Biology Reference
In-Depth Information
displayed on the surface of capsids,
33
is involved in the early step of
HPV infection by binding with the cellular receptor at the time of
attachment of virions to cells.
L2 functions in the infectious process were also studied by com-
bination of L2s of HPV16 and BPV1 by Yang
et al
.
34
The peptide
with aa sequences of BPV1 aa1-88 binds to the surface of a variety of
cells. The binding, which is not abolished by pretreatment of the cells
with trypsin and heparinase, is interfered with by peptides of BPV1
L2 aa1-88 and HPV16 L2 aa13-31. HPV16 L2 aa13-31 peptide
tagged with GFP (L2/13-31/GFP) attaches to HeLa cells (Fig. 3,
Region A). Amino acid substitutions at aa18 plus aa19 and aa21 plus
aa22 significantly reduce the ability of L2/13-31/GFP to bind to
SiHa cells. Introduction of the same mutation into L2 reduces the
infectivity of HPV16 pseudovirions. Deletion of the region of
aa91-128 from BPV1 L2 eliminates infectivity of BPV1.
These studies indicate that interaction between L2 and the cell
surface at a post-adsorption step would be important for HPV
infection. The N-terminal segments of L2 aa13-31, aa25-45, and
aa108-120 — which are displayed on the surface of capsids — may
be involved in the early step of HPV infection by binding with the
cellular molecules. The cellular target for the segment of aa25-45 is
b-actin, but the cellular targets for aa13-31 and aa108-120 have not
yet been identified.
Antigenicity of HPV Capsid Proteins
Conformationally Dependent and Linear
Epitopes of L1-Capsids
The majority of anti-L1-capsid antibodies recognize conformationally
dependent epitopes and bind to L1-capsids in a highly type-specific
manner. Giroglou
et al
.
35
and Rose
et al
.
36
showed that anti-sera
obtained by immunizing rabbits with HPV6, 11, 16, 18, 31, 33, 35,
39, and 45 L1-capsids are strongly reactive in ELISA with only the cog-
nate L1-capsid type used as the immunogen. Similarly, we have showed
that anti-sera obtained by immunizing mice with HPV6, 16, 18, and
58 L1-capsids react in ELISA with the cognate L1-capsid type used
