A bat MERS-like coronavirus circulates in pangolins and utilizes human DPP4 and host proteases for cell entry.

It is unknown whether pangolins, the most trafficked mammals, play a role in the zoonotic transmission of bat coronaviruses. We report the circulation of a novel MERS-like coronavirus in Malayan pangolins, named Manis javanica HKU4-related coronavirus (MjHKU4r-CoV). Among 86 animals, four tested positive by pan-CoV PCR, and seven tested seropositive (11 and 12.8%). Four nearly identical (99.9%) genome sequences were obtained, and one virus was isolated (MjHKU4r-CoV-1). This virus utilizes human dipeptidyl peptidase-4 (hDPP4) as a receptor and host proteases for cell infection, which is enhanced by a furin cleavage site that is absent in all known bat HKU4r-CoVs. The MjHKU4r-CoV-1 spike shows higher binding affinity for hDPP4, and MjHKU4r-CoV-1 has a wider host range than bat HKU4-CoV. MjHKU4r-CoV-1 is infectious and pathogenic in human airways and intestinal organs and in hDPP4-transgenic mice. Our study highlights the importance of pangolins as reservoir hosts of coronaviruses poised for human disease emergence.

Pathogenesis of SARS-CoV-2 in Transgenic Mice Expressing Human Angiotensin-Converting Enzyme 2.

COVID-19 has spread worldwide since 2019 and is now a severe threat to public health. We previously identified the causative agent as a novel SARS-related coronavirus (SARS-CoV-2) that uses human angiotensin-converting enzyme 2 (hACE2) as the entry receptor. Here, we successfully developed a SARS-CoV-2 hACE2 transgenic mouse (HFH4-hACE2 in C3B6 mice) infection model. The infected mice generated typical interstitial pneumonia and pathology that were similar to those of COVID-19 patients. Viral quantification revealed the lungs as the major site of infection, although viral RNA could also be found in the eye, heart, and brain in some mice. Virus identical to SARS-CoV-2 in full-genome sequences was isolated from the infected lung and brain tissues. Last, we showed that pre-exposure to SARS-CoV-2 could protect mice from severe pneumonia. Our results show that the hACE2 mouse would be a valuable tool for testing potential vaccines and therapeutics.

Structure of Mpro from SARS-CoV-2 and discovery of its inhibitors.

A new coronavirus, known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is the aetiological agent responsible for the 2019-2020 viral pneumonia outbreak of coronavirus disease 2019 (COVID-19)1-4. Currently, there are no targeted therapeutic agents for the treatment of this disease, and effective treatment options remain very limited. Here we describe the results of a programme that aimed to rapidly discover lead compounds for clinical use, by combining structure-assisted drug design, virtual drug screening and high-throughput screening. This programme focused on identifying drug leads that target main protease (Mpro) of SARS-CoV-2: Mpro is a key enzyme of coronaviruses and has a pivotal role in mediating viral replication and transcription, making it an attractive drug target for SARS-CoV-25,6. We identified a mechanism-based inhibitor (N3) by computer-aided drug design, and then determined the crystal structure of Mpro of SARS-CoV-2 in complex with this compound. Through a combination of structure-based virtual and high-throughput screening, we assayed more than 10,000 compounds-including approved drugs, drug candidates in clinical trials and other pharmacologically active compounds-as inhibitors of Mpro. Six of these compounds inhibited Mpro, showing half-maximal inhibitory concentration values that ranged from 0.67 to 21.4 µM. One of these compounds (ebselen) also exhibited promising antiviral activity in cell-based assays. Our results demonstrate the efficacy of our screening strategy, which can lead to the rapid discovery of drug leads with clinical potential in response to new infectious diseases for which no specific drugs or vaccines are available.

A pneumonia outbreak associated with a new coronavirus of probable bat origin.

Since the outbreak of severe acute respiratory syndrome (SARS) 18 years ago, a large number of SARS-related coronaviruses (SARSr-CoVs) have been discovered in their natural reservoir host, bats1-4. Previous studies have shown that some bat SARSr-CoVs have the potential to infect humans5-7. Here we report the identification and characterization of a new coronavirus (2019-nCoV), which caused an epidemic of acute respiratory syndrome in humans in Wuhan, China. The epidemic, which started on 12 December 2019, had caused 2,794 laboratory-confirmed infections including 80 deaths by 26 January 2020. Full-length genome sequences were obtained from five patients at an early stage of the outbreak. The sequences are almost identical and share 79.6% sequence identity to SARS-CoV. Furthermore, we show that 2019-nCoV is 96% identical at the whole-genome level to a bat coronavirus. Pairwise protein sequence analysis of seven conserved non-structural proteins domains show that this virus belongs to the species of SARSr-CoV. In addition, 2019-nCoV virus isolated from the bronchoalveolar lavage fluid of a critically ill patient could be neutralized by sera from several patients. Notably, we confirmed that 2019-nCoV uses the same cell entry receptor-angiotensin converting enzyme II (ACE2)-as SARS-CoV.

Characterization of a mouse-adapted strain of bat severe acute respiratory syndrome-related coronavirus.

Bats carry genetically diverse severe acute respiratory syndrome-related coronaviruses (SARSr-CoVs). Some of them utilize human angiotensin-converting enzyme 2 (hACE2) as a receptor and cannot efficiently replicate in wild-type mice. Our previous study demonstrated that the bat SARSr-CoV rRsSHC014S induces respiratory infection and lung damage in hACE2 transgenic mice but not wild-type mice. In this study, we generated a mouse-adapted strain of rRsSHC014S, which we named SMA1901, by serial passaging of wild-type virus in BALB/c mice. SMA1901 showed increased infectivity in mouse lungs and induced interstitial lung pneumonia in both young and aged mice after intranasal inoculation. Genome sequencing revealed mutations in not only the spike protein but the whole genome, which may be responsible for the enhanced pathogenicity of SMA1901 in wild-type BALB/c mice. SMA1901 induced age-related mortality similar to that observed in SARS and COVID-19. Drug testing using antibodies and antiviral molecules indicated that this mouse-adapted virus strain can be used to test prophylactic and therapeutic drug candidates against SARSr-CoVs. IMPORTANCE The genetic diversity of SARSr-CoVs in wildlife and their potential risk of cross-species infection highlights the importance of developing a powerful animal model to evaluate the antibodies and antiviral drugs. We acquired the mouse-adapted strain of a bat-origin coronavirus named SMA1901 by natural serial passaging of rRsSHC014S in BALB/c mice. The SMA1901 infection caused interstitial pneumonia and inflammatory immune responses in both young and aged BALB/c mice after intranasal inoculation. Our model exhibited age-related mortality similar to SARS and COVID-19. Therefore, our model will be of high value for investigating the pathogenesis of bat SARSr-CoVs and could serve as a prospective test platform for prophylactic and therapeutic candidates.

A SARS-CoV-2-Related Virus from Malayan Pangolin Causes Lung Infection without Severe Disease in Human ACE2-Transgenic Mice.

Coronavirus disease 2019 (COVID-19), which is caused by the novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is the most severe emerging infectious disease in the current century. The discovery of SARS-CoV-2-related coronaviruses (SARSr-CoV-2) in bats and pangolins in South Asian countries indicates that SARS-CoV-2 likely originated from wildlife. To date, two SARSr-CoV-2 strains have been isolated from pangolins seized in Guangxi and Guangdong by the customs agency of China, respectively. However, it remains unclear whether these viruses cause disease in animal models and whether they pose a transmission risk to humans. In this study, we investigated the biological features of a SARSr-CoV-2 strain isolated from a smuggled Malayan pangolin (Manis javanica) captured by the Guangxi customs agency, termed MpCoV-GX, in terms of receptor usage, cell tropism, and pathogenicity in wild-type BALB/c mice, human angiotensin-converting enzyme 2 (ACE2)-transgenic mice, and human ACE2 knock-in mice. We found that MpCoV-GX can utilize ACE2 from humans, pangolins, civets, bats, pigs, and mice for cell entry and infect cell lines derived from humans, monkeys, bats, minks, and pigs. The virus could infect three mouse models but showed limited pathogenicity, with mild peribronchial and perivascular inflammatory cell infiltration observed in lungs. Our results suggest that this SARSr-CoV-2 virus from pangolins has the potential for interspecies infection, but its pathogenicity is mild in mice. Future surveillance among these wildlife hosts of SARSr-CoV-2 is needed to monitor variants that may have higher pathogenicity and higher spillover risk. IMPORTANCE SARS-CoV-2, which likely spilled over from wildlife, is the third highly pathogenic human coronavirus. Being highly transmissible, it is perpetuating a pandemic and continuously posing a severe threat to global public health. Several SARS-CoV-2-related coronaviruses (SARSr-CoV-2) in bats and pangolins have been identified since the SARS-CoV-2 outbreak. It is therefore important to assess their potential of crossing species barriers for better understanding of their risk of future emergence. In this work, we investigated the biological features and pathogenicity of a SARSr-CoV-2 strain isolated from a smuggled Malayan pangolin, named MpCoV-GX. We found that MpCoV-GX can utilize ACE2 from 7 species for cell entry and infect cell lines derived from a variety of mammalian species. MpCoV-GX can infect mice expressing human ACE2 without causing severe disease. These findings suggest the potential of cross-species transmission of MpCoV-GX, and highlight the need of further surveillance of SARSr-CoV-2 in pangolins and other potential animal hosts.

Inactivated SARS-CoV-2 Vaccine Shows Cross-Protection against Bat SARS-Related Coronaviruses in Human ACE2 Transgenic Mice.

Severe acute respiratory syndrome coronavirus (SARS-CoV-1) and SARS-CoV-2 are highly pathogenic to humans and have caused pandemics in 2003 and 2019, respectively. Genetically diverse SARS-related coronaviruses (SARSr-CoVs) have been detected or isolated from bats, and some of these viruses have been demonstrated to utilize human angiotensin-converting enzyme 2 (ACE2) as a receptor and to have the potential to spill over to humans. A pan-sarbecovirus vaccine that provides protection against SARSr-CoV infection is urgently needed. In this study, we evaluated the protective efficacy of an inactivated SARS-CoV-2 vaccine against recombinant SARSr-CoVs carrying two different spike proteins (named rWIV1 and rRsSHC014S, respectively). Although serum neutralizing assays showed limited cross-reactivity between the three viruses, the inactivated SARS-CoV-2 vaccine provided full protection against SARS-CoV-2 and rWIV1 and partial protection against rRsSHC014S infection in human ACE2 transgenic mice. Passive transfer of SARS-CoV-2-vaccinated mouse sera provided low protection for rWIV1 but not for rRsSHC014S infection in human ACE2 mice. A specific cellular immune response induced by WIV1 membrane protein peptides was detected in the vaccinated animals, which may explain the cross-protection of the inactivated vaccine. This study shows the possibility of developing a pan-sarbecovirus vaccine against SARSr-CoVs for future preparedness. IMPORTANCE The genetic diversity of SARSr-CoVs in wildlife and their potential risk of cross-species infection highlight the necessity of developing wide-spectrum vaccines against infection of various SARSr-CoVs. In this study, we tested the protective efficacy of the SARS-CoV-2 inactivated vaccine (IAV) against two SARSr-CoVs with different spike proteins in human ACE2 transgenic mice. We demonstrate that the SARS-CoV-2 IAV provides full protection against rWIV1 and partial protection against rRsSHC014S. The T-cell response stimulated by the M protein may account for the cross protection against heterogeneous SARSr-CoVs. Our findings suggest the feasibility of the development of pan-sarbecovirus vaccines, which can be a strategy of preparedness for future outbreaks caused by novel SARSr-CoVs from wildlife.

Lethal Swine Acute Diarrhea Syndrome Coronavirus Infection in Suckling Mice.

Swine acute diarrhea syndrome coronavirus (SADS-CoV) is a recently emerging bat-borne coronavirus responsible for high mortality rates in piglets. In vitro studies have indicated that SADS-CoV has a wide tissue tropism in different hosts, including humans. However, whether this virus potentially threatens other animals remains unclear. Here, we report the experimental infection of wild-type BALB/c and C57BL/6J suckling mice with SADS-CoV. We found that mice less than 7 days old are susceptible to the virus, which caused notable multitissue infections and damage. The mortality rate was the highest in 2-day-old mice and decreased in older mice. Moreover, a preliminary neuroinflammatory response was observed in 7-day-old SADS-CoV-infected mice. Thus, our results indicate that SADS-CoV has potential pathogenicity in young hosts. IMPORTANCE SADS-CoV, which likely has originated from bat coronaviruses, is highly pathogenic to piglets and poses a threat to the swine industry. Little is known about its potential to disseminate to other animals. No efficient treatment is available, and the quarantine strategy is the only preventive measure. In this study, we demonstrated that SADS-CoV can efficiently replicate in suckling mice younger than 7 days. In contrast to infected piglets, in which intestinal tropism is shown, SADS-CoV caused infection and damage in all murine tissues evaluated in this study. In addition, neuroinflammatory responses were detected in some of the infected mice. Our work provides a preliminary cost-effective model for the screening of antiviral drugs against SADS-CoV infection.

Single-Cell Landscape of Lungs Reveals Key Role of Neutrophil-Mediated Immunopathology during Lethal SARS-CoV-2 Infection.

Due to the limitation of human studies with respect to individual difference or the accessibility of fresh tissue samples, how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection results in pathological complications in lung, the main site of infection, is still incompletely understood. Therefore, physiologically relevant animal models under realistic SARS-CoV-2 infection conditions would be helpful to our understanding of dysregulated inflammation response in lung in the context of targeted therapeutics. Here, we characterized the single-cell landscape in lung and spleen upon SARS-CoV-2 infection in an acute severe disease mouse model that replicates human symptoms, including severe lung pathology and lymphopenia. We showed a reduction of lymphocyte populations and an increase of neutrophils in lung and then demonstrated the key role of neutrophil-mediated lung immunopathology in both mice and humans. Under severe conditions, neutrophils recruited by a chemokine-driven positive feedback produced elevated "fatal signature" proinflammatory genes and pathways related to neutrophil activation or releasing of granular content. In addition, we identified a new Cd177high cluster that is undergoing respiratory burst and Stfahigh cluster cells that may dampen antigen presentation upon infection. We also revealed the devastating effect of overactivated neutrophil by showing the highly enriched neutrophil extracellular traps in lung and a dampened B-cell function in either lung or spleen that may be attributed to arginine consumption by neutrophil. The current study helped our understanding of SARS-CoV-2-induced pneumonia and warranted the concept of neutrophil-targeting therapeutics in COVID-19 treatment. IMPORTANCE We demonstrated the single-cell landscape in lung and spleen upon SARS-CoV-2 infection in an acute severe disease mouse model that replicated human symptoms, including severe lung pathology and lymphopenia. Our comprehensive study revealed the key role of neutrophil-mediated lung immunopathology in SARS-CoV-2-induced severe pneumonia, which not only helped our understanding of COVID-19 but also warranted the concept of neutrophil targeting therapeutics in COVID-19 treatment.

Correlation Between Early Plasma Interleukin 37 Responses With Low Inflammatory Cytokine Levels and Benign Clinical Outcomes in Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

BACKGROUND: The immune protective mechanisms during severe acute respiratory syndrome coronavirus (SARS-CoV-2) infection remain to be deciphered for the development of an effective intervention approach. METHODS: We examined early responses of interleukin 37 (IL-37), a powerful anti-inflammatory cytokine, in 254 SARS-CoV-2-infected patients before any clinical intervention and determined its correlation with clinical prognosis. RESULTS: Our results demonstrated that SARS-CoV-2 infection causes elevation of plasma IL-37. Higher early IL-37 responses were correlated with earlier viral RNA negative conversion, chest computed tomographic improvement, and cough relief, consequently resulted in earlier hospital discharge. Further assays showed that higher IL-37 was associated with lower interleukin 6 and interleukin 8 (IL-8) and higher interferon α responses and facilitated biochemical homeostasis. Low IL-37 responses predicted severe clinical prognosis in combination with IL-8 and C-reactive protein. In addition, we observed that IL-37 administration was able to attenuate lung inflammation and alleviate respiratory tissue damage in human angiotensin-converting enzyme 2-transgenic mice infected with SARS-CoV-2. CONCLUSIONS: Overall, we found that IL-37 plays a protective role by antagonizing inflammatory responses while retaining type I interferon, thereby maintaining the functionalities of vital organs. IL-37, IL-8, and C-reactive protein might be formulated as a precise prediction model for screening severe clinical cases and have good value in clinical practice.

Genetically Diverse Filoviruses in Rousettus and Eonycteris spp. Bats, China, 2009 and 2015.

Genetically divergent filoviruses detected in Rousettus and Eonycteris spp. bats in China exhibited 61%-99% nt identity with reported filoviruses, based on partial replicase sequences, and they demonstrated lung tropism. Co-infection with 4 different filoviruses was found in 1 bat. These results demonstrate that fruit bats are key reservoirs of filoviruses.

[Role of renal sympathetic nerve and oxidative stress in foot shock-induced hypertension in rats].

The present study was aimed to investigate the roles of renal sympathetic nerve and oxidative stress in the development of foot shock-induced hypertension. Ninety rats were divided into 6 groups (the number of each group was 15): control group, foot shock group, denervation of renal sympathetic nerve group, denervation of renal sympathetic nerve + foot shock group, Tempol treatment + foot shock group, denervation of renal sympathetic nerve + Tempol treatment + foot shock group. Rats were received electrical foot shock for 14 days (2-4 mA, 75 V, shocks of 50-100 ms every 30 s, for 4 h each session through an electrified grid floor every day). Renal sympathetic ablation was used to remove bilateral renal sympathetic nerve in rats (rats were allowed to recover for one week before the beginning of the foot shock procedure). The antioxidant Tempol was injected intraperitoneally at 1 h before foot shock. Systolic blood pressure was measured at 1 h after foot shock on day 0, 3, 7, 10 and 14. Contents of thiobarbituric acid reactive substance (TBARS), renin, angiotensin II (AngII) and glutathione peroxidase (GSH-Px) in plasma were measured by ELISA after 14-day foot shock. The results showed that systolic blood pressure of foot shock group was significantly increased (P < 0.05) compared with that of control group from day 7 to day 14 of foot shock. Denervation of renal sympathetic nerve and/or Tempol treatment significantly reduced the increase of systolic blood pressure induced by foot shock. Levels of TBARS, renin and AngII in plasma were increased significantly in foot shock group compared with that of control group (P < 0.05). Plasma GSH-Px concentration was decreased in foot shock group rats compared with that of control group (P < 0.05). Denervation of renal sympathetic nerve and/or tempol treatment significantly reduced the increase in TBARS, renin, AngII levels induced by foot shock in comparison with that of foot shock group (P < 0.05), but had no effects on the reduction of GSH-Px concentration. The results suggest that renal sympathetic nerve may play an important role in the development of foot shock-induced hypertension, and renal sympathetic nerve may influence oxidative stress and directly or indirectly activate renin-angiotensin-aldosterone system, so the foot shock-induced high blood pressure may be maintained and hypertension may therefore be produced.

Establishment of a human organoid-based evaluation system for assessing interspecies infection risk of animal-borne coronaviruses.

The COVID-19 pandemic presents a major threat to global public health. Several lines of evidence have shown that the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), along with two other highly pathogenic coronaviruses, SARS-CoV and Middle East Respiratory Syndrome (MERS-CoV) originated from bats. To prevent and control future coronavirus outbreaks, it is necessary to investigate the interspecies infection and pathogenicity risks of animal-related coronaviruses. Currently used infection models, including in vitro cell lines and in vivo animal models, fail to fully mimic the primary infection in human tissues. Here, we employed organoid technology as a promising new model for studying emerging pathogens and their pathogenic mechanisms. We investigated the key host-virus interaction patterns of five human coronaviruses (SARS-CoV-2 original strain, Omicron BA.1, MERS-CoV, HCoV-229E, and HCoV-OC43) in different human respiratory organoids. Five indicators, including cell tropism, invasion preference, replication activity, host response and virus-induced cell death, were developed to establish a comprehensive evaluation system to predict coronavirus interspecies infection and pathogenicity risks. Using this system, we further examined the pathogenicity and interspecies infection risks of three SARS-related coronaviruses (SARSr-CoV), including WIV1 and rRsSHC014S from bats, and MpCoV-GX from pangolins. Moreover, we found that cannabidiol, a non-psychoactive plant extract, exhibits significant inhibitory effects on various coronaviruses in human lung organoid. Cannabidiol significantly enhanced interferon-stimulated gene expression but reduced levels of inflammatory cytokines. In summary, our study established a reliable comprehensive evaluation system to analyse infection and pathogenicity patterns of zoonotic coronaviruses, which could aid in prevention and control of potentially emerging coronavirus diseases.

Strategy To Assess Zoonotic Potential Reveals Low Risk Posed by SARS-Related Coronaviruses from Bat and Pangolin.

In the last 2 decades, pathogens originating in animals may have triggered three coronavirus pandemics, including the coronavirus disease 2019 pandemic. Thus, evaluation of the spillover risk of animal severe acute respiratory syndrome (SARS)-related coronavirus (SARSr-CoV) is important in the context of future disease preparedness. However, there is no analytical framework to assess the spillover risk of SARSr-CoVs, which cannot be determined by sequence analysis alone. Here, we established an integrity framework to evaluate the spillover risk of an animal SARSr-CoV by testing how viruses break through key human immune barriers, including viral cell tropism, replication dynamics, interferon signaling, inflammation, and adaptive immune barriers, using human ex vivo lung tissues, human airway and nasal organoids, and human lung cells. Using this framework, we showed that the two pre-emergent animal SARSr-CoVs, bat BtCoV-WIV1 and pangolin PCoV-GX, shared similar cell tropism but exhibited less replicative fitness in the human nasal cavity or airway than did SARS-CoV-2. Furthermore, these viruses triggered fewer proinflammatory responses and less cell death, yet showed interferon antagonist activity and the ability to partially escape adaptive immune barriers to SARS-CoV-2. Collectively, these animal viruses did not fully adapt to spread or cause severe diseases, thus causing successful zoonoses in humans. We believe that this experimental framework provides a path to identifying animal coronaviruses with the potential to cause future zoonoses. IMPORTANCE Evaluation of the zoonotic risk of animal SARSr-CoVs is important for future disease preparedness. However, there are misconceptions regarding the risk of animal viruses. For example, an animal SARSr-CoV could readily infect humans. Alternately, human receptor usage may result in spillover risk. Here, we established an analytical framework to assess the zoonotic risk of SARSr-CoV by testing a series of virus-host interaction profiles. Our data showed that the pre-emergent bat BtCoV-WIV1 and pangolin PCoV-GX were less adapted to humans than SARS-CoV-2 was, suggesting that it may be extremely rare for animal SARSr-CoVs to break all bottlenecks and cause successful zoonoses.

Ecological study of cave nectar bats reveals low risk of direct transmission of bat viruses to humans.

Bats are reservoirs of various viruses. The widely distributed cave nectar bat ( Eonycteris spelaea) is known to carry both filoviruses and coronaviruses. However, the potential transmission of theses bat viruses to humans is not fully understood. In this study, we tracked 16 E. spelaea bats in Mengla County, Yunnan Province, China, using miniaturized GPS devices to investigate their movements and potential contact with humans. Furthermore, to determine the prevalence of coronavirus and filovirus infections, we screened for the nucleic acids of the Menglà virus (MLAV) and two coronaviruses (GCCDC1-CoV and HKU9-CoV) in anal swab samples taken from bats and for antibodies against these viruses in human serum samples. None of the serum samples were found to contain antibodies against the bat viruses. The GPS tracking results showed that the bats did not fly during the daytime and rarely flew to residential areas. The foraging range of individual bats also varied, with a mean cumulative nightly flight distance of 25.50 km and flight speed of up to 57.4 km/h. Taken together, these results suggest that the risk of direct transmission of GCCDC1-CoV, HKU9-CoV, and MLAV from E. spelaea bats to humans is very low under natural conditions.

ACE2-independent infection of T lymphocytes by SARS-CoV-2.

SARS-CoV-2 induced marked lymphopenia in severe patients with COVID-19. However, whether lymphocytes are targets of viral infection is yet to be determined, although SARS-CoV-2 RNA or antigen has been identified in T cells from patients. Here, we confirmed that SARS-CoV-2 viral antigen could be detected in patient peripheral blood cells (PBCs) or postmortem lung T cells, and the infectious virus could also be detected from viral antigen-positive PBCs. We next prove that SARS-CoV-2 infects T lymphocytes, preferably activated CD4 + T cells in vitro. Upon infection, viral RNA, subgenomic RNA, viral protein or viral particle can be detected in the T cells. Furthermore, we show that the infection is spike-ACE2/TMPRSS2-independent through using ACE2 knockdown or receptor blocking experiments. Next, we demonstrate that viral antigen-positive T cells from patient undergone pronounced apoptosis. In vitro infection of T cells induced cell death that is likely in mitochondria ROS-HIF-1a-dependent pathways. Finally, we demonstrated that LFA-1, the protein exclusively expresses in multiple leukocytes, is more likely the entry molecule that mediated SARS-CoV-2 infection in T cells, compared to a list of other known receptors. Collectively, this work confirmed a SARS-CoV-2 infection of T cells, in a spike-ACE2-independent manner, which shed novel insights into the underlying mechanisms of SARS-CoV-2-induced lymphopenia in COVID-19 patients.

Identification of potent human neutralizing antibodies against SARS-CoV-2 implications for development of therapeutics and prophylactics.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus that is spreading rapidly, which seriously impacts global public health and economy. Thus, developing effective drugs remains urgent. We identify two potent antibodies, nCoVmab1 and nCoVmab2, targeting the SARS-CoV-2 spike protein receptor-binding domain (RBD) with high affinities from a naïve human phage-displayed Fab library. nCoVmab1 and nCoVmab2 neutralize authentic SARS-CoV-2 with picomolar and nanomolar IC50 values, respectively. No detectable defects of nCoVmab1 and nCoVmab2 are found during the preliminary druggability evaluation. nCoVmab1 could reduce viral titer and lung injury when administered prophylactically and therapeutically in human angiotensin-converting enzyme II (hACE2)-transgenic mice. Therefore, phage display platform could be efficiently used for rapid development of neutralizing monoclonal antibodies (nmabs) with clinical potential against emerging infectious diseases. In addition, we determinate epitopes in RBD of these antibodies to elucidate the neutralizing mechanism. We also convert nCoVmab1 and nCoVmab2 to their germline formats for further analysis, which reveals the contribution of somatic hypermutation (SHM) during nCoVmab1 and nCoVmab2 maturation. Our findings not only provide two highly potent nmabs against SARS-CoV-2 as prophylactic and therapeutic candidates, but also give some clues for development of anti-SARS-CoV-2 agents (e.g., drugs and vaccines) targeting the RBD.

Characterization of Novel Rhabdoviruses in Chinese Bats.

Bats, the second largest order of mammals worldwide, harbor specific characteristics such as sustaining flight, a special immune system, unique habits, and ecological niches. In addition, they are the natural reservoirs of a variety of emerging or re-emerging zoonotic pathogens. Rhabdoviridae is one of the most diverse families of RNA viruses, which consists of 20 ecologically diverse genera, infecting plants, mammals, birds, reptiles, and fish. To date, three bat-related genera are described, named Lyssavirus, Vesiculovirus, and Ledantevirus. However, the prevalence and the distribution of these bat-related rhabdoviruses remain largely unknown, especially in China. To fill this gap, we performed a large molecular retrospective study based on the real-time reverse transcription polymerase chain reaction (RT-qPCR) detection of lyssavirus in bat samples (1044 brain and 3532 saliva samples, from 63 different bat species) originating from 21 provinces of China during 2006-2018. None of them were positive for lyssavirus, but six bat brains (0.6%) of Rhinolophus bat species, originating from Hubei and Hainan provinces, were positive for vesiculoviruses or ledanteviruses. Based on complete genomes, these viruses were phylogenetically classified into three putative new species, tentatively named Yinshui bat virus (YSBV), Taiyi bat virus (TYBV), and Qiongzhong bat virus (QZBV). These results indicate the novel rhabdoviruses circulated in different Chinese bat populations.

Antibody-Dependent Enhancement of SARS-CoV-2 Infection of Human Immune Cells: In Vitro Assessment Provides Insight in COVID-19 Pathogenesis.

Patients with COVID-19 generally raise antibodies against SARS-CoV-2 following infection, and the antibody level is positively correlated to the severity of disease. Whether the viral antibodies exacerbate COVID-19 through antibody-dependent enhancement (ADE) is still not fully understood. Here, we conducted in vitro assessment of whether convalescent serum enhanced SARS-CoV-2 infection or induced excessive immune responses in immune cells. Our data revealed that SARS-CoV-2 infection of primary B cells, macrophages and monocytes, which express variable levels of FcγR, could be enhanced by convalescent serum from COVID-19 patients. We also determined the factors associated with ADE, and found which showed a time-dependent but not viral-dose dependent manner. Furthermore, the ADE effect is not associated with the neutralizing titer or RBD antibody level when testing serum samples collected from different patients. However, it is higher in a medium level than low or high dilutions in a given sample that showed ADE effect, which is similar to dengue. Finally, we demonstrated more viral genes or dysregulated host immune gene expression under ADE conditions compared to the no-serum infection group. Collectively, our study provides insight into the understanding of an association of high viral antibody titer and severe lung pathology in severe patients with COVID-19.