Taken together, these data indicated that pangolin MjHKU4r-CoV-1 carries a specific furin cleavage site (most probably, RQQR) that is not found in bat HKU4-CoV.
https://www.cell.com/cell/fulltext/S0092-8674(23)00049-1
Thus, MjHKU4r-CoV-1 uses hDPP4 and human proteolytic proteases cleavage for infecting human cells, indicating that this virus is capable of directly infecting human cells without the need for further adaptation.
Our study highlights the MERS-like virus potentially emerges in humans and the importance of pangolins as reservoir hosts of CoVs poised for human emergence, including at least Sarbecovirus
, and Merbecovirus. The prevalence of this virus related to bats but more adapted to humans in pangolins suggests the latter to be important or even adaptation hosts during bat CoV cross-species transmission.It has been suggested that the risk of spillover is greater when there are more opportunities for human-animal contact, for example, during deforestation or in the trade of wildlife, as these animals are important natural virus reservoir hosts. For instance, bats carry the most CoV species, followed by small mammals, such as rodents, shrews, hedgehogs, civets, and pangolins. Compared with bats, small mammals that are frequently traded pose a bigger threat to humans in terms of CoV spillover. The 2002 human SARS-CoV-1 spillover could have been interrupted if the prevalence and virological assessment of civet SARS-CoV-1, which was related to bat SARS-related CoV, would have been determined early, before it jumped to humans. In this regard, our data provide a novel insight that game animals such as pangolins could be more human-threatening reservoir hosts than bats because they are in closer contact with humans and carry more human-adapted CoVs, and early investigation may break the chain of viral cross-species transmission.The genetic relationship and divergence between the MjHKU4r-CoVs and bat HKU4-CoVs suggest a possible bat-pangolin transmission of this virus species, which was occurred a long time ago. It remains unclear whether pangolins are infected by zoonotic transmission directly from bats or from other mammals in the trade chain. Compared with bat HKU4r-CoVs, MjHKU4r-CoVs appear to be better adapted to humans. The emergence and high transmissibility of SARS-CoV-2 variants are largely attributed to an additional furin cleavage site, which is not observed in other sarbecoviruses, and a higher ACE2-binding capacity in later variants. Similarly, although bat HKU4r-CoVs have been isolated and could infect hDPP4-Tg mice, they generally show poor receptor-binding capacity or sometimes require exogenous trypsin treatment for human cell entry, indicating the requirement for further adaptation in human cells.,,, In contrast, MjHKU4r-CoVs utilize hDPP4 (as efficiently as MERS-CoV) and human proteolytic cleavage proteases for cell entry. This has also been observed for pangolin sarbecoviruses. Moreover, a furin cleavage site was observed in MjHKU4r-CoV and MERS-CoV, but not in any of the bat HKU4r-CoVs., The furin cleavage site may allow MjHKU4r-CoV to replicate to high titers in the respiratory tract, as SARS-CoV-2 with the furin cleavage site deleted showed dysfunctional replication. Notably, a genetically related pangolin HKU4r-CoV has been found in another metagenomics analysis (HKU4/P251T/pangolin/2018, GenBank: OM009282.1), showing 98.3%, 86.3%, and 68.6% genome sequence identity to MjHKU4r-CoV-1, bat HKU4, and MERS-CoV, respectively. Importantly, the RQQR furin cleavage site was also predicted in the S protein of this HKU4r-CoV. This pangolin HKU4r-CoV was also discovered in Malayan pangolins smuggled from Southeast Asia with no information on their original inhabitant, suggesting a wide prevalence of HKU4r-CoV in pangolins. Thus, pangolins appear to be important reservoir hosts that carry bat-related, human-adapted CoVs, although the ecological relationship between pangolins and bats in the context of CoV transmission remains unclear.
https://www.nature.com/articles/s41598-023-32622-4
The pangolin and coronavirus lineages are polyphyletic in the species tree. There are two clades within the pangolin coronaviruses with 77% support. These two clades contain distinct bat coronavirus lineages. One of these pangolin coronavirus clades contains the bat coronavirus (RaTG13) and human coronavirus lineages. The other pangolin coronavirus clade contains pangolin and remaining bat coronavirus lineages. The fact that the pangolin and bat coronavirus clades are still polyphyletic is consistent with the degree of variation relative to the human coronavirus lineages—a factor of at least 3X more than among human lineages.
SARS-CoV-2 likely originated with a single introduction into humans. While bat species are the likely reservoir, multiple interspecies transmission events were likely involved in the generation of SARS-CoV-2, possibly including transmission through pangolin hosts.
https://www.sciencedirect.com/science/article/pii/S1995820X23001359
TyRo-CoV-162275 found in greater bamboo bat is the first reported bat HKU4r-CoV with a furin protease cleavage site.
Sequence analysis showed that TyRo-CoV-162275 shared the highest identity with Malayan pangolin (Manis javanica) HKU4-related coronaviruses (MjHKU4r-CoVs) from Guangxi Province, whereas TyRo-CoV-162269 was closely related to HKU33-CoV discovered in a greater bamboo bat (Tylonycteris robustula) from Guizhou Province. Notably, TyRo-CoV-162275 has a putative furin protease cleavage site in its S protein and is likely to utilize human dipeptidyl peptidase-4 (hDPP4) as a cell-entry receptor, similar to MERS-CoV. To the best of our knowledge, this is the first report of a bat HKU4r-CoV strain containing a furin protease cleavage site. These findings expand our understanding of coronavirus geographic and host distributions.
The highest diversity of bat-borne corona-viruses in China was found in Yunnan and Guangdong (Fan et al., 2019; Zhu et al., 2023). Recently, SARS-CoV-2-related CoVs identified in several pangolin species in Guangdong and Guangxi provinces have shown the ability to exploit human angiotensin-converting enzyme 2 (hACE2) as a receptor for viral infection and may share common ancestry with RaTG-13, BANAL-236 and other SARS-CoV-2 related CoVs found in bats from China and Laos (Lam et al., 2020; Shi et al., 2022; Xiao et al., 2020).
We found that pangolin HKU4-related coronaviruses in T. robustula contain a furin protease cleavage site. Further studies and characterisations of bat CoVs should be conducted to provide additional insights into their host range and the evolutionary history of bat populations in China and Southeast Asia.
https://elixirfield.blogspot.com/2023/03/pangolins-likely-intermediate-host-as.html
https://elixirfield.blogspot.com/2020/04/pangolins-are-further-corroborated-as.html
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