Does prior immunization with measles, mumps, and rubella vaccines contribute to the antibody response to COVID-19 antigens?

BACKGROUND: Incidence and severity of SARS-CoV2 infection are significantly lower in children and teenagers proposing that certain vaccines, routinely administered to neonates and children may provide cross-protection against this emerging infection. OBJECTIVE: To assess the cross-protection induced by prior measles, mumps and rubella (MMR) vaccinations against COVID-19. METHODS: The antibody responses to MMR and tetanus vaccines were determined in 53 patients affected with SARS-CoV2 infection and 52 age-matched healthy subjects. Serum levels of antibodies specific for NP and RBD of SARS-CoV2 were also determined in both groups of subjects with ELISA. RESULTS: Our results revealed significant differences in anti-NP (P<0.0001) and anti-RBD (P<0.0001) IgG levels between patients and healthy controls. While the levels of rubella- and mumps specific IgG were not different in the two groups of subjects, measles-specific IgG was significantly higher in patients (P<0.01). The serum titer of anti-tetanus antibody, however, was significantly lower in patients compared to healthy individuals (P<0.01). CONCLUSION: Our findings suggest that measles vaccination triggers those B cells cross-reactive with SARS-CoV2 antigens leading to the production of increased levels of measles-specific antibody.

Three doses of prototypic SARS-CoV-2 inactivated vaccine induce cross-protection against its variants of concern.

Variants are globally emerging very quickly following pandemic prototypic SARS-CoV-2. To evaluate the cross-protection of prototypic SARS-CoV-2 vaccine against its variants, we vaccinated rhesus monkeys with three doses of prototypic SARS-CoV-2 inactivated vaccine, followed by challenging with emerging SARS-CoV-2 variants of concern (VOCs). These vaccinated animals produced neutralizing antibodies against Alpha, Beta, Delta, and Omicron variants, although there were certain declinations of geometric mean titer (GMT) as compared with prototypic SARS-CoV-2. Of note, in vivo this prototypic vaccine not only reduced the viral loads in nasal, throat and anal swabs, pulmonary tissues, but also improved the pathological changes in the lung infected by variants of Alpha, Beta, and Delta. In summary, the prototypic SARS-CoV-2 inactivated vaccine in this study protected against VOCs to certain extension, which is of great significance for prevention and control of COVID-19.

Cellular and humoral functional responses after BNT162b2 mRNA vaccination differ longitudinally between naive and subjects recovered from COVID-19.

We have analyzed BNT162b2 vaccine-induced immune responses in naive subjects and individuals recovered from coronavirus disease 2019 (COVID-19), both soon after (14 days) and later after (almost 8 months) vaccination. Plasma spike (S)-specific immunoglobulins peak after one vaccine shot in individuals recovered from COVID-19, while a second dose is needed in naive subjects, although the latter group shows reduced levels all along the analyzed period. Despite how the neutralization capacity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mirrors this behavior early after vaccination, both groups show comparable neutralizing antibodies and S-specific B cell levels late post-vaccination. When studying cellular responses, naive individuals exhibit higher SARS-CoV-2-specific cytokine production, CD4+ T cell activation, and proliferation than do individuals recovered from COVID-19, with patent inverse correlations between humoral and cellular variables early post-vaccination. However, almost 8 months post-vaccination, SARS-CoV-2-specific responses are comparable between both groups. Our data indicate that a previous history of COVID-19 differentially determines the functional T and B cell-mediated responses to BNT162b2 vaccination over time.

Immunological dysfunction persists for 8 months following initial mild-to-moderate SARS-CoV-2 infection.

A proportion of patients surviving acute coronavirus disease 2019 (COVID-19) infection develop post-acute COVID syndrome (long COVID (LC)) lasting longer than 12 weeks. Here, we studied individuals with LC compared to age- and gender-matched recovered individuals without LC, unexposed donors and individuals infected with other coronaviruses. Patients with LC had highly activated innate immune cells, lacked naive T and B cells and showed elevated expression of type I IFN (IFN-ß) and type III IFN (IFN-λ1) that remained persistently high at 8 months after infection. Using a log-linear classification model, we defined an optimal set of analytes that had the strongest association with LC among the 28 analytes measured. Combinations of the inflammatory mediators IFN-ß, PTX3, IFN-γ, IFN-λ2/3 and IL-6 associated with LC with 78.5-81.6% accuracy. This work defines immunological parameters associated with LC and suggests future opportunities for prevention and treatment.

Elucidating T Cell and B Cell Responses to SARS-CoV-2 in Humans: Gaining Insights into Protective Immunity and Immunopathology.

The SARS-CoV-2 pandemic is an unprecedented epochal event on at least two fronts. Firstly, in terms of the rapid spread and the magnitude of the outbreak, and secondly, on account of the equally swift response of the scientific community that has galvanized itself into action and has successfully developed, tested and deployed highly effective and novel vaccines in record time to combat the virus. The sophistication and diversification of the scientific toolbox we now have at our disposal has enabled us to interrogate both the breadth and the depth of the immune response to a degree that is unparalleled in recent memory. In terms of our understanding of what is critical to contain the virus and mitigate the effects the pandemic, neutralizing antibodies to SARS-CoV-2 garner most of the attention, however, it is essential to recognize that it is the quality and the fitness of the virus-specific T cell and B cell response that lays the foundation and the backdrop for an effective neutralizing antibody response. In this report, we will review some of the key findings that have helped define and delineate some of the essential attributes of T and B cell responses in the setting of SARS-CoV-2 infection.

Microfluidic characterisation reveals broad range of SARS-CoV-2 antibody affinity in human plasma.

The clinical outcome of SARS-CoV-2 infections, which can range from asymptomatic to lethal, is crucially shaped by the concentration of antiviral antibodies and by their affinity to their targets. However, the affinity of polyclonal antibody responses in plasma is difficult to measure. Here we used microfluidic antibody affinity profiling (MAAP) to determine the aggregate affinities and concentrations of anti-SARS-CoV-2 antibodies in plasma samples of 42 seropositive individuals, 19 of which were healthy donors, 20 displayed mild symptoms, and 3 were critically ill. We found that dissociation constants, K d, of anti-receptor-binding domain antibodies spanned 2.5 orders of magnitude from sub-nanomolar to 43 nM. Using MAAP we found that antibodies of seropositive individuals induced the dissociation of pre-formed spike-ACE2 receptor complexes, which indicates that MAAP can be adapted as a complementary receptor competition assay. By comparison with cytopathic effect-based neutralisation assays, we show that MAAP can reliably predict the cellular neutralisation ability of sera, which may be an important consideration when selecting the most effective samples for therapeutic plasmapheresis and tracking the success of vaccinations.

25-Hydroxycholesterol Inhibits Kaposi's Sarcoma Herpesvirus and Epstein-Barr Virus Infections and Activates Inflammatory Cytokine Responses.

Oncogenic gammaherpesviruses express viral products during latent and lytic infection that block the innate immune response. Previously, we found that Kaposi's sarcoma herpesvirus (KSHV/human herpesvirus-8) viral microRNAs (miRNAs) downregulate cholesterol biogenesis, and we hypothesized that this prevents the production of 25-hydroxycholesterol (25HC), a cholesterol derivative. 25HC blocks KSHV de novo infection of primary endothelial cells at a postentry step and decreases viral gene expression of LANA (latency-associated nuclear antigen) and RTA. Herein we expanded on this observation by determining transcriptomic changes associated with 25HC treatment of primary endothelial cells using RNA sequencing (RNA-Seq). We found that 25HC treatment inhibited KSHV gene expression and induced interferon-stimulated genes (ISGs) and several inflammatory cytokines (interleukin 8 [IL-8], IL-1α). Some 25HC-induced genes were partially responsible for the broadly antiviral effect of 25HC against several viruses. Additionally, we found that 25HC inhibited infection of primary B cells by a related oncogenic virus, Epstein-Barr virus (EBV/human herpesvirus-4) by suppressing key viral genes such as LMP-1 and inducing apoptosis. RNA-Seq analysis revealed that IL-1 and IL-8 pathways were induced by 25HC in both primary endothelial cells and B cells. We also found that the gene encoding cholesterol 25-hydroxylase (CH25H), which converts cholesterol to 25HC, can be induced by type I interferon (IFN) in human B cell-enriched peripheral blood mononuclear cells (PBMCs). We propose a model wherein viral miRNAs target the cholesterol pathway to prevent 25HC production and subsequent induction of antiviral ISGs. Together, these results answer some important questions about a widely acting antiviral (25HC), with implications for multiple viral and bacterial infections. IMPORTANCE A cholesterol derivative, 25-hydroxycholesterol (25HC), has been demonstrated to inhibit infections from widely different bacteria and viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, its mechanism of activity is still not fully understood. In this work, we look at gene expression changes in the host and virus after 25HC treatment to find clues about its antiviral activity. We likewise demonstrate that 25HC is also antiviral against EBV, a common cancer-causing virus. We compared our results with previous data from antiviral screening assays and found the same pathways resulting in antiviral activity. Together, these results bring us closer to understanding how a modified form of cholesterol works against several viruses.

Immune memory from SARS-CoV-2 infection in hamsters provides variant-independent protection but still allows virus transmission.

SARS-CoV-2 has caused morbidity and mortality across the globe. As the virus spreads, new variants are arising that show enhanced capacity to bypass preexisting immunity. To understand the memory response to SARS-CoV-2, here, we monitored SARS-CoV-2­specific T and B cells in a longitudinal study of infected and recovered golden hamsters (Mesocricetus auratus). We demonstrated that engagement of the innate immune system after SARS-CoV-2 infection was delayed but was followed by a pronounced adaptive response. Moreover, T cell adoptive transfer conferred a reduction in virus levels and rapid induction of SARS-CoV-2­specific B cells, demonstrating that both lymphocyte populations contributed to the overall response. Reinfection of recovered animals with a SARS-CoV-2 variant of concern showed that SARS-CoV-2­specific T and B cells could effectively control the infection that associated with the rapid induction of neutralizing antibodies but failed to block transmission to both naïve and seroconverted animals. These data suggest that the adaptive immune response to SARS-CoV-2 is sufficient to provide protection to the host, independent of the emergence of variants.

Discovery and characterization of high-affinity, potent SARS-CoV-2 neutralizing antibodies via single B cell screening.

Monoclonal antibodies that target SARS-CoV-2 with high affinity are valuable for a wide range of biomedical applications involving novel coronavirus disease (COVID-19) diagnosis, treatment, and prophylactic intervention. Strategies for the rapid and reliable isolation of these antibodies, especially potent neutralizing antibodies, are critical toward improved COVID-19 response and informed future response to emergent infectious diseases. In this study, single B cell screening was used to interrogate antibody repertoires of immunized mice and isolate antigen-specific IgG1+ memory B cells. Using these methods, high-affinity, potent neutralizing antibodies were identified that target the receptor-binding domain of SARS-CoV-2. Further engineering of the identified molecules to increase valency resulted in enhanced neutralizing activity. Mechanistic investigation revealed that these antibodies compete with ACE2 for binding to the receptor-binding domain of SARS-CoV-2. These antibodies may warrant further development for urgent COVID-19 applications. Overall, these results highlight the potential of single B cell screening for the rapid and reliable identification of high-affinity, potent neutralizing antibodies for infectious disease applications.

Seasonal coronavirus-specific B cells with limited SARS-CoV-2 cross-reactivity dominate the IgG response in severe COVID-19.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of coronavirus disease 2019 (COVID-19). Little is known about the interplay between preexisting immunity to endemic seasonal coronaviruses and the development of a SARS-CoV-2-specific IgG response. We investigated the kinetics, breadth, magnitude, and level of cross-reactivity of IgG antibodies against SARS-CoV-2 and heterologous seasonal and epidemic coronaviruses at the clonal level in patients with mild or severe COVID-19 as well as in disease control patients. We assessed antibody reactivity to nucleocapsid and spike antigens and correlated this IgG response to SARS-CoV-2 neutralization. Patients with COVID-19 mounted a mostly type-specific SARS-CoV-2 response. Additionally, IgG clones directed against a seasonal coronavirus were boosted in patients with severe COVID-19. These boosted clones showed limited cross-reactivity and did not neutralize SARS-CoV-2. These findings indicate a boost of poorly protective CoV-specific antibodies in patients with COVID-19 that correlated with disease severity, revealing "original antigenic sin."

Alterations in lymphocyte subsets and monocytes in patients diagnosed with SARS-CoV-2 pneumonia: a mini review of the literature.

OBJECTIVE: Complete blood count parameters are frequently altered in COVID-19 patients. Leucopenia and lymphopenia are the most common findings. This is not specific to COVID-19 as similar alterations are found in various other viral infections. This work is intended to summarize the evidence regarding white blood cell and lymphocyte subset alterations in COVID-19 and their clinical implications. MATERIALS AND METHODS: A PubMed search was conducted to identify relevant original studies. Articles not available in English or referring exclusively to pediatric patients were excluded. The study was designed as a narrative review from its inception. RESULTS: Complete white blood cell number and lymphocytes may be reduced in COVID-19 patients. Circulating CD4+ cells (helper T lymphocytes), CD8+ cells (cytotoxic T lymphocytes), regulatory T cells and natural killer (NK) cells may be reduced, with a greater reduction observed in critically ill patients. CD4+ and regulatory cell deficiencies may contribute to the cytokine storm and subsequent tissue damage observed in severe COVID-19 infection. NK and CD8+ cell deficiency might delay infection clearance. These aberrations of cellular immunity may contribute significantly to the pathogenesis of the disease. Alterations observed in monocyte function can also be implicated as they are effector cells responsible for tissue damage and remodeling. B cell dysfunction and maturation abnormalities have also been reported, suggesting that the virus also impairs humoral immunity. CONCLUSIONS: Lymphocyte subset abnormalities may be useful prognostic biomarkers for COVID-19, with circulating CD8+ cell count being the most promising as a predictor of severe disease requiring mechanical ventilation and mortality.

Single-cell epigenomic landscape of peripheral immune cells reveals establishment of trained immunity in individuals convalescing from COVID-19.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection often causes severe complications and even death. However, asymptomatic infection has also been reported, highlighting the difference in immune responses among individuals. Here we performed single-cell chromatin accessibility and T cell-receptor analyses of peripheral blood mononuclear cells collected from individuals convalescing from COVID-19 and healthy donors. Chromatin remodelling was observed in both innate and adaptive immune cells in the individuals convalescing from COVID-19. Compared with healthy donors, recovered individuals contained abundant TBET-enriched CD16+ and IRF1-enriched CD14+ monocytes with sequential trained and activated epigenomic states. The B-cell lineage in recovered individuals exhibited an accelerated developmental programme from immature B cells to antibody-producing plasma cells. Finally, an integrated analysis of single-cell T cell-receptor clonality with the chromatin accessibility landscape revealed the expansion of putative SARS-CoV-2-specific CD8+ T cells with epigenomic profiles that promote the differentiation of effector or memory cells. Overall, our data suggest that immune cells of individuals convalescing from COVID-19 exhibit global remodelling of the chromatin accessibility landscape, indicative of the establishment of immunological memory.

Humoral Immunity against SARS-CoV-2 and the Impact on COVID-19 Pathogenesis.

It has been more than a year since severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first emerged. Many studies have provided insights into the various aspects of the immune response in coronavirus disease 2019 (COVID-19). Especially for antibody treatment and vaccine development, humoral immunity to SARS-CoV-2 has been studied extensively, though there is still much that is unknown and controversial. Here, we introduce key discoveries on the humoral immune responses in COVID-19, including the immune dynamics of antibody responses and correlations with disease severity, neutralizing antibodies and their cross-reactivity, how long the antibody and memory B-cell responses last, aberrant autoreactive antibodies generated in COVID-19 patients, and the efficacy of currently available therapeutic antibodies and vaccines against circulating SARS-CoV-2 variants, and highlight gaps in the current knowledge.

Detection of differentially abundant cell subpopulations in scRNA-seq data.

Comprehensive and accurate comparisons of transcriptomic distributions of cells from samples taken from two different biological states, such as healthy versus diseased individuals, are an emerging challenge in single-cell RNA sequencing (scRNA-seq) analysis. Current methods for detecting differentially abundant (DA) subpopulations between samples rely heavily on initial clustering of all cells in both samples. Often, this clustering step is inadequate since the DA subpopulations may not align with a clear cluster structure, and important differences between the two biological states can be missed. Here, we introduce DA-seq, a targeted approach for identifying DA subpopulations not restricted to clusters. DA-seq is a multiscale method that quantifies a local DA measure for each cell, which is computed from its k nearest neighboring cells across a range of k values. Based on this measure, DA-seq delineates contiguous significant DA subpopulations in the transcriptomic space. We apply DA-seq to several scRNA-seq datasets and highlight its improved ability to detect differences between distinct phenotypes in severe versus mildly ill COVID-19 patients, melanomas subjected to immune checkpoint therapy comparing responders to nonresponders, embryonic development at two time points, and young versus aging brain tissue. DA-seq enabled us to detect differences between these phenotypes. Importantly, we find that DA-seq not only recovers the DA cell types as discovered in the original studies but also reveals additional DA subpopulations that were not described before. Analysis of these subpopulations yields biological insights that would otherwise be undetected using conventional computational approaches.

B cell genomics behind cross-neutralization of SARS-CoV-2 variants and SARS-CoV.

Monoclonal antibodies (mAbs) are a focus in vaccine and therapeutic design to counteract severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants. Here, we combined B cell sorting with single-cell VDJ and RNA sequencing (RNA-seq) and mAb structures to characterize B cell responses against SARS-CoV-2. We show that the SARS-CoV-2-specific B cell repertoire consists of transcriptionally distinct B cell populations with cells producing potently neutralizing antibodies (nAbs) localized in two clusters that resemble memory and activated B cells. Cryo-electron microscopy structures of selected nAbs from these two clusters complexed with SARS-CoV-2 spike trimers show recognition of various receptor-binding domain (RBD) epitopes. One of these mAbs, BG10-19, locks the spike trimer in a closed conformation to potently neutralize SARS-CoV-2, the recently arising mutants B.1.1.7 and B.1.351, and SARS-CoV and cross-reacts with heterologous RBDs. Together, our results characterize transcriptional differences among SARS-CoV-2-specific B cells and uncover cross-neutralizing Ab targets that will inform immunogen and therapeutic design against coronaviruses.

Immune Memory in Mild COVID-19 Patients and Unexposed Donors Reveals Persistent T Cell Responses After SARS-CoV-2 Infection.

Understanding the causes of the diverse outcome of COVID-19 pandemic in different geographical locations is important for the worldwide vaccine implementation and pandemic control responses. We analyzed 42 unexposed healthy donors and 28 mild COVID-19 subjects up to 5 months from the recovery for SARS-CoV-2 specific immunological memory. Using HLA class II predicted peptide megapools, we identified SARS-CoV-2 cross-reactive CD4+ T cells in around 66% of the unexposed individuals. Moreover, we found detectable immune memory in mild COVID-19 patients several months after recovery in the crucial arms of protective adaptive immunity; CD4+ T cells and B cells, with a minimal contribution from CD8+ T cells. Interestingly, the persistent immune memory in COVID-19 patients is predominantly targeted towards the Spike glycoprotein of the SARS-CoV-2. This study provides the evidence of both high magnitude pre-existing and persistent immune memory in Indian population. By providing the knowledge on cellular immune responses to SARS-CoV-2, our work has implication for the development and implementation of vaccines against COVID-19.

A novel STING agonist for cancer immunotherapy and a SARS-CoV-2 vaccine adjuvant.

A novel STING agonist, CDGSF, ipsilaterally modified with phosphorothioate and fluorine, was synthesized. The phosphorothioate in CDGSF might be a site for covalent conjugation. Injection of CDGSF generated an immunogenic ("hot") tumor microenvironment to suppress melanoma, more efficiently than dithio CDG. In particular, immunization with SARS-CoV-2 spike protein using CDGSF as an adjuvant elicited an exceptionally high antibody titer and a robust T cell response, overcoming the drawbacks of aluminum hydroxide. These results highlighted the therapeutic potential of CDGSF for cancer immunotherapy and the adjuvant potential of the STING agonist in the SARS-CoV-2 vaccine for the first time.

B careful: Humoral responses and COVID-19 severity.

Neutralizing antibody responses to SARS-CoV-2, though often of limited longevity, have generally been assumed to be protective against COVID-19 disease.