Epithelial galectin-3 induces mitochondrial complex inhibition and cell cycle arrest of CD8+ T Cells in severe/critical ill COVID-19 (preprint)

Several studies have identified the presence of functionally depleted CD8+ T cells in COVID-19 patients, and particularly abnormally reduced CD8+ T cells in severe/critical patients, which may be a major cause of disease progression and poor prognosis. In this study, a proliferating-depleted CD8+ T cell phenotype was observed in severe/critical COVID-19 patients through scRNA-seq and scTCR-seq analysis. These CD8+ T cells were subsequently found to be characterized by cell cycle arrest and downregulation of mitochondrial biogenesis and respiratory chain complex genes. Cellchat analysis revealed that the Galectin signaling pathways between infected lung epithelial cells and CD8+ T cells play the key role in inducing CD8+ T cell reduction and dysfunction in severe/critical COVID-19. We used SARS-COV-2 ORF3a to transfect A549 epithelial cells, and co-cultured with CD8+ T cells. The ex vivo experiments confirmed that galectin-3 inhibited the transcription of mitochondrial respiratory chain complex III/IV genes in CD8+ T cells by suppressing the nuclear translocation of nuclear respiratory factor 1 (NRF1). In addition, the regulatory effect of galectin-3 was correlated with the activation of ERK signaling and/or the inhibition of Akt signaling. Galectin-3 inhibitor, TD-139, promoted nuclear translocation of NRF1, and enhanced mitochondrial respiratory chain complex III/IV gene expression and mitochondrial biogenesis, then restore the expansion ability of CD8+ T cells. Our study improved the understanding the immunopathogenesis and provided new target for the prevention and treatment of severe/critical COVID-19.

Incubation Period of Coronavirus Disease 2019: New Implications for Intervention and Control (preprint)

Background: The COVID-19 pandemic raging around the world has caused serious disasters to mankind. The incubation period is a key parameter for epidemic control and also an important basis for epidemic prediction, but its distribution law remain unclear. Methods: The incubation period T was described by the accelerated failure time models, and the principle of interval-censored data processing and estimation methods were used. Statistical analysis were performed on R-4.0.2 software using “coarseDataTools 0.6-5” package to optimize the parameters to be estimated and calculate the confidence interval. The optimization method used when solving the maximum likelihood function is the simplex method. We used bootstrap re-sampling procedures with 1000 iterations to estimate the confidence interval. Results: Here we analyzed the epidemiological information of 787 confirmed non-Wuhan resident cases, and systematically studied the characteristics of the incubation period of COVID-19 based on the interval-censored data estimation method. Through the statistical analysis of the overall and 7 types of sub-group samples, it was concluded that the incubation period of COVID-19 approximately conformed to the Gamma distribution with a mean value of 7.8 (95%CI: 7.4-8.5) days and a median value of 7.0 (95%CI: 6.7-7.3) days. Conclusions: The incubation period was positively correlated with age and negatively correlated with disease severity. Female cases presented a slightly higher incubation period than that of males. The incubation period of cases with travel history to Hubei and multiple exposures was shorter. The proportion of infected persons who developed symptoms within 14 days was 91.6%. These results are of great significance to the prevention and control of the COVID-19 pandemic.

Transmission Dynamics of Coronavirus Disease 2019 (COVID-19) in the World: The Roles of Intervention and Seasonality (preprint)

The coronavirus disease 2019 (COVID-19) is spreading rapidly all over the world. The transmission dynamics of the COVID-19 pandemic is still unclear, but developing strategies for mitigating the severity of the pandemic is yet a top priority for global public health. In this study, we developed a novel compartmental model, SEIR-CV(susceptible-exposed-infectious-removed with control variables), which not only considers the key characteristics of asymptomatic infection and the effects of seasonal variations, but also incorporates different control measures for multiple transmission routes, so as to accurately predict and effectively control the spread of COVID-19. Based on SEIR-CV, we predicted the COVID-19 epidemic situation in China out of Hubei province and proposed corresponding control strategies. The results showed that the prediction results are highly consistent with the outbreak surveillance data, which proved that the proposed control strategies have achieved sound consequent in the actual epidemic control. Subsequently, we have conducted a rolling prediction for the United States, Brazil, India, five European countries (the United Kingdom, Italy, Spain, Germany, and France), southern hemisphere, northern hemisphere, and the world out of China. The results indicate that control measures and seasonal variations have a great impact on the progress of the COVID-19 pandemic. Our prediction results show that the COVID-19 pandemic is developing more rapidly due to the impact of the cold season in the southern hemisphere countries such as Brazil. While the development of the pandemic should have gradually weakened in the northern hemisphere countries with the arrival of the warm season, instead of still developing rapidly due to the relative loose control measures such as the United States and India. Furthermore, the prediction results illustrate that if keeping the current control measures in the main COVID-19 epidemic countries, the pandemic will not be contained and the situation may eventually turn to group immunization, which would lead to the extremely severe disaster of about 5 billion infections and 300 million deaths globally. However, if China's super stringent control measures were implemented from 15 July, 15 August or 15 September 2020, the total infections would be contained about 15 million, 32 million or 370 million respectively, which indicates that the stringent and timely control measures is critical, and the best window period is before September for eventually overcoming COVID-19.

Heparin-induced thrombocytopenia is associated with a high risk of mortality in critical COVID-19 patients receiving heparin-involved treatment (preprint)

Background Coronavirus infectious disease 2019 (COVID-19) has developed into a global pandemic. It is essential to investigate the clinical characteristics of COVID-19 and uncover potential risk factors for severe disease to reduce the overall mortality rate of COVID-19. Methods Sixty-one critical COVID-19 patients admitted to the intensive care unit (ICU) and 93 severe non-ICU patients at Huoshenshan Hospital (Wuhan, China) were included in this study. Medical records, including demographic, platelet counts, heparin-involved treatments, heparin-induced thrombocytopenia-(HIT) related laboratory tests, and fatal outcomes of COVID-19 patients were analyzed and compared between survivors and nonsurvivors. Findings Sixty-one critical COVID-19 patients treated in ICU included 15 survivors and 46 nonsurvivors. Forty-one percent of them (25/61) had severe thrombocytopenia, with a platelet count (PLT) less than 50x109/L, of whom 76% (19/25) had a platelet decrease of >50% compared to baseline; 96% of these patients (24/25) had a fatal outcome. Among the 46 nonsurvivors, 52.2% (24/46) had severe thrombocytopenia, compared to 6.7% (1/15) among survivors. Moreover, continuous renal replacement therapy (CRRT) could induce a significant decrease in PLT in 81.3% of critical CRRT patients (13/16), resulting in a fatal outcome. In addition, a high level of anti-heparin-PF4 antibodies, a marker of HIT, was observed in most ICU patients. Surprisingly, HIT occurred not only in patients with heparin exposure, such as CRRT, but also in heparin-naive patients, suggesting that spontaneous HIT may occur in COVID-19. Interpretation Anti-heparin-PF4 antibodies are induced in critical COVID-19 patients, resulting in a progressive platelet decrease. Exposure to a high dose of heparin may trigger further severe thrombocytopenia with a fatal outcome. An alternative anticoagulant other than heparin should be used to treat COVID-19 patients in critical condition.

Systemic analysis of tissue cells potentially vulnerable to SARS-CoV-2 infection by the protein-proofed single-cell RNA profiling of ACE2, TMPRSS2 and Furin proteases (preprint)

Single-cell RNA profiling of ACE2, the SARS-CoV-2 receptor, had proposed multiple tissue cells as the potential targets of SARS-CoV-2, the novel coronavirus causing the COVID-19 pandemic. However, most were not echoed by the patients clinical manifestations, largely due to the lack of protein expression information of ACE2 and co-factors. Here, we incorporated the protein information to analyse the expression of ACE2, together with TMPRSS2 and Furin, two proteases assisting SARS-CoV-2 infection, at single cell level in situ, which we called protein-proofed single-cell RNA (pscRNA) profiling. Systemic analysis across 36 tissues revealed a rank list of candidate cells potentially vulnerable to SARS-CoV-2. The top targets are lung AT2 cells and macrophages, then cardiomyocytes and adrenal gland stromal cells, followed by stromal cells in testis, ovary and thyroid. Whereas, the polarized kidney proximal tubule cells, liver cholangiocytes and intestinal enterocytes are less likely to be the primary SARS-CoV-2 targets as ACE2 localizes at the apical region of cells, where the viruses may not readily reach. Actually, the stomach may constitute a physical barrier against SARS-CoV-2 as the acidic environment in normal stomach (pH < 2.0) could completely inactivate SARS-CoV-2 pseudo-viruses. These findings are in concert with the clinical characteristics of prominent lung symptoms, frequent heart injury, and uncommon intestinal symptoms and acute kidney injury. Together, we provide a comprehensive view on the potential SARS-CoV-2 targets by pscRNA profiling, and propose that, in addition to acute respiratory distress syndrome, attentions should also be paid to the potential injuries in cardiovascular, endocrine and reproductive systems during the treatment of COVID-19 patients.

Highly pathogenic coronavirus N protein aggravates lung injury by MASP-2-mediated complement over-activation (preprint)

An excessive immune response contributes to SARS-CoV, MERS-CoV and SARS-CoV-2 pathogenesis and lethality, but the mechanism remains unclear. In this study, the N proteins of SARS-CoV, MERS-CoV and SARS-CoV-2 were found to bind to MASP-2, the key serine protease in the lectin pathway of complement activation, resulting in aberrant complement activation and aggravated inflammatory lung injury. Either blocking the N protein:MASP-2 interaction or suppressing complement activation can significantly alleviate N protein-induced complement hyper-activation and lung injury in vitro and in vivo. Complement hyper-activation was also observed in COVID-19 patients, and a promising suppressive effect was observed when the deteriorating patients were treated with anti-C5a monoclonal antibody. Complement suppression may represent a common therapeutic approach for pneumonia induced by these highly pathogenic coronaviruses.