Were assembled by co-transfection of 293 T cells with Env plasmid containing JRFL Env WT gene or its loop deletion or ITI 007 biological activity replacement mutants with or without the CT, and HIV-1 backbone plasmid pNL4-3 containing a luciferase reporter gene and HIV-1 structural genes. 48 h post transfection, the culture supernatants containing assembled pseudovirus were harvested and stored at 280uC, or directly used in virus titration by capture ELISA and subsequent virus entry assay.Construction of Loop Deletion MutantsFull-length JRFL gp160 gene in pSVIII was used as a template for generation of various loop deletion or replacement mutants, including single loop deletion of V2 (DV2), V3 (DV3), V4 (DV4), V5 (DV5), loop D (DlpD), CD4 binding loop (DCD4bl), and deletion of V2 crown (DV2C) and V3 crown (DV3C), and double loop deletion of V1 and V2 (DV1V2), and loop D and V5 (DlpDDV5), and replacement of V4 (DV4fl) and V5 (DV5fl) with flexible linkers of the same lengths (Table 1). A panel of primers were designed and synthesized for amplification of different fragments of JRFL gp160 gene and for replacement of each loop with either a short flexible linker or a flexible linker of the same length as the original loop (in the case of V4 and V5) (Table 1 and 2). Primer pSV3for was paired with each anti-sense primer to amplify the upstream fragments of the Env, and primer pSV3rev was paired with each sense primer for amplification of the corresponding downstream fragments using the following PCR program: an initial denaturation at 94uC for 5 min, followed by 10 Licochalcone-A cycles of 95uC for 20 s, 50uC for 30 s and 72uC for 90 s, and 20 cycles of 95uC for 20 s, 55uC for 30 s and 72uC for 90 s, and a final extension at 72uC for 10 min. The upstream and the corresponding downstream fragments for each mutant were assembled by splice overlap extension (SOE) as follow: an initial denaturation at 94uC for 5 min, followed by 5 cycles of 95uC for 20 s, 55uC for 30 s and 72uC for 90 s. The assembled full-length gp160 loop deletion mutant genes were then amplified by PCR using pSV3for and pSV3rev as a pair of primers and the following PCR program: 20 cycles of 95uC for 20 s, 55uC for 30 s and 72uC for 3 min, and a final extension at 72uC for 10 min. All PCR products were gel-purified using QIAquick gel extraction kit (Qiagen), digested with KpnI and BamHI, and ligated to pSV3 plasmid digested with the same restriction enzymes. Ligation products were used to transform TG1 electroporation competent cells. Each loop deletion or replacement mutant was confirmed by DNA sequencing.Pseudovirus Entry AssayCrude preparation of pseudovirus in culture supernatant was 3fold serially diluted in DMEM growth medium and 100 ml of each dilution in triplicate were placed in 96-well flat-bottom cell culture plates. 100 ml of TZM-bl cell suspension in DMEM growth medium containing DEAE-Dextran (25 mg/ml) were dispensed to the wells to a final cell density of 10,000 cells per well and a final concentration of DEAE-Dextran of 10 mg/ml. The plates were then incubated at 37uC with 5 CO2 for 48 h. Cells were washed with PBS once and lysed with 60 ml per well lysis buffer by incubating at RT for 30 min followed by addition of 25 ml of luciferin (Promega). Luminescence readings (RU) were determined by PE Victor3 luminometer. Relative pseudovirus entered into the cells was calculated as follow: (RUsample-RUblank)/(RUWT-RUblank)6100.Capture ELISA250 ng per well of D7324 in PBS were coated on high-binding 96-well h.Were assembled by co-transfection of 293 T cells with Env plasmid containing JRFL Env WT gene or its loop deletion or replacement mutants with or without the CT, and HIV-1 backbone plasmid pNL4-3 containing a luciferase reporter gene and HIV-1 structural genes. 48 h post transfection, the culture supernatants containing assembled pseudovirus were harvested and stored at 280uC, or directly used in virus titration by capture ELISA and subsequent virus entry assay.Construction of Loop Deletion MutantsFull-length JRFL gp160 gene in pSVIII was used as a template for generation of various loop deletion or replacement mutants, including single loop deletion of V2 (DV2), V3 (DV3), V4 (DV4), V5 (DV5), loop D (DlpD), CD4 binding loop (DCD4bl), and deletion of V2 crown (DV2C) and V3 crown (DV3C), and double loop deletion of V1 and V2 (DV1V2), and loop D and V5 (DlpDDV5), and replacement of V4 (DV4fl) and V5 (DV5fl) with flexible linkers of the same lengths (Table 1). A panel of primers were designed and synthesized for amplification of different fragments of JRFL gp160 gene and for replacement of each loop with either a short flexible linker or a flexible linker of the same length as the original loop (in the case of V4 and V5) (Table 1 and 2). Primer pSV3for was paired with each anti-sense primer to amplify the upstream fragments of the Env, and primer pSV3rev was paired with each sense primer for amplification of the corresponding downstream fragments using the following PCR program: an initial denaturation at 94uC for 5 min, followed by 10 cycles of 95uC for 20 s, 50uC for 30 s and 72uC for 90 s, and 20 cycles of 95uC for 20 s, 55uC for 30 s and 72uC for 90 s, and a final extension at 72uC for 10 min. The upstream and the corresponding downstream fragments for each mutant were assembled by splice overlap extension (SOE) as follow: an initial denaturation at 94uC for 5 min, followed by 5 cycles of 95uC for 20 s, 55uC for 30 s and 72uC for 90 s. The assembled full-length gp160 loop deletion mutant genes were then amplified by PCR using pSV3for and pSV3rev as a pair of primers and the following PCR program: 20 cycles of 95uC for 20 s, 55uC for 30 s and 72uC for 3 min, and a final extension at 72uC for 10 min. All PCR products were gel-purified using QIAquick gel extraction kit (Qiagen), digested with KpnI and BamHI, and ligated to pSV3 plasmid digested with the same restriction enzymes. Ligation products were used to transform TG1 electroporation competent cells. Each loop deletion or replacement mutant was confirmed by DNA sequencing.Pseudovirus Entry AssayCrude preparation of pseudovirus in culture supernatant was 3fold serially diluted in DMEM growth medium and 100 ml of each dilution in triplicate were placed in 96-well flat-bottom cell culture plates. 100 ml of TZM-bl cell suspension in DMEM growth medium containing DEAE-Dextran (25 mg/ml) were dispensed to the wells to a final cell density of 10,000 cells per well and a final concentration of DEAE-Dextran of 10 mg/ml. The plates were then incubated at 37uC with 5 CO2 for 48 h. Cells were washed with PBS once and lysed with 60 ml per well lysis buffer by incubating at RT for 30 min followed by addition of 25 ml of luciferin (Promega). Luminescence readings (RU) were determined by PE Victor3 luminometer. Relative pseudovirus entered into the cells was calculated as follow: (RUsample-RUblank)/(RUWT-RUblank)6100.Capture ELISA250 ng per well of D7324 in PBS were coated on high-binding 96-well h.
