- Persistence of viral RNA, pneumocyte syncytia, and thrombosis are hallmarks of advanced COVID-19 pathology
Authors report the systematic analysis of 41 consecutive post-mortem samples from individuals who died of COVID-19. Histological analysis is complemented by immunohistochemistry for cellular and viral antigens and the detection of viral genomes by in situ RNA hybridization. COVID-19 is characterized by extensive alveolar damage (41/41 of patients) and thrombosis of the lung micro- and macro-vasculature (29/41, 71%). Thrombi were in different stages of organization, consistent with their local origin. Pneumocytes and endothelial cells contained viral RNA even at the later stages of the disease. An additional feature was the common presence of a large number of dysmorphic pneumocytes, often forming syncytial elements (36/41, 87%). Despite occasional detection of virus-positive cells, no overt signs of viral infection were detected in other organs, which showed non-specific alterations. Authors conclude that COVID-19 is a unique disease characterized by extensive lung thrombosis, long-term persistence of viral RNA in pneumocytes and endothelial cells, along with the presence of infected cell syncytia. Several of COVID-19 features might be consequent to the persistence of virus-infected cells for the duration of the disease.
- SARS-CoV-2 direct cardiac damage through spike-mediated cardiomyocyte 3 fusion
Viruses spread between hosts through particles, but within hosts, viral genomes can spread from cell to cell through fusion, evading antiviral defenses and obviating costly infectious virion production1-3. Billions of electromechanically coupled cardiomyocytes (CMs) make myocardium inherently vulnerable to pathological electromechanical short circuits caused by intercellular viral spread 4-6. Beyond respiratory illness, COVID-19 affects the heart and cardiac injury and arrhythmias are serious public health concerns8-12. By studying the myocardium of a young woman who died suddenly, diagnosed postmortem with COVID-19, authors discovered highly focal myocardial SARS-CoV-2 infection spreading from one CM to another through intercellular junctions identified by highly concentrated sarcolemmal t-tubule viral spike glycoprotein. SARS-CoV-2 permissively infected beating human induced pluripotent stem cell (hiPSC)-CMs building multinucleated cardiomyotubes (CMTs) through cell-type-specific fusion driven by proteolytically-activated spike glycoprotein. Recombinant spike glycoprotein, co-localizing to sarcolemma and sarcoplasmic reticulum, produced multinucleated CMTs with pathological structure, electrophysiology, and Ca2+ excitation-contraction coupling. Blocking cleavage, a peptide-based protease inhibitor neutralized SARS-CoV-2 spike glycoprotein pathogenicity. Authors conclude that SARS-CoV-2 spike glycoprotein, efficiently primed, activated, and strategically poised during biosynthesis, can exploit the CM’s inherent membranous connectivities to drive heart damage directly, uncoupling clinically common myocardial injury from lymphocytic myocarditis, often suspected but rarely confirmed in COVID-19.
- Case Study: Prolonged infectious SARS-CoV-2 shedding from an asymptomatic immunocompromised cancer patient.
Long-term SARS-CoV-2 shedding was observed from the upper respiratory tract of a female immunocompromised patient with chronic lymphocytic leukemia and acquired hypogammaglobulinemia. Shedding of infectious SARS-CoV-2 was observed up to 70 days, and genomic and subgenomic RNA up to 105 days past initial diagnosis. The infection was not cleared after the first treatment with convalescent plasma, suggesting a limited impact on SARS-CoV-2 in the upper respiratory tract within this patient. Several weeks after a second convalescent plasma transfusion, SARS-CoV-2 RNA was no longer detected. Marked within-host genomic evolution of SARS-CoV-2 was observed, with a continuous turnover of dominant viral variants. However, replication kinetics in Vero E6 cells and primary human alveolar epithelial tissues were not affected. The data indicate that certain immunocompromised patients may shed infectious virus for longer durations than previously recognized. Detection of subgenomic RNA is recommended in persistently SARS-CoV-2 positive individuals as a proxy for the shedding of infectious virus.
- For now, it’s unethical to use human challenge studies for SARS-CoV-2 vaccine development
The prospect of a widely available severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine is an increasingly high priority for an effective response to the coronavirus disease 2019 (COVID-19) pandemic and an area of intense interest and attention for professionals, politicians, and the public alike. The understandable desire for such a vaccine has led to significant discussion and even some planning for the possibility of human challenge studies (HCS) as a tool for accelerating the process for identifying, testing, and developing an effective vaccine. Proponents argue that such HCS are ethically acceptable in the current pandemic. Most critically, they contend that these studies are likely to speed the development of effective vaccines. But based on assessment of these arguments, the authors of this opinion piece disagree. They believe it is unethical to move forward with such trials at the current time. Whereas proponents of these studies suggest that such studies will accelerate the time to approved vaccines, the facts fail to support these claims. HCS to address SARS-CoV-2 face unacceptable ethics challenges, and, further, undertaking them would do a disservice to the public by undermining already strained confidence in the vaccine development process.
- Rapid deployment of SARS-CoV-2 testing: The CLIAHUB
To address the dearth of testing availability in the San Francisco Bay Area, the Chan Zuckerberg Biohub, in partnership with the University of California, San Francisco (UCSF) Clinical Microbiology Lab, rapidly built and deployed an emergency COVID-19 viral testing facility, staffed by a combination of Biohub employees and UCSF graduate students, postdocs, and faculty. These efforts were facilitated by guidance from the Food and Drug Administration (FDA) on February 29, 2020, “Policy for Coronavirus Disease-2019 Tests During the Public Health Emergency”, and an Executive Order (March 12, 2020) from California State Governor Gavin Newsom modifying certain California-specific regulatory personnel requirements. The goal of this facility, called the “CLIAHUB,” was to provide free, rapid, high-capacity testing services to local hospitals, Department of Public Health offices, and community-based clinical screening efforts in the San Francisco Bay Area, with a particular emphasis on underserved populations. In this perspective piece, authors describe in detail the experiences of the Biohub, including organizational structure, recruitment and training of highly skilled volunteers, automation, information management, engineering, protocol development, and clinical validation. The lessons learned are shared to offer guidance to other research laboratories pursuing rapid expansion of diagnostic capabilities in the context of emergency response for COVID-19 and future pandemic responses.
- SARS-CoV-2 Infects Human Engineered Heart Tissues and Models COVID-19 Myocarditis
Epidemiological studies of the COVID-19 pandemic have revealed evidence of cardiac involvement and documented that myocardial injury and myocarditis are predictors of poor outcomes. Nonetheless, little is understood regarding SARS-CoV-2 tropism within the heart and whether cardiac complications result directly from myocardial infection. Authors develop a human engineered heart tissue model and demonstrate that SARS-CoV-2 selectively infects cardiomyocytes. Viral infection is dependent on expression of angiotensin-I converting enzyme 2 (ACE2) and endosomal cysteine proteases, suggesting an endosomal mechanism of cell entry. After infection with SARS-CoV-2, engineered tissues display typical features of myocarditis, including cardiomyocyte cell death, impaired cardiac contractility, and innate immune cell activation. Consistent with these findings, autopsy tissue obtained from individuals with COVID-19 myocarditis demonstrated cardiomyocyte infection, cell death, and macrophage-predominate immune cell infiltrate. These findings establish human cardiomyocyte tropism for SARS-CoV-2 and provide an experimental platform for interrogating and mitigating cardiac complications of COVID-19.