276⊙s.al -S1 subunit S2 subunit NTD c RB A R S2 )c s in 2019-n0 SL-CVCASSAR itsgene,.ph ighb nin oV.SP uses using N p:heptad rep TM,t rane domain;CP,yto target sites in 2019 pment or n/entry inhibitors The RBDs of SARS-CoV and MERS-CoV contai (HR)1 and 2.Afte in sl to the recentor the S2 subunit change mation by inserting the FP into the host cell membrane and and association bet ween HRI and HR2 to form six ting i into the hos ugh the acid 15.8 n s prote of MERS-CoV tMERS-CoV inte pore for replication in the cell [5].A peptide derived tion suggesting that 2019-nCoV S-RBD o from the HR2 d main of SARS-CoV S protein(SC-1) modified S-RBD of other coronavirus may be applied can interact with HR region in viral developing 2019- vaccines.Of course,the 6.HB of a HR2 domains in viral s protein and thus blocking The recently develoned sars-cov and mers.cov the viral fusion with the host cell [6].Since 2019 neutralizing monoclonal antibodies(mAbs)and nano nCoV S-HR2 identical to that of dies with protective efficacy are specific to the S SARS-CoV ly a tew theprotein ly the RBD 5,8 ected to bea t2019-nCoV h oV S-RE配 tralizin We have recently designed and engineered a pan EKIpeptide,which could ubit MERS-Co S could 唱P ncy is gener [21 Intranasal ntide before or It may take several months or even vears for after viral challenge,EKI peptide can protect human researching and developing neutralizing antibodies DPP4-transgenic mic from MERS-Cov infection against 2019-nCov infection One of the rapid prophylactic tide as inst 2019-nCov infe tion.We have shown that SARS-CoV S-RBD-specific treat infection by 2019-nCoV and other emerging cor- eutralizing mAbs and sera could onaviruses in the future -Cv-L-CoV-Wcontains three functional domains, fusion peptide (FP), and heptad repeat (HR) 1 and 2. After binding of RBD in S1 to the receptor, the S2 subunit changes confor￾mation by inserting the FP into the host cell membrane and association between HR1 and HR2 to form six￾helical bundle (6-HB), resulting in the fusion between viral and cellular membranes. The viral genetic materials enter into the host cell through the fusion pore for replication in the cell [5]. A peptide derived from the HR2 domain of SARS-CoV S protein (SC-1) can interact with HR1 region in viral S protein to form heterologous 6-HB, resulting in the inhibition of homologous 6-HB formation between HR1 and HR2 domains in viral S protein and thus blocking the viral fusion with the host cell [6]. Since 2019- nCoV S-HR2 sequence is 100% identical to that of SARS-CoV, while there are only a few mutations of non-critical amino acids in S-HR1 region, SC-1 peptide is expected to be also effective against 2019-nCoV infection. We have recently designed and engineered a pan￾CoV fusion inhibitor, EK1 peptide, which could inhibit infection of five human coronaviruses, including SARS-CoV and MERS-CoV, and three bat-SL-CoVs [7]. Intranasal application of EK1 peptide before or after viral challenge, EK1 peptide can protect human DPP4-transgenic mice from MERS-CoV infection, suggesting its potential prophylactic and therapeutic effect against 2019-nCoV infection. Once confirmed, we will develop EK1 peptide as a t prophylactic or therapeutic for intranasal application to prevent or treat infection by 2019-nCoV and other emerging cor￾onaviruses in the future. The RBDs of SARS-CoV and MERS-CoV contain multiple conformation-dependent neutralizing epi￾topes that induce more potent neutralizing antibodies and protective efficacy against SARS-CoV and MERS-CoV infections, respectively, than other regions in S protein [5,8,9]. Modification of MERS-CoV S-RBD amino acid residues based on the structure design could improve its protection against MERS-CoV infec￾tion [9], suggesting that 2019-nCoV S-RBD or modified S-RBD of other coronavirus may be applied for developing 2019-nCoV vaccines. Of course, the RBD-containing S and S1 of a coronavirus, e.g. 2019- nCoV, can also be used for vaccine development [8]. The recently developed SARS-CoV and MERS-CoV neutralizing monoclonal antibodies (mAbs) and nano￾bodies with protective efficacy are specific to the S1 subunit of S protein, particularly the RBD [5,8–10]. Therefore, the 2019-nCoV S-RBD is anticipated to be a key target for developing 2019-nCoV neutralizing mAbs. The neutralizing mAbs targeting non-RBD regions, including NTD and S2 of SARS-CoV and/or MERS-CoV S could also be identified [5,8,11,12], although their neutralizing potency is generally lower than that of RBD-specific mAbs. It may take several months or even years for researching and developing neutralizing antibodies against 2019-nCoV infection. One of the rapid approaches is to evaluate the currently available SARS-CoV neutralizing antibodies with cross-neutra￾lizing and protection activity against 2019-nCoV infec￾tion. We have shown that SARS-CoV S-RBD-specific neutralizing mAbs and sera could cross-neutralize bat-SL-CoVs, such as bat-SL-CoV-W1V1 and bat-SL￾Figure 1. Analysis of the functional domains in 2019-nCoV spike protein and its gene. (A) Phylogenetic analysis of S gene of 2019- nCoV (Wuhan-Hu-1), bat-SL-CoVZXC21, bat-SL-CoVZXC45, SARS-CoV and other coronaviruses using Neighbor-Joining method. (B) The representative scheme of functional domains in S protein of 2019-nCoV. SP, signal peptide; NTD, N-terminal domain; RBD, receptor-binding domain; FP, fusion peptide, HR1, heptad repeat 1; HR2, heptad repeat 2; TM, transmembrane domain; CP, cyto￾plasmic domain. (C) The target sites in 2019-nCoV S for development of vaccines, antibodies and fusion/entry inhibitors. 276 S. Jiang et al