The Membrane Fusion Step of Vaccinia Virus Entry Is Cooperatively Mediated by Multiple Viral Proteins and Host Cell Components
Figure 5
Effects of deficiencies of individual virion membrane proteins on membrane fusion and virus infectivity.
In each panel, equivalent numbers of purified R18-loaded MVs were bound to HeLa cells at 4°C for 60 min and unbound virions were removed by washing. Virus-bound cells were then incubated at 37°C for 40 min and R18 fluorescence was monitored and plotted as arbitrary units. Parallel cultures were incubated for 48 h and the yield of virus was determined by plaque assay. Recombinant viruses were as follows: (A) ΔI5L, (B) IPTG-inducible A16, (C) IPTG-inducible G9, (D) IPTG-inducible G3, (E) IPTG-inducible A21, (F) IPTG-inducible O3, (G) IPTG-inducible H2, (H) IPTG-inducible F9, (I) IPTG-inducible A28, (J) IPTG-inducible L1, and (K) IPTG-inducible L5. For panels B-K, the plus and minus signs in the upper left signifies the virus was grown in the presence or absence of IPTG, respectively. For panel A, the plus and minus refer to wild type virus and a deletion mutant, respectively. As a negative control, 56°C heat-inactivated I5+ virions (panel A) were assayed for hemifusion and infectivity (<105 PFU/ml; data not shown).