anti-RBD Antibodies Research Articles

RBD-displaying OMV nanovaccine boosts immunity against SARS-CoV-2

BackgroundSince the emergence of SARS-CoV-2, the causative agent of COVID-19, the global health landscape has confronted an unprecedented and formidable challenge. The SARS-CoV-2 receptor-binding domain (RBD) is a key antigen in vaccine design. However, its low immunogenicity has been a hurdle, resulting in the production of minimal anti-RBD antibodies even when combined with alum adjuvant. Outer membrane vesicles (OMVs), secreted by Gram-negative bacteria, are nanospherical structures that can display or deliver antigens while also providing adjuvant activity through pathogen-associated molecular patterns (PAMPs).ResultsIn this study, we utilized the SpyTag (ST)/SpyCatcher (SC) bioconjugation system to couple OMV and SARS-CoV-2 RBD in vitro. We successfully prepared a ‘plug-and-display’ nanovaccine OMV-RBD, which demonstrated good safety profiles and promoted the uptake of antigens by DCs and the maturation of BMDCs by activating TLR3 and NOD2 signaling pathways. Both intranasal and intramuscular immunization with OMV-RBD vaccine elicited robust antigen-specific humoral and cellular immune responses. Importantly, the induced antibodies effectively inhibited the binding of RBD to human angiotensin-converting enzyme 2 (hACE2) and neutralized SARS-CoV-2 pseudoviruses.ConclusionsThis vaccine platform offers an alternative strategy for developing recombinant subunit vaccines against SARS-CoV-2, potentially enhancing immune responses and improving vaccine efficacy.Graphical abstract

Dual-Mode Immunosensor for Antibody Detection: Harnessing the Versatility of Antibody-Based Nanozymes across Optical and Electrochemical Platforms.

In the early years of the 21st century, numerous viral infectious diseases have proliferated, prompting intensified efforts to devise more effective diagnostic methods. In response, various biosensors have emerged with the aim of overcoming the constraints of conventional diagnostic techniques. Nanomaterial-based biosensors have revolutionized conventional approaches, significantly enhancing biosensor performance and effectively tackling these challenges. A diverse array of nanoparticles and nanomaterials has been systematically synthesized, engineered, and employed to augment the functionalities of biosensors. This work capitalizes on the properties of gold-platinum bimetallic nanoclusters (NCs) embedded in the structure of an immunoglobulin (IgG) (Au/Pt NCs-IgG), unveiling a novel double strategy for the detection of antibodies that leverages both their catalytic NC scaffold and the biorecognition element. The detection mechanism revealed the unique oxidase-like properties of Au/Pt NCs-IgG. This distinctive property, in addition to previously reported peroxidase-like activity, positions Au/Pt NCs-IgG as an effective probe in both optical and electrochemical sandwich enzyme-linked immunosorbent assays, facilitating their incorporation in different sensor frameworks and their utilization across various applications. As a study case, anti-SARS-CoV-2 antibodies (anti-RBD IgG antibodies) were employed as the target analyte. A linear detection range was found between 0.5 and 100 ng/mL for optical immunosensors and 50-300 ng/mL for electrochemical immunosensors. The validation of the immunosensor in clinical samples demonstrated its promising diagnostic value. The significantly differential signal obtained between positive and negative clinical samples underscores the suitability of both sensors for point-of-care diagnostic applications.

Validation and Clinical Performance of a Non-Commercial ELISA for SARS-CoV-2 Anti-RBD IgA Antibodies.

COVID-19 is caused by SARS-CoV-2, first identified in 2019. The Cuban vaccines, Abdala and Mambisa, have demonstrated efficacy in preventing SARS-CoV-2 infection. Immunoglobulin A (IgA) are the main line of defense against pathogens invading the respiratory or digestive tract and its presence in serum can be measured to assess vaccine efficacy. ELISAs are a valuable tool for assessing vaccine immunogenicity. These tests should be validated to ensure their reliability and suitability. The objective of this study was to validate a non-commercial ELISA for the quantification of total anti-RBD IgA in serum samples to support clinical studies. This assay demonstrated high clinical specificity (97.3%). The accuracy and precision of the assay showed an overall error of less than 20% at all levels in QCs. Re-evaluation of samples showed a mean difference of less than 30% in 90.2% of cases. Anti-RBD IgA titers correlated with viral neutralization titers and percentage inhibition of RBD-ACE2 binding. This assay was found to be highly accurate and reproducible for the quantification of anti-RBD IgA, met the most stringent acceptance criteria and is fit for purpose. It is currently being used to evaluate the immunogenicity of the Abdala and Mambisa vaccines.

Tracking Immunity: An Increased Number of COVID-19 Boosters Increases the Longevity of Anti-RBD and Anti-RBD-Neutralizing Antibodies.

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. 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. 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. 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.

Evaluation of anti-SARS-CoV-2 RBD antibody response after booster dose of SpikoGen® in individuals with two previous doses of Sinopharm and its association with HLA-DR and -DQ alleles.

It has been demonstrated that COVID-19 vaccines confer significant protection, but temporal decay in the vaccine-induced antibodies has been reported; therefore, a third booster dose was considered. Human leukocyte antigen (HLA) class II molecules act as antigen presenting structures, play critical roles in the formation of an efficient antibody response. The current study aimed to evaluate the anti-receptor binding domain (RBD) antibody response after the booster dose of SpikoGen® vaccine in individuals with a history of Sinopharm primary vaccination series and its association with HLA-DQB1 and -DRB alleles. Whole blood samples were drawn from 95 eligible individuals before and three weeks after the booster dose of SpikoGen®. Quantitative measurement of anti-RBD IgG and qualitative assessment of anti-RBD IgA was performed using the ELISA method and HLA-DQB1 and -DRB loci were genotyped by low-resolution SSP-PCR method. A significant increase was observed in the anti-RBD IgG antibodies after the booster dose of SpikoGen® (baseline: 1.82±0.55 GMT, after: 2.28±0.36 GMT)(P<0.0001). The median fold change of anti-RBD IgG antibodies for DRB1*14 positive individuals (3.96 (1.47-31.75)) was significantly higher than DRB1*14 negative people (1.18 (1.08-1.34))(P=0.008). In addition, the median fold change of anti-RBD IgG antibodies for DQB1*04 positive individuals (1.39 (1.21-3.43)) was higher than those which were DQB1*04 negative (1.18 (1.08-1.34)), however it was marginally significant (P=0.060). The seroconversion incidence for anti-RBD IgA antibodies was 68.42%. In conclusion, our study showed that the booster dose of SpikoGen® can elicit a robust anti-RBD antibody response which was positively associated with DRB1*14 allele.

Estimating SARS-CoV-2 Omicron XBB.1.5 Spike-Directed Functional Antibody Levels From an Anti-Receptor Binding Domain Wuhan-Hu-1-Based Commercial Immunoassay Results.

We investigated whether antibody concentrations measured in plasma using the Roche Elecsys® Anti-SARS-CoV-2 S assay (targeting the receptor binding domain, RBD) could estimate levels of Wuhan-Hu-1 and Omicron XBB.1.5 spike-directed antibodies with neutralizing ability (NtAb) or those mediating NK-cell activity. We analyzed 135 plasma samples from 39 vaccinated elderly nursing home residents. A strong correlation was found for NtAb against both Wuhan-Hu-1 (Rho = 0.73, p < 0.001) and Omicron XBB.1.5 (sub)variants (Rho = 0.73, p < 0.001). Moderate positive correlations were observed for NK-cell activity, based on lysosome-associated membrane protein 1 (LAMP1)-producing NK cells stimulated with Wuhan-Hu-1 (Rho = 0.43, p < 0.001) and Omicron XBB.1.5 spike proteins (Rho = 0.50, p < 0.001). Similarly, interferon-gamma (IFN-γ)-producing NK-cell frequencies showed moderate correlations (Wuhan-Hu-1: Rho = 0.43, p < 0.001; Omicron XBB.1.5: Rho = 0.50, p < 0.001). Random Forest models accurately predicted NtAb levels against Wuhan-Hu-1 (R2 = 0.72), though models for Omicron XBB.1.5 were less robust. Anti-RBD antibody concentrations of 4.73 and 5.02 log10 BAU/mL predicted high NtAb levels for Wuhan-Hu-1 and Omicron XBB.1.5, respectively. Antibody thresholds for predicting functional NK cell-mediated responses were 4.73 log10 and 4.54 log10 BAU/mL for Wuhan-Hu-1 and Omicron XBB.1.5, respectively. For LAMP1-producing NK cells, the thresholds were 4.94 and 4.75 log10 BAU/mL for Wuhan-Hu-1 and Omicron XBB.1.5, respectively. In summary, total anti-RBD antibody levels measured by the Roche assay may allow inference of NtAb levels and, to a lesser extent, Fc-mediated NK-cell responses against Omicron XBB.1.5.

Immunologic assessment of the impact of SARS-CoV-2 vaccine booster doses on humoral immunity: a cross-sectional study in morocco

To assess the impact of the SARS-CoV-2 booster dose on the immune response against COVID-19, we conducted a cross-sectional study in the Casablanca-Settat region of Morocco. The study included 2,802 participants from 16 provinces, all of whom had received three doses of a SARS-CoV-2 vaccine. IgG antibodies targeting the S1 RBD subunit of the SARS-CoV-2 spike protein were quantified using the SARS-CoV-2 IgG II Quant assay and measured on the Abbott Architect i2000SR instrument. Adjusted seroprevalence of anti-RBD antibodies showed that participants who received two doses of ChAdOx1-S followed by a BBIBP-CorV booster had a seroprevalence rate of 99.68% (95% CI: 99.39–99.83%), while those who received a BNT162b2 booster had a rate of 99.67% (95% CI: 99.38–99.82%). Both rates were higher than those observed with other vaccination regimens. The evaluation of booster dose effects revealed significant differences in anti-RBD antibody levels across various vaccination regimens: two doses of BBIBP-CorV compared to three doses of BBIBP-CorV (P < 0.0001), two doses of BNT162b2 versus three doses of BNT162b2 (P = 0.023), two doses of ChAdOx1-S versus two doses of ChAdOx1-S with a BNT162b2 booster (P = 0.023), and two doses of BBIBP-CorV versus two doses of BBIBP-CorV with a BNT162b2 booster (P < 0.0001). However, no significant difference was found between two doses of ChAdOx1-S and three doses of ChAdOx1-S (P = 0.23). Participants with prior SARS-CoV-2 exposure who received two doses of ChAdOx1-S followed by either a BBIBP-CorV or BNT162b2 booster showed higher levels of anti-RBD IgG antibodies (P = 0.042 and P = 0.001, respectively). Interestingly, individuals with comorbidities who received the BNT162b2 booster dose exhibited a significantly stronger humoral response (P < 0.05). In conclusion, our findings highlight the effectiveness of the BNT162b2 booster dose in eliciting a strong immune response. The high seroprevalence rates achieved with both BNT162b2 and BBIBP-CorV boosters reflect the country’s robust vaccination strategy.

Enhancing protective immunity against SARS-CoV-2 with a self-amplifying RNA lipid nanoparticle vaccine.

RNA-based vaccines against SARS-CoV-2 have demonstrated promising protective immunity against the global COVID-19 epidemic. Enhancing the intensity and duration of mRNA antigen expression is anticipated to markedly boost antiviral immune responses. Self-amplifying RNA (saRNA) represents a next-generation platform for RNA-based vaccines, amplifying transcripts in situ to augment the expression of encoded immunogens. Here, we develop a saRNA nanovaccine, formulated with a mutated saRNA encoding the receptor-binding domain (RBD) of the SARS-CoV-2 spike glycoprotein, encapsulated within a lipid nanoparticle (LNP-saRNA-RBD). This LNP-saRNA vaccine platform enables efficient delivery of saRNA-RBD, inducing enhanced and prolonged expression of the RBD antigen. LNP-saRNA-RBD vaccination stimulated the generation of antigen-specific T cells, promoting their differentiation into a long-lived effector memory phenotype. Immunization with LNP-saRNA-RBD induced a germinal center response in draining lymph nodes, leading to the production of anti-RBD IgG antibodies with the ability to neutralize SARS-CoV-2 pseudovirus. Furthermore, prime-boost immunizations with LNP-saRNA-RBD conferred protection to mice against SARS-CoV-2 challenge by suppressing viral infection and replication, as well as pulmonary inflammatory responses and associated damage. Taken together, these findings provide strong support for advancing the development of LNP-saRNA-RBD as a safe and efficacious vaccine candidate against SARS-CoV-2 infection.

Safety and Effectiveness of the Pfizer-BioNTech COVID-19 Vaccine among Health Staff in Sulaimani City, Iraq: A Prospective Cohort Study

A cohort study was conducted among 210 health staff members in Sulaimani city to assess the safety and effectiveness of the Pfizer-BioNTech vaccine. They were divided into two groups: vaccinated and unvaccinated. The vaccinated group received two doses of the Pfizer vaccine, while the unvaccinated group did not receive any vaccines during this study. Vaccine reactogenicity was assessed using a self-report form. Whereas vaccine immunogenicity was assessed by testing the anti-receptor binding domain IgG (anti-RBD IgG) antibody. Several adverse effects were observed with each dose. The most frequent adverse effects were pain at the inoculation site, tiredness, myalgia and fever. The average adverse effects per person in the first and second doses were 5.3 (SD 3.3) and 6.3 (SD 3.5) respectively (p = 0.005). The immunized group's anti-RBD IgG antibody levels were greatly improved after taking the first and second doses (32.50 and 44.92 binding antibody units (BAU)/mL respectively). After eight months of taking the two doses, the antibody level dropped to 17.00 BAU/mL. This study indicates that the vaccine can be safe and effective for enhancing antibody production.

Antibody Response to SARS-CoV-2 Vaccines in Transplant Recipients and Hemodialysis Patients: Data from the Dominican Republic.

Background: The global COVID-19 pandemic has resulted in approximately 7 million deaths and a historic vaccination effort, with over 13.6 billion doses administered. Despite this, understanding of immune responses in vulnerable populations, such as transplant recipients (TR) and hemodialysis patients (HD), remains limited, especially outside the US and Europe. Methods: To address this gap, we analyzed blood samples and deidentified data from the Instituto Nacional de Coordinación de Trasplante (INCORT) in The Dominican Republic, measuring antibody levels to SARS-CoV-2 post-infection and vaccination with BNT162b2 (Pfizer-BioNTech) and Sinovac-CoronaVac (Sinovac) in TR, HD, and healthy controls (CO). Using a fluorescent multiplex assay (mPlex-CoV) and mixed-effects modeling, we assessed variations in anti-S, anti-RBD, and anti-N IgG antibodies. Results: The results indicate that the CO group experienced an early peak in anti-S and anti-RBD antibodies, followed by stabilization. In contrast, the TR and HD groups showed a slower, gradual increase in antibodies. Despite fluctuations in the HD group, both the TR and HD groups maintained high anti-S and anti-RBD IgG levels, indicating a back-boosting effect from vaccination. However, elevated anti-N IgG levels in the TR and HD groups suggest potential reinfections. Additionally, prior SARS-CoV-2 infection led to higher anti-S IgG levels, with BNT162b2 associated with higher anti-S IgG and CoronaVac associated with higher anti-N IgG levels. Conclusion: These findings highlight the variability in antibody responses and the need for targeted public health strategies to diverse immunological profiles.

Possible rapid reduction of anti-RBD antibody titre after SARS-CoV-2 mRNA vaccination in pregnant women: Multicentre prospective study.

Pregnant women are at increased risk for severe illness associated with coronavirus disease 2019 (COVID-19) compared to nonpregnant women. The aim of this multicenter prospective study was to assess the current COVID-19 vaccination status of pregnant women in the southern Osaka district and to compare their antibody titers with those of nonpregnant women. Serum antibody titers of anti-NCP antibodies (antibodies against the SARS-CoV-2 nucleocapsid) and anti-RBD antibodies (the receptor binding domain of the S1 subunit of the spike protein) were evaluated in 753 pregnant women at 34-35 weeks of gestation from October 2021 to March 2022. Anti-RBD antibody titre was also investigated in 1003 health care workers at Kindai University hospital 3 and 6 months after a second dose of the vaccine from March 2021 to April 2021. 519 (68.9%) pregnant women were vaccinated during pregnancy, of whom 497 (95.8%) received two doses. The COVID-19 infection rate calculated from the number of pregnant women with a positive anti-NCP antibody titre or with confirmed diagnosis was 5.1% (12/234) in the unvaccinated and 3.5% (18/519) in the vaccinated. The estimated half-life calculated from anti-RBD antibody titers and the number of days between vaccination and antibody testing was 39.9 days. The antibody titre and half-life in pregnant women were significantly lower and shorter than in nonpregnant women aged 20-39 years (109.4 days). Our study showed that pregnant women may have lower vaccine-acquired COVID-19 immunity than nonpregnant women.

The results of vaccination against novel coronavirus infection in adolescents with allergic diseases

Novel coronavirus infection requires analyzing its course in patients with allergic diseases. Patients with atopic allergic diseases remain insufficiently studied with regard to the peculiarities of the course of both the underlying allergic disease and infectious processes caused by viruses and bacteria. Epithelial cells in bronchial asthma do not respond sufficiently to interferons, suggesting that SARS-CoV-2 infection may suppress spontaneous upregulation of angiotensin-converting enzyme expression, which ultimately reduces disease severity, but at the same time makes patients with allergic atopic diseases susceptible to other viral infections. The results obtained indicate statistically significant differences in the formation of anti-RBD IgG antibodies to SARS-CoV-2 between the group of adolescents with bronchial asthma vaccinated against a new coronavirus infection and those not vaccinated against it. During the follow-up period after 6 months, a statistically significant increase in anti-RBD IgG titer to SARS-CoV-2 due to novel coronavirus infection was observed among the unimmunized children. Clinical parameters indicated a favorable course of atopic process and control of bronchial asthma exacerbations in adolescents who received vaccination against both new coronavirus infection and influenza, while those who did not receive vaccination against these viral infections had bronchial asthma exacerbations due to respiratory infection. Also among patients with bronchial asthma who received influenza vaccination, there were no cases of influenza A and bronchial asthma exacerbations due to respiratory infections. In this regard, influenza vaccination is an important intervention to maintain control of asthma exacerbations. It is noteworthy that no new coronavirus infection was reported among vaccinated adolescents within a year after immunization. At the same time, 6 months after vaccination against a new coronavirus infection, we observed a statistically significant increase in antibody levels in unvaccinated adolescents, indicating the presence of high viral neutralizing activity. Vaccination against novel coronavirus infection in patients with bronchial asthma may be considered a possibility.

Electrochemical Immunosensors on Laser-Induced Graphene Platforms for Monitoring of Anti-RBD Antibodies After SARS-CoV-2 Infection.

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has posed a major challenge to global health. The development of fast, accurate, and accessible diagnostic methods is essential in controlling the disease and mitigating its impacts. In this context, electrochemical biosensors present themselves as promising tools for the efficient monitoring of SARS-CoV-2 infection. We have developed a highly specific biosensor for the detection of anti-SARS-CoV-2 antibodies in patient sera. The use of the RBD-S region as an antigen, although purified to minimize cross-linking, poses a specific challenge. The structural similarity between SARS-CoV-2 and other respiratory viruses, as well as the complexity of the serum matrix, hinders robust analytical strategies to ensure diagnostic accuracy. This work presents a novel immunosensor for COVID-19 diagnosis using laser-induced graphene (LIG) electrodes subjected to electrochemical reduction with graphene (named rGraphene-LIG). In the present study, we chose an initial approach focused on demonstrating the concept and evaluating the feasibility of the rGraphene-LIG sensor for SARS-CoV-2 detection. The rGraphene-LIG electrodes presented a notable current increase for the redox probe in the aqueous solution of a mixture of 5 mmol L-1 potassium ferricyanide/ferrocyanide ([Fe(CN)6]3-/[Fe(CN)6]4-) in 0.1 mol L-1 KCl (pH set at 7.4). As a proof of concept, the rGraphene-LIG electrode was applied for antibody determination in real samples using cyclic voltammetry, and a limit of detection (LOD) of 0.032 μg L-1 was achieved. When determining antigens in commercial samples, we obtained an LOD of 560 ηg mL-1 and a limit of quantification of 1677 ηg mL-1. The results of the electrochemical experiments were in accordance with the surface roughness obtained from atomic force microscopy images. Based on these results, the rGraphene-LIG electrode is shown to be an excellent platform for immunoglobulin detection when present in individuals after antigenic exposure caused by SARS-CoV-2.

Methotrexate treatment hampers induction of vaccine-specific CD4 T cell responses in patients with IMID

ObjectivesMethotrexate (MTX) is one of the most commonly used medications to treat rheumatoid arthritis (RA). However, the effect of MTX treatment on cellular immune responses remains incompletely understood. This raises...

Monitoring humoral responses against three SARS-CoV-2 vaccines in a university population from Chihuahua, Mexico.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has spread worldwide since 2019. Survey of the antibodies against SARS-CoV-2 is one of the most important measures of immunity since it can give an idea on the effectiveness of administered vaccines and the serologic status of individuals. We determined the concentrations of blood IgM and IgG against three SARS-CoV-2 proteins in vaccinated teachers and students among a university population from Chihuahua, Mexico. Humoral response surveillance against the 3C-like proteinase (3CLpro), nuclear protein (NP), and receptor binding domain (RBD) of SARS-CoV-2 was carried out. A total of 239 samples were analyzed: 67 from teachers who were vaccinated with CanSino and 172 from students (27.9% were vaccinated with AstraZeneca, 32.6% with Sinovac, 24.4% with Pfizer-BioNTech, 15.1% with other vaccines). Significant differences in the levels of IgG were observed between serum from individuals prior to vaccination (preimmunization serum) and from those that were vaccinated with CanSino. However, samples from asymptomatic individuals did not show differences between the preimmunization and post-immunization serum. The three vaccinated groups (AstraZeneca, Pfizer and Sinovac) did not show significant differences in anti-RBD IgG antibody titers compared to the positive control group, except for a Pfizer non-COVID-19 subgroup where the level of antibodies in the Pfizer group was 1.7 times higher. Neither vaccine group showed significant differences between those individuals who previously had COVID-19 and uninfected individuals. These results provide a picture of the situation at the time when in-person classes resumed.

IgG neutralization potential of COVISHIELD™ vaccinated individual’s sera after booster vaccination: Longitudinal and prospective cohort study

The novel SARS-CoV-2 (COVID-19) has caused widespread human turmoil by posing challenges concerning infection prevention, disease diagnosis, and treatment. Several approved vaccines including Sinovac (CoronaVac), COVISHIELD™ (Oxford/AstraZeneca formulation), Janssen (Johnson &amp; Johnson), Sputnik V (Gamaleya), Covaxin (Bharat Biotech), Pfizer (BNT162b2), and others are being used to combat COVID-19. It is crucial to evaluate the kinetics of SARS-CoV-2 antibodies to predict the possibility of reinfection and the longevity of vaccination protection. There is a lack of data on longitudinal humoral antibody dynamics following two and three doses of the SARS-CoV-2 vaccination ChAdOx1-nCOV (COVISHIELDTM) in Indians. Thus, concerns about the efficacy of current vaccines have been raised by a sharp rise in coronavirus disease 2019 (Covid-19) cases caused by sub-variants of SARS-CoV-2 (Severe acute respiratory syndrome corona virus 2) in communities that have received massive vaccinations. The relative immunogenicity and safety of various COVID-19 immunizations administered as a third (booster) dose are not well known. We examined the reactogenicity and immunogenicity of the COVID-19 vaccine as a third dose after two doses of COVISHIELDTM to produce data to optimize the selection of booster vaccinations. After three doses of the COVID-19 vaccine, we evaluated the sera of COVISHIELDTM vaccine recipients for their ability to neutralize the virus. Primary immunization with two doses of COVISHIELDTM vaccine recipients provided significant protection against symptomatic disease caused by the SARS-CoV-2 variants. A COVISHIELDTM vaccine booster vaccine recipient substantially increased protection. The immunization findings showed a significant difference (p ≥ 0.001) between the COVID-19 naive vaccine (n = 438) and the sera of COVID-19-positive recovered subjects (n = 371) who received three doses of COVISHIELDTM. Our findings reveal that anti-RBD antibodies persist over time, which may reduce the probability of reinfection. A three-dose vaccination (n = 53) increases defense against variations by noticeably increasing cross-neutralizing antibody titers. Particularly against variants with antibody escape mutations.

Longevity of hybrid immunity against SARS-CoV-2 in adults vaccinated with an adenovirus-based COVID-19 vaccine

BackgroundHybrid immunity provides better protection against COVID-19 than vaccination or prior natural infection alone. It induces high magnitude and broadly cross-reactive neutralising anti-Spike IgG antibodies. However, it is not clear how long these potent antibodies last, especially in the context of adenovirus-based COVID-19 vaccines.MethodsWe conducted a longitudinal cohort study and enrolled 20 adults who had received an adenovirus-based COVID-19 vaccine before a laboratory-confirmed SARS-CoV-2 infection. We followed up the study participants for 390 days post the initial breakthrough infection. We assessed the longevity and cross-reactive breadth of serum antibodies against SARS-CoV-2 variants of concern (VOCs), including Omicron.ResultsThe binding anti-Spike IgG antibodies remained within the reported putative levels for at least 360 days and were cross-neutralising against Beta, Gamma, Delta, and Omicron. During the follow up period, a median of one SARS-CoV-2 re-infection event was observed across the cohort, but none resulted in severe COVID-19. Moreover, the re-exposure events were associated with augmented anti-Spike and anti-RBD IgG antibody titres.ConclusionsThis study confirms that hybrid immunity provides durable broadly cross-reactive antibody immunity against SARS-CoV-2 variants of concern for at least a year (360 days), and that it is further augment by SARS-CoV-2 re-exposure.

Preclinical assessment of a recombinant RBD-Fc fusion protein as SARS-CoV-2 candidate vaccine.

Waning immunity and emergence of new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), highlight the need for further research in vaccine development. A recombinant fusion protein containing the receptor-binding domain (RBD) fused to the human IgG1 Fc (RBD-Fc) was produced in CHO-K1 cells. RBD-Fc was emulsified with four adjuvants to evaluate its immunogenicity. The RBD-specific humoral and cellular immune responses were assessed by ELISA. The virus neutralizing potency of the vaccine was investigated using four neutralization methods. Safety was studied in mice and rabbits, and Antibody-Dependent Enhancement (ADE) effects were investigated by flow cytometry. RBD-Fc emulsified in Alum induced a high titer of anti-RBD antibodies with remarkable efficacy in neutralizing both pseudotyped and live SARS-CoV-2 Delta variant. The neutralization potency dropped significantly in response to the Omicron variant. RBD-Fc induced both TH2 and particularly TH1 immune responses. Histopathologic examinations demonstrated no substantial pathologic changes in different organs. No changes in serum biochemical and hematologic parameters were observed. ADE effect was not observed following immunization with RBD-Fc. RBD-Fc elicits highly robust neutralizing antibodies and cellular immune responses, with no adverse effects. Therefore, it could be considered a promising and safe subunit vaccine against SARS-CoV-2.

T cell responses to repeated SARS-CoV-2 vaccination and breakthrough infections in patients on TNF inhibitor treatment: a prospective cohort study

Understanding cellular responses to SARS-CoV-2 immunisations is important for informing vaccine recommendations in patients with inflammatory bowel disease (IBD) and other vulnerable patients on immunosuppressive therapies. This study investigated the magnitude and quality of T cell responses after multiple SARS-CoV-2 vaccine doses and COVID-19 breakthrough infection. This prospective, observational study included patients with IBD and arthritis on tumour necrosis factor inhibitors (TNFi) receiving up to four SARS-CoV-2 vaccine doses. T cell responses to SARS-CoV-2 peptides were measured by flow cytometry before and 2-4 weeks after vaccinations and breakthrough infection to assess the frequency and polyfunctionality of responding cells, along with receptor-binding domain (anti-RBD) antibodies. Between March 2, 2021, and December 20, 2022, 143 patients (118 IBD, 25 arthritis) and 73 healthy controls were included. In patients with either IBD or arthritis, humoral immunity was attenuated compared to healthy controls (median anti-RBD levels 3391 vs. 6280 BAU/ml, p=0.008) after three SARS-CoV-2 vaccine doses. Patients with IBD had comparable quantities (median CD4 0.11% vs. 0.11%, p=0.26, CD8 0.031% vs. 0.047%, p=0.33) and quality (polyfunctionality score: 0.403 vs. 0.371, p=0.39; 0.105 vs. 0.101, p=0.87) of spike-specific T cells to healthy controls. Patients with arthritis had lower frequencies but comparable quality of responding T cells to controls. Breakthrough infection increased spike-specific CD8 T cell quality and T cell responses against non-spike peptides. Patients with IBD on TNFi have T cell responses comparable to healthy controls despite attenuated humoral responses following three vaccine doses. Repeated vaccination and breakthrough infection increased the quality of T cell responses. Our study adds evidence that, in the absence of other risk factors, this group may in future be able to follow the general recommendations for COVID-19 vaccines. South-Eastern Norway Regional Health Authority, Coalition for Epidemic Preparedness Innovations (CEPI), Norwegian Institute of Public Health, Akershus University Hospital, Diakonhjemmet Hospital.

Expression and purification of SARS-CoV-2 receptor binding domain in Escherichia coli for diagnostic and therapeutic purposes.

SARS-CoV-2 causes a severe respiratory disease known as COVID-19 and is responsible for a global viral pandemic. The SARS-CoV-2 receptor binding domain (RBD) is located on the spike protein, which identifies and binds to the angiotensin-converting enzyme 2 (ACE2) receptor. The RBD is an important target for developing virus-neutralizing antibodies, vaccines, and inhibitors. In this study, recombinant SARS-CoV-2 RBD was expressed in E. coli BL21 (DE3) and purified and its binding activity was determined. Purification was conducted using the Ni-NTA column. ELISA. flow cytometry assays were set to evaluate the binding ability of recombinant RBD to different anti-RBD antibodies and native ACE2 receptors on HEK293A cells, respectively. The SDS-PAGE analysis revealed the corresponding band at 27 kDa in the culture after induction with 0.7 mM IPTG, while the corresponding band was not observed in the culture without IPTG induction. ELISA results showed that antibodies produced in the human sera could bind to the recombinant RBD protein and the commercial anti-RBD antibody. Also, flow cytometry analysis revealed that the recombinant RBD could bind to human ACE2 on the surface of HEK293A cells. Our outcomes displayed that the recombinant RBD expressed in the E. coli strain has biological activity and can be used as an antigen for the development of diagnosis kits and vaccines as well as a tool for screening drugs against SASR-CoV-2.