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

Seroprevalence of SARS-CoV-2 Binding and Neutralizing Antibodies in Healthcare Workers during the Epidemic Peak in Referral Hospitals and Quarantine Sites: Saudi Arabia

Healthcare workers (HCWs) are at high risk for SARS-CoV-2 infection compared to the general population. Here, we aimed to evaluate and characterize the SARS-CoV-2 seropositivity rate in randomly collected samples among HCWs from the largest referral hospitals and quarantine sites during the peak of the COVID-19 epidemic in the city of Jeddah, the second largest city in Saudi Arabia, using a cross-sectional analytic study design. Out of 693 participants recruited from 29 June to 10 August 2020, 223 (32.2%, 95% CI: 28.8–35.8) were found to be confirmed seropositive for SARS-CoV-2 antibodies, and among those 197 (88.3%) had never been diagnosed with COVID-19. Seropositivity was not significantly associated with participants reporting COVID-19 compatible symptoms as most seropositive HCW participants 140 (62.8%) were asymptomatic. The large proportion of asymptomatic SARS-CoV-2 cases detected in our study demands periodic testing as a general hospital policy.

Impact of SARS-CoV-2 variants on the total CD4+ and CD8+ T cell reactivity in infected or vaccinated individuals

The emergence of SARS-CoV-2 variants with evidence of antibody escape highlight the importance of addressing whether the total CD4+ and CD8+ T cell recognition is also affected. Here, we compare SARS-CoV-2-specific CD4+ and CD8+ T cells against the B.1.1.7, B.1.351, P.1, and CAL.20C lineages in COVID-19 convalescents and in recipients of the Moderna (mRNA-1273) or Pfizer/BioNTech (BNT162b2) COVID-19 vaccines. The total reactivity against SARS-CoV-2 variants is similar in terms of magnitude and frequency of response, with decreases in the 10%-22% range observed in some assay/VOC combinations. A total of 7% and 3% of previously identified CD4+ and CD8+ T cell epitopes, respectively, are affected by mutations in the various VOCs. Thus, the SARS-CoV-2 variants analyzed here do not significantly disrupt the total SARS-CoV-2 T cell reactivity; however, the decreases observed highlight the importance for active monitoring of T cell reactivity in the context of SARS-CoV-2 evolution.

Subacute SARS-CoV-2 replication can be controlled in the absence of CD8+ T cells in cynomolgus macaques

SARS-CoV-2 infection presents clinical manifestations ranging from asymptomatic to fatal respiratory failure. Despite the induction of functional SARS-CoV-2-specific CD8⁺ T-cell responses in convalescent individuals, the role of virus-specific CD8⁺ T-cell responses in the control of SARS-CoV-2 replication remains unknown. In the present study, we show that subacute SARS-CoV-2 replication can be controlled in the absence of CD8⁺ T cells in cynomolgus macaques. Eight macaques were intranasally inoculated with 10⁵ or 10⁶ TCID₅₀ of SARS-CoV-2, and three of the eight macaques were treated with a monoclonal anti-CD8 antibody on days 5 and 7 post-infection. In these three macaques, CD8⁺ T cells were undetectable on day 7 and thereafter, while virus-specific CD8⁺ T-cell responses were induced in the remaining five untreated animals. Viral RNA was detected in nasopharyngeal swabs for 10–17 days post-infection in all macaques, and the kinetics of viral RNA levels in pharyngeal swabs and plasma neutralizing antibody titers were comparable between the anti-CD8 antibody treated and untreated animals. SARS-CoV-2 RNA was detected in the pharyngeal mucosa and/or retropharyngeal lymph node obtained at necropsy on day 21 in two of the untreated group but undetectable in all macaques treated with anti-CD8 antibody. CD8⁺ T-cell responses may contribute to viral control in SARS-CoV-2 infection, but our results indicate possible containment of subacute viral replication in the absence of CD8⁺ T cells, implying that CD8⁺ T-cell dysfunction may not solely lead to viral control failure.

SARS-CoV-2 infection presents a wide spectrum of clinical manifestations ranging from asymptomatic to fatal respiratory failure. The determinants for failure in viral control and/or fatal disease progression have not been elucidated fully. Both acquired immune effectors, antibodies and CD8⁺ T cells, are considered to contribute to viral control. However, it remains unknown whether a deficiency in either of these two arms is directly linked to failure in the control of SARS-CoV-2 replication. In the present study, to know the requirement of CD8⁺ T cells for viral control after the establishment of infection, we examined the effect of CD8⁺ cell depletion by monoclonal anti-CD8 antibody administration in the subacute phase on SARS-CoV-2 replication in cynomolgus macaques. Unexpectedly, our analysis revealed no significant impact of CD8⁺ cell depletion on viral replication, indicating that subacute SARS-CoV-2 replication can be controlled in the absence of CD8⁺ T cells. CD8⁺ T-cell responses may contribute to viral control in SARS-CoV-2 infection, but this study suggests that CD8⁺ T-cell dysfunction may not solely lead to viral control failure or fatal disease progression.

Influence of HLA Class II Polymorphism on Predicted Cellular Immunity Against SARS-CoV-2 at the Population and Individual Level

Development of adaptive immunity after COVID-19 and after vaccination against SARS-CoV-2 is predicated on recognition of viral peptides, presented on HLA class II molecules, by CD4+ T-cells. We capitalised on extensive high-resolution HLA data on twenty five human race/ethnic populations to investigate the role of HLA polymorphism on SARS-CoV-2 immunogenicity at the population and individual level. Within populations, we identify wide inter-individual variability in predicted peptide presentation from structural, non-structural and accessory SARS-CoV-2 proteins, according to individual HLA genotype. However, we find similar potential for anti-SARS-CoV-2 cellular immunity at the population level suggesting that HLA polymorphism is unlikely to account for observed disparities in clinical outcomes after COVID-19 among different race/ethnic groups. Our findings provide important insight on the potential role of HLA polymorphism on development of protective immunity after SARS-CoV-2 infection and after vaccination and a firm basis for further experimental studies in this field.

SARS-CoV-2-specific circulating T follicular helper cells correlate with neutralizing antibodies and increase during early convalescence

T-cell immunity is likely to play a role in protection against SARS-CoV-2 by helping generate neutralizing antibodies. We longitudinally studied CD4 T-cell responses to the M, N, and S structural proteins of SARS-CoV-2 in 26 convalescent individuals. Within the first two months following symptom onset, a majority of individuals (81%) mounted at least one CD4 T-cell response, and 48% of individuals mounted detectable SARS-CoV-2-specific circulating T follicular helper cells (cTfh, defined as CXCR5⁺PD1⁺ CD4 T cells). SARS-CoV-2-specific cTfh responses across all three protein specificities correlated with antibody neutralization with the strongest correlation observed for S protein-specific responses. When examined over time, cTfh responses, particularly to the M protein, increased in convalescence, and robust cTfh responses with magnitudes greater than 5% were detected at the second convalescent visit, a median of 38 days post-symptom onset. CD4 T-cell responses declined but persisted at low magnitudes three months and six months after symptom onset. These data deepen our understanding of antigen-specific cTfh responses in SARS-CoV-2 infection, suggesting that in addition to S protein, M and N protein-specific cTfh may also assist in the development of neutralizing antibodies and that cTfh response formation may be delayed in SARS-CoV-2 infection.

Since December 2019, the Coronavirus Disease 2019 (COVID-19) pandemic has caused significant morbidity and mortality worldwide. Recently approved vaccines against SARS-CoV-2 are understood to protect against infection by inducing neutralizing antibodies. However, the underlying immune responses necessary for protection remain unclear. It is well established that T follicular helper cells (Tfh), a subset of CD4 T cells, are essential to the development of neutralizing antibodies and that some of these cells, called circulating T follicular helper cells (cTfh), can be studied in the blood. Not much is known about Tfh responses mounted in SARS-CoV-2 infection. Here, we studied cTfh responses to three major structural proteins in individuals recovered from COVID-19. We find that SARS-CoV-2-specific cTfh frequencies correlate with neutralizing antibody responses. We also find that cTfh responses to SARS-CoV-2 increase well into convalescence before contracting. Our results suggest that cTfh responses against proteins other than the spike protein may contribute to the development of neutralizing antibodies and that the formation of cTfh responses in SARS-CoV-2 infection may be delayed.

MiRNA Profiling in Plasma and Placenta of SARS-CoV-2-Infected Pregnant Women

MicroRNAs are gene expression regulators associated with several human pathologies, including those generated by viral infections. Their role in SARS-CoV-2 infection and COVID-19 has been investigated and reviewed in many informative studies; however, a thorough miRNA outline in SARS-CoV-2-infected pregnant women (SIPW), at both systemic and placental levels, is missing. To fill this gap, blood and placenta biopsies collected at delivery from 15 asymptomatic SIPW were immediately analysed for: miRNA expression (n = 84) (QPCR array), antiviral/immune mRNA target expression (n = 74) (QGene) and cytokine/chemokines production (n = 27) (Multiplex ELISA). By comparing these results with those obtained from six uninfected pregnant women (UPW), we observed that, following SARS-CoV-2 infection, the transcriptomic profile of pregnant women is significantly altered in different anatomical districts, even in the absence of clinical symptoms and vertical transmission. This characteristic combination of miRNA and antiviral/immune factors seems to control both the infection and the dysfunctional immune reaction, thus representing a positive correlate of protection and a potential therapeutic target against SARS-CoV-2.

Insights into Pathology and Pathogenesis of Coronavirus Disease 2019 from a Histopathological and Immunological Perspective

Since the first case of COVID-19 was reported in Wuhan, China, in December 2019, the SARS-CoV-2 epidemic has spread all over the world and has become a significant public health issue. The development of treatments for COVID-19 is currently in progress; however, their effects remain limited, and the development of more effective therapeutics is desired. Thus, sufficient understanding of the pathophysiology of COVID-19 is essential to develop effective therapeutics for this disease. Pathological analyses in particular play an important role to demonstrate the causal link between an infectious disease and the pathogen and elucidate the mechanism of pathogenesis. As per pathological analyses to date, respiratory organs are identified as the major affected organs in most COVID-19 cases; also, various lesions were noted in other organs. Further, there have been increasing reports that show that the immune responses of the host contribute to the deterioration of the pathological condition of COVID-19, and a novel concept of MIS-C/MIS-A is also being established. Thus, in this article, we have provided an overview of the pathology of COVID-19 from a histopathological and immunological perspective focusing on the mechanisms of COVID-19 pathogenesis.

A single dose of the SARS-CoV-2 vaccine BNT162b2 elicits Fc-mediated antibody effector functions and T cell responses

While the standard regimen of the BNT162b2 mRNA vaccine for SARS-CoV-2 includes two doses administered 3 weeks apart, some public health authorities are spacing these doses, raising concerns about efficacy. However, data indicate that a single dose can be up to 90% effective starting 14 days post-administration. To assess the mechanisms contributing to protection, we analyzed humoral and T cell responses three weeks after a single BNT162b2 dose. We observed weak neutralizing activity elicited in SARS-CoV-2 naive individuals but strong anti-receptor binding domain and spike antibodies with Fc-mediated effector functions and cellular CD4+ T cell responses. In previously infected individuals, a single dose boosted all humoral and T cell responses, with strong correlations between T helper and antibody immunity. Our results highlight the potential role of Fc-mediated effector functions and T cell responses in vaccine efficacy. They also provide support for spacing doses to vaccinate more individuals in conditions of vaccine scarcity.

T-cell mediated immunity after AZD1222 vaccination: A polyfunctional spike-specific Th1 response with a diverse TCR repertoire

AZD1222 (ChAdOx1 nCoV-19), a replication-deficient simian adenovirus-vectored vaccine, has demonstrated safety, efficacy, and immunogenicity against coronavirus disease 2019 (COVID-19) in clinical trials and real-world studies. We characterized CD4+ and CD8+ T-cell responses induced by AZD1222 vaccination in peripheral blood mononuclear cells (PBMCs) from 280 unique vaccine recipients aged 18-85 years who enrolled in the phase 2/3 COV002 trial. Total spike-specific CD4+ T cell helper type 1 (Th1) and CD8+ T-cell responses were significantly increased in AZD1222-vaccinated adults of all ages following two doses of AZD1222. CD4+ Th2 responses following AZD1222 vaccination were not detected. Furthermore, AZD1222-specific Th1 and CD8+ T cells both displayed a high degree of polyfunctionality in all adult age groups. T-cell receptor (TCR) β sequences from vaccinated participants mapped against TCR sequences known to react to SARS-CoV-2 revealed substantial breadth and depth across the SARS-CoV-2 spike protein for the AZD1222-induced CD4+ and CD8+ T-cell responses. Overall, AZD1222 vaccination induced a robust, polyfunctional Th1-dominated T-cell response, with broad CD4+ and CD8+ T-cell coverage across the SARS-CoV-2 spike protein.

One Sentence Summary

Polyfunctional CD4+ and CD8+ T-cell responses are elicited against the SARS-CoV-2 spike protein following vaccination with AZD1222.

Impaired Priming of SARS-CoV-2-Specific Naive CD8+ T Cells in Older Subjects

Advanced age is associated with severe symptoms and death upon SARS-CoV-2 infection. Virus-specific CD8⁺ T-cell responses have shown to be protective toward critical COVID-19 manifestations, suggesting that suboptimal cellular immunity may contribute to the age-pattern of the disease. The induction of a CD8⁺ T-cell response against an emerging pathogen like SARS-CoV-2 relies on the activation of naive T cells. To investigate whether the primary CD8⁺ T-cell response against this virus is defective in advanced age, we used an in vitro approach to prime SARS-CoV-2-specific naive CD8⁺ T cells from healthy, unexposed donors of different age groups. Compared to younger adults, older individuals display a poor SARS-CoV-2-specific T-cell priming capacity in terms of both magnitude and quality of the response. In addition, older subjects recognize a lower number of epitopes. Our results implicate that immune aging is associated with altered primary SARS-CoV-2-specific CD8⁺ T-cell responses.

Surviving older patients show preserved cellular and humoral immunological memory several months after SARS-CoV-2 infection

Understanding how older people respond to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is critical if we are to confront the coronavirus disease 2019 (COVID-19) pandemic and establish effective vaccination strategies. Immunosenescence reduces the ability to respond to neoantigens and may compromise the life of infected individuals. Here, we analyzed the immunological memory to SARS-CoV-2 in 102 recovered patients aged over 60 years several months after the infection had been resolved. Specific memory T lymphocytes against the virus were measured by interferon-γ (IFN-γ) and granzyme B release by ELISpot; memory B-lymphocyte responses were quantified by detection of anti-S IgG1 producer cells by ELISpot and anti-S and anti-N antibodies were determined by enzyme-linked immunosorbent assay (ELISA). Memory T lymphocytes were found in peripheral blood of most of the studied donors, more than 7 months after the infection in some of them. Fewer patients maintained memory B lymphocytes, but antibodies, mainly anti-S, were highly durable and positively correlated with T responses. More robust humoral responses were found in patients who had more severe symptoms and had been admitted to hospital. We concluded that specific immunity against SARS-CoV-2 is effectively preserved regardless of age, despite the great heterogeneity of their immune responses, and that memory T lymphocytes and anti-S IgG might be more durable than memory B cells and anti-N IgG.

Immune Signature Linked to COVID-19 Severity: A SARS-Score for Personalized Medicine

SARS-CoV-2 infection leads to a highly variable clinical evolution, ranging from asymptomatic to severe disease with acute respiratory distress syndrome, requiring intensive care units (ICU) admission. The optimal management of hospitalized patients has become a worldwide concern and identification of immune biomarkers predictive of the clinical outcome for hospitalized patients remains a major challenge. Immunophenotyping and transcriptomic analysis of hospitalized COVID-19 patients at admission allow identifying the two categories of patients. Inflammation, high neutrophil activation, dysfunctional monocytic response and a strongly impaired adaptive immune response was observed in patients who will experience the more severe form of the disease. This observation was validated in an independent cohort of patients. Using in silico analysis on drug signature database, we identify differential therapeutics that specifically correspond to each group of patients. From this signature, we propose a score-the SARS-Score-composed of easily quantifiable biomarkers, to classify hospitalized patients upon arrival to adapt treatment according to their immune profile.

Short Telomeres and a T-Cell Shortfall in COVID-19: The Aging Effect

The slow pace of global vaccination and the rapid emergence of SARS-CoV-2 variants suggest recurrent waves of COVID-19 in coming years. Therefore, understanding why deaths from COVID-19 are highly concentrated among older adults is essential for global health. Severe COVID-19 T-cell lymphopenia is more common among older adults, and it entails poor prognosis. Much about the primary etiology of this form of lymphopenia remains unknown, but regardless of its causes, offsetting the decline in T-cell count during SARS-CoV-2 infection demands fast and massive T-cell clonal expansion, which is telomere length (TL)-dependent. We have built a model that captures the effect of age-dependent TL shortening in hematopoietic cells and its effect on T-cell clonal expansion capacity. The model shows that an individual with average hematopoietic cell TL (HCTL) at age twenty years maintains maximal T-cell clonal expansion capacity until the 6th decade of life when this capacity plummets by more than 90% over the next ten years. The collapse coincides with the steep increase in COVID-19 mortality with age. HCTL metrics may thus explain the vulnerability of older adults to COVID-19. That said, the wide inter-individual variation in HCTL across the general population means that some younger adults with inherently short HCTL might be at risk of severe COVID-19 lymphopenia and mortality from the disease.

Vaccination of cancer patients against COVID-19: towards the end of a dilemma

With the emergence of second wave of COVID-19 infection globally, particularly in India in March-April 2021, protection by massive vaccination drive has become the need of the hour. Vaccines have been proved to reduce the risk of developing severe illness and are emerging as vital tools in the battle against COVID-19. As per the GLOBOCAN database, nearly 19.3 million new cancer cases have been reported in 2020 globally, which posed a significant challenge to health care providers to protect such large number of 'vulnerable' patients from COVID-19. Nevertheless, a considerable degree of doubt, hesitancy and misconceptions are noted regarding the administration of vaccines particularly during active immuno-suppressant treatment. This review article highlights the added vulnerability of cancer patients to the COVID-19 infection and has explored the immunological challenges associated with malignancy, anticancer treatment and COVID-19 vaccination.

SARS-CoV-2-specific immune response in COVID-19 convalescent individuals

We collected blood from coronavirus disease 2019 (COVID-19) convalescent individuals and investigated SARS-CoV-2-specific humoral and cellular immunity in these discharged patients. Follow-up analysis in a cohort of 171 patients at 4-11 months after the onset revealed high levels of IgG antibodies. A total of 78.1% (164/210) of the specimens tested positive for neutralizing antibody (NAb). SARS-CoV-2 antigen peptide pools-stimulated-IL-2 and -IFN-γ response can distinguish COVID-19 convalescent individuals from healthy donors. Interestingly, NAb survival was significantly affected by the antigen peptide pools-stimulated-IL-2 response, -IL-8 response, and -IFN-γ response. The antigen peptide pools-activated CD8+ T cell counts were correlated with NAb. The antigen peptide pools-activated natural killer (NK) cell counts in convalescent individuals were correlated with NAb and disease severity. Our data suggested that the development of NAb is associated with the activation of T cells and NK cells. Our work provides a basis for further analysis of the protective immunity to SARS-CoV-2 and for understanding the pathogenesis of COVID-19. It also has implications for the development of an effective vaccine for SARS-CoV-2 infection.

[The corona pandemic and multiple sclerosis: vaccinations and their implications for patients-Part 1: recommendations]

The ongoing COVID-19 pandemic is a global health crisis. New challenges are constantly emerging especially for the healthcare system, not least with the emergence of various viral mutations. Given the variety of immunomodulatory and immunosuppressive therapies for multiple sclerosis (MS) and the immense developments in vaccine production, there is a high need of information for people with MS. The aim of this article is therefore to provide an overview of MS and COVID-19 as well as to clarify the implications for patients with MS, especially regarding vaccination and to formulate appropriate recommendations.

Effect of Bamlanivimab vs Placebo on Incidence of COVID-19 Among Residents and Staff of Skilled Nursing and Assisted Living Facilities: A Randomized Clinical Trial

IMPORTANCE

Preventive interventions are needed to protect residents and staff of skilled nursing and assisted living facilities from COVID-19 during outbreaks in their facilities. Bamlanivimab, a neutralizing monoclonal antibody against SARS-CoV-2, may confer rapid protection from SARS-CoV-2 infection and COVID-19.

OBJECTIVE

To determine the effect of bamlanivimab on the incidence of COVID-19 among residents and staff of skilled nursing and assisted living facilities.

DESIGN, SETTING, AND PARTICIPANTS

Randomized, double-blind, single-dose, phase 3 trial that enrolled residents and staff of 74 skilled nursing and assisted living facilities in the United States with at least 1 confirmed SARS-CoV-2 index case. A total of 1175 participants enrolled in the study from August 2 to November 20, 2020. Database lock was triggered on January 13, 2021, when all participants reached study day 57.

INTERVENTIONS

Participants were randomized to receive a single intravenous infusion of bamlanivimab, 4200 mg (n = 588), or placebo (n = 587).

MAIN OUTCOMES AND MEASURES

The primary outcome was incidence of COVID-19, defined as the detection of SARS-CoV-2 by reverse transcriptase-polymerase chain reaction and mild or worse disease severity within 21 days of detection, within 8 weeks of randomization. Key secondary outcomes included incidence of moderate or worse COVID-19 severity and incidence of SARS-CoV-2 infection.

RESULTS

The prevention population comprised a total of 966 participants (666 staff and 300 residents) who were negative at baseline for SARS-CoV-2 infection and serology (mean age, 53.0 [range, 18-104] years; 722 [74.7%] women). Bamlanivimab significantly reduced the incidence of COVID-19 in the prevention population compared with placebo (8.5% vs 15.2%; odds ratio, 0.43 [95% CI, 0.28-0.68]; P < .001; absolute risk difference, -6.6 [95% CI, -10.7 to -2.6] percentage points). Five deaths attributed to COVID-19 were reported by day 57; all occurred in the placebo group. Among 1175 participants who received study product (safety population), the rate of participants with adverse events was 20.1% in the bamlanivimab group and 18.9% in the placebo group. The most common adverse events were urinary tract infection (reported by 12 participants [2%] who received bamlanivimab and 14 [2.4%] who received placebo) and hypertension (reported by 7 participants [1.2%] who received bamlanivimab and 10 [1.7%] who received placebo).

CONCLUSIONS AND RELEVANCE

Among residents and staff in skilled nursing and assisted living facilities, treatment during August-November 2020 with bamlanivimab monotherapy reduced the incidence of COVID-19 infection. Further research is needed to assess preventive efficacy with current patterns of viral strains with combination monoclonal antibody therapy.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04497987.

SARS-CoV-2-specific humoral and cellular immunity persists through 9 months irrespective of COVID-19 severity at hospitalisation

OBJECTIVES

Humoral and cellular immunity to SARS-CoV-2 following COVID-19 will likely contribute to protection from reinfection or severe disease. It is therefore important to characterise the initiation and persistence of adaptive immunity to SARS-CoV-2 amidst the ongoing pandemic.

METHODS

Here, we conducted a longitudinal study on hospitalised moderate and severe COVID-19 patients from the acute phase of disease into convalescence at 5 and 9 months post-symptom onset. Utilising flow cytometry, serological assays as well as B cell and T cell FluoroSpot assays, we assessed the magnitude and specificity of humoral and cellular immune responses during and after human SARS-CoV-2 infection.

RESULTS

During acute COVID-19, we observed an increase in germinal centre activity, a substantial expansion of antibody-secreting cells and the generation of SARS-CoV-2-neutralising antibodies. Despite gradually decreasing antibody levels, we show persistent, neutralising antibody titres as well as robust specific memory B cell responses and polyfunctional T cell responses at 5 and 9 months after symptom onset in both moderate and severe COVID-19 patients.

CONCLUSION

Our findings describe the initiation and, importantly, persistence of cellular and humoral SARS-CoV-2-specific immunological memory in hospitalised COVID-19 patients long after recovery, likely contributing towards protection against reinfection.

Temporal maturation of neutralizing antibodies in COVID-19 convalescent individuals improves potency and breadth to circulating SARS-CoV-2 variants

Antibody titers against SARS-CoV-2 slowly wane over time. Here, we examined how time affects antibody potency. To assess the impact of antibody maturation on durable neutralizing activity against original SARS-CoV-2 and emerging variants of concern (VOCs), we analyzed receptor binding domain (RBD)-specific IgG antibodies in convalescent plasma taken 1-10 months after SARS-CoV-2 infection. Longitudinal evaluation of total RBD IgG and neutralizing antibody revealed declining total antibody titers but improved neutralization potency per antibody to original SARS-CoV-2, indicative of antibody response maturation. Neutralization assays with authentic viruses revealed that early antibodies capable of neutralizing original SARS-CoV-2 had limited reactivity toward B.1.351 (501Y.V2) and P.1 (501Y.V3) variants. Antibodies from late convalescents exhibited increased neutralization potency to VOCs, suggesting persistence of cross-neutralizing antibodies in plasma. Thus, maturation of the antibody response to SARS-CoV-2 potentiates cross-neutralizing ability to circulating variants, suggesting that declining antibody titers may not be indicative of declining protection.

Differential T-Cell Reactivity to Endemic Coronaviruses and SARS-CoV-2 in Community and Health Care Workers

Herein we measured CD4+ T-cell responses against common cold coronaviruses (CCC) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in high-risk health care workers (HCW) and community controls. We observed higher levels of CCC-reactive T cells in SARS-CoV-2-seronegative HCW compared to community donors, consistent with potential higher occupational exposure of HCW to CCC. We further show that SARS-CoV-2 T-cell reactivity of seronegative HCW was higher than community controls and correlation between CCC and SARS-CoV-2 responses is consistent with cross-reactivity and not associated with recent in vivo activation. Surprisingly, CCC T-cell reactivity was decreased in SARS-CoV-2-infected HCW, suggesting that exposure to SARS-CoV-2 might interfere with CCC responses, either directly or indirectly. This result was unexpected, but consistently detected in independent cohorts derived from Miami and San Diego. CD4+ T-cell responses against common cold coronaviruses (CCC) are elevated in SARS-CoV-2 seronegative high-risk health care workers (HCW) compared to COVID-19 convalescent HCW, suggesting that exposure to SARS-CoV-2 might interfere with CCC responses and/or cross-reactivity associated with a protective effect.

CD8+ T cells contribute to survival in patients with COVID-19 and hematologic cancer

Patients with cancer have high mortality from coronavirus disease 2019 (COVID-19), and the immune parameters that dictate clinical outcomes remain unknown. In a cohort of 100 patients with cancer who were hospitalized for COVID-19, patients with hematologic cancer had higher mortality relative to patients with solid cancer. In two additional cohorts, flow cytometric and serologic analyses demonstrated that patients with solid cancer and patients without cancer had a similar immune phenotype during acute COVID-19, whereas patients with hematologic cancer had impairment of B cells and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibody responses. Despite the impaired humoral immunity and high mortality in patients with hematologic cancer who also have COVID-19, those with a greater number of CD8 T cells had improved survival, including those treated with anti-CD20 therapy. Furthermore, 77% of patients with hematologic cancer had detectable SARS-CoV-2-specific T cell responses. Thus, CD8 T cells might influence recovery from COVID-19 when humoral immunity is deficient. These observations suggest that CD8 T cell responses to vaccination might provide protection in patients with hematologic cancer even in the setting of limited humoral responses.

Neutralizing antibody levels are highly predictive of immune protection from symptomatic SARS-CoV-2 infection

Predictive models of immune protection from COVID-19 are urgently needed to identify correlates of protection to assist in the future deployment of vaccines. To address this, we analyzed the relationship between in vitro neutralization levels and the observed protection from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection using data from seven current vaccines and from convalescent cohorts. We estimated the neutralization level for 50% protection against detectable SARS-CoV-2 infection to be 20.2% of the mean convalescent level (95% confidence interval (CI) = 14.4-28.4%). The estimated neutralization level required for 50% protection from severe infection was significantly lower (3% of the mean convalescent level; 95% CI = 0.7-13%, P = 0.0004). Modeling of the decay of the neutralization titer over the first 250 d after immunization predicts that a significant loss in protection from SARS-CoV-2 infection will occur, although protection from severe disease should be largely retained. Neutralization titers against some SARS-CoV-2 variants of concern are reduced compared with the vaccine strain, and our model predicts the relationship between neutralization and efficacy against viral variants. Here, we show that neutralization level is highly predictive of immune protection, and provide an evidence-based model of SARS-CoV-2 immune protection that will assist in developing vaccine strategies to control the future trajectory of the pandemic.

SARS-CoV-2 viremia is associated with distinct proteomic pathways and predicts COVID-19 outcomes

BACKGROUNDSARS-CoV-2 plasma viremia has been associated with severe disease and death in COVID-19 in small-scale cohort studies. The mechanisms behind this association remain elusive.METHODSWe evaluated the relationship between SARS-CoV-2 viremia, disease outcome, and inflammatory and proteomic profiles in a cohort of COVID-19 emergency department participants. SARS-CoV-2 viral load was measured using a quantitative reverse transcription PCR-based platform. Proteomic data were generated with Proximity Extension Assay using the Olink platform.RESULTSThis study included 300 participants with nucleic acid test-confirmed COVID-19. Plasma SARS-CoV-2 viremia levels at the time of presentation predicted adverse disease outcomes, with an adjusted OR of 10.6 (95% CI 4.4-25.5, P < 0.001) for severe disease (mechanical ventilation and/or 28-day mortality) and 3.9 (95% CI 1.5-10.1, P = 0.006) for 28-day mortality. Proteomic analyses revealed prominent proteomic pathways associated with SARS-CoV-2 viremia, including upregulation of SARS-CoV-2 entry factors (ACE2, CTSL, FURIN), heightened markers of tissue damage to the lungs, gastrointestinal tract, and endothelium/vasculature, and alterations in coagulation pathways.CONCLUSIONThese results highlight the cascade of vascular and tissue damage associated with SARS-CoV-2 plasma viremia that underlies its ability to predict COVID-19 disease outcomes.FUNDINGMark and Lisa Schwartz; the National Institutes of Health (U19AI082630); the American Lung Association; the Executive Committee on Research at Massachusetts General Hospital; the Chan Zuckerberg Initiative; Arthur, Sandra, and Sarah Irving for the David P. Ryan, MD, Endowed Chair in Cancer Research; an EMBO Long-Term Fellowship (ALTF 486-2018); a Cancer Research Institute/Bristol Myers Squibb Fellowship (CRI2993); the Harvard Catalyst/Harvard Clinical and Translational Science Center (National Center for Advancing Translational Sciences, NIH awards UL1TR001102 and UL1TR002541-01); and by the Harvard University Center for AIDS Research (National Institute of Allergy and Infectious Diseases, 5P30AI060354).

Centenarians and extremely old people living with frailty can elicit durable SARS-CoV-2 spike specific IgG antibodies with virus neutralization functions following virus infection as determined by serological study

BACKGROUND

The SARS-CoV-2 (Severe Acute Respiratory Syndrome coronavirus 2) has led to more than 165 million COVID-19 cases and >3.4 million deaths worldwide. Epidemiological analysis has revealed that the risk of developing severe COVID-19 increases with age. Despite a disproportionate number of older individuals and long-term care facilities being affected by SARS-CoV-2 and COVID-19, very little is understood about the immune responses and development of humoral immunity in the extremely old person after SARS-CoV-2 infection. Here we conducted a serological study to investigate the development of humoral immunity in centenarians following a SARS-CoV-2 outbreak in a long-term care facility.

METHODS

Extreme aged individuals and centenarians who were residents in a long-term care facility and infected with or exposed to SARS-CoV-2 were investigated between April and June 2020 for the development of antibodies to SARS-CoV-2. Blood samples were collected from positive and bystander individuals 30 and 60 days after original diagnosis of SARS-CoV-2 infection. Plasma was used to quantify IgG, IgA, and IgM isotypes and subsequent subclasses of antibodies specific for SARS-CoV-2 spike protein. The function of anti-spike was then assessed by virus neutralization assays against the native SARS-CoV-2 virus.

FINDINGS

Fifteen long-term care residents were investigated for SARS-CoV-2 infection. All individuals had a Clinical Frailty scale score ≥5 and were of extreme older age or were centenarians. Six women with a median age of 98.8 years tested positive for SARS-CoV-2. Anti-spike IgG antibody titers were the highest titers observed in our cohort with all IgG positive individuals having virus neutralization ability. Additionally, 5 out of the 6 positive participants had a robust IgA anti-SARS-CoV-2 response. In all 5, antibodies were detected after 60 days from initial diagnosis.

Durability of Immunity to SARS-CoV-2 and Other Respiratory Viruses

Even in nonpandemic times, respiratory viruses account for a vast global burden of disease. They remain a major cause of illness and death and they pose a perpetual threat of breaking out into epidemics and pandemics. Many of these respiratory viruses infect repeatedly and appear to induce only narrow transient immunity, but the situation varies from one virus to another. In the absence of effective specific treatments, understanding the role of immunity in protection, disease, and resolution is of paramount importance. These problems have been brought into sharp focus by the coronavirus disease 2019 (COVID-19) pandemic. Here, we summarise what is now known about adaptive immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and draw comparisons with immunity to other respiratory viruses, focusing on the longevity of protective responses.

RIG-I triggers a signaling-abortive anti-SARS-CoV-2 defense in human lung cells

Efficient immune responses against viral infection are determined by sufficient activation of nucleic acid sensor-mediated innate immunity1,2. Coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains an ongoing global pandemic. It is an urgent challenge to clarify the innate recognition mechanism to control this virus. Here we show that retinoic acid-inducible gene-I (RIG-I) sufficiently restrains SARS-CoV-2 replication in human lung cells in a type I/III interferon (IFN)-independent manner. RIG-I recognizes the 3' untranslated region of the SARS-CoV-2 RNA genome via the helicase domains, but not the C-terminal domain. This new mode of RIG-I recognition does not stimulate its ATPase, thereby aborting the activation of the conventional mitochondrial antiviral-signaling protein-dependent pathways, which is in accordance with lack of cytokine induction. Nevertheless, the interaction of RIG-I with the viral genome directly abrogates viral RNA-dependent RNA polymerase mediation of the first step of replication. Consistently, genetic ablation of RIG-I allows lung cells to produce viral particles that expressed the viral spike protein. By contrast, the anti-SARS-CoV-2 activity was restored by all-trans retinoic acid treatment through upregulation of RIG-I protein expression in primary lung cells derived from patients with chronic obstructive pulmonary disease. Thus, our findings demonstrate the distinctive role of RIG-I as a restraining factor in the early phase of SARS-CoV-2 infection in human lung cells.

COVID-19 optimal vaccination policies: A modeling study on efficacy, natural and vaccine-induced immunity responses

About a year into the pandemic, COVID-19 accumulates more than two million deaths worldwide. Despite non-pharmaceutical interventions such as social distance, mask-wearing, and restrictive lockdown, the daily confirmed cases remain growing. Vaccine developments from Pfizer, Moderna, and Gamaleya Institute reach more than 90% efficacy and sustain the vaccination campaigns in multiple countries. However, natural and vaccine-induced immunity responses remain poorly understood. There are great expectations, but the new SARS-CoV-2 variants demand to inquire if the vaccines will be highly protective or induce permanent immunity. Further, in the first quarter of 2021, vaccine supply is scarce. Consequently, some countries that are applying the Pfizer vaccine will delay its second required dose. Likewise, logistic supply, economic and political implications impose a set of grand challenges to develop vaccination policies. Therefore, health decision-makers require tools to evaluate hypothetical scenarios and evaluate admissible responses. Following some of the WHO-SAGE recommendations, we formulate an optimal control problem with mixed constraints to describe vaccination schedules. Our solution identifies vaccination policies that minimize the burden of COVID-19 quantified by the number of disability-adjusted years of life lost. These optimal policies ensure the vaccination coverage of a prescribed population fraction in a given time horizon and preserve hospitalization occupancy below a risk level. We explore "via simulation" plausible scenarios regarding efficacy, coverage, vaccine-induced, and natural immunity. Our simulations suggest that response regarding vaccine-induced immunity and reinfection periods would play a dominant role in mitigating COVID-19.

How to interpret and use COVID-19 serology and immunology tests

BACKGROUND

Although molecular tests are considered the reference standard for coronavirus disease 2019 (COVID-19) diagnostics, serological and immunological tests may be useful in specific settings.

OBJECTIVES

This review summarizes the underlying principles and performance of COVID-19 serological and immunological testing.

SOURCES

Selected peer-reviewed publications on COVID-19 related serology and immunology published between December 2019 and March 2021.

CONTENT

Serological tests are highly specific but heterogeneous in their sensitivity for the diagnosis of COVID-19. For certain indications, including delayed disease presentations, serological tests can have added value. The presence of antibodies against SARS-CoV-2 may indicate a recent or past COVID-19 infection. Lateral flow immunoassay (LFIA) antibody tests have the advantages of being easy and fast to perform, but many have a low sensitivity in acute settings. Enzyme-linked immunosorbent assay (ELISA) and chemiluminescence immunoassays (CLIAs) have higher sensitivities. Besides humoral immunity, cellular immunity is also essential for successful host defences against viruses. Enzyme-linked immunospot (ELISpot) assays can be used to measure T-cell responses against SARS-CoV-2. The presence of cross-reactive SARS-CoV-2-specific T cells in never exposed patients suggests the possibility of cellular immunity induced by other circulating coronaviruses. T-cell responses against SARS-CoV-2 have also been detected in recovered COVID-19 patients with no detectable antibodies.

IMPLICATIONS

Serological and immunological tests are primarily applied for population-based seroprevalence studies to evaluate the effectiveness of COVID-19 control measures and increase our understanding of the immunology behind COVID-19. Combining molecular diagnostics with serological tests may optimize the detection of COVID-19. As not all infected patients will develop antibodies against SARS-CoV-2, assessment of cellular immunity may provide complementary information on whether a patient has been previously infected with COVID-19. More studies are needed to understand the correlations of these serological and immunological parameters with protective immunity, taking into account the different circulating virus variants.

Toward Understanding COVID-19 Recovery: National Institutes of Health Workshop on Postacute COVID-19

Over the past year, the SARS-CoV-2 pandemic has swept the globe, resulting in an enormous worldwide burden of infection and mortality. However, the additional toll resulting from long-term consequences of the pandemic has yet to be tallied. Heterogeneous disease manifestations and syndromes are now recognized among some persons after their initial recovery from SARS-CoV-2 infection, representing in the broadest sense a failure to return to a baseline state of health after acute SARS-CoV-2 infection. On 3 to 4 December 2020, the National Institute of Allergy and Infectious Diseases, in collaboration with other Institutes and Centers of the National Institutes of Health, convened a virtual workshop to summarize existing knowledge on postacute COVID-19 and to identify key knowledge gaps regarding this condition.

Low Innate Immunity and Lagged Adaptive Immune Response in the Re-Tested Viral RNA Positivity of a COVID-19 Patient

Recent studies have highlighted observations regarding re-tested positivity (RP) of SARS-CoV-2 RNA in discharged COVID-19 patients, however, the immune mechanisms underlying SARS-CoV-2 RNA RP in immunocompetent patients remain elusive. Herein, we describe the case of an immunocompetent COVID-19 patient with moderate symptoms who was twice re-tested as positive for SARS-CoV-2 RNA, and the period between first and third viral RNA positivity was 95 days, longer than previously reported (18–25 days). The chest computed tomography findings, plasma anti-SARS-CoV-2 antibody, neutralizing antibodies (NAbs) titer, and whole blood transcriptic characteristics in the viral RNA RP patient and other COVID-19 patients were analyzed. During the SARS-CoV-2 RNA RP period, new lung lesions were observed. The COVID-19 patient with viral RNA RP had delayed seroconversion of anti-spike/receptor-binding domain (RBD) IgA antibody and NAbs and were accompanied with disappearance of the lung lesions. Further experimental data validated that NAbs titer was significantly associated with anti-RBD IgA and IgG, and anti-spike IgG. The RP patient had lower interferon-, T cells- and B cell-related genes expression than non-RP patients with mild-to-moderate symptoms, and displayed lower cytokines and chemokines gene expression than severe patients. Interestingly, the RP patient had low expression of antigen presentation-related genes and low B cell counts which might have contributed to the delayed anti-RBD specific antibody and low CD8+ cell response. Collectively, delayed antigen presentation-related gene expression was found related to delayed adaptive immune response and contributed to the SARS-CoV-2 RNA RP in this described immunocompetent patient.

Network Topology of Biological Aging and Geroscience-Guided Approaches to COVID-19

Aging has emerged as the greatest and most prevalent risk factor for the development of severe COVID-19 infection and death following exposure to the SARS-CoV-2 virus. The presence of multiple co-existing chronic diseases and conditions of aging further enhances this risk. Biological aging not only enhances the risk of chronic diseases, but the presence of such conditions further accelerates varied biological processes or "hallmarks" implicated in aging. Given growing evidence that it is possible to slow the rate of many biological aging processes using pharmacological compounds has led to the proposal that such geroscience-guided interventions may help enhance immune resilience and improve outcomes in the face of SARS-CoV-2 infection. Our review of the literature indicates that most, if not all, hallmarks of aging may contribute to the enhanced COVID-19 vulnerability seen in frail older adults. Moreover, varied biological mechanisms implicated in aging do not function in isolation from each other, and exhibit intricate effects on each other. With all of these considerations in mind, we highlight limitations of current strategies mostly focused on individual single mechanisms, and we propose an approach which is far more multidisciplinary and systems-based emphasizing network topology of biological aging and geroscience-guided approaches to COVID-19.

COVID-19: immunopathology, pathophysiological mechanisms, and treatment options

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to spread globally despite the worldwide implementation of preventive measures to combat the disease. Although most COVID-19 cases are characterised by a mild, self-limiting disease course, a considerable subset of patients develop a more severe condition, varying from pneumonia and acute respiratory distress syndrome (ARDS) to multi-organ failure (MOF). Progression of COVID-19 is thought to occur as a result of a complex interplay between multiple pathophysiological mechanisms, all of which may orchestrate SARS-CoV-2 infection and contribute to organ-specific tissue damage. In this respect, dissecting currently available knowledge of COVID-19 immunopathogenesis is crucially important, not only to improve our understanding of its pathophysiology but also to fuel the rationale of both novel and repurposed treatment modalities. Various immune-mediated pathways during SARS-CoV-2 infection are relevant in this context, which relate to innate immunity, adaptive immunity, and autoimmunity. Pathological findings in tissue specimens of patients with COVID-19 provide valuable information with regard to our understanding of pathophysiology as well as the development of evidence-based treatment regimens. This review provides an updated overview of the main pathological changes observed in COVID-19 within the most commonly affected organ systems, with special emphasis on immunopathology. Current management strategies for COVID-19 include supportive care and the use of repurposed or symptomatic drugs, such as dexamethasone, remdesivir, and anticoagulants. Ultimately, prevention is key to combat COVID-19, and this requires appropriate measures to attenuate its spread and, above all, the development and implementation of effective vaccines. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Prolonged viral clearance of severe acute respiratory syndrome coronavirus 2 in the older aged population

INTRODUCTION

The detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) is the standard method for the diagnosis of coronavirus disease 2019 (COVID-19). This PCR test can be positive even in patients who have recovered from the disease, and the duration for achieving viral clearance has not been clarified yet.

METHODS

This study was conducted between April 3, 2020, and June 17, 2020, at the Toyama University Hospital and the Toyama Rehabilitation Home. We collected the data of patients with COVID-19, analyzing the duration until twice-consecutive negative qRT-PCR test.

RESULTS

A total of 42 patients were enrolled. The median duration of the twice-consecutive negative qRT-PCR test was 29.0 d (interquartile range: 25.75-35.25). The longest duration of viral shedding was 73 d. The duration of viral clearance was significantly longer in the older (>65 years) group than in the younger group (34.5 d vs. 25.0 d, P < 0.0001).

CONCLUSION

This study demonstrated that viral clearance tends to be sustained in the older adults.

Immunotherapy use outside clinical trial populations: never say never?

BACKGROUND

Based on favourable outcomes in clinical trials, immune checkpoint inhibitors (ICIs), most notably programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) inhibitors, are now widely used across multiple cancer types. However, due to their strict inclusion and exclusion criteria, clinical studies often do not address challenges presented by non-trial populations.

DESIGN

This review summarises available data on the efficacy and safety of ICIs in trial-ineligible patients, including those with autoimmune disease, chronic viral infections, organ transplants, organ dysfunction, poor performance status, and brain metastases, as well as the elderly, children, and those who are pregnant. In addition, we review data concerning other real-world challenges with ICIs, including timing of therapy switch, relationships to radiotherapy or surgery, re-treatment after an immune-related toxicity, vaccinations in patients on ICIs, and current experience around ICI and coronavirus disease-19. Where possible, we provide recommendations to aid the often-difficult decision-making process in those settings.

CONCLUSIONS

Data suggest that ICIs are often active and have an acceptable safety profile in the populations described above, with the exception of PD-1 inhibitors in solid organ transplant recipients. Decisions about whether to treat with ICIs should be personalised and require multidisciplinary input and careful counselling of patients with respect to potential risks and benefits. Clinical judgements need to be carefully weighed, considering factors such as underlying cancer type, feasibility of alternative treatment options, or activity in trial-eligible patients.

Does Covera-19 know 'when to hold 'em or 'when to fold 'em? A translational thought experiment

The function of proteins depends on their structure. The structural integrity of proteins is dynamic and depends on interacting nearby neighboring moieties that influence their properties and induce folding and structural changes. The conformational changes induced by these nearby neighbors in the micro-environmental milieu at that moment are guided by chemical or electrical bonding attractions. There are few literature references that describe the potential for environmental milieu changes to disfavor SARS-CoV-2 attachment to a receptor for survival outside of a host. There are many studies on the effects of pH (acid and base balance) supporting its importance for protein structure and function, but few focus on pH role in extracellular or intracellular protein or actionable requirements of Covera-19. 'Fold 'em or Hold 'em' is seen by the various functions and effects of furin as it seeks an acidic milieu for action or compatible amino acid sequences which is currently aided by its histidine component and the structural changes of proteins as they enter or exit the host. Questions throughout the text are posed to focus on current thoughts as reviewing applicable COVID-19 translational research science in order to understand the complexities of Covid-19. The pH needs of COVID-19 players and its journey through the human host and environment as well as some efficacious readily available repurposed drugs and out-of-the box and easily available treatments are reviewed.

Immunogenicity and efficacy of the COVID-19 candidate vector vaccine MVA-SARS-2-S in preclinical vaccination

The highly attenuated vaccinia virus MVA is licensed as smallpox vaccine; as a vector it is a component of the approved adenovirus-MVA–based prime-boost vaccine against Ebola virus disease. Here, we provide results from testing the COVID-19 candidate vaccine MVA-SARS-2-S, a poxvirus-based vector vaccine that proceeded to clinical evaluation. When administered by intramuscular inoculation, MVA-SARS-2-S expresses and safely delivers the full-length SARS-CoV-2 S protein, inducing balanced SARS-CoV-2–specific cellular and humoral immunity, and protective efficacy in vaccinated mice. Substantial clinical experience has been gained with MVA vectors using homologous and heterologous prime-boost applications, including the immunization of children and immunocompromised individuals. Thus, MVA-SARS-2-S represents an important resource for developing further optimized COVID-19 vaccines.

Severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2) has emerged as the infectious agent causing the pandemic coronavirus disease 2019 (COVID-19) with dramatic consequences for global human health and economics. Previously, we reached clinical evaluation with our vector vaccine based on modified vaccinia virus Ankara (MVA) against the Middle East respiratory syndrome coronavirus (MERS-CoV), which causes an infection in humans similar to SARS and COVID-19. Here, we describe the construction and preclinical characterization of a recombinant MVA expressing full-length SARS-CoV-2 spike (S) protein (MVA-SARS-2-S). Genetic stability and growth characteristics of MVA-SARS-2-S, plus its robust expression of S protein as antigen, make it a suitable candidate vaccine for industrial-scale production. Vaccinated mice produced S-specific CD8⁺ T cells and serum antibodies binding to S protein that neutralized SARS-CoV-2. Prime-boost vaccination with MVA-SARS-2-S protected mice sensitized with a human ACE2-expressing adenovirus from SARS-CoV-2 infection. MVA-SARS-2-S is currently being investigated in a phase I clinical trial as aspirant for developing a safe and efficacious vaccine against COVID-19.

SARS-CoV-2-specific T cell memory is sustained in COVID-19 convalescent patients for 10 months with successful development of stem cell-like memory T cells

Memory T cells contribute to rapid viral clearance during re-infection, but the longevity and differentiation of SARS-CoV-2-specific memory T cells remain unclear. Here we conduct ex vivo assays to evaluate SARS-CoV-2-specific CD4⁺ and CD8⁺ T cell responses in COVID-19 convalescent patients up to 317 days post-symptom onset (DPSO), and find that memory T cell responses are maintained during the study period regardless of the severity of COVID-19. In particular, we observe sustained polyfunctionality and proliferation capacity of SARS-CoV-2-specific T cells. Among SARS-CoV-2-specific CD4⁺ and CD8⁺ T cells detected by activation-induced markers, the proportion of stem cell-like memory T (T_SCM) cells is increased, peaking at approximately 120 DPSO. Development of T_SCM cells is confirmed by SARS-CoV-2-specific MHC-I multimer staining. Considering the self-renewal capacity and multipotency of T_SCM cells, our data suggest that SARS-CoV-2-specific T cells are long-lasting after recovery from COVID-19, thus support the feasibility of effective vaccination programs as a measure for COVID-19 control.

T cells are instrumental to protective immune responses against SARS-CoV-2, the pathogen responsible for the COVID-19 pandemic. Here the authors show that, in convalescent COVID-19 patients, memory T cell responses are detectable up to 317 days post-symptom onset, in which the presence of stem cell-like memory T cells further hints long-lasting immunity.

Phenotypes and Functions of SARS-CoV-2-Reactive T Cells

Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19), which is an ongoing pandemic disease. SARS-CoV-2-specific CD4+ and CD8+ T-cell responses have been detected and characterized not only in COVID-19 patients and convalescents, but also unexposed individuals. Here, we review the phenotypes and functions of SARS-CoV-2-specific T cells in COVID-19 patients and the relationships between SARS-CoV-2-specific T-cell responses and COVID-19 severity. In addition, we describe the phenotypes and functions of SARS-CoV-2-specific memory T cells after recovery from COVID-19 and discuss the presence of SARS-CoV-2-reactive T cells in unexposed individuals and SARS-CoV-2-specific T-cell responses elicited by COVID-19 vaccines. A better understanding of T-cell responses is important for effective control of the current COVID-19 pandemic.

COVID-19 (SARS-CoV-2) lymphocyte responses are associated with inflammatory biomarkers in total joint replacement surgery candidates pre-operatively

Background

Recent studies indicate that, in addition to antibody production, lymphocyte responses to SARS-CoV-2 may play an important role in protective immunity to COVID-19 and a percentage of the general population may exhibit lymphocyte memory due to unknown/asymptomatic exposure to SARS-CoV-2 or cross-reactivity to other more common coronaviruses pre-vaccination. Total joint replacement (TJR) candidates returning to elective surgeries (median age 68 years) may exhibit similar lymphocyte and/or antibody protection to COVID-19 prior to vaccination

Methods

In this retrospective study, we analyzed antibody titters, lymphocyte memory, and inflammatory biomarkers specific for the Spike and Nucleocapsid proteins of the SARS-CoV-2 virus in a cohort of n=73 returning TJR candidates (knees and/or hips) pre-operatively.

Results

Peripheral blood serum of TJR candidate patients exhibited a positivity rate of 18.4% and 4% for IgG antibodies specific for SARS-CoV-2 nucleocapsid and spike proteins, respectively. 13.5% of TJR candidates exhibited positive lymphocyte reactivity (SI > 2) to the SARS-CoV-2 nucleocapsid protein and 38% to the spike protein. SARS-CoV-2 reactive lymphocytes exhibited a higher production of inflammatory biomarkers (i.e., IL-1β, IL-6, TNFα, and IL-1RA) compared to non-reactive lymphocytes.

Conclusions

A percentage of TJR candidates returning for elective surgeries exhibit pre-vaccination positive SARS-CoV-2 antibodies and T cell memory responses with associated pro-inflammatory biomarkers. This is an important parameter for understanding immunity, risk profiles, and may aid pre-operative planning.

Trial registration

Retrospectively registered.

Diverse Humoral Immune Responses in Younger and Older Adult COVID-19 Patients

We sought to discover links between antibody responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and patient clinical variables, cytokine profiles, and antibodies to endemic coronaviruses. Serum samples from 30 patients of younger (26 to 39 years) and older (69 to 83 years) age groups and with varying clinical severities ranging from outpatient to mechanically ventilated were collected and used to probe a novel multi-coronavirus protein microarray. This microarray contained variable-length overlapping fragments of SARS-CoV-2 spike (S), envelope (E), membrane (M), nucleocapsid (N), and open reading frame (ORF) proteins created through in vitro transcription and translation (IVTT). The array also contained SARS-CoV, Middle East respiratory syndrome coronavirus (MERS-CoV), human coronavirus OC43 (HCoV-OC43), and HCoV-NL63 proteins. IgG antibody responses to specific epitopes within the S1 protein region spanning amino acids (aa) 500 to 650 and within the N protein region spanning aa 201 to 300 were found to be significantly higher in older patients and further significantly elevated in those older patients who were ventilated. Additionally, there was a noticeable overlap between antigenic regions and known mutation locations in selected emerging SARS-CoV-2 variants of current clinical consequence (B.1.1.7, B1.351, P.1, CAL20.C, and B.1.526). Moreover, the older age group displayed more consistent correlations of antibody reactivity with systemic cytokine and chemokine responses than the younger adult group. A subset of patients, however, had little or no response to SARS-CoV-2 antigens and disproportionately severe clinical outcomes. Further characterization of these slow-low-responding individuals with cytokine analysis revealed significantly higher interleukin-10 (IL-10), IL-15, and interferon gamma-induced protein 10 (IP-10) levels and lower epidermal growth factor (EGF) and soluble CD40 ligand (sCD40L) levels than those of seroreactive patients in the cohort. IMPORTANCE As numerous viral variants continue to emerge in the coronavirus disease 2019 (COVID-19) pandemic, determining antibody reactivity to SARS-CoV-2 epitopes becomes essential in discerning changes in the immune response to infection over time. This study enabled us to identify specific areas of antigenicity within the SARS-CoV-2 proteome, allowing us to detect correlations of epitopes with clinical metadata and immunological signals to gain holistic insight into SARS-CoV-2 infection. This work also emphasized the risk of mutation accumulation in viral variants and the potential for evasion of the adaptive immune responses in the event of reinfection. We additionally highlighted the correlation of antigenicity between structural proteins of SARS-CoV-2 and endemic HCoVs, raising the possibility of cross-protection between homologous lineages. Finally, we identified a subset of patients with minimal antibody reactivity to SARS-CoV-2 infection, prompting discussion of the potential consequences of this alternative immune response.

Differential Cytokine Responses in Hospitalized COVID-19 Patients Limit Efficacy of Remdesivir

A significant proportion of COVID-19 patients will progress to critical illness requiring invasive mechanical ventilation. This accentuates the need for a therapy that can reduce the severity of COVID-19. Clinical trials have shown the effectiveness of remdesivir in shortening recovery time and decreasing progression to respiratory failure and mechanical ventilation. However, some studies have highlighted its lack of efficacy in patients on high-flow oxygen and mechanical ventilation. This study uncovers some underlying immune response differences between responders and non-responders to remdesivir treatment. Immunological analyses revealed an upregulation of tissue repair factors BDNF, PDGF-BB and PIGF-1, as well as an increase in ratio of Th2-associated cytokine IL-4 to Th1-associated cytokine IFN-γ. Serological profiling of IgG subclasses corroborated this observation, with significantly higher magnitude of increase in Th2-associated IgG2 and IgG4 responses. These findings help to identify the mechanisms of immune regulation accompanying successful remdesivir treatment in severe COVID-19 patients.

SARS-CoV-2 Portrayed against HIV: Contrary Viral Strategies in Similar Disguise

SARS-CoV-2 and HIV are zoonotic viruses that rapidly reached pandemic scale, causing global losses and fear. The COVID-19 and AIDS pandemics ignited massive efforts worldwide to develop antiviral strategies and characterize viral architectures, biological and immunological properties, and clinical outcomes. Although both viruses have a comparable appearance as enveloped viruses with positive-stranded RNA and envelope spikes mediating cellular entry, the entry process, downstream biological and immunological pathways, clinical outcomes, and disease courses are strikingly different. This review provides a systemic comparison of both viruses' structural and functional characteristics, delineating their distinct strategies for efficient spread.

Exploratory analysis to identify the best antigen and the best immune biomarkers to study SARS-CoV-2 infection

BACKGROUND

Recent studies proposed the whole-blood based IFN-γ-release assay to study the antigen-specific SARS-CoV-2 response. Since the early prediction of disease progression could help to assess the optimal treatment strategies, an integrated knowledge of T-cell and antibody response lays the foundation to develop biomarkers monitoring the COVID-19. Whole-blood-platform tests based on the immune response detection to SARS-CoV2 peptides is a new approach to discriminate COVID-19-patients from uninfected-individuals and to evaluate the immunogenicity of vaccine candidates, monitoring the immune response in vaccine trial and supporting the serological diagnostics results. Here, we aimed to identify in the whole-blood-platform the best immunogenic viral antigen and the best immune biomarker to identify COVID-19-patients.

METHODS

Whole-blood was overnight-stimulated with SARS-CoV-2 peptide pools of nucleoprotein-(NP) Membrane-, ORF3a- and Spike-protein. We evaluated: IL-1β, IL-1Ra, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12p70, IL-13, IL- 15, IL-17A, eotaxin, FGF, G-CSF, GM-CSF, IFN-γ, IP-10, MCP-1, MIP-1α, MIP-1β, PDGF, RANTES, TNF-α, VEGF. By a sparse partial least squares discriminant analysis we identified the most important soluble factors discriminating COVID-19- from NO-COVID-19-individuals.

RESULTS

We identified a COVID-19 signature based on six immune factors: IFN-γ, IP-10 and IL-2 induced by Spike; RANTES and IP-10 induced by NP and IL-2 induced by ORF3a. We demonstrated that the test based on IP-10 induced by Spike had the highest AUC (0.85, p  <  0.0001) and that the clinical characteristics of the COVID-19-patients did not affect IP-10 production. Finally, we validated the use of IP-10 as biomarker for SARS-CoV2 infection in two additional COVID-19-patients cohorts.

CONCLUSIONS

We set-up a whole-blood assay identifying the best antigen to induce a T-cell response and the best biomarkers for SARS-CoV-2 infection evaluating patients with acute COVID-19 and recovered patients. We focused on IP-10, already described as a potential biomarker for other infectious disease such as tuberculosis and HCV. An additional application of this test is the evaluation of immune response in SARS-CoV-2 vaccine trials: the IP-10 detection may define the immunogenicity of a Spike-based vaccine, whereas the immune response to the virus may be evaluated detecting other soluble factors induced by other viral-antigens.

Correlates of Neutralization against SARS-CoV-2 Variants of Concern by Early Pandemic Sera

Emerging SARS-CoV-2 variants of concern that overcome natural and vaccine-induced immunity threaten to exacerbate the COVID-19 pandemic. Increasing evidence suggests that neutralizing antibody (NAb) responses are a primary mechanism of protection against infection. However, little is known about the extent and mechanisms by which natural immunity acquired during the early COVID-19 pandemic confers cross-neutralization of emerging variants. In this study, we investigated cross-neutralization of the B.1.1.7 and B.1.351 SARS-CoV-2 variants in a well-characterized cohort of early pandemic convalescent subjects. We observed modestly decreased cross-neutralization of B.1.1.7 but a substantial 4.8-fold reduction in cross-neutralization of B.1.351. Correlates of cross-neutralization included receptor binding domain (RBD) and N-terminal domain (NTD) binding antibodies, homologous NAb titers, and membrane-directed T cell responses. These data shed light on the cross-neutralization of emerging variants by early pandemic convalescent immune responses. IMPORTANCE Widespread immunity to SARS-CoV-2 will be necessary to end the COVID-19 pandemic. NAb responses are a critical component of immunity that can be stimulated by natural infection as well as vaccines. However, SARS-CoV-2 variants are emerging that contain mutations in the spike gene that promote evasion from NAb responses. These variants may therefore delay control of the COVID-19 pandemic. We studied whether NAb responses from early COVID-19 convalescent patients are effective against the two SARS-CoV-2 variants, B.1.1.7 and B.1.351. We observed that the B.1.351 variant demonstrates significantly reduced susceptibility to early pandemic NAb responses. We additionally characterized virological, immunological, and clinical features that correlate with cross-neutralization. These studies increase our understanding of emerging SARS-CoV-2 variants.

Case Report: Sars-CoV-2 Infection in a Vaccinated Individual: Evaluation of the Immunological Profile and Virus Transmission Risk

During the COVID19 pandemic, a range of vaccines displayed high efficacy in preventing disease, severe outcomes of infection, and mortality. However, the immunological correlates of protection, the duration of immune response, the transmission risk over time from vaccinated individuals are currently under active investigation. In this brief report, we describe the case of a vaccinated Healthcare Professional infected with a variant of Sars-CoV-2, who has been extensively investigated in order to draw a complete trajectory of infection. The patient has been monitored for the whole length of infection, assessing the temporal viral load decay, the quantification of viral RNA and subgenomic mRNA, antibodies (anti Sars-CoV-2, IgA, IgG, IgM) and cell-mediated (cytokine, B- and T-cell profiles) responses. Overall, this brief report highlights the efficacy of vaccine in preventing COVID19 disease, accelerating the recovery from infection, reducing the transmission risk, although the use of precautionary measures against Sars-CoV-2 spreading still remain critical.

Cell Death in Coronavirus Infections: Uncovering Its Role during COVID-19

Cell death mechanisms are crucial to maintain an appropriate environment for the functionality of healthy cells. However, during viral infections, dysregulation of these processes can be present and can participate in the pathogenetic mechanisms of the disease. In this review, we describe some features of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and some immunopathogenic mechanisms characterizing the present coronavirus disease (COVID-19). Lymphopenia and monocytopenia are important contributors to COVID-19 immunopathogenesis. The fine mechanisms underlying these phenomena are still unknown, and several hypotheses have been raised, some of which assign a role to cell death as far as the reduction of specific types of immune cells is concerned. Thus, we discuss three major pathways such as apoptosis, necroptosis, and pyroptosis, and suggest that all of them likely occur simultaneously in COVID-19 patients. We describe that SARS-CoV-2 can have both a direct and an indirect role in inducing cell death. Indeed, on the one hand, cell death can be caused by the virus entry into cells, on the other, the excessive concentration of cytokines and chemokines, a process that is known as a COVID-19-related cytokine storm, exerts deleterious effects on circulating immune cells. However, the overall knowledge of these mechanisms is still scarce and further studies are needed to delineate new therapeutic strategies.

Countries with similar COVID-19 vaccination rates yet divergent outcomes: are all vaccines created equal?

The world is currently engaged in a race of vaccination versus infection in an effort to control the COVID-19 pandemic. Some countries have already achieved high vaccination rates, offering a glimpse into the so-called “post-vaccination” world. We describe here a striking comparison between the similar-sized and neighboring countries of Bahrain and Qatar. While both countries have achieved impressive vaccination rates, cases increased to unprecedented levels in one country while decreasing steadily in the other. Although this could be attributed to a number of factors, we argue here that the heavy reliance on alum-adjuvanted inactivated virus vaccines may have contributed to these discrepant outcomes. We then expand the analysis to compare the outcomes of the top 10 vaccinated countries based on their reliance on inactivated virus vaccines. The results remarkably align with the initial findings seen in Bahrain and Qatar. Countries that did not use inactivated virus vaccines achieved steady declines in daily COVID-19 deaths, while other countries did not. This work highlights the urgent need to further study the effectiveness of alum-adjuvanted inactivated virus vaccines for COVID-19 before expanding their use.

Immune Evasion of SARS-CoV-2 Emerging Variants: What Have We Learnt So Far?

Despite the slow evolutionary rate of SARS-CoV-2 relative to other RNA viruses, its massive and rapid transmission during the COVID-19 pandemic has enabled it to acquire significant genetic diversity since it first entered the human population. This led to the emergence of numerous variants, some of them recently being labeled "variants of concern" (VOC), due to their potential impact on transmission, morbidity/mortality, and the evasion of neutralization by antibodies elicited by infection, vaccination, or therapeutic application. The potential to evade neutralization is the result of diversity of the target epitopes generated by the accumulation of mutations in the spike protein. While three globally recognized VOCs (Alpha or B.1.1.7, Beta or B.1.351, and Gamma or P.1) remain sensitive to neutralization albeit at reduced levels by the sera of convalescent individuals and recipients of several anti-COVID19 vaccines, the effect of spike variability is much more evident on the neutralization capacity of monoclonal antibodies. The newly recognized VOC Delta or lineage B.1.617.2, as well as locally accepted VOCs (Epsilon or B.1.427/29-US and B1.1.7 with the E484K-UK) are indicating the necessity of close monitoring of new variants on a global level. The VOCs characteristics, their mutational patterns, and the role mutations play in immune evasion are summarized in this review.

Approach to SARS-CoV-2 Vaccination in Patients With Multiple Sclerosis

For more than a year now, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been causing the coronavirus disease (COVID-19) pandemic with high mortality and detrimental effects on society, economy, and individual lives. Great hopes are being placed on vaccination as one of the most potent escape strategies from the pandemic and multiple vaccines are already in clinical use. However, there is still a lot of insecurity about the safety and efficacy of vaccines in patients with autoimmune diseases like multiple sclerosis (MS), especially under treatment with immunomodulatory or immunosuppressive drugs. We propose strategic approaches to SARS-CoV-2 vaccination management in MS patients and encourage fellow physicians to measure the immune response in their patients. Notably, both humoral and cellular responses should be considered since the immunological equivalent for protection from SARS-CoV-2 after infection or vaccination still remains undefined and will most likely involve antiviral cellular immunity. It is important to gain insights into the vaccine response of immunocompromised patients in order to be able to deduce sensible strategies for vaccination in the future.

Coordinate Induction of Humoral and Spike Specific T-Cell Response in a Cohort of Italian Health Care Workers Receiving BNT162b2 mRNA Vaccine

Vaccination is the main public health measure to reduce SARS-CoV-2 transmission and hospitalization, and a massive worldwide scientific effort resulted in the rapid development of effective vaccines. This work aimed to define the dynamics of humoral and cell-mediated immune response in a cohort of health care workers (HCWs) who received a two-dose BNT162b2-mRNA vaccination. The serological response was evaluated by quantifying the anti-RBD and neutralizing antibodies. The cell-mediated response was performed by a whole blood test quantifying Th1 cytokines (IFN-γ, TNF-α, IL-2), produced in response to spike peptides. The BNT162b2-mRNA vaccine induced both humoral and cell-mediated immune responses against spike peptides in virtually all HCWs without previous SARS-CoV-2 infection, with a moderate inverse relation with age in the anti-RBD response. Spike-specific T cells produced several Th1 cytokines (IFN-γ, TNF-α, and IL-2), which correlated with the specific-serological response. Overall, our study describes the ability of the BNT162b2 mRNA vaccine to elicit a coordinated neutralizing humoral and spike-specific T cell response in HCWs. Assessing the dynamics of these parameters by an easy immune monitoring protocol can allow for the evaluation of the persistence of the vaccine response in order to define the optimal vaccination strategy.