Identifying immune markers driving early and effective antibody response in patients with severe coronavirus disease 2019 (COVID-19) is critical due to the threat of future coronavirus pandemics, incomplete global vaccination, and suboptimal booster coverage. Patients with life-threatening severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are characterized by dysregulated thromboinflammation and cytokine storm that could influence the isotype virus-specific antibody response and the subsequent clinical outcome. We investigated the association between COVID-19-related mortality with the dynamics, magnitude, and relative avidity of nucleoprotein (N), spike (S), and receptor-binding domain (RBD)-specific IgM, IgA, and IgG in circulation. We also assessed the relationship between the virus-specific antibody responses and cytokine patterns, as well as systemic and pulmonary thromboinflammation markers. This multicenter study included COVID-19 patients hospitalized early in the pandemic, classified as survivors (n=62) and non-survivors (n=17). We developed indirect enzyme-linked immunosorbent assays (ELISAs) to evaluate each virus-specific isotype using well-characterized outpatient COVID-19 (n=180) and pre-pandemic cohorts (n=111). The pro-inflammatory interleukin (IL)-6 and tumor necrosis factor (TNF)-α, as well as the regulatory IL-10, transforming growth factor (TGF)-β1, and soluble tumor necrosis factor receptor I (sTNFRI) levels were evaluated. The ELISAs performed highly for all virus-specific isotypes, although modest for IgM-N. Non-survivors increased N-specific, but no S-specific, IgM and IgA responses throughout the disease course and, more notably, a delayed class switching to IgG-S and IgG-RBD compared to survivors. No differences were observed in the virus-specific IgG relative avidity. Survivors exhibited an antibody response proportional to the degree of systemic and pulmonary thromboinflammation, whereas non-survivors showed those dissociated because of their uncontrolled severe thromboinflammation. Only the survivors showed a dominant regulatory cytokine pattern in the early phase of infection (<10 days after symptoms onset), which strongly correlated with developing IgG-S and IgG-RBD protective antibodies. We developed easy-to-use immune assays that enable patient monitoring and identify at-risk populations in low- to middle-income regions. Non-survivors displayed an ineffective N-mediated antibody response, marked by an inability to control inflammation and a compromised time-dependent class switching toward S and RBD-specific IgG. The regulatory cytokine axis, including TGF-β1, maybe a critical immune correlate of effective antibody-mediated immunity in COVID-19.

Since SARS-CoV-2 has caused unprecedented changes in the epidemiology of other infectious diseases, investigations on coinfection between SARS-CoV-2 and one of the famous vector-borne diseases, malaria, are crucial for disease control, especially in malaria-endemic areas. The clinical profiles, possible mechanisms for interactions, and representative control measures of COVID-19 and malaria coinfections have recently garnered public attention. The overlap in epidemiology, infection incubation, and clinical symptoms between COVID-19 and malaria coinfections has been thoroughly discussed to provide a detailed diagnostic procedure for coinfections, thereby guiding appropriate clinical interventions. Immunological and genetic evidence has shown that previous malaria exposure may protect the body from the poor prognosis of COVID-19. ACE2 downregulation and TLR-induced pathways play a role in this protective effect, as do CD8 + and CD4 + T-cell activation and coinhibitory receptor upregulation, which help maintain a balance of immune reactions. Finally, multiple control measures for coinfections were discussed, and malaria control efforts were enriched in the context of COVID-19. These efforts included (1) developing vaccinations; (2) evaluating the efficacy of anti-malarial drugs in the SARS-CoV-2 treatment; (3) exploring recent advances in natural products that are potentially useful for coinfection treatment; (4) researching and implementing bioinsecticides for malaria control, such as gene-driven mosquitoes, fungi, and bacterial symbionts; and (5) improving national electronic disease surveillance platforms in malaria-endemic regions. At last, the above findings summarized valuable lessons about malaria and COVID-19 control and expedite further investigations on coinfections with complex clinical presentations.

Most individuals show immunity to SARS-CoV-2 from vaccination or infection, or both. We aimed to determine the safety and immunogenicity of an omicron-containing COVID-19 vaccine (mRNA-1273.222) in vaccine-naive adolescents who were SARS-CoV-2 positive.

Part 3 of the phase 2/3 TeenCOVE trial was a phase 3, open-label, single-arm part done in the USA and the Dominican Republic that enrolled healthy, vaccine-naive adolescents (aged 12-17 years) to receive two 50 μg doses of mRNA-1273.222 (ancestral strain Wuhan-Hu-1 and omicron subvariants BA.4 and BA.5), 6 months apart. Primary reactogenicity and safety outcomes included assessment of solicited local or systemic adverse reactions 7 days after vaccination, and unsolicited and prespecified adverse events throughout study participation. Inferred effectiveness (primary immunogenicity outcome) was established by comparing neutralising antibody responses 28 days after dose 1 of mRNA-1273.222 in SARS-CoV-2-positive adolescents with responses 28 days after dose 2 of mRNA-1273 100 μg primary series in SARS-CoV-2-negative young adults (aged 18-25 years) from the COVE trial. This study is registered with ClinicalTrials.gov (NCT04649151).

Between Dec 21, 2022, and June 5, 2023, 379 adolescents (378 of whom were SARS-CoV-2 positive) received at least one mRNA-1273.222 dose and were included in the safety analysis set. The reactogenicity profile was favourable compared with the mRNA-1273 primary series, with no new safety concerns identified. Unsolicited adverse events were reported in 49 (13%) of 379 participants; no deaths or adverse events leading to study discontinuation were reported. The immunogenicity set included 245 adolescents from the per-protocol immunogenicity subset who were SARS-CoV-2 positive at baseline and 296 young adults who were SARS-CoV-2 negative. Compared with the mRNA-1273 primary series in SARS-CoV-2-negative young adults, a single dose of mRNA-1273.222 induced superior (geometric mean ratio [GMR] 95% CI lower bound >1) neutralising antibody responses against omicron BA.4 and BA.5 (GMR 48·95 [95% CI 44·21-54·21]) and non-inferior (GMR 95% CI lower bound >0·667) neutralising antibody responses against ancestral SARS-CoV-2 (GMR 4·25 [95% CI 3·69-4·88]) in SARS-CoV-2-positive adolescents.

In vaccine-naive, SARS-CoV-2-positive adolescents, single-dose mRNA-1273.222 was effective against COVID-19 based on successful immunobridging to the two-dose mRNA-1273 primary series in young adults. The findings support a simplified single-dose vaccination schedule with variant-containing mRNA vaccines, regardless of previous vaccination status.

Moderna.

Given the low levels of coronavirus disease 2019 (COVID-19) vaccine coverage in sub-Saharan Africa (sSA), despite high levels of natural severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) exposures, strategies for extending the breadth and longevity of naturally acquired immunity are warranted. Designing such strategies will require a good understanding of naturally acquired immunity.

We measured whole-spike immunoglobulin G (IgG) and spike-receptor binding domain (RBD) total immunoglobulins (Igs) on 585 plasma samples collected longitudinally over five successive time points within six months of COVID-19 diagnosis in 309 COVID-19 patients. We measured antibody-neutralising potency against the wild-type (Wuhan) SARS-CoV-2 pseudovirus in a subset of 51 patients over three successive time points. Binding and neutralising antibody levels and potencies were then tested for correlations with COVID-19 severities.

Rates of seroconversion increased from day 0 (day of PCR testing) to day 180 (six months) (63.6% to 100 %) and (69.3 % to 97%) for anti-spike-IgG and anti-spike-RBD binding Igs, respectively. Levels of these binding antibodies peaked at day 28 (p<0.01) and were subsequently maintained for six months without significant decay (p>0.99). Similarly, antibody-neutralising potencies peaked at day 28 (p<0.01) but declined by three-fold, six months after COVID-19 diagnosis (p<0.01). Binding antibody levels were highly correlated with neutralising antibody potencies at all the time points analysed (r>0.60, p<0.01). Levels and potencies of binding and neutralising antibodies increased with disease severity.

Most COVID-19 patients generated SARS-CoV-2 specific binding antibodies that remained stable in the first six months of infection. However, the respective neutralising antibodies decayed three-fold by month-six of COVID-19 diagnosis suggesting that they are short-lived, consistent with what has been observed elsewhere in the world. Thus, regular vaccination boosters are required to sustain the high levels of anti-SARS-CoV-2 naturally acquired neutralising antibody potencies in our population.

R-loops are three-stranded RNA-DNA hybrid structures that play important regulatory roles, but excessive or deregulated R-loops formation can trigger DNA damage and genome instability. Digestion of R-loops is mainly relying on the action of two specialized ribonucleases: RNaseH1 and RNaseH2. RNaseH2 is the main enzyme carrying out the removal of misincorporated rNMPs during DNA replication or repair, through the Ribonucleotide Excision Repair (RER) pathway. We have recently shown that the human RNA helicase DDX3X possessed RNaseH2-like activity, being able to substitute RNaseH2 in reconstituted RER reactions. Here, using synthetic R-loop mimicking substrates, we could show that human DDX3X alone was able to both displace and degrade the ssRNA strand hybridized to DNA. Moreover, DDX3X was found to physically interact with human RNaseH2. Such interaction suppressed the nuclease and helicase activities of DDX3X, but stimulated severalfold the catalytic activity of the trimeric RNaseH2, but not of RNaseH1. Finally, silencing of DDX3X in human cells caused accumulation of RNA-DNA hybrids and phosphorylated RPA foci. These results support a role of DDX3X as a scaffolding protein and auxiliary factor for RNaseH2 during R-loop degradation.

SARS-CoV-2 pandemic still poses a significant burden on global health and economy, especially for symptoms persisting beyond the acute disease. COVID-19 manifests with various degrees of severity and the identification of early biomarkers capable of stratifying patient based on risk of progression could allow tailored treatments.

We longitudinally analyzed 67 patients, classified according to a WHO ordinal scale as having Mild, Moderate, or Severe COVID-19. Peripheral blood samples were prospectively collected at hospital admission and during a 6-month follow-up after discharge. Several subsets and markers of the innate and adaptive immunity were monitored as putative factors associated with COVID-19 symptoms.

More than 50 immunological parameters were associated with disease severity. A decision tree including the main clinical, laboratory, and biological variables at admission identified low NK-cell precursors and CD14+CD91+ monocytes, and high CD8+ Effector Memory T cell frequencies as the most robust immunological correlates of COVID-19 severity and reduced survival. Moreover, low regulatory B-cell frequency at one month was associated with the susceptibility to develop long COVID at six months, likely due to their immunomodulatory ability.

These results highlight the profound perturbation of the immune response during COVID-19. The evaluation of specific innate and adaptive immune-cell subsets allows to distinguish between different acute and persistent COVID-19 symptoms.

SARS-CoV-2 has rampantly spread around the globe and continues to cause unprecedented loss through ongoing waves of (re)infection. Increasing our understanding of the protection against infection with SARS-CoV-2 is critical to ending the pandemic. Serological assays have been widely used to assess immune responses, but secretory antibodies, the essential first line of defense, have been studied to only a limited extent. Of particular interest and importance are neutralizing antibodies, which block the binding of the spike protein of SARS-CoV-2 to the human receptor angiotensin-converting enzyme-2 (ACE2) and thus are essential for immune defense. Here, we employed Microfluidic Diffusional Sizing (MDS), an immobilization-free technology, to characterize neutralizing antibody affinity to SARS-CoV-2 spike receptor-binding domain (RBD) and spike trimer in saliva. Affinity measurement was obtained through a contrived sample and buffer using recombinant SARS-CoV-2 RBD and monoclonal antibody. Limited saliva samples demonstrated that MDS applies to saliva neutralizing antibody measurement. The ability to disrupt a complex of ACE2-Fc and spike trimer is shown. Using a quantitative assay on the patient sample, we determined the affinity and binding site concentration of the neutralizing antibodies.

Globally, over 772 million cases of COVID-19 have been reported. New variants of interest with corresponding spikes in case numbers continue to be identified. Vulnerable patients, including older adults or patients with severe comorbidities, continue to be at risk. A large body of evidence has been accumulated regarding anti-SARS-CoV-2-antibodies and COVID-19 but the usefulness of antibody measurements remains unclear. This systematic review aims to assess the prognostic value of anti-SARS-CoV-2-antibodies and their usefulness for guiding booster vaccinations.

Studies in English and published between January 2020 and October 2023 were included. Studies that relied on multiparameter-models or comprised fewer than 100 participants were excluded. PubMed and via the WHO COVID-19 research database, Embase and Medline databases were searched. Study selection and quality assessment was conducted independently by two researchers.

After screening 1,160 studies, 33 studies comprising >30 million individuals were included. Anti-SARS-CoV-2-antibodies were strongly associated with reduced risk of SARS-CoV-2-infection and better outcomes, including mortality. Risk of infection and COVID-19 severity decreased with increasing antibody levels.

Anti-SARS-CoV-2-antibodies are useful for early identification of high-risk patients and timely adjustment of therapy. Protective thresholds may be applied to advise booster vaccinations but verification in separate cohorts is required.

To gain insight into how immunity develops against SARS-CoV-2 from 2020 to 2022, we analyzed the immune response of a small group of university staff and students who were either infected or vaccinated. We investigated the levels of receptor-binding domain (RBD)-specific and nucleocapsid (N)-specific IgG and IgA antibodies in serum and saliva samples taken early (around 10 days after infection or vaccination) and later (around 1 month later), as well as N-specific T-cell responses. One patient who had been infected in 2020 developed serum RBD and N-specific IgG antibodies, but declined eight months later, then mRNA vaccination in 2021 produced a higher level of anti-RBD IgG than natural infection. In the vaccination of naïve individuals, vaccines induced anti-RBD IgG, but it declined after six months. A third vaccination boosted the IgG level again, albeit to a lower level than after the second. In 2022, when the Omicron variant became dominant, familial transmission occurred among vaccinated people. In infected individuals, the levels of serum anti-RBD IgG antibodies increased later, while anti-N IgG peaked earlier. The N-specific activated T cells expressing IFN γ or CD107a were detected only early. Although SARS-CoV-2-specific salivary IgA was undetectable, two individuals showed a temporary peak in RBD- and N-specific IgA antibodies in their saliva on the second day after infection. Our study, despite having a small sample size, revealed that SARS-CoV-2 infection triggers the expected immune responses against acute viral infections. Moreover, our findings suggest that the temporary mucosal immune responses induced early during infection may provide better protection than the currently available intramuscular vaccines.

There is a growing trend in using saliva for SARS-CoV-2 detection with reasonable accuracy. We have studied the responses of IgA, IgG, and IgM in human saliva by directly comparing disease with control analyzing two-trace two-dimensional correlation spectra (2T2D-COS) employing Fourier transform infrared (FTIR) spectra. It explores the molecular-level variation between control and COVID-19 saliva samples. The advantage of 2T2D spectra is that it helps in discriminating remarkably subtle features between two simple pairs of spectra. It gives spectral information from highly overlapped bands associated with different systems. The clinical findings from 2T2D show the decrease of IgG and IgM salivary antibodies in the 50, 60, 65, and 75-years COVID-19 samples. Among the various COVID-19 populations studied the female 30-years group reveals defense mechanisms exhibited by IgM and IgA. Lipids and fatty acids decrease, resulting in lipid oxidation due to the SARS-CoV-2 in the samples studied. Study shows salivary thiocyanate plays defense against SARS-CoV-2 in the male population in 25 and 35 age groups. The receiver operation characteristics statistical method shows a sensitivity of 98% and a specificity of 94% for the samples studied. The measure of accuracy computed as F score and G score has a high value, supporting our study's validation. Thus, 2T2D-COS analysis can potentially monitor the progression of immunoglobulin's response function to COVID-19 with reasonable accuracy, which could help diagnose clinical trials. KEY MESSAGES: The molecular profile of salivary antibodies is well resolved and identified from 2T2D-COS FTIR spectra. The IgG antibody plays a significant role in the defense mechanism against SARS-CoV-2 in 25-40 years. 2T2D-COS reveals the absence of salivary thiocyanate in the 40-75 years COVID-19 population. The receiver operation characteristic (ROC) analysis validates our study with high sensitivity and specificity.

Much of the global population now has some level of adaptive immunity to SARS-CoV-2 induced by exposure to the virus (natural infection), vaccination, or a combination of both (hybrid immunity). Key questions that subsequently arise relate to the duration and the level of protection an individual might expect based on their infection and vaccination history. A multi-component composite correlate of risk (CoR) could inform individuals and stakeholders about protection and aid decision making. This perspective evaluates the various elements that need to be accommodated in the development of an antibody-based composite CoR for reinfection with SARS-CoV-2 or development of severe COVID-19, including variation in exposure dose, transmission route, viral genetic variation, patient factors, and vaccination status. We provide an overview of antibody dynamics to aid exploration of the specifics of SARS-CoV-2 antibody testing. We further discuss anti-SARS-CoV-2 immunoassays, sample matrices, testing formats, frequency of sampling and the optimal time point for such sampling. While the development of a composite CoR is challenging, we provide our recommendations for each of these key areas and highlight areas that require further work to be undertaken.

Virus-specific antibodies are crucial for protective immunity against SARS-CoV-2. Assessing functional antibodies through conventional or pseudotyped virus neutralisation tests (pVNT) requires high biosafety levels. Alternatively, the virus-free surrogate virus neutralisation test (sVNT) quantifies antibodies interfering with spike binding to angiotensin-converting enzyme 2. We evaluated secreted nanoluciferase-tagged spike protein fragments as diagnostic antigens in the sVNT in a vaccination cohort. Initially, spike fragments were tested in a capture enzyme immunoassay (EIA), identifying the receptor binding domain (RBD) as the optimal diagnostic antigen. The sensitivity of the in-house sVNT applying the nanoluciferase-labelled RBD equalled or surpassed that of a commercial sVNT (cPass, GenScript Diagnostics) and an in-house pVNT four weeks after the first vaccination (98% vs. 94% and 72%, respectively), reaching 100% in all assays four weeks after the second and third vaccinations. When testing serum reactivity with Omicron BA.1 spike, the sVNT and pVNT displayed superior discrimination between wild-type- and variant-specific serum reactivity compared to a capture EIA. This was most pronounced after the first and second vaccinations, with the third vaccination resulting in robust, cross-reactive BA.1 construct detection. In conclusion, utilising nanoluciferase-labelled antigens permits the quantification of SARS-CoV-2-specific inhibitory antibodies. Designed as flexible modular systems, the assays can be readily adjusted for monitoring vaccine efficacy.

Infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induces rapid production of IgM, IgA, and IgG antibodies directed to multiple viral antigens that may have impact diverse clinical outcomes.

We evaluated IgM, IgA, and IgG antibodies directed to the nucleocapsid (NP), IgA and IgG to the Spike protein and to the receptor-binding domain (RBD), and the presence of neutralizing antibodies (nAb), in a cohort of unvaccinated SARS-CoV-2 infected individuals, in the first 30 days of post-symptom onset (PSO) (T1).

This study included 193 coronavirus disease 2019 (COVID-19) participants classified as mild, moderate, severe, critical, and fatal and 27 uninfected controls. In T1, we identified differential antibody profiles associated with distinct clinical presentation. The mild group presented lower levels of anti-NP IgG, and IgA (vs moderate and severe), anti-NP IgM (vs severe, critical and fatal), anti-Spike IgA (vs severe and fatal), and anti-RBD IgG (vs severe). The moderate group presented higher levels of anti-RBD IgA, comparing with severe group. The severe group presented higher levels of anti-NP IgA (vs mild and fatal) and anti-RBD IgG (vs mild and moderate). The fatal group presented higher levels of anti-NP IgM and anti-Spike IgA (vs mild), but lower levels of anti-NP IgA (vs severe). The levels of nAb was lower just in mild group compared to severe, critical, and fatal groups, moreover, no difference was observed among the more severe groups. In addition, we studied 82 convalescent individuals, between 31 days to 6 months (T2) or more than 6 months (T3), PSO, those: 12 mild, 26 moderate, and 46 severe plus critical. The longitudinal analyzes, for the severe plus critical group showed lower levels of anti-NP IgG, IgA and IgM, anti-Spike IgA in relation T3. The follow-up in the fatal group, reveals that the levels of anti-spike IgG increased, while anti-NP IgM levels was decreased along the time in severe/critical and fatal as well as anti-NP IgG and IgA in several/critical groups.

In summary, the anti-NP IgA and IgG lower levels and the higher levels of anti-RBD and anti-Spike IgA in fatal compared to survival group of individuals admitted to the intensive care unit (ICU). Collectively, our data discriminate death from survival, suggesting that anti-RBD IgA and anti-Spike IgA may play some deleterious effect, in contrast with the potentially protective effect of anti-NP IgA and IgG in the survival group.

The incidence of diabetes in childhood has increased during the COVID-19 pandemic. Elucidating whether SARS-CoV-2 infection is associated with islet autoimmunity, which precedes type 1 diabetes onset, is relevant to disease etiology and future childhood diabetes trends.

To determine whether there is a temporal relationship between SARS-CoV-2 infection and the development of islet autoimmunity in early childhood.

Between February 2018 and March 2021, the Primary Oral Insulin Trial, a European multicenter study, enrolled 1050 infants (517 girls) aged 4 to 7 months with a more than 10% genetically defined risk of type 1 diabetes. Children were followed up through September 2022.

SARS-CoV-2 infection identified by SARS-CoV-2 antibody development in follow-up visits conducted at 2- to 6-month intervals until age 2 years from April 2018 through June 2022.

The development of multiple (≥2) islet autoantibodies in follow-up in consecutive samples or single islet antibodies and type 1 diabetes. Antibody incidence rates and risk of developing islet autoantibodies were analyzed.

Consent was obtained for 885 (441 girls) children who were included in follow-up antibody measurements from age 6 months. SARS-CoV-2 antibodies developed in 170 children at a median age of 18 months (range, 6-25 months). Islet autoantibodies developed in 60 children. Six of these children tested positive for islet autoantibodies at the same time as they tested positive for SARS-CoV-2 antibodies and 6 at the visit after having tested positive for SARS-CoV-2 antibodies. The sex-, age-, and country-adjusted hazard ratio for developing islet autoantibodies when the children tested positive for SARS-CoV-2 antibodies was 3.5 (95% CI, 1.6-7.7; P = .002). The incidence rate of islet autoantibodies was 3.5 (95% CI, 2.2-5.1) per 100 person-years in children without SARS-CoV-2 antibodies and 7.8 (95% CI, 5.3-19.0) per 100 person-years in children with SARS-CoV-2 antibodies (P = .02). Islet autoantibody risk in children with SARS-CoV-2 antibodies was associated with younger age (<18 months) of SARS-CoV-2 antibody development (HR, 5.3; 95% CI, 1.5-18.3; P = .009).

In young children with high genetic risk of type 1 diabetes, SARS-CoV-2 infection was temporally associated with the development of islet autoantibodies.

(1) Background: Coronavirus proteins are quite conserved amongst endemic strains (eCoV) and SARS-CoV-2. We aimed to evaluate whether peptide epitopes might serve as useful diagnostic biomarkers to stratify previous infections and COVID-19. (2) Methods: Peptide epitopes were identified at an amino acid resolution that applied a novel statistical approach to generate data sets of potential antibody binding peptides. (3) Results: Data sets from more than 120 COVID-19 or eCoV-infected patients, as well as vaccinated persons, have been used to generate data sets that have been used to search in silico for potential epitopes in proteins of SARS-CoV-2 and eCoV. Peptide epitopes were validated with >300 serum samples in synthetic peptide micro arrays and epitopes specific for different viruses, in addition to the identified cross reactive epitopes. (4) Conclusions: Most patients develop antibodies against non-structural proteins, which are useful general markers for recent infections. However, there are differences in the epitope patterns of COVID-19, and eCoV, and the S-protein vaccine, which can only be explained by a high degree of cross-reactivity between the viruses, a pre-existing immune response against some epitopes, and even an alternate processing of the vaccine proteins.

COVID-19 has affected the entire world due to the rapid spread of SARS-CoV-2, mainly through airborne particles from saliva, which, being easily obtained, help monitor the progression of the disease. Fourier transform infrared (FTIR) spectra combined with chemometric analysis could increase the diagnostic efficiency of the disease. However, two-dimensional correlation spectroscopy (2DCOS) is superior to conventional spectra as it helps to resolve the minute overlapped peaks. In this work, we aimed to use 2DCOS and receiver operating characteristic (ROC) analyses to compare the immune response in saliva associated with COVID-19, which could be important in biomedical diagnosis. FTIR spectra of human saliva samples from male (575) and female (366) patients ranging from 20 to 82 ± 2 years of age were used for the study. Age groups were segregated as G1 (25-40 ± 2 years), G2 (45-60 ± 2 years), and G3 (65-80 ± 2 years). The results of the 2DCOS analysis showed biomolecular changes in response to SARS-CoV-2. 2DCOS analyses of the male G1 + (1579,1644) and -(1531,1598) crossover peaks evidenced changes such as amide I > IgG. Female G1 crossover peaks -(1504,1645), (1504,1545) and -(1391,1645) resulted in amide I > IgG > IgM. The asynchronous spectra in 1300-900 cm-1 of the G2 male group showed that IgM is more important in diagnosing infections than IgA. Female G2 asynchronous spectra -(1027,1242) and + (1068,1176) showed that IgA > IgM is produced against SARS-CoV-2. The G3 male group evidenced antibody changes in IgG > IgM. The absence of IgM in the female G3 population diagnoses a specifically targeted immunoglobulin associated with sex. Moreover, ROC analysis showed sensitivity (85-89 % men; 81-88 % women) and specificity (90-93 % men; 78-92 % women) for the samples studied. The general classification performance (F1 score) of the studied samples is high for the male (88-91 %) and female (80-90 %) populations. This high PPV (positive predictive value) and NPV (negative predictive value) verify our segregation of COVID-19 positive and negative sample groups. Therefore, 2DCOS with ROC analysis using FTIR spectra have the potential for a non-invasive approach to monitoring COVID-19.

Recent evidence suggests a role for Diabetes Mellitus in adverse outcomes from COVID-19 infection; yet the underlying mechanisms are not clear. Moreover, attention has turned to prophylactic vaccination to protect the population from COVID-19-related illness and mortality. We performed a comprehensive peer-reviewed literature search on an array of key terms concerning diabetes and COVID-19 seeking to address the following questions: 1. What role does diabetes play as an accelerator for adverse outcomes in COVID-19?; 2. What mechanisms underlie the differences in outcomes seen in people with diabetes?; 3. Are vaccines against COVID-19 efficacious in people with diabetes? The current literature demonstrates that diabetes is associated with an increased risk of adverse outcomes from COVID-19 infection, and post-COVID sequelae. Potential mechanisms include dysregulation of Angiotensin Converting Enzyme 2, Furin, CD147, and impaired immune cell responses. Hyperglycaemia is a key exacerbator of these mechanisms. Limited studies are available on COVID-19 vaccination in people with diabetes; however, the current literature suggests that vaccination is protective against adverse outcomes for this population. In summary, people with diabetes are a high-risk group that should be prioritised in vaccination efforts. Glycaemic optimisation is paramount to protecting this group from COVID-19-associated risk. Unsolved questions remain as to the molecular mechanisms underlying the adverse outcomes seen in people with diabetes; the functional impact of post-COVID symptoms on people with diabetes, their persistence, and management; how long-term vaccine efficacy is affected by diabetes, and the antibody levels that confer protection from adverse outcomes in COVID-19.

Antibody measurements play a central role in the diagnosis of many autoimmune and infectious diseases. One antibody detection technology, Luciferase Immunoprecipitation Systems (LIPS), utilizes genetically encoded recombinant luciferase antigen fusion proteins in an immunoglobulin capture format to generate robust antibody measurement with high diagnostic sensitivity and specificity. The LIPS technology has been highly useful in detecting antibodies for research diagnostics and the discovery of new autoantigens. The methodology of the assay requires immunoglobulin binding reagents such as protein A/G beads and washing steps to process the immune complex before antibody levels are measured by light production with a luminometer. Recently, simplified mix and read immunoassays based on split components of the nanoluciferase enzyme in a complementation format have been developed for antibody measurements without requiring immunoglobulin-capturing beads or washing steps. The mix and read immunoassays utilize two or three nanoluciferase fragments which when reconstituted via antigen-specific antibody binding generate a functional enzyme. At present, these split luciferase tests have been developed mainly for detecting SARS-CoV-2 antibodies. Here, we describe the traditional LIPS technology and compare it to the new split luciferase methodologies focusing on their technical features, strengths, limitations, and future opportunities for diagnostic research, and clinical applications.

Viral shedding and neutralizing antibody (NAb) dynamics among patients hospitalized with severe coronavirus disease 2019 (COVID-19) and immune correlates of protection have been key questions throughout the pandemic. We investigated the duration of reverse transcriptase-polymerase chain reaction (RT-PCR) positivity, infectious viral shedding and NAb titers as well as the association between NAb titers and disease severity in hospitalized COVID-19 patients in Denmark 2020-2021.

Prospective single-center observational cohort study of 47 hospitalized COVID-19 patients. Oropharyngeal swabs were collected at eight time points during the initial 30 days of inclusion. Serum samples were collected after a median time of 7 (IQR 5 - 10), 37 (IQR 35 - 38), 97 (IQR 95 - 100), and 187 (IQR 185 - 190) days after symptom onset. NAb titers were determined by an in-house live virus microneutralization assay. Viral culturing was performed in Vero E6 cells.

Patients with high disease severity had higher mean log2 NAb titers at day 37 (1.58, 95% CI [0.34 -2.81]), 97 (2.07, 95% CI [0.53-3.62]) and 187 (2.49, 95% CI [0.20- 4.78]) after symptom onset, compared to patients with low disease severity. Peak viral load (0.072, 95% CI [- 0.627 - 0.728]), expressed as log10 SARS-CoV-2 copies/ml, was not associated with disease severity. Virus cultivation attempts were unsuccessful in almost all (60/61) oropharyngeal samples collected shortly after hospital admission.

We document an association between high disease severity and high mean NAb titers at days 37, 97 and 187 after symptom onset. However, peak viral load during admission was not associated with disease severity.

The study is registered at https://clinicaltrials.gov/ (NCT05274373).

Neutralizing antibodies (NAbs) are central players in the humoral immunity that defends the body from SARS-CoV-2 infection by blocking viral entry into host cells and neutralizing their biological effects. Even though NAbs primarily work by neutralizing viral antigens, on some occasions, they may also combat the SARS-CoV-2 virus escaping neutralization by employing several effector mechanisms in collaboration with immune cells like natural killer (NK) cells and phagocytes. Besides their prophylactic and therapeutic roles, antibodies can be used for COVID-19 diagnosis, severity evaluation, and prognosis assessment in clinical practice. Furthermore, the measurement of NAbs could have key implications in determining individual or herd immunity against SARS-CoV-2, vaccine effectiveness, and duration of the humoral protective response, as well as aiding in the selection of suitable individuals who can donate convalescent plasma to treat infected people. Despite all these clinical applications of NAbs, using them in clinical settings can present some challenges. This review discusses the protective functions, possible protective mechanisms against SARS-CoV-2, and potential clinical applications of NAbs in COVID-19. This article also highlights the possible challenges and solutions associated with COVID-19 antibody-based prophylaxis, therapy, and vaccination.

Antibodies to SARS-CoV-2 are central to recovery and immunity from COVID-19. However, the relationship between disease severity and the repertoire of antibodies against specific SARS-CoV-2 epitopes an individual develops following exposure remains incompletely understood. Here, we studied seroprevalence of antibodies to specific SARS-CoV-2 and other betacoronavirus antigens in a well-annotated, community sample of convalescent and never-infected individuals obtained in August 2020. One hundred and twenty-four participants were classified into five groups: previously exposed but without evidence of infection, having no known exposure or evidence of infection, seroconverted without symptoms, previously diagnosed with symptomatic COVID-19, and recovered after hospitalization with COVID-19. Prevalence of IgGs specific to the following antigens was compared between the five groups: recombinant SARS-CoV-2 and betacoronavirus spike and nucleocapsid protein domains, peptides from a tiled array of 22-mers corresponding to the entire spike and nucleocapsid proteins, and peptides corresponding to predicted immunogenic regions from other proteins of SARS-CoV-2. Antibody abundance generally correlated positively with severity of prior illness. A number of specific immunogenic peptides and some that may be associated with milder illness or protection from symptomatic infection were identified. No convincing association was observed between antibodies to Receptor Binding Domain(s) (RBDs) of less pathogenic betacoronaviruses HKU1 or OC43 and COVID-19 severity. However, apparent cross-reaction with SARS-CoV RBD was evident and some predominantly asymptomatic individuals had antibodies to both MERS-CoV and SARS-CoV RBDs. Findings from this pilot study may inform development of diagnostics, vaccines, and therapeutic antibodies, and provide insight into viral pathogenic mechanisms.

It remains unclear whether high titers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies aggravate clinical manifestations in patients or whether severe clinical manifestations result in high antibody titers. Thus, we investigated the cause-effect relationship between SARS-CoV-2 antibody titers and disease severity.

We prospectively enrolled patients admitted with the diagnosis of coronavirus disease-19 (COVID-19) from February 2020 to August 2020. We measured SARS-CoV-2 antibody titers, namely anti-receptor-binding domain (RBD) antibody and neutralizing antibody (NAb), from blood samples and calculated the chest radiograph (CXR) scores of the patients to evaluate the severity of COVID-19.

Overall, 40 patients with COVID-19 were enrolled. Pneumonia was observed in more than half of the patients (25/40, 60%). SARS-CoV-2 antibody titers were higher in patients who were aged >60 years (anti-RBD antibodies, P = 0.003 and NAb, P = 0.009), presented with pneumonia (P = 0.006 and 0.007, respectively), and required oxygen therapy (P = 0.003 and 0.004, respectively) than in those who were not. CXR scores peaked (at 15-21 days after the onset of symptoms) statistically significantly earlier than SARS-CoV-2 antibody titers (at 22-30 days for NAb and at 31-70 days for anti-RBD antibody). There was a close correlation between the maximum CXR score and the maximum SAR-CoV-2 antibody titer.

Based on the comparison of the peak time of SARS-CoV-2 antibody titers with the CXR score after symptom onset, we suggest that severe clinical manifestations result in high titers of SARS-CoV-2 antibodies.

Due to the recent coronavirus disease 2019 (COVID-19) pandemic and emergent administration of various vaccines worldwide, comprehensive studies on the different aspects of vaccines are in demand. This study evaluated antibody response after the second dose of the COVID-19 vaccine in the Children's Medical Center personnel. The blood samples of 174 healthcare workers were gathered at least 10 days after vaccination. The administered vaccines included Oxford/AstraZeneca, COVAXIN, Sinopharm, and Sputnik V. This study assessed all antibodies employing ELISA methods, including anti-SARS-CoV-2 neutralizing antibody by DiaZist and Pishtazteb kits, anti-SARS-CoV-2-nucleocapsid by Pishtazteb kit, and anti-SARS-CoV-2-Spike by Razi kit. The cutoff for the tests' results was calculated according to the instructions of each kit. Totally, 174 individuals with an average age of 40 ± 9 years participated in this study, the proportion of men was 31%, and the frequency of past COVID-19 infection was 66 (38%). Sixteen (9%) personnel received Oxford/AstraZeneca, 28 (16%) COVAXIN, 29 (17%) Sinopharm, and 101 (58%) Sputnik V. anti-SARS-CoV-2-nucleocapsid and anti-SARS-CoV-2-Spike were positive in 37 (21%), and 163 (94%) participants and their mean level were more in adenoviral-vectored vaccines (p value < 0.0001). Neutralizing antibody was positive in 74% using Pishtazteb kit while 87% using DiaZist kit. All antibodies' levels were significantly higher in those with a past COVID-19 infection (p value < 0.0001). In conclusion, Oxford/AstraZeneca and Sputnik V had a similar outcome of inducing high levels of anti-SARS-Cov-2-spike and neutralizing antibodies, which were more than Sinopharm and COVAXIN. The titers of Anti-SARS-CoV-2-nucleocapsid antibody were low in all of these four vaccines.

Low-volume antibody assays can be used to track SARS-CoV-2 infection rates in settings where active testing for virus is limited and remote sampling is optimal. We developed 12 ELISAs detecting total or antibody isotypes to SARS-CoV-2 nucleocapsid, spike protein or its receptor binding domain (RBD), 3 anti-RBD isotype specific luciferase immunoprecipitation system (LIPS) assays and a novel Spike-RBD bridging LIPS total-antibody assay. We utilized pre-pandemic (n=984) and confirmed/suspected recent COVID-19 sera taken pre-vaccination rollout in 2020 (n=269). Assays measuring total antibody discriminated best between pre-pandemic and COVID-19 sera and were selected for diagnostic evaluation. In the blind evaluation, two of these assays (Spike Pan ELISA and Spike-RBD Bridging LIPS assay) demonstrated >97% specificity and >92% sensitivity for samples from COVID-19 patients taken >21 days post symptom onset or PCR test. These assays offered better sensitivity for the detection of COVID-19 cases than a commercial assay which requires 100-fold larger serum volumes. This study demonstrates that low-volume in-house antibody assays can provide good diagnostic performance, and highlights the importance of using well-characterized samples and controls for all stages of assay development and evaluation. These cost-effective assays may be particularly useful for seroprevalence studies in low and middle-income countries.

The precise interaction between the immune system and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is critical in deciphering the pathogenesis of coronavirus disease 2019 (COVID-19) and is also vital for developing novel therapeutic tools, including monoclonal antibodies, antivirals drugs, and vaccines. Viral infections need innate and adaptive immune reactions since the various immune components, such as neutrophils, macrophages, CD4+ T, CD8+ T, and B lymphocytes, play different roles in various infections. Consequently, the characterization of innate and adaptive immune reactions toward SARS-CoV-2 is crucial for defining the pathogenicity of COVID-19. In this study, we explain what is currently understood concerning the conventional immune reactions to SARS-CoV-2 infection to shed light on the protective and pathogenic role of immune response in this case. Also, in particular, we investigate the in-depth roles of other immune mediators, including neutrophil elastase, serum amyloid A, and syndecan, in the immunopathogenesis of COVID-19.