162
Cytomegalovirus and Varicella–zoster Virus Vaccines
viruses such as VZV and CMV, these
neutralizing antibodies are elicited and
bound by the envelope glycoproteins,
whereas antibody produced to internal
virion proteins such as tegument and
capsid proteins is not protective and is
only useful for conFrming VZV or CMV
infection. Helper T-cell responses are nec-
essary for production of antibody against
protein antigens, so that T-cell responses
to both surface and internal virion pro-
teins can have an indirect role in antibody
production.
The major glycoprotein species for CMV
a
regBandthegH
/gL
/gOhe
te
ro
t
r
ime
r
,
and the major species for VZV are the
gE/gI heterodimer, gB, and the gH/gL/gO
heterotrimer (±ig. 1). CMV and VZV gB
glycoproteins may also exist in oligomeric
forms in their native conformation on the
surface of the virion, either as a dimer or a
tetramer. The characteristics of these viral
gene products are summarized in Table 2.
The
original
electrophoretic
analyses
of
puriFed
CMV
and
VZV
detected
a larger number of electrophoretically
distinct
envelope
glycoproteins,
but
subsequent immunological analyses with
monoclonal
antibodies
demonstrated
that
these
multiple
species
actually
Tab. 2
Characteristics of major immunogenic proteins of CMV and VZV.
Protein (gene)
Viral function
Immunogenicity
CMV gB (UL55)
Most abundant glycoprotein in envelope;
virion fusion and penetration into cell
Principal target of neutralizing
antibody, and target for helper
and cytotoxic T cells
CMV gH (UL75)
Second most abundant glycoprotein in
envelope, oligomer with CMV gL and
gO; fusion
Target of neutralizing antibody
and helper/cytotoxic T cells
CMV pp65 (UL83)
Major component of tegument;
phosphoprotein with protein kinase
activity and role in intracellular
regulation
Principal target for helper and
cytotoxic T cells
CMV pp150 (UL32)
Second most predominant component
of tegument; phosphoprotein
SigniFcant target of helper and
cytotoxic T cells
CMV IE1 (UL123)
Nonstructural protein; immediate-early
protein important in regulation
SigniFcant target for cytotoxic T
cells
VZV gE (OR±68)
Most abundant glycoprotein in envelope;
oligomer with gI
Major target of neutralizing
antibody
VZV gB (OR±31)
Second most abundant envelope
glycoprotein; virion entry and fusion
Target of neutralizing antibody
VZV gH (OR±37)
Glycoprotein component of envelope;
oligomer with VZV gL and gO
Target of neutralizing antibody
VZV IE62 (OR±62)
Major component of tegument;
immediate-early regulatory protein
with role in replication; major altered
gene product in Oka vaccine vs
parental virus strain
Major target of cytotoxic T cells
VZV IE63 (OR±63)
Component of tegument;
immediate-early protein with
regulatory role in intracellular
replication
Major target of cytotoxic T cells
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