Inhibition of Semliki Forest Virus Penetration by Lysosomotropic Weak Bases

Abstract

SUMMARYThe effect of five lysosomotropic weak bases (chloroquine, amantadine, tributylamine, methylamine and NH4CI) on Semliki Forest virus (SFV) infection has been studied in BHK-21 cells. When present at concentrations equal to or greater than 0-1, 0.5, 2, 15 and 15 mM respectively, the agents inhibited SFV infection by more than 90%. The effect was reversible and involved a process occurring within the first 60 min of virus-cell contact. The agents did not have a direct virucidal effect nor did they affect virus binding to the cells, receptor-mediated endocytosis of prebound virus, intracellular distribution of virus after endocytosis, or the low pH-induced membrane fusion activity of the virus spike glycoproteins. The step blocked by chloroquine and NH4CI occurred intracellularly and was identified as the release of the virus nucleocapsid into the cytoplasm or the uncoating process. On the basis of these results, our previous studies on SFV entry, and the known effects of lipophilic amines on lysosomes, we conclude that the agents affect entry by a common mechanism: they prevent the transfer of the virus nucleocapsid into the cytoplasm by increasing the lysosomal pH above the critical value needed to trigger a low pH-dependent fusion reaction between the membranes of the tysosome and the virus.

MHC Class I Presentation of Live and Heat‐Inactivated Sendai Virus Antigen in T2Kb Cells Depends on an Intracellular Compartment with Endosomal Characteristics

“…It should be pointed out that the PR8 CTL data thus reflect drug inhibition of virus infectivity rather than an effect on antigen processing. The complete, or strong, inhibition of PR8 virus infection of EL-4 cells show an effect, at some level, on endosomal activity as this virus is taken up by endocytosis and requires a low pH to penetrate the vesicular membrane into the cytosol [32]. We also verified that the different drugs did not affect CTL effector activity per se (data not shown).…”

Stepwise dismantling of adenovirus 2 during entry into cells

“…Neither drug had significant effect on the efficiency of virus binding and endocytosis. Since ammonium chloride raises the endosomalllysosomal pH within 1 min after addition (Okhuma and Poole, 1978) it could be used to define the time course of virus penetration from endosomes (Helenius et al, 1982). Adenoviruses were bound to cells at 4OC, and ammonium chloride was added at different times before and after warming to 37%.…”

Pathway of rubella virus infectious entry into Vero cells

“…By preventing the low pH-induced fusion of viral and cell membranes which occurs in the endosome, these compounds are able to block the entry of certain viruses into the cytosol (Gollins & Porterfield, 1986;Helenius et al, 1982;Matlin et al, 1981Matlin et al, , 1982. In a first series of experiments, medium containing different concentrations of four lysosomotropic drugs (monensin, methylamine, ammonium chloride and chloroquine) were added to Vero cells after the viral binding step (1 h at 4 °C) and maintained for the complete virus replication cycle (48 h).…”