Production and characterisation of a SARSCoV-2 S-protein RBD homodimer with increased avidity for specific antibodies.

Monitoring of the proportion of immune individuals and the effectiveness of vaccination in a population involves evaluation of several important parameters, including the level of virus-neutralising antibodies. In order to combat the COVID-19 pandemic, it is essential to develop approaches to detecting SARS-CoV-2 neutralising antibodies by safe, simple and rapid methods that do not require live viruses. To develop a test system for enzyme-linked immunosorbent assay (ELISA) that detects potential neutralising antibodies, it is necessary to obtain a highly purified recombinant receptor-binding domain (RBD) of the spike (S) protein with high avidity for specific antibodies. The aim of the study was to obtain and characterise a SARSCoV-2 S-protein RBD homodimer and a recombinant RBD-expressing cell line, as well as to create an ELISA system for detecting potential neutralising antibodies. Material(s) and Method(s): the genetic construct was designed in silico. To generate a stable producer cell line, the authors transfected CHO-S cells, subjected them to antibiotic pressure, and selected the optimal clone. To isolate monomeric and homodimeric RBD forms, the authors purified the recombinant RBD by chromatographic methods. Further, they analysed the activity of the RBD forms by Western blotting, bio-layer interferometry, and indirect ELISA. The analysis involved monoclonal antibodies GamXRH19, GamP2C5, and h6g3, as well as serum samples from volunteers vaccinated with Gam-COVID-Vac (Sputnik V) and unvaccinated ones. Result(s): the authors produced the CHO-S cell line for stable expression of the recombinant SARS-CoV-2 S-protein RBD. The study demonstrated the recombinant RBD's ability to homodimerise after fed-batch cultivation of the cell line for more than 7 days due to the presence of unpaired cysteines. The purified recombinant RBD yield from culture broth was 30-50 mg/L. Monomeric and homodimeric RBD forms were separated using gel-filtration chromatography and characterised by their ability to interact with specific monoclonal antibodies, as well as with serum samples from vaccinated volunteers. The homodimeric recombinant RBD showed increased avidity for both monoclonal and immune sera antibodies. Conclusion(s): the homodimeric recombinant RBD may be more preferable for the analysis of levels of antibodies to the receptor-binding domain of the SARS-CoV-2 S protein.Copyright © 2023 Authors. All rights reserved.

SARS-CoV-2 Infection Increases the Gene Expression Profile for Alzheimer's Disease Risk

The COVID-19 pandemic is a global outbreak of coronavirus, an infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). One in five adults who have had COVID-19 in the past was still experiencing any one of the symptoms of long COVID like headache, brain fog, fatigue, and shortness of breath. Up to 30% of individuals with mild to severe infection show diverse neurological symptoms, including dementias. Hence, it is very much important to characterize the neurotropism and neurovirulence of the SARS-CoV-2 virus. This helps us understand the mechanisms involved in initiating inflammation in the brain, further leading to the development of earlyonset Alzheimer's disease and related dementias (ADRDs). In our brain gene expression analysis, we found that severe COVID-19 patients showed increased expression of innate immune response genes and genes that are implicated in AD pathogenesis. To study the infection-induced ADRDs, we used a mouse-adapted strain of the SARS-CoV-2 (MA10) virus to infect mice of different age groups (3, 6, and 20 Months). In this study, we found that aged mice showed evidence of viral neurotropism, prolonged viral infection, increased expression of tau aggregator FKBP51, interferoninducible gene Ifi204, and complement genes like C4 and C5AR1. Brain histopathology also showed the AD signature including tau-phosphorylation, tau-oligomerization, and alpha-synuclein expression in aged MA10-infected mice. The results from gene expression profiling of SARS-CoV-2 infected and AD brains and studies with MA10 aged mice show that COVID-19 infection increases the risk of AD in the aged population. Furthermore, this study helps us to understand the crucial molecular markers that are regulated during COVID infection that could act as major players in developing ADRDs. Future studies will be involved in understanding the molecular mechanisms of ADRD in response to COVID infection and developing novel therapies targeting AD.

Regional effects on efficacy and safety of vilobelimab in mechanically ventilated patients with severe COVID-19

Introduction: Poor outcomes in COVID-19 patients (pt) are associated with C5a-C5aR axis activation. A C5a-specific monoclonal antibody, vilobelimab (VILO), improves outcomes in critically ill COVID-19 pt in a Phase 3 randomized, double-blind, placebo (PLC)- controlled study [1]. Method(s): COVID-19 pt within 48 h of intubation were randomly assigned to receive 6, 800 mg infusions of VILO or PLC at a 1:1 ratio on top of standard of care. Predefined subgroup analyses by region and country were performed. Result(s): Forty-six (46) hospitals on 4 continents randomized 369 pt: VILO (n = 178), PLC (n = 191). VILO significantly reduced 28- (HR 0.67;95% CI 0.48-0.96;p = 0.027) and 60-Day mortality (HR 0.67;95% CI 0.48-0.93, p = 0.0163) using a predefined, unstratified per protocol analysis. Mortality rates at 28- and 60-days and VILO treatment effects, however, differed substantially between regions: Western Europe HR for 60-day mortality 0.59 [0.37-0.95], South Africa plus Russian Federation HR 0.62 [0.28-1.38] and South America HR 0.80 [0.46-1.39] (Fig. 1). The weak signal in South America is predominately driven by Brazil (n = 74), which showed a significant age imbalance with a median 9-years younger PLC group (44.5-years-old vs 53.5-years-old) with low 60-day mortality of ~ 32.5% in the PLC group versus ~ 43.3% in Western Europe. Adjusting for age group categories (<= 30, 31-40, 41-50, 51-60, > 60;Cox regression) for 60-day mortality changed the HR in Brazil (0.96 [0.44-2.10] for continuous age-adjustment) to values near the estimate for the entire study population (HR 0.77 [0.35-1.69] for age in categories), suggesting a by chance imbalance and not a statistically evident weaker effect in Brazil. Conclusion(s): Regional efficacy differences between the rest of the world and South America were driven by age imbalances between treatment groups, which do not diminish the robust efficacy signal for VILO in severe COVID-19.

Pharmacokinetic/pharmacodynamic analysis of vilobelimab and anaphylatoxin c5a as well as antidrug antibodies in Panamo: a phase 3 study in critically ill, mechanically ventilated COVID-19 patients

Introduction: C5a-C5aR axis activation is associated with increased mortality in severe COVID-19. Vilobelimab (VILO), a C5a-specific monoclonal antibody, improved mortality in severe COVID-19 patients (pts) in a Phase 3 multicenter, randomized, double-blind, placebo (PLC)- controlled study [1]. A pharmacokinetic/pharmacodynamic (PK/PD) analysis was undertaken to assess VILO and C5a as well as antidrug antibodies (ADA) levels in the study. Method(s): Forty-six (46) hospitals on four continents randomized 369 COVID-19 pts (VILO [n = 178], PLC [n = 191]) within 48 h of being mechanically ventilated to receive 6, 800 mg infusions of VILO or PLC at a 1:1 ratio on top of standard of care. Blood samples were taken at screening, Day 8 and at hospital discharge for VILO and C5a and at screening and hospital discharge for ADA. Enzyme-linked immunosorbent assays were used to analyze levels. Result(s): Screening blood samples for VILO and C5a were available for VILO (n = 93) and PLC (n = 99) from sites in Western Europe. On Day 8 after 3 infusions, mean VILO trough concentrations were 21799.3- 302972.1 ng/mL (geometric mean 137881.3 ng/mL) (Fig. 1). At screening, C5a was highly elevated and comparable between groups: VILO median 118.3 ng/mL, mean 130.3 ng/mL, PLC median 104.6 ng/mL, mean 123.2 ng/mL. By Day 8, C5a levels were reduced by 84.6% in the VILO group (median 14.5 ng/mL [mean 16.8 ng/mL], p < 0.001) versus a 19.6% increase in the PLC group (median, 119.2 ng/mL, mean 129.8 ng/ mL). Beyond Day 8, though PD sampling was sparse, C5a levels remained elevated for PLC whereas C5a slowly rose but did not reach screening levels for VILO. Treatment-induced ADA were observed in 1 pt in the VILO group (Day 40 discharge) and 1 pt in the PLC group (Day 25 discharge), both appeared independent of treatment. Conclusion(s): The PK/PD analysis shows that VILO efficiently inhibits C5a in pts with severe COVID-19 resulting in a robust clinical effect on mortality reduction without inducing ADA.

Symptoms and Biomarkers of Long Covid in People Living with and without Hiv

Background: HIV is a risk factor for severe acute COVID-19, but it is unknown whether HIV is a risk factor for long COVID. Method(s): We conducted a prospective observational cohort study of US adults with HIV (PWH) and HIV-seronegative adults with first SARS-CoV-2 infection within 4 weeks together with people who never had COVID-19. At enrollment, participants recalled the presence and severity of 49 long COVID-associated symptoms in the month prior to COVID-19. The same symptom survey was administered at 1, 2, 4, and 6 months post-COVID or post-enrollment for never- COVID participants. Post-COVID participants donated blood 1 and 4 months post-COVID, and never-COVID participants donated blood 0-1 times. Antibody titers to 18 coronavirus antigens and levels of 30 cytokines and hormones were quantified (Meso Scale Discovery). The Mann Whitney U test was used to compare continuous variables between groups, and Pearson's chi-squared test for categorical variables. Spearman correlation analyses were used to build networks of associations between cytokines and symptoms. Result(s): 341 participants enrolled between June 2021 and September 2022. Of these, 73 were PWH post-COVID, 121 were HIV-seronegative post-COVID, 78 were PWH never-COVID, and 69 were HIV-seronegative never-COVID. Over 85% of participants were vaccinated prior to COVID-19. Most participants with HIV were male sex at birth (83% post-COVID, 59% never-COVID), on ART ( >95%), with median CD4 counts >500. Over 60% of participants reported 1+ new or worsened symptoms 2-6 months post-COVID, with higher percentages in PWH at 2 months post-COVID (p< 0.05). PWH were more likely to report body ache, pain, confusion, memory problems, and thirst and had higher levels of creatine phosphokinase post-COVID than HIV-seronegative people. SARS-CoV-2 and non-SARS human coronavirus antibody titers did not differ between PWH and HIV-seronegative post-COVID participants. Cytokine associations with each other (network density) were significantly enriched at 1 month post-COVID in both PWH and HIV-seronegative people, with significantly less enrichment at 4 months post-COVID and in never- COVID participants. Levels of four analytes (cortisol, C5a, TGF-beta1, and TIM-3) associated with specific symptoms of long COVID. Conclusion(s): PWH may experience more symptoms post-COVID with a slightly different symptom profile than people without HIV. Inflammatory networks were active in PWH and people without HIV at 1 month post-COVID.

Terminal complement complex C5b-9 and C5b assay in sera of COVID-19 patients with different disease severities

Objective: The aim of this study is to find out the link between the involvement of complement activation in the inflammatory reactions in COVID-19 patients, the deterioration of the clinical status and development of sever COVID-19 in those patients. Methods: The study included 274 COVID-19 patients, divided into three groups;group1: severe COVID-19 patients (n=37), group 2;moderate COVID-19 severity patients (n=78), group 3;mild COVID-19 severity patients (n=159). Serum levels of C-reactive protein, D-dimer, and ferritin were measured in the three patient groups, and the patients were subjected to CT chest imaging. Serum levels of the tested biomarkers were measured by ELISA at diagnosis. Results: Sever COVID-19 patients had higher serum levels of ferritin and D-dimer in comparison to patients with moderate and mild severity COVID-19 with statistically significant difference (p value 0.01 and 0.02 respectively). There was a significant elevation in the serum levels IL-6 and TNF-α in severe COVID-19 patients (488.5±112.2 and 159.6±38.3 respectively) versus moderate (206.07±53.3 and 93.5±39.5) and mild group (200.9± 52.27 and 52.9±23) respectively, (p value < 0.001). There was also a significant elevation of C5b and C5b-9 serum levels in severe COVID-19 patients (18.6±10.3 and 73.25±7.35) compared to moderate (14.11±15.6 and 143.6±170) and mild COVID-19 groups (76± 11.32 and 3.9± 3.03) respectively. Conclusion: We conclude that the severity of inflammation presented in elevated neutrophil counts and serum levels of inflammatory cytokines IL-6 and TNF in association with sever complement activation are implicated in severity and bad prognosis of COVID-19. © 2020 The author (s).

Kidney Limited Complement-Mediated Thrombotic Microangiopathy- a Challenging Case

Introduction: Complement-mediated thrombotic microangiopathy (CM-TMA) is a rare disease characterized by microangiopathic hemolytic anemia (MAHA), thrombocytopenia and organ injury. The absence of hemolysis and thrombocytopenia is rare. We present a case of kidney limited CM-TMA successfully treated with eculizumab. Method(s): A 36 year-old man with poorly controlled hypertension, obesity, CKD (baseline creatinine (sCr) 2,6mg/dL, albuminuria 150mg/g), hyperlipidemia, obstructive sleep apnea, hyperuricemia, SARS-CoV-2 infection 3 months earlier, and family history of CKD of unknown etiology (father started kidney replacement therapy (KRT) at young age) presented to the ER with high blood pressure and right hemiplegy. Head CT scan showed left thalamo-capsular hemorrhage. Oftalmologic exam was normal. Laboratory findings were: hemoglobin (Hb) 12.5g/dL, elevated white cell count (17.900/uL), platelet count 214.000/uL, sCr 4.3mg/dL, lactate dehydrogenase (LDH) 303U/L. Urine dipstick revealed protein+ and Hb++. Chest X-ray showed signs of pneumonia. The patient was admitted in ICU and mechanically ventilated. After 3 weeks, renal function recovered to its baseline (sCr 1.5mg/dL, no proteinuria) without KRT, and the patient was transferred to the medical ward. Several infectious complications prolonged hospital stay. After 3 months, a new mild SARS-CoV-2 infection was detected. At this time: Hb 9.9g/dL, platelets 220.000/uL, sCr 2.2mg/dL. Six days later the patient showed Hb 9.5 g/dL, without reticulocytosis, platelets 195.000/uL, sCr 6.3mg/dL, LDH 348U/L, normal haptoglobin, no schizocytes on blood smear. After 3 days, the patient was anuric and sCr increased to 10mg/dL, prompting KRT. Kidney ultrasound showed no abnormalities. Autoimmunity study was negative, normal C3/C4, no monoclonal gammopathy, and negative viral serologies. Kidney biopsy (KB) was performed as the etiology of AKI remained unclear. Light microscopy revealed thickned glomerular capillary walls with subendothelial expansion forming double contouring, arteriolar intimal expansion and fibrin thrombi occluding the vascular lumina. Scarse C3 deposition was observed in capillary walls. Since the morphological features were consistent with TMA, secondary causes were excluded and primary causes also investigated: ADAMTS13 activity, complement factor B and I were within normal range, slight decrease of factor H with normal anti factor H antibody. The molecular studies of complement genes were performed by NGS-based gene panel revealing a rare heterozygous missense mutation on gene CFB, c.1189G>A (p.Asp397Asn), described as a genetic risk factor of CM-TMA in the presence of a trigger. Result(s): Treatment with eculizumab was started and the patient showed signs of kidney recovery allowing KRT suspension 1 month later (sCr 5.53mg/dL). Of note, the patient never presented MAHA or thrombocytopenia. After 5 months, renal function improved to sCr 3.9mg/dL. Conclusion(s): We report a case of CM-TMA with isolated kidney injury without laboratory hallmarks of TMA. Patients usually require a secondary trigger for the disease to manifest, and in this case SARS-CoV-2 infection may have been the causative agent. A mutation in gene CFB may have predisposed the patient to the outcome. KB was crucial for diagnosis and prompted the treatment with eculizumab with partial recovery without the need for chronic KRT. No conflict of interestCopyright © 2023

Phase 3 RCT of C5a-Specific Vilobelimab in Severe COVID-19 Pneumonia

Background: Blocking the C5a-C5aR axis in COVID-19 patients could improve outcomes by limiting myeloid cell infiltration in damaged organs and preventing excessive lung inflammation and endothelialitis. Aims and Objectives: Vilobelimab (VILO), an anti-C5a mAb that preserves the membrane attack complex (MAC), was tested in a Phase III adaptively designed multicenter, double-blind placebo (P)-controlled study for survival in critically ill COVID-19 patients. Method(s): COVID-19 pneumonia patients (N=369;VILO n=178, P n=191) within 48 hrs of intubation were randomly assigned to receive 6, 800 mg infusions of VILO or P on top of standard of care. Primary outcome was 28-day allcause mortality. Result(s): 28-day all-cause mortality was 31.7% VILO vs 41.6% P (Kaplan-Meier estimates;Cox regression site stratified, HR 0.73;95%CI:0.50-1.06;P=0.094) with a 22.7% relative mortality reduction to Day 60. In predefined primary outcome analysis without site stratification, VILO significantly reduced 28-day mortality (HR 0.67;95%CI:0.48-0.96;P=0.027);needed to treat number, 10 to save 1. VILO significantly reduced 28-day mortality in severe patients with baseline WHO ordinal scale score of 7 (n=237, HR 0.62;95%CI:0.40-0.95;P=0.028) or severe ARDS/PaO2/FiO2<=100 mmHg (n=98, HR 0.55;95%CI:0.30-0.98;P=0.044) or eGFR<60 mL/min/1.73m2 (n=108, HR 0.55;95%CI:0.31-0.96;P=0.036). Treatment emergent AEs were 90.9% VILO vs 91.0% P. Infections were comparable;VILO (62.9%), P (59.3%). Serious AEs were 58.9% VILO, 63.5% P. Conclusion(s): VILO reduced mortality at 28 to 60 days in severe COVID-19 pneumonia patients with no increase in infections suggesting the importance of targeting C5a while preserving MAC.

The efficacy and safety of complement C5a inhibitors for patients with severe COVID-19: a systematic review and meta-analysis.

BACKGROUND: The clinical efficacy and safety of complement C5a inhibitors for patients with severe COVID-19 remains unclear. METHODS: The PubMed, Embase, Cochrane Library, and ClinicalTrials.gov databases were searched from their inception to 27 September 2022. Only studies that assessed the usefulness of C5a inhibitors for the treatment of patients with severe COVID-19 patients were included. The primary outcome was the risk of 28-day mortality. RESULTS: Six studies, including four randomized controlled trials (RCTs) and two non-RCTs, were included. The study group receiving C5a inhibitors had a significantly lower risk of mortality compared with the control group (23.6% [70/297] vs 39.2% [136/347]; odds ratio [OR], 0.53; 95% confidence interval [CI]: 0.37-0.76; P< 0.001), and no heterogeneity was detected (I2 = 0%; P= 0.58). Compared with control group, the study group was associated with a similar risk of serious adverse events (AEs) (OR, 0.84; 95% CI: 0.57-1.23; P0 = 0.37), infection (OR, 1.46; 95% CI: 0.77-2.79; P= 0.25) and acute kidney injury (OR, 0.89; 95% CI: 0.54-1.46; P= 0.64). CONCLUSION: C5a inhibitors could help reduce the risk of mortality in patients with severe COVID-19 infection while being as safe as placebos. These findings support the promising role of C5a inhibitors in the treatment of severe COVID-19.

Complete response to eculizumab in atypical hemolytic uremic syndrome with homozygous C3 mutation

Case Report: Atypical Hemolytic Uremic Syndrome (atypical HUS) is a rare and severe form of thrombotic microangiopathy (TMA) characterized by thrombocytopenia, intravascular hemolysis, and acute kidney injury with an incidence of 1 per million.1 Dysregulation and overactivation of the complement alternative pathway due to genetic mutations have been detected in 40-60% of patients with sporadic or familial atypical HUS.2,4 Triggers include viral illness, pregnancy, malignancy, sepsis, or sporadically with no known inciting event.1 Atypical HUS is a severe disease with a 2-10% risk of mortality, 33% risk of end-stage renal failure, and 50% chance of relapse.5 A 24-year-old female with prior history of atypical HUS at the age of 16 (with response to plasmapheresis) presented to the ER with a 5-day history of fever, chills, sore throat, nausea, vomiting, and dark urine. She tested positive for COVID-19. The exam revealed scleral icterus and scattered petechiae. Labs demonstrated nadir hemoglobin (Hgb) of 9.2 g/dL, platelet count of 52 000k/uL, haptoglobin < 30 mg/dL, peak LDH 1128U/L and creatinine 4.62 mg/dL. Urinalysis is consistent with hemoglobinuria. Schistocytes were noted on the peripheral smear. Rapid streptococcal antigen test and C3, C4, and IgA levels were unremarkable. Chest X-Ray, X-ray KUB, and ultrasound abdomen were unremarkable. The pregnancy test was negative. ADAMTS13 was >100%. Genetic analysis after the initial episode at age 16 revealed autosomal recessive inheritance c.193A > c gene mutations in C3. The patient received IV fluids, ceftriaxone for cystitis, and two units of Fresh Frozen Plasma. She initiated treatment with eculizumab. She also received the MENVEO and meningitis B vaccine per protocol due to the risk of meningitis from terminal complement deficiencies. After 4 infusions of eculizumab, patient's labs improved to platelet count of 307 000 k/uL, Hgb 12.2 g/ dL (nadir 9.2 g/dL), haptoglobin 78 mg/dL normalization of LDH and improved creatinine. Atypical HUS is a rare form of TMAwith mutations in C3 noted in 5% of cases. Complement cascade dysfunction leads to endothelial deposits and microvasculature damage. The resulting prothrombotic state causes obstructive microvascular thrombi predominantly affecting the kidneys but can cause multiorgan dysfunction. The SARS-CoV-2 virus may precipitate atypical HUS relapse due to endothelial damage and complement activation further intensified in patients with existing complement aberrations. Plasma exchange remains a standard of care for atypical HUS, as it effectively removes the antibodies and other proteins. Eculizumab a humanized monoclonal IgG antibody binds to complement proteins, preventing cleavage into C5a and C5b blocking C5b-9(MAC) activation. In patients with CFH, CFI, C3, and CFB mutations, eculizumab is the preferred intervention. Copyright © 2023 Southern Society for Clinical Investigation.

Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Anti-C5a Antibody BDB-001 for Severe COVID-19: A Randomized, Double-Blind, Placebo-Controlled Phase 1 Clinical Trial in Healthy Chinese Adults.

INTRODUCTION: Severe Coronavirus Disease 2019 (COVID-19) progresses with inflammation and coagulation, due to an overactive complement system. Complement component 5a (C5a) plays a key role in the complement system to trigger a powerful "cytokine and chemokine storm" in viral infection. BDB-001, a recombinant human immunoglobulin G4 (IgG4) that specially binds to C5a, has the potential to inhibit the C5a-triggered cytokine storm in treating COVID-19 patients and other inflammation diseases. Here, we have explored its safety, tolerability, pharmacokinetics, and pharmacodynamics in healthy adults. This trial is registered with http://www.chinadrugtrials.org.cn/(CTR20200429 ). METHODS: Thirty-two enrolled participants were randomized into three single-dose cohorts (2, 4, and 8 mg/kg) and 1 multi-dose cohort (4 mg/kg), and received either BDB-001 or placebo (3:1) double-blindly. The safety and tolerability after administration were evaluated for 21 days for single-dose cohorts and 28 days for the multi-dose cohort. The pharmacokinetics of BDB-001 in plasma and pharmacodynamics as free C5a in plasma were analyzed. RESULTS: The incidence of drug-related adverse events (AEs) was low, and all AEs were mild or moderate: neither AEs ≥ 3 (NCI-Common Terminology Criteria For Adverse Events, CTCAE 5.0) nor serious adverse events (SAEs) were found. The area under the concentration-time curve from time zero to 480 h (AUC0-480h), that from time zero to infinity (AUCinf), and peak plasma concentration ©max) increased dose-dependently from 2 to 8 mg/kg in the single-dose cohorts and were characterized by a nonlinear pharmacokinetics of target-mediated drug disposal (TMDD). The accumulation index by AUC0-tau after five administrations (4 mg/kg) from the multi-dose cohort was 6.42, suggesting an accumulation effect. Furthermore, inhibition of C5a at the plasma level was observed. CONCLUSION: The results of this phase I study supported that BDB-001 is a potent anti-C5a inhibitor with safety, tolerability, and no immunogenicity. TRIAL REGISTRATION NUMBER: CTR20200429.

Anti-C5a antibody vilobelimab treatment and the effect on biomarkers of inflammation and coagulation in patients with severe COVID-19: a substudy of the phase 2 PANAMO trial.

We recently reported in the phase 3 PANAMO trial that selectively blocking complement 5a (C5a) with vilobelimab led to improved survival in critically ill COVID-19 patients. C5a is an important contributor to the innate immune system and can also activate the coagulation system. High C5a levels have been reported in severely ill COVID-19 patients and correlate with disease severity and mortality. Previously, we assessed the potential benefit and safety of vilobelimab in severe COVID-19 patients. In the current substudy of the phase 2 PANAMO trial, we aim to explore the effects of vilobelimab on various biomarkers of inflammation and coagulation. Between March 31 and April 24, 2020, 17 patients with severe COVID-19 pneumonia were enrolled in an exploratory, open-label, randomised phase 2 trial. Blood markers of complement, endothelial activation, epithelial barrier disruption, inflammation, neutrophil activation, neutrophil extracellular trap (NET) formation and coagulopathy were measured using enzyme-linked immunosorbent assay (ELISA) or utilizing the Luminex platform. During the first 15 days after inclusion, change in biomarker concentrations between the two groups were modelled with linear mixed-effects models with spatial splines and compared. Eight patients were randomized to vilobelimab treatment plus best supportive care (BSC) and nine patients were randomized to BSC only. A significant decrease over time was seen in the vilobelimab plus BSC group for C5a compared to the BSC only group (p < 0.001). ADAMTS13 levels decreased over time in the BSC only group compared to the vilobelimab plus BSC group (p < 0.01) and interleukin-8 (IL-8) levels were statistically more suppressed in the vilobelimab plus BSC group compared to the BSC group (p = 0.03). Our preliminary results show that C5a inhibition decreases the inflammatory response and hypercoagulability, which likely explains the beneficial effect of vilobelimab in severe COVID-19 patients. Validation of these results in a larger sample size is warranted.

X-ray diffraction data for the C5a-peptidase mutant with modified activity and specificity.

The Streptococcal C5a peptidase (ScpA) specifically inactivates the human complement factor hC5a, a potent anaphylatoxin recently identified as a therapeutic target for treatment of COVID-19 infections. Engineering of ScpA to enhance its potential as a therapeutic will require detailed examination of the basis for its highly selective activity. The emerging view of ScpA and related subtilases is that selection of their substrates is a dynamic two-step process involving flexibility in the domains around the active site and in the C-ter of the substrate. Surface plasmon resonance (SPR) analyses of the ScpA-hC5a interaction have shown that high affinity binding of the substrate is driven by electrostatic interactions between an exosite on the Fn2 domain of the enzyme and the bulky N-ter cleavage product (PN, 'core' residues 1-67) of C5a [1]. Introduction of a D783A mutation in the Fn2 exosite, located approximately 50 Å from the catalytic serine, was shown to significantly reduce substrate binding affinity and k cat of the enzyme. X-ray crystallographic studies on the D783A mutant (ScpAD783A) were undertaken to better interpret the impact of this mutation on the specificity and activity of ScpA. Here we present the 1.9 Å X-ray diffraction data for ScpAD783A and the molecular replacement solution for the structure. Both raw diffraction images and coordinates have been made available on public databases. Additional details on the related SPR and enzyme kinetics analyses on ScpAD783A reported in Jain et al. [2].

Tissue factor in COVID-19-associated coagulopathy.

Evidence of micro- and macro-thrombi in the arteries and veins of critically ill COVID-19 patients and in autopsies highlight the occurrence of COVID-19-associated coagulopathy (CAC). Clinical findings of critically ill COVID-19 patients point to various mechanisms for CAC; however, the definitive underlying cause is unclear. Multiple factors may contribute to the prothrombotic state in patients with COVID-19. Aberrant expression of tissue factor (TF), an initiator of the extrinsic coagulation pathway, leads to thrombotic complications during injury, inflammation, and infections. Clinical evidence suggests that TF-dependent coagulation activation likely plays a role in CAC. Multiple factors could trigger abnormal TF expression and coagulation activation in patients with severe COVID-19 infection. Proinflammatory cytokines that are highly elevated in COVID-19 (IL-1ß, IL-6 and TNF-α) are known induce TF expression on leukocytes (e.g. monocytes, macrophages) and non-immune cells (e.g. endothelium, epithelium) in other conditions. Antiphospholipid antibodies, TF-positive extracellular vesicles, pattern recognition receptor (PRR) pathways and complement activation are all candidate factors that could trigger TF-dependent procoagulant activity. In addition, coagulation factors, such as thrombin, may further potentiate the induction of TF via protease-activated receptors on cells. In this systematic review, with other viral infections, we discuss potential mechanisms and cell-type-specific expressions of TF during SARS-CoV-2 infection and its role in the development of CAC.

Complement Regulation in Immortalized Fibroblast-like Synoviocytes and Primary Human Endothelial Cells in Response to SARS-CoV-2 Nucleocapsid Protein and Pro-Inflammatory Cytokine TNFα.

Background: Case reports are available showing that patients develop symptoms of acute arthritis during or after recovery from SARS-CoV-2 infection. Since the interrelation is still unknown, our aim was to study the impact of the SARS-CoV-2 nucleocapsid protein (NP) on human fibroblast-like synoviocytes and human endothelial cells (hEC) in terms of complement and cytokine regulation. Methods: Non-arthritic (K4IM) synoviocyte, arthritic (HSE) synoviocyte cell lines and primary hEC were stimulated with recombinant NP and/or TNFα. Analyses of cell viability, proliferation, gene and protein expression of cytokines and complement factors were performed. Results: NP suppressed significantly the vitality of hEC and proliferation of HSE. NP alone did not induce any significant changes in the examined gene expressions. However, NP combined with TNFα induced significantly higher TNFα in HSE and K4IM as well as higher IL-6 and CD55 gene expression in HSE and suppressed C3aR1 gene expression in hEC. HSE proliferated twice as fast as K4IM, but showed significantly lesser gene expressions of CD46, CD55, CD59 and TNFα with significantly higher IL-6 gene expression. CD35 gene expression was undetectable in K4IM, HSE and hEC. Conclusions: NP might contribute in combination with other inflammatory factors to complement regulation in arthritis.

Public health impact of booster vaccination against COVID-19 in the UK during Delta variant dominance in autumn 2021.

AIM: To evaluate the public health impact of the UK COVID-19 booster vaccination program in autumn 2021, during a period of SARS-CoV-2 Delta variant predominance. MATERIALS AND METHODS: A compartmental Susceptible-Exposed-Infectious-Recovered model was used to compare age-stratified health outcomes for adult booster vaccination versus no booster vaccination in the UK over a time horizon of September-December 2021, when boosters were introduced in the UK and the SARS-CoV-2 Delta variant was predominant. Model input data were sourced from targeted literature reviews and publicly available data. Outcomes were predicted COVID-19 cases, hospitalizations, post-acute sequelae of COVID-19 (PASC) cases, deaths, and productivity losses averted, and predicted healthcare resources saved. Scenario analyses varied booster coverage, virus infectivity and severity, and time horizon parameters. RESULTS: Booster vaccination was estimated to have averted approximately 547,000 COVID-19 cases, 36,000 hospitalizations, 147,000 PASC cases, and 4,200 deaths in the UK between September and December 2021. It saved over 316,000 hospital bed-days and prevented the loss of approximately 16.5 million paid and unpaid patient work days. In a scenario of accelerated uptake, the booster rollout would have averted approximately 3,400 additional deaths and 25,500 additional hospitalizations versus the base case. A scenario analysis assuming four-fold greater virus infectivity and lower severity estimated that booster vaccination would have averted over 105,000 deaths and over 41,000 hospitalizations versus the base case. A scenario analysis assuming pediatric primary series vaccination prior to adult booster vaccination estimated that expanding vaccination to children aged ≥5 years would have averted approximately 51,000 additional hospitalizations and 5,400 additional deaths relative to adult booster vaccination only. LIMITATIONS: The model did not include the wider economic burden of COVID-19, hospital capacity constraints, booster implementation costs, or non-pharmaceutical interventions. CONCLUSIONS: Booster vaccination during Delta variant predominance reduced the health burden of SARS-CoV-2 in the UK, releasing substantial NHS capacity.

C5a elevation in convalescents from severe COVID-19 is not associated with early complement activation markers C3bBbP or C4d.

Numerous publications have underlined the link between complement C5a and the clinical course of COVID-19. We previously reported that levels of C5a remain high in the group of severely ill patients up to 90 days after hospital discharge. We have now evaluated which complement pathway fuels the elevated levels of C5a during hospitalization and follow-up. The alternative pathway (AP) activation marker C3bBbP and the soluble fraction of C4d, a footprint of the classical/lectin (CP/LP) pathway, were assessed by immunoenzymatic assay in a total of 188 serial samples from 49 patients infected with SARS-CoV-2. Unlike C5a, neither C3bBbP nor C4d readouts rose proportionally to the severity of the disease. Detailed correlation analyses in hospitalization and follow-up samples collected from patients of different disease severity showed significant positive correlations of AP and CP/LP markers with C5a in certain groups, except for the follow-up samples of the patients who suffered from highly severe COVID-19 and presented the highest C5a readouts. In conclusion, there is not a clear link between persistently high levels of C5a after hospital discharge and markers of upstream complement activation, suggesting the existence of a non-canonical source of C5a in patients with a severe course of COVID-19.

ASTHMA, AIRWAY INFLAMMATION AND PTSD ASSOCIATION: RELEVANT MODELS AND A ROLE OF IL17A

Background: There is a growing interest in airway inflammation and mental health. Recent genetic and epidemiological evidence supports an association between PTSD and asthma however, contributory immune mediators/mechanisms are unclear. Recent work from our group employs mouse aeroallergen, house dust mite (HDM) models to examine the role of severe asthma linked inflammatory T helper cells, Th17 and interleukin 17 (IL-17A) in regulating PTSD-relevant behaviors. Methods: A combination of behavioral, immunological, transgenic and transcriptomic approaches were used. 1) BALBc-C5a receptor treatment that shifts Th2 mild asthma phenotype to Th17/IL17a expansion and robust airway inflammation;2) IL-17a receptor knockout mice and 3) RNAseq transcriptomics of cortical and blood brain barrier compromised area, subfornical organ (SFO) tissue was performed. Fear conditioning and extinction was assessed as a PTSD-relevant behavior. Results: Induction of Th17/IL-17 in the BALBc/anti-C5aR1 treated mice resulted in compromised fear extinction and increased fear reinstatement. Absence of IL-17 signaling in IL17Ra deficient mice attenuated HDM effects on fear extinction. Preliminary evidence suggests a potential of the SFO in translating HDM effects to the medial prefrontal cortex, an area regulating fear extinction. Transcriptomic analyses revealed modulation of immune T cell-targeted signaling pathways within the SFO in mice with Th17A expansion. Conclusion: Overall, our work provides novel insights on mechanisms by which mediators of severe airway inflammation, Th17/IL17A regulate fear memory of relevance to PTSD. Beyond asthma-PTSD, our findings have relevant implications for other pulmonary (e.g. COVID-19) and autoimmune inflammatory conditions and mental health.

Exosite binding modulates the specificity of the immunomodulatory enzyme ScpA, a C5a inactivating bacterial protease.

The C5a peptidase from Streptococcus pyogenes (ScpA) is a highly specific enzyme with potential therapeutic value. ScpA is a good model for studying determinants of specificity in the multidomain immunomodulatory enzymes (IMEs), which comprise a large family of bacterial surface proteases. The surface exposed region of ScpA has 5 main domains which includes 3 C-terminal Fn3-like domains (Fn1, Fn2 and Fn3) (Kagawa et al. 2009). Progressive deletion of the Fn3-like domains from the C-ter resulted in loss of enzyme activity and showed an important role for the Fn2 domain in enzyme function. Functional investigation of specific acidic residues on the Fn2 domain identified 3 residues 30-50 Å from the catalytic site (D783, E864 and D889) which impacted to differing degrees on binding and on catalysis, supporting the presence of an exosite on the Fn2. In particular, residue D783 was observed to impact on both substrate binding affinity and the activity of ScpA. A double mutant cycle analysis showed energetic coupling between the targeted ScpA residues and residues in the core portion (residues 1-67) of the C5a substrate. The data supports the presence of a communication network between the active site and the exosite on Fn2. These findings provide a basis for rational engineering of this important enzyme family to enhance stability, activity and/or specificity.

[Biomarkers and functional tests in immediate hypersensitivity to SARS-CoV-2 mRNA vaccines]. / Biomarqueurs et tests fonctionnels dans l'hypersensibilité immédiate aux vaccins ARNm dirigés contre le SARS-CoV-2.

Hypersensitivity to mRNA vaccines directed against SARS-CoV-2 are rare. They may be related to an IgE-dependent mechanism involving PEG contained in vaccines in the form of liposomes. Direct activation of the classical complement pathway (CARPA) has also been strongly suspected. In addition to skin tests, biomarkers have been proposed: anti-PEG antibodies, determination of anaphylatoxins C5a and C3a, or soluble complex C5b-9. Anti-PEG antibodies can be measured by non-standardized in house methods; their presence in post-vaccination reactions against SARS-CoV2 has not been confirmed by all the studies as well as for complement proteins. Mast cell mediators (histamine and tryptase) could rarely be assayed at the time of reaction and their increase is inconstant depending on studies. A slightly elevated baseline tryptase level in some patients suggests that hyper-alphatryptasemia might be involved. A basophil activation test (BAT) can be performed but the results are still preliminary depending on the allergens used: PEG, PEG in the form of liposomes or vaccine itself. The lack of positivity of skin tests in some patients even though basophils are able to be activated in the presence of the same allergen confirms the hypothesis in this case of a possible non-IgE-dependent phenomenon. In conclusion, concerning the exploration of immediate reactions to mRNA vaccines directed against SARS-CoV-2, the place of biological markers requires additional studies in order to better identify the actors and mechanisms involved.