Temporal development and neutralising potential of antibodies against SARS-CoV-2 in hospitalised COVID-19 patients: An observational cohort study

Complement dysregulation is a prevalent and therapeutically amenable feature of long COVID

BACKGROUND

Long COVID encompasses a heterogeneous set of ongoing symptoms that affect many individuals after recovery from infection with SARS-CoV-2. The underlying biological mechanisms nonetheless remain obscure, precluding accurate diagnosis and effective intervention. Complement dysregulation is a hallmark of acute COVID-19 but has not been investigated as a potential determinant of long COVID.

METHODS

We quantified a series of complement proteins, including markers of activation and regulation, in plasma samples from healthy convalescent individuals with a confirmed history of infection with SARS-CoV-2 and age/ethnicity/sex/infection/vaccine-matched patients with long COVID.

FINDINGS

Markers of classical (C1s-C1INH complex), alternative (Ba, iC3b), and terminal pathway (C5a, TCC) activation were significantly elevated in patients with long COVID. These markers in combination had a receiver operating characteristic predictive power of 0.794. Other complement proteins and regulators were also quantitatively different between healthy convalescent individuals and patients with long COVID. Generalized linear modeling further revealed that a clinically tractable combination of just four of these markers, namely the activation fragments iC3b, TCC, Ba, and C5a, had a predictive power of 0.785.

CONCLUSIONS

These findings suggest that complement biomarkers could facilitate the diagnosis of long COVID and further suggest that currently available inhibitors of complement activation could be used to treat long COVID.

FUNDING

This work was funded by the National Institute for Health Research (COV-LT2-0041), the PolyBio Research Foundation, and the UK Dementia Research Institute.

RBD-Protein/Peptide Vaccine UB-612 Elicits Mucosal and Fc-Mediated Antibody Responses against SARS-CoV-2 in Cynomolgus Macaques

Antibodies provide critical protective immunity against COVID-19, and the Fc-mediated effector functions and mucosal antibodies also contribute to the protection. To expand the characterization of humoral immunity stimulated by subunit protein-peptide COVID-19 vaccine UB-612, preclinical studies in non-human primates were undertaken to investigate mucosal secretion and the effector functionality of vaccine-induced antibodies in antibody-dependent monocyte phagocytosis (ADMP) and antibody-dependent NK cell activation (ADNKA) assays. In cynomolgus macaques, UB-612 induced potent serum-neutralizing, RBD-specific IgG binding, ACE2 binding-inhibition antibodies, and antibodies with Fc-mediated effector functions in ADMP and ADNKA assays. Additionally, immunized animals developed mucosal antibodies in bronchoalveolar lavage fluids (BAL). The level of mucosal or serum ADMP and ADNKA antibodies was found to be UB-612 dose-dependent. Our results highlight that the novel subunit UB-612 vaccine is a potent B-cell immunogen inducing polyfunctional antibody responses contributing to anti-viral immunity and vaccine efficacy.

Waning of SARS-CoV-2 Seropositivity among Healthy Young Adults over Seven Months

Background: We conducted a longitudinal study to estimate immunity produced in response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection among university students over seven months. Methods: All participants were attending a public university and resided in Pitt County, North Carolina. University students enrolled weekly for 10 weeks between 26 August 2020 and 28 October 2020, resulting in 136 young adults completing at least one study visit by 17 November 2020. Enrolled students completed an online survey and nasal swab collection at two-week intervals and monthly blood collection between 26 August 2020 and 31 March 2021. Results: Amongst 695 serum samples tested during follow-up, the prevalence of a positive result for anti-nucleocapsid antibodies (N-IgG) was 9.78%. In 22 students with more than one positive N-IgG serum sample, 68.1% of the group lost persistence of N-IgG below the positive threshold over 140 days. Anti-spike IgG antibodies were significantly higher among 11 vaccinated compared to 10 unvaccinated. Conclusions: In healthy young adults, N-IgG wanes below the detectable threshold within five months. S-IgG titer remained consistently elevated months after infection, and significantly increased after vaccination.

On the caveats of a multiplex test for SARS-CoV-2 to detect seroconversion after infection or vaccination

The Covid-19 pandemic, caused by SARS-CoV-2, has resulted in over 6 million reported deaths worldwide being one of the biggest challenges the world faces today. Here we present optimizations of all steps of an enzyme-linked immunosorbent assay (ELISA)-based test to detect IgG, IgA and IgM against the trimeric spike (S) protein, receptor binding domain (RBD), and N terminal domain of the nucleocapsid (N-NTD) protein of SARS-CoV-2. We discuss how to determine specific thresholds for antibody positivity and its limitations according to the antigen used. We applied the assay to a cohort of 126 individuals from Rio de Janeiro, Brazil, consisting of 23 PCR-positive individuals and 103 individuals without a confirmed diagnosis for SARS-CoV-2 infection. To illustrate the differences in serological responses to vaccinal immunization, we applied the test in 18 individuals from our cohort before and after receiving ChAdOx-1 nCoV-19 or CoronaVac vaccines. Taken together, our results show that the test can be customized at different stages depending on its application, enabling the user to analyze different cohorts, saving time, reagents, or samples. It is also a valuable tool for elucidating the immunological consequences of new viral strains and monitoring vaccination coverage and duration of response to different immunization regimens.

Whole blood-based measurement of SARS-CoV-2-specific T cells reveals asymptomatic infection and vaccine immunogenicity in healthy subjects and patients with solid-organ cancers

Accurate assessment of SARS-CoV-2 immunity is critical in evaluating vaccine efficacy and devising public health policies. Whilst the exact nature of effective immunity remains incompletely defined, SARS-CoV-2-specific T-cell responses are a critical feature that will likely form a key correlate of protection against COVID-19. Here, we developed and optimized a high-throughput whole blood-based assay to determine the T-cell response associated with prior SARS-CoV-2 infection and/or vaccination amongst 231 healthy donors and 68 cancer patients. Following overnight in vitro stimulation with SARS-CoV-2-specific peptides, blood plasma samples were analysed for TH 1-type cytokines. Highly significant differential IFN-γ+ /IL-2+ SARS-CoV-2-specific T-cell responses were seen amongst previously infected COVID-19-positive healthy donors in comparison with unknown / naïve individuals (p < 0·0001). IFN-γ production was more effective at identifying asymptomatic donors, demonstrating higher sensitivity (96·0% vs. 83·3%) but lower specificity (84·4% vs. 92·5%) than measurement of IL-2. A single COVID-19 vaccine dose induced IFN-γ and/or IL-2 SARS-CoV-2-specific T-cell responses in 116 of 128 (90·6%) healthy donors, reducing significantly to 27 of 56 (48·2%) when measured in cancer patients (p < 0·0001). A second dose was sufficient to boost T-cell responses in the majority (90·6%) of cancer patients, albeit IFN-γ+ responses were still significantly lower overall than those induced in healthy donors (p = 0·034). Three-month post-vaccination T-cell responses also declined at a faster rate in cancer patients. Overall, this cost-effective standardizable test ensures accurate and comparable assessments of SARS-CoV-2-specific T-cell responses amenable to widespread population immunity testing, and identifies individuals at greater need of booster vaccinations.

Clinical Course of COVID-19 and Cycle Threshold in Patients with Haematological Neoplasms

The SARS-CoV-2 viral load in a respiratory sample can be inversely quantified using the cycle threshold (Ct), defined as the number of amplification cycles required to detect the viral genome in a quantitative PCR assay using reverse transcriptase (RT-qPCR). It may be classified as high (Ct < 25), intermediate (25–30) and low (Ct > 30). We describe the clinical course of 3 patients with haematological neoplasms who contracted COVID-19. None of them had been vaccinated. Firstly, a 22-year-old male with a refractory acute lymphoblastic leukaemia experienced an oligosymptomatic COVID-19 and had a Ct of 23 with an ascending curve. Another male, aged 23, had recently begun treatment for a promyelocytic leukaemia. He had a subacute course with high oxygen requirements. His Ct dropped from 28, when he only experienced fever, to 14.8, during the most critical period and on the edge of ventilatory support. Viral clearance was documented 126 days after the beginning of the symptoms. Finally, a 60-year-old male had received rituximab as maintenance therapy for a follicular lymphoma 3 months before contracting COVID-19. He had a fulminant course and required mechanical ventilation a few days later. We highlight the association between the course of CoViD-19 and the Ct. Viral shedding was longer than in immunocompetent hosts.

COVID-19 vaccine candidates and vaccine development platforms available worldwide

The pandemic caused by the worldwide spread of the coronavirus, which first appeared in 2019, has been named coronavirus disease 19 (COVID-19). More than 4.5 million deaths have been recorded due to the pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), according to the World Health Organization. COVID-19 Dashboard in September 2021. Apart from the wildtype, other variations have been successfully transmitted early in the outbreak although they were not discovered until March 2020. Modifications in the SARS-CoV-2 genetic material, such as mutation and recombination, have the ability to modify the viral life span, along with transitivity, cellular tropism, and symptom severity. Several processes are involved in introducing novel vaccines to the population, including vaccine manufacturing, preclinical studies, Food and Drug Administration permission or certification, processing, and marketing. COVID-19 vaccine candidates have been developed by a number of public and private groups employing a variety of strategies, such as RNA, DNA, protein, and viral vectored vaccines. This comprehensive review, which included the most subsequent evidence on unique features of SARS-CoV-2 and the associated morbidity and mortality, was carried out using a systematic search of recent online databases in order to generate useful knowledge about the COVID-19 updated versions and their consequences on the disease symptoms and vaccine development.

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The ongoing vaccine studies all over the world against the COVID-19 epidemic have been reviewed.

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The effects of different vaccine platforms and new variants on vaccine studies were discussed.

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The effect of vaccines on existing and novel variants was evaluated.

Temporal Associations of the SARS-CoV-2 NP Antigen and Anti-Spike Total Ig Levels with Laboratory Parameters in a Greek Cohort of Hospitalized COVID-19 Patients

Background

The direct effect of SARS-CoV-2 on the lungs results in increased hospitalization rates of patients with pneumonia. Severe COVID-19 patients often develop ARDS which is associated with poor prognosis. Assessing risk factors for COVID-19 severity is indispensable for implementing and evaluating therapeutic interventions. We investigated the temporal associations between the SARS-CoV-2 antigen (Ag), total Immunoglobulin (Ig) levels, and several laboratory parameters in hospitalized patients with varying degrees of COVID-19 severity.

Methods

The SARS-CoV-2 nucleocapsid protein (NP) and total Ig Spike (S) protein-specific antibodies were determined for each patient with lateral flow assays through repeated sampling every two days. Hematological and biochemical parameters were evaluated at the same time points.

Results

40 Greek COVID-19 patients (31 males, 9 females) with a median age of 59.50 ± 16.21 years were enrolled in the study. The median time from symptom onset to hospitalization was 8.0 ± 4.19 days. A significant negative correlation was observed between the SARS-CoV-2 Ag and total Ig levels. The temporal correlation patterns of the SARS-CoV-2 NP Ag and anti-S total Ig levels with laboratory markers varied among patients with differing degrees of COVID-19 severity. Severe-critical cases had lower SARS-CoV-2 Ag and increased total Ig levels as compared to mild-moderate cases.

Conclusions

Distinct temporal profiles of the SARS-CoV-2 NP Ag and anti-S total Ig levels may distinguish different groups of COVID-19 severity.

A Reliable Indirect ELISA Protocol for Detection of Human Antibodies Directed to SARS-CoV-2 NP Protein

A few months ago, the availability of a reliable and cost-effective testing capacity for COVID-19 was a concern for many countries. With the emergence and circulation of new SARS-CoV-2 variants, another layer of challenge can be added for COVID-19 testing at both molecular and serological levels. This is particularly important for the available tests principally designed to target the S gene/protein where multiple mutations have been reported. Herein, the SARS-CoV-2 NP recombinant protein was utilized to develop a simple and reliable COVID-19 NP human IgG ELISA. The optimized protocol was validated against a micro-neutralization (MN) assay, in-house S-based ELISA, and commercial chemiluminescence immunoassay (CLIA). The developed assay provides 100% sensitivity, 98.9% specificity, 98.9% agreement, and high overall accuracy with an area under curve equal to 0.9998 ± 0.0002 with a 95% confidence interval of 0.99 to 1.00. The optical density values of positive samples significantly correlated with their corresponding MN titers. The assay specifically detects IgG antibodies to the SARS-CoV-2 NP protein and does not cross-detect IgG to the viral S protein. Moreover, it does not cross-react with antibodies related to other coronaviruses (e.g., the Middle East respiratory syndrome coronavirus or human coronavirus HKU1). The availability of this reliable COVID-19 NP IgG ELISA protocol is highly valuable for its diagnostic and epidemiological applications.