Preeclampsia in the Context of COVID-19: Mechanisms, Pathophysiology, and Clinical Outcomes.

The emergence of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has led to the global COVID-19 pandemic, significantly impacting the health of pregnant women. Obstetric populations, already vulnerable, face increased morbidity and mortality related to COVID-19, aggravated by preexisting comorbidities. Recent studies have shed light on the potential correlation between COVID-19 and preeclampsia (PE), a leading cause of maternal and perinatal morbidity worldwide, emphasizing the significance of exploring the relationship between these two conditions. Here, we review the pathophysiological similarities that PE shares with COVID-19, with a particular focus on severe COVID-19 cases and in PE-like syndrome cases related with SARS-CoV-2 infection. We highlight cellular and molecular mechanistic inter-connectivity between these two conditions, for example, regulation of renin-angiotensin system, tight junction and barrier integrity, and the complement system. Finally, we discuss how COVID-19 pandemic dynamics, including the emergence of variants and vaccination efforts, has shaped the clinical scenario and influenced the severity and management of both COVID-19 and PE. Continued research on the mechanisms of SARS-CoV-2 infection during pregnancy and the potential risk of developing PE from previous infections is warranted to delineate the complexities of COVID-19 and PE interactions and to improve clinical management of both conditions.

Case Report: C3 deficiency in two siblings.

The complement system, a vital component of innate immunity, consists of various proteins and pathways crucial for the recognition and elimination of pathogens. In addition, it plays a major role in the initiation of adaptive response through the opsonization of antigens, contributing to B-cell activation and memory maintenance. Deficiencies in complement proteins, particularly C3, can lead to severe and recurrent infections as well as immune complex disorders. Here, we present a case report of two siblings with total C3 deficiency resulting from compound heterozygous mutations in C3 (NM_000064.4): c.305dup; [p.Asn103GlnfsTer66] and c.1269 + 5G>T, previously unreported in C3-related diseases. Both, the index case and her sister, presented a history of recurrent infections since early childhood and one of them developed hemolytic uremic syndrome (HUS). Immunological evaluation revealed absent plasma C3 levels, decreased memory B cells, hypogammaglobulinemia, and impaired response to polysaccharide antigens. The siblings showed partial responses to antimicrobial prophylaxis and vaccination, requiring intravenous immunoglobulin replacement therapy, resulting in clinical improvement. Genetic analysis identified additional risk polymorphisms associated with atypical HUS. This case highlights the importance of comprehensive genetic and immunological evaluations in complement deficiencies, along with the potential role of immunoglobulin replacement therapy in managing associated antibody defects.

Ravulizumab in Atypical Hemolytic Uremic Syndrome: An Analysis of 2-Year Efficacy and Safety Outcomes in 2 Phase 3 Trials.

Rationale & Objective: Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy (TMA) caused by complement dysregulation. Ravulizumab is a C5i approved for the treatment of aHUS. This analysis assessed long-term outcomes of ravulizumab in adults and pediatric patients with aHUS. Study Design: This analysis reports 2-year data from 2 phase 3, single-arm studies. Setting & Participants: One study included C5i-naïve adults (NCT02949128), and the other included 2 cohorts of pediatric patients (C5i-naïve and those who switched to ravulizumab from eculizumab [pediatric switch patients]; NCT03131219). Exposure: Patients received intravenous ravulizumab every 4-8 weeks, with the dose depending on body weight. Outcomes: The primary endpoint in the studies of C5i-naïve patients was complete TMA response, which consisted of platelet count normalization, lactate dehydrogenase normalization, and ≥25% improvement in serum creatinine concentrations from baseline, at 2 consecutive assessments ≥4 weeks apart. Analytical Approach: All analyses used descriptive statistics. No formal statistical comparisons were performed. Results: In total, 86 and 92 patients were included in efficacy and safety analyses, respectively. Complete TMA response rates over 2 years were 61% and 90% in C5i-naïve adults and pediatric patients, respectively. The median increase in estimated glomerular filtration rate from baseline was maintained over 2 years in C5i-naïve adults (35 mL/min/1.73 m2) and pediatric patients (82.5 mL/min/1.73 m2). Most adverse events and serious adverse events occurred during the first 26 weeks. No meningococcal infections were reported. Improvement in the Functional Assessment of Chronic Illness Therapy - Fatigue score achieved by 26 weeks was maintained over 2 years. Limitations: Limitations were the small sample of pediatric switch patients and limited availability of genetic data. Conclusions: Long-term treatment with ravulizumab is well tolerated and associated with improved hematologic and renal parameters and quality of life in adults and pediatric patients with aHUS.

This research tested a drug called ravulizumab for the treatment of atypical hemolytic uremic syndrome (aHUS). aHUS is a rare disease that causes clots in tiny blood vessels. This can damage the kidneys and other organs. We analyzed data from 2 clinical trials in which children and adults with aHUS received ravulizumab through a tube placed in a vein (intravenous line). They received ravulizumab every 4-8 weeks depending on their weight. We found that treating patients for 2 years with ravulizumab was associated with improved blood health, kidney function, and quality of life and was well tolerated. These results support ravulizumab as a long-term treatment for people with aHUS.

C4d expression in focal segmental glomerulosclerosis.

BACKGROUND: There is a little information about of expression of C4d (complement fragment) in Focal segmental glomerulosclerosis (FSGS) subtypes. Our aim was to determine the expression of C4d in FSGS subtypes in percutaneous native renal biopsies in a second-level hospital and its correlation with clinical, biochemical and histological variables. MATERIAL AND METHODS: A retrospective study in paraffin blocks of patients with biopsy with FSGS aged 16-65 years, indistinct sex, not diabetic or obese. Immunohistochemistry was performed for C4d and their expression was analyzing in non-sclerosed glomerular capillaries (GC) and sclerosis areas (SA). Clinical and biochemical variables were recorded. The cases were divided into C4d positive and C4d negative groups and compared. The correlation between C4d staining scores in CG and SA with clinical and biochemical variables were analyzed. RESULTS: Twenty samples were analyzed, 4 for each subtype. At the time of biopsy average age 38.8 ±â€¯18.6 years, 65% male, 8.7% were hypertension. The percentage of positivity for C4d was 40% in GC, 30% SA and 35% in mesangium. The highest expression was for cellular and collapsing subtypes. C4d positivity cases had increased proteinuria (p = 0.035). A significant correlation was found between percentage of C4d expression in CG with SA (p = 0.012) and SA with tubular atrophy and interstitial fibrosis (p < 0.05). CONCLUSIONS: C4d expression in FSGS predominated in the cellular and collapsing subtypes, which translates complement activation. C4d is a possible surrogate marker in GSFS.

Clinical presentation and management of atypical hemolytic uremic syndrome in Latin America: a narrative review of the literature.

INTRODUCTION: Comprehensive information about atypical hemolytic uremic syndrome (aHUS) is relatively scarce outside of Europe and North America. This narrative review assembles available published data about the clinical presentation and management of aHUS in Latin America. AREAS COVERED: A search conducted in February 2023 of the MEDLINE (from inception), Embase (from inception), and LILACS/IBECS (1950 to 2023) databases using search terms 'atypical hemolytic uremic syndrome' and 'Latin America' and their variations retrieved 51 records (full papers and conference abstracts) published in English, Spanish, or Portuguese. After de-duplication, manual screening of titles/abstracts and addition of author-known articles, 25 articles were included of which 17 (68%) are full papers. All articles were published during the years 2013-2022. Articles include cohort studies, a registry analysis, and case reports from Argentina, Brazil, Chile and Columbia. Overall, Latin American patients with aHUS present the classic epidemiological, clinical, and genetic characteristics associated with this condition as described in other world regions. Depending on the country and time of reporting, aHUS in Latin America was treated mainly with plasma therapy and/or eculizumab. Where reported, eculizumab substantially improved aHUS-related outcomes in almost all adult and pediatric patients. EXPERT OPINION: Eculizumab has dramatically altered the natural course of aHUS, improving prognosis and patient outcomes. Addressing economic challenges and investing in healthcare infrastructure will be essential to implement strategies for timely detection and early treatment of aHUS in Latin America.

Phagocytosis.

One hundred years have passed since the death of Élie Metchnikoff (1845-1916). He was the first to observe the uptake of particles by cells and realized the importance of this process, named phagocytosis, for the host response to injury and infection. He also was a strong advocate of the role of phagocytosis in cellular immunity, and with this, he gave us the basis for our modern understanding of inflammation and the innate immune response. Phagocytosis is an elegant but complex process for the ingestion and elimination of pathogens, but it is also important for the elimination of apoptotic cells and hence fundamental for tissue homeostasis. Phagocytosis can be divided into four main steps: (i) recognition of the target particle, (ii) signaling to activate the internalization machinery, (iii) phagosome formation, and (iv) phagolysosome maturation. In this chapter, we present a general view of our current knowledge on phagocytosis performed mainly by professional phagocytes through antibody and complement receptors and discuss aspects that remain incompletely understood.

Mannose Binding Lectin and C3 Serum Levels in Coronary Artery Disease: A Cross-Sectional Study.

BACKGROUND: The process of tissue injury in coronary artery disease (CAD) has been associated with activation of the complement system, partly due to the action of mannose-binding lectin (MBL) and C3, which are expressed in atherosclerotic lesions. OBJECTIVE: The aim of this study was to evaluate the serum levels of MBL and C3 in patients with CAD and to compare them with healthy controls. Additionally, we aim to assess the correlation between MBL and C3 levels and cardiometabolic parameters. METHODS: MBL and C3 serum concentration were determined by ELISA and immunoturbidimetry, respectively, in up to 119 patients undergoing coronary angiography for CAD evaluation, comprising 48 individuals diagnosed with acute myocardial infarction (MI) and 71 without MI. A total of 93 paired healthy controls were included in the study. RESULTS: Individuals with CAD had MBL serum concentration higher than controls (p = .002), regardless of the presence of MI (p = .006). In addition, high concentration of MBL (>2000 ng/mL) was more frequent in patients with CAD (p = .007; OR = 2.6; 95% CI = 1.3-5.1). C3 levels were not significantly associated with any of the patient groups but were positively correlated with cardiometabolic parameters such as body mass index (BMI) and triglycerides levels. CONCLUSIONS: Higher concentrations of MBL were found to be associated with CAD, whereas C3 levels were found to be associated with cardiovascular risk factors.

Proteomic Insights into Biology of Bipolar Disorder: Implications for Health Complexity and Mortality.

OBJECTIVE: The present study has the following objectives: 1) identify differentially expressed proteins and pathways in blood samples of BD compared to healthy controls by employing high-throughput proteomics and bioinformatics and 2) characterize disease-related molecular signatures through in-depth analysis of the differentially expressed proteins and pathways. METHODS: Blood samples from BD patients (n=10) classified into high (BD+) or poor functioning (BD-), based on functional and cognitive status, and healthy controls (n=5) were analyzed using mass spectrometry-based proteomic analysis. Bioinformatics was performed to detect biological processes, pathways, and diseases related to BD. RESULTS: Eight proteins exclusively characterized the molecular profile of patients with BD+ compared to HC, while 26 altered proteins were observed in the BD- group. These altered proteins were mainly enriched in biological processes related to lipid metabolism, complement system and coagulation cascade, and cardiovascular diseases; all these changes were more prominent in the BD- group. CONCLUSION: These findings may represent systemic alterations that occur with the progression of the illness and a possible link between BD and medical comorbidities. Such comprehensive understanding provides valuable insights for targeted interventions, addressing mental and physical health aspects in subjects with BD. Despite these promising findings, further research is warranted, encompassing larger sample cohorts and incorporating biological validation through molecular biology methods.

Complement-Mediated Thrombotic Microangiopathy after Kidney Transplant: Should Treatment with C5 Inhibitor Be Lifelong?

Complement-mediated thrombotic microangiopathy (CM-TMA) is a rare and life-threatening complication that can occur in kidney transplant recipients, with various potential triggers including immunosuppressive medications. The optimal management and duration of treatment with C5 inhibitors (C5i) for CM-TMA in this patient population remain areas of ongoing investigation. We present the case of a 38-year-old female with a history of IgA nephropathy who underwent preemptive living-related kidney transplantation and subsequently developed CM-TMA 7 years post-transplant. Treatment with ravulizumab led to a rapid hematologic response and stabilized platelet counts. Serial measurements of complement functional tests and clinical stability guided the discontinuation of C5i therapy. The case highlights the complexity of managing CM-TMA in kidney transplant recipients, particularly in determining the appropriate duration of C5i therapy. The absence of an established protocol for discontinuation necessitates a personalized approach based on clinical and laboratory stability, absence of complement gene variants, and serial complement functional tests. Further prospective investigations are warranted to define the optimal strategies for monitoring and safely discontinuing C5i therapy in this unique patient population. This case underscores the importance of individualized care in the management of CM-TMA post-kidney transplantation, offering insights into potential criteria for therapy discontinuation.

Role of the complement system in kidney cell death induced by Loxosceles venom Sphingomyelinases D.

Envenomation by Loxosceles spiders can result in local and systemic pathologies. Systemic loxoscelism, which can lead to death, is characterized by intravascular hemolysis, platelet aggregation, and acute kidney injury. Sphingomyelinase D (SMase D) in Loxosceles spider venom is responsible for both local and systemic pathologies, and has been shown to induce metalloprotease activity. As the complement system is involved in many renal pathologies and is involved in hemolysis in systemic loxoscelism, the aim of this study was to investigate its role and the role of complement regulators and metalloproteases in an in vitro model of Loxosceles venom induced renal pathology. We investigated the effects of the venom/SMase D and the complement system on the HK-2 kidney cell line. Using cell viability assays, western blotting, and flow cytometry, we show that human serum, as a source of complement, enhanced the venom/SMase D induced cell death and the deposition of complement components and properdin. Inhibitors for ADAM-10 and ADAM-17 prevented the venom induced release of the of the complement regulator MCP/CD46 and reduced the venom/SMase D induced cell death. Our results show that the complement system can contribute to Loxosceles venom induced renal pathology. We therefore suggest that patients experiencing systemic loxoscelism may benefit from treatment with metalloproteinase inhibitors and complement inhibitors, but this proposition should be further analyzed in future pre-clinical and clinical assays.

Analysis of glomerular deposition of IgM and C3 in patients with podocytopathies.

Minimal Change Disease (MCD) and Focal Segmental Glomerulosclerosis (FSGS) are the main causes of nephrotic syndrome in the world. The complement system appears to play an important role in the pathogenesis of these diseases. To evaluate the deposition of immunoglobulins and particles of the complement system in renal biopsies of patients with FSGS and MCD and relate to laboratory data, we selected 59 renal biopsies from patients with podocytopathies, 31 from patients with FSGS and 28 with MCD. Epidemiological, clinical, laboratory information and the prognosis of these patients were evaluated. Analysis of the deposition of IgM, IgG, C3, C1q and C4d in renal biopsies was performed. We related IgM and C3 deposition with laboratory parameters. Statistical analysis was performed using GraphPad Prism version 7.0. Glomerular deposition of IgM was significantly higher in the FSGS group, as was codeposition of IgM and C3. The clinical course of patients and laboratory data were also worse in cases of FSGS, with a higher percentage progressing to chronic kidney disease and death. Patients with C3 deposition had significantly higher mean serum creatinine and significantly lower eGFR, regardless of disease. Patients with FSGS had more IgM and C3 deposition in renal biopsies, worse laboratory data and prognosis than patients with MCD. C3 deposition, both in FSGS and MCD, appears to be related to worsening renal function.

A peptide dataset for target analysis of human complement system proteins.

The targeted LC-MS/MS method has been widely applied for peptide quantification, offering sensibility, specificity, and reproducibility to the analysis. However, it requires the prior selection of targets, including the construction of a spectral library. Here, we present a dataset comprising peptide mass spectra for targeted LC-MS/MS method setup, applied to a set of human complement system proteins. Additionally, we selected a group of peptides and demonstrated their stability and reproducibility in quantification. This dataset is invaluable for studies aiming at the quantification of the complement system proteins by targeted LC-MS/MS, as it provides data for spectral library construction and a list of selected peptides.

Systematic review and bioinformatics analysis of plasma and serum extracellular vesicles proteome in type 2 diabetes.

Background: Type 2 diabetes (T2D) is a complex metabolic ailment marked by a global high prevalence and significant attention in primary healthcare settings due to its elevated morbidity and mortality rates. The pathophysiological mechanisms underlying the onset and progression of this disease remain subjects of ongoing investigation. Recent evidence underscores the pivotal role of the intricate intercellular communication network, wherein cell-derived vesicles, commonly referred to as extracellular vesicles (EVs), emerge as dynamic regulators of diabetes-related complications. Given that the protein cargo carried by EVs is contingent upon the metabolic conditions of the originating cells, particular proteins may serve as informative indicators for the risk of activating or inhibiting signaling pathways crucial to the progression of T2D complications. Methods: In this study, we conducted a systematic review to analyze the published evidence on the proteome of EVs from the plasma or serum of patients with T2D, both with and without complications (PROSPERO: CRD42023431464). Results: Nine eligible articles were systematically identified from the databases, and the proteins featured in these articles underwent Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. We identified changes in the level of 426 proteins, with CST6, CD55, HBA1, S100A8, and S100A9 reported to have high levels, while FGL1 exhibited low levels. Conclusion: These proteins are implicated in pathophysiological mechanisms such as inflammation, complement, and platelet activation, suggesting their potential as risk markers for T2D development and progression. Further studies are required to explore this topic in greater detail.

Plasmid-encoded toxin of Escherichia coli cleaves complement system proteins and inhibits complement-mediated lysis in vitro.

Plasmid-encoded toxin (Pet) is an autotransporter protein of the serine protease autotransporters of Enterobacteriaceae (SPATE) family, important in the pathogenicity of Escherichia coli. The pet gene was initially found in the enteroaggregative E. coli (EAEC) virulence plasmid, pAA2. Although this virulence factor was initially described in EAEC, an intestinal E. coli pathotype, pet may also be present in other pathotypes, including extraintestinal pathogenic strains (ExPEC). The complement system is an important defense mechanism of the immune system that can be activated by invading pathogens. Proteases produced by pathogenic bacteria, such as SPATEs, have proteolytic activity and can cleave components of the complement system, promoting bacterial resistance to human serum. Considering these factors, the proteolytic activity of Pet and its role in evading the complement system were investigated. Proteolytic assays were performed by incubating purified components of the complement system with Pet and Pet S260I (a catalytic site mutant) proteins. Pet, but not Pet S260I, could cleave C3, C5 and C9 components, and also inhibited the natural formation of C9 polymers. Furthermore, a dose-dependent inhibition of ZnCl2-induced C9 polymerization in vitro was observed. E. coli DH5α survived incubation with human serum pre-treated with Pet. Therefore, Pet can potentially interfere with the alternative and the terminal pathways of the complement system. In addition, by cleaving C9, Pet may inhibit membrane attack complex (MAC) formation on the bacterial outer membrane. Thus, our data are suggestive of a role of Pet in resistance of E. coli to human serum.

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.

High production MBL2 polymorphisms protect against COVID-19 complications in critically ill patients: A retrospective cohort study.

Mannose-binding lectin (MBL) binds to SARS-CoV-2, inhibits infection of susceptible cells, and activates the complement system via the lectin pathway. In this study, we investigated the association of MBL2 polymorphisms with the risk of hospitalization and clinical worsening in patients with COVID-19. A total of 550 patients with COVID-19 were included (94 non-hospitalized and 456 hospitalized). Polymorphisms in MBL2 exon 1 (codons 52, 54 and 57) and promoter region (-550, -221, and +4) were determined by real-time PCR. MBL and complement proteins were measured by Luminex. A higher frequency of the H/H genotype and the HYPA haplotype was observed in non-hospitalized patients when compared to hospitalized. In addition, critically ill patients carrying haplotypes associated with high MBL levels (HYPA/HYPA + HYPA/LYPA + HYPA/LYQA + LYPA/LYQA + LYPA/LYPA + LYQA/LYQA + LXPA/HYPA + LXPA/LYQA + LXPA/LYPA) were protected against lower oxygen saturation levels (P = 0.02), use of invasive ventilation use (P = 0.02, OR 0.38), and shock (P = 0.01, OR 0.40), independent of other potential confounders adjusted by multivariate analysis. Our results suggest that variants in MBL2 associated with high MBL levels may play a protective role in the clinical course of COVID-19.

Therapeutic efficacy of a potent anti-Venezuelan equine encephalitis virus antibody is contingent on Fc effector function.

The development of specific, safe, and potent monoclonal antibodies (Abs) has led to novel therapeutic options for infectious disease. In addition to preventing viral infection through neutralization, Abs can clear infected cells and induce immunomodulatory functions through engagement of their crystallizable fragment (Fc) with complement proteins and Fc receptors on immune cells. Little is known about the role of Fc effector functions of neutralizing Abs in the context of encephalitic alphavirus infection. To determine the role of Fc effector function in therapeutic efficacy against Venezuelan equine encephalitis virus (VEEV), we compared the potently neutralizing anti-VEEV human IgG F5 (hF5) Ab with intact Fc function (hF5-WT) or containing the loss of function Fc mutations L234A and L235A (hF5-LALA) in the context of VEEV infection. We observed significantly reduced binding to complement and Fc receptors, as well as differential in vitro kinetics of Fc-mediated cytotoxicity for hF5-LALA compared to hF5-WT. The in vivo efficacy of hF5-LALA was comparable to hF5-WT at -24 and + 24 h post infection, with both Abs providing high levels of protection. However, when hF5-WT and hF5-LALA were administered + 48 h post infection, there was a significant decrease in the therapeutic efficacy of hF5-LALA. Together these results demonstrate that optimal therapeutic Ab treatment of VEEV, and possibly other encephalitic alphaviruses, requires neutralization paired with engagement of immune effectors via the Fc region.

The complement system as a key modulator of the oral microbiome in health and disease.

In this review, we address the interplay between the complement system and host microbiomes in health and disease, focussing on oral bacteria known to contribute to homeostasis or to promote dysbiosis associated with dental caries and periodontal diseases. Host proteins modulating complement activities in the oral environment and expression profiles of complement proteins in oral tissues were described. In addition, we highlight a sub-set of bacterial proteins involved in complement evasion and/or dysregulation previously characterized in pathogenic species (or strains), but further conserved among prototypical commensal species of the oral microbiome. Potential roles of these proteins in host-microbiome homeostasis and in the emergence of commensal strain lineages with increased virulence were also addressed. Finally, we provide examples of how commensal bacteria might exploit the complement system in competitive or cooperative interactions within the complex microbial communities of oral biofilms. These issues highlight the need for studies investigating the effects of the complement system on bacterial behaviour and competitiveness during their complex interactions within oral and extra-oral host sites.

Role of the complement system in kidney cell death induced by Loxosceles venom Sphingomyelinases D

Envenomation by Loxosceles spiders can result in local and systemic pathologies. Systemic loxoscelism, which can lead to death, is characterized by intravascular hemolysis, platelet aggregation, and acute kidney injury. Sphingomyelinase D (SMase D) in Loxosceles spider venom is responsible for both local and systemic pathologies, and has been shown to induce metalloprotease activity. As the complement system is involved in many renal pathologies and is involved in hemolysis in systemic loxoscelism, the aim of this study was to investigate its role and the role of complement regulators and metalloproteases in an in vitro model of Loxosceles venom induced renal pathology. We investigated the effects of the venom/SMase D and the complement system on the HK-2 kidney cell line. Using cell viability assays, western blotting, and flow cytometry, we show that human serum, as a source of complement, enhanced the venom/SMase D induced cell death and the deposition of complement components and properdin. Inhibitors for ADAM-10 and ADAM-17 prevented the venom induced release of the of the complement regulator MCP/CD46 and reduced the venom/SMase D induced cell death. Our results show that the complement system can contribute to Loxosceles venom induced renal pathology. We therefore suggest that patients experiencing systemic loxoscelism may benefit from treatment with metalloproteinase inhibitors and complement inhibitors, but this proposition should be further analyzed in future pre-clinical and clinical assays.

Amyloid Fibrils Produced by Streptococcus sanguinis Contribute to Biofilm Formation and Immune Evasion.

Bacterial surface proteins assembled into amyloids contribute to biofilm formation and host immune evasion. Streptococcus sanguinis, a pioneer colonizer of teeth commonly involved in cardiovascular infections, expresses about thirty-three proteins anchored to the cell wall by sortase A. Here, we characterized the production of amyloid in S. sanguinis strains differing in biofilm and immune evasion phenotypes and investigated the role of sortase A in amyloidogenesis. Amyloid was identified in biofilms formed by nine strains, using Congo red (CR) staining and cross-polarized light microscopy. Additionally, EGCG, an amyloid inhibitor, impaired biofilm maturation in a strain-specific fashion. The amounts of amyloid-like components quantified in culture fluids of nine strains using thioflavin T and fluorimetry negatively correlated with bacterial binding to complement-activating proteins (SAP, C1q), C3b deposition and rates of opsonophagocytosis in PMNs, implying amyloid production in immune evasion. The deletion of the sortase A gene (srtA) in strain SK36 compromised amyloid production and sucrose-independent biofilm maturation. The srtA mutant further showed increased susceptibility to C3b deposition and altered interactions with PMNs as well as reduced persistence in human blood. These findings highlight the contribution of amyloids to biofilm formation and host immune evasion in S. sanguinis strains, further indicating the participation of sortase A substrates in amyloidogenesis.