FIG 4.

IFITM3/Y20A-enhanced SARSpp and MERSpp infection is low pH dependent. (A) Huh7.5 cells were infected with OC43pp, MERSpp, SARSpp, NL63pp, or 229Epp in the absence (mock) or presence of the indicated concentrations of NH₄Cl. Luciferase activities were determined at 48 hpi. Relative infection is the ratio of the luciferase activity in cells treated with NH₄Cl over that in the mock-treated cells. The error bars indicate standard deviations (n = 6). (B and C) Huh7.5 cells stably expressing the indicated wild-type or Y20A mutant IFITM3 proteins or transduced with the empty vector were infected with MERSpp (B) or SARSpp (C) in the absence (mock) or presence of the indicated concentrations of NH₄Cl. Luciferase activities were determined at 48 hpi. Relative infection is the ratio of the luciferase activity in cells treated with NH₄Cl over that in the mock-treated cells. The error bars indicate standard deviations (n = 6).