Developing efficient and safe adjuvants for use in human vaccines remains both a challenge and a necessity. Past approaches have been largely empirical and generally used a single type of adjuvant, ...such as aluminium salts or emulsions. However, new vaccine targets often require the induction of well-defined cell-mediated responses in addition to antibodies, and thus new immunostimulants are required. Recent advances in basic immunology have elucidated how early innate immune signals can shape subsequent adaptive responses and this, coupled with improvements in biochemical techniques, has led to the design and development of more specific and focused adjuvants. In this Review, I discuss the research that has made it possible for vaccinologists to now be able to choose between a large panel of adjuvants, which potentially can act synergistically, and combine them in formulations that are specifically adapted to each target and to the relevant correlate(s) of protection.
In this study, enzyme-assisted extraction was used to isolate functional polysaccharides from Korean ginseng (Panax ginseng Meyer) and the physicochemical and biological properties of the extracted ...polysaccharides were investigated, comparing with those from traditional hot-water extraction (FGWP). In macrophages, their effects on cytokines production could be ordered as FGEP-CA ≥ FGEP-A > FGEP-C > FGWP, suggesting that FGEP-CA (combined cellulase- and α-amylase-extracted polysaccharide) is a potent immunostimulator. In addition, enzymatic digestion led to differences in the monosaccharide profile of the extract. FGWP mainly consisted of rhamnose, arabinose, galactose, galacturonic acid, and glucose in molar percentages of 1.8:10.1:9.2:17.8:60.6, whereas FGEP-CA was 3.2:11.4:16.5:22.3:45.8, respectively, suggesting that enzyme-assisted extraction of ginseng polysaccharides produces a higher proportion of pectin polysaccharides. The HPLC profile of FGEP-CA also showed lower and more heterogeneous molecular weights than FGWP did. In cyclophosphamide-induced immunosuppressed mice, FGEP-CA administration ameliorated decreased spleen and thymus indices (200 mg/kg), lymphocyte proliferation, natural killer cell activity, leukocyte counts, and the serum cytokines, interleukin-2, interleukin-6, and interferon-γ (100 and 200 mg/kg). These results suggest that enzyme-assisted extraction using cellulase and α-amylase is an effective method for the preparation of functional polysaccharides from fresh Korean ginseng, and FGEP-CA could be utilized as a potential immune-stimulatory agent.
The anti-tuberculosis-vaccine Bacillus Calmette-Guérin (BCG) is the most widely used vaccine in the world. In addition to its effects against tuberculosis, BCG vaccination also induces non-specific ...beneficial effects against certain forms of malignancy and against infections with unrelated pathogens. It has been recently proposed that the non-specific effects of BCG are mediated through epigenetic reprogramming of monocytes, a process called trained immunity. In the present study we demonstrate that autophagy contributes to trained immunity induced by BCG. Pharmacologic inhibition of autophagy blocked trained immunity induced in vitro by stimuli such as β-glucans or BCG. Single nucleotide polymorphisms (SNPs) in the autophagy genes ATG2B (rs3759601) and ATG5 (rs2245214) influenced both the in vitro and in vivo training effect of BCG upon restimulation with unrelated bacterial or fungal stimuli. Furthermore, pharmacologic or genetic inhibition of autophagy blocked epigenetic reprogramming of monocytes at the level of H3K4 trimethylation. Finally, we demonstrate that rs3759601 in ATG2B correlates with progression and recurrence of bladder cancer after BCG intravesical instillation therapy. These findings identify a key role of autophagy for the nonspecific protective effects of BCG.
Oligosaccharides and dietary fibres are non-digestible food ingredients that preferentially stimulate the growth of prebiotic Bifidobacterium and other lactic acid bacteria in the gastro-intestinal ...tract. Xylooligosaccharides (XOS) provide a plethora of health benefits and can be incorporated into several functional foods. In the recent times, there has been an over emphasis on the microbial conversion of agroresidues into various value added products. Xylan, the major hemicellulosic component of lignocellulosic materials (LCMs), represents an important structural component of plant biomass in agricultural residues and could be a potent bioresource for XOS. On an industrial scale, XOS can be produced by chemical, enzymatic or chemo-enzymatic hydrolysis of LCMs. Chemical methods generate XOS with a broad degree of polymerization (DP), while enzymatic processes will be beneficial for the manufacture of food grade and pharmaceutically important XOS. Xylooligomers exert several health benefits, and therefore, have been considered to provide relief from several ailments. This review provides a brief on production, purification and structural characterization of XOS and their health benefits.
Toll-like receptors (TLRs) are vital elements of the mammalian immune system that function by recognizing pathogen-associated molecular patterns (PAMPs), bridging innate and adaptive immunity. They ...have become a prominent therapeutic target for the treatment of infectious diseases, cancer, and allergies, with many TLR agonists currently in clinical trials or approved as immunostimulants. Numerous studies have shown that conjugation of TLR agonists to other molecules can beneficially influence their potency, toxicity, pharmacokinetics, or function. The functional properties of TLR agonist conjugates, however, are highly dependent on the ligation strategy employed. Here, we review the chemical structural requirements for effective functional TLR agonist conjugation. In addition, we provide similar analysis for those that have yet to be conjugated. Moreover, we discuss applications of covalent TLR agonist conjugation and their implications for clinical use.
As part of the accelerated development of vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we report a dose-finding and adjuvant justification study of SCB-2019, a ...protein subunit vaccine candidate containing a stabilised trimeric form of the spike (S)-protein (S-Trimer) combined with two different adjuvants.
Our study is a phase 1, randomised, double-blind placebo-controlled trial at a specialised clinical trials centre in Australia. We enrolled healthy adult volunteers in two age groups: younger adults (aged 18–54 years) and older adults (aged 55–75 years). Participants were randomly allocated either vaccine or placebo using a list prepared by the study funder. Participants were to receive two doses of SCB-2019 (either 3 μg, 9 μg, or 30 μg) or a placebo (0·9% NaCl) 21 days apart. SCB-2019 either had no adjuvant (S-Trimer protein alone) or was adjuvanted with AS03 or CpG/Alum. The assigned treatment was administered in opaque syringes to maintain masking of assignments. Reactogenicity was assessed for 7 days after each vaccination. Humoral responses were measured as SCB-2019 binding IgG antibodies and ACE2-competitive blocking IgG antibodies by ELISA and as neutralising antibodies by wild-type SARS-CoV-2 microneutralisation assay. Cellular responses to pooled S-protein peptides were measured by flow-cytometric intracellular cytokine staining. This trial is registered with ClinicalTrials.gov, NCT04405908; this is an interim analysis and the study is continuing.
Between June 19 and Sept 23, 2020, 151 volunteers were enrolled; three people withdrew, two for personal reasons and one with an unrelated serious adverse event (pituitary adenoma). 148 participants had at least 4 weeks of follow-up after dose two and were included in this analysis (database lock, Oct 23, 2020). Vaccination was well tolerated, with two grade 3 solicited adverse events (pain in 9 μg AS03-adjuvanted and 9 μg CpG/Alum-adjuvanted groups). Most local adverse events were mild injection-site pain, and local events were more frequent with SCB-2019 formulations containing AS03 adjuvant (44–69%) than with those containing CpG/Alum adjuvant (6–44%) or no adjuvant (3–13%). Systemic adverse events were more frequent in younger adults (38%) than in older adults (17%) after the first dose but increased to similar levels in both age groups after the second dose (30% in older and 34% in younger adults). SCB-2019 with no adjuvant elicited minimal immune responses (three seroconversions by day 50), but SCB-2019 with fixed doses of either AS03 or CpG/Alum adjuvants induced high titres and seroconversion rates of binding and neutralising antibodies in both younger and older adults (anti-SCB-2019 IgG antibody geometric mean titres at day 36 were 1567–4452 with AS03 and 174–2440 with CpG/Alum). Titres in all AS03 dose groups and the CpG/Alum 30 μg group were higher than were those recorded in a panel of convalescent serum samples from patients with COVID-19. Both adjuvanted SCB-2019 formulations elicited T-helper-1-biased CD4+ T-cell responses.
The SCB-2019 vaccine, comprising S-Trimer protein formulated with either AS03 or CpG/Alum adjuvants, elicited robust humoral and cellular immune responses against SARS-CoV-2, with high viral neutralising activity. Both adjuvanted vaccine formulations were well tolerated and are suitable for further clinical development.
Clover Biopharmaceuticals and the Coalition for Epidemic Preparedness Innovations.
Many immunostimulants act as vaccine adjuvants via activation of the innate immune system, although in many cases it is unclear which specific molecules contribute to the stimulatory activity. QS-21 ...is a defined, highly purified, and soluble saponin adjuvant currently used in licensed and exploratory vaccines, including vaccines against malaria, cancer, and HIV-1. However, little is known about the mechanisms of cellular activation induced by QS-21. We observed QS-21 to elicit caspase-1-dependent IL-1β and IL-18 release in antigen-presenting cells such as macrophages and dendritic cells when co-stimulated with the TLR4-agonist adjuvant monophosphoryl lipid A. Furthermore, our data suggest that the ASC-NLRP3 inflammasome is responsible for QS-21-induced IL-1β/IL-18 release. At higher concentrations, QS-21 induced macrophage and dendritic cell death in a caspase-1-, ASC-, and NLRP3-independent manner, whereas the presence of cholesterol rescued cell viability. A nanoparticulate adjuvant that contains QS-21 as part of a heterogeneous mixture of saponins also induced IL-1β in an NLRP3-dependent manner. Interestingly, despite the role NLRP3 plays for cellular activation in vitro, NLRP3-deficient mice immunized with HIV-1 gp120 and QS-21 showed significantly higher levels of Th1 and Th2 antigen-specific T cell responses and increased IgG1 and IgG2c compared with wild type controls. Thus, we have identified QS-21 as a nonparticulate single molecular saponin that activates the NLRP3 inflammasome, but this signaling pathway may contribute to decreased antigen-specific responses in vivo.
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•Two polysaccharides of MMP-2 and MMP-3 are fractioned from marine clam M. meretrix.•MMP-2 and MMP-3 belong to gulcomannan and gulcogalactan homologs.•Their chemical structures are ...α(1→4)–glucan branched with Man or Gal.•MMP-2 and MMP-3 can stimulate splenocyte proliferation and cytokines secretion.•The bioactivity perhaps is correlated to their peculiar structures.
The marine clam Meretrix meretrix was subjected to extraction with a combined procedure of water decoction, ethanol precipitation, and deproteinization to yield a water-soluble polysaccharide coded as MMP. The product was fractionated with DEAE-52 cellulose and resulted in two soluble fractions designated as MMP-2 and -3. The structures of the fractions were determined by chemical and physicochemical analysis, and their immunomodulation activities and cytokine production were assayed by lymphopoiesis. Results showed that MMP-2 and -3 were glucomannan and glucogalactan homologs, respectively. They possess average molecular masses of 272 and 257 kDa, respectively, and were elucidated as branched copolymers, elaborated as α(1→4)–glucan branching with mannose or galactose via β(1→6)-linkage. Bioassay indicated that MMP-2 and -3 held moderate potentials in restoring immune function because they augment splenocyte proliferation and enhance the cytokine secretion of lymphocytes dose-dependently. We speculated that their bioactivities are closely correlated with their peculiar structures.
Monophosphoryl lipid A (MPLA) species, including MPL (a trade name of GlaxoSmithKline) and GLA (a trade name of Immune Design, a subsidiary of Merck), are widely used as an adjuvant in vaccines, ...allergy drugs, and immunotherapy to boost the immune response. Even though MPLA is a derivative of lipopolysaccharide (LPS), a component of the outer membrane of Gram-negative bacteria, bacterial strains producing MPLA have not been found in nature nor engineered. In fact, MPLA generation involves expensive and laborious procedures based on synthetic routes or chemical transformation of precursors isolated from Gram-negative bacteria. Here, we report the engineering of an Escherichia coli strain for in situ production and accumulation of MPLA. Furthermore, we establish a succinct method for purifying MPLA from the engineered E. coli strain. We show that the purified MPLA (named EcML) stimulates the mouse immune system to generate antigen-specific IgG antibodies similarly to commercially available MPLA, but with a dramatically reduced manufacturing time and cost. Our system, employing the first engineered E. coli strain that directly produces the adjuvant EcML, could transform the current standard of industrial MPLA production.
•Monophosphoryl lipid A (MPLA) is a safe and effective adjuvant.•Engineering lipopolysaccharide biosynthetic pathway enables to produce MPLA.•Employing lipid A 1-phosphatase from Aquifex dephosphorylates lipid A in vivo.•The succinct purification method of MPLA (EcML) is developed.•EcML purified from the engineered strain effectively functions as an adjuvant.
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