Heparan sulfate promotes ACE2 super-cluster assembly to enhance SARS-CoV-2-associated syncytium formation (preprint)

The mechanism of syncytium formation, caused by spike-induced cell-cell fusion in severe COVID-19, is largely unclear. Here we combine chemical genetics with 4D confocal imaging to establish the cell surface heparan sulfate (HS) as a critical host factor exploited by SARS-CoV-2 to enhance spike’s fusogenic activity. HS binds spike to facilitate ACE2 clustering, generating synapse-like cell-cell contacts to promote fusion pore formation. ACE2 clustering, and thus, syncytium formation is significantly mitigated by chemical or genetic elimination of cell surface HS, while in a cell-free system consisting of purified HS, spike, and lipid-anchored ACE2, HS directly induces ACE2 clustering. Importantly, the interaction of HS with spike allosterically enables a conserved ACE2 linker in receptor clustering, which concentrates spike at the fusion site to overcome fusion-associated activity loss. This fusion-boosting mechanism can be effectively targeted by an investigational HS-binding drug, which reduces syncytium formation in vitro and viral infection in mice.

A live attenuated influenza virus-vectored intranasal COVID-19 vaccine provides rapid, prolonged, and broad protection against SARS-CoV-2 infection (preprint)

Remarkable progress has been made in developing intramuscular vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); however, they are limited with respect to eliciting local immunity in the respiratory tract, which is the primary infection site for SARS-CoV-2. To overcome the limitations of intramuscular vaccines, we constructed a nasal vaccine candidate based on an influenza vector by inserting a gene encoding the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2, named CA4-dNS1-nCoV-RBD (dNS1-RBD). A preclinical study showed that in hamsters challenged 1 day and 7 days after single-dose vaccination or 6 months after booster vaccination, dNS1-RBD largely mitigated lung pathology, with no loss of body weight, caused by either the prototype-like strain or beta variant of SARS-CoV-2. Lasted data showed that the animals could be well protected against beta variant challenge 9 months after vaccination. Notably, the weight loss and lung pathological changes of hamsters could still be significantly reduced when the hamster was vaccinated 24 h after challenge. Moreover, such cellular immunity is relatively unimpaired for the most concerning SARS-CoV-2 variants. The protective immune mechanism of dNS1-RBD could be attributed to the innate immune response in the nasal epithelium, local RBD-specific T cell response in the lung, and RBD-specific IgA and IgG response. Thus, this study demonstrates that the intranasally delivered dNS1-RBD vaccine candidate may offer an important addition to fight against the ongoing COVID-19 pandemic, compensating limitations of current intramuscular vaccines, particularly at the start of an outbreak.

Switching to electric vehicles can lead to significant reductions of PM2.5 and NO2 across China

Summary Transportation contributes to around one-fifth of global greenhouse gas emissions, while also causing severe air pollution. The conversion to electric vehicles (EVs) represents a major path to decarbonize the transport sector, with potentially significant co-benefits for human health. However, the scale of such co-benefits largely remains an empirical question and lacks observational evidence. The full lockdown in China during the coronavirus disease 2019 (COVID-19) pandemic provides an unprecedented real-world experiment to evaluate emission reduction potentials of a large-scale transition to EVs. Here, we utilize ground and satellite observations of air quality during the full lockdown to constrain predictions of a comprehensive chemical transport model and find that the substantial traffic reductions are near-linearly linked to reductions of PM2.5 (particles with an aerodynamic diameter ≤2.5 μm) and NO2. A further extrapolation of a full conversion to EVs shows a significant reduction of PM2.5 (30%–70%) and NO2 (30%–80%) in most of China. Our findings provide fact-based evidence of potential environmental benefits generated by fully switching to EVs.

Sterilizing immunity against SARS-CoV-2 in hamsters conferred by a novel recombinant subunit vaccine (preprint)

A safe and effective SARS-CoV-2 vaccine is essential to avert the on-going COVID-19 pandemic. Here, we developed a subunit vaccine, which is comprised of CHO-expressed spike ectodomain protein (StriFK) and nitrogen bisphosphonates-modified zinc-aluminum hybrid adjuvant (FH002C). This vaccine candidate rapidly elicited the robust humoral response, Th1/Th2 balanced helper CD4 T cell and CD8 T cell immune response in animal models. In mice, hamsters, and non-human primates, 2-shot and 3-shot immunization of StriFK-FH002C generated 28- to 38-fold and 47- to 269-fold higher neutralizing antibody titers than the human COVID-19 convalescent plasmas, respectively. More importantly, the StriFK-FH002C immunization conferred sterilizing immunity to prevent SARS-CoV-2 infection and transmission, which also protected animals from virus-induced weight loss, COVID-19-like symptoms, and pneumonia in hamsters. Vaccine-induced neutralizing and cell-based receptor-blocking antibody titers correlated well with protective efficacy in hamsters, suggesting vaccine-elicited protection is immune-associated. The StriFK-FH002C provided a promising SARS-CoV-2 vaccine candidate for further clinical evaluation.

A comprehensive transcriptome analysis reveals broader but weaker host response of SARS-CoV-2 than SARS-CoV (preprint)

COVID-19, which has resulted a worldwide health crisis with more than 74.9 million confirmed cases worldwide by December 2020, is caused by a newly emerging coronavirus identified and named SARS-CoV-2 in February in Wuhan, China. Experiences in defeating SARS, which infested during 2002-2003, can be used in treating the new disease. However, comparative genomics and epidemiology studies have shown much difference between SARS-CoV and SARS-CoV-2, which underlies the different clinical features and therapies in between those two diseases. Further studies comparing transcriptomes infected by these two viruses to uncover the differences in host responses would be necessary. Here we conducted a comprehensive transcriptome analysis of SARS-CoV and SARS-CoV-2-infected human cell lines, including Caco-2, Calu-3, H1299. Clustering analysis and expression of ACE2 show that SARS-CoV-2 has broader but weaker infection, where the largest discrepancy occurs in the epithelial lung cancer cell, Calu-3. SARS-CoV-2 genes also show less tissue specificity than SARS-CoV genes. Furthermore, we detected more general but moderate immune responses in SARS-CoV-2 infected transcriptomes by comparing weighted gene co-expression networks and modules. Our results suggest a different immune therapy and treatment scheme for COVID-19 patients than the ones used on SARS patients. The wider but weaker permissiveness and host responses of virus infection may also imply a long-term existence of SARS-CoV-2 among human populations.