TGF-β SIGNALING PATHWAY SHAPES ADAPTIVE IMMUNITY in EARLY SARS-CoV-2 INFECTION

Background: SARS-CoV-2 induces cytokine response dysregulation and immune dysfunction. What remains unclear is how cytokine signaling shapes immune responses during early SARS-CoV-2 infection when adaptive immunity is developing. Our goal is to identify immune pathways that shape the early development of adaptive immune responses in COVID-19 patients. We performed paired single-cell transcriptomic and epigenomic profiling at two time-points of early SARS-CoV-2 infection to determine immune signatures of acute infection and epigenetic drivers that underpin immune response dynamics. Methods: PBMC samples were collected from four moderate to severe COVID-19 patients at two early time-points (n = 3 for Week 1 and n = 3 for Week 2 after symptom onset, including 2 participants having paired blood sampling at both time points) and from two healthy controls (n = 2). Using paired scRNA-Seq and scATAC-Seq, we captured transcriptomic and epigenomic profiles in the same single cells to identify chromatin accessibility changes as a potential mechanism for the surge and decline of immune responses elicited during acute SARS-CoV-2 infection. Using bioinformatic approaches, we identified heterogeneous immune cell populations, modeled cell differentiation trajectories, determined dysregulated immune pathways through gene set enrichment analysis, and connected chromatin co-accessible landscapes. Results: We captured transcriptomic and epigenomic profiles of 43,726 single cells and identified paired transcriptional and epigenetic landscapes in six major immune cell types: CD4+ T cells, CD8+ T cells, B cells, dendritic cells, monocytes, and NK cells. We found that early SARS-CoV-2 infection induced a surge in IL-2, IL-6, IFN-α, IFN-γ, TNF-α, and NF-κB responses at Week 1 that declined at Week 2 in adaptive immune cells (CD4+ T, CD8+ T, and B cells). In contrast, TGF-β responses surged early at Week 1 and continued to increase at Week 2 in these cells. In B cells and plasmablasts, we found early surges of IGHA1 (encoding IgA heavy chain) and SOX4 (an essential transcription factor for B cell development) expressions that correlated with expression of SMAD-dependent TGF-β signaling pathway. Further, we found a notable increase in chromatin accessibility at the SMAD binding regulatory element 150 kb upstream of SOX4 in B cells of infected patients. Conclusion: Our data suggest a significant increase in TGF-β activity that instructs dynamic B cell-associated protective immunity during early SARS-CoV-2 infection.

Cancer patients display diminished viral RNA clearance and altered T cell responses during SARS-CoV-2 infection

Cancer patients display immunomodulation related to malignancy and anti-cancer therapies, but how these factors impact COVID-19 remains unknown. To investigate immune responses in cancer patients with COVID-19, we undertook a prospective case-control study, enrolling hospitalized solid tumor patients with acute COVID-19, as well as age-, gender-, and comorbidity-matched COVID-19 patients without cancer as controls. Using biospecimens collected during hospitalization, we performed virologic measurements as well as in-depth immunophenotyping of cellular, antibody and cytokine responses. We enrolled 17 cancer patients (cases) admitted to Yale-New Haven Hospital between March 15 and June 30, 2020 with COVID-19, as well as 17 matched non-cancer patients (controls) admitted with COVID-19. No significant differences were observed between cases and controls based on patient characteristics (age, gender, race, co-morbidities, smoking history, days from symptom onset to COVID-19 diagnosis) or outcomes (COVID-19 severity, length of hospital stay, rate of intubation or mortality). The most common primary tumor sites were lung (4/17) and gastrointestinal (4/17);all cases had received cancer-directed therapy within 6 months of COVID-19 diagnosis, with 13/17 receiving treatment less than 1 month prior to hospitalization. Three of 17 cases had received immune checkpoint inhibitor therapies. Despite having similar SARS-CoV-2 viral RNA loads at the time of COVID-19 diagnosis when compared with controls, cancer cases had increased viral RNA abundance during hospitalization, suggesting slower clearance. Antibody responses against SARS-CoV-2 were preserved in cancer cases, with cases displaying similar levels of IgM and IgG antibodies directed against SARS-CoV-2 epitopes compared to controls. Cytokine profiling revealed higher plasma levels of CCL3, IL1A and CXCL12 in cancer cases compared to controls. Using flow cytometric immunophenotyping, we found that innate immune and non-T cell adaptive immune parameters were similar between cases and controls hospitalized with COVID-19. However, among cancer cases on conventional therapies, T cell lymphopenia was more profound, and these cases demonstrated higher levels of CD8+ exhausted (CD8+CD45RA-PD1+TIM3+ ), CD8+GranzymeB+ and CD4+CD38+HLA-DR+ and CD8+CD38+HLA-DR+ activated T cells when compared with controls;interestingly, these differences were not observed in patients who had received immune checkpoint inhibition. Thus, we found reduced viral RNA clearance and specific alterations in T cell and cytokine responses in cancer patients hospitalized with COVID-19 compared with matched controls with COVID-19. This dysregulated T cell response in cancer patients, which may reflect immune modulation due to chronic antigen stimulation as well as cancer therapies, may lead to altered virologic and clinical outcomes in this population.

Detection of Pneumococcal Pneumonia during SARS-CoV-2 Infection

Background. Streptococcus pneumoniae (pneumococcus) is a common colonizer of the upper respiratory tract and can progress to cause invasive and mucosal disease. Additionally, infection with pneumococcus can complicate respiratory viral infections (influenza, respiratory syncytial virus, etc.) by exacerbating the initial disease. Limited data exist describing the potential relationship of SARS-CoV-2 infection with pneumococcus and the role of co-infection in influencing COVID-19 severity. Methods. Inpatients and healthcare workers testing positive for SARS-CoV-2 during March-August 2020 were tested for pneumococcus through culture-enrichment of saliva followed by RT-qPCR (to identify carriage) and for inpatients only, serotype-specific urine antigen detection (UAD) assays (to identify pneumococcal pneumonia). A multinomial multivariate regression model was used to examine the relationship between pneumococcal detection and COVID-19 severity. Results. Among the 126 subjects who tested positive for SARS-CoV-2, the median age was 62 years;54.9% of subjects were male;88.89% were inpatients;23.5% had an ICU stay;and 13.5% died. Pneumococcus was detected in 17 subjects (13.5%) by any method, including 5 subjects (4.0%) by RT-qPCR and 12 subjects (13.6%) by UAD. Little to no bacterial growth was observed on 21/235 culture plates. Detection by UAD was associated with both moderate and severe COVID-19 disease while RT-qPCR detection in saliva was not associated with severity. None of the 12 individuals who were UAD-positive died. Conclusion. Pneumococcal pneumonia (as determined by UAD) continues to occur during the ongoing pandemic and may be associated with more serious COVID-19 outcomes. Detection of pneumococcal carriage may be masked by high levels of antibiotic use. Future studies should better characterize the relationship between pneumococcus and SARS-CoV-2 across all disease severity levels.

Susceptibility of mature human myocardial cell types to sars-cov-2

Background: SARS-CoV-2 is a highly transmissible and virulent respiratory pathogen responsible for the global coronavirus disease 2019 (COVID-19) pandemic. A significant number of patients infected with SARS-CoV-2 show signs of myocardial injury ranging from asymptomatic troponemia to acute congestive heart failure and cardiogenic shock. The precise mechanisms underlying myocardial injury in this cohort are unclear, and it is difficult to distinguish weather new onset cardiac dysfunction is representative of active myocardial infection or a consequence of systemic illness. To address this gap in knowledge we constructed a model to assess replicative potential of SARS-CoV2 in primary cell lines derived from adult and pediatric myocardium including cardiomyocytes, fibroblasts, and endothelial cells and corroborated our in vitro findings with a pathologic analysis of myocardial tissue obtained from patients infected with SARS-CoV-2. Methods: Samples of atrial myocardium obtained from patients undergoing cardiac surgery were enzymatically digested and purified into cardiomyocyte, fibroblast, and endothelial cell populations. Susceptibility to infection with SARS-CoV-2 was then assessed in primary human myocardial cell types and compared against induced cardiomyocytes derived from human pluripotential stem cells. Infectivity was quantitatively assessed using qPCR against genomic and subgenomic viral RNA and normalized to GAPDH. Postmortem heart and lung FFPE tissue from de-identified patients who died from SARS CoV-2 infection were obtained and analyze by immunofluorescence for viral spike and nucleocapsid protein or stained with hematoxylin and eosin for histological evaluation. Results: Primary cardiomyocytes obtained from adult (n=7) and pediatric (n=7) atrial myocardium could not support active replication SARS-CoV-2 virus and there was no evidence of viral replication in pathologic myocardial specimens obtained from COVID infected patients (n=7). Collectively our data indicate that primary cardiac cell types are unable to support the level of viral replication observed in iPSCM (p=0.0007) suggesting that induced pluripotential stem cells may not adequately model the response of mature myocardium to SARS-CoV-2.

High-affinity, neutralizing antibodies to SARS-CoV-2 can be made without T follicular helper cells

[Figure: see text].

Adaptive immune determinants of viral clearance and protection in mouse models of SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused more than 160 million infections and more than 3 million deaths worldwide. Although effective vaccines are currently being deployed, the adaptive immune determinants that promote viral clearance and confer protection remain poorly defined. Using mouse models of SARS-CoV-2, we demonstrate that both humoral and cellular adaptive immunity contribute to viral clearance in the setting of primary infection. Furthermore, we find that either convalescent mice or mice that receive mRNA vaccination are protected from both homologous infection and infection with a variant of concern, B.1.351. In addition, we find that this protection is largely mediated by antibody response and not cellular immunity. These results highlight the in vivo protective capacity of antibodies generated to both vaccine and natural infection.

Divergent and self-reactive immune responses in the CNS of COVID-19 patients

Background: One third of COVID-19 patients develop significant neurological symptoms, yet SARS-CoV-2 is rarely detected in central nervous system (CNS) tissue, suggesting a potential role for parainfectious processes, including neuroimmune responses. Methods: We examined immune parameters in CSF and blood samples from a cohort of hospitalized patients with COVID-19 and significant neurological complications (n=6), compared to SARS-CoV-2 uninfected controls (Fig1A). Immune cells were characterized by single cell RNA and repertoire sequencing. Intrathecal antibodies were assessed for anti-viral and auto-reactivity by ELISA, mouse brain immunostaining, phage display, and IP-MS. Results: Through single cell and parallel cytokine analyses of CSF and paired plasma, we found divergent T cell responses in the CNS compartment, including increased levels of IL-1B and IL-12-associated innate and adaptive immune cell activation (Fig1B). We found evidence of clonal expansion of B cells in the CSF, with B cell receptor sequences that were unique from those observed in peripheral blood B cells (Fig1C), suggesting a divergent intrathecal humoral response to SARS-CoV-2. Indeed, all COVID-19 cases examined had anti-SARS-antibodies. Next, we directly examined whether CSF resident antibodies targeted self-antigens and found a significant burden of CNS autoimmunity, with the CSF from most patients recognizing neural self-antigens. COVID-19 CSF produced immunoreactive staining of specific anatomic regions of the brain including cortical neurons, olfactory bulb, thalamus, and cerebral vasculature. Finally, we produced a panel of monoclonal antibodies from patients' CSF and peripheral blood, and show that these target both anti-viral and anti-neural antigens-including one CSF-derived mAb specific for the spike protein that also recognizes neural tissue (Fig1D). Conclusion: This immune survey reveals evidence of a compartmentalized and self-reactive immune response in the CNS in COVID-19 patients with neurologic symptoms. We identified both innate and adaptive anti-viral immune responses, as well as humoral autoimmunity that appears to be unique to the CNS during SARS-CoV-2 infection. These data suggest a potential role for autoimmunity in contributing to neurological symptoms, and merit further investigation to the potential role of autoantibodies in post-acute COVID-19 neurological symptoms.

Immune responses to SARS-CoV-2

The clinical presentation of COVID-19 involves a broad range of symptoms and disease trajectories. Understanding the nature of the immune response that leads to recovery over severe disease is key to developing effective treatments for COVID-19. In this talk, I will discuss immune responses in COVID-19 patients with moderate and severe disease. I will compare viral load, immune phenotype, and cytokines that are predictive of mortality and discuss signatures of cytokines and growth factors that associate with recovery vs disease exacerbation. I will also discuss sex differences in immunity to SARS-CoV-2 and how such differences correspond to disease outcomes.

Implementing an at-home smell test for early assessment of COVID-19 in high-risk healthcare workers

Background: Smell loss has been recognized as an important, and potentially early, sign of COVID-19. However, to date smell loss has only been assessed in retrospective, COVID+ cohorts, and largely through self-report. The objective of this study was to implement a daily standardized behavioral test of smell sensitivity in healthcare workers (HCW) to capture changes in smell sensitivity over time and to assess whether these changes occur prior to positive COVID test. Methods: The study enrolled 500 high-risk COVID-negative HCW during the COVID-19 epidemic in Connecticut, beginning March 28, 2020 (80% F, mean age 38, 58% nurses). Initially, HCW received a daily symptom questionnaire with parosmia screening questions. On April 23 we introduced the “Jiffy”, a daily at-home psychophysical test of smell sensitivity, where olfactory stimuli are sampled and rated for perceived intensity. SARS-CoV-2 infection was tested every three days by PCR of nasopharyngeal swabs or saliva Results: Of the first 500 enrolled HCW, 376 HCW (75%) completed the Jiffy 4528 times (mean 12 times/HCW). 17/500 HCW (3.4%) had a COVID+ test, of which 9/17 (53%) reported smell loss through the Jiffy or the daily symptom survey. 6/9 (67%) reported smell loss that preceded or was concurrent with a COVID+ test. 8/17 COVID+ HCW completed the Jiffy, with 5/8 (63%) reporting reductions in smell versus 42/368 (11%) COVID- HCW (OR=13, 95% CI: 2.4-85, p=.001). COVID+ HCW rated their greatest reduction in smell sensitivity as slight (40%) and severe (60%), versus slight (88%) and moderate (12%) in COVID- HCW. 16/17 COVID+ HCW completed a daily symptom survey (mean 14 times/HCW), with 8/16 (50%) ever reporting parosmia versus 90/466 (19%) of COVID- HCW (OR=4.2, 95% CI: 1.3-13, p=.007). Overall, parosmia was the first reported symptom in 3/13 (23%) COVID+ HCW who reported symptoms. Conclusion: We conducted a prospective study of smell testing in a population at high risk for COVID-19 using two parallel approaches. Our results demonstrate the feasibility of at-home smell testing for assessing parosmia during COVID-19, in some cases even prior to a positive PCR result. Given the urgent need for widespread, lowcost, non-invasive testing for COVID-19, we are now developing an easy-to-use app to distribute this survey more widely to high-risk populations. (Table Presented).

Active monitoring of a healthcare worker cohort during the COVID-19 epidemic

Background: Initial CDC recommendations for passive monitoring of COVID-19 related symptoms among staff may not be sufficient in preventing the introduction and transmission of SARS-CoV-2 in healthcare settings. We therefore implemented active monitoring for SARS-CoV-2 infection in healthcare workers (HCWs) at an academic medical center during the COVID-19 epidemic in northeast US. Methods: We recruited a cohort of HCWs at Yale New Haven Hospital who worked in COVID-19 units and did not have COVID-19 related symptoms between March 28 and June 1, 2020. During follow-up, participants provided daily information on symptoms by responding to a web-based questionnaire, self-administered nasopharyngeal (NP) and saliva specimens every 3 days, and blood specimens every 14 days. We performed SARS-CoV-2 RT-PCR and an anti-spike protein IgM and IgG ELISA to identify virological and serological-confirmed infection, respectively. Results: We enrolled 525 (13%) amongst 4,136 HCW of whom daily information on symptoms and NP, saliva, and blood specimens were obtained for 66% (of 13208), 42% (or 1977), 44% (of 2071) and 65% (of 1099), respectively, of the follow-up measurement points. We identified 16 (3.0% of 525) HCWs with PCR-confirmed SARS-CoV-2 infection and an additional 12 (2.3% of 525) who were not tested by PCR or had negative PCR results but had serological evidence of infection. The overall cumulative incidence of SARS-CoV-2 infection was 5.3% (28 of 525) amongst HCWs. Cases were not identified by hospital protocols for passive staff self-monitoring for symptoms. Amongst 16 PCR-confirmed cases, 9 (56%) of the 16 PCR-confirmed HCW had symptoms during or after the date of initial detection. We did not identify an epidemiological link between the 28 confirmed cases. Conclusion: We found that a significant proportion (5.3%) of HCWs were infected with SARS-CoV-2 during the COVID-19 epidemic. In the setting of universal PPE use, infections were possibly acquired in the community rather than stemming from patient-HCW or HCW-HCW transmission. Passive monitoring of symptoms is inadequate in preventing introductions of SARS-CoV-2 into the healthcare setting due to asymptomatic and oligosymptomatic presentations.