26 Previous findings of Middle East Respiratory Syndrome coronavirus (MERS-CoV)-27 related viruses in bats, and the ability of Tylonycteris-BatCoV HKU4 spike protein to utilize 28 MERS-CoV receptor, human dipeptidyl peptidase 4 hDPP4, suggest a bat ancestral origin of 29 MERS-CoV. We developed 12 primary bat cell lines from seven bat species, including 30 Tylonycteris pachypus, Pipistrellus abramus and Rhinolophus sinicus (hosts of Tylonycteris-31 BatCoV HKU4, Pipistrellus-BatCoV HKU5 and SARS-related-CoV respectively), and tested 32 their susceptibilities to MERS-CoVs, SARS-CoV and human coronavirus 229E (HCoV-229E). 33 Five cell lines, including P. abramus and R. sinicus but not T. pachypus cells, were susceptible 34 to human MERS-CoV EMC/2012. However, three tested camel MERS-CoV strains showed 35 different infectivities, with only two strains capable of infecting three and one cell lines 36 respectively. SARS-CoV can only replicate in R. sinicus cells, while HCoV-229E cannot 37 replicate in any bat cells. Bat dipeptidyl peptidase 4 (DPP4) sequences were closely related to 38 those of human and non-human primates but distinct from dromedary DPP4 sequence. Critical 39 residues for binding to MERS-CoV spike protein were mostly conserved in bat DPP4. DPP4 40 was expressed in the five bat cells susceptible to MERS-CoV, with significantly higher mRNA 41 expression levels than those in non-susceptible cells (P=0.0174), supporting that DPP4 42 expression is critical for MERS-CoV infection in bats. However, overexpression of T. pachypus 43 DPP4 failed to confer MERS-CoV susceptibility in T. pachypus cells, suggesting other cellular 44 factors in determining viral replication. The broad cellular tropism of MERS-CoV should 45 prompt further exploration of host diversity of related viruses to identify its ancestral origin. 46 47 All rights reserved. No reuse allowed without permission. The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. . https://doi.org/10.1101/326538 doi: bioRxiv preprint Existing evidence suggests that MERS-CoV may be originated from bats. In particular, 49 Tylonycteris-BatCoV HKU4 spike protein was shown to utilize MERS-CoV receptor, human 50 dipeptidyl peptidase 4 (DPP4). To better understand the potential infectivities of MERS-CoV in 51 bats, we developed 12 primary bat cell lines from seven bat species, including Tylonycteris 52 pachypus and Rhinolophus sinicus (host of Tylonycteris-BatCoV HKU4 and SARS-related-53 CoV respectively). MERS-CoV demonstrated much broader cellular tropism than SARS-CoV 54 and HCoV-229E, being able to infect five cell lines, including R. sinicus but not T. pachypus 55 cells. The close phylogenetic relationship between bat and human DPP4 genes supported the 56 ability of MERS-CoV to infect bat cells, while DPP4 expression appeared critical for MERS-57 CoV replication. However, overexpression of T. pachypus DPP4 failed to confer MERS-CoV 58 susceptibility in T. pachypus cells. The broad cellular tropism of MERS-CoV may reflect the 59 host diversity of MERS-CoV-related viruses and offers insights into its ancestral origin. 60 61 All rights reserved. No reuse allowed without permission.
Output: Replication of MERS and SARS coronaviruses in bat cells offers insights to their 1 ancestral origins 2 3