Differential dynamics of peripheral immune responses to acute SARS-CoV-2 infection in older adults.

In this study, peripheral blood mononuclear cells from young and old patients with COVID-19 were examined phenotypically, transcriptionally and functionally to reveal age-, time- and severity-specific adaptations. Gene signatures within memory B cells and plasmablasts correlated with reduced frequency of antigen-specific B cells and neutralizing antibodies in older patients with severe COVID-19. Moreover, these patients exhibited exacerbated T cell lymphopenia, which correlated with lower plasma interleukin-2, and diminished antigen-specific T cell responses. Single-cell RNA sequencing revealed augmented signatures of activation, exhaustion, cytotoxicity and type I interferon signaling in memory T and natural killer cells with age. Although cytokine storm was evident in both age groups, older individuals exhibited elevated levels of myeloid cell recruiting factors. Furthermore, we observed redistribution of monocyte and dendritic cell subsets and emergence of a suppressive phenotype with severe disease, which was reversed only in young patients over time. This analysis provides new insights into the impact of aging on COVID-19.

SARS-Cov-2 Infection and Seroconversion Rates in Healthcare Providers Prior to COVID-19 Vaccine Rollout.

OBJECTIVE: A 6-month longitudinal surveillance study of asymptomatic healthcare providers (HCP) was carried out at a large urban academic medical center in the United States to assess whether their job occupation with higher exposure risks to SARS-CoV-2 would equate with higher risk of contracting COVID-19 at the beginning of the pandemic before COVID-19 vaccines were available. METHODS: A longitudinal cohort study design was used to collect and analyze immunological and virological monitoring data and self-report survey assessments of personal protective equipment (PPE) availability, adherence to infection control guidelines, and time spent on COVID-19 wards. RESULTS: Among 289 eligible participants, SARS-CoV-2 exposure risk was high with 48-69% participants working in COVID-19 units and more than 30% of them caring for COVID-19 patients. However, the seroconversion rate was low with only 2.1% of participants developing humoral or cellular immunity against SARS-CoV-2. CONCLUSION: Our study findings suggest that, for this HCP cohort working at a large urban academic medical center, a low incidence of SARS-CoV-2 infection could be maintained under conditions of strict infection prevention protocols and reliable PPE availability.

Rapid Protection from COVID-19 in Nonhuman Primates Vaccinated Intramuscularly but Not Intranasally with a Single Dose of a Vesicular Stomatitis Virus-Based Vaccine.

The ongoing pandemic of coronavirus (CoV) disease 2019 (COVID-19) continues to exert a significant burden on health care systems worldwide. With limited treatments available, vaccination remains an effective strategy to counter transmission of severe acute respiratory syndrome CoV 2 (SARS-CoV-2). Recent discussions concerning vaccination strategies have focused on identifying vaccine platforms, number of doses, route of administration, and time to reach peak immunity against SARS-CoV-2. Here, we generated a single-dose, fast-acting vesicular stomatitis virus (VSV)-based vaccine derived from the licensed Ebola virus (EBOV) vaccine rVSV-ZEBOV, expressing the SARS-CoV-2 spike protein and the EBOV glycoprotein (VSV-SARS2-EBOV). Rhesus macaques vaccinated intramuscularly (i.m.) with a single dose of VSV-SARS2-EBOV were protected within 10 days and did not show signs of COVID-19 pneumonia. In contrast, intranasal (i.n.) vaccination resulted in limited immunogenicity and enhanced COVID-19 pneumonia compared to results for control animals. While both i.m. and i.n. vaccination induced neutralizing antibody titers, only i.m. vaccination resulted in a significant cellular immune response. RNA sequencing data bolstered these results by revealing robust activation of the innate and adaptive immune transcriptional signatures in the lungs of i.m. vaccinated animals only. Overall, the data demonstrate that VSV-SARS2-EBOV is a potent single-dose COVID-19 vaccine candidate that offers rapid protection based on the protective efficacy observed in our study. IMPORTANCE The vesicular stomatitis virus (VSV) vaccine platform rose to fame in 2019, when a VSV-based Ebola virus (EBOV) vaccine was approved by the European Medicines Agency and the U.S. Food and Drug Administration for human use against the deadly disease. Here, we demonstrate the protective efficacy of a VSV-EBOV-based COVID-19 vaccine against challenge in nonhuman primates (NHPs). When a single dose of the VSV-SARS2-EBOV vaccine was administered intramuscularly (i.m.), the NHPs were protected from COVID-19 within 10 days. In contrast, if the vaccine was administered intranasally, there was no benefit from the vaccine and the NHPs developed pneumonia. The i.m. vaccinated NHPs quickly developed antigen-specific IgG, including neutralizing antibodies. Transcriptional analysis highlighted the development of protective innate and adaptive immune responses in the i.m. vaccination group only.

Correlates of SARS-CoV-2 anti-RBD IgG antibody titers among persons experiencing homelessness in Los Angeles.

OBJECTIVES: People experiencing homelessness (PEH) have been especially impacted by the COVID-19 pandemic, likely due to increased vulnerabilities stemming from chronic diseases, substance use, and mental health conditions. DESIGN: A case-control study to assess the presence of antibodies against SARS-CoV-2 among PEH and associations with key variables. SAMPLE: A convenience sample of 97 PEH in Skid Row, Los Angeles. MEASUREMENTS: A structured questionnaire assessing socio-demographic, mental health, drug and alcohol use, health care access, pandemic stress, and other COVID-19-specific questions. RESULTS: We found high anti-receptor binding domain (RBD) IgG titers among five of 15 PEH who reported no prior COVID-19 diagnosis or being vaccinated, suggesting undiagnosed and/or asymptomatic COVID-19. While anti-RBD IgG titers across vaccination categories were not statistically significant (p = .069), participants vaccinated with Janssen had the lowest mean anti-RBD IgG titers. In multivariable analysis, we found negative associations between level of SARS-CoV-2 antibody titers with the Janssen vaccine and depression; thus, a need for integrated care for PEH with depression and COVID-19. CONCLUSIONS: Further research is warranted to confirm the immune response, initial and over time, to SARS-CoV-2 infection and to COVID-19 vaccinations, particularly among PEH whose immune systems may be impacted by multiple health conditions.

Single-cell RNA sequencing reveals immunological rewiring at the maternal-fetal interface following asymptomatic/mild SARS-CoV-2 infection.

While severe coronavirus 2019 (COVID-19) is associated with immune activation at the maternal-fetal interface, responses to asymptomatic/mild severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during pregnancy remain unknown. Here, we assess immunological adaptations in blood and term decidua in response to asymptomatic/mild disease in pregnant women. We report attenuated antigen presentation and type I interferon (IFN) signaling pathways, loss of tissue-resident decidual macrophages, and upregulated cytokine/chemokine signaling in monocyte-derived decidual macrophages. Furthermore, we describe increased frequencies of activated tissue-resident T cells and decreased abundance of regulatory T cells with infection while frequencies of cytotoxic CD4/CD8 T cells are increased in the blood. In contrast to decidual macrophages, type I IFN signaling is higher in decidual T cells. Finally, infection leads to a narrowing of T cell receptor diversity in both blood and decidua. Collectively, these observations indicate that asymptomatic/mild COVID-19 during pregnancy results in remodeling of the immunological landscape of the maternal-fetal interface, with a potential for long-term adverse outcomes for the offspring.

Roles of antiviral sensing and type I interferon signaling in the restriction of SARS-CoV-2 replication.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019. Few studies have compared replication dynamics and host responses to SARS-CoV-2 in cell lines from different tissues and species. Therefore, we investigated the role of tissue type and antiviral genes during SARS-CoV-2 infection in nonhuman primate (kidney) and human (liver, respiratory epithelial, gastric) cell lines. We report different viral growth kinetics and release among the cell lines despite comparable ACE2 expression. Transcriptomics revealed that absence of STAT1 in nonhuman primate cells appeared to enhance inflammatory responses without effecting infectious viral titer. Deletion of RL-6 in respiratory epithelial cells increased viral replication. Impaired infectious virus release was detected in Huh7 but not Huh7.5 cells, suggesting a role for RIG1. Gastric cells MKN45 exhibited robust antiviral gene expression and supported viral replication. Data here provide insight into molecular pathogenesis of and alternative cell lines for studying SARS-CoV-2 infection.

Single-cell profiling of T and B cell repertoires following SARS-CoV-2 mRNA vaccine.

mRNA vaccines for SARS-CoV-2 have shown exceptional clinical efficacy, providing robust protection against severe disease. However, our understanding of transcriptional and repertoire changes following full vaccination remains incomplete. We used scRNA-Seq and functional assays to compare humoral and cellular responses to 2 doses of mRNA vaccine with responses observed in convalescent individuals with asymptomatic disease. Our analyses revealed enrichment of spike-specific B cells, activated CD4+ T cells, and robust antigen-specific polyfunctional CD4+ T cell responses following vaccination. On the other hand, although clonally expanded CD8+ T cells were observed following both vaccination and natural infection, CD8+ T cell responses were relatively weak and variable. In addition, TCR gene usage was variable, reflecting the diversity of repertoires and MHC polymorphism in the human population. Natural infection induced expansion of CD8+ T cell clones that occupy distinct clusters compared to those induced by vaccination and likely recognize a broader set of viral antigens of viral epitopes presented by the virus not seen in the mRNA vaccine. Our study highlights a coordinated adaptive immune response in which early CD4+ T cell responses facilitate the development of the B cell response and substantial expansion of effector CD8+ T cells, together capable of contributing to future recall responses.

Pathogenic and transcriptomic differences of emerging SARS-CoV-2 variants in the Syrian golden hamster model.

BACKGROUND: Following the discovery of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its rapid spread throughout the world, new viral variants of concern (VOC) have emerged. There is a critical need to understand the impact of the emerging variants on host response and disease dynamics to facilitate the development of vaccines and therapeutics. METHODS: Syrian golden hamsters are the leading small animal model that recapitulates key aspects of severe coronavirus disease 2019 (COVID-19). We performed intranasal inoculation of SARS-CoV-2 into hamsters with the ancestral virus (nCoV-WA1-2020) or VOC first identified in the United Kingdom (B.1.1.7, alpha) and South Africa (B.1.351, beta) and analyzed viral loads and host responses. FINDINGS: Similar gross and histopathologic pulmonary lesions were observed after infection with all three variants. Although differences in viral genomic copy numbers were noted in the lungs and oral swabs of challenged animals, infectious titers in the lungs were comparable between the variants. Antibody neutralization capacities varied, dependent on the original challenge virus and cross-variant protective capacity. Transcriptional profiling of lung samples 4 days post-challenge (DPC) indicated significant induction of antiviral pathways in response to all three challenges with a more robust inflammatory signature in response to B.1.1.7 infection. Furthermore, no additional mutations in the spike protein were detected at 4 DPC. INTERPRETATIONS: Although disease severity and viral shedding were not significantly different, the emerging VOC induced distinct humoral responses and transcriptional profiles compared to the ancestral virus. These observations suggest potential differences in acute early responses or alterations in immune modulation by VOC. FUNDING: Intramural Research Program, NIAID, NIH; National Center for Research Resources, NIH; National Center for Advancing Translational Sciences, NIH.

Corticosteroid treatment in COVID-19 modulates host inflammatory responses and transcriptional signatures of immune dysregulation.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease-2019 (COVID-19), a respiratory disease that varies in severity from mild to severe/fatal. Several risk factors for severe disease have been identified, notably age, male sex, and pre-existing conditions such as diabetes, obesity, and hypertension. Several advancements in clinical care have been achieved over the past year, including the use of corticosteroids (e.g., corticosteroids) and other immune-modulatory treatments that have now become standard of care for patients with acute severe COVID-19. While the understanding of the mechanisms that underlie increased disease severity with age has improved over the past few months, it remains incomplete. Furthermore, the molecular impact of corticosteroid treatment on host response to acute SARS-CoV-2 infection has not been investigated. In this study, a cross-sectional and longitudinal analysis of Ab, soluble immune mediators, and transcriptional responses in young (65 ≤ years) and aged (≥ 65 years) diabetic males with obesity hospitalized with acute severe COVID-19 was conducted. Additionally, the transcriptional profiles in samples obtained before and after corticosteroids became standard of care were compared. The analysis indicates that severe COVID-19 is characterized by robust Ab responses, heightened systemic inflammation, increased expression of genes related to inflammatory and pro-apoptotic processes, and reduced expression of those important for adaptive immunity regardless of age. In contrast, COVID-19 patients receiving steroids did not show high levels of systemic immune mediators and lacked transcriptional indicators of heightened inflammatory and apoptotic responses. Overall, these data suggest that inflammation and cell death are key drivers of severe COVID-19 pathogenesis in the absence of corticosteroid therapy.

Obesity Correlates With Pronounced Aberrant Innate Immune Responses in Hospitalized Aged COVID-19 Patients.

Both age and obesity are leading risk factors for severe coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Specifically, although most infections occur in individuals under the age of 55 years, 95% of hospitalizations, admissions to the intensive care unit, and deaths occur in those over the age of 55 years. Moreover, hospitalized COVID-19 patients have a higher prevalence of obesity. It is generally believed that chronic low-grade inflammation and dysregulated innate and adaptive immune responses that are associated with aging and obesity are responsible for this elevated risk of severe disease. However, the impact of advanced age and obesity on the host response to SARS-CoV-2 infection remains poorly defined. In this study, we assessed changes in the concentration of soluble immune mediators, IgG antibody titers, frequency of circulating immune cells, and cytokine responses to mitogen stimulation as a function of BMI and age. We detected significant negative correlations between BMI and myeloid immune cell subsets that were more pronounced in aged patients. Similarly, inflammatory cytokine production by monocytes was also negatively correlated with BMI in aged patients. These data suggest that the BMI-dependent impact on host response to SARS-CoV-2 is more pronounced on innate responses of aged patients.

Acute SARS-CoV-2 infection is associated with an increased abundance of bacterial pathogens, including Pseudomonas aeruginosa in the nose.

Research conducted on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pathogenesis and coronavirus disease 2019 (COVID-19) generally focuses on the systemic host response, especially that generated by severely ill patients, with few studies investigating the impact of acute SARS-CoV-2 at the site of infection. We show that the nasal microbiome of SARS-CoV-2-positive patients (CoV+, n = 68) at the time of diagnosis is unique when compared to CoV- healthcare workers (n = 45) and CoV- outpatients (n = 21). This shift is marked by an increased abundance of bacterial pathogens, including Pseudomonas aeruginosa, which is also positively associated with viral RNA load. Additionally, we observe a robust host transcriptional response in the nasal epithelia of CoV+ patients, indicative of an antiviral innate immune response and neuronal damage. These data suggest that the inflammatory response caused by SARS-CoV-2 infection is associated with an increased abundance of bacterial pathogens in the nasal cavity that could contribute to increased incidence of secondary bacterial infections.

SARS-CoV-2 acquisition and immune pathogenesis among school-aged learners in four diverse schools.

BACKGROUND: Understanding SARS-CoV-2 infection in children is necessary to reopen schools safely. METHODS: We measured SARS-CoV-2 infection in 320 learners [10.5 ± 2.1 (sd); 7-17 y.o.] at four diverse schools with either remote or on-site learning. Schools A and B served low-income Hispanic learners; school C served many special-needs learners, and all provided predominantly remote instruction. School D served middle- and upper-income learners, with predominantly on-site instruction. Testing occurred in the fall (2020), and 6-8 weeks later during the fall-winter surge (notable for a tenfold increase in COVID-19 cases). Immune responses and mitigation fidelity were also measured. RESULTS: We found SARS-CoV-2 infections in 17 learners only during the surge. School A (97% remote learners) had the highest infection (10/70, 14.3%, p < 0.01) and IgG positivity rates (13/66, 19.7%). School D (93% on-site learners) had the lowest infection and IgG positivity rates (1/63, 1.6%). Mitigation compliance [physical distancing (mean 87.4%) and face-covering (91.3%)] was remarkably high at all schools. Documented SARS-CoV-2-infected learners had neutralizing antibodies (94.7%), robust IFN-γ + T cell responses, and reduced monocytes. CONCLUSIONS: Schools can implement successful mitigation strategies across a wide range of student diversity. Despite asymptomatic to mild SARS-CoV-2 infection, children generate robust humoral and cellular immune responses. IMPACT: Successful COVID-19 mitigation was implemented across a diverse range of schools. School-associated SARS-CoV-2 infections reflect regional rates rather than remote or on-site learning. Seropositive school-aged children with asymptomatic to mild SARS-CoV-2 infections generate robust humoral and cellular immunity.

To B or Not to B: Mechanisms of Protection Conferred by rVSV-EBOV-GP and the Roles of Innate and Adaptive Immunity.

Zaire Ebola virus (EBOV) is a member of the Filoviridae family of negative sense, single-stranded RNA viruses. EBOV infection causes Ebola virus disease (EVD), characterized by coagulopathy, lymphopenia, and multi-organ failure, which can culminate in death. In 2019, the FDA approved the first vaccine against EBOV, a recombinant live-attenuated viral vector wherein the G protein of vesicular stomatitis virus is replaced with the glycoprotein (GP) of EBOV (rVSV-EBOV-GP, Ervebo® by Merck). This vaccine demonstrates high efficacy in nonhuman primates by providing prophylactic, rapid, and post-exposure protection. In humans, rVSV-EBOV-GP demonstrated 100% protection in several phase III clinical trials in over 10,000 individuals during the 2013-2016 West Africa epidemic. As of 2020, over 218,000 doses of rVSV-EBOV-GP have been administered to individuals with high risk of EBOV exposure. Despite licensure and robust preclinical studies, the mechanisms of rVSV-EBOV-GP-mediated protection are not fully understood. Such knowledge is crucial for understanding vaccine-mediated correlates of protection from EVD and to aid the further design and development of therapeutics against filoviruses. Here, we summarize the current literature regarding the host response to vaccination and EBOV exposure, and evidence regarding innate and adaptive immune mechanisms involved in rVSV-EBOV-GP-mediated protection, with a focus on the host transcriptional response. Current data strongly suggest a protective synergy between rapid innate and humoral immunity.

Distinct transcriptional responses to fatal Ebola virus infection in cynomolgus and rhesus macaques suggest species-specific immune responses.

Ebola virus (EBOV) is a negative single-stranded RNA virus within the Filoviridae family and the causative agent of Ebola virus disease (EVD). Nonhuman primates (NHPs), including cynomolgus and rhesus macaques, are considered the gold standard animal model to interrogate mechanisms of EBOV pathogenesis. However, despite significant genetic similarity (>90%), NHP species display different clinical presentation following EBOV infection, notably a ∼1-2 days delay in disease progression. Consequently, evaluation of therapeutics is generally conducted in rhesus macaques, whereas cynomolgus macaques are utilized to determine efficacy of preventative treatments, notably vaccines. This observation is in line with reported differences in disease severity and host responses between these two NHP following infection with simian varicella virus, influenza A and SARS-CoV-2. However, the molecular underpinnings of these differential outcomes following viral infections remain poorly defined. In this study, we compared published transcriptional profiles obtained from cynomolgus and rhesus macaques infected with the EBOV-Makona Guinea C07 using bivariate and regression analyses to elucidate differences in host responses. We report the presence of a shared core of differentially expressed genes (DEGs) reflecting EVD pathology, including aberrant inflammation, lymphopenia, and coagulopathy. However, the magnitudes of change differed between the two macaque species. These findings suggest that the differential clinical presentation of EVD in these two species is mediated by altered transcriptional responses.