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In March 2020, the United Kingdom Primary Immunodeficiency Network (UKPIN) established a registry of cases to collate the outcomes of individuals with PID and SID following SARS-CoV-2 infection and treatment. A total of 310 cases of SARS-CoV-2 infection in individuals with PID or SID have now been reported in the UK. The overall mortality within the cohort was 17.7% (n = 55/310). Individuals with CVID demonstrated an infection fatality rate (IFR) of 18.3% (n = 17/93), individuals with PID receiving IgRT had an IFR of 16.3% (n = 26/159) and individuals with SID, an IFR of 27.2% (n = 25/92). Individuals with PID and SID had higher inpatient mortality and died at a younger age than the general population. Increasing age, low pre-SARS-CoV-2 infection lymphocyte count and the presence of common co-morbidities increased the risk of mortality in PID. Access to specific COVID-19 treatments in this cohort was limited: only 22.9% (n = 33/144) of patients admitted to the hospital received dexamethasone, remdesivir, an anti-SARS-CoV-2 antibody-based therapeutic (e.g. REGN-COV2 or convalescent plasma) or tocilizumab as a monotherapy or in combination. Dexamethasone, remdesivir, and anti-SARS-CoV-2 antibody-based therapeutics appeared efficacious in PID and SID. Compared to the general population, individuals with PID or SID are at high risk of mortality following SARS-CoV-2 infection. Increasing age, low baseline lymphocyte count, and the presence of co-morbidities are additional risk factors for poor outcome in this cohort. [ABSTRACT FROM AUTHOR]

Background: Vaccination prevents severe morbidity and mortality from COVID-19 in the general population. The immunogenicity and efficacy of SARS-CoV-2 vaccines in patients with antibody deficiency is poorly understood. Objectives: COVID-19 in patients with antibody deficiency (COV-AD) is a multi-site UK study that aims to determine the immune response to SARS-CoV-2 infection and vaccination in patients with primary or secondary antibody deficiency, a population that suffers from severe and recurrent infection and does not respond well to vaccination. Methods: Individuals on immunoglobulin replacement therapy or with an IgG less than 4 g/L receiving antibiotic prophylaxis were recruited from April 2021. Serological and cellular responses were determined using ELISA, live-virus neutralisation and interferon gamma release assays. SARS-CoV-2 infection and clearance were determined by PCR from serial nasopharyngeal swabs. Results: A total of 5.6% (n = 320) of the cohort reported prior SARS-CoV-2 infection, but only 0.3% remained PCR positive on study entry. Seropositivity, following two doses of SARS-CoV-2 vaccination, was 54.8% (n = 168) compared with 100% of healthy controls (n = 205). The magnitude of the antibody response and its neutralising capacity were both significantly reduced compared to controls. Participants vaccinated with the Pfizer/BioNTech vaccine were more likely to be seropositive (65.7% vs. 48.0%, p = 0.03) and have higher antibody levels compared with the AstraZeneca vaccine (IgGAM ratio 3.73 vs. 2.39, p = 0.0003). T cell responses post vaccination was demonstrable in 46.2% of participants and were associated with better antibody responses but there was no difference between the two vaccines. Eleven vaccine-breakthrough infections have occurred to date, 10 of them in recipients of the AstraZeneca vaccine. Conclusion: SARS-CoV-2 vaccines demonstrate reduced immunogenicity in patients with antibody deficiency with evidence of vaccine breakthrough infection. [ABSTRACT FROM AUTHOR]

B-cell-depleting agents are among the most commonly used drugs to treat haemato-oncological and autoimmune diseases. They rapidly induce a state of peripheral B-cell aplasia with the potential to interfere with nascent vaccine responses, particularly to novel antigens. We have examined the relationship between B-cell reconstitution and SARS-CoV-2 vaccine responses in two cohorts of patients previously exposed to B-cell-depleting agents: a cohort of patients treated for haematological B-cell malignancy and another treated for rheumatological disease. B-cell depletion severely impairs vaccine responsiveness in the first 6 months after administration: SARS-CoV-2 antibody seroprevalence was 42.2% and 33.3% in the haemato-oncological patients and rheumatology patients, respectively and 22.7% in patients vaccinated while actively receiving anti-lymphoma chemotherapy. After the first 6 months, vaccine responsiveness significantly improved during early B-cell reconstitution; however, the kinetics of reconstitution was significantly faster in haemato-oncology patients. The AstraZeneca ChAdOx1 nCoV-19 vaccine and the Pfizer BioNTech 162b vaccine induced equivalent vaccine responses; however, shorter intervals between vaccine doses (<1 m) improved the magnitude of the antibody response in haeamto-oncology patients. In a subgroup of haemato-oncology patients, with historic exposure to B-cell-depleting agents (>36 m previously), vaccine non-responsiveness was independent of peripheral B-cell reconstitution. The findings have important implications for primary vaccination and booster vaccination strategies in individuals clinically vulnerable to SARS-CoV-2. B cell depleting drugs including rituximab are commonly used to treat haematological malignancy and autoimmune diseases but may impair the immunological response to vaccination. This study investigates SARS-CoV-2 vaccine responses in individuals with haematological and rheumatological disease with previously exposure to B cell depleting agents. Vaccination within the first 6 months of B cell depletion is associated with significant impairment of vaccine responsiveness; however, rheumatology and haemato-oncological patients display different kinetics of B cell reconstitution corresponding to differential vaccine responsiveness over time. [ABSTRACT FROM AUTHOR]

Summary: Coronavirus 19 (COVID‐19) has been associated with both transient and persistent systemic symptoms that do not appear to be a direct consequence of viral infection. The generation of autoantibodies has been proposed as a mechanism to explain these symptoms. To understand the prevalence of autoantibodies associated with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection, we investigated the frequency and specificity of clinically relevant autoantibodies in 84 individuals previously infected with SARS‐CoV‐2, suffering from COVID‐19 of varying severity in both the acute and convalescent setting. These were compared with results from 32 individuals who were on the intensive therapy unit (ITU) for non‐COVID reasons. We demonstrate a higher frequency of autoantibodies in the COVID‐19 ITU group compared with non‐COVID‐19 ITU disease control patients and that autoantibodies were also found in the serum 3–5 months post‐COVID‐19 infection. Non‐COVID patients displayed a diverse pattern of autoantibodies; in contrast, the COVID‐19 groups had a more restricted panel of autoantibodies including skin, skeletal muscle and cardiac antibodies. Our results demonstrate that respiratory viral infection with SARS‐CoV‐2 is associated with the detection of a limited profile of tissue‐specific autoantibodies, detectable using routine clinical immunology assays. Further studies are required to determine whether these autoantibodies are specific to SARS‐CoV‐2 or a phenomenon arising from severe viral infections and to determine the clinical significance of these autoantibodies. [ABSTRACT FROM AUTHOR]

There are limited treatments for severe COVID-19; of the empirical treatments used in this study (dexamethasone, remdesivir, convalescent plasma), the only dexamethasone is associated with reduced 28-day mortality in the general population [[3]-[5]]. Herein, we highlight our experience of using remdesivir and convalescent plasma to treat persistent symptomatic COVID-19 in a patient with secondary immunodeficiency following long-term rituximab treatment. To the Editor, We read with interest the report from London et al. regarding the efficacy of convalescent plasma in the treatment of severe COVID-19 in two patients with primary immunodeficiencies [[1]]. The efficacy of convalescent plasma in the treatment of COVID-19 in patients has been reported in small case series of individuals with both congenital and acquired B cell aplasia [[7]-[9]]. [Extracted from the article]

Germline gain-of-function mutations in CARD11 lead to the primary immunodeficiency, B cell expansion with NF-κB, and T cell anergy (BENTA). Herein, we report the case of a girl, presenting at 2 years of age with lymphocytosis and splenomegaly in whom a novel, in-frame, three base pair deletion in CARD11 was identified resulting in the deletion of a single lysine residue (K215del) from the coiled-coil domain. In vitro functional assays demonstrated that this variant leads to a subtle increase in baseline NF-κB signaling and impaired proliferative responses following T cell receptor and mitogenic stimulation. Previously reported immunological defects associated with BENTA appear mild in our patient who is now 6 years of age; a B cell lymphocytosis and susceptibility to upper respiratory tract infections persist; however, she has broad, sustained responses to protein-polysaccharide conjugate vaccines and displays normal proliferative responses to ex vivo T cell stimulation. [ABSTRACT FROM AUTHOR]

• Patients commencing clozapine divide into different groups based on neutrophil counts. • Early neutrophil trajectory when starting clozapine appears to predict clozapine response. • Neutrophils are increasingly recognised to play key roles in the immune response. • Clozapine's unique efficacy in TRS may be due to its immune effects. • Neutrophils may be an easily accessible biomarker for treatment response. Clozapine has unique effectiveness in treatment-resistant schizophrenia and is known to cause immunological side-effects. A transient spike in neutrophils commonly occurs in the first weeks of clozapine therapy. There is contradictory evidence in the literature as to whether neutrophil changes with clozapine are linked to treatment response. The current study aims to further examine the neutrophil changes in response to clozapine and explore any association between neutrophil trajectory and treatment response. A retrospective cohort study of patients undergoing their first treatment with clozapine and continuing for at least 2 years identified 425 patients (69% male/31% female). Neutrophil counts at baseline, 3 weeks and 1 month were obtained predominantly by linkage with data from the clozapine monitoring service. Clinical Global Impression- Severity (CGI-S) was rated from case notes at the time of clozapine initiation and at 2 years. Latent class growth analysis (LCGA) was performed to define distinct trajectories of neutrophil changes during the first month of treatment. Logistic regression was then conducted to investigate for association between the trajectory of neutrophil count changes in month 1 and clinical response at 2 years as well as between baseline neutrophil count and response. Of the original cohort, 397 (93%) patients had useable neutrophil data during the first 6 weeks of clozapine treatment. LCGA revealed significant differences in neutrophil trajectories with a three-class model being the most parsimonious. The classes had similar trajectory profiles but differed primarily on overall neutrophil count: with low, high-normal and high neutrophil classes, comprising 52%, 40% and 8% of the sample respectively. Membership of the high-normal group was associated with significantly increased odds of a positive response to clozapine, as compared to the low neutrophil group [Odds ratio (OR) = 2.10, p-value = 0.002; 95% confidence interval (95% CI) = 1.31–3.36]. Baseline neutrophil count was a predictor of response to clozapine at 2 years, with counts of ≥5 × 109/l significantly associated with positive response (OR = 1.60, p-value = 0.03; 95% CI = 1.03–2.49). Our data are consistent with the hypothesis that patients with low-level inflammation, reflected in a high-normal neutrophil count, are more likely to respond to clozapine, raising the possibility that clozapine exerts its superior efficacy via immune mechanisms. [ABSTRACT FROM AUTHOR]

The gold standard treatment for Dupuytren's contracture is surgical excision of the cord. A non-surgical treatment with collagenase clostridium histolyticum injection is available but appears costly. Objectives: To provide data on resource consumption related to surgical and non-surgical treatment for Dupuytren's contracture. Design and Participants: Twenty patients with a single digit Dupuytren's contracture, 10 treated with surgical excision, and 10 treated with a single injection of collagenase. Measurements: Minutes spent in theatre, number of follow-up appointments, time to skin healing, and patients return to normal activities of daily living. Results: The injection group was significantly better regarding theatre time (p < 0.0001), follow-up appointments (p = 0.048), skin healing time (p < 0.001), and return to normal activities of daily living (p = 0.02) than the operated group. Conclusions: There are significant personal and health economic differences between the two methods of treatment which may influence local choice. [ABSTRACT FROM AUTHOR]

Appropriate regulation and subsequent resolution of acute inflammatory events is critical to the prevention of autoinflammatory diseases. Indeed, the chronic inflammation observed in diseases such as RA is at least partially consequent on the failure of endogenous immunoregulation. Current RA therapies (e.g. anti-TNF-α inhibitors and MTX) inhibit components of the inflammatory disease process without directly promoting the resolution of inflammation. We propose that the next generation of RA therapeutics will complement and augment endogenous immunoregulatory and pro-resolution immunological networks, thus promoting the definitive resolution of inflammation rather than temporary immunological control. Of particular interest with respect to this therapeutic approach is binding immunoglobulin protein [BiP; also known as glucose-regulated protein-78 (GRP78)], a member of the recently defined resolution-associated molecular pattern (RAMP) family of molecules. In this review, we consider the preclinical evidence from experiments in mouse and man that suggests BiP and other members of the RAMP family have the potential to herald a new generation of immunotherapeutics. [ABSTRACT FROM PUBLISHER]

A Correction to this paper has been published: https://doi.org/10.1007/s10875-021-01029-z [ABSTRACT FROM AUTHOR]

• Prospective evidence of a reduction in immunoglobulin levels during clozapine treatment. • Reduction in immunoglobulin levels observed over the first six months of treatment. • Reductions in immunoglobulin levels correlated with reduction in schizophrenia symptom severity. Use of clozapine in treatment-resistant schizophrenia is often limited due to risk of adverse effects. Cross-sectional associations between clozapine treatment and low immunoglobulin levels have been reported, however prospective studies are required to establish temporal relationships. We tested the hypothesis that reductions in immunoglobulin levels would occur over the first 6 months following initiation of clozapine treatment. Relationships between immunoglobulin levels and symptom severity over the course of clozapine treatment were also explored. This prospective observational study measured immunoglobulin (Ig) levels (A, M and G) in 56 patients with treatment-resistant schizophrenia at 6-, 12- and 24-weeks following initiation with clozapine. Clinical symptoms were also measured at 12 weeks using the positive and negative syndrome scale (PANSS). IgA, IgG and IgM all decreased during clozapine treatment. For IgA and IgG the reduction was significant at 24 weeks (IgA: β = –32.66, 95% CI = -62.38, −2.93, p = 0.03; IgG: β = -63.96, 95% CI = -118.00, −9.31, p = 0.02). For IgM the reduction was significant at 12 and 24 weeks (12 weeks: β = –23.48, 95% CI = -39.56, −7.42, p = 0.004; 24 weeks: β = –33.12, 95 %CI = -50.30, −15.94, p = <0.001). Reductions in IgA and IgG during clozapine treatment were correlated with reductions in PANSS-total over 12 weeks (n = 32, IgA r = 0.59, p = 0.005; IgG r = 0.48, p = 0.03). The observed reductions in immunoglobulin levels over six months of clozapine treatment add further evidence linking clozapine to secondary antibody deficiency. Associations between Ig reduction and symptom improvement may however indicate that immune mechanisms contribute to both desirable and undesirable effects of clozapine. [ABSTRACT FROM AUTHOR]

Background: The measurement of monoclonal free light chains is being increasingly utilized since the introduction of serum-based assays. It is important for laboratories to determine their own reference ranges in order to reflect the local population. The aim of this study was to determine if age-adjusted reference ranges for serum free light chains would have implications for demand management of further laboratory investigations including immunofixation. Methods: After certain exclusions, 4293 samples from individuals seen in primary care across Oxfordshire between 2014 and 2016 were identified for analysis of patient characteristics, serum free light chain results and estimated glomerular filtration rate. Results: We found age to be an independent variable when considering serum free light chain concentrations, ratio and estimated glomerular filtration rate. The reference ranges derived from our data differ markedly from the original Binding Site ranges. When the age-specific ranges are retrospectively applied to our population, there is a 38% decrease in follow-up testing with no loss of specificity. Conclusion: We feel confident implementing new age-specific serum free light chain reference ranges in our laboratory. We have developed a simple algorithm for evaluating serum free light chains based on age and estimated glomerular filtration rate. We encourage laboratories to establish their own local reference ranges using large cohorts and their chosen serum free light chain assay platform. [ABSTRACT FROM AUTHOR]

.83 ht 1 Abbreviations: IgG, immunoglobulin G; IgRT, immunoglobulin replacement therapy; IQR, interquartile range. We demonstrate that, in previously stable patients, IgRT dose reductions lead to a reduction in trough IgG, which is associated with an increased frequency of infections requiring outpatient antibiotic use. [Extracted from the article]

Post-acute cardiac sequelae, following SARS-CoV-2 infection, are well recognized as complications of COVID-19. We have previously shown the persistence of autoantibodies against antigens in skin, muscle, and heart in individuals following severe COVID-19; the most common staining on skin tissue displayed an inter-cellular cement pattern consistent with antibodies against desmosomal proteins. Desmosomes play a critical role in maintaining the structural integrity of tissues. For this reason, we analyzed desmosomal protein levels and the presence of anti-desmoglein (DSG) 1, 2, and 3 antibodies in acute and convalescent sera from patients with COVID-19 of differing clinical severity. We find increased levels of DSG2 protein in sera from acute COVID-19 patients. Furthermore, we find that DSG2 autoantibody levels are increased significantly in convalescent sera following severe COVID-19 but not in hospitalized patients recovering from influenza infection or healthy controls. Levels of autoantibody in sera from patients with severe COVID-19 were comparable to levels in patients with non-COVID-19-associated cardiac disease, potentially identifying DSG2 autoantibodies as a novel biomarker for cardiac damage. To determine if there was any association between severe COVID-19 and DSG2, we stained post-mortem cardiac tissue from patients who died from COVID-19 infection. This confirmed DSG2 protein within the intercalated discs and disruption of the intercalated disc between cardiomyocytes in patients who died from COVID-19. Our results reveal the potential for DSG2 protein and autoimmunity to DSG2 to contribute to unexpected pathologies associated with COVID-19 infection. We find raised levels of anti-DSG2 autoantibodies in sera from individuals following severe COVID-19. Staining of post-mortem cardiac tissue from individuals that died from COVID-19 with an anti-DSG2 antibody revealed disruption of the intercalated disc between cardiomyocytes that was consistent with separation of the DSG2 protein homodimer. Our results reveal the potential for DSG2 protein and autoimmunity to DSG2 to contribute to unexpected pathologies associated with COVID-19 infection. [ABSTRACT FROM AUTHOR]

In this population-based cohort of 7538 adults, combined immunoglobulin (Ig) G, IgA, and IgM (IgG/A/M) anti-spike titers measured after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination were predictive of protection against breakthrough SARS-CoV-2 infection. Discrimination was significantly improved by adjustment for factors influencing risk of SARS-CoV-2 exposure, including household overcrowding, public transport use, and visits to indoor public places. Anti-spike IgG/A/M titers showed positive correlation with neutralizing antibody titers (rs = 0.80 [95% confidence interval, .72-.86]; P < .001) and S peptide-stimulated interferon-γ concentrations (rs = 0.31 [.13-.47]; P < .001). [ABSTRACT FROM AUTHOR]

UBE2L3 is associated with increased susceptibility to numerous autoimmune diseases, but the underlying mechanism is unexplained. By using data from a genome-wide association study of systemic lupus erythematosus (SLE), we observed a single risk haplotype spanning UBE2L3 , consistently aligned across multiple autoimmune diseases, associated with increased UBE2L3 expression in B cells and monocytes. rs140490 in the UBE2L3 promoter region showed the strongest association. UBE2L3 is an E2 ubiquitin-conjugating enzyme, specially adapted to function with HECT and RING-in-between-RING (RBR) E3 ligases, including HOIL-1 and HOIP, components of the linear ubiquitin chain assembly complex (LUBAC). Our data demonstrate that UBE2L3 is the preferred E2 conjugating enzyme for LUBAC in vivo, and UBE2L3 is essential for LUBAC-mediated activation of NF-κB. By accurately quantifying NF-κB translocation in primary human cells from healthy individuals stratified by rs140490 genotype, we observed that the autoimmune disease risk UBE2L3 genotype was correlated with basal NF-κB activation in unstimulated B cells and monocytes and regulated the sensitivity of NF-κB to CD40 stimulation in B cells and TNF stimulation in monocytes. The UBE2L3 risk allele correlated with increased circulating plasmablast and plasma cell numbers in SLE individuals, consistent with substantially elevated UBE2L3 protein levels in plasmablasts and plasma cells. These results identify key immunological consequences of the UBE2L3 autoimmune risk haplotype and highlight an important role for UBE2L3 in plasmablast and plasma cell development. [ABSTRACT FROM AUTHOR]

Detecting antibody responses during and after SARS‐CoV‐2 infection is essential in determining the seroepidemiology of the virus and the potential role of antibody in disease. Scalable, sensitive and specific serological assays are essential to this process. The detection of antibody in hospitalized patients with severe disease has proven relatively straightforward; detecting responses in subjects with mild disease and asymptomatic infections has proven less reliable. We hypothesized that the suboptimal sensitivity of antibody assays and the compartmentalization of the antibody response may contribute to this effect. We systematically developed an ELISA, optimizing different antigens and amplification steps, in serum and saliva from non‐hospitalized SARS‐CoV‐2‐infected subjects. Using trimeric spike glycoprotein, rather than nucleocapsid, enabled detection of responses in individuals with low antibody responses. IgG1 and IgG3 predominate to both antigens, but more anti‐spike IgG1 than IgG3 was detectable. All antigens were effective for detecting responses in hospitalized patients. Anti‐spike IgG, IgA and IgM antibody responses were readily detectable in saliva from a minority of RT‐PCR confirmed, non‐hospitalized symptomatic individuals, and these were mostly subjects who had the highest levels of anti‐spike serum antibodies. Therefore, detecting antibody responses in both saliva and serum can contribute to determining virus exposure and understanding immune responses after SARS‐CoV‐2 infection. [ABSTRACT FROM AUTHOR]

Although anti-S IgA and IgG were more similar in children and adult COVID-19 patients, anti-N IgA and IgG antibodies were higher in ITU patients (Figure 1C,D). Since antibody isotypes can reflect recent infection (IgM), or more historic infections (IgG and IgA), we examined individual antibody isotypes and presented these results as area under the curve (AUC). Therefore, children with Kawasaki-like inflammatory syndrome, negative by PCR, can have IgG1, IgG3, and IgA antibody levels to SARS-CoV-2 in the absence of maintained IgM responses. Screening of sera, diluted 1:40, to detect IgG, IgA, and IgM demonstrated that all children had antibodies against the SARS-CoV-2 S glycoprotein (Figure 1A). [Extracted from the article]

Background: Understanding the T cell response to SARS-CoV-2 is critical to vaccine development, epidemiological surveillance and disease control strategies. This systematic review critically evaluates and synthesises the relevant peer-reviewed and pre-print literature published from 01/01/2020-26/06/2020. Methods: For this systematic review, keyword-structured literature searches were carried out in MEDLINE, Embase and COVID-19 Primer. Papers were independently screened by two researchers, with arbitration of disagreements by a third researcher. Data were independently extracted into a pre-designed Excel template and studies critically appraised using a modified version of the MetaQAT tool, with resolution of disagreements by consensus. Findings were narratively synthesised. Results: 61 articles were included. 55 (90%) studies used observational designs, 50 (82%) involved hospitalised patients with higher acuity illness, and the majority had important limitations. Symptomatic adult COVID-19 cases consistently show peripheral T cell lymphopenia, which positively correlates with increased disease severity, duration of RNA positivity, and non-survival; while asymptomatic and paediatric cases display preserved counts. People with severe or critical disease generally develop more robust, virus-specific T cell responses. T cell memory and effector function has been demonstrated against multiple viral epitopes, and, cross-reactive T cell responses have been demonstrated in unexposed and uninfected adults, but the significance for protection and susceptibility, respectively, remains unclear. Conclusion: A complex pattern of T cell response to SARS-CoV-2 infection has been demonstrated, but inferences regarding population level immunity are hampered by significant methodological limitations and heterogeneity between studies, as well as a striking lack of research in asymptomatic or pauci-symptomatic individuals. In contrast to antibody responses, population-level surveillance of the T cell response is unlikely to be feasible in the near term. Focused evaluation in specific sub-groups, including vaccine recipients, should be prioritised. [ABSTRACT FROM AUTHOR]

Background: Progress in characterising the humoral immune response to Severe Acute Respiratory Syndrome 2 (SARS-CoV-2) has been rapid but areas of uncertainty persist. Assessment of the full range of evidence generated to date to understand the characteristics of the antibody response, its dynamics over time, its determinants and the immunity it confers will have a range of clinical and policy implications for this novel pathogen. This review comprehensively evaluated evidence describing the antibody response to SARS-CoV-2 published from 01/01/2020-26/06/2020. Methods: Systematic review. Keyword-structured searches were carried out in MEDLINE, Embase and COVID-19 Primer. Articles were independently screened on title, abstract and full text by two researchers, with arbitration of disagreements. Data were double-extracted into a pre-designed template, and studies critically appraised using a modified version of the Public Health Ontario Meta-tool for Quality Appraisal of Public Health Evidence (MetaQAT) tool, with resolution of disagreements by consensus. Findings were narratively synthesised. Results: 150 papers were included. Most studies (113 or 75%) were observational in design, were based wholly or primarily on data from hospitalised patients (108, 72%) and had important methodological limitations. Few considered mild or asymptomatic infection. Antibody dynamics were well described in the acute phase, up to around three months from disease onset, but the picture regarding correlates of the antibody response was inconsistent. IgM was consistently detected before IgG in included studies, peaking at weeks two to five and declining over a further three to five weeks post-symptom onset depending on the patient group; IgG peaked around weeks three to seven post-symptom onset then plateaued, generally persisting for at least eight weeks. Neutralising antibodies were detectable within seven to 15 days following disease onset, with levels increasing until days 14–22 before levelling and then decreasing, but titres were lower in those with asymptomatic or clinically mild disease. Specific and potent neutralising antibodies have been isolated from convalescent plasma. Cross-reactivity but limited cross-neutralisation with other human coronaviridae was reported. Evidence for protective immunity in vivo was limited to small, short-term animal studies, showing promising initial results in the immediate recovery phase. Conclusions: Literature on antibody responses to SARS-CoV-2 is of variable quality with considerable heterogeneity of methods, study participants, outcomes measured and assays used. Although acute phase antibody dynamics are well described, longer-term patterns are much less well evidenced. Comprehensive assessment of the role of demographic characteristics and disease severity on antibody responses is needed. Initial findings of low neutralising antibody titres and possible waning of titres over time may have implications for sero-surveillance and disease control policy, although further evidence is needed. The detection of potent neutralising antibodies in convalescent plasma is important in the context of development of therapeutics and vaccines. Due to limitations with the existing evidence base, large, cross-national cohort studies using appropriate statistical analysis and standardised serological assays and clinical classifications should be prioritised. [ABSTRACT FROM AUTHOR]

Dried blood spot (DBS) samples can be used for the detection of severe acute respiratory syndrome coronavirus 2 spike antibodies. DBS sampling is comparable to matched serum samples with a relative 98.1% sensitivity and 100% specificity. Thus, DBS sampling offers an alternative for population-wide serologic testing in the coronavirus pandemic. [ABSTRACT FROM AUTHOR]