Viruses: EBOV and clathrin-mediated endocytosis

The Zaire ebolavirus (EBOV) is a negative-sense, single-stranded RNA virus composed of a helical RNA strand bound by several structural and regulatory proteins, including VP35, VP30, nucleoprotein (NP) and protein L, contained within the capsid. VP35 and VP30 are cofactors of protein L, which catalyzes the transcription of viral RNA within the cytosol of the host cell. The capsid is surrounded by an envelope derived from the host cell’s plasma membrane, which is studded with 10 nm spikes of viral glycoprotein (GP). Unlike positive-sense RNA viruses, such as poliovirus, the pure, isolated RNA from EBOV is not inherently infectious, because it must first be transcribed to produce functional viral mRNA. In comparison, the viral genome of poliovirus and other positive-sense pathogens can be immediately translated by the host cell into necessary viral proteins. The structure of EBOV is shown in Figure 1.

Figure 1 Structure of EBOV

Researchers were interested in investigating whether the mechanism of cell entry of EBOV differs from clathrin-mediated endocytosis, which is the mechanism used by many positive-sense RNA viruses like poliovirus. To investigate this, they separated 200 rats into two even groups. They infected group-1 rats with live poliovirus and group-2 rats with live EBOV. For each group, half of the rats were then injected with “drug X”, a drug known to inhibit dynamin. After two weeks, biopsies were taken, and immunohistochemical staining was used to identify the number of infected cells per high-powered microscope field. The results are shown in Figure 2.

Figure 2 Effect of drug X on viral infectivity