Smid encoding 12-510 S1 fragment of SARSCoV Urbani Spike (S) protein, with an N terminal C5 signal sequence and a C-terminal human IgG Fc [14], was used as a template in site directed mutagenesis PCR using QuikChange Lightning Site-Directed Mutagenesis Kit (Stratagene) to generate Sin845, GZ-C, GDO1, and GZ0402 mutants. The same procedure and primers were used for the generation of the full length S protein 1113-59-3 Mutant constructs using the pcDNA3.1- S, coding 18325633 for the full length SARS-CoV S 
protein with a C-terminal (C9) tag derived from human rhodopsin protein, as a template.well as mutant proteins (Sin845, GZ-C, GD01 and GZ0402) overnight at 4uC. The binding of the 18 HmAbs were tested by ELISA as described previously using antihuman IgG2 HRP mouse monoclonal antibody as the secondary antibody (SouthernBiotech, Birmingham, AL) [19]. The same procedure was followed for testing the binding of 39 non S1 neutralizing HmAbs against S protein ectodomain, S2, HR1, HR2 and S1 domain proteins.Production of Urbani and Different Mutant Pseudotyped VirusesPseudotyped viruses were generated by co-transfection of 293FT producer cells (grown in DMEM with 10 FBS) with pHIV-GFP-luc expression vector, pgagpol HIV vector, pHIV-Rev and pHIV-TAT [31], along with the pcDNA3.1-S coding for the SARS-CoV S protein using calcium phosphate transfection according to the previously described protocol [19]. For the production of HIV/DE, only HIV vectors were transfected into the cells. The media were changed the following morning and the supernatants were collected 24 and 48 hrs later and pooled. The pseudotyped viruses were concentrated through a 20 sucrose cushion at 41,000 rpm using Beckman Ultracentrifuge. The incorporation of the S proteins in the virus particles was confirmed by western blot using 1D4 anti-rhodopsin mouse monoclonal antibody (Santa Cruz Biotechnology, Santa Cruz, CA), while the virus p24Ag content was confirmed by mouse anti-HIV1 p24 monoclonal antibody (Santa Cruz Biotechnology, Santa Cruz, CA).Construction of S-ectodomain, S2, HR1 and HR2 Domains Expression PlasmidsThe pcDNA3.1 S encoding the full length S protein of SARSCoV was used as a template in a PCR reaction to amplify the Sectodomain (residues 12-1184), the S2 (residues 700-1184), the HR1 (residues 901-1040), and the HR2 (residues 1141-1184) domains. All the K162 web forward primers were designed with a 59 NheI site while the reverse primers were designed with a 59 BamHI site. The PCR products were then cloned in frame into the C-terminus IgG tag mammalian expression vector [14].In vitro Pseudotyped Virus Neutralization AssayEntry inhibition was performed by 
pre-incubating Urbani and mutant pseudoviruses, [equivalent to 10 nanograms of p24 Ag, quantified by HIV-1 p24 ELISA kit (Express Biotech International, MD)], with purified mAbs individually or in combinations at 37uC for 1 hr. The pseudovirus/mAb mixture or pseudovirus alone was added to the target 293/ACE2 stable cell line plated at a density of 60,000 cells/well in 12 well plate, and incubated overnight at 37uC and the medium was replaced the following morning. Forty eight hours later, the cells were lysed and luciferase expression was determined using luciferase assay kit (Promega, WI) according to the manufacturer’s instructions. The rabbit immune serum was used as a positive control for entry inhibition. The percentage entry inhibition was calculated using the following equation: Luciferase reading of mock treated virus{Expression and.Smid encoding 12-510 S1 fragment of SARSCoV Urbani Spike (S) protein, with an N terminal C5 signal sequence and a C-terminal human IgG Fc [14], was used as a template in site directed mutagenesis PCR using QuikChange Lightning Site-Directed Mutagenesis Kit (Stratagene) to generate Sin845, GZ-C, GDO1, and GZ0402 mutants. The same procedure and primers were used for the generation of the full length S protein mutant constructs using the pcDNA3.1- S, coding 18325633 for the full length SARS-CoV S protein with a C-terminal (C9) tag derived from human rhodopsin protein, as a template.well as mutant proteins (Sin845, GZ-C, GD01 and GZ0402) overnight at 4uC. The binding of the 18 HmAbs were tested by ELISA as described previously using antihuman IgG2 HRP mouse monoclonal antibody as the secondary antibody (SouthernBiotech, Birmingham, AL) [19]. The same procedure was followed for testing the binding of 39 non S1 neutralizing HmAbs against S protein ectodomain, S2, HR1, HR2 and S1 domain proteins.Production of Urbani and Different Mutant Pseudotyped VirusesPseudotyped viruses were generated by co-transfection of 293FT producer cells (grown in DMEM with 10 FBS) with pHIV-GFP-luc expression vector, pgagpol HIV vector, pHIV-Rev and pHIV-TAT [31], along with the pcDNA3.1-S coding for the SARS-CoV S protein using calcium phosphate transfection according to the previously described protocol [19]. For the production of HIV/DE, only HIV vectors were transfected into the cells. The media were changed the following morning and the supernatants were collected 24 and 48 hrs later and pooled. The pseudotyped viruses were concentrated through a 20 sucrose cushion at 41,000 rpm using Beckman Ultracentrifuge. The incorporation of the S proteins in the virus particles was confirmed by western blot using 1D4 anti-rhodopsin mouse monoclonal antibody (Santa Cruz Biotechnology, Santa Cruz, CA), while the virus p24Ag content was confirmed by mouse anti-HIV1 p24 monoclonal antibody (Santa Cruz Biotechnology, Santa Cruz, CA).Construction of S-ectodomain, S2, HR1 and HR2 Domains Expression PlasmidsThe pcDNA3.1 S encoding the full length S protein of SARSCoV was used as a template in a PCR reaction to amplify the Sectodomain (residues 12-1184), the S2 (residues 700-1184), the HR1 (residues 901-1040), and the HR2 (residues 1141-1184) domains. All the forward primers were designed with a 59 NheI site while the reverse primers were designed with a 59 BamHI site. The PCR products were then cloned in frame into the C-terminus IgG tag mammalian expression vector [14].In vitro Pseudotyped Virus Neutralization AssayEntry inhibition was performed by pre-incubating Urbani and mutant pseudoviruses, [equivalent to 10 nanograms of p24 Ag, quantified by HIV-1 p24 ELISA kit (Express Biotech International, MD)], with purified mAbs individually or in combinations at 37uC for 1 hr. The pseudovirus/mAb mixture or pseudovirus alone was added to the target 293/ACE2 stable cell line plated at a density of 60,000 cells/well in 12 well plate, and incubated overnight at 37uC and the medium was replaced the following morning. Forty eight hours later, the cells were lysed and luciferase expression was determined using luciferase assay kit (Promega, WI) according to the manufacturer’s instructions. The rabbit immune serum was used as a positive control for entry inhibition. The percentage entry inhibition was calculated using the following equation: Luciferase reading of mock treated virus{Expression and.
