Diversity and independent evolutionary profiling of rodent-borne pathogens in tropical island, China (preprint)

The risk of emerging infectious diseases (EID) is increasing globally. More than 60% of EIDs worldwide are caused by animal-borne pathogens, and most viral pathogens are rodent-borne. This study aimed to characterise the virome and analyse the phylogenetic evolution and diversity of rodent-borne viruses in Hainan Province, China. We collected 588 anal and throat samples from rodents, combined them into 28 pools according to their species and location, and processed them for next-generation sequencing and bioinformatics analysis. The diverse viral reads closely related to mammals were assigned to 15 viral families. Molecular clues of the important rodent-borne viruses were further identified by polymerase chain reaction for phylogenetic analysis and annotation of genetic characteristics such as coronavirus, arenavirus, picornavirus. We identified a pestivirus in Leopoldoms edwardsi and two bocaviruses in Rattus andamanensis and Leopoldoms edwardsi from the national nature reserves of Jianfengling and Bangxi with low amino acid identity to known pathogens are proposed as the novel species, and their rodent hosts have not been previously reported to carry these viruses. These results expand our knowledge of viral classification and host range and suggest that there are highly diverse, undiscovered viruses that have evolved independently in their unique wildlife hosts in inaccessible areas, which may cause zoonosis if they cross their host barrier. Our virome and phylogenetic analyses of rodent-borne viruses provide basic data for the prevention and control of human infectious diseases caused by rodent-borne viruses in the subtropical area of China.

A comprehensive survey of bat sarbecoviruses across China for the origin tracing of SARS-CoV and SARS-CoV-2 (preprint)

Severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2 have been thought to originate from bat, but whether the cross-species transmission occurred directly from bat to human or through an intermediate host remains elusive. In this study, we performed CoV screening of 102 samples collected from animal-selling stalls of Wuhan Huanan Market (WHM) and pharyngeal and anal swabs from13,064 bats collected at 703 locations across China, covering almost all known southern hotspots for sarbecovirus, between 2016 and 2021. This is the first systematic survey of bat CoV in China during the outbreak of Corona Virus Disease 2019. We found four non-sarbeco CoVs in samples of WHM, and 142 SARS-CoV related CoVs (SARSr-CoV) and 4 recombinant CoVs in bats, of which YN2020B-G share the highest sequence identity with SARS-CoV among all known bat CoVs, suggesting endemic SARSr-CoVs in bats in China. However, we did not find any SARS-CoV-2 related CoVs (SC2r-CoV) in any samples, including specimens collected from the only two domestic places where RaTG13 and RmYN02 were previously reported (the Tongguan caves and the karst caves around the Xishuangbanna Tropical Botanical Garden), indicating that SC2r-CoVs might not actively circulate among bats in China. Phylogenetic analysis showed that there are three different lineages of sarbecoviruses, L1 (SARSr-CoV), L2 (SC2r-CoV), and L-R (a novel CoV lineage from L1 and L2 recombination), in China. Of note, L-R CoVs are only found in R. pusillus. Further macroscopical analysis of the genetic diversity, host specificity for colonization and accidental infection, and geographical characteristics of available CoVs in database revealed the presence of a general geographical distribution pattern for bat sarbecoviruses, with the highest genetic diversity and sequence homology to SARS-CoV or SARS-CoV-2 along the southwest border of China, the least in the northwest of China. Considering the receptor binding motifs for spike gene of sarbecoviruses in Indochina Peninsula show the greatest diversity, our data provide the rationale that extensive surveys in further south and southwest to or of China might be needed for finding closer ancestors of SARS-CoV and SARS-CoV-2.

Decoding the RNA viromes in rodent lungs to understand rodent-borne pathogens (preprint)

Most human infectious viral diseases – including COVID-19 and Ebola – originated in animals. As the largest group of mammalian species, rodents are natural reservoirs for many diverse zoonotic viruses. Better understanding the core rodent virome will reduce the risk of future emergence or re-emergence of rodent-borne pathogens. A recent study focused on viruses found in the lungs of rodents in Mainland Southeast Asia, a hotspot for zoonotic emerging infectious diseases. Lung samples were collected from 3,284 rodents and insectivores throughout Thailand, Lao PDR, and Cambodia. Using metatranscriptomics, researchers outlined unique characteristics of the rodent viruses identified. Many mammalian- or arthropod-related viruses from distinct evolutionary lineages were reported for the first time, and viruses related to known pathogens were found. These results expand our understanding of the core virome in rodent species in Mainland Southeast Asia and suggest that a highly diverse array of viruses remains to be found in these species. Viral surveillance in wildlife hosts will minimize the impact of potential wildlife-originating infectious diseases.

The Rhinolophus affinis bat ACE2 and multiple animal orthologs are functional receptors for bat coronavirus RaTG13 and SARS-CoV-2 (preprint)

Bat coronavirus (CoV) RaTG13 shares the highest genome sequence identity with SARS-CoV-2 among all known coronaviruses, and also uses human angiotensin converting enzyme 2 (hACE2) for virus entry. Thus, SARS-CoV-2 is thought to have originated from bat. However, whether SARS-CoV-2 emerged from bats directly or through an intermediate host remains elusive. Here, we found that Rhinolophus affinis bat ACE2 (RaACE2) is an entry receptor for both SARS-CoV-2 and RaTG13, although RaACE2 binding to the receptor binding domain (RBD) of SARS-CoV-2 is markedly weaker than that of hACE2. We further evaluated the receptor activities of ACE2s from additional 16 diverse animal species for RaTG13, SARS-CoV, and SARS-CoV-2 in terms of S protein binding, membrane fusion, and pseudovirus entry. We found that the RaTG13 spike (S) protein is significantly less fusogenic than SARS-CoV and SARS-CoV-2, and seven out of sixteen different ACE2s function as entry receptors for all three viruses, indicating that all three viruses might have broad host rages. Of note, RaTG13 S pseudovirions can use mouse, but not pangolin ACE2, for virus entry, whereas SARS-CoV-2 S pseudovirions can use pangolin, but limited for mouse, ACE2s enter cells. Mutagenesis analysis revealed that residues 484 and 498 in RaTG13 and SARS-CoV-2 S proteins play critical roles in recognition of mouse and human ACE2. Finally, two polymorphous Rhinolophous sinicus bat ACE2s showed different susceptibilities to virus entry by RaTG13 and SARS-CoV-2 S pseudovirions, suggesting possible coevolution. Our results offer better understanding of the mechanism of coronavirus entry, host range, and virus-host coevolution.

Single-cell transcriptional atlas of the Chinese horseshoe bat (Rhinolophus sinicus) provides insight into the cellular mechanisms which enable bats to be viral reservoirs (preprint)

Bats are a major "viral reservoir" in nature and there is a great interest in not only the cell biology of their innate and adaptive immune systems, but also in the expression patterns of receptors used for cellular entry by viruses with potential cross-species transmission. To address this and other questions, we created a single-cell transcriptomic atlas of the Chinese horseshoe bat (Rhinolophus sinicus) which comprises 82,924 cells from 19 organs and tissues. This atlas provides a molecular characterization of numerous cell types from a variety of anatomical sites, and we used it to identify clusters of transcription features that define cell types across all of the surveyed organs. Analysis of viral entry receptor genes for known zoonotic viruses showed cell distribution patterns similar to that of humans, with higher expression levels in bat intestine epithelial cells. In terms of the immune system, CD8+ T cells are in high proportion with tissue-resident memory T cells, and long-lived effector memory nature killer (NK) T-like cells (KLRG1, GZMA and ITGA4 genes) are broadly distributed across the organs. Isolated lung primary bat pulmonary fibroblast (BPF) cells were used to evaluate innate immunity, and they showed a weak response to interferon {beta} and tumor necrosis factor- compared to their human counterparts, consistent with our transcriptional analysis. This compendium of transcriptome data provides a molecular foundation for understanding the cell identities, functions and cellular receptor characteristics for viral reservoirs and zoonotic transmission.