Search Results (87)

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: The anti-spike (S) SARS-CoV-2 antibodies confer neutralizing properties and their concentration may be related to COVID-19 protection. Anti-nucleocapsid (N) SARS-CoV-2 antibodies in mRNA COVID-19 vaccine recipients indicate infection. The aim of this study was to analyze the anti-S and anti-N titers 3 years after COVID-19 vaccination. Methods: Ninety-nine vaccinated healthcare workers provided blood samples in 2024 and filled out questionnaires about their COVID-19 history and boosters acceptance. Anti-spike and anti-nucleocapsid IgG were assessed with commercially available immunoassays, DiaSorin’s SARS-CoV-2 TrimericS IgG and Abbott’s SARS-CoV-2 IgG, respectively. Results: Three years after the primary COVID-19 vaccination, the anti-S SARS-CoV-2 antibody concentration was still high. However, it dropped in comparison to the data obtained a year before (3600 vs. 2040 BAU/mL), possibly due to the lack of boosters. In contrast, the percentage of anti-N seropositive individuals grew from 34% two years after vaccination to 40.4% after three years. Subjects with SARS-CoV-2 infection within a year prior to the antibody measurements had statistically significantly higher median anti-S concentrations than those with tentatively no contact with SARS-CoV-2 (2940 vs. 1930 BAU/mL). Conclusions: Overall, our data indicates that although the booster vaccinations’ acceptance decreases, the circulating SARS-CoV-2 stimulates humoral immunity, resulting in high anti-S antibody concentrations even three years after the vaccination. 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

Background: Vaccination against SARS-CoV-2 has been pivotal in controlling the COVID-19 pandemic. However, understanding vaccine-induced immunity in immunocompromised individuals remains critical, particularly how prior exposure to other coronaviruses modulates immune responses. The influence of previous infections with endemic human coronaviruses (HCoVs), such as OC43, on SARS-CoV-2 immunity is not fully understood. This study evaluates antibody responses to COVID-19 vaccination in hemodialysis patients (HD), transplant recipients (TR), and healthy controls (CO), accounting for prior SARS-CoV-2 infection and baseline human coronavirus (HCoV) reactivity. Methods: We obtained longitudinal antibody measurements from 70 subjects (CO: n = 33; HD: n = 13; TR: n = 24) and assessed antibody kinetics across multiple post-vaccination time points using multivariate linear mixed modeling (MLMM). Results: Limited but measurable cross-reactivity was observed between SARS-CoV-2 and endemic HCoVs, particularly the $\beta$-coronavirus OC43. Pre-existing immunity in healthy individuals modestly enhanced vaccine-induced anti-spike (S) IgG responses, supported by post-vaccination increases in SARS-CoV-2 IgG. Prior SARS-CoV-2 infection significantly influenced anti-S and nucleocapsid (N) IgG responses but had limited impact on endemic HCoVs responses. Vaccine type and immune status significantly affected antibody kinetics. mRNA vaccination (BNT162b2) elicited stronger and more durable SARS-CoV-2 anti-S IgG responses than the inactivated CoronaVac vaccine, especially in immunocompetent individuals. Immunocompromised groups showed delayed or attenuated responses, with modest anti-S IgG cross-reactive boosting. Elevated anti-N IgG in CoronaVac recipients raised questions about its origin—infection or vaccine effects. MLMM identified key immunological and clinical predictors of antibody responses, emphasizing the critical role of host immune history. Conclusions: These findings highlight a constrained but meaningful role for HCoV cross-reactivity in SARS-CoV-2 immunity and vaccine responsiveness, underscore the need for infection markers unaffected by vaccination, and support development of broadly protective pan-coronavirus vaccines and tailored strategies for at-risk populations. Full article

Objectives: The aim of the present study was to better understand the antibody concentrations in healthcare workers (HCWs) from a hospital in Mexico City with a high density of COVID-19 patients. Methods: Up to 243 HCWs were recruited in 2020 and 2022 and were sorted into three groups: hybrid immunity (HI, natural infection plus vaccination), vaccine-induced immunity (VI), and unvaccinated but RT-qPCR negative at the beginning of the pandemic (UV). Peripheral blood and nasopharyngeal swab samples were obtained; additionally, saliva samples were obtained from the UV group. The titers of IgG, IgM, and IgA against the SARS-CoV-2 receptor-binding domain (RBD) and nucleocapsid (NCP) proteins were assessed using an in-house ELISA, and positivity to the virus was determined via RT-qPCR. Results: Most HI and VI participants were positive for serum anti-RBD IgG (92.8% and 100%, respectively), while 26.6% (for HI) and 19% (for VI) were positive for anti-NCP IgG. Regarding serum anti-RBD IgA, the VI and HI groups had positive rates of 87.3% and 66%, respectively. In contrast, the UV group showed a rate of 5.7% but the positivity for IgA in saliva was higher (52% for RBD and 35% for NCP). In addition, the highest antibody titers were obtained for anti-RBD IgG and IgA in the HI and VI groups, respectively. In saliva, the IgA antibody titer was higher for the RBD antigen (1:1280). Conclusions: These results strengthen our understanding of antibody concentrations in HCWs during two critical years of the pandemic in a general hospital with many COVID-19 patients. 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: Hemodialysis patients, due to impaired kidney function and compromised immune responses, face increased risks from SARS-CoV-2. Anti-nucleocapsid IgG (anti-IgG N) antibodies are a commonly used marker to assess prior infection in the general population; however, their efficacy for hemodialysis patients remains unclear. Methods: A retrospective study of 361 hemodialysis patients evaluated anti-IgG N antibodies for detecting prior SARS-CoV-2 infection. Antibody levels were measured using a chemiluminescence immunoassay (CLIA) over the four time points. Boxplots illustrated antibody distribution across sampling stages and infection status. Logistic regression and receiver operating characteristic (ROC) curve analysis determined diagnostic accuracy, sensitivity, specificity, and optimal cutoff values. Results: Among the 361 hemodialysis patients, 36 (10.0%) had SARS-CoV-2 infection. Sex distribution showed a trend toward significance (p = 0.05). Boxplot analysis showed that anti-IgG N levels remained low in non-infected patients but increased in infected patients, peaking at the third sampling. Anti-IgG N demonstrated high diagnostic accuracy (AUC: 0.973–0.865) but declined over time (p = 0.00525). The optimal cutoff at C1 was 0.01 AU/mL (sensitivity 1.00, specificity 0.94). Adjusted models had lower predictive value. Conclusions: Anti-IgG N antibodies showed high diagnostic accuracy for detecting prior SARS-CoV-2 infection in hemodialysis patients, though performance declined over time. These findings highlight the need for tailored diagnostic strategies in this vulnerable population. Full article

Virus-like nanoparticles (VNPs) based on Moloney murine leukemia virus represent a well-established platform for the expression of heterologous molecules such as cytokines, cytokine receptors, peptide MHC (pMHC) and major allergens, but their application for inducing protective anti-viral immunity has remained understudied as of yet. Here, we variably fused the wildtype SARS-CoV-2 spike, its receptor-binding domain (RBD) and nucleocapsid (NC) to the minimal CD16b-GPI anchor acceptor sequence for expression on the surface of VNP. Moreover, a CD16b-GPI-anchored single-chain version of IL-12 was tested for its adjuvanticity. VNPs expressing RBD::CD16b-GPI alone or in combination with IL-12::CD16b-GPI were used to immunize BALB/c mice intramuscularly and subsequently to investigate virus-specific humoral and cellular immune responses. CD16b-GPI-anchored viral molecules and IL-12-GPI were well-expressed on HEK-293T-producer cells and purified VNPs. After the immunization of mice with VNPs, RBD-specific antibodies were only induced with RBD-expressing VNPs, but not with empty control VNPs or VNPs solely expressing IL-12. Mice immunized with RBD VNPs produced RBD-specific IgM, IgG_2a and IgG₁ after the first immunization, whereas RBD-specific IgA only appeared after a booster immunization. Protein/peptide microarray and ELISA analyses confirmed exclusive IgG reactivity with folded but not unfolded RBD and showed no specific IgG reactivity with linear RBD peptides. Notably, booster injections gradually increased long-term IgG antibody avidity as measured by ELISA. Interestingly, the final immunization with RBD–Omicron VNPs mainly enhanced preexisting RBD Wuhan Hu-1-specific antibodies. Furthermore, the induced antibodies significantly neutralized SARS-CoV-2 and specifically enhanced cellular cytotoxicity (ADCC) against RBD protein-expressing target cells. In summary, VNPs expressing viral proteins, even in the absence of adjuvants, efficiently induce functional SARS-CoV-2-specific antibodies of all three major classes, making this technology very interesting for future vaccine development and boosting strategies with low reactogenicity. Full article

The effectiveness of multiple COVID-19 vaccinations in individuals with a history of SARS-CoV-2 infection remains unclear; specifically, elucidation of the durability of anti-viral antibody responses could provide important insights for epidemiological applications. We utilized the BU ELISA protocol to measure the circulating SARS-CoV-2 receptor-binding domain (RBD) and nucleocapsid (N) specific IgG and IgA antibody levels in a cohort of individuals infected with SARS-CoV-2 in the spring of 2020, with the sample collection spanning six months to two years post-symptom onset. Further, we interrogated the neutralization activity of these samples against the ancestral SARS-CoV-2 (WA-1) and Delta and Omicron (BA.1) variants. Consistent with previous studies, we found a more rapid waning of anti-N compared to anti-RBD antibodies in months prior to the first vaccinations. Vaccine-induced antibody responses in individuals previously infected with SARS-CoV-2 were elevated and sustained for more than one year post-vaccination. Similarly, neutralization activity against WA-1, Delta, and Omicron increased and remained higher than pre-vaccination levels for one year after the first COVID-19 vaccine dose. Collectively, these results indicate that infection followed by vaccination yields robust antibody responses against SARS-CoV-2 that endure for one year. These results suggest that an annual booster would stably boost anti-SARS-CoV-2 antibody responses, preventing infection and disease. Full article

The COVID-19 pandemic highlighted the global necessity to develop fast, affordable, and user-friendly diagnostic alternatives. Alongside recognized tests such as ELISA, nanotechnologies have since been explored for direct and indirect diagnosis of SARS-CoV-2, the etiological agent of COVID-19. Accordingly, in this work, we report a method to detect anti-SARS-CoV-2 antibodies based on graphene-based field-effect transistors (GFETs), using a nanostructured platform of graphene with added gold nanorods (GNRs) and a specific viral protein. To detect anti-N-protein IgG antibodies for COVID-19 in human sera, gold nanorods were functionalized with the nucleocapsid (N) protein of SARS-CoV-2, and subsequently deposited onto graphene devices. Our test results demonstrate that the sensor is highly sensitive and can detect antibody concentrations as low as 100 pg/mL. Using the sensor to test human sera that were previously diagnosed with ELISA showed a 90% accuracy rate compared to the ELISA results, with the test completed in under 15 min. Integrating graphene and nanorods eliminates the need for a blocker, simplifying sensor fabrication. This hybrid sensor holds robust potential to serve as a simple and efficient point-of-care platform. Full article

Background: This study aimed to assess the antibody response to SARS-CoV-2 vaccines among healthcare workers (HCWs) from multiple outpatient clinics in Japan, examining the effects of baseline characteristics (e.g., sex, age, underlying condition, smoking history, occupation) and prior infections. Methods: A total of 101 HCWs provided serum at four time points between October 2020 and July 2023. HCWs received two to six doses of mRNA vaccine (BNT162b2 or mRNA-1273). Anti-nucleocapsid (N) and anti-spike (S) IgG antibodies against the ancestral Wuhan strain were measured using the Abbott Architect™ SARS-CoV-2 IgG assay. Univariate and regression analysis evaluated factors such as past infections, age, sex, smoking, underlying condition, and occupation. Results: After four to six doses, the median anti-S IgG titer in uninfected HCWs was 1807.30 BAU/mL, compared to 1899.89 BAU/mL in HCWs with prior infections. The median anti-N IgG titer was 0.10 index S/C in uninfected HCWs and 0.39 index S/C in infected HCWs. HCWs with prior infection had anti-S IgG titers 1.1 to 5.8 times higher than those without. Univariate and multivariate analyses indicated infection and vaccination significantly increased anti-S and anti-N IgG titers. Age, sex, smoking history and occupation did not influence antibody titers while underlying conditions were associated with lower anti-N IgG titers. Conclusions: Infection and vaccination were strongly associated with an increase in anti-S and anti-N IgG titers; however, the impact of hybrid immunity appeared to be limited and varied depending on the timing of the sampling. These findings provide valuable insights for developing personalized vaccination strategies and future vaccine development. Full article

Background/Objectives: Since the World Health Organization declared COVID-19 a pandemic in March 2020, the virus has caused multiple waves of infection globally. Arizona State University (ASU), the largest four-year university in the United States, offers a uniquely diverse setting for assessing immunity within a large community. This study aimed to test our hypothesis that an increased number of exposures to SARS-CoV-2 RBD through vaccination/boosters/infection will increase SARS-CoV-2 antibody seroprevalence by increasing the longevity of anti-RBD and anti-RBD-neutralizing antibodies. Methods: A serosurvey was conducted at ASU from 30 January to 3 February 2023. Participants completed questionnaires about demographics, respiratory infection history, symptoms, and COVID-19 vaccination status. Blood samples were analyzed for anti-receptor binding domain (RBD) IgG and anti-nucleocapsid (NC) antibodies, offering a comprehensive view of immunity from both natural infection and vaccination. Results: The seroprevalence of anti-RBD IgG antibodies was 96.2% (95% CI: 94.8–97.2%), and 64.9% (95% CI: 61.9–67.8%) of participants had anti-NC antibodies. Anti-RBD IgG levels correlated strongly with neutralizing antibody levels, and participants who received more vaccine doses showed higher levels of both anti-RBD IgG and neutralizing antibodies. Increasing the number of exposures through vaccination and/or infection resulted in higher and long-lasting antibodies. Conclusions: The high levels of anti-RBD antibodies observed reflect substantial vaccine uptake within this population. Ongoing vaccination efforts, especially as new variants emerge, are essential to maintaining protective antibody levels. These findings underscore the importance of sustained public health initiatives to support broad-based immunity and protection. Full article

Background/Objectives: The impact of vaccines against SARS-CoV-2 on the immunity of patients with multiple sclerosis (PwMS) is still not fully known. Further clarification could help address medical concerns related to the use of immunosuppressive and immunomodulatory medications, known as disease-modifying therapies (DMTs), in PwMS, as well as ensure adequate protection against severe outcomes of COVID-19. Therefore, the aim of our study was to evaluate the humoral and cellular immune response in PwMS treated with DMTs. Methods: The concentrations of IgG Spike (S) anti-SARS-CoV-2 antibodies and IgG Nucleocapsid (N) anti-SARS-CoV-2 antibodies, as well as interferon-gamma (IFN-γ) titers were analyzed in PwMS groups treated with dimethyl fumarate (DMF), interferon beta (IFN), and healthy control group. Results: Almost 100% of PwMS experienced seroconversion, which resulted from either vaccination and/or prior infection. Additionally, there were no significant differences between the study and control groups in terms of IgG (S) and (N) anti-SARS-CoV-2 antibody levels. However, interferon-gamma titers were lower in both PwMS groups, which may indicate adequate humoral and decreased cellular response to the examined PwMS. Additionally, after the division of the whole study group into two subgroups according to the time since the last vaccination, IgG (S) anti-SARS-CoV-2 and IFN-γ concentrations were significantly lower in the case of patients who were immunized more than 200 days before sample collection. No differences were observed in the case of subgroups in which sample collection was less than 200 days after vaccination when compared to the control group. Conclusions: This could indicate a time-related decrease in immunity in PwMS treated with DMTs. Full article

(1) Background: After the COVID-19 pandemic, there is concern regarding the immunity of the population to SARS-CoV-2 variants, particularly the Omicron variant and its sub-lineages. (2) Methods: The study involved analyzing the immune response and symptomatology of 27 vaccinated individuals who were subsequently infected by Omicron sub-lineages. Blood samples were collected for serological analysis, including the detection of IgG antibodies reactive to the Nucleocapsid (N) and Spike (S) antigens of SARS-CoV-2. Additionally, participants were interviewed to assess the intensity of symptoms during the infection. (3) Results: Despite the high levels of anti-Spike IgG observed after vaccination, all participants were infected by Omicron sub-lineages. The most common symptoms reported by participants were fever or chills, sore throat, and cough. The levels of anti-Spike IgG found prior to infection did not correlate with symptom intensity post-infection. However, it was observed that high post-infection anti-Nucleocapsid IgG levels correlated with mild symptoms during the course of the disease, suggesting a potential role for anti-N antibodies in symptom intensity. (4) Conclusions: In line with previous studies, the high levels of IgG anti-Spike resulting from vaccination did not provide complete protection against infection by the Omicron variant. Additionally, our data suggest that anti-Nucleocapsid IgG titers are negatively correlated with the intensity of the symptoms during mild infections. Full article

Understanding variables that influence antibody responses to COVID-19 vaccination within a population can provide valuable information on future vaccination strategies. In this population-based study, we examined the antibody responses to COVID-19 vaccination in Manitoba using residual serum specimens collected between January 2021 and March 2022 (n = 20,365). Samples were tested for spike and nucleocapsid IgG against SARS-CoV-2 using clinically validated assays. We assessed the impacts of multiple factors on post-vaccination antibody titres including type of vaccine, age, sex, geographic location, number of doses received, and timing of vaccination. Our investigation demonstrated that vaccination with one dose of Moderna mRNA-1273 elicited higher anti-spike IgG titres overall compared to Pfizer BNT162b2 vaccination, while one dose of Pfizer BNT162b2 followed by a second dose of Moderna mRNA-1273 exhibited higher titres than two doses of Pfizer BNT162b2 or Moderna mRNA-1273, irrespective of age. Age and time post-vaccination had considerable effects on antibody responses, with older age groups exhibiting lower anti-spike IgG titres than younger ages, and titres of those vaccinated with Pfizer BNT162b2 waning faster than those vaccinated with Moderna mRNA-1273 or a combination of Pfizer BNT162b2 and Moderna mRNA-1273. Antibody titres did not appear to be affected by sex or geographic location. Our results identify how factors such as age and type of vaccine can influence antibody responses to vaccination, and how antibody titres wane over time. This information highlights the importance of tailoring vaccine regimens to specific populations, especially those at increased risk of severe COVID-19 and can be used to inform future vaccination strategies, scheduling of booster doses, and public health measures. Full article