Overview of Neutralizing Antibodies and Their Potential in COVID-19

Macrophage membrane-coated nanoparticles for the treatment of infectious diseases

Infectious diseases severely threaten human health, and traditional treatment techniques face multiple limitations. As an important component of immune cells, macrophages display unique biological properties, such as biocompatibility, immunocompatibility, targeting specificity, and immunoregulatory activity, and play a critical role in protecting the body against infections. The macrophage membrane-coated nanoparticles not only maintain the functions of the inner nanoparticles but also inherit the characteristics of macrophages, making them excellent tools for improving drug delivery and therapeutic implications in infectious diseases (IDs). In this review, we describe the characteristics and functions of macrophage membrane-coated nanoparticles and their advantages and challenges in ID therapy. We first summarize the pathological features of IDs, providing insight into how to fight them. Next, we focus on the classification, characteristics, and preparation of macrophage membrane-coated nanoparticles. Finally, we comprehensively describe the progress of macrophage membrane-coated nanoparticles in combating IDs, including drug delivery, inhibition and killing of pathogens, and immune modulation. At the end of this review, a look forward to the challenges of this aspect is presented.

SARS-CoV-2 Neutralization Assays Used in Clinical Trials: A Narrative Review

Since the emergence of COVID-19, extensive research efforts have been undertaken to accelerate the development of multiple types of vaccines to combat the pandemic. These include inactivated, recombinant subunit, viral vector, and nucleic acid vaccines. In the development of these diverse vaccines, appropriate methods to assess vaccine immunogenicity are essential in both preclinical and clinical studies. Among the biomarkers used in vaccine evaluation, the neutralizing antibody level serves as a pivotal indicator for assessing vaccine efficacy. Neutralizing antibody detection methods can mainly be classified into three types: the conventional virus neutralization test, pseudovirus neutralization test, and surrogate virus neutralization test. Importantly, standardization of these assays is critical for their application to yield results that are comparable across different laboratories. The development and use of international or regional standards would facilitate assay standardization and facilitate comparisons of the immune responses induced by different vaccines. In this comprehensive review, we discuss the principles, advantages, limitations, and application of different SARS-CoV-2 neutralization assays in vaccine clinical trials. This will provide guidance for the development and evaluation of COVID-19 vaccines.

Blood Group Variations in COVID-19 Convalescent Plasma and Regular Blood Donors: A Comparative Analysis in the Serbian Population

This research explores the association between ABO blood groups and susceptibility to SARS-CoV-2 infection, analyzing Convalescent COVID-19 plasma (CCP) donors (n = 500) and healthy whole blood donors (BDs) (n = 9678) during the pandemic (1 May 2020 to 30 April 2021). A comparison is made with pre-pandemic BDs (n = 11,892) from 1 May 2018 to 30 April 2019. Significant differences in blood group distribution are observed, with blood group A individuals being three times more likely to be CCP donors. Conversely, blood groups B, O, and AB are less associated with CCP donation. Notably, blood group O is more prevalent among regular BDs, suggesting potential resistance to SARS-CoV-2 infection. This study underscores variations in blood group distribution during the pandemic compared to pre-pandemic periods. The findings support previous research indicating a link between blood group antigens and viral susceptibility, including SARS-CoV-2. Understanding these associations has implications for public health strategies, with potential for predicting COVID-19 outcomes and transmission patterns. Further research is crucial to explore molecular and immunological mechanisms, providing valuable insights for targeted preventive strategies and personalized healthcare in managing the impact of COVID-19.

From Detection to Protection: Antibodies and Their Crucial Role in Diagnosing and Combatting SARS-CoV-2

Understanding the antibody response to SARS-CoV-2, the virus responsible for COVID-19, is crucial to comprehending disease progression and the significance of vaccine and therapeutic development. The emergence of highly contagious variants poses a significant challenge to humoral immunity, underscoring the necessity of grasping the intricacies of specific antibodies. This review emphasizes the pivotal role of antibodies in shaping immune responses and their implications for diagnosing, preventing, and treating SARS-CoV-2 infection. It delves into the kinetics and characteristics of the antibody response to SARS-CoV-2 and explores current antibody-based diagnostics, discussing their strengths, clinical utility, and limitations. Furthermore, we underscore the therapeutic potential of SARS-CoV-2-specific antibodies, discussing various antibody-based therapies such as monoclonal antibodies, polyclonal antibodies, anti-cytokines, convalescent plasma, and hyperimmunoglobulin-based therapies. Moreover, we offer insights into antibody responses to SARS-CoV-2 vaccines, emphasizing the significance of neutralizing antibodies in order to confer immunity to SARS-CoV-2, along with emerging variants of concern (VOCs) and circulating Omicron subvariants. We also highlight challenges in the field, such as the risks of antibody-dependent enhancement (ADE) for SARS-CoV-2 antibodies, and shed light on the challenges associated with the original antigenic sin (OAS) effect and long COVID. Overall, this review intends to provide valuable insights, which are crucial to advancing sensitive diagnostic tools, identifying efficient antibody-based therapeutics, and developing effective vaccines to combat the evolving threat of SARS-CoV-2 variants on a global scale.

Potential of a Bead-Based Multiplex Assay for SARS-CoV-2 Antibody Detection

Serological assays for SARS-CoV-2 play a pivotal role in the definition of whether patients are infected, the understanding of viral epidemiology, the screening of convalescent sera for therapeutic and prophylactic purposes, and in obtaining a better understanding of the immune response towards the virus. The aim of this study was to investigate the performance of a bead-based multiplex assay. This assay allowed for the simultaneous testing of IgG antibodies against SARS-CoV-2 spike, S1, S2, RBD, and nucleocapsid moieties and S1 of seasonal coronaviruses hCoV-22E, hCoV-HKU1, hCoV-NL63, and hCoV-OC43, as well as MERS and SARS-CoV. We compared the bead-based multiplex assay with commercial ELISA tests. We tested the sera of 27 SARS-CoV-2 PCR-positive individuals who were previously tested with different ELISA assays. Additionally, we investigated the reproducibility of the results by means of multiple testing of the same sera. Finally, the results were correlated with neutralising assays. In summary, the concordance of the qualitative results ranged between 78% and 96% depending on the ELISA assay and the specific antigen. Repeated freezing-thawing cycles resulted in reduced mean fluorescence intensity, while the storage period had no influence in this respect. In our test cohort, we detected up to 36% of sera positive for the development of neutralising antibodies, which is in concordance with the bead-based multiplex and IgG ELISA.

Vaccination impairs de novo immune response to omicron breakthrough infection, a precondition for the original antigenic sin

Several studies have suggested the imprinting of SARS-CoV-2 immunity by original immune challenge without addressing the formation of the de novo response to successive antigen exposures. As this is crucial for the development of the original antigenic sin, we assessed the immune response against the mutated epitopes of omicron SARS-CoV-2 after vaccine breakthrough. Our data demonstrate a robust humoral response in thrice-vaccinated individuals following omicron breakthrough which is a recall of vaccine-induced memory. The humoral and memory B cell responses against the altered regions of the omicron surface proteins are impaired. The T cell responses to mutated epitopes of the omicron spike protein are present due to the high cross-reactivity of vaccine-induced T cells rather than the formation of a de novo response. Our findings, therefore, underpin the speculation that the imprinting of SARS-CoV-2 immunity by vaccination may lead to the development of original antigenic sin if future variants overcome the vaccine-induced immunity.

Engineered polyspecific antibodies: A new frontier in the field of immunotherapeutics

The 21st-century beginning remarked with the huge success of monospecific MAbs, however, in the last couple of years, polyspecific MAbs (PsAbs) have been an interesting topic and show promise of being biobetter than monospecific MAbs. Polyspecificity, in which a single antibody serves multiple specific target binding, has been hypothesized to contribute to the development of a highly effective antibody repertoire for immune defence. This polyspecific MAb trend represents an explosion that is gripping the whole pharmaceutical industry. This review is concerned with the current development and quality enforcement of PsAbs. All provided literature on monospecific MAbs and polyspecific MAbs (PsAbs) were searched using various electronic databases such as PubMed, Google Scholar, Web of Science, Elsevier, Springer, ACS, Google Patent and books via the keywords Antibody engineering, Polyspecific antibody, Conventional antibody, non-conventional antibody, and Single domain antibody. In the literature, there are more than 100 different formats to construct PsAb by quadroma technology, chemical conjugation and genetic engineering. Till March 2023, nine PsAb have been approved around the world, and around 330 are in advanced developmental stages, showing the dominancy of PsAb in the growing health sector. Recent advancements in protein engineering techniques and the fusion of non-conventional antibodies have made it possible to create complex PsAbs that demonstrate higher stability and enhanced potency. This marks the most significant achievement for cancer immunotherapy, in which PsAbs have immense promise. It is worth mentioning that seven out of the nine PsAbs have been approved as anti-cancer therapy. As PsAbs continue to acquire prominence, they could pave the way for the development of novel immunotherapies for multiple diseases.

Novel neutralizing SARS-CoV-2-specific mAbs offer detection of RBD linear epitopes

BACKGROUND

To stop the spread of the COVID-19 disease, it is crucial to create molecular tools to investigate and diagnose COVID-19. Current efforts focus on developing specific neutralizing monoclonal antibodies (NmAbs) elicited against the receptor-binding domain (RBD).

METHODS

In the present study, recombinant RBD (rRBD) protein was produced in E. coli, followed by immunizing mice with purified rRBD. ELISA was applied to screen the hybridomas for positive reactivity with rRBD protein. The linear and conformational epitopes of the mAbs were subsequently identified using western blot. Finally, the reactivity, affinity, and neutralization activity of the purified mAbs were evaluated using ELISA.

RESULTS

All mAbs exhibited similar reactivity trends towards both eukaryotic RBD and prokaryotic rRBD in ELISA. Among them, 2E7-D2 and 2B4-G8 mAbs demonstrated higher reactivity than other mAbs. Additionally, in western blot assays, these two mAbs could detect reducing and non-reducing rRBD, indicating recognition of linear epitopes. Notably, five mAbs effectively blocked rRBD- angiotensin-converting enzyme 2 (ACE2) interaction, while two high-affinity mAbs exhibited potent neutralizing activity against eukaryotic RBD.

CONCLUSION

In the current study, we generated and characterized new RBD-specific mAbs using the hybridoma technique that recognized linear and conformational epitopes in RBD with neutralization potency. Our mAbs are novel candidates for diagnosing and treating SARS-CoV-2.

Evaluating long-term antibody responses to booster doses of COVID-19 vaccines in the Pakistani population

Background & Objective

Nearly 80 million of the Pakistani population received two doses of the BBIBP-CorV vaccine, against SARS-CoV-2, and 2.6 million people received heterologous booster doses up to February 2022. Our objective was to measure the long-term change of antibody titers in persons vaccinated with Pfizer-BioNTech COVID-19 following two doses of BBIBP-CorV.

Methods

Serum specimens from forty-three participants were collected 4-8 weeks following two doses of BBIBP-CorV at the Indus Hospital & Health Network, Karachi. A second set of serum specimens were collected 2-12 months after Pfizer-BioNTech COVID-19 booster dose administration. Chemiluminescent Microparticle Immunoassay (CMIA, Abbott Alinity Quant), and the pseudotyped lentivirus antibody neutralization assay were performed on all specimens. The latter assay was reported as log half-maximal inhibitory concentrations (IC50), calculated using a nonlinear regression algorithm (log [inhibitor] versus normalized response variable slope) in Graph Pad Prism 9. Paired sample t-test was used to ascertain the statistical significance of the difference in means of antibody titers obtained before and after the booster vaccine doses.

Results

Mean log10 values obtained with CMIA before and after the booster dose were 2.90 AU/mL and 3.87 AU/mL respectively, while the corresponding log10 IC50 values obtained through pseudotyped lentivirus antibody neutralization assay were 2.45 and 2.80. These differences were statistically significant with CMIA (p = <0.00001), but not with pseudotyped lentivirus antibody neutralization assay (p = 0.06318.).

Conclusion

A heterologous booster dose with Pfizer-BioNTech COVID-19 vaccine following two doses of BBIBP results in increased total antibody titers, though neutralizing antibody titers may start to wane a few months after the booster dose.

Quantitative and Standardized Pseudovirus Neutralization Assay for COVID-19

COVID-19 is a global pandemic caused by the highly infectious SARS-CoV-2 virus. Efforts to combat SARS-CoV-2 infection include mass vaccination and development of monoclonal and convalescent plasma therapeutics that require precise measurements of correlative, functional neutralizing antibodies that prevent virus infection. Developing rapid, safe, easy-to-use, and high-quality neutralization assays are essential for the success of the massive effort. Here, we developed a vesicular stomatitis virus-based neutralization assay that was capable of quantifying varying degrees of neutralization in patient serum samples. This assay has two detection readouts, flow cytometry and live cell imaging. The two readout methods produced consistent values of all 50% neutralization titers, further enhancing measurement confidence on the assay. Moreover, the use of available reference standards such as the World Health Organization International Standard (NIBSC code 20/136) enables quantification and standardization of the pseudovirus neutralization assay with neutralizing antibody titers measured in International Units/mL. Quantitative and standardized neutralization assays are critical for reliable efficacy evaluation and comparison of numerous vaccines and therapeutics.

Unravelling humoral immunity in SARS-CoV-2: Insights from infection and vaccination

Following infection and vaccination against SARS-CoV-2, humoral components of the adaptive immune system play a key role in protecting the host. Specifically, B cells generate high-affinity antibodies against various antigens of the virus. In this review, we discuss the mechanisms of immunity initiation through both natural infection and vaccination, shedding light on the activation of B cell subsets in response to SARS-CoV-2 infection and vaccination. The innate immune system serves as the initial line of primary and nonspecific defence against viruses. However, within several days following infection or a vaccine dose, a virus-specific immune response is initiated, primarily by B cells that produce antibodies. These antibodies contribute to the resolution of the disease. Subsequently, these B cells transition into memory B cells, which play a crucial role in providing long-term immunity against the virus. CD4+ T helper cells initiate a cascade, leading to B cell somatic hypermutation, germinal center memory B cells, and the production of neutralizing antibodies. B-cell dysfunction can worsen disease severity and reduce vaccine efficacy. Notably, individuals with B cell immunodeficiency show lower IL-6 production. Furthermore, this review delves into several aspects of immune responses, such as hybrid immunity, which has shown promise in boosting broad-spectrum protection. Cross-reactive immunity is under scrutiny as well, as pre-existing antibodies can offer protection against the disease. We also decipher breakthrough infection mechanisms, especially with the novel variants of the virus. Finally, we discuss some potential therapeutic solutions regarding B cells including convalescent plasma therapy, B-1 cells, B regulatory cell (Breg) modulation, and the use of neutralizing monoclonal antibodies in combating the infection. Ongoing research is crucial to grasp population immunity trends and assess the potential need for booster doses in maintaining effective immune responses against potential viral threats.

A community study of neutralizing antibodies against SARS-CoV-2 in China

Background

The immune background of the overall population before and after the outbreak of SARS-CoV-2 in China remains unexplored. And the level of neutralizing antibodies is a reliable indicator of individual immunity.

Objectives

This study aimed to assess the immune levels of different population groups during a viral outbreak and identify the factors influencing these levels.

Methods

We measured the levels of neutralizing antibodies in 12,137 participants using the COVID19 Neutralizing Antibody Detection kit. The dynamics of neutralizing antibodies were analyzed using a generalized additive model, while a generalized linear model and multi-factor analysis of variance were employed to investigate the influencing factors. Additionally, statistical methods were used to compare neutralizing antibody levels among subgroups of the real-world population.

Results

Participants who received booster doses exhibited significantly higher levels of neutralizing antibodies compared to those who received only one or two doses (p<0.001). Both elderly [22.55 (5.12, 62.03) IU/mL, 55%] and minors [21.41 (8.15, 45.06) IU/mL, 56%] showed lower positivity rates and neutralizing antibody levels compared to young adults [29.30 (9.82, 188.08) IU/mL, 62%] (p<0.001). Furthermore, the HIV-positive group demonstrated a slightly lower seropositivity rate compared to the healthy group across the three vaccination time points. Notably, three months after the large-scale infection, both the neutralizing antibody level and positivity rate in real-world populations were higher than the previous record [300 (300, 300) IU/mL, 89%; 27.10 (8.77, 139.28) IU/mL, 60%], and this difference was statistically significant.

Conclusions

Increasing vaccine dosage enhances neutralizing antibody levels, resulting in greater and longer-lasting immunity. Monitoring immune levels in older individuals and those with AIDS is crucial. Additionally, the neutralizing antibodies generated from vaccination have not yet reached the threshold for achieving herd immunity, while individuals exhibit higher immune levels following a large-scale infection. These findings provide valuable insights for guiding new strategies in vaccine administration.

Weaker SARS-CoV-2 vaccine responses in nonalcoholic fatty liver disease with advanced liver fibrosis

Background

SARS-CoV-2 vaccine responses that could harbor potential risks to chronic liver diseased patients.

Aims

To assess immune response following Pfizer's SARS-CoV-2 vaccine in patients with different liver fibrosis severities of nonalcoholic fatty liver disease (NAFLD).

Methods

Clinical and histological (NAS-score and fibrosis stage) characteristics of NAFLD patients before vaccine were correlated with serologic vaccine responses of two doses of the BNT162b2. Serum SARS-CoV-2 spike immunoglobulins (anti-S) were assessed on day seven following immunization (Liaison assay).

Results

The mean-age of patients (n = 157) was 56.9 ± 13.2 years (46.5 % males). 94.8 % had a positive response (anti-S levels ≥ 19 AU/ml). The anti-S cutoff of 200 AU/ml used to separate strong vs. weak responses. A strong response (anti-S titers ≥ 200 AU/ml) was observed in 93/157 (59.2 %) patients with a mean-age of 53.1 ± 13.8 years (45.2 % males). A weak response (anti-S titers < 200 AU/ml) was observed in 64/157 (40.8 %) cases with a mean-age of 62.3 ± 10.2 years (p < 0.0001). The strong response subgroup had lower metabolic comorbidities, including glucose hemostasis, hypertension, and dyslipidemia (p < 0.04). Moreover, the strong response subgroup had fibrosis stages F0-F2 (75.3 % vs. 56.3 %) and lower rates of advanced stages F3-F4 (24.7 % vs. 43.8 %). The F0-F2 subgroups had significantly higher rates of strong responses than the F3-F4 stages. The anti-S ≥ 200 and anti-S ≥ 400 AU/ml response achieved in 66 % and 36.8 % of the F0-F2 population was significantly higher than the 45.1 % (p = 0.006) and 23.5 % (p = 0.05) in the F3-F4 population, respectively. The Fib-4 calculations and Fibroscan evaluations were consistent with histologic fibrosis assessment.

Conclusion

Advanced liver fibrosis (assessed by histology, Fib-4, or Fibroscan) is a risk factor for lower response to Pfizer's BNT162b2 vaccine, and patients should be prioritized for the vaccine booster against SARS-CoV-2.

Antibody escape, the risk of serotype formation, and rapid immune waning: Modeling the implications of SARS-CoV-2 immune evasion

As the COVID-19 pandemic progresses, widespread community transmission of SARS-CoV-2 has ushered in a volatile era of viral immune evasion rather than the much-heralded stability of "endemicity" or "herd immunity." At this point, an array of viral strains has rendered essentially all monoclonal antibody therapeutics obsolete and strongly undermined the impact of vaccinal immunity on SARS-CoV-2 transmission. In this work, we demonstrate that antibody escape resulting in evasion of pre-existing immunity is highly evolutionarily favored and likely to cause waves of short-term transmission. In the long-term, invading strains that induce weak cross-immunity against pre-existing strains may co-circulate with those pre-existing strains. This would result in the formation of serotypes that increase disease burden, complicate SARS-CoV-2 control, and raise the potential for increases in viral virulence. Less durable immunity does not drive positive selection as a trait, but such strains may transmit at high levels if they establish. Overall, our results draw attention to the importance of inter-strain cross-immunity as a driver of transmission trends and the importance of early immune evasion data to predict the trajectory of the pandemic.

Assessment of neutralization susceptibility of Omicron subvariants XBB.1.5 and BQ.1.1 against broad-spectrum neutralizing antibodies through epitopes mapping

The emergence of new variants of the SARS-CoV-2 virus has posed a significant challenge in developing broadly neutralizing antibodies (nAbs) with guaranteed therapeutic potential. Some nAbs, such as Sotrovimab, have exhibited varying levels of efficacy against different variants, while others, such as Bebtelovimab and Bamlanivimab-etesevimab are ineffective against specific variants, including BQ.1.1 and XBB. This highlights the urgent need for developing broadly active monoclonal antibodies (mAbs) providing prophylactic and therapeutic benefits to high-risk patients, especially in the face of the risk of reinfection from new variants. Here, we aimed to investigate the feasibility of redirecting existing mAbs against new variants of SARS-CoV-2, as well as to understand how BQ.1.1 and XBB.1.5 can evade broadly neutralizing mAbs. By mapping epitopes and escape sites, we discovered that the new variants evade multiple mAbs, including FDA-approved Bebtelovimab, which showed resilience against other Omicron variants. Our approach, which included simulations, endpoint free energy calculation, and shape complementarity analysis, revealed the possibility of identifying mAbs that are effective against both BQ.1.1 and XBB.1.5. We identified two broad-spectrum mAbs, R200-1F9 and R207-2F11, as potential candidates with increased binding affinity to XBB.1.5 and BQ.1.1 compared to the reference (Wu01) strain. Additionally, we propose that these mAbs do not interfere with Angiotensin Converting Enzyme 2 (ACE2) and bind to conserved epitopes on the receptor binding domain of Spike that are not-overlapping, potentially providing a solution to neutralize these new variants either independently or as part of a combination (cocktail) treatment.

Combined anti-S1 and anti-S2 antibodies from hybrid immunity elicit potent cross-variant ADCC against SARS-CoV-2

Antibodies capable of neutralizing SARS-CoV-2 are well studied, but Fc receptor-dependent antibody activities that can also significantly impact the course of infection have not been studied in such depth. Since most SARS-CoV-2 vaccines induce only anti-spike antibodies, here we investigated spike-specific antibody-dependent cellular cytotoxicity (ADCC). Vaccination produced antibodies that weakly induced ADCC; however, antibodies from individuals who were infected prior to vaccination (hybrid immunity) elicited strong anti-spike ADCC. Quantitative and qualitative aspects of humoral immunity contributed to this capability, with infection skewing IgG antibody production toward S2, vaccination skewing toward S1, and hybrid immunity evoking strong responses against both domains. A combination of antibodies targeting both spike domains support strong antibody-dependent NK cell activation, with 3 regions of antibody reactivity outside the receptor-binding domain (RBD) corresponding with potent anti-spike ADCC. Consequently, ADCC induced by hybrid immunity with ancestral antigen was conserved against variants containing neutralization escape mutations in the RBD. Induction of antibodies recognizing a broad range of spike epitopes and eliciting strong and durable ADCC may partially explain why hybrid immunity provides superior protection against infection and disease compared with vaccination alone, and it demonstrates that spike-only subunit vaccines would benefit from strategies that induce combined anti-S1 and anti-S2 antibody responses.

An Overview of the Conventional and Novel Methods Employed for SARS-CoV-2 Neutralizing Antibody Measurement

SARS-CoV-2 is the etiological agent of the coronavirus disease-19 (COVID-19) and is responsible for the pandemic that started in 2020. The virus enters the host cell through the interaction of its spike glycoprotein with the angiotensin converting enzyme-2 (ACE2) on the host cell's surface. Antibodies present an important role during the infection and pathogenesis due to many reasons, including the neutralization of viruses by binding to different spike epitopes. Therefore, measuring the neutralizing antibody titers in the whole population is important for COVID-19's epidemiology. Different methods are described in the literature, and some have been used to validate the main vaccines used worldwide. In this review, we discuss the main methods used to quantify neutralizing antibody titers, their advantages and limitations, as well as new approaches to determineACE2/spike blockage by antibodies.

Preventive treatment of coronavirus disease-2019 virus using coronavirus disease-2019-receptor-binding domain 1C aptamer by suppress the expression of angiotensin-converting enzyme 2 receptor

The cause of the worldwide coronavirus disease-2019 (COVID-19) pandemic is the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). It is known to employ the same entry portal as SARS-CoV, which is the type 1 transmembrane angiotensin-converting enzyme 2 (ACE2) receptor. The receptor-binding domain (RBD) is located on the spike S-protein's S1 subunit of the spike glycoprotein. The most important and effective therapy method is inhibiting the interaction between the ACE2 receptor and the S-spike RBD. An aptamer is a small, single-chain oligonucleotide that binds strongly to the target molecule. Recently, a CoV-2-RBD-1C aptamer-based system with a 51-base hairpin structure was discovered to have substantial binding affinity against the SARS-CoV-2RBD with similar binding sites at ACE. In the current study, we will study the aptamer's effect as a SARS-CoV-2 spike blocker and inhibit its ACE2 receptors' binding by studying the toxicity of aptamer for this cell line by calcein assay and the inhibition test of CoV-2-RBD-1C aptamers on spike RBD-ACE2 binding. The results show the half-maximum inhibitory concentration of CoV-2-RBD-1C aptamer is 0.08188 μM. The inhibition effect of CoV-2-RBD-1C aptamer on spike RBD-ACE2 binding was determined at half-maximal effective concentration of 0.5 μM concentration. The percentage of spike-ACE2 binding inhibition in A549-hACE2 cells in the D614G variant after 30 s was 77%. This percentage is higher than D614 and N501Y and equals 55% and 65%, respectively, at 0.15 μM of CoV-2-RBD-1C aptamer. The CoV-2-RBD-1C aptamer prevents virus entrance through spike inhibition, which results in a 90% reduction in spike D614 virus transduction at 1.28 μM. In conclusion, the CoV-2-RBD-1C aptamer might be an effective treatment against COVID-19 infection because it directly affects the virus by blocking the S-spike of SARS-CoV-2 and preventing ACE2 receptor binding.

Study on the Protective Immunity Induced by Pseudotyped Baculovirus Expressing the E Protein of Tembusu Virus in Ducklings

The Duck Tembusu virus (DTMUV), a pathogenic flavivirus, has been causing significant economic losses in the Chinese poultry industry since 2010. This virus can severely decrease egg production and inhibit the growth of laying ducks and ducklings. While many vaccines have been developed to prevent DTMUV infection, fresh outbreaks continue to occur, as few effective vaccines are available. The E glycoprotein of DTMUV is the primary target for inducing protective immunity in the natural host. Therefore, we conducted an investigation and successfully developed a recombinant baculovirus containing the DTMUV E gene. Ducklings were then vaccinated with the purified protein derived from this virus as a potential vaccine candidate. Our findings demonstrated that the E glycoprotein of DTMUV was highly expressed in Sf9 cells. The vaccination of ducklings with the recombinant baculovirus Bac-E resulted in the induction of strong humoral and cellular immune responses. Most significantly, we observed that the vaccine provided 100% protective immunity against lethal challenges with the DTMUV YY5 strain.

Generalizing the Wells-Riley Infection Probability: A Superstatistical Scheme for Indoor Infection Risk Estimation

Recent evidence supports that air is the main transmission pathway of the recently identified SARS-CoV-2 coronavirus that causes COVID-19 disease. Estimating the infection risk associated with an indoor space remains an open problem due to insufficient data concerning COVID-19 outbreaks, as well as, methodological challenges arising from cases where environmental (i.e., out-of-host) and immunological (i.e., within-host) heterogeneities cannot be neglected. This work addresses these issues by introducing a generalization of the elementary Wells-Riley infection probability model. To this end, we adopted a superstatistical approach where the exposure rate parameter is gamma-distributed across subvolumes of the indoor space. This enabled us to construct a susceptible (S)-exposed (E)-infected (I) dynamics model where the Tsallis entropic index q quantifies the degree of departure from a well-mixed (i.e., homogeneous) indoor-air-environment state. A cumulative-dose mechanism is employed to describe infection activation in relation to a host's immunological profile. We corroborate that the six-foot rule cannot guarantee the biosafety of susceptible occupants, even for exposure times as short as 15 min. Overall, our work seeks to provide a minimal (in terms of the size of the parameter space) framework for more realistic indoor SEI dynamics explorations while highlighting their Tsallisian entropic origin and the crucial yet elusive role that the innate immune system can play in shaping them. This may be useful for scientists and decision makers interested in probing different indoor biosafety protocols more thoroughly and comprehensively, thus motivating the use of nonadditive entropies in the emerging field of indoor space epidemiology.

Artificial intelligence-based HDX (AI-HDX) prediction reveals fundamental characteristics to protein dynamics: Mechanisms on SARS-CoV-2 immune escape

Three-dimensional structure and dynamics are essential for protein function. Advancements in hydrogen-deuterium exchange (HDX) techniques enable probing protein dynamic information in physiologically relevant conditions. HDX-coupled mass spectrometry (HDX-MS) has been broadly applied in pharmaceutical industries. However, it is challenging to obtain dynamics information at the single amino acid resolution and time consuming to perform the experiments and process the data. Here, we demonstrate the first deep learning model, artificial intelligence-based HDX (AI-HDX), that predicts intrinsic protein dynamics based on the protein sequence. It uncovers the protein structural dynamics by combining deep learning, experimental HDX, sequence alignment, and protein structure prediction. AI-HDX can be broadly applied to drug discovery, protein engineering, and biomedical studies. As a demonstration, we elucidated receptor-binding domain structural dynamics as a potential mechanism of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody efficacy and immune escape. AI-HDX fundamentally differs from the current AI tools for protein analysis and may transform protein design for various applications.

Anti-SARS-CoV-2 Immunoglobulins in Human Milk after Coronavirus Disease or Vaccination-Time Frame and Duration of Detection in Human Milk and Factors That Affect Their Titers: A Systematic Review

Human milk (HM) of mothers infected with or vaccinated against SARS-CoV-2 contains specific immunoglobulins, which may protect their offspring against infection or severe disease. The time frame and duration after infection or vaccination, during which these immunoglobulins are detected in HM, as well as the major factors that influence their levels, have not been fully elucidated. This systematic review aimed to collect the existing literature and describe the immune response, specifically regarding the immunoglobulins in HM after COVID-19 disease or vaccination in non-immune women. We conducted a systematic search of PubMed and Scopus databases to identify studies published up until 19 March 2023. In total, 975 articles were screened, and out of which 75 were identified as being relevant and were finally included in this review. Infection by SARS-CoV-2 virus primarily induces an IgA immune response in HM, while vaccination predominantly elevates IgG levels. These immunoglobulins give HM a neutralizing capacity against SARS-CoV-2, highlighting the importance of breastfeeding during the pandemic. The mode of immune acquisition (infection or vaccination) and immunoglobulin levels in maternal serum are factors that seem to influence immunoglobulin levels in HM. Further studies are required to determine the impact of other factors, such as infection severity, lactation period, parity, maternal age and BMI on immunoglobulin level in HM.

Neutralization of Wild-Type and Alpha SARS-CoV-2 Variant by CoronaVac® Vaccine and Natural Infection- Induced Antibodies

One of the immune responses desired to be achieved by SARS-CoV-2 vaccination is to create neutralizing antibodies (nAbs), thus preventing the development and spread of infection. The aim of this study was to investigate the seropositivity rate, anti-spike antibody levels, and neutralizing capacity of these antibodies against wild type (WT) and alpha variants in serum samples of individuals who had been naturally infected or vaccinated with CoronaVac®. Total anti-spike antibody levels were determined in all samples. Neutralization assays were performed by the reduction of the cytopathic effect in Vero-E6 cells with infectious WT and alpha SARS-CoV-2 variants. Although both naturally infected and vaccinated individuals were all seropositive for antispike antibodies, 84.8% of the vaccinated group, and 89.3% of the naturally infected group had detectable nAbs. The nAbs titers were significantly higher in the naturally infected group for both WT and alfa variant of the virus as compared to the vaccinated individuals. In this study, it was observed that all individuals became seropositive six weeks after exposure to the vaccine or the virus. Moreover, naturally infected individuals had higher levels of nAbs than those vaccinated. The presence of nAbs against the alpha variant in both naturally infected and vaccinated individuals suggests that these antibodies may also be protective against infections, which may be caused by other variants, such as delta and omicron.

Rapid engineering of SARS-CoV-2 therapeutic antibodies to increase breadth of neutralization including BQ.1.1, CA.3.1, CH.1.1, XBB.1.16, and XBB.1.5

SARS-CoV-2 Omicron variant XBB.1.5 has shown extraordinary immune escape even for fully vaccinated individuals. There are currently no approved antibodies that neutralize this variant, and continued emergence of new variants puts immunocompromised and elderly patients at high risk. Rapid and cost-effective development of neutralizing antibodies is urgently needed. Starting with a single parent clone that neutralized the Wuhan-Hu-1 strain, antibody engineering was performed in iterative stages in real time as variants emerged using a proprietary technology called STage-Enhanced Maturation. An antibody panel that broadly neutralizes currently circulating Omicron variants was obtained by in vitro affinity maturation using phage display. The engineered antibodies show potent neutralization of BQ.1.1, XBB.1.16, and XBB.1.5 by surrogate virus neutralization test and pM K_D affinity for all variants. Our work not only details novel therapeutic candidates but also validates a unique general strategy to create broadly neutralizing antibodies to current and future SARS-CoV-2 variants.

Complete blood count derived inflammatory biomarkers and the level of anti-SARS-CoV-2 NAb and S-RBD IgG among cancer survivors receiving COVID-19 vaccines

<b>Background</b>: In the era of coronavirus disease 2019 (COVID-19), it is mandatory to identify vulnerable people with cancers as they have impaired immune system that can lead to high mortality. This study analyzes the complete blood count (CBC) derived inflammatory biomarkers and the level of anti-SARS-CoV-2 neutralizing antibody (NAb) and spike protein’s receptor-binding domain immunoglobulin G (S-RBD IgG) among cancer survivors.<br /> <b>Methods</b>: A cross-sectional study was conducted in patients with either solid or hematological cancers who had received two-doses of COVID-19 vaccinations within six months.<br /> <b>Results</b>: From 119 subjects, the COVID-19 vaccines demonstrated laboratory efficacy (median NAb=129.03 AU/mL; median S-RBD IgG=270.53 AU/mL). The seropositive conversion of NAb reached 94.1% and S-RBD IgG reached 93.3%. Additionally, the S-RBD IgG had very weak correlation with absolute monocyte count (R=-0.185; <i>p</i>-value=0.044). The NAb also had very weak correlation with leukocyte (Kendall’s tau-b (τb)=-0.147; <i>p</i>-value=0.019), absolute neutrophil count (τb=-0.126; <i>p</i>-value=0.044), absolute eosinophil count (τb=-0.132; <i>p</i>-value=0.034).<br /> <b>Conclusion</b>: The seropositivity rate of anti-SARS-CoV-2 NAb and S-RBD IgG were significantly high. However, the CBC derived inflammatory biomarkers had poor correlation with anti-SARS-CoV-2 NAb and S-RBD IgG. Thus, anti-SARS-CoV-2 NAb and S-RBD IgG are currently the only reliable markers for measuring the COVID-19 vaccine efficacy which should be widely accessible.

Serological Cross-Reactivity in Zoonotic Flaviviral Infections of Medical Importance

Flaviviruses are enveloped RNA viruses from the family Flaviviridae that comprise many important human pathogenic arboviruses such as Yellow Fever, Dengue, and Zika viruses. Because they belong to the same genus, these viruses show sequence and structural homology among them, which results in serological cross-reactivity. Upon infection, the immune system produces both species-specific and cross-reactive antibodies, and depending on the virus, in a successive flavivirus infection, cross-reactive antibodies either enhance protection or exacerbate the disease—the latter usually due to antibody-dependent enhancement. These antigenic relationships between different flaviviruses that lead to serological cross-reactivity make them difficult to be identified through serological methods, especially when it comes to successive flavivirus infections. We present here an overview of the main structural, epidemiological, and immunological aspects of flaviviruses, highlighting the role of neutralizing antibodies in fighting viral infections and in the “original antigenic sin” problem. Finally, we draw attention to the importance of developing a rapid serological diagnostic test for flaviviruses with high sensitivity and specificity, especially when considering that cross-reactive immunity can influence the outcome of these infections.

De novo design and Rosetta-based assessment of high-affinity antibody variable regions (Fv) against the SARS-CoV-2 spike receptor binding domain (RBD)

The continued emergence of new SARS-CoV-2 variants has accentuated the growing need for fast and reliable methods for the design of potentially neutralizing antibodies (Abs) to counter immune evasion by the virus. Here, we report on the de novo computational design of high-affinity Ab variable regions (Fv) through the recombination of VDJ genes targeting the most solvent-exposed hACE2-binding residues of the SARS-CoV-2 spike receptor binding domain (RBD) protein using the software tool OptMAVEn-2.0. Subsequently, we carried out computational affinity maturation of the designed variable regions through amino acid substitutions for improved binding with the target epitope. Immunogenicity of designs was restricted by preferring designs that match sequences from a 9-mer library of "human Abs" based on a human string content score. We generated 106 different antibody designs and reported in detail on the top five that trade-off the greatest computational binding affinity for the RBD with human string content scores. We further describe computational evaluation of the top five designs produced by OptMAVEn-2.0 using a Rosetta-based approach. We used Rosetta SnugDock for local docking of the designs to evaluate their potential to bind the spike RBD and performed "forward folding" with DeepAb to assess their potential to fold into the designed structures. Ultimately, our results identified one designed Ab variable region, P1.D1, as a particularly promising candidate for experimental testing. This effort puts forth a computational workflow for the de novo design and evaluation of Abs that can quickly be adapted to target spike epitopes of emerging SARS-CoV-2 variants or other antigenic targets.

Treatment with integrase inhibitors alters SARS-CoV-2 neutralization levels measured with HIV-based pseudotypes in people living with HIV

The presence of neutralizing antibodies (NAbs) is a major correlate of protection for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Thus, different in vitro pseudoviruses-based assays have been described to detect NAbs against SARS-CoV-2. However, the determination of NAbs against SARS-CoV-2 in people living with HIV (PLWH) through HIV-based pseudoparticles could be influenced by cross-neutralization activity or treatment, impeding accurate titration of NAbs. Two assays were compared using replication-defective HIV or VSV-based particles pseudotyped with SARS-CoV-2 spike to measure NAbs in COVID-19-recovered and COVID-19-naïve PLWH. The assay based on HIV-pseudoparticles displayed neutralization activity in all COVID-19-recovered PLWH with a median neutralizing titer 50 (NT50) of 1417.0 (interquartile range [IQR]: 450.3-3284.0), but also in 67% of COVID-19-naïve PLWH (NT50: 631.5, IQR: 16.0-1535.0). Regarding VSV-pseudoparticles system, no neutralization was observed in COVID-19-naïve PLWH as expected, whereas in comparison with HIV-pseudoparticles assay lower neutralization titers were measured in 75% COVID-19-recovered PLWH (NT50: 100.5; IQR: 20.5-1353.0). Treatment with integrase inhibitors was associated with inaccurate increase in neutralization titers when HIV-based pseudoparticles were used. IgG purification and consequent elimination of drugs from samples avoided the interference with retroviral cycle and corrected the lack of specificity observed in HIV-pseudotyped assay. This study shows methodological alternatives based on pseudoviruses systems to determine specific SARS-CoV-2 neutralization titers in PLWH.

Protective roles and protective mechanisms of neutralizing antibodies against SARS-CoV-2 infection and their potential clinical implications

Neutralizing antibodies (NAbs) are central players in the humoral immunity that defends the body from SARS-CoV-2 infection by blocking viral entry into host cells and neutralizing their biological effects. Even though NAbs primarily work by neutralizing viral antigens, on some occasions, they may also combat the SARS-CoV-2 virus escaping neutralization by employing several effector mechanisms in collaboration with immune cells like natural killer (NK) cells and phagocytes. Besides their prophylactic and therapeutic roles, antibodies can be used for COVID-19 diagnosis, severity evaluation, and prognosis assessment in clinical practice. Furthermore, the measurement of NAbs could have key implications in determining individual or herd immunity against SARS-CoV-2, vaccine effectiveness, and duration of the humoral protective response, as well as aiding in the selection of suitable individuals who can donate convalescent plasma to treat infected people. Despite all these clinical applications of NAbs, using them in clinical settings can present some challenges. This review discusses the protective functions, possible protective mechanisms against SARS-CoV-2, and potential clinical applications of NAbs in COVID-19. This article also highlights the possible challenges and solutions associated with COVID-19 antibody-based prophylaxis, therapy, and vaccination.

A Clinical Update on SARS-CoV-2: Pathology and Development of Potential Inhibitors

SARS-CoV-2 (severe acute respiratory syndrome) is highly infectious and causes severe acute respiratory distress syndrome (SARD), immune suppression, and multi-organ failure. For SARS-CoV-2, only supportive treatment options are available, such as oxygen supportive therapy, ventilator support, antibiotics for secondary infections, mineral and fluid treatment, and a significant subset of repurposed effective drugs. Viral targeted inhibitors are the most suitable molecules, such as ACE2 (angiotensin-converting enzyme-2) and RBD (receptor-binding domain) protein-based inhibitors, inhibitors of host proteases, inhibitors of viral proteases 3CLpro (3C-like proteinase) and PLpro (papain-like protease), inhibitors of replicative enzymes, inhibitors of viral attachment of SARS-CoV-2 to the ACE2 receptor and TMPRSS2 (transmembrane serine proteinase 2), inhibitors of HR1 (Heptad Repeat 1)-HR2 (Heptad Repeat 2) interaction at the S2 protein of the coronavirus, etc. Targeting the cathepsin L proteinase, peptide analogues, monoclonal antibodies, and protein chimaeras as RBD inhibitors interferes with the spike protein's ability to fuse to the membrane. Targeting the cathepsin L proteinase, peptide analogues, monoclonal antibodies, and protein chimaeras as RBD inhibitors interferes with the spike protein's ability to fuse to the membrane. Even with the tremendous progress made, creating effective drugs remains difficult. To develop COVID-19 treatment alternatives, clinical studies are examining a variety of therapy categories, including antibodies, antivirals, cell-based therapy, repurposed diagnostic medicines, and more. In this article, we discuss recent clinical updates on SARS-CoV-2 infection, clinical characteristics, diagnosis, immunopathology, the new emergence of variant, SARS-CoV-2, various approaches to drug development and treatment options. The development of therapies has been complicated by the global occurrence of many SARS-CoV-2 mutations. Discussion of this manuscript will provide new insight into drug pathophysiology and drug development.

Immunogenicity of BNT162b2, BBIBP-CorV, Gam-COVID-Vac and ChAdOx1 nCoV-19 Vaccines Six Months after the Second Dose: A Longitudinal Prospective Study

Many available SARS-CoV-2 vaccines demonstrated good humoral response, but studies directly comparing their immunogenicity in the general population are lacking. We evaluated the medium−term kinetics of anti-S SARS-CoV-2 antibodies (Abs) at one and six months after the second dose of BNT162b2, BBIBP-CorV, and Gam-COVID-Vac. Immunogenicity at six months was directly compared between BNT162b2, BBIBP-CorV, Gam-COVID-Vac, and ChAdOx1 nCoV-19. Participants ≥ 20 years old from Novi Sad, Serbia, without prior SARS-CoV-2 infection, were included. Anti S1/S2 IgG antibodies were measured using quantitative LIAISON SARS-CoV-2 assay. A total of 368 participants were included: 231 (62.77%) had sera collected at two time points. Two doses of BNT162b2 were received by 37.50% of participants, followed by BBIBP-CorV (22.01%), Gam-COVID-Vac (21.47%), and ChAdOx1 nCoV-19 (19.02%). Mean Ab levels at the 28th day and 6 months were 216.55 (SD = 105.73) AU/mL and 75.68 (SD = 57.30) for BNT162b2, 194.38 (SD = 140.24) and 90.53 (SD = 111.30) for Gam-COVID-Vac, and 72.74 (SD = 80.04) and 24.43 (SD = 38.43) for BBIBP-CorV group (p < 0.01, between two time points across all three groups), with a significant difference between women and men (p < 0.01, for both sexes). At the sixth month post-vaccination, the highest mean Ab level was detected in Gam-COVID-Vac group (91.28 AU/mL, SD = 95.96), followed by BNT162b2 (85.25 AU/mL, SD = 60.02), ChAdOx1 nCoV-19 (64.22 AU/mL, SD = 65.30), and BBIBP-CorV (25.26 AU/mL, SD = 36.92) (p < 0.01). Anti-spike IgG persistence was demonstrated six months post-vaccination with a significant decline in Ab levels. These results suggest a lower protection against SARS-CoV-2 over time. Our findings support the introduction of additional (booster) doses.

Combined monitoring of IgG and IgA anti-Spike and anti-Receptor binding domain long term responses following BNT162b2 mRNA vaccination in Greek healthcare workers

Studies on the humoral response to homologous BNT162b2 mRNA-vaccination focus mainly on IgG antibody dynamics, while long-term IgA kinetics are understudied. Herein, kinetics of IgG and IgA levels against trimeric-Spike (S) and Receptor-Binding-Domain (RBD) were evaluated by in-house ELISAs in 146 two-dose vaccinated Greek healthcare workers (HCWs) in a 9-month period at six time points (up to 270 days after the first dose). The effect of a homologous booster third dose was also studied and evaluated. The peak of immune response was observed 21 days after the second dose; 100% seroconversion rate for anti-S and anti-RBD IgG, and 99.7% and 96.3% respectively for IgA. IgG antibody levels displayed higher increase compared to IgA. Declining but persistent anti-SARS-CoV-2 antibody levels were detected 9 months after vaccination; IgG and IgA anti-S levels approached those after the first dose, while a more rapid reduction rate for anti-RBD antibodies led to significantly lower levels for both classes, supporting the need for a booster dose. Indeed, a homologous booster third dose resulted in enhanced levels of anti-S of both classes, whereas anti-RBD didn't exceed the peak levels after the second dose. Previous SARS-CoV-2 infection, flu vaccination, BMI<35 and the occurrence of an adverse event upon vaccination, were associated with higher IgG antibody levels over time, which however were negatively affected by age increase and the presence of chronic diseases. Overall, after concurrently using the S and RBD target-antigens in in-house ELISAs, we report in addition to IgG, long-term persistence of IgA antibodies. Regarding antibody levels, homologous mRNA vaccination gives rise to an effective anti-viral protection up to 9 months negatively correlated to age. Considering that COVID-19 is still a matter of public concern, booster vaccine doses remain critical to vulnerable individuals.

Non-neutralizing antibodies: Deleterious or propitious during SARS-CoV-2 infection?

Antibody-dependent enhancement (ADE) is a complex phenomenon mediated by antibodies, frequently pre-existing non-neutralizing or sub-neutralizing antibodies. In the course of infectious diseases, ADE may be responsible for worsening the clinical course of the disease by increasing the virulence of pathogens (ADE of infection) or enhancing disease severity (ADE of disease). Here we reviewed the mechanisms thought to be behind the ADE phenomenon and its potential relationship with COVID-19 severity. Since the early COVID-19 epidemics, ADE has been mentioned as a possible mechanism involved in severe COVID-19 disease and, later, as a potential risk in the case of infection after vaccination. However, current data do not support its role in disease severity, both after infection and reinfection.

Kinetics of severe acute respiratory syndrome coronavirus 2 infection antibody responses

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly throughout the world, causing severe morbidity and mortality. Since the first reports of Coronavirus disease 2019 (COVID-19) in late 2019, research on the characteristics of specific humoral immunity against SARS-CoV-2 in patients with COVID-19 has made great progress. However, our knowledge of persistent humoral immunity to SARS-CoV-2 infection is limited. The existence of protective immunity after infection will affect future transmission and disease severity. Therefore, it is important to gather knowledge about the kinetics of antibody responses. In this review, we summarize the information obtained so far on the characteristics and kinetics of the SARS-CoV-2 infection of specific humoral immune response, especially in neutralizing antibodies and their relationship with disease severity. In addition, with the emergence of variants of concern, we summarize the neutralizing effect of specific humoral immunity on variants of concern after the initial SARS-CoV-2 infection and vaccination.

Adequacy of Hemodialysis Serves as an Independent Predictor of Humoral Response to ChAdOx1 Prime-Boost Vaccination in Hemodialysis Patients

Background: Immune response assessed by the quantification of neutralizing antibodies (nAbs) and predictors associated with immunogenicity after the prime-boost ChAdOx1 (Oxford−AstraZeneca) COVID-19 vaccine in hemodialysis (HD) patients remains unclear. Methods: This prospective study enrolled 174 HD patients and 67 healthy subjects to evaluate antibodies against the spike protein 1 and receptor-binding domain of severe acute respiratory syndrome coronavirus type 2 after prime-booster vaccination, by using enzyme-linked immunosorbent assay and applied spline-based generalized additive model regression analysis to predict 50% neutralization titer (NT50). The correlation between HD parameters and NT50 was analyzed. Results: NT50 was lower in HD patients compared with healthy controls after the prime-boost dose (p < 0.001). The geometric mean titer ratios were higher in first-dose seronegative than in the seropositive subgroup in HD patients and healthy controls (6.96 vs. 2.36, p = 0.002, and 9.28 vs. 1.26, p = 0.011, respectively). After two doses of ChAdOx1, one-way ANOVA showed that Ca × P was positively associated with NT50 (p trend = 0.043) and multiple linear regression showed the similar results (p = 0.021). Kt/V (a quantification of dialysis adequacy) (OR = 20.295, p = 0.005) could independently predict seroconversion (NT50 ≥ 35.13 IU/mL). Conclusion: Adequacy of hemodialysis could independently predict seroconversion in HD subjects vaccinated with prime-boost doses of ChAdOx1.

Neutralization Assessments Reveal High Cardiothoracic Ratio and Old Age as Independent Predictors of Low Neutralizing Antibody Titers in Hemodialysis Patients Receiving a Single Dose of COVID-19 Vaccine

BACKGROUND

Data are lacking regarding predictors of quantification of neutralizing antibodies (nAbs) based on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 50% neutralization titer (NT50) after a single dose of COVID-19 vaccine in hemodialysis (HD) patients.

METHODS

This prospective single-center study enrolled 200 HD patients and 82 healthy subjects to estimate antibodies against the SARS-CoV-2 viral spike protein 1 and receptor-binding domain after a first dose of a COVID-19 vaccine (ChAdOx1 or mRNA-1273), measured by enzyme-linked immunosorbent assay and applied spline-based generalized additive model regression analysis to predict NT50 converted to international units.

RESULTS

After the first dose of ChAdOx1, multiple linear regression showed that age (p = 0.011) and cardiothoracic ratio (p = 0.002) were negatively associated with NT50. Older age (OR = 0.958, p = 0.052) and higher cardiothoracic ratio (OR < 0.001, p = 0.037) could predict negative humoral response (NT50 < 35.13 IU/mL). NT50 was lower in HD patients compared with healthy controls receiving ChAdOx1 (10.68 vs. 43.01 IU/m, p < 0.001) or mRNA-1273 (36.39 vs. 262.2 IU/mL, p < 0.001). ChAdOx1 elicited lower GMTs than mRNA-1273 in the HD cohort (10.68 vs. 36.39 IU/mL, p < 0.001) and in healthy controls (43.01 vs. 262.22 IU/mL, p < 0.001).

CONCLUSION

High cardiothoracic ratio and old age could independently predict a decline in nAb titers in an HD cohort vaccinated with a single dose of ChAdOx1.