Mechanism of Uncoating of Influenza B Virus in MDCK Cells: Action of Chloroquine

Abstract

SUMMARYExposure of influenza B virus-infected MDCK cells to chloroquine at the time of infection resulted in significant inhibition of infection. The appearance of input virus in the intracellular vesicles was not affected in the presence of the drug, but primary transcription of the virus genome did not occur. Chloroquine caused a rapid rise in the pH inside the lysosomes of MDCK ceils, to 6.5 from the physiological pH 5.6. In contrast, exposure of infected cells incubated in acidic medium (pH 6.0) to chloroquine did not cause an increase in lysosomal pH and this low pH treatment during the chloroquine-sensitive phase was followed by virus production. Influenza B virus induced haemolysis of chick erythrocytes at low pH values (5-0 to 5.9) which was associated with cell--cell membrane fusion. It is likely that chloroquine prevents the uncoating of influenza B virus by increasing the lysosomal pH above the critical value required for inducing fusion between the virus envelope and the lysosomal membrane.

Influenza A Virus Nucleoprotein: A Highly Conserved Multi-Functional Viral Protein as a Hot Antiviral Drug Target

“…This double protonated species cannot readily penetrate the endosomal membrane. As a result, the endosomal pH increases [95], which impedes the conformational change of hemagglutinin for viral uncoating. Overall chloroquine acts as a proton sponge and neutralizes the endosomal pH.…”

Recycling of chloroquine and its hydroxyl analogue to face bacterial, fungal and viral infections in the 21st century

“…Thus, in this mechanism the antiviral effect is dependent on the extent to which the virus uses endosomes for entry [59]. For instance, Shibata et al [35] found that CQ might prevent the uncoating of influenza B virus by increasing the lysosomal pH above the critical value required for inducing fusion between the virus envelope and the lysosomal membrane. CQ was also found to inhibit uncoating of the hepatitis A virus (HAV) [42].…”

“…The activity of CQ against Orthomyxoviridae (influenza A and B viruses) has been described for several decades [35,37,122] and in vitro assays on avian influenza virus strains are ongoing [36]. Shibata et al's [35] results suggested that CQ prevents the uncoating of influenza B virus. Ooi et al [38] found that the IC 50 values of CQ against influenza A viruses H1N1 and H3N2 were 3.6 mol/L and 0.84 mol/L, respectively.…”

Influenza virus inhibits amiloride-sensitive Na+channels in respiratory epithelia

“…1d) suggested that it was a consequence of one of the early steps in the infection process (26). These early steps include: (i) the binding of hemagglutinin in the viral coat to sialic acid residues on a receptor protein in the apical membrane, which can be inhibited by pretreatment with neuraminidase (27); (ii) the endocytosis of the virusreceptor complex, which can be blocked by cytochalasin D (28); and (iii) the uncoating of the virus because of the movement of H ϩ through the M2 protein in the viral coat, which can be blocked by amantadine (29,30) or by chloroquine, which dissipates the endosomal pH gradient (31). Of the four agents that block one or the other of these early steps in the infection process, only neuraminidase prevented the inhibition of the amiloride-sensitive current by PR8 virus (Fig.…”