To test E protein folding and expression, 1610 6 WT and mutant E expressing cells were seeded in 10 cm plates, cultured for 24h, and then E protein expression was induced by culture for 36 h in 1.5 mg/ml tetracycline in DME medium with 10% FCS at 37uC. Cells were lysed in RIPA buffer (50 mM Tris-HCl pH 7.4, 150mM NaCl, 1% NP40, 0.5% Na-deoxycholate, 0.1% SDS, 1mM PMSF, 16 Roche complete protease inhibitor cocktail) on ice for 1 hr. The cell lysates were cleared by centrifugation for 30 min at 10,0006g and protein concentrations were quantitated and normalized. E proteins were immunoprecipitated from cell lysate samples (500 mg total cellular protein) using 20 mg purified mAb 4G2 or mAb 4E11 and 20 ml protein-G sepharose, or 30 ml Sango antibody and 20 ml protein-A sepharose. 4E11 and 4G2 immunoprecipitated samples were blotted with Sango. Sango immunoprecipitated samples were blotted with mouse anti DENV2 serum.