The role of scavenger receptor BI in hepatitis - eTheses Repository ...

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Particle density is believed to be determined by lipid composition; lower
density HCV virions have a higher lipid content and therefore may be
regarded as the ‘most lipoprotein like’ form. Low density HCV have the
highest specific infectivity (45, 179, 180) and we have shown that particle
density correlates with sensitivity to neutralising antibodies (Figure 5-8).
Taken together these observations suggest that adopting a lipoprotein like
formation promotes HCV infection, and possibly stabilises the virion
glycoproteins in a manner that reduces epitope availability. A number of
apoprotein species can be found in HCV LVPs, indeed apoC-I is thought to
enhance infection (79, 210, 211), however it is not known how apoproteins
function within an infectious particle. Understanding the role of apoproteins
within circulating HCV particles will be key to determining the relationship
between particle density and infectivity.
Figure 6-2 displays a model structure of a HCV LVP; this particle has both
virion and lipoprotein like characteristics. The envelope proteins lie flat within
the membrane surrounding the capsid, however the outer leaflet of the virion
envelope is fused with the lipoprotein lipid monolayer. This proposed structure
would confine the viral glycoproteins to the virion envelope bilayer, whereas
the very large structural apoprotein, apo-B100, resides within the triglyceride
core of lipoprotein (321) and should not diffuse into the virion. However, the
smaller exchangeable apoproteins reside within the lipoprotein lipid monolayer
(321), allowing their diffusion throughout the particle and interaction with viral
glycoproteins. The areas of the viral envelope proteins shaded in green