Microbial communities are found throughout the biosphere, from human guts to glaciers, from soil to activated sludge. Understanding the statistical properties of such diverse communities can pave the way to elucidate the common mechanisms ...Multiple ecological forces act together to shape the composition of microbial communities. Phyloecology approaches—which combine phylogenetic relationships between species with community ecology—have the potential to disentangle such forces but are often ...

The α7 nicotinic acetylcholine receptor (α7nAChR) is central to the anti-inflammatory function of the vagus nerve in a physiological mechanism termed the inflammatory reflex. Studies on the inflammatory reflex have been instrumental for the current development of the field of bioelectronic medicine. An independent investigation of the biological role of αB-crystallin (HspB5), the most abundant gene transcript present in active multiple sclerosis lesions in human brains, also led to α7nAChR. Induction of experimental autoimmune encephalomyelitis (EAE) in HspB5-/- mice results in greater paralytic signs, increased levels of proinflammatory cytokines, and T-lymphocyte activation relative to wild-type animals. Administration of HspB5 was therapeutic in animal models of multiple sclerosis, retinal and cardiac ischemia, and stroke. Structure-activity studies established that residues 73-92 were as potent as the parent protein, but only when it formed amyloid fibrils. Amyloid fibrils and small heat shock proteins (sHsps) selectively bound α7nAChR on peritoneal macrophages (MΦs) and B lymphocytes, converting the MΦs to an immune suppressive phenotype and mobilizing the migration of both cell types from the peritoneum to secondary lymph organs. Here, we review multiple aspects of this work, which may be of interest for developing future therapeutic approaches for multiple sclerosis and other disorders.

Significance The identification of α7 nicotinic acetylcholine receptor (α7 NAChR) as the principal receptor for amyloid fibrils and small heat shock proteins clarifies their mechanism of immune suppression. The discovery of the receptor allows previous experiments using amyloid fibrils to be interpreted based on the extensive body of literature detailing the NAChR signaling pathway. In addition, the data further support the realization that amyloid fibrils are immune suppressive, which may be an important factor in neurodegenerative diseases. The demonstration that NAChR agonists are effective in limiting ischemia and autoimmunity emphasizes that the α7-specific partial agonists, which failed in clinical trials for Alzheimer’s disease and schizophrenia, could be reconsidered as therapeutics for a spectrum of inflammatory indications.

Although the accumulation of amyloidogenic proteins in neuroinflammatory conditions is generally considered pathologic, in a murine model of multiple sclerosis, amyloid-forming fibrils, comprised of hexapeptides, are anti-inflammatory. Whether these molecules modulate systemic inflammatory conditions remains unknown. We hypothesized that an amylin hexapeptide that forms fibrils can attenuate the systemic inflammatory response in a murine model of sepsis. To test this hypothesis, mice were pre-treated with either vehicle or amylin hexapeptide (20 μg) at 12 hours and 6 hours prior to intraperitoneal (i.p.) lipopolysaccharide (LPS, 20 mg/kg) administration. Illness severity and survival were monitored every 6 hours for 3 days. Levels of pro- (IL-6, TNF-α, IFN-γ) and anti-inflammatory (IL-10) cytokines were measured via ELISA at 1, 3, 6, 12, and 24 hours after LPS (i.p.). As a metric of lung injury, pulmonary artery endothelial cell (PAEC) barrier function was tested 24 hours after LPS administration by comparing lung wet-to-dry ratios, Evan's blue dye (EBD) extravasation, lung histology and caspase-3 activity. Compared to controls, pretreatment with amylin hexapeptide significantly reduced mortality (p<0.05 at 72 h), illness severity (p<0.05), and pro-inflammatory cytokine levels, while IL-10 levels were elevated (p<0.05). Amylin pretreatment attenuated LPS-induced lung injury, as demonstrated by decreased lung water and caspase-3 activity (p<0.05, versus PBS). Hence, in a murine model of systemic inflammation, pretreatment with amylin hexapeptide reduced mortality, disease severity, and preserved lung barrier function. Amylin hexapeptide may represent a novel therapeutic tool to mitigate sepsis severity and lung injury.

Amyloid hexapeptide molecules are effective in the treatment of the murine model of neuroinflammation, known as experimental autoimmune encephalomyelitis (EAE). Efficacy however differs between two inbred mouse strains, C57BL/6J (B6) and C57BL/10SnJ (B10). Amyloid hexapeptide treatments improved the clinical outcomes of B6, but not B10 mice, indicating that genetic background influences therapeutic efficacy. Moreover, although previous studies indicated that prion protein deficiency results in more severe EAE in B6 mice, we observed no such effect in B10 mice. In addition, we found that amyloid hexapeptide treatments of B10 and B6 mice elicited differential IL4 responses. Thus, the modulatory potential of prion protein and related treatments with other amyloid hexapeptides in EAE depends on mouse strain.

Significance IL-10–secreting B lymphocytes and peritoneal macrophages are activated by immunization with amyloid fibrils composed of short peptides resulting in reduction of paralysis and inflammation in mice with experimental autoimmune encephalomyelitis. B-cell–deficient μMT mice and IL-10 knockout animals were used to establish the critical role of regulatory B cells in the therapeutic mode of action. Reintroduction of B-1a lymphocytes into the μMT animals reconstituted the ability of the fibrils to ameliorate the paralytic signs, leading to the trafficking of both populations of cells from the peritoneum to secondary lymph organs and not to the CNS. The reduction in CNS inflammation, combined with successful intranasal administration, provides support that this strategy could be translated into an effective human therapeutic.

Similarity between influenza nucleoprotein and hypocretin receptor 2 may trigger vaccine-associated narcolepsy.

Amyloidogenic proteins have long been linked to neurodegenerative diseases. However, amyloid fibrils composed of six amino acids are protective in an animal model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE). The reduction of pro-inflammatory cytokines, decrease in the number of inflammatory foci in the parenchyma and meninges of the brain and spinal cord, and amelioration of the neurological signs of EAE when amyloid fibril-forming hexapeptides are administered reveal that some fibrils provide benefit. The therapeutic activity of the amyloid fibrils arise from diverse pathways that include binding of pro-inflammatory mediators in the plasma, reduction of IL-6, TNF-alpha, and IFN-gamma levels, and induction of type 1 interferon (IFN). Type 1 IFN has been used widely as a therapeutic agent for the treatment of MS and has been shown to be therapeutic in EAE with adoptive transfer of Th1 lymphocytes. However, type 1 IFN is known to exacerbate EAE with adoptive transfer of Th17 lymphocytes. Indeed, the amyloid fibril-forming peptide Tau 623-628 was therapeutic in Th1 adoptively transferred EAE, but ineffective in Th17 adoptively transferred EAE. However, the therapeutic effect of Tau 623-628 was restored in IFN-alpha/beta receptor (IFNAR) knockout mice, indicating that other immune pathways independent of type 1 IFN induction play a role in the amelioration of EAE. Moreover, Amylin 28-33, a polar, non-ionizable peptide that does not form fibrils as rapidly as Tau 623-628, induces a small fraction of type 1 IFN compared to Tau 623-628 and is therapeutic in Th17 EAE. The diverse immunological pathways modulated by the self-assembling hexapeptides are under investigation with a goal to develop novel, safe, and potent therapeutics for neuroinflammation.

Amyloid fibrils composed of peptides as short as six amino acids are effective therapeutics for experimental autoimmune encephalomyelitis (EAE). Immunosuppression arises from at least two pathways: (1) expression of type 1 IFN by pDCs, which were induced by neutrophil extracellular traps arising from the endocytosis of the fibrils; and (2) the reduced expression of IFN-γ, TNF, and IL-6. The two independent pathways stimulated by the fibrils can act in concert to be immunosuppressive in Th1 indications, or in opposition, resulting in inflammation when Th17 T lymphocytes are predominant. The generation of type 1 IFN can be minimized by using polar, nonionizable, amyloidogenic peptides, which are effective in both Th1 and Th17 polarized EAE.

OBJECTIVE: To determine the immune pathways modulated by amyloid fibril-forming peptides composed of six amino acids that have been found to be anti-inflammatory and therapeutic in an animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). BACKGROUND: Our earlier work showed that amyloid fibril formation of a small peptide corresponding to residues 73-92 from the small heat shock protein alpha B crystallin (HspB5) correlated with chaperone activity and amelioration of EAE. However, exchange of one hydrophobic amino acid at position 77, 79, or 81 with a lysine disrupted amyloid formation, chaperone function, and therapeutic efficacy of the peptide. To eliminate the toxicity of amyloid fibrils formed by larger peptides and proteins, we used the minimum number of amino acids capable of forming amyloid fibrils. Peptides composed of six amino acids that form amyloid fibrils were shown to have chaperone activity and were therapeutic in EAE. RESULTS: The levels of IL-6, IL-2, TNF alpha, and IFN gamma were all decreased following treatment with the hexapeptide tau 623-628. We also show that tau 623-628 induces type I interferon (IFN), which is a treatment in MS and indicates a distinct effect not seen in HspB5 treatment. Tau 623-628 was therapeutic in Th1 adoptively transferred EAE, but ineffective in Th17 adoptively transferred EAE, which corresponds with the observation that type I IFN is beneficial in Th1 EAE, but not in Th17 EAE (Axtell et al., Nat Med 2010; 16: 406-412). Amylin 28-33, a polar, non-ionizable peptide, induces very low levels of type I IFN and is therapeutic in Th17 EAE, indicating other immune pathways play a role in amelioration of EAE. CONCLUSIONS: The mode of action of the amyloid-forming hexapeptides is similar to HspB5 in its capacity to bind pro-inflammatory proteins in the plasma, which could have pleiotropic effects including the reduction of pro-inflammatory cytokines. However, the amyloidogenic peptides also modulate diverse immunological pathways, which can differ based upon the composition of the hexapeptides.

Amyloid forming molecules are generally considered harmful. In Alzheimer's Disease two amyloid molecules Aβ A4 and tau vie for consideration as the main pathogenic culprit. But molecules obey the laws of chemistry and defy the way we categorize them as humans with our well-known proclivities to bias in our reasoning. We have been exploring the brains of multiple sclerosis patients to identify molecules that are associated with protection from inflammation and degeneration. In 2001 we noted that aB crystallin (cryab) was the most abundant transcript found in MS lesions, but not in healthy brains. Cryab can reverse paralysis and attenuate inflammation in several models of inflammation including experimental autoimmune encephalomyelitis (EAE), and various models of ischemia. Cryab is an amyloid forming molecule. We have identified a core structure common to many amyloids including amyloid protein Aβ A4, tau, amylin, prion protein, serum amyloid protein P, and cryab. The core hexapeptide structure is highly immune suppressive and can reverse paralysis in EAE when administered systemically. Administration of this amyloid forming hexapeptide quickly lowers inflammatory cytokines in plasma like IL-6 and IL-2. The hexapeptide bind a set of proinflammatory mediators in plasma, including acute phase reactants and complement components. The beneficial properties of amyloid forming hexapeptides provide a potential new therapeutic direction. These experiments indicate that amyloid forming molecules have Janus faces, providing unexpected benefit for neuroinflammatory conditions.

Background: Suppression of activation of pathogenic CD4 + T cells is a potential therapeutic intervention in multiple sclerosis (MS). We previously showed that a small heat shock protein, CRYAB, reduced T cell proliferation, pro-inflammatory cytokine production and clinical signs of experimental allergic encephalomyelitis, a model of MS. Objective: We assessed whether the ability of CRYAB to reduce the activation of T cells translated to the human disease. Methods: CD4 + T cells from healthy controls and volunteers with MS were activated in vitro in the presence or absence of a CRYAB peptide (residues 73–92). Parameters of activation (proliferation rate, cytokine secretion) and tolerance (anergy, activation-induced cell death, microRNAs) were evaluated. Results: The secretion of pro-inflammatory cytokines by CD4 + T cells was decreased in the presence of CRYAB in a subset of relapsing–remitting multiple sclerosis (RRMS) participants with mild disease severity while no changes were observed in healthy controls. Further, there was a correlation for higher levels of miR181a microRNA, a marker upregulated in tolerant CD8 + T cells, in CD4 + T cells of MS patients that displayed suppressed cytokine production (responders). Conclusion: CRYAB may be capable of suppressing the activation of CD4 + T cells from a subset of RRMS patients who appear to have less disability but similar age and disease duration.

The amyloid-forming proteins tau, αB crystallin, and amyloid P protein are all found in lesions of multiple sclerosis (MS). Our previous work established that amyloidogenic peptides from the small heat shock protein αB crystallin (HspB5) and from amyloid β fibrils, characteristic of Alzheimer's disease, were therapeutic in experimental autoimmune encephalomyelitis (EAE), reflecting aspects of the pathology of MS. To understand the molecular basis for the therapeutic effect, we showed a set of amyloidogenic peptides composed of six amino acids, including those from tau, amyloid β A4, major prion protein (PrP), HspB5, amylin, serum amyloid P, and insulin B chain, to be anti-inflammatory and capable of reducing serological levels of interleukin-6 and attenuating paralysis in EAE. The chaperone function of the fibrils correlates with the therapeutic outcome. Fibrils composed of tau 623-628 precipitated 49 plasma proteins, including apolipoprotein B-100, clusterin, transthyretin, and complement C3, supporting the hypothesis that the fibrils are active biological agents. Amyloid fibrils thus may provide benefit in MS and other neuroinflammatory disorders.