The role of mannose-binding lectin (MBL) in diabetic retinopathy: A scoping review.

Diabetes mellitus (DM) is a chronic systemic disease characterized by a multifactorial nature, which may lead to several macro and microvascular complications. Diabetic retinopathy (DR) is one of the most severe microvascular complications of DM, which can result in permanent blindness. The mechanisms involved in the pathogenesis of DR are multiple and still poorly understood. Factors such as dysregulation of vascular regeneration, oxidative and hyperosmolar stress in addition to inflammatory processes have been associated with the pathogenesis of DR. Furthermore, compelling evidence shows that components of the immune system, including the complement system, play a relevant role in the development of the disease. Studies suggest that high concentrations of mannose-binding lectin (MBL), an essential component of the complement lectin pathway, may contribute to the development of DR in patients with DM. This review provides an update on the possible role of the complement system, specifically the lectin pathway, in the pathogenesis of DR and discusses the potential of MBL as a non-invasive biomarker for both, the presence and severity of DR, in addition to its potential as a therapeutic target for intervention strategies.

Inhibition of vertebrate complement system by hematophagous arthropods: inhibitory molecules, mechanisms, physiological roles, and applications.

In arthropods, hematophagy has arisen several times throughout evolution. This specialized feeding behavior offered a highly nutritious diet obtained during blood feeds. On the other hand, blood-sucking arthropods must overcome problems brought on by blood intake and digestion. Host blood complement acts on the bite site and is still active after ingestion, so complement activation is a potential threat to the host's skin feeding environment and to the arthropod gut enterocytes. During evolution, blood-sucking arthropods have selected, either in their saliva or gut, anticomplement molecules that inactivate host blood complement. This review presents an overview of the complement system and discusses the arthropod's salivary and gut anticomplement molecules studied to date, exploring their mechanism of action and other aspects related to the arthropod-host-pathogen interface. The possible therapeutic applications of arthropod's anticomplement molecules are also discussed.

Complement System Inhibitory Drugs in a Zebrafish (Danio rerio) Model: Computational Modeling.

The dysregulation of complement system activation usually results in acute or chronic inflammation and can contribute to the development of various diseases. Although the activation of complement pathways is essential for innate defense, exacerbated activity of this system may be harmful to the host. Thus, drugs with the potential to inhibit the activation of the complement system may be important tools in therapy for diseases associated with complement system activation. The synthetic peptides Cp40 and PMX205 can be highlighted in this regard, given that they selectively inhibit the C3 and block the C5a receptor (C5aR1), respectively. The zebrafish (Danio rerio) is a robust model for studying the complement system. The aim of the present study was to use in silico computational modeling to investigate the hypothesis that these complement system inhibitor peptides interact with their target molecules in zebrafish, for subsequent in vivo validation. For this, we analyzed molecular docking interactions between peptides and target molecules. Our study demonstrated that Cp40 and the cyclic peptide PMX205 have positive interactions with their respective zebrafish targets, thus suggesting that zebrafish can be used as an animal model for therapeutic studies on these inhibitors.

Complement System Activation Is a Plasma Biomarker Signature during Malaria in Pregnancy.

Malaria in pregnancy (MiP) is a public health problem in malaria-endemic areas, contributing to detrimental outcomes for both mother and fetus. Primigravida and second-time mothers are most affected by severe anemia complications and babies with low birth weight compared to multigravida women. Infected erythrocytes (IE) reach the placenta, activating the immune response by placental monocyte infiltration and inflammation. However, specific markers of MiP result in poor outcomes, such as low birth weight, and intrauterine growth restriction for babies and maternal anemia in women infected with Plasmodium falciparum are limited. In this study, we identified the plasma proteome signature of a mouse model infected with Plasmodium berghei ANKA and pregnant women infected with Plasmodium falciparum infection using quantitative mass spectrometry-based proteomics. A total of 279 and 249 proteins were quantified in murine and human plasma samples, of which 28% and 30% were regulated proteins, respectively. Most of the regulated proteins in both organisms are involved in complement system activation during malaria in pregnancy. CBA anaphylatoxin assay confirmed the complement system activation by the increase in C3a and C4a anaphylatoxins in the infected plasma compared to non-infected plasma. Moreover, correlation analysis showed the association between complement system activation and reduced head circumference in newborns from Pf-infected mothers. The data obtained in this study highlight the correlation between the complement system and immune and newborn outcomes resulting from malaria in pregnancy.

Hyper-inflammation and complement in COVID-19.

COVID-19 is a complex disease manifesting in a broad severity spectrum and involving distinct organs and systems. Hyperinflammation, including complement over-activation, has a pivotal role in severe COVID-19 pathobiology, stimulating the inflammatory response, causing microangiopathy, platelet-neutrophil activation, and hypercoagulability. SARS-CoV-2 can directly activate the complement system by the classic, alternative, and lectin pathways, and infected cells can produce intracellular complement (the complesome). COVID-19 severity appears to be associated with the degree of complement activation, and it has been hypothesized that patients with COVID-19 may benefit from therapeutic complement inhibition. Different complement cascade molecules may be targeted with potential advantages and disadvantages. Which target(s) is the most effective and when is the best timing for intervention remain open questions. Early phase I and phase II clinical trials have shown promising but conflicting results, warranting phase III controlled randomized trials. Upstream complement inhibition appears to better and more effectively block hyperinflammation with potential clinical significance. Understanding how SARS-CoV-2 exploits the complement system can add precious information about the pathogenesis of other infections, inflammatory, and autoimmune diseases beyond COVID-19.

Relationship between the expression of complement inhibitory proteins and therapeutic efficacy of antibodies in breast cancer.

Complement regulatory proteins (mCRPs) CD55, CD46 and CD59 have been proposed as key elements in therapeutic resistance against cancer. mCRP-expressing tumor cells, in addition to hindering trastuzumab, pertuzumab and sacituzumab-govitecan therapeutic activity in breast cancer, can regulate biological processes that promote tumor progression. This review describes the structure of mCRPs and analyzes their expression using transcriptomic databases from breast cancer patients, in addition to collecting information on mCRPs interactions and signaling in tumor cells. Given that mCRPs are relevant targets, several strategies that have been explored for their inhibition and regulation in order to increase therapeutic efficacy and prevent cancer resistance and progression are described.

Se ha propuesto a las proteínas reguladoras de complemento (mCRP) CD55, CD46 y CD59 como piezas clave en la resistencia terapéutica contra el cáncer. Las células tumorales que expresan las mCRP, además de obstaculizar la actividad terapéutica de trastuzumab, pertuzumab y sacituzumab-govitecan en cáncer de mama, pueden regular procesos biológicos que promueven la progresión tumoral. Esta revisión describe la estructura de las mCRP y analiza su expresión a partir de bases de datos transcriptómicos de pacientes con cáncer de mama; también recopila información de interacciones y señalización de las mCRP en células tumorales. Dado que estas mCRP son dianas relevantes, se describen diversas estrategias para su inhibición y regulación para incrementar la eficacia terapéutica y evitar la resistencia y progresión del cáncer.

Atypical hemolytic uremic syndrome in the Colombian Caribbean: its particular characteristics.

INTRODUCTION: Atypical hemolytic uremic syndrome (aHUS) is a rare and genetically mediated systemic disease most often caused by uncontrolled and chronic complement activation that leads to systemic thrombotic microangiopathy, renal and extra-renal damage. MATERIALS AND METHODS: This is descriptive, retrospective and multicenter study, which reports demographic, clinical, laboratory, and genetic characteristics, as well as their treatment response and outcome of 20 aHUS patients diagnosed between 2014 and 2018. RESULTS: Most patients were female adults (75%) and 30% were associated to pregnancy/postpartum, 15% to autoimmune disease, and 65% to infections. Gastrointestinal involvement (75%) was the most frequent extra-renal organ damage. Antenatal mortality and mortality rate were 5% and 10%, respectively. 25% of the patients progressed to end-stage renal disease. In 4/8 of patients treated within 1 week of presentation, eculizumab treatment restored multi-organ function after 4 weeks of treatment. CFH (37%) and CFI (25%) mutations were the most frequent. CONCLUSION: This is the first series of aHUS cases of Colombian Caribbean region which reports the clinical and epidemiological characteristics of this condition in this region.

Dialysis-related thrombocytopenia: a case report.

Thrombocytopenia is frequently observed in hemodialysis patients, and its correct investigation and control remain a challenge. It is estimated that during the hemodialysis session there is a drop of up to 15% in the platelet count, with recovery after the end of treatment. This reduction in platelets is due to platelet adhesion and complement activation, regardless of the membrane material. Several studies with platelet surface markers demonstrate increased platelet activation and aggregation secondary to exposure to cardiopulmonary bypass. This case report describes a patient on hemodialysis who developed severe thrombocytopenia during hospitalization. Investigation and exclusion of the most common causes were carried out: heparin-related thrombocytopenia, adverse drug reaction, hypersplenism, and hematological diseases. Afterwards, the possibility of hemodialysis-related thrombocytopenia was raised, since the fall was accentuated during the sessions with partial recovery after the dialyzer change. Attention to the sterilization method and dialyzer reuse must be considered for correction. In the current case, reusing the dialyzer minimized the drop in platelet counts associated with hemodialysis.

Methodological Appraisal of Literature Concerning the Analysis of Genetic Variants or Protein Levels of Complement Components on Susceptibility to Infection by Trypanosomatids: A Systematic Review.

Background: Trypanosomatids are protozoa responsible for a wide range of diseases, with emphasis on Chagas Disease (CD) and Leishmaniasis, which are in the list of most relevant Neglected Tropical Diseases (NTD) according to World Health Organization (WHO). During the infectious process, immune system is immediately activated, and parasites can invade nucleated cells through a broad diversity of receptors. The complement system - through classical, alternative and lectin pathways - plays a role in the first line of defense against these pathogens, acting in opsonization, phagocytosis and lysis of parasites. Genetic modifications in complement genes, such as Single Nucleotide Polymorphisms (SNPs), can influence host susceptibility to these parasites and modulate protein expression. Methods: In March and April 2021, a literature search was conducted at the PubMed and Google Scholar databases and the reference lists obtained were verified. After applying the inclusion and exclusion criteria, the selected studies were evaluated and scored according to eleven established criteria regarding their thematic approach and design, aiming at the good quality of publications. Results: Twelve papers were included in this systematic review: seven investigating CD and five focusing on Leishmaniasis. Most articles presented gene and protein approaches, careful determination of experimental groups, and adequate choice of experimental techniques, although several of them were not up-to-date. Ten studies explored the association of polymorphisms and haplotypes with disease progression, with emphasis on lectin complement pathway genes. Decreased and increased patient serum protein levels were associated with susceptibility to CD and Visceral Leishmaniasis, respectively. Conclusion: This systematic review shows the influence of genetic alterations in complement genes on the progression of several infectious diseases, with a focus on conditions caused by trypanosomatids, and contributes suggestions and evidence to improve experimental design in future research proposals.

Complement-Mediated Differential Immune Response of Human Macrophages to Sporothrix Species Through Interaction With Their Cell Wall Peptidorhamnomannans.

In this study, the human immune response mechanisms against Sporothrix brasiliensis and Sporothrix schenckii, two causative agents of human and animal sporotrichosis, were investigated. The interaction of S. brasiliensis and S. schenckii with human monocyte-derived macrophages (hMDMs) was shown to be dependent on the thermolabile serum complement protein C3, which facilitated the phagocytosis of Sporothrix yeast cells through opsonization. The peptidorhamnomannan (PRM) component of the cell walls of these two Sporothrix yeasts was found to be one of their surfaces exposed pathogen-associated molecular pattern (PAMP), leading to activation of the complement system and deposition of C3b on the Sporothrix yeast surfaces. PRM also showed direct interaction with CD11b, the specific component of the complement receptor-3 (CR3). Furthermore, the blockade of CR3 specifically impacted the interleukin (IL)-1ß secretion by hMDM in response to both S. brasiliensis and S. schenckii, suggesting that the host complement system plays an essential role in the inflammatory immune response against these Sporothrix species. Nevertheless, the structural differences in the PRMs of the two Sporothrix species, as revealed by NMR, were related to the differences observed in the host complement activation pathways. Together, this work reports a new PAMP of the cell surface of pathogenic fungi playing a role through the activation of complement system and via CR3 receptor mediating an inflammatory response to Sporothrix species.

Adaptations to haematophagy: Investigations on how male and female Culex quinquefasciatus (Diptera: Culicidae) deal with human complement activation after a blood meal.

Culex quinquefasciatus is a mosquito species with an anthropophilic habit, often associated with areas with poor sanitation in tropical and urban regions. Adult males and females feed on sugars but only females feed on blood in natural conditions for egg maturation. During haematophagy, female C. quinquefasciatus transmit pathogens such as the West Nile virus, Oropouche virus, various encephalitis viruses, and Wuchereria bancrofti to human hosts. It has been observed in laboratory conditions that male C. quinquefasciatus may feed on blood during an artificial feed. Experiments were carried out to understand how males and females of this species deal with human complement activation. Our results showed that female C. quinquefasciatus, but not males, withstand the stress caused by the ingestion of normal human serum. It was observed that the salivary gland extracts from female mosquitoes were able to inhibit the classical and lectin pathways, whereas male salivary gland extracts only inhibited the lectin pathway. The male and female intestinal contents inhibited the classical and lectin pathways. Neither the salivary glands nor the intestinal contents from males and females showed inhibitory activity towards the alternative pathway. However, the guts of male and female C. quinquefasciatus captured factor H from the human serum, permitting C3b inactivation to its inactive form iC3b, and preventing the formation of the C3 convertase. The activity of the antioxidant enzyme catalase is similar in C. quinquefasciatus females and males. This article shows for the first time that males from a haematophagous arthropod species present human anti-complement activity in their salivary gland extracts and gut contents. The finding of an activity that helps to protect the damage caused by blood ingestion in sugar-feeding male mosquitoes suggests that this may be a pre-adaptation to blood-feeding.

Complement System in Alcohol-Associated Liver Disease.

Innate immunity contributes effectively to the development of Alcohol-Associated liver disease (ALD). Particularly, human studies and murine models of ALD have shown that Complement activation plays an important role during the initial and later stages of ALD. The Complement System may contribute to the pathogenesis of this disease since it has been shown that ethanol-derived metabolic products activate the Complement cascade on liver membranes, leading to hepatocellular damage. However, studies evaluating the plasma levels of Complement proteins in ALD patients present contradictory results in some cases, and do not establish a well-marked role for each Complement component. The impairment of leukocyte chemoattractant activity observed in these patients may contribute to the susceptibility to bacterial infections in the latter stages of the disease. On the other hand, murine models of ALD have provided more detailed insights into the mechanisms that link the Complement System to the pathogenesis of the disease. It has been observed that Classical pathway can be activated via C1q binding to apoptotic cells in the liver and contributes to the development of hepatic inflammation. C3 contributes to the accumulation of triglycerides in the liver and in adipose tissue, while C5 seems to be involved with inflammation and liver injury after chronic ethanol consumption. In this review, we present a compendium of studies evaluating the role of Complement in human and murine models of ALD. We also discuss potential therapies to human ALD, highlighting the use of Complement inhibitors.

C5a-C5aR1 Axis Activation Drives Envenomation Immunopathology by the Snake Naja annulifera.

Systemic complement activation drives a plethora of pathological conditions, but its role in snake envenoming remains obscure. Here, we explored complement's contribution to the physiopathogenesis of Naja annulifera envenomation. We found that N. annulifera venom promoted the generation of C3a, C4a, C5a, and the soluble Terminal Complement Complex (sTCC) mediated by the action of snake venom metalloproteinases. N. annulifera venom also induced the release of lipid mediators and chemokines in a human whole-blood model. This release was complement-mediated, since C3/C3b and C5a Receptor 1 (C5aR1) inhibition mitigated the effects. In an experimental BALB/c mouse model of envenomation, N. annulifera venom promoted lipid mediator and chemokine production, neutrophil influx, and swelling at the injection site in a C5a-C5aR1 axis-dependent manner. N. annulifera venom induced systemic complementopathy and increased interleukin and chemokine production, leukocytosis, and acute lung injury (ALI). Inhibition of C5aR1 with the cyclic peptide antagonist PMX205 rescued mice from these systemic reactions and abrogated ALI development. These data reveal hitherto unrecognized roles for complement in envenomation physiopathogenesis, making complement an interesting therapeutic target in envenomation by N. annulifera and possibly by other snake venoms.

A double edged-sword - The Complement System during SARS-CoV-2 infection.

In the past 20 years, infections caused by coronaviruses SARS-CoV, MERS-CoV and SARS-CoV-2 have posed a threat to public health since they may cause severe acute respiratory syndrome (SARS) in humans. The Complement System is activated during viral infection, being a central protagonist of innate and acquired immunity. Here, we report some interactions between these three coronaviruses and the Complement System, highlighting the central role of C3 with the severity of these infections. Although it can be protective, its role during coronavirus infections seems to be contradictory. For example, during SARS-CoV-2 infection, Complement System can control the viral infection in asymptomatic or mild cases; however, it can also intensify local and systemic damage in some of severe COVID-19 patients, due to its potent proinflammatory effect. In this last condition, the activation of the Complement System also amplifies the cytokine storm and the pathogenicity of coronavirus infection. Experimental treatment with Complement inhibitors has been an enthusiastic field of intense investigation in search of a promising additional therapy in severe COVID-19 patients.

Selective decrease in complement C2 hemolytic activity is a sensitive marker for cryoglobulinemia and active disease in hepatitis C patients.

BACKGROUND: Some HCV patients present low/non-detected C2 hemolytic activity (C2h) without apparent consumption of other Complement components (selective low/non-detected C2h). AIM: Characterization of the immunologic/clinical basis of this phenomenon. METHODS: C2h, HCV-viral load, cryoglobulinemia and Complement components were determined in 726 HCV patients, with sequential C2h determination in 189 patients. RESULTS: C2h was non-detected in 15.9%, low in 16.9% and normal in 67.2% subjects and showed temporal oscillation in 30.7% of patients. Samples with selective non-detected C2h presented lower C3/C4 than those with normal C2h, but still within the normal C3/C4 range. Selective non-detected C2h was associated with higher aspartate aminotransferase (AST) (p<0.001), alanine transferase (ALT) (p = 0.03) and APRI (Aspartate aminotransferase-to-Platelet Ratio Index) (p<0.001), lower serum albumin (p = 0.01) and platelet count (p = 0.012), more individuals at pre-treatment stage, with detectable HCV-RNA p<0.001), cryoglobulinemia (p<0.001) and with HCV genotype 3 (p = 0.003). Elevated ALT, HCV genotype 3, active disease and viral load were independent predictors of low/non-detected C2h. In vitro exposure of normal serum to exogenous HCV cryoglobulins caused dose-dependent decrease in C2h. CONCLUSIONS: Selective C2h decrease is a sensitive marker of Complement activation in HCV patients and is associated with cryoglobulinemia, active disease, elevated ALT, higher viral load, and HCV genotype 3.

Insights into the role of complement system in the pathophysiology of endometriosis.

Endometriosis (EM) is a gynecologic disorder characterized by the presence of endometrium-like tissue outside of normal location that affects up to 10 % of all women in reproductive age. The pathogenesis of endometriosis is not completely known. The relationship between complement and EM has already been demonstrated in some studies, indicating an important role in the pathophysiology of the disease, however, researches are scarce and sometimes controversial. The objective of this review is to bring state-of-the-art knowledge on the subject and promote better understanding of the complement system role in the pathophysiology of EM. We searched in databases up to December 2020 and found 1213 articles that were screened, from which were selected 54 articles from title and abstract. We found that there is a dysfunction of the immune system on endometriosis, including the complement system. Apparently, the complement system is dysregulated in endometriosis and several proteins of the three complement pathways presented serum levels altered in women with endometriosis compared with those without the disease. The most studied protein is C3. Future investigations on the innate immune response and complement system could offer a further understanding on the inflammatory pathogenesis of EM, which will support a new therapeutic plan.

Is It Possible to Intervene in the Capacity of Trypanosoma cruzi to Elicit and Evade the Complement System?

Chagas' disease is a zoonotic parasitic ailment now affecting more than 6 million people, mainly in Latin America. Its agent, the protozoan Trypanosoma cruzi, is primarily transmitted by endemic hematophagous triatomine insects. Transplacental transmission is also important and a main source for the emerging global expansion of this disease. In the host, the parasite undergoes intra (amastigotes) and extracellular infective (trypomastigotes) stages, both eliciting complex immune responses that, in about 70% of the cases, culminate in permanent immunity, concomitant with the asymptomatic presence of the parasite. The remaining 30% of those infected individuals will develop a syndrome, with variable pathological effects on the circulatory, nervous, and digestive systems. Herein, we review an important number of T. cruzi molecules, mainly located on its surface, that have been characterized as immunogenic and protective in various experimental setups. We also discuss a variety of parasite strategies to evade the complement system - mediated immune responses. Within this context, we also discuss the capacity of the T. cruzi infective trypomastigote to translocate the ER-resident chaperone calreticulin to its surface as a key evasive strategy. Herein, it is described that T. cruzi calreticulin inhibits the initial stages of activation of the host complement system, with obvious benefits for the parasite. Finally, we speculate on the possibility to experimentally intervene in the interaction of calreticulin and other T. cruzi molecules that interact with the complement system; thus resulting in significant inhibition of T. cruzi infectivity.

Glomerular endothelial activation, C4d deposits and microangiopathy in immunoglobulin A nephropathy.

Immunoglobulin A nephropathy (IgAN) is considered as mesangiopathy since it initiates in the mesangium; however, other glomerular components are involved and the glomerular capillary wall offers the first contact to circulating macromolecular IgA1. Acute and active forms of IgAN are associated with endocapillary hypercellularity and vascular damage of various degrees, in severe cases with microangiopathy (MA) without or with thrombosis [thrombotic microangiopathy (TMA)]. Vascular damage activates complement and coagulation cascades. A defective complement regulation has recently been detected in active and progressive cases of IgAN. C4d deposits in renal biopsies have been found to be an early risk factor. These observations have raised interest in manifestation of MA and TMA in progressive cases of IgAN. MA-TMA lesions have been found in various percentages (2-53%) of patients with IgAN according to patients' selection and pathology definition of TMA. The association with hypertension (HTN) was so strong that it led to the hypothesis that MA/TMA in IgAN was a mere consequence of severe HTN. Old and new clinical and experimental data indicate that in IgAN the interaction of the glomerular capillary wall with immune reactants and complement uncontrolled activation leading to C4b deposits favours the development of MA-TMA, which plays a role in progression and renal function decline. The central role of complement activation is relevant also for the new therapeutic interventions offered by the pharma.

Alternative complement pathway activation in thrombotic microangiopathy associated with lupus nephritis.

INTRODUCTION/OBJECTIVE: Thrombotic microangiopathy (TMA) in systemic lupus erythematosus is a rare manifestation associated with activation of the complement system. This study aimed to compare plasma and urine complement activation products between patients with active lupus nephritis (aLN) and those with acute TMA plus concomitant active LN (aTMA+aLN). METHODS: Plasma and urine samples were obtained from 20 patients with aTMA+aLN, 20 patients with aLN matched by the histological activity index, 5 patients with chronic TMA, 20 patients with inactive LN, and 10 kidney donors. Complement fragments C3a, C4a, C4d, Ba, C5a, C5bC9, and factor H were determined by ELISA; and kidney C4d deposition was detected by immunohistochemistry. Patients were followed for > 12 months and complement activation products re-measured after treatment in 10 aTMA+aLN patients. RESULTS: Both aTMA+aLN and aLN groups had increased circulating C3a, Ba, and C5bC9; and decreased circulating C3, C4, C4a, C4d, and factor H. Urinary C3a, C5a, Ba, and C5bC9 were higher in patients with aTMA+aLN than in aLN. After treatment, levels of circulating C3, C4, and factor H increased; while levels of urinary C3a, C5a, Ba, and C5bC9 decreased in patients with aTMA+aLN. These changes were observed at each aTMA episode in two patients studied during repeated TMA episodes. There was no difference in C4d deposition in glomerular capillaries, tubular basement membrane, peritubular capillaries, and arterioles between patients with aLN and those aTMA+aLN. CONCLUSIONS: Circulating and urine complement activation products suggest that thrombotic microangiopathy associated with LN is mediated through activation of the alternative complement pathway. Key Points • Immune-complex kidney disease in systemic lupus erythematosus (SLE) is associated with activation of the classical, lectin, and alternative complement pathways • Indirect evidence from measurement of circulating and urinary complement pathway activation products suggests that renal acute thrombotic microangiopathy in SLE is mediated by activation of the alternative complement pathway • C4d kidney immunohistochemistry may be positive in both immune complex nephritis and thrombotic microangiopathy. Therefore, it is not a specific marker of renal thrombotic microangiopathy in SLE.

P-MAPA, a Fungi-Derived Immunomodulatory Compound, Induces a Proinflammatory Response in a Human Whole Blood Model.

P-MAPA is a complex compound, derived from Aspergillus oryzae cultures, that has shown immunomodulatory properties in infection and cancer animal models. Despite promising results in these models, the mechanisms of cellular activation by P-MAPA, suggested to be Toll-like receptor- (TLR-) dependent, and its effect on human immune cells, remain unclear. Using an ex vivo model of human whole blood, the effects of P-MAPA on complement system activation, production of cytokines, and the expression of complement receptors (CD11b, C5aR, and C3aR), TLR2, TLR4, and the coreceptor CD14 were analyzed in neutrophils and monocytes. P-MAPA induced complement activation in human blood, detected by increased levels of C3a, C5a, and SC5b-9 in plasma. As a consequence, CD11b expression increased and C5aR decreased upon activation, while C3aR expression remained unchanged in leukocytes. TLR2 and TLR4 expressions were not modulated by P-MAPA treatment on neutrophils, but TLR4 expression was reduced in monocytes, while CD14 expression increased in both cell types. P-MAPA also induced the production of TNF-α, IL-8, and IL-12 and oxidative burst, measured by peroxynitrite levels, in human leukocytes. Complement inhibition with compstatin showed that P-MAPA-induced complement activation drives modulation of C5aR, but not of CD11b, suggesting that P-MAPA acts through both complement-dependent and complement-independent mechanisms. Compstatin also significantly reduced the peroxynitrite generation. Altogether, our results show that P-MAPA induced proinflammatory response in human leukocytes, which is partially mediated by complement activation. Our data contribute to elucidate the complement-dependent and complement-independent mechanisms of P-MAPA, which ultimately result in immune cell activation and in its immunomodulatory properties in infection and cancer animal models.