Tinzaparin-a review of its molecular profile, pharmacology, special properties, and clinical uses.

PURPOSE: Low molecular weight heparins (LMWHs) are a group of heterogenous moieties, long used in the prevention and treatment of thrombosis. They derive from heparin and since they are prepared by different methods of depolymerization, they differ in pharmacokinetic properties and anticoagulant profiles, and thus are not clinically interchangeable. METHODS: In this review we provide an overview of tinzaparin's main characteristics and uses. RESULTS: Tinzaparin which is produced by the enzymatic depolymerization of unfractionated heparin (UFH) can be used for the treatment and prevention of deep venous thrombosis (DVT) and pulmonary embolism (PE); it has been also used in special populations such as elders, obese, pregnant women, and patients with renal impairment and/or cancer with favorable outcomes in both safety and efficacy, with a once daily dose regimen. Furthermore, LMWHs are extensively used in clinical practice for both thromboprophylaxis and thrombosis treatment of COVID-19 patients. CONCLUSION: Tinzaparin features support the hypothesis for having a role in immunothrombosis treatment (i.e. in the context of cancer ,COVID-19), interfering not only with coagulation cascade but also exhibiting anti-inflammatory potency.

Persisting Endothelial Cell Activation and Hypercoagulability after COVID-19 Recovery—The Prospective Observational ROADMAP-Post COVID-19 Study

Background. Hypercoagulable state and endothelial cell activation are common alterations in patients with COVID-19. Nevertheless, the hypothesis of persistent hypercoagulability and endothelial cell activation following recovery from COVID-19 remains an unresolved issue. Objectives. To investigate the persistence of endothelial cell activation and hypercoagulability after recovery from COVID-19. Patients/Methods. COVID-19 survivors (n = 208) and 30 healthy individuals were enrolled in this study. The following biomarkers were measured: procoagulant phospholipid-dependent clotting time (PPL-ct), D-Dimer, fibrin monomers (FM), free Tissue factor pathway inhibitor (free-TFP)I, heparinase, and soluble thrombomodulin (sTM). Antibodies against SARS-CoV-2 (IgG and IgA) were also measured. Results. The median interval between symptom onset and screening for SARS-CoV-2 antibodies was 62 days (IQR = 22 days). Survivors showed significantly higher levels of D-Dimers, FM, TFPI, and heparanase as compared to that of the control group. Survivors had significantly shorter PPL-ct. Elevated D-dimer was associated with older age. Elevated FM was associated with female gender. Elevated heparanase was independently associated with male gender. Decreased Procoag-PPL clotting time was associated with female gender. One out of four of COVID-19 survivors showed increase at least one biomarker of endothelial cell activation or hypercoagulability. Conclusions. Two months after onset of COVID-19, a significant activation of endothelial cells and in vivo thrombin generation persists in at least one out of four survivors of COVID-19. The clinical relevance of these biomarkers in the diagnosis and follow-up of patients with long COVID-19 merits to be evaluated in a prospective clinical study.

Adverse effects of COVID-19 mRNA vaccines: the spike hypothesis.

Vaccination is a major tool for mitigating the coronavirus disease 2019 (COVID-19) pandemic, and mRNA vaccines are central to the ongoing vaccination campaign that is undoubtedly saving thousands of lives. However, adverse effects (AEs) following vaccination have been noted which may relate to a proinflammatory action of the lipid nanoparticles used or the delivered mRNA (i.e., the vaccine formulation), as well as to the unique nature, expression pattern, binding profile, and proinflammatory effects of the produced antigens - spike (S) protein and/or its subunits/peptide fragments - in human tissues or organs. Current knowledge on this topic originates mostly from cell-based assays or from model organisms; further research on the cellular/molecular basis of the mRNA vaccine-induced AEs will therefore promise safety, maintain trust, and direct health policies.

Characterizing Kinetics and Avidity of SARS-CoV-2 Antibody Responses in COVID-19 Greek Patients.

In-depth understanding of the immune response provoked by SARS-CoV-2 infection is necessary, as there is a great risk of reinfection and a difficulty in achieving herd immunity due to a decline in both antibody concentration and avidity. Avidity testing, however, could overcome variability in the immune response associated with sex or clinical symptoms, and thus differentiate between recent and past infections. In this context, here, we analyzed SARS-CoV-2 antibody kinetics and avidity in Greek hospitalized (26%) and non-hospitalized (74%) COVID-19 patients (N = 71) in the course of up to 15 months after their infection to improve the accuracy of the serological diagnosis in dating the onset of the infection. The results showed that IgG-S1 levels decline significantly at four months (p = 0.0239) in both groups of patients and are higher in hospitalized ones (up to 2.1-fold, p < 0.001). Additionally, hospitalized patients' titers drop greatly and are equalized to non-hospitalized ones only at a time-point of twelve to fifteen months. Antibody levels of women in total remain more stable months after infection, compared to men. Furthermore, we examined the differential maturation of IgG avidity after SARS-CoV-2 infection, showing an incomplete maturation of avidity that results in a plateau at four months after infection. We also defined 38.2% avidity (sensitivity: 58.9%, specificity: 90.91%) as an appropriate "cut-off" that could be used to determine the stage of infection before avidity reaches a plateau.

Immunostimulation and Coagulopathy in COVID-19 Compared to Patients With H1N1 Pneumonia or Bacterial Sepsis.

BACKGROUND/AIM: Multiple reports from all over the world link COVID-19 with endothelial/coagulation disorders as well as a dysregulated immune response. This study tested the hypothesis that immunostimulation will be greater in COVID-19 patients than in patients with H1N1 infection or bacterial sepsis. Also, whether an increase in immune stimulation will be accompanied by a more severely affected endothelium/coagulation system was examined. PATIENTS AND METHODS: Twenty-three septic patients, admitted in the Intensive Care Unit (ICU), were enrolled (9 with SARS-CoV-2, 5 with H1N1 pneumonia, 9 with bacterial sepsis). Myeloperoxidase (MPO) activity along with certain endothelial/coagulation factors were assessed on admission (time point 1) and at either improvement or deterioration (time point 2). RESULTS: MPO levels were significantly higher in COVID-19 patients compared to both other groups. Furthermore, in patients with COVID-19, vWF levels did not differ significantly, fVIII levels were lower while ADAMTS-13 activity was higher compared to patients with H1N1 pneumonia and bacterial sepsis (a trend in the latter). CONCLUSION: Increased immunostimulation was noted in COVID-19 patients compared to other septic patients; however, this was not accompanied by greater disturbance of the clotting system and/or more severe endothelial injury.

Genetic prediction of ICU hospitalization and mortality in COVID-19 patients using artificial neural networks.

There is an unmet need of models for early prediction of morbidity and mortality of Coronavirus disease-19 (COVID-19). We aimed to a) identify complement-related genetic variants associated with the clinical outcomes of ICU hospitalization and death, b) develop an artificial neural network (ANN) predicting these outcomes and c) validate whether complement-related variants are associated with an impaired complement phenotype. We prospectively recruited consecutive adult patients of Caucasian origin, hospitalized due to COVID-19. Through targeted next-generation sequencing, we identified variants in complement factor H/CFH, CFB, CFH-related, CFD, CD55, C3, C5, CFI, CD46, thrombomodulin/THBD, and A Disintegrin and Metalloproteinase with Thrombospondin motifs (ADAMTS13). Among 381 variants in 133 patients, we identified 5 critical variants associated with severe COVID-19: rs2547438 (C3), rs2250656 (C3), rs1042580 (THBD), rs800292 (CFH) and rs414628 (CFHR1). Using age, gender and presence or absence of each variant, we developed an ANN predicting morbidity and mortality in 89.47% of the examined population. Furthermore, THBD and C3a levels were significantly increased in severe COVID-19 patients and those harbouring relevant variants. Thus, we reveal for the first time an ANN accurately predicting ICU hospitalization and death in COVID-19 patients, based on genetic variants in complement genes, age and gender. Importantly, we confirm that genetic dysregulation is associated with impaired complement phenotype.

Kinetics of Nucleocapsid, Spike and Neutralizing Antibodies, and Viral Load in Patients with Severe COVID-19 Treated with Convalescent Plasma.

COVID-19 is an ongoing pandemic with high morbidity and mortality. Despite meticulous research, only dexamethasone has shown consistent mortality reduction. Convalescent plasma (CP) infusion might also develop into a safe and effective treatment modality on the basis of recent studies and meta-analyses; however, little is known regarding the kinetics of antibodies in CP recipients. To evaluate the kinetics, we followed 31 CP recipients longitudinally enrolled at a median of 3 days post symptom onset for changes in binding and neutralizing antibody titers and viral loads. Antibodies against the complete trimeric Spike protein and the receptor-binding domain (Spike-RBD), as well as against the complete Nucleocapsid protein and the RNA binding domain (N-RBD) were determined at baseline and weekly following CP infusion. Neutralizing antibody (pseudotype NAb) titers were determined at the same time points. Viral loads were determined semi-quantitatively by SARS-CoV-2 PCR. Patients with low humoral responses at entry showed a robust increase of antibodies to all SARS-CoV-2 proteins and Nab, reaching peak levels within 2 weeks. The rapid increase in binding and neutralizing antibodies was paralleled by a concomitant clearance of the virus within the same timeframe. Patients with high humoral responses at entry demonstrated low or no further increases; however, virus clearance followed the same trajectory as in patients with low antibody response at baseline. Together, the sequential immunological and virological analysis of this well-defined cohort of patients early in infection shows the presence of high levels of binding and neutralizing antibodies and potent clearance of the virus.

SARS-CoV-2 antibody kinetics eight months from COVID-19 onset: Persistence of spike antibodies but loss of neutralizing antibodies in 24% of convalescent plasma donors.

Elucidating the characteristics of human immune response against SARS-CoV-2 is of high priority and relevant for determining vaccine strategies. We report the results of a follow-up evaluation of anti-SARS-CoV-2 antibodies in 148 convalescent plasma donors who participated in a phase 2 study at a median of 8.3 months (range 6.8-10.5 months) post first symptom onset. Monitoring responses over time, we found contraction of antibody responses for all four antigens tested, with Spike antibodies showing higher persistence than Nucleocapsid antibodies. A piecewise linear random-effects multivariate regression analysis showed a bi-phasic antibody decay with a more pronounced decrease during the first 6 months post symptoms onset by analysis of two intervals. Interestingly, antibodies to Spike showed better longevity whereas their neutralization ability contracted faster. As a result, neutralizing antibodies were detected in only 76% of patients at the last time point. In a multivariate analysis, older age and hospitalization were independently associated with higher Spike, Spike-RBD, Nucleocapsid, N-RBD antibodies and neutralizing antibody levels. Results on persistence and neutralizing ability of anti-SARS-CoV-2 antibodies, especially against Spike and Spike-RBD, should be considered in the design of future vaccination strategies.

High Prevalence of Anti-PF4 Antibodies Following ChAdOx1 nCov-19 (AZD1222) Vaccination Even in the Absence of Thrombotic Events.

It is unclear whether the ChAdOx1 nCov-19 vaccine can induce the development of anti-PF4 antibodies in vaccinated individuals who have not developed thrombosis. The aim of this prospective study was to evaluate the presence of antibodies against heparin/PF4 in adults who received a first dose of the ChAdOx1 nCov-19 vaccine, and correlate them with clinical data and antibody responses to the vaccine. We detected non-platelet activating anti-PF4 antibodies in 67% (29/43) of the vaccinated individuals on day 22 following the first dose of the ChAdOx1 nCov-19 vaccine, though these were detected in low titers. Furthermore, there was no correlation between the presence of anti-PF4 IgG antibodies and the baseline clinical characteristics of the patients. Our findings suggest that the ChAdOx1 nCov-19 vaccine can elicit anti-PF4 antibody production even in recipients without a clinical manifestation of thrombosis. The presence of anti-PF4 antibodies was not sufficient to provoke clinically evident thrombosis. Our results offer an important insight into the ongoing investigations regarding the underlying multifactorial pathophysiology of thrombotic events induced by the ChAdOx1 nCov-19 vaccine.

Accurate SARS-CoV-2 seroprevalence surveys require robust multi-antigen assays.

There is a plethora of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) serological tests based either on nucleocapsid phosphoprotein (N), S1-subunit of spike glycoprotein (S1) or receptor binding domain (RBD). Although these single-antigen based tests demonstrate high clinical performance, there is growing evidence regarding their limitations in epidemiological serosurveys. To address this, we developed a Luminex-based multiplex immunoassay that detects total antibodies (IgG/IgM/IgA) against the N, S1 and RBD antigens and used it to compare antibody responses in 1225 blood donors across Greece. Seroprevalence based on single-antigen readouts was strongly influenced by both the antigen type and cut-off value and ranged widely [0.8% (95% CI 0.4-1.5%)-7.5% (95% CI 6.0-8.9%)]. A multi-antigen approach requiring partial agreement between RBD and N or S1 readouts (RBD&N|S1 rule) was less affected by cut-off selection, resulting in robust seroprevalence estimation [0.6% (95% CI 0.3-1.1%)-1.2% (95% CI 0.7-2.0%)] and accurate identification of seroconverted individuals.

SARS-CoV-2 Infection Is Asymptomatic in Nearly Half of Adults with Robust Anti-Spike Protein Receptor-Binding Domain Antibody Response.

Between June and November 2020, we assessed plasma antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid protein in 4996 participants (aged 18-82 years, 34.5% men) from the National and Kapodistrian University of Athens. The weighted overall prevalence was 1.6% and monthly prevalence correlated with viral RNA-confirmed SARS-CoV-2 infections in Greece, in the same period. Notably, 49% of seropositive cases reported no history of SARS-CoV-2 infection-related clinical symptoms and 33% were unsuspected of their previous infection. Additionally, levels of anti-SARS-CoV-2 antibodies against the spike-protein receptor-binding domain were similar between symptomatic and asymptomatic individuals, irrespective of age and gender. Using Food and Drug Administration Emergency Use Authorization-approved assays, these results support the need for such studies on pandemic evaluation and highlight the development of robust humoral immune responses even among asymptomatic individuals. The high percentage of unsuspected/asymptomatic active cases, which may contribute to community transmission for more days than that of cases who are aware and self-isolate, underscores the necessity of measures across the population for the efficient control of the pandemic.

Peripheral Blood Immune Profiling of Convalescent Plasma Donors Reveals Alterations in Specific Immune Subpopulations Even at 2 Months Post SARS-CoV-2 Infection.

Immune profiling of patients with COVID-19 has shown that SARS-CoV-2 causes severe lymphocyte deficiencies (e.g., lymphopenia, decreased numbers, and exhaustion of T cells) and increased levels of pro-inflammatory monocytes. Peripheral blood (PB) samples from convalescent plasma (CP) donors, COVID-19 patients, and control subjects were analyzed by multiparametric flow cytometry, allowing the identification of a wide panel of immune cells, comprising lymphocytes (T, B, natural killer (NK) and NKT cells), monocytes, granulocytes, and their subsets. Compared to active COVID-19 patients, our results revealed that the immune profile of recovered donors was restored for most subpopulations. Nevertheless, even 2 months after recovery, CP donors still had reduced levels of CD4+ T and B cells, as well as granulocytes. CP donors with non-detectable levels of anti-SARS-CoV-2-specific antibodies in their serum were characterized by higher Th9 and Th17 cells, which were possibly expanded at the expense of Th2 humoral immunity. The most noticeable alterations were identified in previously hospitalized CP donors, who presented the lowest levels of CD8+ regulatory T cells, the highest levels of CD56+CD16- NKT cells, and a promotion of a Th17-type phenotype, which might be associated with a prolonged pro-inflammatory response. A longer follow-up of CP donors will eventually reveal the time needed for full recovery of their immune system competence.

Peripheral Blood Immune Profiling of Convalescent Plasma Donors Reveals Alterations in Specific Immune Subpopulations Even at 2 Months Post SARS-CoV-2 Infection

Immune profiling of patients with COVID-19 has shown that SARS-CoV-2 causes severe lymphocyte deficiencies (e.g., lymphopenia, decreased numbers, and exhaustion of T cells) and increased levels of pro-inflammatory monocytes. Peripheral blood (PB) samples from convalescent plasma (CP) donors, COVID-19 patients, and control subjects were analyzed by multiparametric flow cytometry, allowing the identification of a wide panel of immune cells, comprising lymphocytes (T, B, natural killer (NK) and NKT cells), monocytes, granulocytes, and their subsets. Compared to active COVID-19 patients, our results revealed that the immune profile of recovered donors was restored for most subpopulations. Nevertheless, even 2 months after recovery, CP donors still had reduced levels of CD4+ T and B cells, as well as granulocytes. CP donors with non-detectable levels of anti-SARS-CoV-2-specific antibodies in their serum were characterized by higher Th9 and Th17 cells, which were possibly expanded at the expense of Th2 humoral immunity. The most noticeable alterations were identified in previously hospitalized CP donors, who presented the lowest levels of CD8+ regulatory T cells, the highest levels of CD56+CD16−NKT cells, and a promotion of a Th17-type phenotype, which might be associated with a prolonged pro-inflammatory response. A longer follow-up of CP donors will eventually reveal the time needed for full recovery of their immune system competence.

Anti-SARS-CoV-2 Antibody Responses in Convalescent Plasma Donors Are Increased in Hospitalized Patients; Subanalyses of a Phase 2 Clinical Study.

We evaluated the antibody responses in 259 potential convalescent plasma donors for Covid-19 patients. Different assays were used: a commercial ELISA detecting antibodies against the recombinant spike protein (S1); a multiplex assay detecting total and specific antibody isotypes against three SARS-CoV-2 antigens (S1, basic nucleocapsid (N) protein and receptor-binding domain (RBD)); and an in-house ELISA detecting antibodies to complete spike, RBD and N in 60 of these donors. Neutralizing antibodies (NAb) were also evaluated in these 60 donors. Analyzed samples were collected at a median time of 62 (14-104) days from the day of first symptoms or positive PCR (for asymptomatic patients). Anti-SARS-CoV-2 antibodies were detected in 88% and 87.8% of donors using the ELISA and the multiplex assay, respectively. The multivariate analysis showed that age ≥50 years (p < 0.001) and need for hospitalization (p < 0.001) correlated with higher antibody titers, while asymptomatic status (p < 0.001) and testing >60 days after symptom onset (p = 0.001) correlated with lower titers. Interestingly, pseudotype virus-neutralizing antibodies (PsNAbs) significantly correlated with spike and with RBD antibodies by ELISA. Sera with high PsNAb also showed a strong ability to neutralize active SARS-CoV-2 virus, with hospitalized patients showing higher titers. Therefore, convalescent plasma donors can be selected based on the presence of high RBD antibody titers.

The Emerging Role of Convalescent Plasma in the Treatment of COVID-19.

Various agents are currently under evaluation as potential treatments in the fight against coronavirus disease 2019 (COVID-19). Plasma from patients that have overcome COVID-19 infection, referred to as convalescent plasma, is a treatment option with considerable background in viral diseases such as Spanish influenza, H1N1, Ebola, Severe Acute Respiratory Syndrome (SARS), and Middle East Respiratory Syndrome (MERS). Although convalescent plasma has historically proven beneficial in the treatment of some viral diseases, its use is still explorative in the context of COVID-19. To date, preliminary evidence from case series is favorable as significant clinical, biochemical improvement and hospital discharge have been reported. A detailed overview of randomized as well non-randomized trials of treatment with convalescent plasma, which have been registered worldwide, is provided in this review. Based on these studies, data from thousands of patients is anticipated in the near future. Convalescent plasma seems to be a safe option, but potential risks such as transfusion-related acute lung injury and antibody-dependent enhancement are discussed. Authorities including the Food and Drug Administration (FDA), and scientific associations such as the International Society of Blood Transfusion (ISBT) and the European Blood Alliance (EBA), have provided guidance into the selection criteria for donors and recipients. A debatable, pivotal issue pertains to the optimal timing of convalescent plasma transfusion. This treatment should be administered as early as possible to maximize efficacy, but at the same time be reserved for severe cases. Emerging risk stratification algorithms integrating clinical and biochemical markers to trace the cases at risk of significant deterioration can prove valuable in this direction.

Hematological findings and complications of COVID-19.

COVID-19 is a systemic infection with a significant impact on the hematopoietic system and hemostasis. Lymphopenia may be considered as a cardinal laboratory finding, with prognostic potential. Neutrophil/lymphocyte ratio and peak platelet/lymphocyte ratio may also have prognostic value in determining severe cases. During the disease course, longitudinal evaluation of lymphocyte count dynamics and inflammatory indices, including LDH, CRP and IL-6 may help to identify cases with dismal prognosis and prompt intervention in order to improve outcomes. Biomarkers, such high serum procalcitonin and ferritin have also emerged as poor prognostic factors. Furthermore, blood hypercoagulability is common among hospitalized COVID-19 patients. Elevated D-Dimer levels are consistently reported, whereas their gradual increase during disease course is particularly associated with disease worsening. Other coagulation abnormalities such as PT and aPTT prolongation, fibrin degradation products increase, with severe thrombocytopenia lead to life-threatening disseminated intravascular coagulation (DIC), which necessitates continuous vigilance and prompt intervention. So, COVID-19 infected patients, whether hospitalized or ambulatory, are at high risk for venous thromboembolism, and an early and prolonged pharmacological thromboprophylaxis with low molecular weight heparin is highly recommended. Last but not least, the need for assuring blood donations during the pandemic is also highlighted.