The envelope proteins of hepatitis C virus (HCV) are the likely targets of
neutralizing antibodies and their molecular and functional characterization
is relevant for vaccine development. We previously showed that surface-exp
ressed E2 is a better immunogen than intracellular E2 and, therefore, we we
re interested in exploring more efficient ways to present E2 protein on the
cell surface. We found that E2 targeted to the cell surface by replacement
of its transmembrane domain did not bring El to the surface although El co
uld be expressed independently on the cell surface if its transmembrane dom
ain was similarly replaced. FAGS analysis suggested that E2 expressed on th
e cell surface acquired its native conformation more efficiently when trunc
ated at aa 661 than when truncated at aa 715. The shorter form of truncated
E2 better retained the ability to bind the second extracellular loop (EC2)
of CD81, the putative HCV receptor. Interestingly, deletion of the hyperva
riable region 1 (HVR1) did not perceptibly alter E2 structure; cell-surface
forms of E2 lacking the HVR1 remained reactive with conformation-sensitive
MAbs and were able to bind recombinant EC2 of CD81, (C) 2000 Academic Pres
s.