Evaluation of the Immune Response Induced by CoronaVac 28-Day Schedule Vaccination in a Healthy Population Group

A quest for universal anti-SARS-CoV-2 T cell assay: systematic review, meta-analysis, and experimental validation

Measuring SARS-CoV-2-specific T cell responses is crucial to understanding an individual's immunity to COVID-19. However, high inter- and intra-assay variability make it difficult to define T cells as a correlate of protection against COVID-19. To address this, we performed systematic review and meta-analysis of 495 datasets from 94 original articles evaluating SARS-CoV-2-specific T cell responses using three assays - Activation Induced Marker (AIM), Intracellular Cytokine Staining (ICS), and Enzyme-Linked Immunospot (ELISPOT), and defined each assay's quantitative range. We validated these ranges using samples from 193 SARS-CoV-2-exposed individuals. Although IFNγ ELISPOT was the preferred assay, our experimental validation suggested that it under-represented the SARS-CoV-2-specific T cell repertoire. Our data indicate that a combination of AIM and ICS or FluoroSpot assay would better represent the frequency, polyfunctionality, and compartmentalization of the antigen-specific T cell responses. Taken together, our results contribute to defining the ranges of antigen-specific T cell assays and propose a choice of assay that can be employed to better understand the cellular immune response against viral diseases.

COVID-19 inactivated and non-replicating viral vector vaccines induce regulatory training phenotype in human monocytes under epigenetic control

Background

Trained immunity is the enhanced innate immune response resulting from exposure to pathogens or vaccines against an unrelated pathogen stimulus. Certain vaccines induce a memory like response in monocytes and NK cells, leading to modulation in cytokine production, metabolic changes, and modifications in histone patterns. Here, we hypothesized that vaccination against SARS-CoV-2 could induce the training of monocytes in addition to stimulating the adaptive immune response.

Methods

Therefore, we aimed to investigate the immunophenotyping, cytokine and metabolic profile of monocytes from individuals who were completely immunized with two doses of inactivated COVID-19 vaccine or non-replicating viral vector vaccine. Subsequently, we investigated the epigenetic mechanisms underlying monocyte immune training. As a model of inflammatorychallenge, to understand if the monocytes were trained by vaccination and how they were trained, cells were stimulated in vitro with the endotoxin LPS, an unrelated stimulus that would provoke the effects of training.

Results

When challenged in vitro, monocytes from vaccinated individuals produced less TNF-α and those who received inactivated vaccine produced less IL-6, whereas vaccination with non-replicating viral vector vaccine induced more IL-10. Inactivated vaccine increased classical monocyte frequency, and both groups showed higher CD163 expression, a hallmark of trained immunity. We observed increased expression of genes involved in glycolysis and reduced IRG1 expression in vaccinated subjects, a gene associated with the tolerance phenotype in monocytes. We observed that both vaccines reduced the chromatin accessibility of genes associated with the inflammatory response, the inactivated COVID-19 vaccine trained monocytes to a regulatory phenotype mediated by histone modifications in the IL6 and IL10 genes, while the non-replicating viral vector COVID-19 vaccine trained monocytes to a regulatory phenotype, mediated by histone modifications in the IL6, IL10, TNF, and CCL2 genes.

Conclusions

Our findings support the recognized importance of adopting vaccination against SARS CoV-2, which has been shown to be effective in enhancing the adaptive immune response against the virus and reducing mortality and morbidity rates. Here, we provide evidence that vaccination also modulates the innate immune response by controlling the detrimental inflammatory response to unrelated pathogen stimulation.

Metabolic Adaptations Correlated with Antibody Response after Immunization with Inactivated SARS-CoV-2 in Brazilian Subjects

The adsorbed vaccine SARS-CoV-2 (inactivated) produced by Sinovac (SV) was the first vaccine against COVID-19 to be used in Brazil. To understand the metabolic effects of SV in Brazilian subjects, NMR-based metabolomics was used, and the immune response was studied in Brazilian subjects. Forty adults without (group^-, n = 23) and with previous COVID-19 infection (group⁺, n = 17) were followed-up for 90 days postcompletion of the vaccine regimen. After 90 days, our results showed that subjects had increased levels of lipoproteins, lipids, and N-acetylation of glycoproteins (NAG) as well as decreased levels of amino acids, lactate, citrate, and 3-hydroxypropionate. NAG and threonine were the highest correlated metabolites with N and S proteins, and neutralizing Ab levels. This study sheds light on the immunometabolism associated with the use of SV in Brazilian subjects from Rio de Janeiro and identifies potential metabolic markers associated with the immune status.

Cellular and Humoral Immune Responses to Vaccination for COVID-19 Are Negatively Impacted by Senescent T Cells: A Case Report

BACKGROUND

Herein, we aimed to follow up on the cellular and humoral immune responses of a group of individuals who initially received the CoronaVac vaccine, followed by a booster with the Pfizer vaccine.

METHODS

Blood samples were collected: before and 30 days after the first CoronaVac dose; 30, 90, and 180 days after the second CoronaVac dose, and also 20 days after the booster with the Pfizer vaccine.

RESULTS

Whilst the positivity to gamma interferon-type cellular response increased after the first CoronaVac dose, neutralizing and IgG antibody levels only raised 30 days after the second dose, followed by a drop in these responses after 90 and 180 days. The booster with the Pfizer vaccine elicited a robust cellular and humoral response. A higher number of double-negative and senescent T cells, as well as increased pro-inflammatory cytokines levels were found in the participants with lower humoral immune responses.

CONCLUSION

CoronaVac elicited an early cellular response, followed by a humoral response, which dropped 90 days after the second dose. The booster with the Pfizer vaccine significantly enhanced these responses. Furthermore, a pro-inflammatory systemic status was found in volunteers who presented senescent T cells, which could putatively impair the immune response to vaccination.

Assessment of Reactivity to the Administration of the mRNA Vaccine after Six Months of Observation

BACKGROUND

The fast spread of the SARS-CoV-2 virus accelerated efforts to create an effective vaccine, and a novel mRNA vaccine was the first to appear effective. Scientific evidence regarding mRNA vaccination is limited; therefore, understanding how the immune system responds to an mRNA vaccine is critical. Our study was aimed at a long-term analysis of the presence and maintenance of the immune response using the chemiluminescent method by analyzing the level of IgG antibodies in vaccinated people who were and were not infected with the SARS-CoV-2 virus.

MATERIALS AND METHODS

Healthcare workers with a history of COVID-19 or who were naïve to the infection were recruited for this study and administered two subsequent doses of the Comirnaty vaccine. IgG SRBD antibody levels were evaluated every month for six consecutive months using the chemiluminescent immunoassay (CLIA).

RESULTS

A total of 149 individuals were recruited for this study, 68 had evidence of past COVID-19 infection, with 63 exhibiting elevated IgG SRBD antibody levels at initial evaluation. Statistically significant differences were observed between COVID-19 convalescents and non-convalescents at all study time points, with the convalescent group consequently representing higher antibody levels.

CONCLUSIONS

COVID-19 convalescents showed a stronger immune response to the vaccine after the first dose. This group exhibited higher IgG levels in all examinations during the observation period. The natural waning of antibody levels can be observed within six months. A booster vaccination may be required. No serious side effects were observed.

Evaluation and comparison of the sensitivity of three commercial RT-qPCR kits used for the detection of SARS-CoV-2 in Santiago, Chile

Introduction

The COVID-19 pandemic is still in force, causing global public health challenges and threats. Although vaccination and herd immunity have proven to be the most efficient way to control the pandemic, massive and early testing of patients using the RT-qPCR technique is crucial for constant genomic surveillance. The appearance of variants of SARS-CoV-2 with new mutations can reduce the efficiency of diagnostic detection. In this sense, several commercial RT-qPCR kits have been the target of extensive analysis because low assay performance could lead to false-negative diagnoses.

Methods

In this study, we evaluated the performance of three commercial RT-qPCR kits; Thermo Fisher (TaqMan 2019-nCoV Assay Kit v1), BGI and Roche (LightCycler^® Multiplex RNA Virus Master) used for the diagnosis of COVID-19 throughout the pandemic in Santiago de Chile.

Results

Under our best assay conditions, we found significant differences in Cq amplification values for control and viral probes, against the same nasopharyngeal swab samples (NPSs). In addition, in some cases, the sensitivity of the RT-qPCR kits decreased against viral variants.

Conclusion

Our study suggests evaluating the RT-qPCR kits used to detect SARS-CoV-2 because variants such as Omicron, which has several mutations, can compromise their detection and underestimate viral circulation.

IgA quantification as a good predictor of the neutralizing antibodies levels after vaccination against SARS-CoV-2

Background

Vaccination against COVID-19 was implemented very quickly, but the emergence of new variants that can evade the previous acquired immunological protection highlights the importance of understanding the mechanisms involved in the immune response generated after SARS-CoV-2 infection or vaccination.

Objectives

Since most of our knowledge on the humoral immunity generated against SARS-CoV-2 has been obtained from studies with infected patients before vaccination, our goal here was to evaluate seroconversion and its correlation with the titers of neutralizing antibodies (NAbs) in individuals who received the complete initial recommended vaccination schedule with three different vaccines.

Study design

We analyzed serum IgG, IgA and total NAbs against the trimeric SARS-CoV-2 Spike (S) protein or its receptor binding domain (RBD) in blood samples collected from 118 healthy individuals without known previous infection, before and after receiving the first and the second dose of CoronaVac (n = 18), ChAdOx-1 (n = 68) or BNT162b2 (n = 32) vaccines.

Results

We found that although IgG titers were high in all sera collected after the two doses of these vaccines, NAbs amounts varies among the groups. In contrast, serum NAbs concentrations were much more comparable to the IgA levels, indicating that these antibodies would have a major neutralizing capacity against SARS-CoV-2.

Conclusions

Altogether our data suggest that quantification of serum anti-S or anti-RBD IgA, rather than IgG, may be a valuable tool to screen NAbs and may be considered for surveillance of vaccine coverage.

Vaccines against SARS-CoV-2 variants and future pandemics

INTRODUCTION

Vaccination continues to be the most effective method for controlling COVID-19 infectious diseases. Nonetheless, SARS-CoV-2 variants continue to evolve and emerge, resulting in significant public concerns worldwide, even after more than 2 years since the COVID-19 pandemic. It is important to better understand how different COVID-19 vaccine platforms work, why SARS-CoV-2 variants continue to emerge, and what options for improving COVID-19 vaccines can be considered to fight against SARS-CoV-2 variants and future pandemics.

AREA COVERED

Here, we reviewed the innate immune sensors in the recognition of SARS-CoV-2 virus, innate and adaptive immunity including neutralizing antibodies by different COVID-19 vaccines. Efficacy comparison of the several COVID-19 vaccine platforms approved for use in humans, concerns about SARS-CoV-2 variants and breakthrough infections, and the options for developing future COIVD-19 vaccines were also covered.

EXPERT OPINION

Owing to the continuous emergence of novel pathogens and the reemergence of variants, safer and more effective new vaccines are needed. This review also aims to provide the knowledge basis for the development of next-generation COVID-19 and pan-coronavirus vaccines to provide cross-protection against new SARS-CoV-2 variants and future coronavirus pandemics.

Comparison of Anti-SARS-CoV-2 IgG Antibody Responses Generated by the Administration of Ad26.COV2.S, AZD1222, BNT162b2, or CoronaVac: Longitudinal Prospective Cohort Study in the Colombian Population, 2021/2022

To mitigate the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), vaccines have been rapidly developed and introduced in many countries. In Colombia, the population was vaccinated with four vaccines. Therefore, this research aimed to determine the ability of the vaccines introduced in the National Vaccination Plan to prevent SARS-CoV-2 infection and induce seroconversion and sought to investigate the longevity of antibodies in the blood. We conducted a prospective, nonprobabilistic, consecutive cross-sectional cohort study in a population with access to vaccination with CoronaVac, Ad26.COV2.S, AZD1222, and BNT162b2 from March 2021 to March 2022. The study included 1327 vaccinated people. A plurality of participants were vaccinated with BNT162b2 (36.1%; n = 480), followed by Ad26.COV2.S (26.9%; n = 358), CoronaVac (24%; n = 331), and AZD1222 (11.9%; n = 158). The crude seroprevalence on day zero varied between 18.1% and 57.8%. Participants who received BNT162b2 had a lower risk of SARS-CoV-2 infection than those who received the other vaccines. Participants who were immunized with BNT162b2 and AZD1222 had a higher probability of losing reactivity on day 210 after receiving the vaccine.

A Booster Dose of CoronaVac Increases Neutralizing Antibodies and T Cells that Recognize Delta and Omicron Variants of Concern

CoronaVac is an inactivated SARS-CoV-2 vaccine approved by the World Health Organization (WHO). Previous studies reported increased levels of neutralizing antibodies and specific T cells 2 and 4 weeks after two doses of CoronaVac; these levels were significantly reduced at 6 to 8 months after the two doses. Here, we report the effect of a booster dose of CoronaVac on the anti-SARS-CoV-2 immune response generated against the variants of concern (VOCs), Delta and Omicron, in adults participating in a phase III clinical trial in Chile. Volunteers immunized with two doses of CoronaVac in a 4-week interval received a booster dose of the same vaccine between 24 and 30 weeks after the second dose. Neutralization capacities and T cell activation against VOCs Delta and Omicron were assessed 4 weeks after the booster dose. We observed a significant increase in neutralizing antibodies 4 weeks after the booster dose. We also observed a rise in anti-SARS-CoV-2-specific CD4⁺ T cells over time, and these cells reached a peak 4 weeks after the booster dose. Furthermore, neutralizing antibodies and SARS-CoV-2-specific T cells induced by the booster showed activity against VOCs Delta and Omicron. Our results show that a booster dose of CoronaVac increases adults’ humoral and cellular anti-SARS-CoV-2 immune responses. In addition, immunity induced by a booster dose of CoronaVac is active against VOCs, suggesting adequate protection.