Robust T Cell Immunity in Convalescent Individuals with Asymptomatic or Mild COVID-19

Global perspective of COVID-19 epidemiology for a full-cycle pandemic

As of October 2020, there are >1 million documented deaths with COVID-19. Excess deaths can be caused by both COVID-19 and the measures taken. COVID-19 shows extremely strong risk stratification across age, socioeconomic factors, and clinical factors. Calculation of years-of-life-lost from COVID-19 is methodologically challenging and can yield misleading over-estimates. Many early deaths may have been due to suboptimal management, malfunctional health systems, hydroxychloroquine, sending COVID-19 patients to nursing homes, and nosocomial infections; such deaths are partially avoidable moving forward. About 10% of the global population may be infected by October 2020. Global infection fatality rate is 0.15-0.20% (0.03-0.04% in those <70 years), with large variability across locations with different age-structure, institutionalization rates, socioeconomic inequalities, population-level clinical risk profile, public health measures, and health care. There is debate on whether at least 60% of the global population must be infected for herd immunity, or, conversely, mixing heterogeneity and pre-existing cross-immunity may allow substantially lower thresholds. Simulations are presented with a total of 1.58-8.76 million COVID-19 deaths over 5-years (1/2020-12/2024) globally (0.5-2.9% of total global deaths). The most favorable figures in that range would be feasible if high risk groups can be preferentially protected with lower infection rates than the remaining population. Death toll may also be further affected by potential availability of effective vaccines and treatments, optimal management and measures taken, COVID-19 interplay with influenza and other health problems, reinfection potential, and any chronic COVID-19 consequences. Targeted, precise management of the pandemic and avoiding past mistakes would help minimize mortality.

Intrafamilial Exposure to SARS-CoV-2 Associated with Cellular Immune Response without Seroconversion, France

We investigated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)–specific antibodies and T-cell responses against SARS-CoV-2 and human coronavirus (HCoV) 229E and OC43 in 11 SARS-CoV-2 serodiscordant couples in Strasbourg, France, in which 1 partner had evidence of mild coronavirus disease (COVID-19) and in 10 unexposed healthy controls. Patients with confirmed COVID-19 were considered index patients and their partners close contacts. All index patients displayed positive SARS-CoV-2–specific antibody and T-cell responses that lasted up to 102 days after symptom onset. All contacts remained seronegative for SARS-CoV-2; however, 6 reported COVID-19 symptoms within a median of 7 days after their partners, and 4 of those showed a positive SARS-CoV-2–specific T-cell response against 3 or 4 SARS-CoV-2 antigens that lasted up to 93 days after symptom onset. The 11 couples and controls displayed positive T-cell responses against HCoV-229E or HCoV-OC43. These data suggest that exposure to SARS-CoV-2 can induce virus-specific T-cell responses without seroconversion.

Late incidence of SARS-CoV-2 infection in a highly-endemic remote rural village. A prospective population-based cohort study

Data on SARS-CoV-2 transmission in rural communities is scarce or non-existent. A previous cross-sectional study in middle-aged and older adults enrolled in the Atahualpa Project Cohort demonstrated that 45% of participants had SARS-CoV-2 antibodies, 77% of whom were symptomatic. Here, we assessed the incidence of SARS-CoV-2 infection in the above-mentioned rural population. One month after baseline testing, 362 of 370 initially seronegative individuals were re-tested to assess incidence of seroconversion and associated risk factors. Twenty-eight of them (7.7%) became seropositive. The overall incidence rate ratio was 7.4 per 100 person months of potential virus exposure (95% C.I.: 4.7-10.2). Six seroconverted individuals (21.4%) developed SARS-CoV-2-related symptomatology. The only covariate significantly associated with seroconversion was the use of an open latrine. Predictive margins showed that these individuals were 2.5 times more likely to be infected (95% C.I.: 1.03-6.1) than those using a flushing toilet. Therefore, along one month, approximately 8% of seronegative individuals became infected, even after almost half of the population was already seropositive. Nevertheless, a smaller proportion of incident cases were symptomatic (21% versus 77% of the earlier cases), and no deaths were recorded. Whether this decreased clinical expression resulted from a lower viral load in new infections cannot be determined. Increased seroconversion in individuals using latrines is consistent with a contributory role of fecal-oral transmission, although we cannot rule out the possibility that latrines are acting as a proxy for poverty or other unknown interacting variables.

Current COVID-19 vaccine candidates: Implications in the Saudi population

AIM

The purpose of this review is to discuss the current status of local and international efforts undergoing clinical trials aiming at developing a Coronavirus Disease-2019 (COVID-19) vaccine, and to highlight the anticipated challenges of this vaccine globally and in Saudi Arabia.

PRESENT FINDINGS

COVID-19 vaccine development efforts started in early January 2020 when Chinese scientists shared the Coronavirus genomic sequence in public domain. Approximately 321 research groups initiated the search for a vaccine, out of which 41 have reached phase I/II trails and 11 reached phase-III clinical trials, including approved vaccines for early to limited use. Out of these projects are two labs in the Kingdom of Saudi Arabia still in early stages of development of a COVID-19 vaccine. Several vaccine attempts are being tested from traditional, attenuated virus methods, to new nucleic acid-based designs. However, no vaccine has yet completed clinical trials and reached public domain.In spite of the challenges faced during previous vaccine trials, researchers have found that Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), the causative agent of COVID-19 is structurally similar to the (SARS-CoV-1) and the Middle Eastern Respiratory Syndrome Coronavirus (MERS-CoV), which caused epidemics in 2003 and 2012 respectively. Both SARS strains show identical affinity towards the type-II alveolar pneumocytes angiotensin converting enzyme-2 (ACE-2) receptor binding domains and therefore, similar pathogenicity. The race to develop the vaccine is predominantly for individuals at high risk of developing the infection, i.e. population groups who are most susceptible to experiencing fatal symptoms of the coronavirus. These include patients with comorbidities, above the age of 60 years and people at risk of contracting large viral loads, such as healthcare providers caring for critical admissions in in-patient wards, Intensive Care Units and Emergency Room settings.

SUMMARY

Many different vaccine strategies are under development throughout different stages of the research timeline; however, it is estimated that none will show favorable results before end of 2020. For any immunization or interventional prevention/therapy system to reach the public and patients at high risk, it needs to undergo multiple phase trials to ensure safety and effectiveness. In this scoping review we aim to map the literature on COVID-19 vaccines and provide recommendations related to gaps in research, applicability and expected challenges for implementation of nationwide vaccination in Saudi Arabia.

On the relationship between BCG coverage and national COVID-19 outcome: could 'heterologous' herd immunity explain why some countries are better off?

The COVID-19 pandemic has affected most parts of the global society since its emergence, and the scientific community has been challenged with questions urgently demanding answers. One of the early hypotheses on COVID-19 outcome was that some protection could be offered by the tuberculosis vaccine (BCG), and several clinical studies were initiated along with the emergence of numerous observational studies on the relationship between BCG and COVID-19 severity. In the present work, I demonstrate a strong correlation between the number of years that countries implemented BCG vaccination plans and age-standardized mortality rates during the first months of the pandemic in Europe. Further analyses of age groups in two European countries with comparably few confounding factors and easily identifiable groups of BCG-vaccinated and non-vaccinated subgroups suggest a population-level effect of BCG on national outcomes of COVID-19. This phenomenon of 'heterologous herd immunity' deserves further investigation, both in epidemiological and experimental studies.

Healthy donor T cell responses to common cold coronaviruses and SARS-CoV-2

BACKGROUNDT cell responses to the common cold coronaviruses have not been well characterized. Preexisting T cell immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been reported, and a recent study suggested that this immunity was due to cross-recognition of the novel coronavirus by T cells specific for the common cold coronaviruses.METHODSWe used the enzyme-linked immunospot (ELISPOT) assay to characterize the T cell responses against peptide pools derived from the spike protein of 3 common cold coronaviruses (HCoV-229E, HCoV-NL63, and HCoV-OC43) and SARS-CoV-2 in 21 healthy donors (HDs) who were seronegative for SARS-CoV-2 and had no known exposure to the virus. An in vitro expansion culture assay was also used to analyze memory T cell responses.RESULTSWe found responses to the spike protein of the 3 common cold coronaviruses in many of the donors. We then focused on HCoV-NL63 and detected broad T cell responses to the spike protein and identified 22 targeted peptides. Interestingly, only 1 study participant had a significant response to SARS-CoV-2 spike or nucleocapsid protein in the ELISPOT assay. In vitro expansion studies suggested that T cells specific for the HCoV-NL63 spike protein in this individual could also recognize SARS-CoV-2 spike protein peptide pools.CONCLUSIONHDs have circulating T cells specific for the spike proteins of HCoV-NL63, HCoV-229E, and HCoV-OC43. T cell responses to SARS-CoV-2 spike and nucleocapsid proteins were present in only 1 participant and were potentially the result of cross-recognition by T cells specific for the common cold coronaviruses. Further studies are needed to determine whether this cross-recognition influences coronavirus disease 2019 (COVID-19) outcomes.

COVID-19: The Emerging Immunopathological Determinants for Recovery or Death

Hyperactivation of the host immune system during infection by SARS-CoV-2 is the leading cause of death in COVID-19 patients. It is also evident that patients who develop mild/moderate symptoms and successfully recover display functional and well-regulated immune response. Whereas a delayed initial interferon response is associated with severe disease outcome and can be the tipping point towards immunopathological deterioration, often preceding death in COVID-19 patients. Further, adaptive immune response during COVID-19 is heterogeneous and poorly understood. At the same time, some studies suggest activated T and B cell response in severe and critically ill patients and the presence of SARS-CoV2-specific antibodies. Thus, understanding this problem and the underlying molecular pathways implicated in host immune function/dysfunction is imperative to devise effective therapeutic interventions. In this comprehensive review, we discuss the emerging immunopathological determinants and the mechanism of virus evasion by the host cell immune system. Using the knowledge gained from previous respiratory viruses and the emerging clinical and molecular findings on SARS-CoV-2, we have tried to provide a holistic understanding of the host innate and adaptive immune response that may determine disease outcome. Considering the critical role of the adaptive immune system during the viral clearance, we have presented the molecular insights of the plausible mechanisms involved in impaired T cell function/dysfunction during various stages of COVID-19.

Longitudinal observation and decline of neutralizing antibody responses in the three months following SARS-CoV-2 infection in humans

Antibody responses to SARS-CoV-2 can be detected in most infected individuals 10-15 d after the onset of COVID-19 symptoms. However, due to the recent emergence of SARS-CoV-2 in the human population, it is not known how long antibody responses will be maintained or whether they will provide protection from reinfection. Using sequential serum samples collected up to 94 d post onset of symptoms (POS) from 65 individuals with real-time quantitative PCR-confirmed SARS-CoV-2 infection, we show seroconversion (immunoglobulin (Ig)M, IgA, IgG) in >95% of cases and neutralizing antibody responses when sampled beyond 8 d POS. We show that the kinetics of the neutralizing antibody response is typical of an acute viral infection, with declining neutralizing antibody titres observed after an initial peak, and that the magnitude of this peak is dependent on disease severity. Although some individuals with high peak infective dose (ID50 > 10,000) maintained neutralizing antibody titres >1,000 at >60 d POS, some with lower peak ID50 had neutralizing antibody titres approaching baseline within the follow-up period. A similar decline in neutralizing antibody titres was observed in a cohort of 31 seropositive healthcare workers. The present study has important implications when considering widespread serological testing and antibody protection against reinfection with SARS-CoV-2, and may suggest that vaccine boosters are required to provide long-lasting protection.

Predicted Cellular Immunity Population Coverage Gaps for SARS-CoV-2 Subunit Vaccines and Their Augmentation by Compact Peptide Sets

Subunit vaccines induce immunity to a pathogen by presenting a component of the pathogen and thus inherently limit the representation of pathogen peptides for cellular immunity-based memory. We find that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) subunit peptides may not be robustly displayed by the major histocompatibility complex (MHC) molecules in certain individuals. We introduce an augmentation strategy for subunit vaccines that adds a small number of SARS-CoV-2 peptides to a vaccine to improve the population coverage of pathogen peptide display. Our population coverage estimates integrate clinical data on peptide immunogenicity in convalescent COVID-19 patients and machine learning predictions. We evaluate the population coverage of 9 different subunits of SARS-CoV-2, including 5 functional domains and 4 full proteins, and augment each of them to fill a predicted coverage gap.

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Clinical data and machine learning predict SARS-CoV-2 peptide-HLA immunogenicity

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Human population coverage gaps of COVID-19 subunit vaccines are predicted

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Subunit augmentation improves vaccine population coverage for cellular immunity

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Subunit-free peptide vaccines are predicted to have high population coverage

Low-Avidity CD4+ T Cell Responses to SARS-CoV-2 in Unexposed Individuals and Humans with Severe COVID-19

CD4⁺ T cells reactive against SARS-CoV-2 can be found in unexposed individuals, and these are suggested to arise in response to common cold coronavirus (CCCoV) infection. Here, we utilized SARS-CoV-2-reactive CD4⁺ T cell enrichment to examine the antigen avidity and clonality of these cells, as well as the relative contribution of CCCoV cross-reactivity. SARS-CoV-2-reactive CD4⁺ memory T cells were present in virtually all unexposed individuals examined, displaying low functional avidity and multiple, highly variable cross-reactivities that were not restricted to CCCoVs. SARS-CoV-2-reactive CD4⁺ T cells from COVID-19 patients lacked cross-reactivity to CCCoVs, irrespective of strong memory T cell responses against CCCoV in all donors analyzed. In severe but not mild COVID-19, SARS-CoV-2-specific T cells displayed low functional avidity and clonality, despite increased frequencies. Our findings identify low-avidity CD4⁺ T cell responses as a hallmark of severe COVID-19 and argue against a protective role for CCCoV-reactive T cells in SARS-CoV-2 infection.

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Low avidity and broad cross-reactivities of pre-existing SARS-CoV-2 memory T cells

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Strong CCCoV-specific memory CD4⁺ T cell responses in all analyzed individuals

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SARS-CoV-2-specific CD4⁺ T cells in COVID-19 patients lack cross-reactivity to CCCoVs

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Low avidity and clonality of SARS-CoV-2-specific T cell responses in severe COVID-19

Could Naturally Occurring Coronaviral Diseases in Animals Serve as Models for COVID-19? A Review Focusing on the Bovine Model

The current pandemic of COVID-19 has highlighted the importance of basic studies on coronaviruses (CoVs) in general, and severe acute respiratory syndrome CoV type 2 (SARS-CoV-2) in particular. CoVs have for long been studied in veterinary medicine, due to their impact on animal health and welfare, production, and economy. Several animal models using coronaviral disease in the natural host have been suggested. In this review, different animal models are discussed, with the main focus on bovine CoV (BCoV). BCoV is endemic in the cattle population worldwide and has been known and studied for several decades. SARS-CoV-2 and BCoV are both betacoronaviruses, where BCoV is highly similar to human coronavirus (HCoV) OC43, encompassing the same virus species (Betacoronavirus 1). BCoV causes respiratory and gastrointestinal disease in young and adult cattle. This review summarizes the current knowledge of the similarities and dissimilarities between BCoV and SARS-CoV-2, as well as discussing the usage of BCoV as a model for human CoVs, including SARS-CoV-2.

Convalescent Memory T Cell Immunity in Individuals with Mild or Asymptomatic SARS-CoV-2 Infection May Result from an Evolutionarily Adapted Immune Response to Coronavirus and the 'Common Cold'

Recent studies have shown a significant level of T cell immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in convalescent coronavirus disease 2019 (COVID-19) patients and unexposed healthy individuals. Also, SARS-CoV-2-reactive T memory cells occur in unexposed healthy individuals from endemic coronaviruses that cause the 'common cold.' The finding of the expression of adaptive SARS-CoV-2-reactive T memory cells in unexposed healthy individuals may be due to multiple cross-reactive viral protein targets following previous exposure to endemic human coronavirus infections. The opinion of the authors is that determination of protein sequence homologies across seemingly disparate viral protein libraries may provide epitope-matching data that link SARS-CoV-2-reactive T memory cell signatures to prior administration of cross-reacting vaccines to common viral pathogens. Exposure to SARS-CoV-2 initiates diverse cellular immune responses, including the associated 'cytokine storm'. Therefore, it is possible that the intact virus possesses a required degree of conformational matching, or stereoselectivity, to effectively target its receptor on multiple cell types. Therefore, conformational matching may be viewed as an evolving mechanism of viral infection and viral replication by an evolutionary modification of the angiotensin-converting enzyme 2 (ACE2) receptor required for SARS-CoV-2 binding and host cell entry. The authors propose that convalescent memory T cell immunity in individuals with mild or asymptomatic SARS-CoV-2 infection may result from an evolutionarily adapted immune response to coronavirus and the 'common cold'.

First year with COVID-19: Assessment and prospects

The vision of health for all by Dr. Halfdan Mahler, Director General of the World Health Organization (WHO) 1973 to 1988, guided public health approaches towards improving life for all those mired in poverty and disease. Research on the Neglected Tropical Diseases (NTDs) of the world's poor was advancing strongly when the coronavirus disease 2019 (COVID-19) struck. Although work on the NTDs did not grind to a halt, the situation is reminiscent of the author Stefan Zweig's passionate account of culture destruction in his book The World of Yesterday from 1941, which gives an insight as to how the war ended traditional life. His thoughts parallel the present situation; however, this time societies are not torn apart by war but instead isolated by a pandemic. It comes upon today's scientists to move fast to make COVID-19 less devastating than the Spanish flu of 1918-1920 that killed more than 3% of the world population...

Imbalance of Regulatory and Cytotoxic SARS-CoV-2-Reactive CD4+ T Cells in COVID-19

The contribution of CD4+ T cells to protective or pathogenic immune responses to SARS-CoV-2 infection remains unknown. Here, we present single-cell transcriptomic analysis of >100,000 viral antigen-reactive CD4+ T cells from 40 COVID-19 patients. In hospitalized patients compared to non-hospitalized patients, we found increased proportions of cytotoxic follicular helper cells and cytotoxic T helper (TH) cells (CD4-CTLs) responding to SARS-CoV-2 and reduced proportion of SARS-CoV-2-reactive regulatory T cells (TREG). Importantly, in hospitalized COVID-19 patients, a strong cytotoxic TFH response was observed early in the illness, which correlated negatively with antibody levels to SARS-CoV-2 spike protein. Polyfunctional TH1 and TH17 cell subsets were underrepresented in the repertoire of SARS-CoV-2-reactive CD4+ T cells compared to influenza-reactive CD4+ T cells. Together, our analyses provide insights into the gene expression patterns of SARS-CoV-2-reactive CD4+ T cells in distinct disease severities.

T cell immunobiology and cytokine storm of COVID-19

2019 coronavirus disease (COVID-19) presents as a newly recognized pneumonia and could rapidly progress into acute respiratory distress syndrome which has brought about a global pandemic. Until now, no curative therapy has been strongly recommended for COVID-19 except for personalized supportive care. T cells and virus-specific T cells are essential to protect against virus infection, including COVID-19. Delayed immune reconstitution (IR) and cytokine storm (CS) remain serious obstacles for the cure of COVID-19. Most COVID-19 patients, especially among elderly patients, had marked lymphopenia and increased neutrophils, but T cell counts in severe COVID-19 patients surviving the disease gradually restored later. Elevated pro-inflammatory cytokines, particularly IL-6, IL-10, IL-2 and IL-17, and exhausted T cells are found in peripheral blood and the lungs. It suggests that Thymosin α1 and adoptive COVID-19-specific T cells could improve IR, while convalescent plasma, IL-6 blockade, mesenchymal stem cells and corticosteroids could suppress CS. More clinical studies in this field worldwide are urgently warranted to pave the way for therapy of COVID-19 in the future.

Special Review: The future of Immunotherapy

During the last two decades, two main schools of modern immunotherapy have come to the forefront. The chimeric anti-CD20 antibody rituximab that was introduced for the treatment of refractory follicular lymphoma in 1998 was one of the first examples of the school of passive immunotherapy. Subsequently major and ever more costly efforts were spent on the development of blockbuster monotherapies including other monoclonal but also bispecific antibodies of highly defined specificity and subclass, antibody-drug conjugates (ADCs), as well as ex vivo expanded tumor-infiltrating lymphocytes, chimeric antigen receptor (CAR)-transduced T cells, and TCR-transduced T cells. On the other hand, there is the school that works toward active induction of patient B- or T-cell immunity against antigens of choice, or active tolerance against pathogenic allergens, auto-antigens or allo-antigens. Stradled in between these two approaches is treatment with blockers of T cell checkpoint control, which releases the brakes of T cells that have already responded to antigen. Extensive and detailed insight into the cellular and molecular interactions that regulate specific immune responses is indispensable in order to be able to optimize efficacy and rule out treatment related toxicity. This applies to all types of immunotherapy. Our knowledge of the checks and balances in the immune system is still increasing at an unprecedented pace, fostering ever more effective and specific (combination) immunotherapies and offering a rich harvest of innovative immunotherapies in the years ahead.

Low rate of COVID-19 seroconversion in health-care workers at a Department of Infectious Diseases in Sweden during the later phase of the first wave; a prospective longitudinal seroepidemiological study

Background: Health-care workers are at risk of contracting and transmitting SARS-CoV-2. The aim of this study was to investigate the prevalence of SARS-CoV-2 IgG antibodies and the rate of seroconversion in an environment with high exposure to SARS-CoV-2. Methods: 131 health-care workers at the Department of Infectious Diseases in Västerås, Sweden, were included in the study. Abbott's SARS-COV-2 IgG immunoassay was used with a signal cut-off ratio of ≥1.4. Every third week from the beginning of May, blood samples were drawn, and the participants completed a questionnaire regarding symptoms consistent with COVID-19 and the result of any SARS-CoV-2 PCR performed since the last sampling occasion. Participants with IgG antibodies against SARS-CoV-2 were re-sampled only on the sixth and last occasion. Results: At the start of the study, 18 (15%) participants had SARS-CoV-2 IgG antibodies. At the end, 25 (19%) of 131 participants were seropositive. One case of asymptomatic infection was detected, and two cases with PCR-confirmed COVID-19 did not develop IgG antibodies. Conclusion: The low rate of seroconversion during the study suggests that it is possible to prevent transmission of SARS-COV-2 in a high-exposure environment. Compliance with adequate infection control guidelines is the likely explanation of our findings.

Paths taken towards NK cell-mediated immunotherapy of human cancer-a personal reflection

The discovery that NK cells are able to specifically recognize cells lacking the expression of self‐MHC class I molecules provided the first insight into NK cell recognition of tumour cells. It started a flourishing field of NK cell research aimed at exploring the molecular nature of NK cell receptors involved in tumour cell recognition. While much of the important early work was conducted in murine experimental model systems, studies of human NK cells rapidly followed. Over the years, human NK cell research has swiftly progressed, aided by new detailed molecular information on human NK cell development, differentiation, molecular specificity, tissue heterogeneity and functional capacity. NK cells have also been studied in many different diseases aside from cancer, including viral diseases, autoimmunity, allergy and primary immunodeficiencies. These fields of research have all, indirectly or directly, provided further insights into NK cell‐mediated recognition of target cells and paved the way for the development of NK cell‐based immunotherapies for human cancer. Excitingly, NK cell‐based immunotherapy now opens up for novel strategies aimed towards treating malignant diseases, either alone or in combination with other drugs. Reviewed here are some personal reflections of select contributions leading up to the current state‐of‐the‐art in the field, with a particular emphasis on contributions from our own laboratory. This review is part of a series of articles on immunology in Scandinavia, published in conjunction with the 50th anniversary of the Scandinavian Society for Immunology.

Virology, epidemiology, immunology and vaccine development of SARS-CoV-2, update after nine months of pandemic

This International Alliance for Biological Standardization COVID-19 webinar was organized to provide an update on the virology, epidemiology and immunology of, and the vaccine development for SARS-CoV-2, none months after COVID-19 was declared a public health emergency of international concern. It brought together a broad range of international stakeholders, including academia, regulators, funders and industry, with a considerable delegation from low- and middle-income countries.

SARS-CoV-2 Antibody Responses Are Correlated to Disease Severity in COVID-19 Convalescent Individuals

Globally, the COVID-19 pandemic has had extreme consequences for the healthcare system and has led to calls for diagnostic tools to monitor and understand the transmission, pathogenesis, and epidemiology, as well as to evaluate future vaccination strategies. In this study, we have developed novel, to our knowledge, flexible ELISA-based assays for specific detection of human SARS-CoV-2 Abs against the receptor-binding domain, including an Ag sandwich ELISA relevant for large population screening and three isotype-specific assays for in-depth diagnostics. Their performance was evaluated in a cohort of 350 convalescent participants with previous COVID-19 infection, ranging from asymptomatic to critical cases. We mapped the Ab responses to different areas on protein N and S and showed that the IgM, A, and G Ab responses against receptor-binding domain are significantly correlated to the disease severity. These assays and the data generated from them are highly relevant for diagnostics and prognostics and contribute to the understanding of long-term COVID-19 immunity.

Unbiased Screens Show CD8+ T Cells of COVID-19 Patients Recognize Shared Epitopes in SARS-CoV-2 that Largely Reside outside the Spike Protein

Developing effective strategies to prevent or treat coronavirus disease 2019 (COVID-19) requires understanding the natural immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We used an unbiased, genome-wide screening technology to determine the precise peptide sequences in SARS-CoV-2 that are recognized by the memory CD8+ T cells of COVID-19 patients. In total, we identified 3-8 epitopes for each of the 6 most prevalent human leukocyte antigen (HLA) types. These epitopes were broadly shared across patients and located in regions of the virus that are not subject to mutational variation. Notably, only 3 of the 29 shared epitopes were located in the spike protein, whereas most epitopes were located in ORF1ab or the nucleocapsid protein. We also found that CD8+ T cells generally do not cross-react with epitopes in the four seasonal coronaviruses that cause the common cold. Overall, these findings can inform development of next-generation vaccines that better recapitulate natural CD8+ T cell immunity to SARS-CoV-2.

Orthogonal SARS-CoV-2 Serological Assays Enable Surveillance of Low-Prevalence Communities and Reveal Durable Humoral Immunity

We conducted a serological study to define correlates of immunity against SARS-CoV-2. Compared to those with mild coronavirus disease 2019 (COVID-19) cases, individuals with severe disease exhibited elevated virus-neutralizing titers and antibodies against the nucleocapsid (N) and the receptor binding domain (RBD) of the spike protein. Age and sex played lesser roles. All cases, including asymptomatic individuals, seroconverted by 2 weeks after PCR confirmation. Spike RBD and S2 and neutralizing antibodies remained detectable through 5-7 months after onset, whereas α-N titers diminished. Testing 5,882 members of the local community revealed only 1 sample with seroreactivity to both RBD and S2 that lacked neutralizing antibodies. This fidelity could not be achieved with either RBD or S2 alone. Thus, inclusion of multiple independent assays improved the accuracy of antibody tests in low-seroprevalence communities and revealed differences in antibody kinetics depending on the antigen. We conclude that neutralizing antibodies are stably produced for at least 5-7 months after SARS-CoV-2 infection.

SARS-CoV-2 immunity: review and applications to phase 3 vaccine candidates

Understanding immune responses to severe acute respiratory syndrome coronavirus 2 is crucial to understanding disease pathogenesis and the usefulness of bridge therapies, such as hyperimmune globulin and convalescent human plasma, and to developing vaccines, antivirals, and monoclonal antibodies. A mere 11 months ago, the canvas we call COVID-19 was blank. Scientists around the world have worked collaboratively to fill in this blank canvas. In this Review, we discuss what is currently known about human humoral and cellular immune responses to severe acute respiratory syndrome coronavirus 2 and relate this knowledge to the COVID-19 vaccines currently in phase 3 clinical trials.

Characterization of pre-existing and induced SARS-CoV-2-specific CD8+ T cells

Emerging data indicate that SARS-CoV-2-specific CD8⁺ T cells targeting different viral proteins are detectable in up to 70% of convalescent individuals^1-5. However, very little information is currently available about the abundance, phenotype, functional capacity and fate of pre-existing and induced SARS-CoV-2-specific CD8⁺ T cell responses during the natural course of SARS-CoV-2 infection. Here, we define a set of optimal and dominant SARS-CoV-2-specific CD8⁺ T cell epitopes. We also perform a high-resolution ex vivo analysis of pre-existing and induced SARS-CoV-2-specific CD8⁺ T cells, applying peptide-loaded major histocompatibility complex class I (pMHCI) tetramer technology. We observe rapid induction, prolonged contraction and emergence of heterogeneous and functionally competent cross-reactive and induced memory CD8⁺ T cell responses in cross-sectionally analyzed individuals with mild disease following SARS-CoV-2 infection and three individuals longitudinally assessed for their T cells pre- and post-SARS-CoV-2 infection. SARS-CoV-2-specific memory CD8⁺ T cells exhibited functional characteristics comparable to influenza-specific CD8⁺ T cells and were detectable in SARS-CoV-2 convalescent individuals who were seronegative for anti-SARS-CoV-2 antibodies targeting spike (S) and nucleoprotein (N). These results define cross-reactive and induced SARS-CoV-2-specific CD8⁺ T cell responses as potentially important determinants of immune protection in mild SARS-CoV-2 infection.

SARS-CoV-2 antibody prevalence in health care workers: Preliminary report of a single center study

Serological surveys have been conducted to establish prevalence for COVID-19 antibodies in various cohorts and communities, reporting a wide range of outcomes. The prevalence of such antibodies among healthcare workers, presumed at higher risk for infection, has been increasingly investigated, more studies are needed to better understand the risks and infection transmission in different healthcare settings. The present study reports on initial sero-surveillance conducted on healthcare workers at a regional hospital system in Orange County, California, during May and June, 2020. Study subjects were recruited from the entire hospital employee workforce and the independent medical staff. Data were collected for job duties and locations, COVID-19 symptoms, a PCR test history, travel record since January 2020, and existence of household contacts with COVID-19. A blood sample was collected from each subject for serum analysis for IgG antibodies to SARS-CoV-2. Of 2,992 tested individuals, a total 2,924 with complete data were included in the analysis. Observed prevalence of 1.06% (31 antibody positive cases), adjusted prevalence of 1.13% for test sensitivity and specificity were identified. Significant group differences between positive vs. negative were observed for age (z = 2.65, p = .008), race (p = .037), presence of fever (p < .001), and loss of smell (p < .001), but not for occupations (p = .710). Possible explanation for this low prevalence includes a relatively low local geographic community prevalence (~4.4%) at the time of testing, the hospital's timely procurement of personal protective equipment, rigorous employee education, patient triage, and treatment protocol development and implementation. In addition, cross-reactive adaptive T cell mediated immunity, as recently described, may possibly play a greater role in healthcare workers than in the general population.

Antigen-Specific Adaptive Immunity to SARS-CoV-2 in Acute COVID-19 and Associations with Age and Disease Severity

Limited knowledge is available on the relationship between antigen-specific immune responses and COVID-19 disease severity. We completed a combined examination of all three branches of adaptive immunity at the level of SARS-CoV-2-specific CD4+ and CD8+ T cell and neutralizing antibody responses in acute and convalescent subjects. SARS-CoV-2-specific CD4+ and CD8+ T cells were each associated with milder disease. Coordinated SARS-CoV-2-specific adaptive immune responses were associated with milder disease, suggesting roles for both CD4+ and CD8+ T cells in protective immunity in COVID-19. Notably, coordination of SARS-CoV-2 antigen-specific responses was disrupted in individuals ≥ 65 years old. Scarcity of naive T cells was also associated with aging and poor disease outcomes. A parsimonious explanation is that coordinated CD4+ T cell, CD8+ T cell, and antibody responses are protective, but uncoordinated responses frequently fail to control disease, with a connection between aging and impaired adaptive immune responses to SARS-CoV-2.

Pathogenesis-directed therapy of 2019 novel coronavirus disease

The 2019 novel coronavirus disease (COVID-19) now is considered a global public health emergency. One of the unprecedented challenges is defining the optimal therapy for those patients with severe pneumonia and systemic manifestations of COVID-19. The optimal therapy should be largely based on the pathogenesis of infections caused by this novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Since the onset of COVID-19, there have been many prepublications and publications reviewing the therapy of COVID-19 as well as many prepublications and publications reviewing the pathogenesis of SARS-CoV-2. However, there have been no comprehensive reviews that link COVID-19 therapies to the pathogenic mechanisms of SARS-CoV-2. To link COVID-19 therapies to pathogenic mechanisms of SARS-CoV-2, we performed a comprehensive search through MEDLINE, PubMed, medRxiv, EMBASE, Scopus, Google Scholar, and Web of Science using the following keywords: COVID-19, SARS-CoV-2, novel 2019 coronavirus, pathology, pathologic, pathogenesis, pathophysiology, coronavirus pneumonia, coronavirus infection, coronavirus pulmonary infection, coronavirus cardiovascular infection, coronavirus gastroenteritis, coronavirus autopsy findings, viral sepsis, endotheliitis, thrombosis, coagulation abnormalities, immunology, humeral immunity, cellular immunity, inflammation, cytokine storm, superantigen, therapy, treatment, therapeutics, immune-based therapeutics, antiviral agents, respiratory therapy, oxygen therapy, anticoagulation therapy, adjuvant therapy, and preventative therapy. Opinions expressed in this review also are based on personal experience as clinicians, authors, peer reviewers, and editors. This narrative review linking COVID-19 therapies with pathogenic mechanisms of SARS-CoV-2 has resulted in six major therapeutic goals for COVID-19 therapy based on the pathogenic mechanisms of SARS-CoV-2. These goals are listed below: 1. The first goal is identifying COVID-19 patients that require both testing and therapy. This is best accomplished with a COVID-19 molecular test from symptomatic patients as well as determining the oxygen saturation in such patients with a pulse oximeter. Whether a symptomatic respiratory illness is COVID-19, influenza, or another respiratory pathogen, an oxygen saturation less than 90% means that the patient requires medical assistance. 2. The second goal is to correct the hypoxia. This goal generally requires hospitalization for oxygen therapy; other respiratory-directed therapies such as prone positioning or mechanical ventilation are often used in the attempt to correct hypoxemia due to COVID-19. 3. The third goal is to reduce the viral load of SARS-CoV-2. Ideally, there would be an oral antiviral agent available such as seen with the use of oseltamivir phosphate for influenza. This oral antiviral agent should be taken early in the course of SARS-CoV-2 infection. Such an oral agent is not available yet. Currently, two options are available for reducing the viral load of SARS-CoV-2. These are post-Covid-19 plasma with a high neutralizing antibody titer against SARS-CoV-2 or intravenous remdesivir; both options require hospitalization. 4. The fourth goal is to identify and address the hyperinflammation phase often seen in hospitalized COVID-19 patients. Currently, fever with an elevated C-reactive protein is useful for diagnosing this hyperinflammation syndrome. Low-dose dexamethasone therapy currently is the best therapeutic approach. 5. The fifth goal is to identify and address the hypercoagulability phase seen in many hospitalized COVID-19 patients. Patients who would benefit from anticoagulation therapy can be identified by a marked increase in d-dimer and prothrombin time with a decrease in fibrinogen. To correct this disseminated intravascular coagulation-like phase, anticoagulation therapy with low molecular weight heparin is preferred. Anticoagulation therapy with unfractionated heparin is preferred in COVID-19 patients with acute kidney injuries. 6. The last goal is prophylaxis for persons who are not yet infected. Potential supplements include vitamin D and zinc. Although the data for such supplements is not extremely strong, it can be argued that almost 50% of the population worldwide has a vitamin D deficiency. Correcting this deficiency would be beneficial regardless of any impact of COVID-19. Similarly, zinc is an important supplement that is important in one's diet regardless of any effect on SARS-CoV-2. As emerging therapies are found to be more effective against the SARS-CoV-2 pathogenic mechanisms identified, they can be substituted for those therapies presented in this review.

Cell-mediated and humoral adaptive immune responses to SARS-CoV-2 are lower in asymptomatic than symptomatic COVID-19 patients

The characterization of cell-mediated and humoral adaptive immune responses to SARS-CoV-2 is fundamental to understand COVID-19 progression and the development of immunological memory to the virus. In this study, we detected T-cells reactive to SARS-CoV-2 proteins M, S, and N, as well as serum virus-specific IgM, IgA, IgG, in nearly all SARS-CoV-2 infected individuals, but not in healthy donors. Virus-reactive T cells exhibited signs of in vivo activation, as suggested by the surface expression of immune-checkpoint molecules PD1 and TIGIT. Of note, we detected antigen-specific adaptive immune response both in asymptomatic and symptomatic SARS-CoV-2 infected subjects. More importantly, symptomatic patients displayed a significantly higher magnitude of both cell-mediated and humoral adaptive immune response to the virus, as compared to asymptomatic individuals. These findings suggest that an uncontrolled adaptive immune response contribute to the development of the life-threatening inflammatory phase of the disease. Finally, this study might open the way to develop effective vaccination strategies.

SARS-CoV-2 and mitochondrial health: implications of lifestyle and ageing

Infection with SARs-COV-2 displays increasing fatality with age and underlying co-morbidity, in particular, with markers of the metabolic syndrome and diabetes, which seems to be associated with a "cytokine storm" and an altered immune response. This suggests that a key contributory factor could be immunosenescence that is both age-related and lifestyle-induced. As the immune system itself is heavily reliant on mitochondrial function, then maintaining a healthy mitochondrial system may play a key role in resisting the virus, both directly, and indirectly by ensuring a good vaccine response. Furthermore, as viruses in general, and quite possibly this new virus, have also evolved to modulate immunometabolism and thus mitochondrial function to ensure their replication, this could further stress cellular bioenergetics. Unlike most sedentary modern humans, one of the natural hosts for the virus, the bat, has to "exercise" regularly to find food, which continually provides a powerful adaptive stimulus to maintain functional muscle and mitochondria. In effect the bat is exposed to regular hormetic stimuli, which could provide clues on how to resist this virus. In this paper we review the data that might support the idea that mitochondrial health, induced by a healthy lifestyle, could be a key factor in resisting the virus, and for those people who are perhaps not in optimal health, treatments that could support mitochondrial function might be pivotal to their long-term recovery.

Distinct antibody responses to SARS-CoV-2 in children and adults across the COVID-19 clinical spectrum

Clinical manifestations of COVID-19 caused by the new coronavirus SARS-CoV-2 are associated with age^1,2. Adults develop respiratory symptoms, which can progress to acute respiratory distress syndrome (ARDS) in the most severe form, while children are largely spared from respiratory illness but can develop a life-threatening multisystem inflammatory syndrome (MIS-C)^3-5. Here, we show distinct antibody responses in children and adults after SARS-CoV-2 infection. Adult COVID-19 cohorts had anti-spike (S) IgG, IgM and IgA antibodies, as well as anti-nucleocapsid (N) IgG antibody, while children with and without MIS-C had reduced breadth of anti-SARS-CoV-2-specific antibodies, predominantly generating IgG antibodies specific for the S protein but not the N protein. Moreover, children with and without MIS-C had reduced neutralizing activity as compared to both adult COVID-19 cohorts, indicating a reduced protective serological response. These results suggest a distinct infection course and immune response in children independent of whether they develop MIS-C, with implications for developing age-targeted strategies for testing and protecting the population.

Convalescent Plasma against COVID-19: A Broad-Spectrum Therapeutic Approach for Emerging Infectious Diseases

In the lack of an effective vaccine and antiviral treatment, convalescent plasma (CP) has been a promising therapeutic approach in past pandemics. Accumulating evidence in the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic corroborates the safety of CP therapy and preliminary data underline the potential efficacy. Recently, the Food and Drug Administration (FDA) permitted CP therapy for coronavirus disease 2019 (COVID-19) patients under the emergency use authorization, albeit additional clinical studies are still needed. The imminent threat of a second or even multiple waves of COVID-19 has compelled health authorities to delineate and calibrate a feasible preparedness algorithm for deploying CP as an immediate therapeutic intervention. The success of preparedness programs depends on the interdisciplinary actions of multiple actors in politics, science, and healthcare. In this review, we evaluate the current status of CP therapy for COVID-19 patients and address the challenges that confront the implementation of CP. Finally, we propose a pandemic preparedness framework for future waves of the COVID-19 pandemic and unknown pathogen outbreaks.

Epitope similarity cannot explain the pre-formed T cell immunity towards structural SARS-CoV-2 proteins

The current pandemic is caused by the SARS-CoV-2 virus and large progress in understanding the pathology of the virus has been made since its emergence in late 2019. Several reports indicate short lasting immunity against endemic coronaviruses, which contrasts studies showing that biobanked venous blood contains T cells reactive to SARS-CoV-2 S-protein even before the outbreak in Wuhan. This suggests a preformed T cell memory towards structural proteins in individuals not exposed to SARS-CoV-2. Given the similarity of SARS-CoV-2 to other members of the Coronaviridae family, the endemic coronaviruses appear likely candidates to generate this T cell memory. However, given the apparent poor immunological memory created by the endemic coronaviruses, immunity against other common pathogens might offer an alternative explanation. Here, we utilize a combination of epitope prediction and similarity to common human pathogens to identify potential sources of the SARS-CoV-2 T cell memory. Although beta-coronaviruses are the most likely candidates to explain the pre-existing SARS-CoV-2 reactive T cells in uninfected individuals, the SARS-CoV-2 epitopes with the highest similarity to those from beta-coronaviruses are confined to replication associated proteins-not the host interacting S-protein. Thus, our study suggests that the observed SARS-CoV-2 pre-formed immunity to structural proteins is not driven by near-identical epitopes.

The COVID-19 pandemic through eyes of a NYC fertility center: a unique learning experience with often unexpected results

Affecting basic tenets of human existence such as health, economic as well as personal security and, of course, reproduction, the COVID-19 pandemic transcended medical specialties and professional disciplines. Yet, six months into the pandemic, there still exists no consensus on how to combat the virus in absence of a vaccine. Facing unprecedented circumstances, and in absence of real evidence on how to proceed, our organization early in the pandemic decided to act independently from often seemingly irrational guidance and, instead, to carefully follow a quickly evolving COVID-19 literature. Here described is the, likely, unique journey of a fertility center that maintained services during peaks of COVID-19 and political unrest that followed. Closely following publicly available data, we recognized relatively early that New York City and other East Coast regions, which during the initial COVID-19 wave between March and May represented the hardest-hit areas in the country, during the second wave, beginning in June and still in progress, remained almost completely unaffected. In contrast, south western regions, almost completely unaffected by the initial wave, were severely affected in the second wave. These two distinctively different infectious phenotypes suggested two likely explanations: The country was witnessing infections with two different SARS-CoV-2 viruses and NYC (along with the East Coast) acquired during the first wave much better immunity to the virus than south western regions. Both hypotheses since have been confirmed: East and West Coasts, indeed, were initially infected by two distinctively different lineages of the virus, with the East Coast lineage being 10-times more infectious. In addition, immunologists discovered an up to this point unknown long-term anti-viral innate (cellular) immune response which offers additional and much broader anti-viral immunity than the classical adaptive immunity via immobilizing antibodies that has been known for decades. Consequently, we predict that in the U.S., even in absence of an available vaccine, COVID-19, by September-October, will be at similarly low levels as are currently seen in NYC and other East Coast regions (generally < 1% test-positivity). We, furthermore, predict that, if current mitigation measures are maintained and no newly aggressive mutation of the virus enters the country, a significant fall-wave of COVID-19, in combination with the usual fall wave of influenza, appears unlikely. To continue serving patients uninterrupted throughout the pandemic, turned for all of our center's staff into a highly rewarding experience, garnered respect and appreciation from patients, and turned into an absolutely unique learning experience.

Rapid, simplified whole blood-based multiparameter assay to quantify and phenotype SARS-CoV-2 specific T cells

Rapid tests to evaluate SARS-CoV-2-specific T cell responses are urgently needed to decipher protective immunity and aid monitoring vaccine-induced immunity. Using a rapid whole blood assay requiring minimal amount of blood, we measured qualitatively and quantitatively SARS-CoV-2-specific CD4 T cell responses in 31 healthcare workers, using flow cytometry. 100% of COVID-19 convalescent participants displayed a detectable SARS-CoV-2-specific CD4 T cell response. SARS-CoV-2-responding cells were also detected in 40.9% of participants with no COVID-19-associated symptoms or who tested PCR negative. Phenotypic assessment indicated that, in COVID-19 convalescent participants, SARS-CoV-2 CD4 responses displayed an early differentiated memory phenotype with limited capacity to produce IFNγ. Conversely, in participants with no reported symptoms, SARS-CoV-2 CD4 responses were enriched in late differentiated cells, co-expressing IFNγ and TNFα and also Granzyme B. This proof of concept study presents a scalable alternative to PBMC-based assays to enumerate and phenotype SARS-CoV-2-responding T cells, thus representing a practical tool to monitor adaptive immunity in vaccine trials.

Summary

In this proof of concept study, we show that SARS-CoV-2 T cell responses are easily detectable using a rapid whole blood assay requiring minimal blood volume. Such assay could represent a suitable tool to monitor adaptive immunity in vaccine trials.

[Telemedicine follow-ups for COVID-19: Experience in a tertiary hospital]

INTRODUCTION

Telemedicine is an attractive option for the follow-up of paediatric patients with SARS-CoV-2 infection. The aim of this article is to describe the experience with telephone consultations in a tertiary hospital.

PATIENTS AND METHODS

Retrospective descriptive study of children with confirmed or probable diagnosis of COVID-19 attended by telephone consultations in Hospital La Paz (Madrid) between March and June 2020. Patients were referred from the Emergency Department after being discharged from the hospital. Telephone consultations were made every 48hours until symptoms resolved, then weekly until completing 14 days without symptoms.

RESULTS

A total of 72 children were included, with median age of 83.5 months (IQR=16.3-157.5). Of those 46 (63.9%) were male, and 14 (19.4%) had comorbidities. There were 32 (44.4%) hospital admissions. COVID-19 diagnosis was confirmed in 33 children by RT-PCR, and in 7 by serology tests. The seroconversion rate was 67.7% in those patients with a positive RT-PCR. Other infections were found in 7 patients (5 Mycoplasma pneumoniae, 1 parvovirus, and 1 cytomegalovirus). Median symptom duration was 25.5 days (IQR=13.8-37), while median follow-up duration was 28 days (IQR=21-39). The median number of telephone consultations per patient was 6 (IQR=4-8). Clinical worsening was reported in 19 (26.4%) during follow-up, and 14 (19.4%) were re-evaluated in the Emergency Department. One patient required hospital admission, but he had a favourable outcome.

CONCLUSIONS

Children with suspected SARS-CoV-2 infection should be followed-up due to prolonged duration of symptoms, and the risk of clinical deterioration. Telephone consultations are a useful and safe alternative for the follow-up of patients with mild symptoms, and for children discharged from the hospital.

What could explain the late emergence of COVID-19 in Africa?

At the end of November 2019, a novel coronavirus responsible for respiratory tract infections emerged in China. Despite drastic containment measures, this virus, known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), spread in Asia and Europe. The pandemic is ongoing with a particular hotspot in southern Europe and America in spring 2020. Many studies predicted an epidemic in Africa similar to that currently seen in Europe and the USA. However, reported data do not confirm these predictions. Several hypotheses that could explain the later emergence and spread of the coronavirus disease 2019 (COVID-19) pandemic in African countries are being discussed, including the lack of health-care infrastructure capable of clinically detecting and confirming COVID-19 cases, the implementation of social distancing and hygiene, international air traffic flows, the climate, the relatively young and rural population, the genetic polymorphism of the angiotensin-converting enzyme 2 receptor, cross-immunity and the use of antimalarial drugs.

Coronavirus disease 2019 population-based prevalence, risk factors, hospitalization, and fatality rates in southern Brazil

OBJECTIVES

To assess population-based prevalence, risk factors, hospitalization, and infection fatality rates (IFR) associated with COVID-19.

METHODS

We conducted two household surveys among the non-institutionalized adult population from May 30 to June 17, 2020, in Lajeado, an 84,000-inhabitant industrial city in southern Brazil. Primary outcome was prevalence of SARS-CoV-2 infection. Secondary outcomes were COVID-19-related hospitalizations and deaths occurring up to June 20, 2020. We summarized prevalence rates across surveys with meta-analysis. We assessed age-range IFR and hospitalization rate and regressed these rates over age strata using nonlinear (exponential) coefficients of determination (R2).

RESULTS

Summarized overall prevalence was 3.40% (95% CI, 2.74-4.18), 34% lower in older adults ≥60 years. Prevalence was 14.3 and 5.4 times higher among household contacts and meat-precessing plant (MPP) workers, respectively. IFR ranged from 0.08% (0.06-0.11) to 4.63% (2.93-7.84) in individuals 20-39 years and ≥60 years, respectively. R2 for hospitalization rate and IFR over age were 0.98 and 0.93 (both p-values <0.0001), respectively.

CONCLUSIONS

This is the first population-based study in Brazil to estimate COVID-19 prevalence, hospitalization, and fatality rates per age stratum. Rates were largely age-dependent. Household contacts and MPP workers are at higher risk of infection. Our findings are valuable for health-policy making and resource allocation to mitigate the pandemic.

Evaluation of the rate of COVID-19 infection, hospitalization and death among Iranian patients with multiple sclerosis

BACKGROUND

COVID-19 is increasingly expanding all over the world. People who have an underlying disease or taking immunosuppressive drugs are generally more likely to be infected than the others. Multiple sclerosis (MS) patients may also be at risk of the disease and its complications depending on the medication they are taking. In this study, we evaluated a large population of patients with MS with different disease modifying drugs to show if any of them increases the risk. In addition, this study evaluates the incidence of COVID-19 in patients with MS, the rate of hospitalization or death in these patients.

METHOD

This study was performed at the MS Clinic of Sina Hospital. All patients were contacted and their demographic characteristics were recorded. They were then asked about their COVID-19 symptoms. Patients with these symptoms were further evaluated. The documents were reviewed by treating neurologist and MS nurses to be sure about diagnosis of COVID19. The positive polymerase chain reaction (PCR) result or compatible lung computed tomography (CT) scan was acceptable for COVID-19 diagnosis.

RESULTS

4647 patients answered the phone contact. Of these, 68 were infected with the COVID-19. The rate of hospitalization was 25% which is far more than general population. Two patients died from COVID-19. Rituximab was associated with increase rate of COVID-19 infection but not with hospitalization rate. There was no significant correlation between use of other drugs and rate of infection.

CONCLUSION

This study revealed that the incidence of COVID-19 in MS patients is not more than general population, but the risk of hospitalization in these patients is higher than estimated for the disease. This highlights the importance of communicating to patients the severity of COVID-19 and the importance of risk reduction behaviors like social distancing and mask use.

Understanding the complexities of SARS-CoV2 infection and its immunology: A road to immune-based therapeutics

Emerging infectious diseases always pose a threat to humans along with plant and animal life. SARS-CoV2 is the recently emerged viral infection that originated from Wuhan city of the Republic of China in December 2019. Now, it has become a pandemic. Currently, SARS-CoV2 has infected more than 27.74 million people worldwide, and taken 901,928 human lives. It was named first 'WH 1 Human CoV' and later changed to 2019 novel CoV (2019-nCoV). Scientists have established it as a zoonotic viral disease emerged from Chinese horseshoe bats, which do not develop a severe infection. For example, Rhinolophus Chinese horseshoe bats harboring severe acute respiratory syndrome-related coronavirus (SARSr-CoV) or SARSr-Rh-BatCoV appear healthy and clear the virus within 2-4 months period. The article introduces first the concept of EIDs and some past EIDs, which have affected human life. Next section discusses mysteries regarding SARS-CoV2 origin, its evolution, and human transfer. Third section describes COVID-19 clinical symptoms and factors affecting susceptibility or resistance. The fourth section introduces the SARS-CoV2 entry in the host cell, its replication, and the establishment of productive infection. Section five describes the host's immune response associated with asymptomatic, symptomatic, mild to moderate, and severe COVID-19. The subsequent seventh and eighth sections mention the immune status in COVID-19 convalescent patients and re-emergence of COVID-19 in them. Thereafter, the eighth section describes viral strategies to hijack the host antiviral immune response and generate the "cytokine storm". The ninth section describes about transgenic humane ACE2 (hACE2) receptor expressing mice to study immunity, drugs, and vaccines. The article ends with the development of different immunomodulatory and immunotherapeutics strategies, including vaccines waiting for their approval in humans as prophylaxis or treatment measures.

Antibody Responses to SARS-CoV-2: Let's Stick to Known Knowns

The scale of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has thrust immunology into the public spotlight in unprecedented ways. In this article, which is part opinion piece and part review, we argue that the normal cadence by which we discuss science with our colleagues failed to properly convey likelihoods of the immune response to SARS-CoV-2 to the public and the media. As a result, biologically implausible outcomes were given equal weight as the principles set by decades of viral immunology. Unsurprisingly, questionable results and alarmist news media articles have filled the void. We suggest an emphasis on setting expectations based on prior findings while avoiding the overused approach of assuming nothing. After reviewing Ab-mediated immunity after coronavirus and other acute viral infections, we posit that, with few exceptions, the development of protective humoral immunity of more than a year is the norm. Immunity to SARS-CoV-2 is likely to follow the same pattern.

Vaccines for COVID-19

Since the emergence of COVID-19, caused by the SARS-CoV-2 virus at the end of 2019, there has been an explosion of vaccine development. By 24 September 2020, a staggering number of vaccines (more than 200) had started preclinical development, of which 43 had entered clinical trials, including some approaches that have not previously been licensed for human vaccines. Vaccines have been widely considered as part of the exit strategy to enable the return to previous patterns of working, schooling and socializing. Importantly, to effectively control the COVID-19 pandemic, production needs to be scaled-up from a small number of preclinical doses to enough filled vials to immunize the world's population, which requires close engagement with manufacturers and regulators. It will require a global effort to control the virus, necessitating equitable access for all countries to effective vaccines. This review explores the immune responses required to protect against SARS-CoV-2 and the potential for vaccine-induced immunopathology. We describe the profile of the different platforms and the advantages and disadvantages of each approach. The review also addresses the critical steps between promising preclinical leads and manufacturing at scale. The issues faced during this pandemic and the platforms being developed to address it will be invaluable for future outbreak control. Nine months after the outbreak began we are at a point where preclinical and early clinical data are being generated for the vaccines; an overview of this important area will help our understanding of the next phases.

Cross-reactive memory T cells and herd immunity to SARS-CoV-2

Immunity is a multifaceted phenomenon. For T cell-mediated memory responses to SARS-CoV-2, it is relevant to consider their impact both on COVID-19 disease severity and on viral spread in a population. Here, we reflect on the immunological and epidemiological aspects and implications of pre-existing cross-reactive immune memory to SARS-CoV-2, which largely originates from previous exposure to circulating common cold coronaviruses. We propose four immunological scenarios for the impact of cross-reactive CD4+ memory T cells on COVID-19 severity and viral transmission. For each scenario, we discuss its implications for the dynamics of herd immunity and on projections of the global impact of SARS-CoV-2 on the human population, and assess its plausibility. In sum, we argue that key potential impacts of cross-reactive T cell memory are already incorporated into epidemiological models based on data of transmission dynamics, particularly with regard to their implications for herd immunity. The implications of immunological processes on other aspects of SARS-CoV-2 epidemiology are worthy of future study.

Broad and strong memory CD4+ and CD8+ T cells induced by SARS-CoV-2 in UK convalescent individuals following COVID-19

The development of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines and therapeutics will depend on understanding viral immunity. We studied T cell memory in 42 patients following recovery from COVID-19 (28 with mild disease and 14 with severe disease) and 16 unexposed donors, using interferon-γ-based assays with peptides spanning SARS-CoV-2 except ORF1. The breadth and magnitude of T cell responses were significantly higher in severe as compared with mild cases. Total and spike-specific T cell responses correlated with spike-specific antibody responses. We identified 41 peptides containing CD4+ and/or CD8+ epitopes, including six immunodominant regions. Six optimized CD8+ epitopes were defined, with peptide-MHC pentamer-positive cells displaying the central and effector memory phenotype. In mild cases, higher proportions of SARS-CoV-2-specific CD8+ T cells were observed. The identification of T cell responses associated with milder disease will support an understanding of protective immunity and highlights the potential of including non-spike proteins within future COVID-19 vaccine design.

COVID-19 vaccine-readiness for anti-CD20-depleting therapy in autoimmune diseases

Although most autoimmune diseases are considered to be CD4 T cell- or antibody-mediated, many respond to CD20-depleting antibodies that have limited influence on CD4 and plasma cells. This includes rituximab, oblinutuzumab and ofatumumab that are used in cancer, rheumatoid arthritis and off-label in a large number of other autoimmunities and ocrelizumab in multiple sclerosis. Recently, the COVID-19 pandemic created concerns about immunosuppression in autoimmunity, leading to cessation or a delay in immunotherapy treatments. However, based on the known and emerging biology of autoimmunity and COVID-19, it was hypothesised that while B cell depletion should not necessarily expose people to severe SARS-CoV-2-related issues, it may inhibit protective immunity following infection and vaccination. As such, drug-induced B cell subset inhibition, that controls at least some autoimmunities, would not influence innate and CD8 T cell responses, which are central to SARS-CoV-2 elimination, nor the hypercoagulation and innate inflammation causing severe morbidity. This is supported clinically, as the majority of SARS-CoV-2-infected, CD20-depleted people with autoimmunity have recovered. However, protective neutralizing antibody and vaccination responses are predicted to be blunted until naive B cells repopulate, based on B cell repopulation kinetics and vaccination responses, from published rituximab and unpublished ocrelizumab (NCT00676715, NCT02545868) trial data, shown here. This suggests that it may be possible to undertake dose interruption to maintain inflammatory disease control, while allowing effective vaccination against SARS-CoV-29, if and when an effective vaccine is available.

Mathematical Models for COVID-19 Pandemic: A Comparative Analysis

COVID-19 pandemic represents an unprecedented global health crisis in the last 100 years. Its economic, social and health impact continues to grow and is likely to end up as one of the worst global disasters since the 1918 pandemic and the World Wars. Mathematical models have played an important role in the ongoing crisis; they have been used to inform public policies and have been instrumental in many of the social distancing measures that were instituted worldwide. In this article, we review some of the important mathematical models used to support the ongoing planning and response efforts. These models differ in their use, their mathematical form and their scope.