Phase I Safety, Tolerability, and Pharmacokinetic Study of Recombinant Human Mannan-Binding Lectin

Dysregulation of complement system in neuropsychiatric disorders: A mini review

Complement system is one of the most important defense mechanisms of the innate immune system. In addition to their roles in immune regulation, complement proteins are also involved in neurodevelopment and adult brain plasticity. Complement dysregulation has been shown in neurodevelopmental disorders including schizophrenia and autism spectrum disorder as well as in mood disorders. A number of clinical as well as genetic studies suggest the role of complement proteins in the cortical thinning and excessive synaptic pruning frequently associated with schizophrenia. The changes in complement proteins are also associated with the pathophysiology of autism spectrum disorder, major depressive disorder and bipolar disorder, but warrant further research. In addition, rodent models suggest a strong case for complement system in anxiety-like behavior. In this article, we review the recent findings on the role of complement system in neuropsychiatric disorders. The possible uses for future complement targeted therapies are also discussed.

In silico investigation and potential therapeutic approaches of natural products for COVID-19: Computer-aided drug design perspective

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a substantial number of deaths around the world, making it a serious and pressing public health hazard. Phytochemicals could thus provide a rich source of potent and safer anti-SARS-CoV-2 drugs. The absence of approved treatments or vaccinations continues to be an issue, forcing the creation of new medicines. Computer-aided drug design has helped to speed up the drug research and development process by decreasing costs and time. Natural compounds like terpenoids, alkaloids, polyphenols, and flavonoid derivatives have a perfect impact against viral replication and facilitate future studies in novel drug discovery. This would be more effective if collaboration took place between governments, researchers, clinicians, and traditional medicine practitioners’ safe and effective therapeutic research. Through a computational approach, this study aims to contribute to the development of effective treatment methods by examining the mechanisms relating to the binding and subsequent inhibition of SARS-CoV-2 ribonucleic acid (RNA)-dependent RNA polymerase (RdRp). The in silico method has also been employed to determine the most effective drug among the mentioned compound and their aquatic, nonaquatic, and pharmacokinetics’ data have been analyzed. The highest binding energy has been reported -11.4 kcal/mol against SARS-CoV-2 main protease (7MBG) in L05. Besides, all the ligands are non-carcinogenic, excluding L04, and have good water solubility and no AMES toxicity. The discovery of preclinical drug candidate molecules and the structural elucidation of pharmacological therapeutic targets have expedited both structure-based and ligand-based drug design. This review article will assist physicians and researchers in realizing the enormous potential of computer-aided drug design in the design and discovery of therapeutic molecules, and hence in the treatment of deadly diseases.

Host-informed therapies for the treatment of pneumococcal pneumonia

Over the past two decades, traditional antimicrobial strategies have lost efficacy due to a rapid rise in antibiotic resistance and limited success in developing new antibiotics. Rather than relying on therapeutics solely targeting the bacterial pathogen, therapies are emerging that simultaneously focus on host responses. Here, we describe the most promising 'host-informed therapies' (HITs) in two categories: those that aid patients with fully functional immune systems, and those that aid patients with perturbed immune processes. Using Streptococcus pneumoniae, the leading cause of bacterial pneumonia, as a case study, we show HITs as an attractive option for supplementing infection management. However, to broaden their applicability and design new strategies, targeted research and clinical trials will be essential.

Characterization of DNA-protein complexes by nanoparticle tracking analysis and their association with systemic lupus erythematosus

Nanotechnology enables investigations of single biomacromolecules, but technical challenges have limited the application in liquid biopsies, for example, blood plasma. Nonetheless, tools to characterize single molecular species in such samples represent a significant unmet need with the increasing appreciation of the physiological importance of protein structural changes at nanometer scale. Mannose-binding lectin (MBL) is an oligomeric plasma protein and part of the innate immune system through its ability to activate complement. MBL also serves a role as a scavenger for cellular debris, especially DNA. This may link functions of MBL with several inflammatory diseases in which cell-free DNA now appears to play a role, but mechanistic insight has been lacking. By making nanoparticle tracking analysis possible in human plasma, we now show that superoligomeric structures of MBL form nanoparticles with DNA. These oligomers correlate with disease activity in systemic lupus erythematosus patients. With the direct quantification of the hydrodynamic radius, calculations following the principles of Taylor dispersion in the blood stream connect the size of these complexes to endothelial inflammation, which is among the most important morbidities in lupus. Mechanistic insight from an animal model of lupus supported that DNA-stabilized superoligomers stimulate the formation of germinal center B cells and drive loss of immunological tolerance. The formation involves an inverse relationship between the concentration of MBL superoligomers and antibodies to double-stranded DNA. Our approach implicates the structure of DNA-protein nanoparticulates in the pathobiology of autoimmune diseases.

Nutraceutical Approach to Preventing Coronavirus Disease 2019 and Related Complications

Introduction

Several months ago, Chinese authorities identified an atypical pneumonia in Wuhan city, province of Hubei (China) caused by a novel coronavirus (2019-nCoV or SARS-CoV-2). The WHO announced this new disease was to be known as "COVID-19".

Evidence Acquisition

Several approaches are currently underway for the treatment of this disease, but a specific cure remains to be established.

Evidence Synthesis

This review will describe how the use of selected nutraceuticals could be helpful, in addition to pharmacological therapy, in preventing some COVID-19-related complications in infected patients.

Conclusions

Even if a specific and effective cure for COVID-19 still has some way to go, selected nutraceuticals could be helpful, in addition to pharmacological therapy, in preventing some COVID-19-related complications in infected patients.

Molecular scaffolds from mother nature as possible lead compounds in drug design and discovery against coronaviruses: A landscape analysis of published literature and molecular docking studies

The recent outbreak of viral infection and its transmission has highlighted the importance of its slowdown for the safeguard of public health, globally. The identification of novel drugs and efficient therapies against these infectious viruses is need of the hour. The eruption of COVID-19 is caused by a novel acute respiratory syndrome virus SARS-CoV-2 which has taken the whole world by storm as it has transformed into a global pandemic. This lethal syndrome is a global health threat to general public which has already affected millions of people. Despite the development of some potential vaccines and repurposed drugs by some Pharma companies, this health emergency needs more attention due to the less efficacy of these vaccines coupled with the emergence of novel and resistant strains of SARS-CoV-2. Due to enormous structural diversity and biological applications, natural products are considered as a wonderful source of drugs for such diseases. Natural product based drugs constitute a substantial proportion of the pharmaceutical market particularly in the therapeutic areas of infectious diseases and oncology. The naturally occurring bioactive antiviral phytochemicals including alkaloids, flavonoids and peptides have been subjected to virtual screening against COVID-19. Since there is no specific medicine available for the treatment of Covid-19, designing new drugs using in silico methods plays an all important role to find that magic bullet which can target this lethal virus. The in silico method is not only quick but economical also when compared to the other conventional methods which are hit and trial methods. Based on this in silico approach, various natural products have been recently identified which might have a potential to inhibit COVID-19 outbreak. These natural products have been shown by these docking studies to interact with the spike protein of the novel coronavirus. This spike protein has been shown to bind to a transmembrane protein called Angiotensin converting enzyme 2 (ACE2), this protein acts as a receptor for the viral spike protein. This comprehensive review article anticipates providing a summary of the authentic and peer reviewed published literature about the potential of natural metabolites that can be developed into possible lead compounds against this new threat of Covid-19. Main focus of the article will be to highlight natural sources of potential anti-coronavirus molecules, mechanism of action, docking studies and the target proteins as well as their toxicity profiles. This review article intends to provide a starting point for the research endeavors that are needed for the design and development of drugs based on pure natural products, their synthetic or semi-synthetic derivatives and standardized plant extracts. This review article will be highly helpful for scientists who are working or intend to work on antiviral drugs from natural sources.

Therapeutic Targeting of the Complement System: From Rare Diseases to Pandemics

The complement system was discovered at the end of the 19th century as a heat-labile plasma component that "complemented" the antibodies in killing microbes, hence the name "complement." Complement is also part of the innate immune system, protecting the host by recognition of pathogen-associated molecular patterns. However, complement is multifunctional far beyond infectious defense. It contributes to organ development, such as sculpting neuron synapses, promoting tissue regeneration and repair, and rapidly engaging and synergizing with a number of processes, including hemostasis leading to thromboinflammation. Complement is a double-edged sword. Although it usually protects the host, it may cause tissue damage when dysregulated or overactivated, such as in the systemic inflammatory reaction seen in trauma and sepsis and severe coronavirus disease 2019 (COVID-19). Damage-associated molecular patterns generated during ischemia-reperfusion injuries (myocardial infarction, stroke, and transplant dysfunction) and in chronic neurologic and rheumatic disease activate complement, thereby increasing damaging inflammation. Despite the long list of diseases with potential for ameliorating complement modulation, only a few rare diseases are approved for clinical treatment targeting complement. Those currently being efficiently treated include paroxysmal nocturnal hemoglobinuria, atypical hemolytic-uremic syndrome, myasthenia gravis, and neuromyelitis optica spectrum disorders. Rare diseases, unfortunately, preclude robust clinical trials. The increasing evidence for complement as a pathogenetic driver in many more common diseases suggests an opportunity for future complement therapy, which, however, requires robust clinical trials; one ongoing example is COVID-19 disease. The current review aims to discuss complement in disease pathogenesis and discuss future pharmacological strategies to treat these diseases with complement-targeted therapies. SIGNIFICANCE STATEMENT: The complement system is the host's defense friend by protecting it from invading pathogens, promoting tissue repair, and maintaining homeostasis. Complement is a double-edged sword, since when dysregulated or overactivated it becomes the host's enemy, leading to tissue damage, organ failure, and, in worst case, death. A number of acute and chronic diseases are candidates for pharmacological treatment to avoid complement-dependent damage, ranging from the well established treatment for rare diseases to possible future treatment of large patient groups like the pandemic coronavirus disease 2019.

Phytogenic Products and Phytochemicals as a Candidate Strategy to Improve Tolerance to Coronavirus

Coronaviruses are the causative agents of many infectious diseases in human and animals. These included severe acute respiratory syndrome (SARS), avian infectious bronchitis (IBV) in poultry, Middle East respiratory syndrome (MERS), and coronavirus disease 2019 (COVID-19) in humans. These results had considerable death burdens and negative influences on social-economic life. Since the appearance of the outbreak of the COVID-19 pandemic, continuous investigations have been carried out by researchers to find active compounds, mainly from plants, as natural sources, that could inhibit or stop the proliferation of the causative agent of COVID-19 (SARS-CoV-2). The most common symptoms caused by infections with COVID-19 can include cough, fever, and sore throat. Nevertheless, there is a shortage of active antiviral compounds for treating different strains of coronavirus. Herbal medicine is a class of medication that originates from nature and is aimed at decreasing the use of preservatives, excipients, or other additives and, consequently, lesser side effects. The rapid spread of COVID-19 infection besides the lack of knowledge about any treatments and the growing concern of the public from the virus directed us toward writing this review article in an aim to provide alternatives to the allopathic medicine use. There is a wealth of chemical diversity in the naturally existing compounds, including their antiviral activities, which may encourage their utilization as therapeutics against viral infections, including coronaviruses. The majority of publications on the herbal remedies of coronavirus, MERS, or SARS focused primarily on the use of polar compounds. These substances displayed encouraging inhibitory influences on coronavirus in humans. These include psoralidin, scutellarein, silvestrol, tryptanthrin, caffeic acid, quercetin, myricetin, saikosaponin B2, griffithsin (lectins), and isobavachalcone. Some other agents like lycorine may be useful, if the antiviral activity is obtained by concentrations below the toxic plasma levels. According to the available literatures, the most promising inhibitors of coronaviruses are polyphenolic compounds, which are small molecules with conjugated fused ring structures.

Natural product-derived phytochemicals as potential agents against coronaviruses: A review

Coronaviruses are responsible for a growing economic, social and mortality burden, as the causative agent of diseases such as severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), avian infectious bronchitis virus (IBV) and COVID-19. However, there is a lack of effective antiviral agents for many coronavirus strains. Naturally existing compounds provide a wealth of chemical diversity, including antiviral activity, and thus may have utility as therapeutic agents against coronaviral infections. The PubMed database was searched for papers including the keywords coronavirus, SARS or MERS, as well as traditional medicine, herbal, remedy or plants, with 55 primary research articles identified. The overwhelming majority of publications focussed on polar compounds. Compounds that show promise for the inhibition of coronavirus in humans include scutellarein, silvestrol, tryptanthrin, saikosaponin B₂, quercetin, myricetin, caffeic acid, psoralidin, isobavachalcone, and lectins such as griffithsin. Other compounds such as lycorine may be suitable if a therapeutic level of antiviral activity can be achieved without exceeding toxic plasma concentrations. It was noted that the most promising small molecules identified as coronavirus inhibitors contained a conjugated fused ring structure with the majority being classified as being polyphenols.

Improvement of pharmacokinetic properties of therapeutic antibodies by antibody engineering

Monoclonal antibodies (mAbs) have become an important therapeutic option for several diseases. Since several mAbs have shown promising efficacy in clinic, the competition to develop mAbs has become severe. In efforts to gain a competitive advantage over other mAbs and provide significant benefits to patients, innovations in antibody engineering have aimed at improving the pharmacokinetic properties of mAbs. Because engineering can provide therapeutics that are more convenient, safer, and more efficacious for patients in several disease areas, it is an attractive approach to provide significant benefits to patients. Further advances in engineering mAbs to modulate their pharmacokinetics were driven by the increase of total soluble target antigen concentration that is often observed after injecting a mAb, which then requires a high dosage to antagonize. To decrease the required dosage, several antibody engineering techniques have been invented that reduce the total concentration of soluble target antigen. Here, we review the various ways that antibody engineering can improve the pharmacokinetic properties of mAbs.

Substitution of Mannan-Binding Lectin (MBL)-Deficient Serum With Recombinant MBL Results in the Formation of New MBL/MBL-Associated Serine Protease Complexes

The lectin pathway (LP) of complement activation depends on the activation of the MBL-associated serine proteases (MASPs) circulating in complex with mannan-binding lectin (MBL). MBL deficiency is the most common complement deficiency and has been associated with several pathological conditions. As we had previously shown, plasma-derived MBL (pdMBL) contains pre-activated MASPs that upon in vivo pdMBL substitution results in restoration of MBL concentrations but no LP functionality due to immediate inactivation of pdMBL-MASP complexes upon infusion. In this study, we analyzed MBL-sufficient and -deficient serum by size-exclusion chromatography for complexes of LP activation. In both sera, we identified non-bound free forms of MASP-2 and to lesser extent MASP-1/3. After addition of recombinant MBL (rMBL) to MBL-deficient serum, these free MASPs were much less abundantly present, which is highly suggestive for the formation of high-molecular complexes that could still become activated upon subsequent ligand binding as shown by a restoration of C4-deposition of MBL-deficient serum. Ficolin (FCN)-associated MASPs have been described to redistribute to ligand-bound MBL, hereby forming new MBL/MASP complexes. However, reconstitution of MBL-deficient serum with rMBL did not change the relative size of the FCN molecules suggestive for a limited redistribution in fluid phase of already formed complexes. Our findings demonstrate that rMBL can associate with free non-bound MASPs in fluid phase while preserving full restoration of LP functionality. In contrast to pdMBL products containing pre-activated MASPs which become inactivated almost immediately, these current data provide a rationale for substitution studies using rMBL instead.

Vulvovaginal candidiasis: Epidemiology, microbiology and risk factors

Vulvovaginal candidiasis (VVC) is an infection caused by Candida species that affects millions of women every year. Although Candida albicans is the main cause of VVC, the identification of non-Candida albicans Candida (NCAC) species, especially Candida glabrata, as the cause of this infection, appears to be increasing. The development of VVC is usually attributed to the disturbance of the balance between Candida vaginal colonization and host environment by physiological or nonphysiological changes. Several host-related and behavioral risk factors have been proposed as predisposing factors for VVC. Host-related factors include pregnancy, hormone replacement, uncontrolled diabetes, immunosuppression, antibiotics, glucocorticoids use and genetic predispositions. Behavioral risk factors include use of oral contraceptives, intrauterine device, spermicides and condoms and some habits of hygiene, clothing and sexual practices. Despite a growing list of recognized risk factors, much remains to be elucidated as the role of host versus microorganisms, in inducing VVC and its recurrence. Thus, this review provides information about the current state of knowledge on the risk factors that predispose to VVC, also including a revision of the epidemiology and microbiology of VVC, as well as of Candida virulence factors associated with vaginal pathogenicity.

Therapeutics for postexposure treatment of Ebola virus infection

The current Ebola virus disease (EVD) outbreak in West Africa is the largest with over 5100 deaths in four West African countries as of 14 November 2014. EVD has high case-fatality rates but no licensed treatment or vaccine is yet available. Several vaccine candidates that protected nonhuman primates are not yet available for clinical use. Slow development of vaccine-stimulated immunity, sporadic nature and fast progression of EVD underlines the need for the development of effective postexposure therapeutic drugs. WHO encouraged the use of untested drugs for EVD to curb the fast-spreading outbreak. Here, we summarize therapeutics for EVD including monoclonal antibody-based therapy and inhibitors of viral replication including our recently developed small-molecule inhibitors of VP30 dephosphorylation.

Human lectins and their roles in viral infections

Innate recognition of virus proteins is an important component of the immune response to viral pathogens. A component of this immune recognition is the family of lectins; pattern recognition receptors (PRRs) that recognise viral pathogen-associated molecular patterns (PAMPs) including viral glycoproteins. In this review we discuss the contribution of soluble and membrane-associated PRRs to immunity against virus pathogens, and the potential role of these molecules in facilitating virus replication. These processes are illustrated with examples of viruses including human immunodeficiency virus (HIV), hepatitis C virus (HCV) and Ebola virus (EBOV). We focus on the structure, function and genetics of the well-characterised C-type lectin mannose-binding lectin, the ficolins, and the membrane-bound CD209 proteins expressed on dendritic cells. The potential for lectin-based antiviral therapies is also discussed.

Limited effect of recombinant human mannose-binding lectin on the infection of novel influenza A (H7N9) virus in vitro

Mannose-binding lectin (MBL), a pattern-recognition molecule in serum, recognizes specific hexose sugars rich in mannose and N-acetylglucosamine on bacterium, yeasts, viruses as well as apoptotic cells. It has been well-identified that MBL has antiviral effects via binding to seasonal influenza H1 and H3 subtype viruses. Influenza A (H7N9) virus, a novel reassortant virus to human population, possesses the surface hemagglutinin (HA) and neuraminidase (NA) genes from duck and wild-bird influenza viruses and internal genes from poultry H9N2 viruses. As of Dec 7th, 2014, a total of 467 human infections and 183 fatal cases have been identified. Here, recombinant human (rh) MBL was tested for its binding and effects on hemagglutination inhibition (HI) and NA activity inhibition (NAI) of avian H7N9, H9N2 and human H3N2 viruses. We discovered that rhMBL exhibited a strong binding to H7N9 virus as human H3N2 did at high virus titers. However, it performed a significantly weaker HI activity effect on H7N9 comparing to those of H3N2 and H9N2, even at a much higher concentration (3.67 ± 0.33 vs. 0.026 ± 0.001 and 0.083 ± 0.02 μg/mL, respectively). Similarly, minor NAI effect of rhMBL, even at up to 10 μg/mL, was found on H7N9 virus while it displayed significant effects on both H3N2 and H9N2 at a lowest concentration of 0.0807 ± 0.009 and 0.0625 μg/mL, respectively. The HI and NAI effects of rhMBL were calcium-dependent and mediated by lectin domain. Our findings suggest that MBL, the host innate molecule, has differential interference effects with human and avian influenza virus and limited antiviral effect against H7N9 virus.

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Comparable binding of rhMBL to avian H7N9 virus as human H3N2 virus.

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Limited antiviral effect of rhMBL against avian H7N9 virus.

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Insensitivity of H7N9 virus to rhMBL may confer its infection severity.

Restoration of MBL-deficiency: redefining the safety, efficacy and viability of MBL-substitution therapy

MBL-deficiency is a commonly occurring deficiency of the innate immune system, affecting a substantial part of the population and has been extensively studied. MBL appears to function as a disease modifier. The role of MBL in different conditions is context-dependent. Many clinical studies show conflicting results, which can be partially explained by different definitions of MBL-deficiency, including phenotype- and genotype-based approaches. In this review we give an overview of literature of MBL, its role in different pathologies, diseases and patient populations. We review MBL replacement studies, and discuss the potential of MBL substitution therapy. We finally suggest that new MBL substitution trials should be conducted within a predefined patient population. MBL-deficiency should be based on serum levels and confirmed by genotyping.

Recombinant human mannose-binding lectin dampens human alveolar macrophage inflammatory responses to influenza A virus in vitro

IAV pneumonia remains a serious global health problem, and preventative and therapeutic strategies remain limited. AM are critical effector cells in the control of influenza, impairing IAV replication, promoting IAV clearance, and promoting efferocytosis and resolution of lung inflammation. MBL, an innate immune pattern recognition molecule, present in the lungs, binds IAV, and plasma MBL deficiency is associated with increased susceptibility to IAV, although the mechanism remains incompletely understood, and the influence of MBL on the IAV-AM interaction has not been established. In the current study, focusing on human macrophages (U937 cell line and clinically relevant human AM), data demonstrated that unopsonized IAV is readily internalized, induced release of TNF and ROS, and promoted macrophage apoptosis. In contrast, IAV, opsonized with rhMBL, reduced IAV uptake and macrophage apoptosis and dramatically reduced TNF release and ROS. Macrophage host-defense responses were reduced further in the presence of MASPs. Taken together, these data support the concept that rhMBL may serve a protective innate host response and a critical biological response modifier function by limiting AM inflammation, oxidative injury, and AM apoptosis, which may allow effective IAV clearance while limiting collateral damage to vital organs, such as the lungs.

The emerging role of complement lectin pathway in trypanosomatids: molecular bases in activation, genetic deficiencies, susceptibility to infection, and complement system-based therapeutics

The innate immune system is evolutionary and ancient and is the pivotal line of the host defense system to protect against invading pathogens and abnormal self-derived components. Cellular and molecular components are involved in recognition and effector mechanisms for a successful innate immune response. The complement lectin pathway (CLP) was discovered in 1990. These new components at the complement world are very efficient. Mannan-binding lectin (MBL) and ficolin not only recognize many molecular patterns of pathogens rapidly to activate complement but also display several strategies to evade innate immunity. Many studies have shown a relation between the deficit of complement factors and susceptibility to infection. The recently discovered CLP was shown to be important in host defense against protozoan microbes. Although the recognition of pathogen-associated molecular patterns by MBL and Ficolins reveal efficient complement activations, an increase in deficiency of complement factors and diversity of parasite strategies of immune evasion demonstrate the unsuccessful effort to control the infection. In the present paper, we will discuss basic aspects of complement activation, the structure of the lectin pathway components, genetic deficiency of complement factors, and new therapeutic opportunities to target the complement system to control infection.

Mannose-binding lectin genotype influences frequency and duration of infectious complications in children with malignancy

Children with cancer receiving identical treatment differ in their experience of infection, suggesting that variations in immunity may influence susceptibility to infection. Studies of the influence of mannose-binding lectin (MBL), an important component of the innate immune system, in children with febrile neutropenia (FN) have yielded conflicting results. We examined the role of MBL in infection susceptibility in the largest cohort of children with cancer reported to date. MBL levels were measured and genotyping performed on children (≤16 y) receiving chemotherapy for cancer in London, UK. Clinical data from FN episodes were recorded prospectively. MBL status was assessed in 269 children; 513 episodes of FN were captured from 211 patients. Patients with MBL2 polymorphisms experienced more FN episodes than wildtype genotype (median 2 vs. 1, respectively; P = 0.074) and more episodes with documented infection (P = 0.045). Patients experiencing multiple FN episodes had lower MBL levels (P = 0.036). MBL genotype influenced duration of episode in some groups: high-risk MBL-deficient patients spent up to 5 nights longer/episode in hospital than equivalent wildtypes. These results indicate that MBL deficiency influences both susceptibility to and outcome of FN episodes and may be most important in those patients at higher risk of complications of FN.

Birds, babies and blood

This is an autobiographical review describing the author's career in immunology research and summarizing his current understanding of the areas involved. Contributions to autoimmunity, immune deficiency, transfusion immunology, HLA-disease associations, reproductive immunology, cellular therapies, and innate immunity are included; also discussion of medical research ethics and various research-related activities.

Potential vaccines and post-exposure treatments for filovirus infections

Viruses of the family Filoviridae represent significant health risks as emerging infectious diseases as well as potentially engineered biothreats. While many research efforts have been published offering possibilities toward the mitigation of filoviral infection, there remain no sanctioned therapeutic or vaccine strategies. Current progress in the development of filovirus therapeutics and vaccines is outlined herein with respect to their current level of testing, evaluation, and proximity toward human implementation, specifically with regard to human clinical trials, nonhuman primate studies, small animal studies, and in vitro development. Contemporary methods of supportive care and previous treatment approaches for human patients are also discussed.

Evolution, revolution and heresy in the genetics of infectious disease susceptibility

Infectious pathogens have long been recognized as potentially powerful agents impacting on the evolution of human genetic diversity. Analysis of large-scale case–control studies provides one of the most direct means of identifying human genetic variants that currently impact on susceptibility to particular infectious diseases. For over 50 years candidate gene studies have been used to identify loci for many major causes of human infectious mortality, including malaria, tuberculosis, human immunodeficiency virus/acquired immunodeficiency syndrome, bacterial pneumonia and hepatitis. But with the advent of genome-wide approaches, many new loci have been identified in diverse populations. Genome-wide linkage studies identified a few loci, but genome-wide association studies are proving more successful, and both exome and whole-genome sequencing now offer a revolutionary increase in power. Opinions differ on the extent to which the genetic component to common disease susceptibility is encoded by multiple high frequency or rare variants, and the heretical view that most infectious diseases might even be monogenic has been advocated recently. Review of findings to date suggests that the genetic architecture of infectious disease susceptibility may be importantly different from that of non-infectious diseases, and it is suggested that natural selection may be the driving force underlying this difference.

A pilot study of host genetic variants associated with influenza-associated deaths among children and young adults

Low-producing MBL2 genotypes may have increased risk for MRSA co-infection.

We compared the prevalence of 8 polymorphisms in the tumor necrosis factor and mannose-binding lectin genes among 105 children and young adults with fatal influenza with US population estimates and determined in subanalyses whether these polymorphisms were associated with sudden death and bacterial co-infection among persons with fatal influenza. No differences were observed in genotype prevalence or minor allele frequencies between persons with fatal influenza and the reference sample. Fatal cases with low-producing MBL2 genotypes had a 7-fold increased risk for invasive methicillin-resistant Staphylococcus aureus (MRSA) co-infection compared with fatal cases with high- and intermediate-producing MBL2 genotypes (odds ratio 7.1, 95% confidence interval 1.6–32.1). Limited analysis of 2 genes important to the innate immune response found no association between genetic variants and fatal influenza infection. Among children and young adults who died of influenza, low-producing MBL2 genotypes may have increased risk for MRSA co-infection.

Mannose-binding lectin and the balance between immune protection and complication

The innate immune system is evolutionarily ancient and biologically primitive. Historically, it was first identified as an element of the immune system that provides the first-line response to pathogens, and increasingly it is recognized for its central housekeeping role and its essential functions in tissue homeostasis, including coagulation and inflammation, among others. A pivotal link between the innate immune system and other functions is mannose-binding lectin (MBL), a pattern recognition molecule. Multiple studies have demonstrated that MBL deficiency increases susceptibility to infection, and the mechanisms associated with this susceptibility to infection include reduced opsonophagocytic killing and reduced activation of the lectin complement pathway. Results from our laboratory have demonstrated that MBL and MBL-associated serine protease (MASP)-1/3 together mediate coagulation factor-like activities, including thrombin-like activity. MBL and/or MASP-1/3-deficient hosts demonstrate in vivo evidence that MBL and MASP-1/3 are involved with hemostasis following injury. Staphylococcus aureus-infected MBL null mice developed disseminated intravascular coagulation, which was associated with elevated blood IL-6 levels (but not TNF-α) and systemic inflammatory responses. Infected MBL null mice also develop liver injury. These findings suggest that MBL deficiency may manifest as disseminated intravascular coagulation and organ failure with infection. Beginning from these observations, this review focuses on the interaction of innate immunity and other homeostatic systems, the derangement of which may lead to complications in infection and other inflammatory states.

Mannose-binding lectin 2 polymorphisms do not influence frequency or type of infection in adults with chemotherapy induced neutropaenia

Background

Mannose-binding Lectin protein (MBL) has been suggested to be relevant in the defence against infections in immunosuppressed individuals. In a Swedish adult cohort immunosuppressed from both the underlying disease and from iatrogenic treatments for their underlying disease we investigated the role of MBL in susceptibility to infection.

Methods

In this cross sectional, prospective study, blood samples obtained from 96 neutropaenic febrile episodes, representing 82 individuals were analysed for single nucleotide polymorphism (SNP) in the MBL2 gene. Concurrent measurement of plasma MBL protein concentrations was also performed for observation of acute response during febrile episodes.

Findings

No association was observed between MBL2 genotype or plasma MBL concentrations, and the type or frequency of infection. Adding to the literature, we found no evidence that viral infections or co-infections with virus and bacteria would be predisposed by MBL deficiency. We further saw no correlation between MBL2 genotype and the risk of fever. However, fever duration in febrile neutropaenic episodes was negatively associated with MBL2 SNP mutations (p<0.05). Patients with MBL2 SNP mutations presented a median febrile duration of 1.8 days compared with 3 days amongst patients with wildtype MBL2 genotype.

Interpretation

We found no clear association between infection, or infection type to MBL2 genotypes or plasma MBL concentration, and add to the reports casting doubts on the benefit of recombinant MBL replacement therapy use during iatrogenic neutropaenia.

Mannan-binding lectin deficiency - Good news, bad news, doesn't matter?

Mannan-binding lectin (MBL) deficiency has been classified as a commonly occurring immune disorder, affecting approximately 30% of the human population. MBL, being part of the innate immune system, supports the recognition of infectious pathogens by binding to carbohydrate moieties expressed on microorganisms and activates the lectin pathway of the complement system. MBL2 gene polymorphisms are associated with quantitative and qualitative MBL abnormalities in the serum. The clinical impact of MBL deficiency and its association to a wide variety of diseases has been extensively studied. The picture is puzzling as the studies suggest a detrimental or beneficial or no impact of low or high MBL serum levels on disease susceptibility. In this review we attempt to extract what is relevant from the literature and address controversial issues. We finally suggest that a comprehensive understanding of the role of MBL in human diseases requires considering its context-dependency.

Decreased efferocytosis and mannose binding lectin in the airway in bronchiolitis obliterans syndrome

BACKGROUND

Mannose binding lectin (MBL) is a key mediator of both innate immunity and efferocytosis (phagocytosis of apoptotic cells) in the airway. Defective efferocytosis results in a net increase in apoptotic material that can undergo secondary necrosis, leading to tissue damage and chronic inflammation. We have shown reduced MBL and efferocytosis in other chronic inflammatory lung diseases; we therefore hypothesized that reduced MBL and efferocytosis in the airways may be a determinant of bronchiolitis obliterans syndrome (BOS) after lung transplantation.

METHODS

We investigated MBL (enzyme-linked immunosorbent assay [ELISA]), MBL-mediated complement deposition (UC4, ELISA), and efferocytosis of apoptotic bronchial epithelial cells (flow cytometry) in bronchoalveolar lavage (BAL) and peripheral blood from 75 lung transplant recipients, comprising 16 with stable graft function, 34 stable with proven infection, 25 with BOS, and 14 healthy controls.

RESULTS

In plasma, MBL levels were highly variable (0-17.538 μg/ml), but increased in infected patients vs control (p = 0.09) or stable groups (p = 0.003). There was a similar increase in UC4 in infected patients and a significant correlation between MBL and UC4. There was no correlation between MBL and time after transplant. In BAL, MBL levels were less variable (0-73.3 ng/ml) and significantly reduced in patients with BOS vs controls and stable groups. Efferocytosis was significantly reduced in the BOS group vs control and stable groups (mean [SEM] control, 20% [1.3%]; stable, 20.5% [2.5%]; infected, 17.3% [2.8%]; BOS, 11.3% [1.5%], p = 0.04).

CONCLUSIONS

Low levels of MBL in the airway may play a role in reduced efferocytosis, subsequent tissue damage, and BOS after lung transplantation.

Complement deficiency states and associated infections

A major function of the immune system is to protect the host from microbial infections. The complement system plays important roles in both the innate and the adaptive immune defense and also acts as a bridge between these arms of immunity. This is obvious from complement deficiencies which in varying degree, depending on which factor is missing, are associated with increased infection susceptibility and also increased risk for other, mainly autoimmune diseases. Genetically determined deficiencies are described for almost all complement proteins but the consequences show a wide variation. Here the genetic defects and molecular abnormalities in complement deficient persons, related clinically relevant infections and the options for prevention and therapy are reviewed. The roles of complement in host defense against common infections are also discussed.

High-dose mannose-binding lectin therapy for Ebola virus infection

Mannose-binding lectin (MBL) targets diverse microorganisms for phagocytosis and complement-mediated lysis by binding specific surface glycans. Although recombinant human MBL (rhMBL) trials have focused on reconstitution therapy, safety studies have identified no barriers to its use at higher levels. Ebola viruses cause fatal hemorrhagic fevers for which no treatment exists and that are feared as potential biothreat agents. We found that mice whose rhMBL serum concentrations were increased ≥7-fold above average human levels survived otherwise fatal Ebola virus infections and became immune to virus rechallenge. Because Ebola glycoproteins potentially model other glycosylated viruses, rhMBL may offer a novel broad-spectrum antiviral approach.

Recombinant chimeric lectins consisting of mannose-binding lectin and L-ficolin are potent inhibitors of influenza A virus compared with mannose-binding lectin

MBL structurally contains a type II-like collagenous domain and a carbohydrate recognition domain (CRD). We have recently generated three novel recombinant chimeric lectins (RCL), in which varying length of collagenous domain of mannose-binding lectin (MBL) is replaced with that of L-ficolin (L-FCN). CRD of MBL is used for target recognition because it has a broad spectrum in pathogen recognition compared with L-FCN. Results of our study demonstrate that these RCLs are potent inhibitors of influenza A virus (IAV). RCLs, against IAV, show dose-dependent activation of the lectin complement pathway, which is significantly higher than that of recombinant human MBL (rMBL). This activity is observed even without MBL-associated serine proteases (MASPs, provided by MBL deficient mouse sera), which have been thought to mediate complement activation. These observations suggest that RCLs are more efficient in associating with MASP-2, which predominantly mediates the activity. Yet, additional serum further increases the activity while RCL-mediated coagulation-like enzyme activities are diminished compared with rMBL, suggesting reduced association with MASP-1, which has been shown to mediate coagulation-like activity. These data suggest that RCLs may interfere less with host coagulation, which is advantageous to be a therapeutic drug. Importantly, these RCLs have surpassed rMBL for anti-viral activities, such as viral aggregation, reduction of viral hemagglutination (HA) and inhibition of virus-mediated HA and neuraminidase (NA) activities. These results are encouraging that novel RCLs could be used as anti-IAV agents with less side effect and that RCLs would be suitable candidates in developing a new anti-IAV therapy.

Infections of people with complement deficiencies and patients who have undergone splenectomy

The complement system comprises several fluid-phase and membrane-associated proteins. Under physiological conditions, activation of the fluid-phase components of complement is maintained under tight control and complement activation occurs primarily on surfaces recognized as "nonself" in an attempt to minimize damage to bystander host cells. Membrane complement components act to limit complement activation on host cells or to facilitate uptake of antigens or microbes "tagged" with complement fragments. While this review focuses on the role of complement in infectious diseases, work over the past couple of decades has defined several important functions of complement distinct from that of combating infections. Activation of complement in the fluid phase can occur through the classical, lectin, or alternative pathway. Deficiencies of components of the classical pathway lead to the development of autoimmune disorders and predispose individuals to recurrent respiratory infections and infections caused by encapsulated organisms, including Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. While no individual with complete mannan-binding lectin (MBL) deficiency has been identified, low MBL levels have been linked to predisposition to, or severity of, several diseases. It appears that MBL may play an important role in children, who have a relatively immature adaptive immune response. C3 is the point at which all complement pathways converge, and complete deficiency of C3 invariably leads to severe infections, including those caused by meningococci and pneumococci. Deficiencies of the alternative and terminal complement pathways result in an almost exclusive predisposition to invasive meningococcal disease. The spleen plays an important role in antigen processing and the production of antibodies. Splenic macrophages are critical in clearing opsonized encapsulated bacteria (such as pneumococci, meningococci, and Escherichia coli) and intraerythrocytic parasites such as those causing malaria and babesiosis, which explains the fulminant nature of these infections in persons with anatomic or functional asplenia. Paramount to the management of patients with complement deficiencies and asplenia is educating patients about their predisposition to infection and the importance of preventive immunizations and seeking prompt medical attention.

Impact of mannose-binding lectin insufficiency on the course of cystic fibrosis: A review and meta-analysis

Mannose-binding lectin (MBL) is an innate immune protein produced by the liver. MBL binds to glycoconjugates containing mannose, fucose or N-acetylglucosamine that are present in a wide variety of bacteria, viruses and fungi. Upon binding, MBL may active the lectin pathway of complement or directly opsonize organisms to enhance phagocytosis. MBL is primarily a serum protein but accumulates in the lung during acute inflammation. Recent evidence suggests an important role for MBL in a variety of infectious disorders. Cystic fibrosis (CF) is a multisystem disease caused by mutations in the gene encoding the CF transmembrane regulator (CFTR). The course of CF lung disease is highly variable even in patients with the same CFTR genotype, suggesting that other modulator genes are important for prognosis. MBL has been proposed as a possible modulator of clinical severity in CF. In this review and meta-analysis, we found that MBL2 genotypes associated with MBL insufficiency were associated with earlier acquisition of Pseudomonas aeruginosa (P < 0.0001), reduced pulmonary function among adult patients (P < 0.0001 for forced expiratory volume), and an increased rate of death or requirement for lung transplantation (odds ratio 3.69; P = 0.02). The available evidence therefore suggests that MBL insufficiency is associated with the severity of CF lung disease. The possible future prophylactic or therapeutic application of MBL replacement is discussed.

Recombinant human complement component C2 produced in a human cell line restores the classical complement pathway activity in-vitro: an alternative treatment for C2 deficiency diseases

Background

Complement C2 deficiency is the most common genetically determined complete complement deficiency and is associated with a number of diseases. Most prominent are the associations with recurrent serious infections in young children and the development of systemic lupus erythematosus (SLE) in adults. The links with these diseases reflect the important role complement C2 plays in both innate immunity and immune tolerance. Infusions with normal fresh frozen plasma for the treatment of associated disease have demonstrated therapeutic effects but so far protein replacement therapy has not been evaluated.

Results

Human complement C2 was cloned and expressed in a mammalian cell line. The purity of recombinant human C2 (rhC2) was greater than 95% and it was characterized for stability and activity. It was sensitive to C1s cleavage and restored classical complement pathway activity in C2-deficient serum both in a complement activation ELISA and a hemolytic assay. Furthermore, rhC2 could increase C3 fragment deposition on the human pathogen Streptococcus pneumoniae in C2-deficient serum to levels equal to those with normal serum.

Conclusions

Taken together these data suggest that recombinant human C2 can restore classical complement pathway activity and may serve as a potential therapeutic for recurring bacterial infections or SLE in C2-deficient patients.

A novel L-ficolin/mannose-binding lectin chimeric molecule with enhanced activity against Ebola virus

Ebola viruses constitute a newly emerging public threat because they cause rapidly fatal hemorrhagic fevers for which no treatment exists, and they can be manipulated as bioweapons. We targeted conserved N-glycosylated carbohydrate ligands on viral envelope surfaces using novel immune therapies. Mannose-binding lectin (MBL) and L-ficolin (L-FCN) were selected because they function as opsonins and activate complement. Given that MBL has a complex quaternary structure unsuitable for large scale cost-effective production, we sought to develop a less complex chimeric fusion protein with similar ligand recognition and enhanced effector functions. We tested recombinant human MBL and three L-FCN/MBL variants that contained the MBL carbohydrate recognition domain and varying lengths of the L-FCN collagenous domain. Non-reduced chimeric proteins formed predominantly nona- and dodecameric oligomers, whereas recombinant human MBL formed octadecameric and larger oligomers. Surface plasmon resonance revealed that L-FCN/MBL76 had the highest binding affinities for N-acetylglucosamine-bovine serum albumin and mannan. The same chimeric protein displayed superior complement C4 cleavage and binding to calreticulin (cC1qR), a putative receptor for MBL. L-FCN/MBL76 reduced infection by wild type Ebola virus Zaire significantly greater than the other molecules. Tapping mode atomic force microscopy revealed that L-FCN/MBL76 was significantly less tall than the other molecules despite similar polypeptide lengths. We propose that alterations in the quaternary structure of L-FCN/MBL76 resulted in greater flexibility in the collagenous or neck region. Similarly, a more pliable molecule might enhance cooperativity between the carbohydrate recognition domains and their cognate ligands, complement activation, and calreticulin binding dynamics. L-FCN/MBL chimeric proteins should be considered as potential novel therapeutics.

Sepsis in acute myeloid leukaemia patients receiving high-dose chemotherapy: no impact of chitotriosidase and mannose-binding lectin polymorphisms

Infections after chemotherapy often cause significant morbidity in patients with acute myeloid leukaemia (AML). Chitotriosidase (CHIT) and mannose-binding lectin (MBL) are part of the innate immune system. Polymorphism in the CHIT-coding gene (CHIT1) may be associated with Gram-negative sepsis in children with AML, and polymorphism in the MBL-coding gene (MBL2) seems to modify the risk of infections in several patient groups. The purpose of this study was to investigate the possible associations between polymorphisms in CHIT1, MBL2 and sepsis in adult patients treated with high-dose chemotherapy for AML. We included 190 patients treated with 526 cycles of chemotherapy. The follow-up period was 6 months from the diagnosis of AML. Prophylactic antibiotics were not used. We identified 604 febrile episodes with 246 episodes of sepsis. Thirty-two patients (17%) either died from infection or infection was a major concomitant factor for death. No significant associations between CHIT1 polymorphism and sepsis (P = 0.85) or death caused by sepsis (P = 0.14) were found. Furthermore, no significant associations between MBL2 polymorphism and sepsis (P = 0.76) or death caused by sepsis (P = 0.24) were observed. The severe and long-lasting neutropenia and mucositis after chemotherapy may explain why the MBL system does not protect against sepsis in patients with AML. Replacement therapy with recombinant MBL is not likely to decrease the risk of sepsis in patients with AML.

Genetically-defined deficiency of mannose-binding lectin is associated with protection after experimental stroke in mice and outcome in human stroke

BACKGROUND

The complement system is a major effector of innate immunity that has been involved in stroke brain damage. Complement activation occurs through the classical, alternative and lectin pathways. The latter is initiated by mannose-binding lectin (MBL) and MBL-associated serine proteases (MASPs). Here we investigated whether the lectin pathway contributes to stroke outcome in mice and humans.

METHODOLOGY/PRINCIPAL FINDINGS

Focal cerebral ischemia/reperfusion in MBL-null mice induced smaller infarctions, better functional outcome, and diminished C3 deposition and neutrophil infiltration than in wild-type mice. Accordingly, reconstitution of MBL-null mice with recombinant human MBL (rhMBL) enhanced brain damage. In order to investigate the clinical relevance of these experimental observations, a study of MBL2 and MASP-2 gene polymorphism rendering the lectin pathway dysfunctional was performed in 135 stroke patients. In logistic regression adjusted for age, gender and initial stroke severity, unfavourable outcome at 3 months was associated with MBL-sufficient genotype (OR 10.85, p = 0.008) and circulating MBL levels (OR 1.29, p = 0.04). Individuals carrying MBL-low genotypes (17.8%) had lower C3, C4, and CRP levels, and the proinflammatory cytokine profile was attenuated versus MBL-sufficient genotypes.

CONCLUSIONS/SIGNIFICANCE

In conclusion, genetically defined MBL-deficiency is associated with a better outcome after acute stroke in mice and humans.