Single-dose SARS-CoV-2 vaccinations with either BNT162b2 or AZD1222 induce disparate Th1 responses and IgA production

An insight into COVID-19 host immunity at single-cell resolution

Host immunity helps the body to fight against COVID-19. Single-cell transcriptomics has provided the scope of investigating cellular and molecular underpinnings of host immune response against SARS-CoV-2 infection at high resolution. In this review, we have systematically described the virus-induced dysregulation of relative abundance as well as molecular behavior of each innate and adaptive immune cell type and cell state during COVID-19 infection and for different vaccinations, based on single-cell studies published in last three-four years. Identification and characterization of these disease-associated specific cell populations might help to design better, efficient, and targeted therapeutic avenues.

The BNT162b2 mRNA vaccine demonstrates reduced age-associated TH1 support in vitro and in vivo

mRNA vaccines demonstrate impaired immunogenicity and durability in vulnerable older populations. We hypothesized that human in vitro modeling and proteomics could elucidate age-specific mRNA vaccine actions. BNT162b2-stimulation changed the plasma proteome of blood samples from young (18-50Y) and older adult (≥60Y) participants, assessed by mass spectrometry, proximity extension assay, and multiplex. Young adult up-regulation (e.g., PSMC6, CPN1) contrasted reduced induction in older adults (e.g., TPM4, APOF, APOC2, CPN1, PI16). 30-85% lower TH1-polarizing cytokines and chemokines were induced in elderly blood (e.g., IFNγ, CXCL10). Analytes lower in older adult samples included human in vivo mRNA immunogenicity biomarkers (e.g., IFNγ, CXCL10, CCL4, IL-1RA). BNT162b2 also demonstrated reduced CD4+ TH1 responses in aged vs. young adult mice. Our study demonstrates the utility of human in vitro platforms modeling age-specific mRNA vaccine immunogenicity, highlights impaired support of TH1 polarization in older adults, and provides a rationale for precision mRNA vaccine adjuvantation to induce greater immunogenicity.

Memory B cell proliferation drives differences in neutralising responses between ChAdOx1 and BNT162b2 SARS-CoV-2 vaccines

Vaccination against COVID-19 has been pivotal in reducing the global burden of the disease. However, Phase III trial results and observational studies underscore differences in efficacy across vaccine technologies and dosing regimens. Notably, mRNA vaccines have exhibited superior effectiveness compared to Adenovirus (AdV) vaccines, especially with extended dosing intervals. Using in-host mechanistic modelling, this study elucidates these variations and unravels the biological mechanisms shaping the immune responses at the cellular level. We used data on the change in memory B cells, plasmablasts, and antibody titres after the second dose of a COVID-19 vaccine for Australian healthcare workers. Alongside this dataset, we constructed a kinetic model of humoral immunity which jointly captured the dynamics of multiple immune markers, and integrated hierarchical effects into this kinetics model, including age, dosing schedule, and vaccine type. Our analysis estimated that mRNA vaccines induced 2.1 times higher memory B cell proliferation than AdV vaccines after adjusting for age, interval between doses and priming dose. Additionally, extending the duration between the second vaccine dose and priming dose beyond 28 days boosted neutralising antibody production per plasmablast concentration by 30%. We also found that antibody responses after the second dose were more persistent when mRNA vaccines were used over AdV vaccines and for longer dosing regimens. Reconstructing in-host kinetics in response to vaccination could help optimise vaccine dosing regimens, improve vaccine efficacy in different population groups, and inform the design of future vaccines for enhanced protection against emerging pathogens.

The varying extent of humoral and cellular immune responses to either vector- or RNA-based SARS-CoV-2 vaccines persists for at least 18 months and is independent of infection

The corona virus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome corona-virus 2 (SARS-CoV-2) spurred a worldwide race for the development of an efficient vaccine. Various strategies were pursued; however, the first vaccines to be licensed presented the SARS-CoV-2 spike protein either in the context of a non-replicating adenoviral vector or as an mRNA construct. While short-term efficacies have extensively been characterized, the duration of protection, the need for repeated boosting, and reasonable vaccination intervals have yet to be defined. We here describe the adaptive immune response resulting from homologous and heterologous vaccination regimen at 18 months after primary vaccination. To that extent, we monitored 176 healthcare workers, the majority of whom had recovered from previous SARS-CoV-2 infection. In summary, we find that differences depending on primary immunization continue to exist 18 months after the first vaccination and these findings hold true irrespective of previous infection with the virus. Homologous primary immunization with BNT162b2 was repeatedly shown to produce higher antibody levels and slower antibody decline, leading to more effective in vitro neutralization capacities. Likewise, cellular responses resulting from in vitro re-stimulation were more pronounced after primary immunization involving BNT162b2. In contrast, IL-2 producing memory T helper and cytotoxic T cells appeared independent from the primary vaccination regimen. Despite these differences, comparable infection rates among all vaccination groups suggest comparable real-life protection.IMPORTANCEVaccination against the severe acute respiratory syndrome corona-virus 2 (SARS-CoV-2) was shown to avert severe courses of corona virus disease 2019 (COVID-19) and to mitigate spreading of the virus. However, the duration of protection and need for repeated boosting have yet to be defined. Monitoring and comparing the immune responses resulting from various vaccine strategies are therefore important to fill knowledge gaps and prepare for future pandemics.

NVX-CoV2373 induces humoral and cellular immune responses that are functionally comparable to vector and mRNA-based vaccines

Background

After licensing of the protein-based vaccine NVX-CoV2373, three technically different vaccines against the SARS-CoV-2 became available for application to the human population - and for comparison of efficacies.

Methods

We here recruited 42 study participants who had obtained one initial dose of NVX-CoV2373 and analyzed their immune responses in contrast to 37 study participants who had obtained either the vector vaccine AZD1222 or the mRNA vaccine BNT162b2 a year earlier. 32 participants also donated blood before first vaccination to serve as a vaccine-naive control. In detail, we investigated and quantified at day 21 and approximately six months after primary immunization the amounts of vaccine-specific antibodies produced, their neutralization capacity, their quality in terms of binding different epitopes and their efficiency in inducing various isotypes. Cellular immunity and intracellular cytokine production following in vitro re-stimulation with BNT162b2 vaccine was analyzed via ELISpot or via flow cytometry.

Results

Our results show that even though vaccination including the mRNA vaccine yielded best results in almost any aspect of antibody levels and binding efficiency, the neutralization capacities against the wild-type Wuhan strain and the Omicron BA.1 variant early and at six months were comparable among all three vaccination groups. As for the T cells, we observed a prevailing CD8 response at three weeks which turned into a predominant CD4 memory at six months which has not yet been observed for AZD1222 and BNT162b2. While additional infection with SARS-CoV-2 resulted in a boost for the humoral response, T cell memory appeared rather unaffected.

Conclusion

Whether any of these differences translate into real world protection from infection, mitigation of severe disease courses and prevention of long/post COVID will need to be investigated in the future.

To be remembered: B cell memory response against SARS-CoV-2 and its variants in vaccinated and unvaccinated individuals

COVID-19 disease has plagued the world economy and affected the overall well-being and life of most of the people. Natural infection as well as vaccination leads to the development of an immune response against the pathogen. This involves the production of antibodies, which can neutralize the virus during future challenges. In addition, the development of cellular immune memory with memory B and T cells provides long-lasting protection. The longevity of the immune response has been a subject of intensive research in this field. The extent of immunity conferred by different forms of vaccination or natural infections remained debatable for long. Hence, understanding the effectiveness of these responses among different groups of people can assist government organizations in making informed policy decisions. In this article, based on the publicly available data, we have reviewed the memory response generated by some of the vaccines against SARS-CoV-2 and its variants, particularly B cell memory in different groups of individuals.

Immunoglobulin A response to SARS-CoV-2 infection and immunity

The novel coronavirus disease (COVID-19) and its infamous "Variants" of the etiological agent termed Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) has proven to be a global health concern. The three antibodies, IgA, IgM, and IgG, perform their dedicated role as main workhorses of the host adaptive immune system in virus neutralization. Immunoglobulin-A (IgA), also known as "Mucosal Immunoglobulin", has been under keen interest throughout the viral infection cycle. Its importance lies because IgA is predominant mucosal antibody and SARS family viruses primarily infect the mucosal surfaces of human respiratory tract. Therefore, IgA can be considered a diagnostic and prognostic marker and an active infection biomarker for SARS CoV-2 infection. Along with molecular analyses, serological tests, including IgA detection tests, are gaining ground in application as an early detectable marker and as a minimally invasive detection strategy. In the current review, it was emphasized the role of IgA response in diagnosis, host defense strategies, treatment, and prevention of SARS-CoV-2 infection. The data analysis was performed through almost 100 published peer-reviewed research reports and comprehended the importance of IgA in antiviral immunity against SARS-CoV-2 and other related respiratory viruses. Taken together, it is concluded that secretory IgA- Abs can serve as a promising detection tool for respiratory viral diagnosis and treatment parallel to IgG-based therapeutics and diagnostics. Vaccine candidates that target and trigger mucosal immune response may also be employed in future dimensions of research against other respiratory viruses.

Polyfunctional CD4 T-cells correlating with neutralising antibody is a hallmark of COVISHIELDTM and COVAXIN® induced immunity in COVID-19 exposed Indians

Detailed characterisation of immune responses induced by COVID-19 vaccines rolled out in India: COVISHIELDTM (CS) and COVAXIN® (CO) in a pre-exposed population is only recently being discovered. We addressed this issue in subjects who received their primary series of vaccination between November 2021 and January 2022. Both vaccines are capable of strongly boosting Wuhan Spike-specific neutralising antibody, polyfunctional Th1 cytokine producing CD4+ T-cells and single IFN-γ + CD8+ T-cells. Consistent with inherent differences in vaccine platform, the vector-based CS vaccine-induced immunity was of greater magnitude, breadth, targeting Delta and Omicron variants compared to the whole-virion inactivated vaccine CO, with CS vaccinees showing persistent CD8+ T-cells responses until 3 months post primary vaccination. This study provides detailed evidence on the magnitude and quality of CS and CO vaccine induced responses in subjects with pre-existing SARS-CoV-2 immunity in India, thereby mitigating vaccine hesitancy arguments in such a population, which remains a global health challenge.

Aerosol Inhalation of Chimpanzee Adenovirus Vectors (ChAd68) Expressing Ancestral or Omicron BA.1 Stabilized Pre-Fusion Spike Glycoproteins Protects Non-Human Primates against SARS-CoV-2 Infection

Current COVID-19 vaccines are effective countermeasures to control the SARS-CoV-2 virus pandemic by inducing systemic immune responses through intramuscular injection. However, respiratory mucosal immunization will be needed to elicit local sterilizing immunity to prevent virus replication in the nasopharynx, shedding, and transmission. In this study, we first compared the immunoprotective ability of a chimpanzee replication-deficient adenovirus-vectored COVID-19 vaccine expressing a stabilized pre-fusion spike glycoprotein from the ancestral SARS-CoV-2 strain Wuhan-Hu-1 (BV-AdCoV-1) administered through either aerosol inhalation, intranasal spray, or intramuscular injection in cynomolgus monkeys and rhesus macaques. Compared with intranasal administration, aerosol inhalation of BV-AdCoV-1 elicited stronger humoral and mucosal immunity that conferred excellent protection against SARS-CoV-2 infection in rhesus macaques. Importantly, aerosol inhalation induced immunity comparable to that obtained by intramuscular injection, although at a significantly lower dose. Furthermore, to address the problem of immune escape variants, we evaluated the merits of heterologous boosting with an adenovirus-based Omicron BA.1 vaccine (C68-COA04). Boosting rhesus macaques vaccinated with two doses of BV-AdCoV-1 with either the homologous or the heterologous C68-COA04 vector resulted in cross-neutralizing immunity against WT, Delta, and Omicron subvariants, including BA.4/5 stronger than that obtained by administering a bivalent BV-AdCoV-1/C68-COA04 vaccine. These results demonstrate that the administration of BV-AdCoV-1 or C68-COA04 via aerosol inhalation is a promising approach to prevent SARS-CoV-2 infection and transmission and curtail the pandemic spread.

T-cell immunity to SARS-CoV-2: what if the known best is not the optimal course for the long run? Adapting to evolving targets

Humanity did surprisingly well so far, considering how unprepared it was to respond to the coronavirus disease 2019 (COVID-19) threat. By blending old and ingenious new technology in the context of the accumulated knowledge on other human coronaviruses, several vaccine candidates were produced and tested in clinical trials in record time. Today, five vaccines account for the bulk of the more than 13 billion doses administered worldwide. The ability to elicit biding and neutralizing antibodies most often against the spike protein is a major component of the protection conferred by immunization but alone it is not enough to limit virus transmission. Thus, the surge in numbers of infected individuals by newer variants of concern (VOCs) was not accompanied by a proportional increase in severe disease and death rate. This is likely due to antiviral T-cell responses, whose evasion is more difficult to achieve. The present review helps navigating the very large literature on T cell immunity induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination. We examine the successes and shortcomings of the vaccinal protection in the light of the emergence of VOCs with breakthrough potential. SARS-CoV-2 and human beings will likely coexist for a long while: it will be necessary to update existing vaccines to improve T-cell responses and attain better protection against COVID-19.

A linear B-cell epitope close to the furin cleavage site within the S1 domain of SARS-CoV-2 Spike protein discriminates the humoral immune response of nucleic acid- and protein-based vaccine cohorts

Background

Understanding the humoral immune response towards viral infection and vaccination is instrumental in developing therapeutic tools to fight and restrict the viral spread of global pandemics. Of particular interest are the specificity and breadth of antibody reactivity in order to pinpoint immune dominant epitopes that remain immutable in viral variants.

Methods

We used profiling with peptides derived from the Spike surface glycoprotein of SARS-CoV-2 to compare the antibody reactivity landscapes between patients and different vaccine cohorts. Initial screening was done with peptide microarrays while detailed results and validation data were obtained using peptide ELISA.

Results

Overall, antibody patterns turned out to be individually distinct. However, plasma samples of patients conspicuously recognized epitopes covering the fusion peptide region and the connector domain of Spike S2. Both regions are evolutionarily conserved and are targets of antibodies that were shown to inhibit viral infection. Among vaccinees, we discovered an invariant Spike region (amino acids 657-671) N-terminal to the furin cleavage site that elicited a significantly stronger antibody response in AZD1222- and BNT162b2- compared to NVX-CoV2373-vaccinees.

Conclusions

Understanding the exact function of antibodies recognizing amino acid region 657-671 of SARS-CoV-2 Spike glycoprotein and why nucleic acid-based vaccines elicit different responses from protein-based ones will be helpful for future vaccine design.

An Immunological Review of SARS-CoV-2 Infection and Vaccine Serology: Innate and Adaptive Responses to mRNA, Adenovirus, Inactivated and Protein Subunit Vaccines

The coronavirus disease 2019 (COVID-19) pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, which is defined by its positive-sense single-stranded RNA (ssRNA) structure. It is in the order Nidovirales, suborder Coronaviridae, genus Betacoronavirus, and sub-genus Sarbecovirus (lineage B), together with two bat-derived strains with a 96% genomic homology with other bat coronaviruses (BatCoVand RaTG13). Thus far, two Alphacoronavirus strains, HCoV-229E and HCoV-NL63, along with five Betacoronaviruses, HCoV-HKU1, HCoV-OC43, SARS-CoV, MERS-CoV, and SARS-CoV-2, have been recognized as human coronaviruses (HCoVs). SARS-CoV-2 has resulted in more than six million deaths worldwide since late 2019. The appearance of this novel virus is defined by its high and variable transmission rate (RT) and coexisting asymptomatic and symptomatic propagation within and across animal populations, which has a longer-lasting impact. Most current therapeutic methods aim to reduce the severity of COVID-19 hospitalization and virus symptoms, preventing the infection from progressing from acute to chronic in vulnerable populations. Now, pharmacological interventions including vaccines and others exist, with research ongoing. The only ethical approach to developing herd immunity is to develop and provide vaccines and therapeutics that can potentially improve on the innate and adaptive system responses at the same time. Therefore, several vaccines have been developed to provide acquired immunity to SARS-CoV-2 induced COVID-19-disease. The initial evaluations of the COVID-19 vaccines began in around 2020, followed by clinical trials carried out during the pandemic with ongoing population adverse effect monitoring by respective regulatory agencies. Therefore, durability and immunity provided by current vaccines requires further characterization with more extensive available data, as is presented in this paper. When utilized globally, these vaccines may create an unidentified pattern of antibody responses or memory B and T cell responses that need to be further researched, some of which can now be compared within laboratory and population studies here. Several COVID-19 vaccine immunogens have been presented in clinical trials to assess their safety and efficacy, inducing cellular antibody production through cellular B and T cell interactions that protect against infection. This response is defined by virus-specific antibodies (anti-N or anti-S antibodies), with B and T cell characterization undergoing extensive research. In this article, we review four types of contemporary COVID-19 vaccines, comparing their antibody profiles and cellular aspects involved in coronavirus immunology across several population studies.

Adaptive immune responses and cytokine immune profiles in humans following prime and boost vaccination with the SARS-CoV-2 CoronaVac vaccine

BACKGROUND

Adaptive immune response has been thought to play a key role in SARS-CoV-2 infection. The role of B cells, CD4+T, and CD8+T cells are different in vaccine-induced immune response, thus it is imperative to explore the functions and kinetics of adaptive immune response. We collected blood samples from unvaccinated and vaccinated individuals. To assess the mechanisms contributing to protective immunity of CoronaVac vaccines, we mapped the kinetics and durability of humoral and cellular immune responses after primary and boost vaccination with CoronaVac vaccine in different timepoints.

MATERIALS AND METHODS

We separate PBMC and plasma from blood samples. The differentiation and function of RBD-spcific CD4+T and CD8+T cells were analyzed by flow cytometry and ELISA. Antibodies response was analyzed by ELISA. ELISPOT analysis was perfomed to detected the RBD-spcific memory B cells. CBA analysis was performed to detected the cytokine immune profiles. Graphpad prism 8 and Origin 2021 were used for statistical analysis.

RESULTS

Vaccine-induced CD4+T cell responses to RBD were more prominent than CD8+T cell responses, and characterized by a predominant Th1 and weak Th17 helper response. CoronaVac vaccine triggered predominant IgG1 antibody response and effectively recalled specific antibodies to RBD protein after booster vaccination. Robust antigen-specific memory B cells were detected (p < 0.0001) following booster vaccination and maintained at 6 months (p < 0.0001) following primary vaccination. Vaccine-induced CD4+T cells correlated with CD8+T cells (r = 0.7147, 0.3258, p < 0.0001, p = 0.04), memory B cell responses (r = 0.7083, p < 0.0001), and IgG and IgA (r = 0.6168, 0.5519, p = 0.0006, 0.003) after vaccination. In addition, vaccine induced a broader and complex cytokine pattern in plasma at early stage.

CONCLUSION

Taken together, these results highlight the potential role of B cell and T cell responses in vaccine-induced long-term immunity.

The mRNA vaccine BNT162b2 demonstrates impaired TH1 immunogenicity in human elders in vitro and aged mice in vivo

mRNA vaccines have been key to addressing the SARS-CoV-2 pandemic but have impaired immunogenicity and durability in vulnerable older populations. We evaluated the mRNA vaccine BNT162b2 in human in vitro whole blood assays with supernatants from adult (18-50 years) and elder (≥60 years) participants measured by mass spectrometry and proximity extension assay proteomics. BNT162b2 induced increased expression of soluble proteins in adult blood (e.g., C1S, PSMC6, CPN1), but demonstrated reduced proteins in elder blood (e.g., TPM4, APOF, APOC2, CPN1, and PI16), including 30-85% lower induction of TH1-polarizing cytokines and chemokines (e.g., IFNγ, and CXCL10). Elder TH1 impairment was validated in mice in vivo and associated with impaired humoral and cellular immunogenicity. Our study demonstrates the utility of a human in vitro platform to model age-specific mRNA vaccine activity, highlights impaired TH1 immunogenicity in older adults, and provides rationale for developing enhanced mRNA vaccines with greater immunogenicity in vulnerable populations.

COVID-19 Vaccination Is Associated with a Better Outcome in Acute Ischemic Stroke Patients: A Retrospective Observational Study

Background: It is unclear whether and how COVID-19 vaccination may affect the outcome of patients with acute ischemic stroke (AIS). We investigated this potential association in a retrospective study by comparing previously vaccinated (VAX) versus unvaccinated (NoVAX) stroke patients. Methods: We collected clinical reports for all consecutive AIS patients admitted to our hospital and evaluated the outcome predictors in VAX and NoVAX groups. Adjustments were made for possible confounders in multivariable logistic regression analysis, and adjusted hazard ratios were calculated. Results: A total of 466 AIS patients (287 VAX and 179 NoVAX) were included in this study. The NIHSS score at discharge and mRS score at a 3-month follow-up visit were significantly lower in VAX patients compared to NoVAX patients (p < 0.001). Good outcomes (mRS 0−2) were significantly associated with COVID-19 vaccination before AIS (adjusted hazard ratio, 0.400 [95% CI = 0.216−0.741]). Conclusions: The observation that COVID-19 vaccination can influence the outcome of AIS provides support for further studies investigating the role of immunity in ischemic brain damage.

Antibody response 6 months after the booster dose of Pfizer in previous recipients of CoronaVac

The most widely used vaccines were messenger RNA (mRNA), viral vector, and inactivated virus with two-dose schedules. In Brazil, the CoronaVac (Sinovac) was the first vaccine approved for emergency use, and the third dose was administered, preferably, with the BNT162b2 vaccine. We evaluated antibody levels after 6 months of the booster dose with BNT162B2 in previous recipients of CoronaVac and whether a subsequent severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) infection enhances the antibody response. We analyze the humoral response (spike [S] IgM for the SARS-CoV-2 and IgG for the S and nucleocapsid [N] proteins) in samples collected before the third dose and 6 months after the third dose. The presence of antibodies was measured by using Abbott Architect i2000SR. The IgM and IgG antispikes were stimulated mainly 30 days after the third dose (30d/3D), with a decline over time. The IgG anti-N was stimulated predominantly in 90d/3D and 180d/3D. The N IgG levels were 50 and 35 times higher in the positive polymerase chain reaction (PCR) group in 90d/3D and 180d/3D, respectively. The S IgG titers were 1.5 times elevated in the positive PCR group, in 180d/3D. The BNT162b2 boosted the S IgG levels, decreasing after 60 days. The booster shot induced IgM and IgG antibodies against spike protein. Infection after vaccination increased antibodies against protein N.

Single-cell sequencing of PBMC characterizes the altered transcriptomic landscape of classical monocytes in BNT162b2-induced myocarditis

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been the most dangerous threat to public health worldwide for the last few years, which led to the development of the novel mRNA vaccine (BNT162b2). However, BNT162b2 vaccination is known to be associated with myocarditis. Here, as an attempt to determine the pathogenesis of the disease and to develop biomarkers to determine whether subjects likely proceed to myocarditis after vaccination, we conducted a time series analysis of peripheral blood mononuclear cells of a patient with BNT162b2-induced myocarditis. Single-cell RNA sequence analysis identified monocytes as the cell clusters with the most dynamic changes. To identify distinct gene expression signatures, we compared monocytes of BNT162b2-induced myocarditis with monocytes under various conditions, including SARS-CoV-2 infection, BNT162b2 vaccination, and Kawasaki disease, a disease similar to myocarditis. Representative changes in the transcriptomic profile of classical monocytes include the upregulation of genes related to fatty acid metabolism and downregulation of transcription factor AP-1 activity. This study provides, for the first time, the importance of classical monocytes in the pathogenesis of myocarditis following BNT162b2 vaccination and presents the possibility that vaccination affects monocytes, further inducing their differentiation and infiltration into the heart.

Vaccine-Induced T-Cell and Antibody Responses at 12 Months after Full Vaccination Differ with Respect to Omicron Recognition

More than a year after the first vaccines against the novel SARS-CoV-2 were approved, many questions still remain about the long-term protection conferred by each vaccine. How long the effect lasts, how effective it is against variants of concern and whether further vaccinations will confer additional benefits remain part of current and future research. For this purpose, we examined 182 health care employees-some of them with previous SARS-CoV-2 infection-12 months after different primary immunizations. To assess antibody responses, we performed an electrochemiluminescence assay (ECLIA) to determine anti-spike IgGs, followed by a surrogate virus neutralization assay against Wuhan-Hu-1 and B.1.1.529/BA.1 (Omicron). T cell response against wild-type and the Omicron variants of concern were assessed via interferon-gamma ELISpot assays and T-cell surface and intracellular cytokine staining. In summary, our results show that after the third vaccination with an mRNA vaccine, differences in antibody quantity and functionality observed after different primary immunizations were equalized. As for the T cell response, we were able to demonstrate a memory function for CD4+ and CD8+ T cells alike. Importantly, both T and antibody responses against wild-type and omicron differed significantly; however, antibody and T cell responses did not correlate with each other and, thus, may contribute differentially to immunity.

Single-cell analysis of the adaptive immune response to SARS-CoV-2 infection and vaccination

Amid the ongoing Coronavirus Disease 2019 (COVID-19) pandemic, vaccination and early therapeutic interventions are the most effective means to combat and control the severity of the disease. Host immune responses to SARS-CoV-2 and its variants, particularly adaptive immune responses, should be fully understood to develop improved strategies to implement these measures. Single-cell multi-omic technologies, including flow cytometry, single-cell transcriptomics, and single-cell T-cell receptor (TCR) and B-cell receptor (BCR) profiling, offer a better solution to examine the protective or pathological immune responses and molecular mechanisms associated with SARS-CoV-2 infection, thus providing crucial support for the development of vaccines and therapeutics for COVID-19. Recent reviews have revealed the overall immune landscape of natural SARS-CoV-2 infection, and this review will focus on adaptive immune responses (including T cells and B cells) to SARS-CoV-2 revealed by single-cell multi-omics technologies. In addition, we explore how the single-cell analyses disclose the critical components of immune protection and pathogenesis during SARS-CoV-2 infection through the comparison between the adaptive immune responses induced by natural infection and by vaccination.

Persistence of Anti-SARS-CoV-2 Spike IgG Antibodies Following COVID-19 Vaccines

Purpose

This study was conducted to investigate antibody immune responses induced by BNT162b2 and AZD1222 human COVID-19 vaccines in Riyadh city, Saudi Arabia.

Patients and Methods

ELISA was used to evaluate antibodies, against the SARS-CoV-2 spike S1 protein, in serum samples from 432 vaccinated individuals at six time points: pre-vaccination (baseline), post-prime, post-boost, 6-months, and 1 year post-vaccination, and 3 weeks post a third dose. Virus microneutralization assay was used to confirm antibody responses in a subset of samples.

Results

Anti-SARS-CoV-2 spike IgG were detected in most subjects post-prime, reached a peak level post-boost, and remained at high level at the 6-month follow-up. At 1 year post-vaccine, the antibody levels were low but increased to a significant level higher than the peak following a third dose. The third dose was given at an average of 250 days after the second dose. The virus microneutralization assay confirmed the neutralization activity of the induced SARS-CoV-2 IgG antibodies. The vaccines induced higher IgG titres at post-prime (p=0.0001) and 6 months (p=0.006) in previously infected individuals. An increased interval between prime and boost, more than recommended time, appeared to enhance the IgG levels (p=0004). Moreover, the vaccines induced higher IgG levels in younger subjects (p=0.01).

Conclusion

These data provide insights and build on the current understanding of immune responses induced by these two vaccines; and support a third boosting dose for these COVID-19 vaccines.

Vaccines Against COVID-19: A Review

As a result of the COVID-19 pandemic, various joint efforts have been made to support the creation of vaccines. Different projects have been under development, of which some are in the clinical evaluation stage and others in are in phase III with positive results. The aim of this paper was to describe the current situation of the development and production of vaccines available to the population to facilitate future research and continue developing and proposing ideas for the benefit of the population. So, we carried out a systematic review using databases such as PubMed, ScienceDirect, SciELO, and MEDLINE, including keywords such as "vaccines," "COVID-19," and "SARS-CoV-2". We reviewed the development and production of the anti-COVID vaccine and its different platforms, the background leading to the massive development of these substances, and the most basic immune aspects for a better understanding of their physiological activity and the immune response in those who receive the vaccine. We also analyzed immunization effects in populations with any medical or physiological conditions (such as immunosuppression, people with comorbidities, and pregnancy), as well as the response to immunization with heterologous vaccines and the hybrid immunity (the combination of natural immunity to SARS-CoV-2 with immunity generated by the vaccine). Likewise, we address the current situation in Mexico and its role in managing the vaccination process against SARS-CoV-2 at the national and international levels. There are still many clinical and molecular aspects to be described, such as the duration of active immunity and the development of immunological memory, to mention some of the most important ones. However, due to the short time since the global vaccination roll-out and that it has been progressive (not counting children and people with medical conditions), it is premature to say whether a second vaccination schedule will be necessary for the near future. Thus, it is essential to continue with health measures.

Higher SARS-CoV-2 Spike Binding Antibody Levels and Neutralization Capacity 6 Months after Heterologous Vaccination with AZD1222 and BNT162b2

Within a year after the emergence of SARS-CoV-2, several vaccines had been developed, clinically evaluated, proven to be efficacious in preventing symptomatic disease, and licensed for global use. The remaining questions about the vaccines concern the duration of protection offered by vaccination and its efficacy against variants of concern. Therefore, we set out to analyze the humoral and cellular immune responses 6 months into homologous and heterologous prime-boost vaccinations. We recruited 190 health care workers and measured their anti-spike IgG levels, their neutralizing capacities against the Wuhan-Hu-1 strain and the Delta variant using a surrogate viral neutralization test, and their IFNγ-responses towards SARS-CoV-2-derived spike peptides. We here show that IFNγ secretion in response to peptide stimulation was significantly enhanced in all three vaccination groups and comparable in magnitude. In contrast, the heterologous prime-boost regimen using AZD1222 and BNT162b2 yielded the highest anti-spike IgG levels, which were 3–4.5 times more than the levels resulting from homologous AZD1222 and BNT162b2 vaccination, respectively. Likewise, the neutralizing capacity against both the wild type as well as the Delta receptor binding domains was significantly higher following the heterologous prime-boost regimen. In conclusion, our results suggest that mixing different SARS-CoV-2 vaccines might lead to more efficacious and longer-lasting humoral protection against breakthrough infections.

Antibody attributes that predict the neutralization and effector function of polyclonal responses to SARS-CoV-2

BACKGROUND

While antibodies can provide significant protection from SARS-CoV-2 infection and disease sequelae, the specific attributes of the humoral response that contribute to immunity are incompletely defined.

METHODS

We employ machine learning to relate characteristics of the polyclonal antibody response raised by natural infection to diverse antibody effector functions and neutralization potency with the goal of generating both accurate predictions of each activity based on antibody response profiles as well as insights into antibody mechanisms of action.

RESULTS

To this end, antibody-mediated phagocytosis, cytotoxicity, complement deposition, and neutralization were accurately predicted from biophysical antibody profiles in both discovery and validation cohorts. These models identified SARS-CoV-2-specific IgM as a key predictor of neutralization activity whose mechanistic relevance was supported experimentally by depletion.

CONCLUSIONS

Validated models of how different aspects of the humoral response relate to antiviral antibody activities suggest desirable attributes to recapitulate by vaccination or other antibody-based interventions.