eotaxin, IFN-α, IFN-γ, IL-2, IL-3, IL-4, IL-5, IL-7, IL-15, IL-17, IL-12p40, IL-12p70, and TNF-β (lymphotoxin) was observed. These data demonstrate that human B cells can be directly activated viaTLR1/TLR2, TLR7, and TLR9 to induce secretion of cytokines, chemokines, and hematopoietic growth factors and suggest a role of B cells in immune response against microbial pathogenesis and immune homeostasis

Carnauba wax nanoparticles enhance strong systemic and mucosal cellular and humoral immune responses to HIV-gp140 antigen

Induction of humoral responses to HIV at mucosal compartments without inflammation is important for vaccine design. We developed charged wax nanoparticles that efficiently adsorb protein antigens and are internalized by DC in the absence of inflammation. HIV-gp140-adsorbed nanoparticles induced stronger in vitro T-cell proliferation responses than antigen alone. Such responses were greatly enhanced when antigen was co-adsorbed with TLR ligands. Immunogenicity studies in mice showed that intradermal vaccination with HIV-gp140 antigen-adsorbed nanoparticles induced high levels of specific IgG. Importantly, intranasal immunization with HIV-gp140-adsorbed nanoparticles greatly enhanced serum and vaginal IgG and IgA responses. Our results show that HIV-gp140-carrying wax nanoparticles can induce strong cellular/humoral immune responses without inflammation and may be of potential use as effective mucosal adjuvants for HIV vaccine candidates

Decreased Toll-like receptor 8 expression and lower TNF-alpha synthesis in infants with acute RSV infection

<p>Abstract</p> <p>Background</p> <p>Toll-like receptors (TLRs) are part of the innate immune system, able to recognize pathogen-associated molecular patterns and activate immune system upon pathogen challenge. Respiratory syncytial virus (RSV) is a RNA virus particularly detrimental in infancy. It could cause severe lower respiratory tract disease and recurrent infections related to inadequate development of anti-viral immunity. The reason could be inadequate multiple TLRs engagement, including TLR8 in recognition of single-stranded viral RNA and diminished synthesis of inflammatory mediators due to a lower expression.</p> <p>Methods</p> <p>Intracellular TLR8 expression in peripheral blood monocytes from RSV-infected infants was profiled and compared to healthy adults and age matched controls. Whether the observed difference in TLR8 expression is a transitory effect, infants in convalescent phase (4-6 weeks later) were retested. Specific TLR8-mediated TNF-α production in monocytes during an acute and convalescent phase was analyzed.</p> <p>Results</p> <p>RSV-infected and healthy infants had lower percentage of TLR8-expressing monocytes than healthy adults whereas decreased of TLR8 protein levels were detected only for RSV-infected infant group. Lower protein levels of TLR8 in monocytes from RSV-infected infants, compared to healthy infants, negatively correlated with respiratory frequency and resulted in lower TNF-α synthesis upon a specific TLR8 stimulation. In the convalescent phase, levels of TLR8 increased, accompanied by increased TNF-α synthesis compared to acute infection.</p> <p>Conclusions</p> <p>Lower TLR8 expression observed in monocytes, during an acute RSV infection, might have a dampening impact on early anti-viral cytokine production necessary to control RSV replication, and subsequently initiate an adaptive Th1 type immune response leading to severe disease in infected infants.</p