Oral Epithelial Cells Expressing Low or Undetectable Levels of Human Angiotensin-Converting Enzyme 2 are Susceptible SARS-CoV-2Virus Infection in vitro (preprint)

The oral cavity is thought to be one of the portals for SARS-CoV-2 entry. Because there is limited evidence of active oral infection by SARS-CoV-2 viruses, we assessed the capacity of SARS-CoV-2 to infect and replicate in oral epithelial cells. Oral gingival epithelial cells (hTERT TIGKs), salivary gland epithelial cells (A-253), and oral buccal epithelial cells (TR146), which occupy different regions of the oral cavity, were challenged with replication competent SARS-CoV-2 viruses and with pseudo-typed viruses expressing SARS-CoV-2 spike proteins. All oral epithelial cells expressing undetectable or low levels of human angiotensin-converting enzyme 2 (hACE2) but high levels of the alternative receptor CD147 were susceptible to SARS-CoV-2 infection. Viral dynamics in hTERT TIGKs were different from those in A-253 and TR146 cells. For example, levels of viral transcripts were sustained in hTERT TIGKs but were significantly decreased in A-253 and TR146 cells at day 3 after infection. Analysis of oral epithelial cells infected by replication competent SARS-CoV-2 viruses expressing GFP showed that the signals of GFP and SARS-CoV-2 mRNAs were not evenly distributed. Taken together, our results demonstrated oral epithelial cells were susceptible to SARS-CoV-2 viruses despite of low or undetectable levels of hACE2, suggesting that alternative receptors contribute to SARS-CoV-2 infection and may be considered for development of future vaccines and therapeutics.

Utility of cardiovascular magnetic resonance imaging in COVID-19 recovered patients: a short-term follow-up study (preprint)

Objective: To evaluate for cardiac involvement in recovered COVID-19 patients using cardiac magnetic resonance imaging (MRI). Methods: : A total of 30 subjects recently recovered from COVID-19 and abnormal left ventricular global longitudinal strain were enrolled. Routine investigations, inflammatory markers and cardiac MRI were done at baseline with follow-up scan at 6 months in individuals with abnormal baseline scan. Additionally, 20 age-and sex-matched individuals were enrolled as healthy controls (HCs). Results: : All 30 enrolled subjects were symptomatic during active COVID-19 disease and were categorized as mild: 11 (36.7%), moderate: 6 (20%) and severe: 13 (43.3%). Of the 30 patients, 16 (53.3%) had abnormal CMR findings. Myocardial edema was reported in 12 (40%) patients while 10 (33.3%) had LGE. No difference was observed in terms of conventional LV parameters however, COVID-19 recovered patients had significantly lower right ventricular (RV) ejection fraction, RV stroke volume and RV cardiac index compared to HCs. Follow-up scan was abnormal in 4/16 (25%) with LGE persisting in 3 patients. Myocardial T1 (1284 + 43.8 ms vs 1147.6 + 68.4 ms; P<0.0001) and T2 values (50.8+16.7 ms vs 42.6+3.6 ms; P=0.04) were significantly higher in post COVID-19 subjects compared to HCs. Similarly, T1 and T2 values of severe COVID-19 patients were significantly higher compared to mild and moderate cases. Conclusions: : An abnormal CMR was seen in half of recovered patients with persistent abnormality in one-fourth at six months. Our study suggests a need for closer follow-up among recovered subjects in order to evaluate for long term cardiovascular sequalae.

CD169-mediated restrictive SARS-CoV-2 infection of macrophages induces pro-inflammatory responses (preprint)

Exacerbated and persistent innate immune response marked by pro-inflammatory cytokine expression is thought to be a major driver of chronic COVID-19 pathology. Although macrophages are not the primary target cells of SARS-CoV-2 infection in humans, viral RNA and antigens in activated monocytes and macrophages have been detected in post-mortem samples, and dysfunctional monocytes and macrophages have been hypothesized to contribute to a protracted hyper-inflammatory state in COVID-19 patients. In this study, we demonstrate that CD169, a myeloid cell specific I-type lectin, facilitated ACE2-independent SARS-CoV-2 fusion and entry in macrophages. CD169-mediated SARS-CoV-2 entry in macrophages resulted in expression of viral genomic and sub-genomic (sg) RNAs with minimal viral protein expression and no infectious viral particle release, suggesting a post-entry restriction of the SARS-CoV-2 replication cycle. Intriguingly this post-entry replication block was alleviated by exogenous ACE2 expression in macrophages. Restricted expression of viral gRNA and sgRNA in CD169 + macrophages elicited a pro-inflammatory cytokine expression (TNF , IL-6 and IL-1 {beta}) in a RIG-I, MDA-5 and MAVS-dependent manner, which was suppressed by remdesivir pre-treatment. These findings suggest that de novo expression of SARS-CoV-2 RNA in macrophages contributes to the pro-inflammatory cytokine signature and that blocking CD169-mediated ACE2 independent infection and subsequent activation of macrophages by viral RNA might alleviate COVID-19-associated hyperinflammatory response.

Development of a Novel Human CD147 Knock-in NSG Mouse Model to Test SARS-CoV-2 Viral Infection (preprint)

Background: An animal model that can mimic the SARS-CoV-2 infection in humans is critical to understanding the rapidly evolving SARS-CoV-2 virus and for development of prophylactic and therapeutic strategies to combat emerging mutants. Studies show that the spike proteins of SARS-CoV and SARS-CoV-2 bind to human angiotensin-converting enzyme 2 (hACE2, a well-recognized, functional receptor for SARS-CoV and SARS-CoV-2) to mediate viral entry. Several hACE2 transgenic (hACE2Tg) mouse models are being widely used, which are clearly invaluable. However, the hACE2Tg mouse model cannot fully explain: 1) low expression of ACE2 observed in human lung and heart, but lung or heart failure occurs frequently in severe COVID-19 patients; 2) low expression of ACE2 on immune cells, but lymphocytopenia occurs frequently in COVID-19 patients; and 3) hACE2Tg mice do not mimic the natural course of SARS-CoV-2 infection in humans. Moreover, one of most outstanding features of coronavirus infection is the diversity of receptor usage, which includes the newly proposed human CD147 (hCD147) as a possible co-receptor for SARS-CoV-2 entry. It is still debatable whether CD147 can serve as a functional receptor for SARS-CoV-2 infection or entry.Results: Here we successfully generated a hCD147 knock-in mouse model (hCD147KI) in the NOD-scid IL2Rgammanull (NSG) background. In this hCD147KI-NSG mouse model, the hCD147 genetic sequence was placed downstream of the endogenous mouse promoter for mouse CD147 (mCD147), which creates an in vivo model that may better recapitulate physiological expression of hCD147 proteins at the molecular level compared to the existing and well-studied K18-hACE2-B6 (JAX) model. In addition, the hCD147KI-NSG mouse model allows further study of SARS-CoV-2 in the immunodeficiency condition which may assist our understanding of this virus in the context of high-risk populations in immunosuppressed states. Our data show 1) the human CD147 protein is expressed in various organs (including bronchiolar epithelial cells) in hCD147KI-NSG mice by immunohistochemical staining and flow cytometry; 2) hCD147KI-NSG mice are marginally sensitive to SARS-CoV-2 infection compared to WT-NSG littermates characterized by increased viral copies by qRT-PCR and moderate body weight decline compared to baseline; 3) a significant increase in leukocytes in the lungs of hCD147KI-NSG mice, compared to infected WT-NSG mice.Conclusions: hCD147KI-NSG mice are more sensitive to COVID-19 infection compared to WT-NSG mice. The hCD147KI-NSG mouse model can serve as an additional animal model for further interrogation whether CD147 serve as an independent functional receptor or accessory receptor for SARS-CoV-2 entry and immune responses.

Biologic correlates of beneficial convalescent plasma therapy in a COVID-19 patient reveal disease resolution mechanisms (preprint)

Background. While the biomarkers of COVID-19 severity have been thoroughly investigated, the key biological dynamics associated with COVID-19 resolution are still insufficiently understood. Main body. We report a case of full resolution of severe COVID-19 due to convalescent plasma transfusion in a patient with underlying multiple autoimmune syndrome. Following transfusion, the patient showed fever remission, improved respiratory status, and rapidly decreased viral burden in respiratory fluids and SARS-CoV-2 RNAemia. Longitudinal unbiased proteomic analysis of plasma and single-cell transcriptomics of peripheral blood cells conducted prior to and at multiple times after convalescent plasma transfusion identified the key biological processes associated with the transition from severe disease to disease-free state. These included (i) temporally ordered upward and downward changes in plasma proteins reestablishing homeostasis and (ii) post-transfusion disappearance of a particular subset of dysfunctional monocytes characterized by hyperactivated Interferon responses and decreased TNF- signaling. Conclusions. Monitoring specific subsets of innate immune cells in peripheral blood may provide prognostic keys in severe COVID-19. Moreover, understanding disease resolution at the molecular and cellular level should contribute to identify targets of therapeutic interventions against severe COVID-19.

A Multiplex PCR Assay for Identifying All Major SARS-CoV-2 Variants (preprint)

Background Variants of Concern (VOC) of SARS-CoV-2, including the Alpha, Beta, Gamma, and Delta, threaten to prolong the pandemic leading to more global morbidity and mortality. Genome sequencing is the mainstay of tracking the development and evolution of the virus, but is costly, slow, and not easily accessible. Methods A multiplex qRT-PCR assay for SARS-CoV-2 was developed, which identifies all VOC as well as other mutations of interest in the viral genome, eight mutations total, using single nucleotide discriminating molecular beacons in a two-tube assay. The sensitivity and specificity of the assay was tested using in vitro-transcribed targets. Twenty-six SARS-CoV-2 positive patient samples were blinded, then tested using this assay and compared with deep sequencing results. Findings The presented variant molecular beacon assay showed high accuracy when testing in vitro-transcribed targets, down to a limit of detection of five copies of the viral RNA, with 100% specificity. When testing patient samples, the assay was in full agreement with results from deep sequencing with a sensitivity and specificity of 100% (26/26). Using this accurate genotyping, the SARS-CoV-2 samples were classified as the appropriate variants, and of the twenty-six samples two were identified as VOC Alpha, eight as VOC Delta, and two as Epsilon. Interpretation We have developed a qRT-PCR assay for the identification of currently circulating VOC of SARS-CoV-2 as well as other important mutations in its Spike protein coding sequence. This assay can be easily implemented on broadly available five-color thermal cyclers and will help track the spread of these variants.

Subclinical left ventricular dysfunction in COVID-19 recovered patients using speckle tracking echocardiography (preprint)

Objectives: Myocardial injury during active coronavirus disease-2019 (COVID-19) infection is well described however, its persistence during recovery is unclear. We assessed left ventricle (LV) global longitudinal strain (GLS) using speckle tracking echocardiography (STE) in COVID-19 recovered patients and studied its correlation with various parameters. Methods: A total of 134 subjects within 30-45 days post recovery from COVID-19 infection and normal LV ejection fraction were enrolled. Routine blood investigations, inflammatory markers (on admission) and comprehensive echocardiography including STE were done for all. Results: Of the 134 subjects, 121 (90.3%) were symptomatic during COVID-19 illness and were categorized as mild: 61 (45.5%), moderate: 50 (37.3%) and severe: 10 (7.5%) COVID-19 illness. Asymptomatic COVID-19 infection was reported in 13 (9.7%) patients. Subclinical LV and right ventricle (RV) dysfunction were seen in 40 (29.9%) and 14 (10.5%) patients respectively. Impaired LVGLS was reported in 1 (7.7%), 8 (13.1%), 22 (44%) and 9 (90%) subjects with asymptomatic, mild, moderate and severe disease respectively. LVGLS was significantly lower in patients recovered from severe illness (mild: -21 ± 3.4%; moderate: -18.1 ± 6.9%; severe: -15.5 ± 3.1%; P < 0.0001). Subjects with reduced LVGLS had significantly higher interleukin-6 (P < 0.0001), C-reactive protein (P = 0.001), lactate dehydrogenase (P = 0.009) and serum ferritin (P = 0.03) levels during index admission. Conclusions: Subclinical LV dysfunction was seen in nearly a third of recovered COVID-19 patients while 10.5% had RV dysfunction. Our study suggests a need for closer follow-up among COVID-19 recovered subjects to elucidate long-term cardiovascular outcomes.

Changing Pattern of Admissions for Acute Myocardial Infarction in India During the COVID-19 Pandemic (preprint)

Background: Admissions for acute myocardial infarction (MI) have declined significantly during the COVID-19 pandemic. The changes in the presentation, management, and outcomes of MI during the pandemic period are not well recognized, and data from low- and middle-income countries are limited.Methods: In this two-timepoint cross-sectional study involving 187 hospitals across India, patients admitted with MI between 15th March to 15th June in 2020 were compared with those admitted during the corresponding period of 2019. We sought to determine the changes in the number of admissions, management practices, and outcomes.Findings: We included 41,832 consecutive adults with MI. Admissions during the pandemic period (n = 16414) decreased by 35·4% as compared to the corresponding period in 2019 (n = 25418). We observed significant heterogeneity in this decline across India with the North zone reporting greater decline (-44·8%) than the South zone (-27·7%). The weekly average decrease in MI admissions in 2020 which peaked around the mid- study period, correlated negatively with the number of COVID cases (r = -0·48; r 2 = 0·2), but strongly correlated with the stringency of lockdown index (r = 0·95; r 2 = 0·90). On a multi-level logistic regression, admissions were lower in 2020 with older age categories, tier 1 cities, and centers with high patient volume, and teaching programs. Adjusted utilization rate of coronary angiography, and percutaneous coronary intervention decreased by 11·3%, and 5·9% respectively. However, the in-hospital mortality rates did not differ.Interpretation: The magnitude of reduction in MI admissions across India was not uniform. The nature, time course, and the patient demographics were different compared to reports from other countries, suggesting a significant impact due to the lockdown. These findings have important implications in managing MI admissions during the pandemic.Funding Statement: The study is funded by cardiological society of India.Declaration of Interests: Nothing to declare for all the authors.Ethics Approval Statement: Individual participating centres either obtained an ethical approval from respective Institutional ethics committees or a no objection certificate from the administration.