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Fig. 2.
Surrogate systems to examine infection mechanisms of HCV. There
are three systems for the study of infection mechanisms of HCV at the
moment. First is a binding assay. Purified envelope protein, HCV-LPs or HCV
particles were used as probes to determine the binding receptors. However,
this binding assay cannot analyze further steps of infection such as fusion and
penetration. Second is a fusion assay. Cell lines expressing HCV envelope pro-
teins and T7 RNA polymerase were co-cultured with the target cell lines con-
taining a reporter plasmid. Upon membrane fusion, T7 RNA polymerase
activates the reporter gene. Third is a pseudotype system. Pseudotype viruses
based on VSV or retroviruses possessing HCV E1 and E2 proteins can inves-
tigate the mechanism of the penetration step by envelope proteins of HCV.
HCV-LPs for HCV-cell Interaction
In the absence of purified HCV particles, virus-like particles (VLPs)
have shown to be one of the surrogate models for HCV studies. It has
been shown that recombinant expression of the major structural pro-
teins of various viruses leads to the formation of VLPs. Production of
VLPs has mostly succeeded by using a recombinant baculovirus
expression system. Several viruses are demonstrated the application of
