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Objectives Specific serological tests are mandatory for reliable SARS‐CoV‐2 diagnostics and seroprevalence studies. Here, we assess the specificities of four commercially available SARS‐CoV‐2 IgG ELISAs in serum/plasma panels originating from Africa, South America, and Europe. Methods 882 serum/plasma samples collected from symptom‐free donors before the COVID‐19 pandemic in three African countries (Ghana, Madagascar, Nigeria), Colombia, and Germany were analysed with three nucleocapsid‐based ELISAs (Euroimmun Anti‐SARS‐CoV‐2‐NCP IgG, EDITM Novel Coronavirus COVID‐19 IgG, Mikrogen recomWell SARS‐CoV‐2 IgG), one spike/S1‐based ELISA (Euroimmun Anti‐SARS‐CoV‐2 IgG), and in‐house common cold CoV ELISAs. Results High specificity was confirmed for all SARS‐CoV‐2 IgG ELISAs for Madagascan (93.4%‐99.4%), Colombian (97.8%‐100.0%), and German (95.9%‐100.0%) samples. In contrast, specificity was much lower for the Ghanaian and Nigerian serum panels (Ghana: NCP‐based assays 77.7%‐89.7%, spike/S1‐based assay 94.3%; Nigeria: NCP‐based assays 39.3%‐82.7%, spike/S1‐based assay 90.7%). 15 of 600 African sera were concordantly classified as positive in both the NCP‐based and the spike/S1‐based Euroimmun ELISA, but did not inhibit spike/ACE2 binding in a surrogate virus neutralization test. IgG antibodies elicited by previous infections with common cold CoVs were found in all sample panels, including those from Madagascar, Colombia, and Germany and thus do not inevitably hamper assay specificity. Nevertheless, high levels of IgG antibodies interacting with OC43 NCP were found in all 15 SARS‐CoV‐2 NCP/spike/S1 ELISA positive sera. Conclusions Depending on the chosen antigen and assay protocol, SARS‐CoV‐2 IgG ELISA specificity may be significantly reduced in certain populations probably due to interference of immune responses to endemic pathogens like other viruses or parasites.

BACKGROUND The cellular surface molecule HsTOSO/FAIM3/HsFcμR has been identified as an IgM-specific Fc receptor expressed on lymphocytes. Here, we show that its extracellular immunoglobulin-like domain (HsFcμR-Igl) specifically binds to IgM/antigen immune complexes (ICs) and exploit this property for the development of novel detection systems for IgM antibodies directed against Crimean-Congo hemorrhagic fever virus (CCHFV) and Zika virus (ZIKV). METHODS His-tagged HsFcμR-Igl was expressed in Escherichia coli and purified by affinity chromatography, oxidative refolding, and size-exclusion chromatography. Specific binding of HsFcμR-Igl to IgM/antigen ICs was confirmed, and 2 prototypic ELISAs for the detection of anti-CCHFV and anti-ZIKV IgM antibodies were developed. Thereby, patient sera and virus-specific recombinant antigens directly labeled with horseradish peroxidase (HRP) were coincubated on HsFcμR-Igl-coated ELISA plates. Bound ICs were quantified by measuring turnover of a chromogenic HRP substrate. RESULTS Assay validation was performed using paired serum samples from 15 Kosovar patients with a PCR-confirmed CCHFV infection and 28 Brazilian patients with a PCR-confirmed ZIKV infection, along with a panel of a priori CCHFV/ZIKV-IgM-negative serum samples. Both ELISAs were highly reproducible. Sensitivity and specificity were comparable with or even exceeded in-house gold standard testing and commercial kits. Furthermore, latex beads coated with HsFcμR-Igl aggregated upon coincubation with an IgM-positive serum and HRP-labeled antigen but not with either component alone, revealing a potential for use of HsFcμR-Igl as a capture molecule in aggregation-based rapid tests. CONCLUSIONS Recombinant HsFcμR-Igl is a versatile capture molecule for IgM/antigen ICs of human and animal origin and can be applied for the development of both plate- and bead-based serological tests.

In a recent report, the cellular receptor CD55 was identified as a molecule essential for the invasion of human erythrocytes by Plasmodium falciparum, the causal agent of the most severe form of malaria. As this invasion process represents a critical step during infection with the parasite, it was hypothesized that genetic variants in the gene could affect severe malaria (SM) susceptibility. We performed high-resolution variant discovery of rare and common genetic variants in the human CD55 gene. Association testing of these variants in over 1700 SM cases and unaffected control individuals from the malaria-endemic Ashanti Region in Ghana, West Africa, were performed on the basis of single variants, combined rare variant analyses, and reconstructed haplotypes. A total of 26 genetic variants were detected in coding and regulatory regions of CD55. Five variants were previously unknown. None of the single variants, rare variants, or haplotypes showed evidence for association with SM or P. falciparum density. Here, we present the first comprehensive analysis of variation in the CD55 gene in the context of SM and show that genetic variants present in a Ghanaian study group appear not to influence susceptibility to the disease.

The cellular surface moleculeHis-taggedAssay validation was performed using paired serum samples from 15 Kosovar patients with a PCR-confirmed CCHFV infection and 28 Brazilian patients with a PCR-confirmed ZIKV infection, along with a panel of a priori CCHFV/ZIKV-IgM-negative serum samples. Both ELISAs were highly reproducible. Sensitivity and specificity were comparable with or even exceeded in-house gold standard testing and commercial kits. Furthermore, latex beads coated withRecombinant

Sickle cell disease is among hereditary diseases with evidence that early diagnoses and treatment improves the clinical outcome. So far sickle cell disease has not been included in the German newborn screening program despite immigration from countries with populations at risk. To determine the birth prevalence we tested 17,018 newborns. High pressure liquid chromatography and subsequent molecular-genetic testing were used for the detection and confirmation of hemoglobin variants. The frequency of sickle cell disease-consistent genotypes was one in 2,385 newborns. Duffy-blood group typing showed evidence that affected children were likely of Sub-Saharan ancestry. An inclusion of sickle cell disease into the German newborn screening seems reasonable.

BACKGROUND Salmonella ranks among the leading causes of bloodstream infections in sub-Saharan Africa. Multidrug resistant typhoidal and nontyphoidal Salmonella (NTS) isolates have been previously identified in this region. However, resistance to ciprofloxacin has rarely been reported in West Africa. This study aims to assess susceptibility against ciprofloxacin in Salmonella causing invasive bloodstream infections among children in rural Ghana. METHODS From May 2007 until May 2012, children attending a rural district hospital in central Ghana were eligible for recruitment. Salmonella enterica isolated from blood cultures were assessed for ciprofloxacin susceptibility by Etest (susceptible minimum inhibitory concentration [MIC] ≤ 0.06 µg/mL). The gyrA, gyrB, parC, and parE genes were sequenced to identify mutations associated with changes in susceptibility to fluoroquinolones. RESULTS Two hundred eighty-five Salmonella enterica isolates from 5211 blood cultures were most commonly identified as Salmonella enterica serovar Typhimurium (n = 129 [45%]), Salmonella enterica serovar Typhi (n = 89 [31%]), Salmonella enterica serovar Dublin (n = 20 [7%]), and Salmonella enterica serovar Enteritidis (n = 19 [7%]). All S. Typhi and S. Dublin were susceptible to ciprofloxacin. Reduced susceptibility (MIC >0.06 µg/mL) was found in 53% (10/19) of S. Enteritidis and in 2% (3/129) of S. Typhimurium isolates. Sequencing detected a single gyrB mutation (Glu466Asp) and a single gyrA mutation (Ser83Tyr) in all 3 S. Typhimurium isolates, while 9 of 10 S. Enteritidis harbored single gyrA mutations (Asp87Gly, Asp87Asn, or Asp87Tyr). No mutations were found in the parC and parE genes. CONCLUSIONS Ciprofloxacin susceptibility in invasive NTS in rural Ghana is highly dependent on serotype. Although reduced ciprofloxacin susceptibility is low in S. Typhimurium, more than half of all S. Enteritidis isolates are affected. Healthcare practitioners in Ghana should be aware of potential treatment failure in patients with invasive S. Enteritidis infections.

Toll like receptors (TLR) are key elements of the innate immune response and involved in the recognition of pathogens. To test common and rare TLR variants involved in susceptibility or resistance to infection with Mycobacterium tuberculosis we screened the exons of the genes encoding TLR 1, 2, 4, and the adaptor molecule TIRAP in more than 4500 tuberculosis (TB) cases and controls from Ghana. The analysis yielded 109 variants with possible functional impact, including 101 non-synonymous variants, three stop-variants, and five indels. Association analyses yielded a significant result for the TLR1 variant rs3923647, conferring strong protection against TB (Odds ratio [OR] 0.21, CI confidence interval [CI] 0.05–0.6, Pnominal 1 x 10−3) when applying a recessive model of inheritance. Replication analyses with an additional 3370 Ghanaian cases and control samples, and with data from a recent TB study of 533 African-Americans confirmed the protective effect and resulted in a combined OR of 0.19, with a nominal P value of 2.2 x 10−5, and a corrected P value of 4.1 x 10−4. The SNP is located near the binding pocket of TLR1 and causes an amino acid exchange from histidine to leucine at position 305. The observed effect may, therefore, be attributable to structural changes in the recognition site of the TLR1 molecule, allowing to bind those mycobacterial ligands which preferentially may induce a protective immune response. This is supported by the analysis of BCG-stimulated peripheral blood mononuclear cells, showing increased induction of the proinflammatory cytokine IFN-γ in carriers of the mutant TLR1 rs3923647 TT genotype, compared to the IFN-γ levels of individuals with the AT and AA genotypes.

A genome-wide association study in Ghana, West Africa, to identify genetic variants associated with malaria pathogenesis reveals two previously unknown loci on chromosomes 1 and 16. This genome-wide association study in 2,645 cases and 3,050 controls from Ghana in West Africa identifies genetic variants that might affect any one of the many steps in malaria pathogenesis. Two novel loci are described. The first is on chromosome 1, in the vicinity of the ATP2B4 gene, which encodes the main calcium pump of erythrocytes, the host cells of the pathogenic stage of the malaria parasite. The second is on chromosome 16, close to MARVELD3, which encodes a tight-junction protein that is expressed on endothelial cells. These genetic variants may confer resistance by affecting key steps in disease development that could generate possible antimalarial targets. Malaria causes approximately one million fatalities per year, mostly among African children1. Although highlighted by the strong protective effect of the sickle-cell trait2,3, the full impact of human genetics on resistance to the disease remains largely unexplored4. Genome-wide association (GWA) studies are designed to unravel relevant genetic variants comprehensively; however, in malaria, as in other infectious diseases, these studies have been only partly successful5. Here we identify two previously unknown loci associated with severe falciparum malaria in patients and controls from Ghana, West Africa. We applied the GWA approach to the diverse clinical syndromes of severe falciparum malaria, thereby targeting human genetic variants influencing any step in the complex pathogenesis of the disease. One of the loci was identified on chromosome 1q32 within the ATP2B4 gene, which encodes the main calcium pump of erythrocytes6, the host cells of the pathogenic stage of malaria parasites. The second was indicated by an intergenic single nucleotide polymorphism on chromosome 16q22.2, possibly linked to a neighbouring gene encoding the tight-junction protein MARVELD3. The protein is expressed on endothelial cells7 and might therefore have a role in microvascular damage caused by endothelial adherence of parasitized erythrocytes. We also confirmed previous reports on protective effects of the sickle-cell trait and blood group O5,8,9. Our findings underline the potential of the GWA approach to provide candidates for the development of control measures against infectious diseases in humans.

Sickle cell disease is among hereditary diseases with evidence that early diagnoses and treatment improves the clinical outcome. So far sickle cell disease has not been included in the German newborn screening program despite immigration from countries with populations at risk. To determine the birth prevalence we tested 17,018 newborns. High pressure liquid chromatography and subsequent molecular-genetic testing were used for the detection and confirmation of hemoglobin variants. The frequency of sickle cell disease-consistent genotypes was one in 2,385 newborns. Duffy-blood group typing showed evidence that affected children were likely of Sub-Saharan ancestry. An inclusion of sickle cell disease into the German newborn screening seems reasonable.

After imputation of data from the 1000 Genomes Project into a genome-wide dataset of Ghanaian individuals with tuberculosis and controls, we identified a resistance locus on chromosome 11p13 downstream of the WT1 gene (encoding Wilms tumor 1). The strongest signal was obtained at the rs2057178 SNP (P = 2.63 × 10 -9). Replication in Gambian, Indonesian and Russian tuberculosis case-control study cohorts increased the significance level for the association with this SNP to P = 2.57 × 10 -11. © 2012 Nature America, Inc. All rights reserved.

Using segregation analyses, control of malaria parasites has previously been linked to a major gene within the chromosomal region 5q31-33, but also to complex genetic factors in which effects are under substantial age-dependent influence. However, the responsible gene variants have not yet been identified for this chromosomal region. In order to perform association analyses of 5q31-33 locus candidate single nucleotide polymorphisms (SNPs), 1015 children were recruited at the age of 3 months and followed monthly until the age of 2 years in an area holoendemic for Plasmodium falciparum malaria in Ghana. Quantitative (incidence rates of malaria episodes) and qualitative phenotypes (i.e. 'more than one malaria episode' or 'not more than one malaria episode') were used in population- and family-based analyses. The strongest signal was observed for the interleukin 3 gene (IL3) SNP rs40401 (P = 3.4 × 10(-7), P(c)= 1.4 × 10(-4)). The IL3 genotypes rs40401(CT) and rs40401(TT) were found to exert a protective effect of 25% [incidence rate ratio (IRR) 0.75, P = 4.1 × 10(-5)] and 33% (IRR 0.67, P = 3.2 × 10(-8)), respectively, against malaria attacks. The association was confirmed in transmission disequilibrium tests (TDT, qTDT). The results could argue for a role of IL3 in the pathophysiology of falciparum malaria.

Human genetics and immune responses are considered to critically influence the outcome of malaria infections including life-threatening syndromes caused by Plasmodium falciparum. An important role in immune regulation is assigned to the apoptosis-signaling cell surface receptor CD95 (Fas, APO-1), encoded by the gene FAS. Here, a candidate-gene association study including variant discovery at the FAS gene locus was carried out in a case-control group comprising 1,195 pediatric cases of severe falciparum malaria and 769 unaffected controls from a region highly endemic for malaria in Ghana, West Africa. We found the A allele of c.−436C>A (rs9658676) located in the promoter region of FAS to be significantly associated with protection from severe childhood malaria (odds ratio 0.71, 95% confidence interval 0.58–0.88, pempirical = 0.02) and confirmed this finding in a replication group of 1,412 additional severe malaria cases and 2,659 community controls from the same geographic area. The combined analysis resulted in an odds ratio of 0.71 (95% confidence interval 0.62–0.80, p = 1.8×10−7, n = 6035). The association applied to c.−436AA homozygotes (odds ratio 0.47, 95% confidence interval 0.36–0.60) and to a lesser extent to c.−436AC heterozygotes (odds ratio 0.73, 95% confidence interval 0.63–0.84), and also to all phenotypic subgroups studied, including severe malaria anemia, cerebral malaria, and other malaria complications. Quantitative FACS analyses assessing CD95 surface expression of peripheral blood mononuclear cells of naïve donors showed a significantly higher proportion of CD69+CD95+ cells among persons homozygous for the protective A allele compared to AC heterozygotes and CC homozygotes, indicating a functional role of the associated CD95 variant, possibly in supporting lymphocyte apoptosis., Author Summary Severe malaria caused by infection with the protozoan parasite Plasmodium falciparum is a major health burden, causing approximately one million fatalities annually, predominantly among young children in Sub-Saharan Africa. The occurrence of severe malaria may depend on a complex interplay of transmission dynamics and the development of a protective immune response but also on heritable differences in the susceptibility to the disease. In two large studies including a total of 2,607 affected children and 3,428 apparently healthy individuals from Ghana, West Africa, we investigated genetic variants of the FAS gene, which encodes CD95, a molecule critically involved in the programmed cell death of lymphocytes. We found that a single nucleotide variant in the FAS promoter was associated with a 29%–reduced risk of developing severe malaria. In individuals carrying two copies of the protective allele, a higher proportion of activated lymphocytes was found to express CD95. These findings indicate that a predisposition to an increased expression of CD95 may help to protect from severe malaria, possibly by rendering activated T-lymphocytes more susceptible to programmed cell death.

The high prevalence of hemoglobin S (HbS) in Africa and hemoglobin C (HbC) in parts of West Africa is caused by the strong protection against severe falciparum malaria during childhood. Much less is known about the effect of HbS and especially HbC on Plasmodium falciparum infection, uncomplicated malaria, and anemia. A total of 1070 children from the Ashanti Region, Ghana, were enrolled at the age of 3 months and visited monthly until 2 years of age. The effects of the β-globin genotype on the age-dependent incidence of malaria, levels of parasitemia, and hemoglobin as well as physical development were analyzed by population-averaged models. Infants with HbAS were protected from uncomplicated malaria (P < .005) and anemia (P < .001), had lower age-adjusted parasite densities (P < .001), and higher age-adjusted hemoglobin levels compared with children with the HbAA genotype (P = .004). In contrast, HbAC carriers had lower hemoglobin levels (P < .033) and were not protected against malaria or anemia. Notably, infants with HbAS were also significantly protected against stunting compared with carriers of HbAA or HbAC. This indicates differing mechanisms of protection against malaria of HbAS and HbAC and might help to understand why HbC is restricted to distinct areas of West Africa.

After the identification of the human interferon-gamma (IFNG) variant G54D (c.287GA, ss105106770) in DNA samples from Ghana, West Africa, systematic mutation screening of IFNG by the LightCycler((R))-based procedure of high-resolution melting (HRM) revealed additional rare mutations. All variants occurred heterozygously only and were confirmed either by their detection in other individuals and/or by repeated DNA sequencing of independent PCR products.

Background Severe malarial anaemia is a major cause of mortality from malaria. Although of enormous relevance, its pathogenesis is largely unknown. Interestingly, the extent of anaemia greatly exceeds the loss of erythrocytes due to direct destruction by the pathogen Plasmodium falciparum . Immune response against the parasite is partially mediated through the Fc receptor for immunoglobulin (Ig) G IIa (FcγRIIa, CD32). The presence of an arginine instead of a histidine residue at amino acid position 131 (H131R) in the extracellular domain of FcγRIIa reduces the affinity of the receptor for IgG 2 and IgG 3 isotypes but increases the binding activity for C reactive protein (CRP). Methods In Ghana, West Africa, 2504 children with severe malaria and 2027 matched healthy controls were studied for the FcγRIIa H131R polymorphism in order to ascertain its influence on major manifestations of the disease. The study group included patients with partly overlapping symptoms of severe malaria, among them 1591 cases with severe anaemia, 562 cases with cerebral malaria, and 497 cases with other malaria complications. Results Analyses of the genotype distributions indicated that, under a recessive model, FcγRIIa 131RR was positively associated with severe malaria collectively (OR 1.20, 95% CI 1.05 to 1.38; p=0.007, p corrected =0.021) and, after stratification for phenotypes, with severe anaemia (OR 1.33, 95% CI 1.13 to 1.57; p=0.001, p corrected =0.009), but not with cerebral malaria (OR 1.04, 95% CI 0.82 to 1.33; p=0.733) or other malaria complications (OR 1.03, 95% CI 0.78 to 1.37; p=0.827). No association was found with levels of parasitaemia. Conclusion The positive association with a CRP binding variant of FcγRIIa supports evidence for a role of CRP mediated defence mechanisms in the pathogenesis of severe malarial anaemia.

Our results suggest that there are at least two different underlying mechanisms of malaria anaemia, uncomplicated anaemia characterized by a slow and continuous development towards a deficit of red blood cells, and anaemia with complications characterized by a rapid and substantial loss of red blood cells. The uncomplicated form appears to be caused by chronic systemic inflammatory processes rather than malaria episodes or parasite densities, similar to what is found in other forms of anaemia of chronic disease (ACD).

Background While the protective effects of sickle cell trait (HbAS) against severe malaria and the resulting survival advantage are well known, the impact on the physical development in young children remains unclear. This study was aimed to investigate the relationship between HbS carriage and stunting in children below two years of age in a cohort from the Ashanti Region, Ghana. Methods 1,070 children were recruited at three months of age and followed-up for 21 months with anthropometric measurements performed every three months. Incidence rate ratios with 95% confidence intervals were calculated by Poisson regression to estimate the association of β-globin genotypes with the number of malaria episodes. Odds ratios (OR) were calculated for the association between the occurrence of β-globin genotypes and/or malaria episodes and stunting. The age-dependent between-group and within-group effects for the β-globin genotypes were assessed by population-averaged models estimated by generalized estimation equation with autoregressive correlation structure. Results Analyses showed a significantly lower age-dependent risk of stunting (OR 0.56; 95% CI 0.33–0.96) in carriers of the HbAS genotype (n = 102) in comparison to those with HbAA (n = 692). This effect was restricted to children who experienced malaria episodes during the observation period suggesting that the beneficial effect of the β-globin HbS variant on the incidence of stunting is closely linked to its protection from mild malaria episodes. Conclusion The lower risk of chronic malnutrition in early childhood, mediated by protection against mild malaria episodes, may contribute to the survival advantage of HbAS carriers in areas of high malaria transmission.

The geographical distributions of hemoglobin S (HbS), hemoglobin C (HbC), and alpha+-thalassemia (-alpha) strongly suggest balancing selection with malaria. However, whereas several studies indicate that the HbS carrier state protects against all major forms of clinical malaria, malaria protection on clinical grounds has been more difficult to confirm for HbC and -alpha, and questions remain as to whether it applies to all forms of the disease.To assess the association between major clinical forms of severe falciparum malaria and HbS, HbC, and -alpha.Case-control study of 2591 children with severe falciparum malaria enrolled at a tertiary referral center in Ghana, West Africa, and 2048 age-, sex-, and ethnicity-matched control participants recruited by community surveys.Frequencies of HbS, HbC, and -alpha in patients and controls, including stratifications of patients for signs of disease.Patients presented with partly overlapping signs of disease, including severe anemia (64%), cerebral malaria (22%), respiratory distress (30%), hyperparasitemia (32%), prostration (52%), acidosis (59%), and hyperlactatemia (56%). Carrier states of HbS, HbC, and -alpha were found in 1.4%, 9.4%, and 25.2% of the patients, respectively, and 14.8%, 8.7%, and 27.3% of controls. The HbS carrier state was negatively associated with all forms of the disease studied (overall odds ratio [OR], 0.08; 95% confidence interval [CI], 0.06-0.12). The HbC carrier state showed a negative association selectively with cerebral malaria (OR, 0.64; 95% CI, 0.45-0.91), and the -alpha carrier state showed a negative association selectively with severe anemia (OR, 0.82; 95% CI, 0.69-0.96).Whereas the HbS carrier state was found to be negatively associated with all major forms of severe falciparum malaria, the negative associations of the carrier states of HbC and -alpha appeared to be limited to cerebral malaria and severe anemia, respectively.

Objectives: Accurate serological assays are urgently needed to support public health responses to Zika virus (ZIKV) infection with its potential to cause foetal damage during pregnancy. Current flavivirus serology for ZIKV infections lacks specificity due to cross-reacting antibodies from closely related other flaviviruses. In this study, we evaluated novel serological tests for accurate ZIKV IgG detection. Methods: Our ELISAs are based on immune complex binding. The high specificity is achieved by the simultaneous incubation of labelled ZIKV antigen and unlabelled flavivirus homolog protein competitors. Two assays were validated with a panel of 406 human samples from PCR-confirmed ZIKV patients collected in Brazil (n = 154), healthy blood donors and other infections from Brazil, Europe, Canada and Colombia (n = 252). Results: The highest specificity (100% [252/252, 95% confidence interval (CI) 98.5-100.0]) was shown by the ZIKV ED3 ICB ELISA using the ED3 antigen of the ZIKV envelope. A similar test using the NS1 antigen (ZIKV NS1 ICB ELISA) was slightly less specific (92.1% [232/252, 95% CI 88.0-95.1]). The commercial Euroimmun ZIKV ELISA had a specificity of only 82.1% (207/252, 95% CI 76.8-86.7). Sensitivity was high (93-100%) from day 12 after onset of symptoms in all three tests. Seroprevalence of ZIKV IgG was analysed in 87 samples from Laos (Asia) confirming that the ED3 ELISA showed specific reactions in other populations. Conclusions: The novel ED3 ICB ELISA will be useful for ZIKV-specific IgG detection for seroepidemiological studies and serological diagnosis for case management in travellers and in countries where other flavivirus infections are co-circulating.

Sensitive and specific serological tests are mandatory for epidemiological studies evaluating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) prevalence as well as coronavirus disease 2019 (COVID-19) morbidity and mortality rates. The accuracy of results is challenged by antibody waning after convalescence and by cross-reactivity induced by previous infections with other pathogens. By employing a patented platform technology based on capturing antigen-antibody complexes with a solid-phase-bound Fcγ receptor (FcγR) and truncated nucleocapsid protein as the antigen, two SARS-CoV-2 IgG enzyme-linked immunosorbent assays (ELISAs), featuring different serum and antigen dilutions, were developed. Validation was performed using a serum panel comprising 213 longitudinal samples from 35 COVID-19 patients and a negative-control panel consisting of 790 pre-COVID-19 samples from different regions of the world. While both assays show similar diagnostic sensitivities in the early convalescent phase, ELISA 2 (featuring a higher serum concentration) enables SARS-CoV-2 IgG antibody detection for a significantly longer time postinfection (≥15 months). Correspondingly, analytical sensitivity referenced to indirect immunofluorescence testing (IIFT) is significantly higher for ELISA 2 in samples with a titer of ≤1:640; for high-titer samples, a prozone effect is observed for ELISA 2. The specificities of both ELISAs were excellent not only for pre-COVID-19 serum samples from Europe, Asia, and South America but also for several challenging African sample panels. The SARS-CoV-2 IgG FcγR ELISAs, methodically combining antigen-antibody binding in solution and isotype-specific detection of immune complexes, are valuable tools for seroprevalence studies requiring the (long-term) detection of anti-SARS-CoV-2 IgG antibodies in populations with a challenging immunological background and/or in which spike-protein-based vaccine programs have been rolled out.