Differential Tropism of SARS-CoV and SARS-CoV-2 in Bat Cells

Abstract

C oronavirus disease (COVID-19) is a global pandemic, affecting 213 countries with >2.7 million confirmed cases and 190,000 fatalities as of April 25, 2020 (1). Its causative agent was identified as severe acute respiratory syndrome coronavirus (SARS-CoV) 2 (SARS-CoV-2), which belongs to the same coronavirus species as SARS-CoV and SARS-related CoVs (SARSr-CoVs) in horseshoe bats (genus Rhinolophus) (2,3). Given the history among some early case-patients of visiting the Huanan seafood market in Wuhan, China, and its genetic close relatedness to SARSr-CoVs in bats and pangolins (2,4), SARS-CoV-2 was suspected to have emerged from wild animals, particularly bats, similar to SARS-CoV. SARS-CoV was a recombinant virus that originated from Chinese horseshoe bats (Rhinolophus sinicus) before it infected palm civets and then humans (5). Studying cellular tropism may provide clues to the host range and possible origin of zoonotic viruses. For example, SARS-CoV could replicate efficiently in kidney cells of its primary origin, R. sinicus, but not in other tested bat cells (6). To elucidate the possible origin of SARS-CoV-2, we tested susceptibilities of bat cell lines developed from different species commonly found in southern China to infection by SARS-CoV-2 in comparison with SARS-CoV. The selected bat species harbored a diverse set of coronaviruses, including SARSr-CoVs and Middle East respiratory syndrome-related coronaviruses (MERSr-CoVs), which pose potential health threats to humans (7). We also performed structural modeling of the virus/host receptor-binding interface. The Study SARS-CoV strain HKU-39849 was isolated in Hong Kong during the SARS epidemic as previously described (8). SARS-CoV-2 strain HK20 was isolated from a patient with COVID-19 in Hong Kong in early February 2020 (3). Thirteen primary or immortalized bat cell lines from 6 different bat species were subjected to infection with SARS-CoV and SARS-CoV-2 at multiplicity of infection of 0.1 as described previously (6,9,10), except with the addition of 2 µg/mL trypsin. The bat species included Miniopterus pusillus, Pipistrellus abramus (harboring Pipistrellus-BatCoV-HKU5), R. sinicus (harboring SARSr-BatCoVs, Rhinolophus-BatCoV-HKU2, Rhinolophus sinicus-BatCoV-HKU32), Tylonycteris pachypus (harboring Tylonycteris-BatCoV-HKU4), Rousettus leschenaultii (harboring many viruses, including Rousettus-BatCoV-HKU9 and Rousettus-BatCoV-HKU10), and Myotis ricketii (harboring Myotis-BatCoV-HKU6). Vero cells from African green monkey kidney were used as positive control (Figure 1; Appendix, https://wwwnc.cdc.gov/EID/ article/26/12/20-2308-App1.pdf). We determined viral replication efficiency by quantitative reverse transcription PCR (qRT-PCR) on cell culture supernatants (Table 1) (6). Cells were considered susceptible to viral infection if qRT-PCR on day 5 postinfection showed >1 log 10 increase in viral titer with statistical significance (p<0.05 by Student t-test).

Evolution, Ecology, and Zoonotic Transmission of Betacoronaviruses: A Review

“…Evidence from other viral zoonoses suggests an origin in bats via possibly an intermediate host ( 7 , 8 ). This review will examine the origin of SARS-CoV-2 in the context of possible zoonotic transmission, evolution, ecological factors, and the role of reservoir species in other coronaviruses ( 9 ).…”

Isolation and genetic characterization of SARS-CoV-2 from Indian patients in a single family without H/O travel abroad

“…SARS-CoV-2 is a betacoronavirus with single-stranded positive sense RNA genome of around 29.8 kb [ 1 , 3 ]. The genome sequences of SARS-CoV-2 shared 96% similarity with bat coronavirus (RaTG13) suggesting possible Bat origin of SARS-CoV-2 [ 4 ]. The SARS-CoV-2 genome had unique polybasic cleavage motif PRRA in the S1-S2 junction region of spike protein.…”

Species-specific molecular barriers to SARS-CoV-2 replication in bat cells

“…Only a handful of models are available to study the replication of betacoronaviruses in bat cells. Viral replication was detected in Rhinolophus sinicus lung and brain cells, as well as in Pipistrellus abramus kidney cells [27], but viral titers were very low. By contrast, SARS-CoV-2 replicated efficiently in R. sinicus intestinal organoids [28], confirming further the susceptibility of Rhinolophus cells to the virus.…”