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Professor Yi-Gang Tong, BUCT College of Life Sciences and Technology published an article as co-author on the novel coronavirus in Nature

On March 26, 2020, Yi Guan and Tsan-Yuk Lam from the University of Hong Kong, Yan-ling Hu from Guangxi Medical University, and Yi-Gang Tong from Beijing University of Chemical Technology, with others, published a research paper Identifying SARS-CoV-2 related coronaviruses in Malayan pangolins in Nature, reporting the latest advances about the potential host of new coronavirus SARS-CoV-2.

Since the outbreak of the novel coronavirus pneumonia, source of the virus has been a matter of public and academic concern. Studies have shown that some early cases are related to the South China Seafood Market in Wuhan, suggesting that wild animals sold there may be the source of the disease. Although studies suggest that bats may be the hosts of SARS-CoV-2, but it is not clear whether there is an intermediate host to transmit the virus to humans. This paper reported the coronaviruses similar to SARS-CoV-2 carried in the Malayan pangolins (Manis javanica) seized during anti-smuggling operations in southern China. The spike protein, esp. the receptor binding domain (RBD) of pangolin viruses showed high similarity with SARS-CoV-2, suggesting that pangolin may be a potential host of SARS-CoV-2.

Pangolins are scaly mammals, often illegally trafficked: they are used as both a food source and their scales are utilized in traditional Chinese medicine. Pangolins are considered critically endangered on the International Union for Conservation of Nature Red List of Endangered Species. The study showed that the authors found six complete or partial genome sequences of coronaviruses in 2017-2018 from smuggling pangolin samples in Guangxi. These viruses share 85.5% nucleotide sequence homology with SARS-CoV-2. Additionally, the authors also found two coronaviruses with higher homology (92.4%) to SARS-CoV-2 in the Guangdong smuggling pangolin samples in 2019. Phylogenetic analysis shows that, although the overall genome homology between these two pangolin coronaviruses and SARS-CoV-2 is lower as compared to that between bat virus RaTG13 and SARS-CoV-2, the homology in the RBD region between pangolin viruses and SARS-CoV-2 is slightly higher than that between RaTG13 and SARS-CoV-2. Moreover, for the five key sites that bind to the receptor, only one site of RaTG13 is the same as SARS-CoV-2, while in pangolin virus, all the five sites are the same as SARS-CoV-2. Phylogenetic analysis shows that this may not be the result of recombination between the viruses but may be the result of convergent evolution. At the same time, the homology of ACE2 protein between pangolin and human is higher (84.8%) than that between bat and human (80.8%-81.4%), which also suggests that the high homology in spike protein RBD between pangolin viruses and SARS-CoV-2 may be the result of convergence evolution. Both the pangolin coronavirus and RaTG13 lack the Furin protease cleavage sites possessed by SARS-CoV-2, suggesting that pangolin coronavirus and bat virus RaTG13 may infect humans with lower efficiency than SARS-CoV-2.

To date, pangolins are the only mammals other than bats documented to carry a SARS-CoV-2 related coronavirus. It is striking that two related lineages of CoVs are found in pangolins independently sampled in different Chinese provinces and that both are also related to SARS-CoV-2. This suggests that these animals may be important hosts for these viruses. But, from current data, it cannot be excluded that pangolins acquired the SARS-CoV-2 related viruses independently from bats or another animal host, so that their role in the emergence of human SARS-CoV-2 remains unproven. Undoubtedly, the extent of virus prevalence in pangolin populations requires additional investigation. However, the repeated occurrence of infections with SARS-CoV-2 related coronaviruses in Guangxi and Guangdong pangolins suggests that this animal may play an important role in the ecology of coronaviruses.

The above results show that pangolins can be infected by coronaviruses associated with SARS-CoV-2, although the epidemiology, pathogenicity, interspecies infectivity and transmissibility of coronaviruses in pangolins remains to be studied. The data presented in the paper strongly suggest that handling these animals requires considerable caution, and that their sale in wet markets should be strictly prohibited. At the same time further surveillance of coronavirus in pangolins are needed to understand their role in the emergence of SARS-CoV-2 and prevent the risk of future zoonotic transmission.

 

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