Correction: Guerrieri et al. Nasal and Salivary Mucosal Humoral Immune Response Elicited by mRNA BNT162b2 COVID-19 Vaccine Compared to SARS-CoV-2 Natural Infection. Vaccines 2021, 9, 1499.

The authors wish to make the following corrections to this paper [...].

Evaluation of the accuracy in the mucosal detection of anti-SARS-CoV-2 antibodies in nasal secretions and saliva.

COVID-19 vaccination with mRNA vaccines induces immune responses capable of neutralizing SARS-CoV-2. Commercially available serological anti-SARS-CoV-2 quantitative and neutralizing assays are essential for the determination of immune responses to vaccines. Nevertheless, at present there is a lack of validated tests to assess the mucosal response to COVID-19 vaccination and standardized analytic and pre-analytic methods have not yet been defined. The aim of our study was to evaluate the accuracy of two diagnostic immunoassays for COVID-19 (ELISA for IgA-S1 and chemiluminescent assay for IgG-RBD) on serum, saliva, and nasal secretions, by the enrollment of three study populations (healthy controls, vaccinated subjects, and subjects recovered from COVID-19 infection). In order to obtain an appropriate cut-off value for the biological matrices studied, ROC curve analyses were performed. Data demonstrate that the analytical and pre-analytical method we have developed can provide accurate and reliable results for the detection of anti-SARS-CoV-2 mucosal specific antibodies (IgA-S1 and IgG-RBD) on saliva and, as a novelty, on nasal secretions, either after COVID-19 infection or in vaccinated subjects.

Evaluation of Hepcidin Level in COVID-19 Patients Admitted to the Intensive Care Unit.

Coronavirus disease 2019 (COVID-19) presents a clinical spectrum that ranges from a mild condition to critical illness. Patients with critical illness present respiratory failure, septic shock and/or multi-organ failure induced by the so called "cytokine storm". Inflammatory cytokines affect iron metabolism, mainly inducing the synthesis of hepcidin, a hormone peptide not routinely measured. High levels of hepcidin have been associated with the severity of COVID-19. The aim of this study was to analyze, retrospectively, the levels of hepcidin in a group of COVID-19 patients admitted to the intensive care unit (ICU) of the Policlinico Tor Vergata of Rome, Italy. Thirty-eight patients from November 2020 to May 2021 were enrolled in the study. Based on the clinical outcome, the patients were assigned to two groups: survivors and non-survivors. Moreover, a series of routine laboratory parameters were monitored during the stay of the patients in the ICU and their levels correlated to the outcome. Statistical differences in the level of hepcidin, D-dimer, IL-6, LDH, NLR, neutrophils level, CRP, TNF-α and transferrin were observed between the groups. In particular, hepcidin values showed significantly different median concentrations (88 ng/mL vs. 146 ng/mL) between survivors and non-survivors. In addition, ROC curves analysis revealed sensitivity and specificity values of 74% and 76%, respectively, at a cut-off of 127 (ng/mL), indicating hepcidin as a good biomarker in predicting the severity and mortality of COVID-19 in ICU patients.

Validation of a quantitative lateral flow immunoassay (LFIA)-based point-of-care (POC) rapid test for SARS-CoV-2 neutralizing antibodies.

With the widespread use of coronavirus disease 2019 (COVID-19) vaccines, a rapid and reliable method to detect SARS-CoV-2 neutralizing antibodies (NAbs) is extremely important for monitoring vaccine effectiveness and immunity in the population. The purpose of this study was to evaluate the performance of the RapiRead™ reader and the TestNOW™ COVID-19 NAb rapid point-of-care (POC) test for quantitative measurement of antibodies against the spike protein receptor-binding domain of severe respiratory syndrome coronavirus 2 (SARS-CoV-2) in different biological matrices compared to chemiluminescence immunoassay (CLIA) methods. Ninety-four samples were collected and analyzed using a RapiRead™ reader and TestNOW™ COVID-19 NAb kits for detecting neutralizing antibodies, and then using two CLIAs. The data were compared statistically using the Kruskal-Wallis test for more than two groups or the Mann-Whitney test for two groups. Specificity and sensitivity were evaluated using a receiver operating characteristic (ROC) curve. Good correlation was observed between the rapid lateral flow immunoassay (LFIA) test system and both CLIA methods. RapiRead™ reader/TestNOW™ COVID-19 NAb vs. Maglumi: correlation coefficient (r) = 0.728 for all patients; r = 0.841 for vaccinated patients. RapiRead™ reader/TestNOW™ COVID-19 NAb vs. Mindray: r = 0.6394 in all patients; r = 0.8724 in vaccinated patients. The time stability of the POC serological test was also assessed considering two times of reading, 12 and 14 minutes. The data revealed no significant differences. The use of a RapiRead™ reader and TestNOW™ COVID-19 NAb assay is a quantitative, rapid, and valid method for detecting SARS-CoV-2 neutralizing antibodies and could be a useful tool for screening studies of SARS-CoV-2 infection and assessing the efficacy of vaccines in a non-laboratory context.

Performance evaluation of four surrogate Virus Neutralization Tests (sVNTs) in comparison to the in vivo gold standard test.

BACKGROUND: Several commercial surrogate Virus Neutralization Tests (sVNTs) have been developed in the last year. Neutralizing anti-SARS-CoV-2 antibodies through interaction with Spike protein Receptor Binding Domain (S-RBD) can block the virus from entering and infecting host cells. However, there is a lack of information about the functional activity of SARS-CoV-2 antibodies that may be associated with protective responses. For these reasons, to counteract viral infection, the conventional virus neutralization test (VNT) is still considered the gold standard. The aim of this study was to contribute more and detailed information about sVNTs' performance, by determining in vitro the anti-SARS-CoV-2 neutralizing antibody concentration using four different commercial assays and then comparing the obtained data to VNT. METHODS: Eighty-eight samples were tested using two chemiluminescence assays (Snibe and Mindray) and two ELISA assays (Euroimmun and Diesse). The antibody titers were subsequently detected and quantified by VNT. RESULTS: The overall agreement between each sVNT and VNT was 95.45% for Euroimmun and 98.86% for Diesse, Mindray and Snibe. Additionally, we investigated whether the sVNTs were closer to the gold standard than traditional anti-SARS-CoV-2 antibody assays S-RBD or S1 based, finding a higher agreement mean value for sVNTs (98.01 ± 1.705% vs 95.45 ± 1.921%; p < 0.05). Furthermore, Spearman's statistical analysis for the correlation of sVNT versus VNT showed r = 0.666 for Mindray; r = 0.696 for Diesse; r = 0.779 for Mindray and r = 0.810 for Euroimmun. CONCLUSIONS: Our data revealed a good agreement between VNT and sVNTs. Despite the VNT still remains the gold standard, the sVNT might be a valuable tool for screening wider populations.

Nasal and Salivary Mucosal Humoral Immune Response Elicited by mRNA BNT162b2 COVID-19 Vaccine Compared to SARS-CoV-2 Natural Infection.

SARS-CoV-2 antibody assays are crucial in managing the COVID-19 pandemic. Approved mRNA COVID-19 vaccines are well known to induce a serum antibody responses against the spike protein and its RBD. Mucosal immunity plays a major role in the fight against COVID-19 directly at the site of virus entry; however, vaccine abilities to elicit mucosal immune responses have not been reported. We detected anti-SARS-CoV-2 IgA-S1 and IgG-RBD in three study populations (healthy controls, vaccinated subjects, and subjects recovered from COVID-19 infection) on serum, saliva, and nasal secretions using two commercial immunoassays (ELISA for IgA-S1 and chemiluminescent assay for IgG-RBD). Our results show that the mRNA BNT162b2 vaccine Comirnaty (Pfizer/BioNTech, New York, NY, USA) determines the production of nasal and salivary IgA-S1 and IgG-RBD against SARS-CoV-2. This mucosal humoral immune response is stronger after the injection of the second vaccine dose compared to subjects recovered from COVID-19. Since there is a lack of validated assays on saliva and nasal secretions, this study shows that our pre-analytical and analytical procedures are consistent with the data. Our findings indicate that the mRNA COVID-19 vaccine elicits antigen-specific nasal and salivary immune responses, and that mucosal antibody assays could be used as candidates for non-invasive monitoring of vaccine-induced protection against viral infection.

Evaluation of serological anti-SARS-CoV-2 chemiluminescent immunoassays correlated to live virus neutralization test, for the detection of anti-RBD antibodies as a relevant alternative in COVID-19 large-scale neutralizing activity monitoring.

The Spike-Receptor Binding Domain (S-RBD) is considered the most antigenic protein in SARS-CoV-2 and probably the key player in SARS-CoV-2 immune response. Quantitative immunoassays may help establish an anti-RBD Abs threshold as an indication of protective immunity. Since different immunoassays are commercial, the standard reference method for the neutralizing activity is the live Virus Neutralization Test (VNT). In this study, anti-RBD IgG levels were detected with two chemiluminescent immunoassays in paucisymptomatic, symptomatic and vaccinated subjects, and their neutralizing activity was correlated to VNT titer, using SARS-CoV-2 original and British variant strains. Both immunoassays confirmed higher anti-RBD Abs levels in vaccinated subjects. Furthermore, despite different anti-RBD Abs median concentrations between the immunoassays, a strong positive correlation with VNT was observed. In conclusion, although the SARS-CoV-2 immune response heterogeneity, the use of immunoassays can help in large-scale monitoring of COVID-19 samples, becoming a valid alternative to VNT test for diagnostic routine laboratories.

Antibody response to COVID-19 vaccine: A point of view that can help to optimize dose distribution.

The global strategy to control coronavirus disease is based on the availability of COVID-19 vaccines. More information about response to a single dose vaccine could help to better understand and optimize the management of the vaccine campaign. Workers from the University of Rome "Tor Vergata" and the University Hospital of University of Rome "Tor Vergata," were monitored during their vaccination program. Serum samples were collected between the first and second dose and after the second dose. University personnel has been vaccinated with two doses of Vaxzevria vaccine 12 weeks apart, while hospital personnel has been vaccinated with two doses of Comirnaty 3 weeks apart. IgG antibodies (Abs) against the Receptor Binding Domain (RBD) of the virus spike surface glycoprotein and neutralizing antibodies (NT) anti-SARS-CoV-2 that block the interaction between RBD and the surface receptor cellular angiotensin converting enzyme (ACE2) were measured using the CL-series Mindray chemiluminescent assays, respectively. Different amounts of antibodies produced after the two doses of vaccine were found. Individuals with a previous natural infection developed a higher Abs titer. Among the individuals with no history of past SARS-CoV-2 infection, 5% had an Abs level of the same order of magnitude of infected people, suggesting that they acquired the infection in an asymptomatic way. In such individuals, one dose of vaccine may be sufficient to obtain a protective immune response.

Lactoferrin as Antiviral Treatment in COVID-19 Management: Preliminary Evidence.

Lactoferrin (Lf), a multifunctional cationic glycoprotein synthesized by exocrine glands and neutrophils, possesses an in vitro antiviral activity against SARS-CoV-2. Thus, we conducted an in vivo preliminary study to investigate the antiviral effect of oral and intranasal liposomal bovine Lf (bLf) in asymptomatic and mild-to-moderate COVID-19 patients. From April 2020 to June 2020, a total of 92 mild-to-moderate (67/92) and asymptomatic (25/92) COVID-19 patients were recruited and divided into three groups. Thirty-two patients (14 hospitalized and 18 in home-based isolation) received only oral and intranasal liposomal bLf; 32 hospitalized patients were treated only with standard of care (SOC) treatment; and 28, in home-based isolation, did not take any medication. Furthermore, 32 COVID-19 negative, untreated, healthy subjects were added for ancillary analysis. Liposomal bLf-treated COVID-19 patients obtained an earlier and significant (p < 0.0001) SARS-CoV-2 RNA negative conversion compared to the SOC-treated and untreated COVID-19 patients (14.25 vs. 27.13 vs. 32.61 days, respectively). Liposomal bLf-treated COVID-19 patients showed fast clinical symptoms recovery compared to the SOC-treated COVID-19 patients. In bLf-treated patients, a significant decrease in serum ferritin, IL-6, and D-dimers levels was observed. No adverse events were reported. These observations led us to speculate a potential role of bLf in the management of mild-to-moderate and asymptomatic COVID-19 patients.

Serological anti-SARS-CoV-2 neutralizing antibodies association to live virus neutralizing test titers in COVID-19 paucisymptomatic/symptomatic patients and vaccinated subjects.

A large number of immunoassays have been developed to detect specific anti-SARS-CoV-2 antibodies; however, not always they are functional to neutralize the virus. The reference test for the anti-spike neutralizing antibodies (nAbs) ability to counteract the viral infection is the virus neutralization test (VNT). Great interest is developing on reliable serological assays allowing antibodies concentration and antibody protective titer correlation. The aim of our study was to detect nAbs serum levels in paucisymptomatic, symptomatic and vaccinated subjects, to find a cut-off value able to protect from virus infection. nAbs serum levels were detected by a competitive automated immunoassay, in association to VNT with the SARS-CoV-2 original and British variant strains. The median nAbs concentrations were: 281.3 BAU/ml for paucisymptomatics; 769.4 BAU/ml for symptomatics; 351.65 BAU/ml for the vaccinated cohort; 983 BAU/ml considering only the second dose vaccinated individuals. The original strain VNT analysis showed 1:80 median neutralization titers in paucisymptomatic and vaccinated subjects; 1:160 in symptomatic patients; 1:160 in the second dose groups. The British variant VNT analysis showed lower neutralization titers in paucisymptomatic and vaccinated groups (1:40); the same titer in symptomatic patients (1:160); the second dose group confirmed the original strain titer (1:160). In conclusion, our data showed optimal correlations with a proportional increase between neutralizing activity and antibody concentration, making nAbs detection a good alternative to virus neutralization assays, difficult to carry out in routine laboratories. Finally, ROC curve analysis established a cut-off of 408.6 BAU/ml to identify subjects with a low risk of infection.

The WHO International Standard for COVID-19 serological tests: towards harmonization of anti-spike assays.

BACKGROUND AND AIMS: SARS-CoV-2 antibody assays are relevant in managing the COVID-19 pandemic, providing valuable data on the immunization status of the population. However, current serology tests are highly variable, due to their different characteristics and to the lack of reference materials. The aim of the World Health Organization (WHO) first International Standard (IS) for anti-SARS-CoV-2 immunoglobulin is to harmonize humoral immune response assessment after natural infection or vaccination, and recommend reporting the results for binding activity in Binding Antibody Units (BAU). MATERIALS AND METHODS: This study analyzed six commercial quantitative anti-SARS-CoV-2 S-protein assays in a head-to-head comparison, using the manufacturers' conversion factors for the WHO IS to obtain BAU/mL values. RESULTS: Our data showed good alignment up to 1000 BAU/mL, then began to disperse, exhibiting some discrepancies. Moreover, correlations among methods varied with Cohen's Kappa ranging from 0.580 to 1.00, with the lowest agreement values for kits using different target antigens or different antibody isotypes, making it clear that the laboratory report should include this information. Values expressed as BAU/ml showed a reduced between-assays variability compared to AU/ml (median coefficients of variation 0.38 and 0.68, respectively; p < 0.001). CONCLUSION: On the basis of these data at present anti-SARS CoV-2 serological assays' results are not interchangeable, and, more importantly, individual immune monitoring should be performed with the same method.

Evaluation of S-RBD and high specificity ACE-2-binding antibodies on SARS-CoV-2 patients after six months from infection.

The antibody response to SARS-CoV-2 has not yet fully defined, but the availability of sensitive and specific serological assays is crucial to observe the presence of specific antibodies against the human receptor binding domain (S-RBD) and high specificity ACE-2-binding antibodies or neutralizing antibodies (NT) in response to vaccines. Indeed, these peculiar antibodies should prevent viral interaction between RBD and Angiotensin-Converting Enzyme 2 (ACE2) receptor, located on surface of host cells. In this study, 72 samples from 37 hospitalized COVID-19 patients and 35 not-hospitalized patients were analyzed longitudinally. The detection of S-RBD and NT antibodies was carried out using CLIA tests. Hospitalized patients showed elevated serum levels of S-RBD (97.22%) and NT (77.78%) antibodies, differently, not-hospitalized, who were paucisymptomatic or asymptomatic patients, showed lower serum levels of S-RBD (65.71%) and NT (38.14%) antibodies. The results suggest that the NT serum level is strongly related to disease severity (p < 0.001) and to the serum level of S-RBD antibodies (p < 0.0001).

Lactoferrin Against SARS-CoV-2: In Vitro and In Silico Evidences.

Lactoferrin (Lf) is a cationic glycoprotein synthetized by exocrine glands and is present in all human secretions. It is also secreted by neutrophils in infection and inflammation sites. This glycoprotein possesses antimicrobial activity due to its capability to chelate two ferric ions per molecule, as well as to interact with bacterial and viral anionic surface components. The cationic features of Lf bind to cells, protecting the host from bacterial and viral injuries. Its anti-inflammatory activity is mediated by the ability to enter inside the nucleus of host cells, thus inhibiting the synthesis of proinflammatory cytokine genes. In particular, Lf down-regulates the synthesis of IL-6, which is involved in iron homeostasis disorders and leads to intracellular iron overload, favoring viral replication and infection. The well-known antiviral activity of Lf has been demonstrated against DNA, RNA, and enveloped and naked viruses and, therefore, Lf could be efficient in counteracting also SARS-CoV-2 infection. For this purpose, we performed in vitro assays, proving that Lf exerts an antiviral activity against SARS-COV-2 through direct attachment to both SARS-CoV-2 and cell surface components. This activity varied according to concentration (100/500 µg/ml), multiplicity of infection (0.1/0.01), and cell type (Vero E6/Caco-2 cells). Interestingly, the in silico results strongly supported the hypothesis of a direct recognition between Lf and the spike S glycoprotein, which can thus hinder viral entry into the cells. These in vitro observations led us to speculate a potential supplementary role of Lf in the management of COVID-19 patients.

Circulating calprotectin as a supporting inflammatory marker in discriminating SARS-CoV-2 infection: an observational study.

OBJECTIVE AND DESIGN: Fecal calprotectin (CLP) is widely known for its detection in stools of patients with inflammatory bowel diseases (IBDs), to investigate the intestinal inflammatory status. Current research is promoting the circulating protein role as a systemic inflammatory marker. However, most studies report serum calprotectin analysis although plasma assay prevents its massive release by granulocytes. In this perspective, the ongoing SARS-CoV-2 pandemic deserves deployment of convenient and easy-to-dose markers that could reliably address the state of infection. METHODS: We analyzed serum circulating calprotectin (cCLP) levels in hospitalized COVID-19 patients and plasma cCLP levels from patients with suspected SARS-CoV-2 infection, then assessed negative or positive on molecular tests. RESULTS: Our results confirm a significant circulating calprotectin increase in infected subjects respect to controls, in serum and plasma. Moreover, plasma calprotectin has higher levels in suspected patients with positive SARS-CoV-2-RT-PCR, compared to suspected patients with negative SARS-CoV-2-RT-PCR. Furthermore, ROC curves results showed the circulating plasma calprotectin discriminatory ability to differentiate infected SARS-CoV-2 patients at a cutoff value greater than 131.3 ng/ml. CONCLUSIONS: Our data propose circulating calprotectin as a new, quantitative and predictive marker, which in addition to being an interesting generic inflammatory marker may provide important indications in SARS-CoV-2 infection.

Low Vitamin D Status at Admission as a Risk Factor for Poor Survival in Hospitalized Patients With COVID-19: An Italian Retrospective Study.

OBJECTIVE: Preliminary findings suggest a relationship between lower serum 25-hydroxyvitamin D [25(OH)D] levels and incidence and severity of COVID-19. The aim of this study was to evaluate the relationship between vitamin D status at admission and different markers of inflammation, coagulation, and sepsis in hospitalized patients with COVID-19. METHOD: We conducted a retrospective study on 137 consecutive patients with SARS-CoV-2 infection and available data on serum 25(OH)D levels, who were admitted to our Institution between March 1 and April 30, 2020. Patients were divided into two groups: survivors (n = 78; 57%) and non-survivors (n = 59; 43%). RESULTS: At admission, all patients showed hypovitaminosis D. Median total serum 25(OH)D levels at admission were significantly higher in survivors than non-survivors (12 ng/mL vs 8 ng/mL; p < 0.01). Non-survivors exhibited significantly higher median levels of white blood cell (WBC) count, neutrophil-to-lymphocyte count ratio (NLR), high-sensitivity C-reactive protein (hsCRP), ferritin, interleukin 6 (IL-6), D-dimer, fibrinogen, and procalcitonin (PCT) compared to survivors at three different time points during hospitalization. In a multivariate analysis performed by a logistic regression model, serum 25(OH)D levels were significantly inversely associated with risk of COVID-19-related in-hospital mortality (odds ratio, 0.91; 95% confidence interval, 0.85-0.98; p = 0.01). According to receiver operating characteristic curve analysis, hsCRP, NLR, ferritin, and D-dimer were the best predictive biomarkers for poor prognosis of COVID-19, whereas IL-6, PCT, fibrinogen, 25(OH)D, WBC count, and tumor necrosis factor alpha (TNF-α) may serve as supportive biomarkers for worse clinical course of the disease. CONCLUSIONS: We found a markedly high prevalence (100%) of hypovitaminosis D in patients admitted to hospital with COVID-19, suggesting a possible role of low vitamin D status in increasing the risk of SARS-CoV-2 infection and subsequent hospitalization. The inverse association between serum 25(OH)D levels and risk of in-hospital mortality observed in our cohort suggests that a lower vitamin D status upon admission may represent a modifiable and independent risk factor for poor prognosis in COVID-19.

Clinical validation of a second generation anti-SARS-CoV-2 IgG and IgM automated chemiluminescent immunoassay.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has proven to be extremely contagious and has spread rapidly all over the world. A key aspect in limiting the virus diffusion is to ensure early and accurate diagnosis. Serological assays could be an alternative in increasing testing capabilities, particularly when used as part of an algorithmic approach combined with molecular analysis. The aim of this study was to evaluate the diagnostic accuracy of a second generation chemiluminescent automated immunoassay able to detect anti-SARS-CoV-2 immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies. Data are carried out on healthy subjects and other infectious diseases pre-pandemic sera, as controls, and on two different coronavirus disease 2019 hospitalized patient groups (early and late infection time). Data obtained have been analyzed in terms of precision, linearity, sensitivity and specificity. Specificities are: 100% for anti-SARS-CoV-2 IgG and 98% for anti-SARS-CoV-2 IgM, in all patient groups. Sensitivities are: 97%, 100%, and 98% for anti-SARS-CoV-2 IgG and 87%, 83%, and 86% for anti-SARS-CoV-2 IgM in the early infection, in the late infection and in the total patient group, respectively. The Mindray anti-SARS-CoV-2 IgG and IgM assays demonstrated higher sensitivity and specificity, indicating that IgG and IgM simultaneous detection is useful even in the early phases of infection.

Anti-phospholipids antibodies and immune complexes in COVID-19 patients: a putative role in disease course for anti-annexin-V antibodies.

INTRODUCTION: Besides distinctive respiratory and digestive hallmarks, COVID-19 has been recently associated with a high prevalence of pro-inflammatory and hypercoagulable states known as "COVID-19 Associated Coagulopathy" (CAC), corresponding to a worsening in patients' conditions, whose causes are still to be elucidated. A link between anti-phospholipid antibodies (aPLs) and viral infections has long been suggested. APLs are assessed for anti-phospholipid syndrome (APS) diagnosis, characterized by thrombocytopenia, thrombosis, and coagulopathy. Furthermore, circulating immune complexes (CICs), arisen upon inflammatory responses and related immune dysregulation, can lead to endothelial cell damage and thrombotic complications. METHOD: We performed an extended panel including IgG/IgM anti-cardiolipin, IgG/IgM anti-ß2-glycoprotein-1, coupled with IgG/IgM anti-prothrombin, IgG/IgM anti-annexin-V on two COVID-19 patient groups (early and late infection time), and a negative control group. IgG CIC analysis followed to evaluate inflammatory status, through a possible complement system activation. RESULTS: Our results showed low positive case percentage in IgG/IgM anti-cardiolipin and IgG/IgM anti-ß2-glycoprotein-1 assays (4.54%, 6.25%, and 4.55%; in early infection group, late infection group, and control group, respectively); few positive cases in IgG/IgM anti-prothrombin and IgG/IgM anti-annexin-V immunoassays; and no IgG CIC positivity in any patient. CONCLUSIONS: In conclusion, our data show a low aPL prevalence, likely excluding an involvement in the pathogenesis of CAC. Interestingly, IgG/IgM anti-prothrombin and anti-annexin-V positive cases, detected in late infection group, suggest that aPLs could temporarily increase or could trigger a "COVID-19-induced-APS-like-syndrome" in predisposed patients. Key Points • To our knowledge, anti-prothrombin (aPT) antibodies, anti-annexin-V antibodies and CICs in COVID-19 patients have not been reported in the scientific literature. • Lack of uniformity and the low percentage of aCL/aß2GP1 positivity preclude a putative role in CAC pathogenesis. • IgG/IgM anti-prothrombin and IgG/IgM anti-annexin-V data show that distribution of positive case number increases in late infection patients, significantly in anti-annexin-V results, suggesting a possible role for these anti-phospholipid antibodies in disease course. • aPLs can arise transiently in some patients with critical illness and SARS-CoV-2 infection (disappearing in a few weeks), as well as in other genetically predisposed patients; they could trigger a "COVID-19-induced-APS-like-syndrome".

Evaluation of a new simultaneous anti-SARS-CoV-2 IgA, IgM and IgG screening automated assay based on native inactivated virus.

In addition to molecular testing, there is evolving interest for anti-SARS-CoV-2 antibodies serologic assays. Majority of them focus on IgM/IgG despite IgA important role in mucosal immunity. A simultaneous anti-SARS-CoV-2 IgA/IgG/IgM immunoassay, performed on an automated instrument by ELISA kit coated with native inactivated SARS-CoV-2, was detected on two control groups (negative swab healthcare workers; pre-pandemic healthy or with other viral infections individuals) and on two COVID-19 patient groups (early and late infection). Specificities were 100% in all groups, indicating no cross-reactivity with other infectious or pre-pandemic sera. Sensitivities were 94% in early infection group and 97% in total positive patient group, reaching 100% in late infection group. To our knowledge, this is the first technique based on native SARS-CoV-2. It is able to identify more positive samples than kits using recombinant antigens, therefore virus native epitopes as well as simultaneous anti-SARS-CoV-2 IgA/IgM/IgG detection could help to contain COVID-19 spreading.