In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.

[Q]: SARS-CoV-2, a member of the coronavirus family, is responsible for the current COVID-19 pandemic. Based on our analysis of hepatitis C virus and coronavirus replication, and the molecular structures and activities of viral inhibitors, we previously demonstrated that three nucleotide analogues inhibit the SARS-CoV RNA-dependent RNA polymerase (RdRp). Here, using polymerase extension experiments, we have demonstrated that the active triphosphate form of Sofosbuvir (a key component of the FDA approved hepatitis C drug EPCLUSA), is incorporated by SARS-CoV-2 RdRp, and blocks further incorporation. Using the same molecular insight, we selected the active triphosphate forms of three other anti-viral agents, Alovudine, AZT (an FDA approved HIV/AIDS drug) and Tenofovir alafenamide (TAF, an FDA approved drug for HIV and hepatitis B) for evaluation as inhibitors of SARS-CoV-2 RdRp. We demonstrated the ability of these three viral polymerase inhibitors, 3'-fluoro-3'-deoxythymidine triphosphate, 3'-azido-3'deoxythymidine triphosphate and Tenofovir diphosphate (the active triphosphate forms of Alovudine, AZT and TAF, respectively) to be incorporated by SARS-CoV-2 RdRp, where they also terminate further polymerase extension. These results offer a strong molecular basis for these nucleotide analogues to be evaluated as potential therapeutics for COVID-19.
[A]: Nucleotide Analogues as Inhibitors of SARS-CoV-2 Polymerase

[Q]: A new porcine coronavirus SADS-CoV was recently identified from suckling piglets 20 with severe diarrhea in southern China and its genome sequence is most identical (~95% 21 identity) to that of bat -coronavirus HKU2. It again indicates bats are the natural 22 reservoir of many coronaviruses that have great potential for cross-species transmission 23 to animals and humans by recombination and/or mutation. Here we report the cryo-EM 24 structures of HKU2 and SADS-CoV spike glycoprotein trimers at 2.38 A and 2.83 A 25 resolution, respectively. HKU2 and SADS-CoV spikes exhibit very high structural 26 similarity, with subtle differences mainly distributed in the NTD and CTD of the S1 27 subunit responsible for cell attachment and receptor binding. We systematically 28 analyzed and compared the NTD, CTD, SD1 and SD2 domains of the S1 subunit and 29 the S2 subunit of HKU2 spike with those of -, -, -, and -coronavirus spikes. The 30 results show that the NTD and CTD of HKU2/SADS-CoV are probably the most 31 ancestral in the evolution of spike. Although the S2 subunit mediating membrane fusion 32 is highly conserved, the connecting region after fusion peptide in HKU2/SADS-CoV 33 S2 subunit also adopts a conformation distinct from other coronaviruses. These results 34 structurally demonstrate a close evolutionary relationship between HKU2 /SADS-CoV 35 and -coronavirus spikes and provide new insights into the evolution and cross-species 36 transmission of coronaviruses. : bioRxiv preprint 39 Coronaviruses, categorized into the order Nidovirales family Coronaviridae and 40 subfamily Coronavirinae, are a large group of viral pathogens with a wide host range 1 . 41 Their infections in humans, other mammals and birds can cause respiratory, hepatic, 42 enteric and neurological diseases with varying severity 2 . The severe acute respiratory 43 syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus 44 (MERS-CoV) have posed severe threats to human health in the 21 st century 1,3 . In the 45 meantime, coronaviruses infecting domestic animals also bring substantial economic 46 losses 4 . For example, the swine acute diarrhea syndrome coronavirus (SADS-CoV) 47 (also known as SeACoV and PEAV) isolated in 2017 caused outbreaks of severe watery 48 diarrhea of suckling piglets with a mortality up to 90% in several commercial pig farms 49 in Guangdong Province of China 5-10 . SADS-CoV is an -coronavirus and other 50 representative members in the -genus are porcine epidemic diarrhea virus 51 (PEDV), porcine transmissible gastroenteritis coronavirus (TGEV), porcine respiratory 52 coronavirus (PRCV), human NL63 and 229E coronaviruses (HCoV-NL63 and HCoV-53 229E) 1 . Representative members in other three genera include mouse hepatitis 54 coronavirus (MHV), bovine coronavirus (BCoV), SARS-CoV, MERS-CoV, HCoV-55 OC43 and HCoV-HKU1 in the -genus, avian infectious bronchitis virus (IBV) in the 56 -genus and porcine deltacoronavirus (PdCoV) in the -genus 1 . 57 Cross-species transmission promoted by genetic recombination and/or mutations 58 underlies the host range expansion of coronaviruses 3,11-13 . Bats are the natural reservoir 59 of more than 30 different -and -coronaviruses that have great potential for 60 interspecies transmission by recombination and/or mutation 12,14-16 . Data on genetic 61 evolution, receptor binding and pathogenesis have demonstrated that human SARS-62 CoV and MERS-CoV most likely originate from bats 1 . Palm civets and dromedary 63 camels are the intermediate hosts of SARS-CoV and MERS-CoV from bats to humans 1 , 64 respectively. The newly identified porcine SADS-CoV isolates are also found to share 65 ~95% sequence identity with Rhinolophus bat coronavirus HKU2, and this further 66 stressed the severe results of coronavirus spillover from bats to domestic animals 5-10 .
[A]: Cryo-EM structures of HKU2 and SADS-CoV spike 1 glycoproteins and insights into coronavirus evolution 2 3 4

[Q]: Multiplex PCR has become the test of choice for the detection of multiple respiratory viruses in clinical specimens. However, there are few direct comparisons of different PCR assays. This study compares 4 different multiplex PCR assays for the recovery of common respiratory viruses. We tested 213 respiratory specimens using four different multiplex PCR assays: the xTAG respiratory viral panel fast (Abbott Molecular Laboratories), Fast-track Respiratory Pathogen assay (Fast-track Diagnostics), Easyplex respiratory pathogen 12 kit (Ausdiagnostics), and an in-house multiplex real-time PCR assay. The performance of the four assays was very similar, with 93-100% agreement for all comparisons. Other issues, such as through-put, technical requirements and cost, are likely to be as important for making a decision about which of these assays to use given their comparative performance.
[A]:
Comparison of four multiplex PCR assays for the detection of viral pathogens in respiratory specimens