An evaluation of the complement-regulating activities of human complement factor H (FH) variants associated with age-related macular degeneration

PURPOSE: Factor H (FH, encoded by CFH) prevents activation of the complement system's alternative pathway (AP) on host tissues. FH impedes C3 convertase (C3bBb) formation, accelerates C3bBb decay, and is a cofactor for factor I (FI)–catalyzed C3b cleavage. Numerous CFH variants are associated with age-related macular degeneration (AMD), but their functional consequences frequently remain undetermined. Here, we conduct functional comparisons between a control version of FH (not AMD linked) and 21 AMD-linked FH variants. METHODS: Recombinantly produced, untagged, full-length FH versions were assayed for binding to C3b and decay acceleration of C3bBb using surface-plasmon resonance, FI-cofactor activity using a fluorescent probe of C3b integrity, suppression of C5b-9 assembly on an AP-activating surface, and inhibition of human AP-mediated lysis of sheep erythrocytes. RESULTS: All versions were successfully purified despite below-average yields for Arg2Thr, Arg53Cys, Arg175Pro, Arg175Gln, Ile221Val, Tyr402His, Pro503Ala, Arg567Gly, Gly1194Asp, and Arg1210Cys. Compared to control FH, Arg2Thr, Leu3Val, Ser58Ala, Asp90Gly, Asp130Asn, Gln400Lys, Tyr402His, Gly650Val, Ser890Ile, and Thr965Met showed minimal functional differences. Arg1210C, Arg53His, Arg175Gln, Gly1194Asp, Pro503Ala, Arg53Cys, Arg576Gly, and Arg175Pro (in order of decreasing efficacy) underperformed, while Ile221Val, Arg303Gln, and Arg303Trp were “marginal.” We newly identified variants toward the center of the molecule, Pro503Ala and Arg567Gly, as potentially pathogenic. CONCLUSIONS: Our approach could be extended to other variants of uncertain significance and to assays for noncanonical FH activities, aiming to facilitate selection of cohorts most likely to benefit from therapeutic FH. This is timely as recombinant therapeutic FH is in development for intravitreal treatment of AMD in patients with reduced FH functionality

Decoding the Components of Dynamics in Three-Domain Proteins

In this study we examine the feasibility and limitations of describing the motional behavior of three-domain proteins in which the domains are linearly connected. In addition to attempting a determination of both the internal and overall re-orientational correlation times, we investigate the existence of correlations in the motions between the three domains. Since in linearly arranged three-domain proteins there are typically no experimental data that can directly report on motional correlation between the first and third domain, we address this question by dynamics simulations. Two limiting cases occur: 1) for weak repulsive potentials and 2) when strong repulsive potentials are applied between sequential domains. The motions of the first and third domains become correlated in the case of strong inter-domain repulsive potentials when these potentials do not allow the angle between the sequential domains to be smaller than about 60°. Although various modeling approaches are available, we chose to use the model-free and extended model-free formalisms of Lipari and Szabo due to their widespread application in the study of protein dynamics. We find that the motional behavior can be separated into two components; the first component represents the concerted overall motion of the three domains, and the second describes the independent component of the motion of each individual domain. We find that this division of the motional behavior of the protein is maintained only when their timescales are distinct and can be made when the angles between sequential domains remain between 60° and 160°. In this work, we identify and quantify inter-domain motional correlations

HpARI protein secreted by a helminth parasite suppresses interleukin-33

Infection by helminth parasites is associated with amelioration of allergic reactivity, but mechanistic insights into this association are lacking. Products secreted by the mouse parasite Heligmosomoides polygyrus suppress type 2 (allergic) immune responses through interference in the interleukin-33 (IL-33) pathway. Here, we identified H. polygyrus Alarmin Release Inhibitor (HpARI), an IL-33-suppressive 26-kDa protein, containing three predicted complement control protein (CCP) modules. In vivo, recombinant HpARI abrogated IL-33, group 2 innate lymphoid cell (ILC2) and eosinophilic responses to Alternaria allergen administration, and diminished eosinophilic responses to Nippostrongylus brasiliensis, increasing parasite burden. HpARI bound directly to both mouse and human IL-33 (in the cytokine's activated state) and also to nuclear DNA via its N-terminal CCP module pair (CCP1/2), tethering active IL-33 within necrotic cells, preventing its release, and forestalling initiation of type 2 allergic responses. Thus, HpARI employs a novel molecular strategy to suppress type 2 immunity in both infection and allergy. Osbourn et al identified HpARI, a protein secreted by a helminth parasite that is capable of suppressing allergic responses. HpARI binds to IL-33 (a critical inducer of allergy) and nuclear DNA, preventing the release of IL-33 from necrotic epithelial cells

The role of the complement system in traumatic brain injury: a review

Traumatic brain injury (TBI) is an important cause of disability and mortality in the western world. While the initial injury sustained results in damage, it is the subsequent secondary cascade that is thought to be the significant determinant of subsequent outcomes. The changes associated with the secondary injury do not become irreversible until some time after the start of the cascade. This may present a window of opportunity for therapeutic interventions aiming to improve outcomes subsequent to TBI. A prominent contributor to the secondary injury is a multifaceted inflammatory reaction. The complement system plays a notable role in this inflammatory reaction; however, it has often been overlooked in the context of TBI secondary injury. The complement system has homeostatic functions in the uninjured central nervous system (CNS), playing a part in neurodevelopment as well as having protective functions in the fully developed CNS, including protection from infection and inflammation. In the context of CNS injury, it can have a number of deleterious effects, evidence for which primarily comes not only from animal models but also, to a lesser extent, from human post-mortem studies. In stark contrast to this, complement may also promote neurogenesis and plasticity subsequent to CNS injury. This review aims to explore the role of the complement system in TBI secondary injury, by examining evidence from both clinical and animal studies. We examine whether specific complement activation pathways play more prominent roles in TBI than others. We also explore the potential role of complement in post-TBI neuroprotection and CNS repair/regeneration. Finally, we highlight the therapeutic potential of targeting the complement system in the context of TBI and point out certain areas on which future research is needed

Virulence of Group A Streptococci Is Enhanced by Human Complement Inhibitors

Streptococcus pyogenes, also known as Group A Streptococcus (GAS), is an important human bacterial pathogen that can cause invasive infections. Once it colonizes its exclusively human host, GAS needs to surmount numerous innate immune defense mechanisms, including opsonization by complement and consequent phagocytosis. Several strains of GAS bind to human-specific complement inhibitors, C4b-binding protein (C4BP) and/or Factor H (FH), to curtail complement C3 (a critical opsonin) deposition. This results in diminished activation of phagocytes and clearance of GAS that may lead to the host being unable to limit the infection. Herein we describe the course of GAS infection in three human complement inhibitor transgenic (tg) mouse models that examined each inhibitor (human C4BP or FH) alone, or the two inhibitors together (C4BPxFH or 'double' tg). GAS infection with strains that bound C4BP and FH resulted in enhanced mortality in each of the three transgenic mouse models compared to infection in wild type mice. In addition, GAS manifested increased virulence in C4BPxFH mice: higher organism burdens and greater elevations of pro-inflammatory cytokines and they died earlier than single transgenic or wt controls. The effects of hu-C4BP and hu-FH were specific for GAS strains that bound these inhibitors because strains that did not bind the inhibitors showed reduced virulence in the 'double' tg mice compared to strains that did bind; mortality was also similar in wild-type and C4BPxFH mice infected by non-binding GAS. Our findings emphasize the importance of binding of complement inhibitors to GAS that results in impaired opsonization and phagocytic killing, which translates to enhanced virulence in a humanized whole animal model. This novel hu-C4BPxFH tg model may prove invaluable in studies of GAS pathogenesis and for developing vaccines and therapeutics that rely on human complement activation for efficacy

New functional and structural insights from updated mutational databases for complement factor H, Factor I, membrane cofactor protein and C3

aHUS (atypical haemolytic uraemic syndrome), AMD (age-related macular degeneration) and other diseases are associated with defective AP (alternative pathway) regulation. CFH (complement factor H), CFI (complement factor I), MCP (membrane cofactor protein) and C3 exhibited the most disease-associated genetic alterations in the AP. Our interactive structural database for these was updated with a total of 324 genetic alterations. A consensus structure for the SCR (short complement regulator) domain showed that the majority (37%) of SCR mutations occurred at its hypervariable loop and its four conserved Cys residues. Mapping 113 missense mutations onto the CFH structure showed that over half occurred in the C-terminal domains SCR-15 to -20. In particular, SCR-20 with the highest total of affected residues is associated with binding to C3d and heparin-like oligosaccharides. No clustering of 49 missense mutations in CFI was seen. In MCP, SCR-3 was the most affected by 23 missense mutations. In C3, the neighbouring thioester and MG (macroglobulin) domains exhibited most of 47 missense mutations. The mutations in the regulators CFH, CFI and MCP involve loss-of-function, whereas those for C3 involve gain-of-function. This combined update emphasizes the importance of the complement AP in inflammatory disease, clarifies the functionally important regions in these proteins, and will facilitate diagnosis and therapy

Effect of orthodontic management and orofacial muscle training protocols on the correction of myofunctional and myoskeletal problems in developing dentition. A systematic review and meta-analysis

The aim of this review was to evaluate available evidence on the effect of early orthodontic management and myofunctional treatment in the developing dentition children, on anterior open bite correction, as well as on normalization of patterns of mouth breathing, swallowing and tongue resting position and pressure. Electronic searches in MEDLINE, Cochrane and LILACS, without language restrictions were conducted. Additionally, unpublished literature was identified. Randomized controlled trials, or controlled clinical trials, comparing interventions applied to manage anterior open bite and other muscle functions such as breathing/swallowing pattern and tongue resting position and pressure, were considered. Quality assessment was based on the Cochrane Risk of Bias tool. Random effects meta-analyses were conducted to assess treatment effects. From the 265 initial search results, 15 articles were included in the review. Eight were randomized controlled trials (RCTs) and 7 were controlled clinical trials. Treatment outcomes comprised skeletal and dentoalveolar changes recorded cephalometrically, mouth posture and lip closure normalization, improvement of tongue resting position/pressure and modification of swallowing pattern. Quantitative synthesis was possible for only 2 of the included RCTs. There was no evidence to support bonded lingual spurs over banded fixed appliances for the correction of anterior open bite in mixed dentition children presenting nonnutritive oral habits at the onset of treatment (SMD: −0.03; 95%CI: −.81, 0.74; P = 0.94). Although early orthodontic management and myofunctional treatment in the deciduous and mixed dentition children appears to be a promising approach, the quality of the existing evidence is questionable. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Lt

Treatment outcomes after extraction and nonextraction treatment evaluated with the American board of orthodontics objective grading system

Introduction: A controversy exists regarding better treatment outcomes when patients treated with extractions and without extractions are evaluated. The aims of this study were to use the American Board of Orthodontics objective grading system (ABO-OGS) to evaluate and compare treatment outcomes in extraction vs nonextraction Class I patients and to determine whether the treatment choice was a significant predictor of success according to the ABO examination. © 2014 by the American Association of Orthodontists