Sensitive and specific assays for C3 nephritic factors clarify mechanisms underlying complement dysregulation

C3 nephritic factors are autoantibodies that prolong the half-life or prevent regulation of the alternative pathway C3 convertase, resulting in uncontrolled complement activation. They are strongly associated with renal disease but their role in pathogenesis remains controversial. Here we optimized and compared a panel of assays to identify and interrogate nephritic factor activities. Of 101 patients with histologic or clinically evident disease, 48 were positive in some or all assays. In the presence of properdin, binding of autoantibody was detected in 39 samples and convertase stabilization was detected in 36. Forty-two of 48 nephritic factors tested prevented convertase decay by factor H, and most of these by decay accelerating factor (28) and complement receptor 1 (34). Representative properdin-independent nephritic factors had no effect on C5 cleavage and terminal pathway activity, while properdin-dependent nephritic factors enhanced activity. Biacore analysis of four purified IgG samples confirmed resistance to decay and showed that properdin-independent nephritic factors increased convertase half-life over 50-fold, whereas properdin-dependent nephritic factors increased the half-life 10- to 20-fold and also increased activity of the C3 convertase up to 10-fold. Thus, our study provides a rational approach to detect and characterize nephritic factors in patients

Brown Spider (Loxosceles genus) Venom Toxins: Tools for Biological Purposes

Venomous animals use their venoms as tools for defense or predation. These venoms are complex mixtures, mainly enriched of proteic toxins or peptides with several, and different, biological activities. In general, spider venom is rich in biologically active molecules that are useful in experimental protocols for pharmacology, biochemistry, cell biology and immunology, as well as putative tools for biotechnology and industries. Spider venoms have recently garnered much attention from several research groups worldwide. Brown spider (Loxosceles genus) venom is enriched in low molecular mass proteins (5–40 kDa). Although their venom is produced in minute volumes (a few microliters), and contain only tens of micrograms of protein, the use of techniques based on molecular biology and proteomic analysis has afforded rational projects in the area and permitted the discovery and identification of a great number of novel toxins. The brown spider phospholipase-D family is undoubtedly the most investigated and characterized, although other important toxins, such as low molecular mass insecticidal peptides, metalloproteases and hyaluronidases have also been identified and featured in literature. The molecular pathways of the action of these toxins have been reported and brought new insights in the field of biotechnology. Herein, we shall see how recent reports describing discoveries in the area of brown spider venom have expanded biotechnological uses of molecules identified in these venoms, with special emphasis on the construction of a cDNA library for venom glands, transcriptome analysis, proteomic projects, recombinant expression of different proteic toxins, and finally structural descriptions based on crystallography of toxins

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

A humanized antibody that regulates the alternative pathway convertase: potential for therapy of renal disease associated with nephritic factors

Dysregulation of the complement alternative pathway can cause disease in various organs that may be life-threatening. Severe alternative pathway dysregulation can be triggered by autoantibodies to the C3 convertase, termed nephritic factors, which cause pathological stabilization of the convertase enzyme and confer resistance to innate control mechanisms; unregulated complement consumption followed by deposition of C3 fragments in tissues ensues. The mAb, 3E7, and its humanized derivative, H17, have been shown previously to specifically bind activated C3 and prevent binding of both the activating protein, factor B, and the inhibitor, factor H, which are opposite effects that complicate its potential for therapy. Using ligand binding assays, functional assays, and electron microscopy, we show that these Abs bind C3b via a site that overlaps the binding site on C3 for the Ba domain within factor B, thereby blocking an interaction essential for convertase formation. Both Abs also bind the preformed convertase, C3bBb, and provide powerful inhibition of complement activation by preventing cleavage of C3. Critically, the Abs also bound and inhibited C3 cleavage by the nephritic factor–stabilized convertase. We suggest that by preventing enzyme formation and/or cleavage of C3 to its active downstream fragments, H17 may be an effective therapy for conditions caused by severe dysregulation of the C3 convertase and, in particular, those that involve nephritic factors, such as dense deposit disease

Aplicação da avaliação subjetiva global produzida pelo paciente (ASG-PPP) e análise do consumo alimentar de pacientes oncológicos: antes e durante o tratamento

The objective of this article is to apply the subjective global assessment produced by the patient (SGA-PPP) and to analyze the food consumption of cancer patients before and during chemotherapy treatment in a High Complexity Oncology Unit in the São Francisco Valley. This is a cross-sectional descriptive study, conducted from March 2022 to February 2023. Patients who had recently been diagnosed with some type of cancer and who had not yet started treatment were included. The research was divided into two moments: evaluation before the beginning of treatment and after 3 to 4 months of the initial approach. Clinical, socioeconomic and demographic questionnaires, as well as the ELSA-Brazil Food Frequency Questionnaire (FFQ) were applied to assess food consumption, as well as the SGA-PPP. Initially, 30 patients with a mean age of 60.20 ± 14.50 years were evaluated, and 40.00% (n=12) were reassessed. The most prevalent tumors were those of the gastrointestinal tract. In the initial evaluation, many patients already had a critical need for nutritional intervention. A comparison between the two research moments, with the patients reassessed, showed a worsening of the SGA-PPP score. As for food intake, the intake of fruits, vegetables and protein sources was more frequent in the reassessment, although many still do not consume daily. Thus, it is noteworthy that the increase in the percentages obtained in the FFQ reflected the frequency and not the amount consumed, since many patients reported a reduction in food intake in the SGA-PPP.&nbsp; It is concluded that chemotherapy can impact food intake and worsen nutritional status, thus demonstrating the importance of nutritional monitoring of these patients.Este estudo teve por objetivo analisar o perfil nutricional de pacientes oncológicos com a aplicação da ASG-PPP e avaliar o consumo alimentar antes e durante o tratamento, em uma Unidade de Alta Complexidade em Oncologia (UNACON), no Vale do São Francisco. Trata-se de um estudo descritivo transversal, realizado no período de março de 2022 a fevereiro de 2023. Foram incluídos pacientes recém diagnosticados com algum tipo de câncer, que ainda não tivessem iniciado o tratamento. A pesquisa foi dividida em dois momentos: avaliação antes do início do tratamento e após 3 a 4 meses da abordagem inicial. Foram aplicados questionários clínico, socioeconômico e demográfico, e o de Frequência Alimentar (QFA - ELSA-BRASIL) para avaliação do consumo alimentar, bem como a ASG-PPP. Foram avaliados inicialmente 30 pacientes, com idade média de 60,20± 14,50 anos, e 40,00% (n=12) foram reavaliados. Os tumores mais prevalentes foram os do trato gastrointestinal. Na avaliação inicial, muitos pacientes já apresentavam necessidade crítica de intervenção nutricional. Fazendo uma comparativa entre os dois momentos de pesquisa, com os pacientes reavaliados, notou-se piora do escore da ASG-PPP. Quanto ao consumo alimentar, a ingestão de frutas, legumes, verduras e fontes proteicas foi mais frequente na reavaliação, apesar de muitos ainda não consumirem diariamente. Sendo assim, ressalta-se que o aumento dos percentuais obtidos no QFA, refletiu a frequência e não quantidade consumida, visto que muitos pacientes relataram redução da ingestão alimentar na ASG-PPP. Conclui-se que a quimioterapia pode impactar na ingestão alimentar e piora do estado nutricional, demonstrando assim a importância do acompanhamento nutricional desses pacientes

Factor I is required for the development of membranoproliferative glomerulonephritis in factor H–deficient mice

The inflammatory kidney disease membranoproliferative glomerulonephritis type II (MPGN2) is associated with dysregulation of the alternative pathway of complement activation. MPGN2 is characterized by the presence of complement C3 along the glomerular basement membrane (GBM). Spontaneous activation of C3 through the alternative pathway is regulated by 2 plasma proteins, factor H and factor I. Deficiency of either of these regulators results in uncontrolled C3 activation, although the breakdown of activated C3 is dependent on factor I. Deficiency of factor H, but not factor I, is associated with MPGN2 in humans, pigs, and mice. To explain this discordance, mice with single or combined deficiencies of these factors were studied. MPGN2 did not develop in mice with combined factor H and I deficiency or in mice deficient in factor I alone. However, administration of a source of factor I to mice with combined factor H and factor I deficiency triggered both activated C3 fragments in plasma and GBM C3 deposition. Mouse renal transplant studies demonstrated that C3 deposited along the GBM was derived from plasma. Together, these findings provide what we believe to be the first evidence that factor I–mediated generation of activated C3 fragments in the circulation is a critical determinant for the development of MPGN2 associated with factor H deficiency

Deficiency of the human complement regulatory protein factor H associated with low levels of component C9

We identified a 4-year-old Brazilian boy from a family of Japanese descent and history of consanguinity, who suffered from severe recurrent pneumonia. He carries factor H (FH) deficiency associated with reduced levels of component C9 and low serum levels of C3 and factor B. His mother also presented low levels of these proteins and factor I, while his father and sister had only lower levels of FH. Western blot assays confirmed the complete absence of FH and FHL-1 polypeptides in this patient. Sequencing of the proband`s FH cDNA revealed a homozygous G453A substitution, encoding an Arg(127)His change. His mother, father and sister are heterozygous for this substitution. Despite the absence of FH in the plasma, this protein was detected in the patient`s fibroblasts, suggesting that Arg(127) may be important for FH secretion. Low concentrations of C9 were detected in the proband serum but no mutations in the patient`s C9 gene or promoter have been identified, suggesting that this is a consequence of uncontrolled complement activation and high C9 consumption.FAPESP Fundacao de Amparo a Pesquisa do Estado de Sao PauloFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq Conselho Nacional de Pesquisa e Desenvolvimento Tecnologico, Brazi

An extended mini-complement factor H molecule ameliorates experimental C3 glomerulopathy.

Abnormal regulation of the complement alternative pathway is associated with C3 glomerulopathy. Complement factor H is the main plasma regulator of the alternative pathway and consists of 20 short consensus repeat (SCR) domains. Although recombinant full-length factor H represents a logical treatment for C3 glomerulopathy, its production has proved challenging. We and others have designed recombinant mini-factor H proteins in which ‘non-essential’ SCR domains have been removed. Here, we report the in vitro and in vivo effects of a mini-complement factor H protein, FH1–5^18–20, using the unique factor H–deficient (Cfh-/-) mouse model of C3 glomerulopathy. FH1–5^18–20 is comprised of the key complement regulatory domains (SCRs 1–5) linked to the surface recognition domains (SCRs 18–20). Intraperitoneal injection of FH1–5^18–20 in Cfh-/- mice reduced abnormal glomerular C3 deposition, similar to full-length factor H. Systemic effects on plasma alternative pathway control were comparatively modest, in association with a short half-life. Thus, FH1–5^18–20 is a potential therapeutic agent for C3 glomerulopathy and other renal conditions with alternative pathway-mediated tissue injury