Search Results (401)

Background: Studies comparing systemic and salivary antibody responses against SARS-CoV-2 between children and adults show conflicting results. Furthermore, it is still unclear whether salivary antibody testing could be a non-invasive approach to evaluate the humoral immune response. Methods: anti-SARS-CoV-2 IgG antibodies were measured in blood and saliva sample pairs from vaccinated adults to investigate whether salivary antibody response could be a non-invasive assessment of immune response. Salivary antibody levels were also compared between vaccinated children and adults to investigate local antibody responses. Results: Salivary IgG antibody response against SARS-CoV-2 largely reflects the systemic response in vaccinated adults. Salivary and systemic antibody concentrations were higher in vaccinated adults who had been infected, received schemes including mRNA-based vaccines, had more exposures, and a shorter time from last exposure. Salivary antibody detection was associated with schemes including mRNA-based vaccines, time from last exposure, and systemic antibody concentrations. Vaccinated children showed higher salivary antibody concentrations than adults. This difference remained when comparing antibody levels between children and adults under equal conditions (vaccination schemes, number of exposures, time from last exposure, COVID-19 history). Younger age, number of exposures, schemes including mRNA-based vaccines, and shorter time from last exposure were associated with salivary antibody levels in a multivariable linear regression analysis (p < 0.0001). Conclusions: Salivary antibody determination against SARS-CoV-2 could be a non-invasive assessment of the short-term immune response in adults with multiple exposures. Furthermore, the stronger salivary antibody response in children suggests that local immune protection may differ between children and adults, contributing to different outcomes. Full article

Accurate and sensitive antibody detection remains critical for advanced COVID-19 diagnostics and monitoring SARS-CoV-2 immunity. This study presents a highly sensitive technique for detecting anti-SARS-CoV-2 antibodies in human serum using an integrated photonic sensing platform. The platform utilizes disposable one-dimensional photonic crystal biochips engineered to sustain Bloch Surface Waves. The biochips are integrated into a custom-made optical set-up, which is capable of dual-mode detection: label-free refractometry and label-based fluorescence. Tests on human serum, including negative controls and positive samples from a recovered COVID-19 patient, confirmed the platform’s effective performance. In fluorescence mode, clear discrimination between positive and negative samples was achieved down to a 1:10⁴ serum dilution, with an optimal operating range centered around 1:10³ dilution. These results demonstrate the potential of the technique as a highly sensitive and versatile platform for antibody detection, with significant relevance for advanced COVID-19 diagnostics. Full article

Background: Rapid and high-throughput diagnostic methods are essential for controlling the spread of infectious diseases, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Lateral flow immunoassay (LFIA) strips provide a cost-effective and user-friendly platform for point-of-care testing. However, the sensitivity of conventional LFIA kits is often limited by the performance of their detection probes. This study reports a highly sensitive LFIA strip for detecting the SARS-CoV-2 nucleocapsid (NP) protein using platinum-decorated poly(2-vinylpyridine) nanoparticles (Pt-P2VPs) as probes. Methods: Monoclonal antibodies against SARS-CoV-2 NP were conjugated with Pt-P2VPs and incorporated into LFIA strips. The test line was coated with anti–SARS-CoV-2 NP monoclonal antibody, and the control line with goat anti-mouse IgG. Recombinant proteins, viral strains, and nasopharyngeal swab specimens from patients were used to evaluate assay performance, with reverse transcription polymerase chain reaction (RT-PCR) as the reference standard. Diagnostic accuracy was assessed using nonparametric statistical tests. Results: Pt-P2VP-based LFIA strips enabled sensitive detection of recombinant NP and inactivated SARS-CoV-2, with minimal cross-reactivity. In 200 clinical specimens (100 PCR-negative and 100 PCR-positive), the assay achieved 74% sensitivity and 100% specificity, with strong correlation to viral RNA load. Compared with conventional LFIA kits, Pt-P2VP strips demonstrated superior sensitivity at lower viral loads. Conclusions: Pt-P2VPs represent a promising probe material for enhancing LFIA performance and may facilitate the development of rapid, sensitive, and scalable immunoassays for infectious disease diagnostics in biomedical applications. Full article

Background/Objectives: Following the global spread of SARS-CoV-2, there was an urgent need for vaccine development to support immune protection. This study aimed to evaluate the impact of active and hybrid immunity on the durability of immunoglobulin G (IgG), neutralizing antibodies, and cellular immune responses over a two-year period. Methods: This longitudinal study was conducted from February 2021 to December 2023 at the Public Health Institute in Ostrava, Czech Republic. Anti-S IgG was measured using ELISA (Euroimmun), neutralizing antibodies via an in-house virus neustralization test (VNT), and cellular immune response using the IGRA test (ELISA, Euroimmun). Participants also completed a questionnaire on demographics, COVID-19 history, symptoms, and vaccination. Statistical analysis included descriptive and non-parametric tests (Mann–Whitney U, Kruskal–Wallis) at a 5% significance level. Results: The cohort included 149 individuals, 97.3% of whom were vaccinated with Comirnaty (Pfizer/BioNTech). A total of 17% had confirmed infection prior to vaccination and showed up to two-fold higher neutralizing antibody levels (p < 0.001) within 2–6 weeks postvaccination. Postvaccination infection was reported in 35% of participants. Although antibody levels declined over the 2–100 week period, participants remained seropositive across all three parameters. Cellular immune response (interferon-γ) remained consistently high throughout follow-up. Conclusions: The study demonstrates long-term durability of IgG and neutralizing antibodies and confirms durable cellular immunity up to two years postvaccination. Hybrid immunity significantly enhanced neutralizing antibody levels, supporting its added value in protective immunity against SARS-CoV-2. Full article

Testing medical countermeasures for SARS-CoV-2 transmission using vertebrates can be hindered by legislation regulating animal experimentation, high costs, and ethical concerns. To overcome these challenges, we propose a new Caenorhabditis elegans strain that constitutively expresses the human angiotensin-converting enzyme 2 receptor (ACE2). This resulted in significant impairment of reproduction and a defect in pharyngeal function compared to wild-type (WT) worms. SARS-CoV-2 infection was simulated by treating worms with the receptor-binding domain (RBD) of the spike protein, which caused dose-dependent and time-dependent pharyngeal impairment in ACE2 worms but not in WT worms. The toxicity of RBD was prevented by administering an anti-human ACE2 antibody, demonstrating that interactions with the ACE2 receptor are essential. The ACE2-expressing worm strain was further used for pharmacological research with Raloxifene. In vitro, 1–3 μM of Raloxifene reduced the entry of lentiviral particles carrying the Wuhan variant and B.1.1.7 UK and B.1.1.529 Omicron strains into HEK293-ACE2, in addition to particles expressing N501Y-mutated or P681H-mutated spike proteins. Raloxifene (0.1–1 μM) completely counteracted RBD toxicity in ACE2 worms, indicating that this strain offers a cost-effective in vivo screening platform for molecules with effects involving interactions with the ACE2 receptor. Full article

Background: Due to the wide host range of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), vaccination has been recommended for susceptible species in zoological collections, particularly to protect endangered species. The Zoetis^® Experimental Mink Coronavirus Vaccine (Subunit) was temporarily authorized in 2021–2024 for emergency use in North America for this purpose. However, there are limited data regarding its safety or efficacy in non-domestic mammals. The present study was conducted to assess the ability of this vaccine to elicit serum neutralizing titers against SARS-CoV-2 in selected animals from the Toronto Zoo (TZ) vaccinated during 2022. Methods: Serum samples were collected from 24 individuals across four families (Cervidae, Felidae, Ursidae, and Hyaenidae) and tested using a surrogate virus neutralization test (sVNT) and a plaque-reduction neutralization test (PRNT). Results: The results showed that all species developed some neutralizing titers after at least one vaccine dose, except for polar bears, which showed no seroconversion. Felids and hyenas had the highest neutralizing titers, which peaked at 3 and declined between 4 and 6 months after boost. These differences may stem from species-specific immune responses or lack of vaccination protocols tailored to individual species. Conclusions: While natural infection with SARS-CoV-2 could not be ruled out in the cohort of this study, insights from our results have the potential to inform future vaccine recommendations for non-domestic species. Furthermore, our study highlighted the value of competitive assays in assessing serological responses across a broad range of exotic species, for which reagents, such as anti-isotype antibodies, are often unavailable. Full article

Serological testing for SARS-CoV-2-specific antibodies, particularly those targeting the nucleocapsid protein, plays a key role in assessing past infection and estimating population-level seroprevalence. The seroprevalence of nucleocapsid antibodies against SARS-CoV-2 was evaluated in 1048 blood donors using the Elecsys Anti-SARS-CoV-2 electrochemiluminescence immunoassay. Participants completed a questionnaire to assess risk factors, symptoms during SARS-CoV-2 infection and vaccination status. The overall SARS-CoV-2 seroprevalence was 89.69%. Seroprevalence was not significantly associated with gender or age. In multivariate logistic regression, most investigated risk factors showed no significant association with seroprevalence. However, residence area and vaccination status were independently associated with SARS-CoV-2 seropositivity. Donors from rural areas had significantly higher odds of seropositivity (aOR = 1.68; 95% CI: 1.01–2.79; p = 0.045) compared to those from urban areas. Unvaccinated individuals were more likely to test positive for SARS-CoV-2 compared to vaccinated participants (aOR: 2.59; 95% CI: 1.35–4.99; p = 0.004). After three years of the COVID-19 pandemic, the prevalence of SARS-CoV-2 among blood donors was remarkably high, indicating that the vast majority of this population group had been exposed to the virus. This study highlights the risk factors for SARS-CoV-2 infection and the differences in antibody prevalence between vaccinated and unvaccinated individuals. Our findings underscore the pivotal role of vaccination in controlling the pandemic and provide valuable insights for policymakers in designing targeted strategies to curb future SARS-CoV-2 transmission. Full article

Background: Thyroid dysfunction, including non-thyroidal illness syndrome (NTIS), is commonly observed in critically ill patients and has been reported in COVID-19, particularly in those with severe disease. NTIS is defined by low free triiodothyronine (fT3) with normal or low thyroid-stimulating hormone (TSH) and free thyroxine (fT4) levels. Thyroid autoantibodies may also reflect immune system activation. The relationship between thyroid hormone alterations, autoimmunity, and clinical severity in COVID-19 remains incompletely understood. Methods: We conducted a retrospective study of 276 patients hospitalized with COVID-19, including 138 in the intensive care unit (ICU) and 138 in general wards. A control group of 110 hospitalized, non-infected patients was also analyzed. Serum concentrations of TSH, fT3, fT4 and reverse T3 (rT3) were measured. The presence of anti-thyroid peroxidase (anti-TPO), anti-thyroglobulin (anti-Tg), and thyrotropin receptor antibodies (TRAb) was assessed. Results: NTIS was observed in 44.2% of ICU patients, 18.1% of non-ICU patients, and 1.8% of controls. The fT3/rT3 ratio was lowest in ICU patients (median 0.11 vs. 0.16 in non-ICU and 0.22 in controls). Thyroid autoantibodies were significantly more prevalent in COVID-19 patients than in controls, with anti-TPO antibodies being the most frequently detected. Their presence, even in patients without known thyroid disease, may reflect immune activation associated with SARS-CoV-2 infection. Conclusions: NTIS and thyroid autoimmunity are frequent in hospitalized COVID-19 patients and may reflect disease severity and immune activation. Our study highlights the prognostic relevance of routine thyroid testing, including the fT3/rT3 ratio and combined autoantibody positivity (notably the triple-positive pattern), by directly comparing ICU and non-ICU patients with a non-COVID control group. Full article

Background: Following SARS-CoV-2 infection, the necessity of vaccination after natural infection remains uncertain. However, many asymptomatic individuals who test negative virologically may nevertheless receive vaccination without being aware of their prior infection. Investigating the implications for vaccine safety and efficacy is crucial. Methods: We analyzed the daily fluctuations in anti-SARS-CoV-2 IgG antibody levels during the enrollment period of a phase 3 randomized, double-blinded, placebo-controlled clinical trial of a tetravalent COVID-19 protein vaccine, SCTV01E. Additionally, we investigated the relationship between baseline IgG levels and their protection against COVID-19 in participants who received placebo. Results: The daily enrolled participants with different baseline IgG levels (<338 BAU/mL, 338–1000 BAU/mL, >1000 BAU/mL) showed dynamic changes with the enrollment date. Among participants with baseline IgG levels < 338 BAU/mL, vaccination conferred a relative protective efficacy of 69.15% (95% CI: 51.14–80.52%) against symptomatic SARS-CoV-2 infection compared with the control group. Conversely, in those with higher baseline IgG levels (≥338 BAU/mL), vaccination did not confer additional benefit. In the placebo group, the relative protection in participants with baseline IgG levels ≥ 338 BAU/mL was 93.79% (87.60%, 96.89%) compared to that of those with baseline IgG levels < 338 BAU/mL. The safety profile of SCTV01E in participants with baseline IgG ≥ 338 BAU/mL was comparable to that in participants with <338 BAU/mL, with favorable safety profiles. Conclusions: During the SCTV01E phase 3 clinical trial, an anti-SARS-CoV-2 IgG antibody IgG level of 338 BAU/mL was suitable for screening individuals in the early phase post-infection alongside virological tests. Vaccinating the infected population was safe and did not compromise efficacy. Clinical Trial: NCT05308576. Full article

The ongoing COVID-19 pandemic has underscored the urgent need for rapid, sensitive, and versatile diagnostic tools. In this study, we developed a nanogold-based lateral flow immunoassay (LFIA) capable of detecting both SARS-CoV-2 nucleocapsid (N) protein antigens and anti-N IgG antibodies at the point of care. Following optimization of colloidal gold nanoparticle size, pH, and protein conjugation parameters, LFIA strips were assembled in two formats: a competitive assay for antigen detection and a sandwich assay for antibody detection. In the competitive format, gold nanoparticles (AuNPs)-conjugated N protein were used to detect varying concentrations of free N protein. The test line signal inversely correlated with antigen concentration, confirming the assay’s specificity and effectiveness. For antibody detection, the sandwich LFIA format employed immobilized anti-human IgG to capture anti-N antibodies in serum samples from COVID-19 patients. Strong test line signals were observed in samples collected ≥11 days post-symptom onset, indicating a time-dependent increase in IgG detectability. These results demonstrate that the AuNP-based LFIA platform provides a flexible, rapid, and low-cost diagnostic solution, suitable for both early antigen detection and serological monitoring during SARS-CoV-2 infection and recovery. Full article

COVID-19 has triggered the rapid adoption of human organoid-based tissue culture models to overcome the limitations of the commonly used Vero cell line that did not fully recapitulate SARS-CoV-2 infection of human tissues. As the primary site of SARS-CoV-2 infection, the human nasal epithelium (HNE) cultivated in vitro and differentiated at air–liquid interface (ALI) is an ideal model to study infection processes and for testing anti-viral antibodies and drugs. However, the need for primary basal cells to establish the ALI-HNE limits the scalability of this model system. To try and bypass this bottleneck, we devised an ALI-differentiated form of the human adenocarcinoma cell line Calu-3, reported to model most aspects of authentic SARS-CoV-2 infection, including viral entry. The ALI-Calu-3 were tested for infection by a panel of SARS-CoV-2 variants, including ancestral (VIC01) and early pandemic lineages (VIC2089, Beta, Delta), and Omicron subvariants (BA2.75, BA4, BA5, XBB1.5). All tested lineages infected the ALI-HNE. In stark contrast, infection of the ALI-Calu-3 by Omicron subvariants BA4 and XBB1.5 was reduced. These data support the use of ALI-Calu-3 as a complementary, intermediary model for most but not all SARS-CoV-2 lineages, and places the ALI-HNE as the benchmark culture model for SARS-CoV-2 infection. Full article

Background/Objectives: Parvovirus B19 (B19V) is a non-enveloped single-stranded DNA virus transmissible by blood transfusion, with potentially severe outcomes in immunocompromised and pregnant recipients. In this study, we investigated the B19V prevalence in 441,084 blood donations from Salzburg, Austria, collected between 2012 and 2024, focusing on changes in epidemiological dynamics before, during, and after the SARS-CoV-2 pandemic. Additionally, the B19VB19V persistence and its implications for deferral policies were assessed. Methods: Donor samples were screened for B19VB19V DNA by qPCR (2012–2024) and for SARS-CoV-2 total anti-N antibodies (2020–2024). B19VB19V prevalence rates, cycle threshold (Ct) values, and seasonal distribution were compared between pre-pandemic, pandemic, and post-pandemic phases. Follow-up testing of initially B19VB19V-positive donors was performed after a 2-year deferral period. Results: The B19VB19V positivity rate of 0.13% (2012–2019) significantly decreased to 0.02% during the SARS-CoV-2 pandemic (2020–2022). A substantial increase occurred post-pandemic, with prevalence reaching 1.47% in 2024. Significant lower Ct values were observed in the post-pandemic phase, indicating higher viral loads. Additionally, younger donors (aged 18–45 years) showed significantly lower Ct values. After a 2-year deferral, 39% of re-tested donors remained B19VB19V DNA-positive. Conclusions: B19VB19V circulation increased substantially after the SARS-CoV-2 pandemic. Our observation is consistent with international reports and is likely due to an ‘immunity debt’ that has been accumulated due to pandemic-related public health interventions. Targeted B19VB19V screening and strict deferral strategies may be warranted particularly during outbreak periods to protect high-risk transfusion recipients. Full article

Background/Objectives: The coronavirus disease 2019 (COVID-19) has more severe symptoms and increased mortality among men than women. To address the prognostic impact of vaccination, comorbidities, and inflammatory biomarkers on classified clinical outcomes in hospitalized COVID-19 patients, we compared common and sex differences. Methods: Besides laboratory and clinical parameters at hospital admission, we performed a common and sex-based comparative analysis for the clinical outcomes, RT-qPCR analyses, and measured severe acute respiratory syndrome coronavirus (SARS-CoV-2)-specific IgM and IgG antibody levels of 702 COVID-19 patients in a single centre from June 2020 to April 2022. Results: Pro-inflammatory biomarkers (C-reactive protein (CRP), interleukin-6 (IL-6), fibrinogen, lactate dehydrogenase (LDH), D-dimer, ferritin), and liver enzymes (AST, ALT, GGT) were significantly more increased in COVID-19 male patients and generally elevated with the severity of clinical outcome, regardless of the SARS-CoV-2 variant. Cycle threshold (Ct) values of RT-qPCR testing were in negative correlation with IL-6 in COVID-19 male patients, indicating that higher viral load largely increased IL-6 levels in parallel with the severity of clinical outcome and regardless of vaccination. IgG levels were higher in early post-COVID-19 male patients. Comorbidities were more frequent in COVID-19 female patients and generally more common in the severe clinical outcomes. Vaccination was negatively correlated with the severity of clinical outcome, liver enzymes, LDH, and inflammatory parameters in hospitalized COVID-19 patients, while the risk of pneumonia was reduced. Vaccination reduced the need for corticosteroid and anti-inflammatory therapies, but increased the need for antiviral drug treatment. Conclusions: In addition to confirming inflammatory biomarkers and the importance of anti-inflammatory therapy in vaccinated patients, this study showed that vaccination reduces, but does not prevent, mortality in patients with COVID-19. Full article

Background: COVID-19 vaccination has been a key tool in protecting healthcare workers (HCWs), but breakthrough infections have occurred. The durability of vaccine-induced immunity and its impact on HCWs remain critical for public health strategies. Methods: In this small cohort study (n = 32), we assessed antibody levels and breakthrough infection rates in HCWs over 12 months post-vaccination, providing insights for booster strategies and infection control. A cohort of 32 HCWs was screened for SARS-CoV-2 infection using weekly self-administered swabs and blood samples collected at baseline, 6 months, and 12 months. SARS-CoV-2 antibodies (IgG, IgM) targeting spike proteins and nucleocapsids were analyzed using a multi-antigen serology panel. Pooled nucleic acid testing was employed for infection detection. Results: Nine participants showed breakthrough infections, with nucleocapsid antibodies indicating prior infection. Eight of these cases occurred after the third vaccine dose during the Omicron-dominant period. Anti-spike antibody levels declined significantly in participants without prior infection, while those with breakthrough infections exhibited increased levels. The half-life of S1 and S1 receptor-binding domain (RDB) vaccine-induced antibodies was 144 and 166 days, respectively, which aligns with CDC data. These findings provide valuable insights for determining the optimal timing of booster doses. Conclusions: Our findings highlight the waning antibody levels over time and the occurrence of breakthrough infections. Although based on a small sample, these data support the need for ongoing monitoring and timely boosters. Full article

Background: Vaccination effectively reduces the risk of infection, including COVID-19 yet older adults often receive insufficient attention despite their increased vulnerability. The study aimed to correlate serological results with underlying conditions, vaccination status, and COVID-19 history. Methods: This non-interventional, multicenter study aimed to assess vaccination coverage and SARS-CoV-2 antibody levels among residents of eight long-term care facilities (LTCFs) in Southern Poland. Data collection took place between January and June 2022, with 429 participants recruited based on their ability to provide informed consent and their residency in LTCFs. Sociodemographic data, medical history, and COVID-19-related information—including infection history and vaccination status—were collected through surveys. Blood samples were obtained for serological testing using enzyme-linked immunosorbent assays (ELISA) to detect anti-SARS-CoV-2 antibodies. Statistical analysis, including Spearman’s correlation, revealed significant associations between antibody levels and vaccination status, as well as between RT-PCR-confirmed COVID-19 infections and higher antibody titers. Results: Among the seven different qualitative serological, only the Anti-SARS-CoV-2 NCP (IgG) and Anti-SARS-CoV-2 (IgA) tests showed a positive correlation with the Anti-SARS-CoV-2 QuantiVac (IgG) test, which was used as a comparator. A weak correlation was noted with the age of the residents. Conclusions: Our findings suggest that vaccination positively influences antibody responses, underscoring the importance of immunization among LTCF residents. Additionally, certain comorbidities—such as degenerative joint disease and diabetes—showed weak correlations with higher antibody levels. This study provides valuable insights into the humoral immune response to COVID-19 in vulnerable populations residing in LTCFs. Full article