Biology Reference
In-Depth Information
inhibit hemagglutination mediated by HPV L1-capsids or L1/L2-
capsids, indicating that the MAbs prevented HPV pseudovirions
from binding to the cell surface. H16.U4 recognizes an epitope in
a functional domain not required for the binding (the role of the
domain is not clear at present). Leucine residue at aa50 and serine
residue at aa282 constitute part of the epitope for H16.V5 and
H16.E70, respectively
39-41
(Fig. 1).
Wang
et al
.
42
showed that H16.V5 is capable of blocking the sero-
logical reactivity of the majority of human sera reactive to HPV16
L1/L2-capsids. ELISA plates coated with HPV16 L1/L2-capsids
received an excess amount of each anti-HPV16 MAb, and then received
human sera positive for anti-HPV16 antibodies. The pretreatment with
H16.V5 prevents the majority of human sera from binding to the cap-
sid antigen, suggesting that most human antibodies reactive with
HPV capsids recognize the same or closely related major antigenic
determinant(s) for H16.V5. The human sera that were not blocked
by H16.V5 are mostly derived from the women with HPV16-associ-
ated cervical lesions.
Roden
et al
.
28
indicated that four anti-BPV1-L1 MAbs, which
were produced by immunizing mice with purified BPV virions, inhibit
the infection of mouse C127 cells with BPV1. These MAbs recognize
type-specific conformationally dependent epitopes on the BPV1 L1-
capsid. Three MAbs effectively block the binding of the virus to the cell
surface at a ratio of approximately two MAb molecules per L1 molecule.
One MAb does not block the binding effectively; however, it efficiently
neutralizes BPV1 infectivity at 0.1 MAb molecule per L1 molecule.
Thus, anti-L1 antibodies can prevent papillomavirus infection
in
vitro
by at least two steps: at the binding to the cell surface and at a
currently unidentified subsequent step in the infection pathway.
Protective Immunity with Anti-L1 Antibodies
in Animal Models
Consistent with the neutralization studies
in vitro
, Breiburd
et al
.
43
showed that antibodies recognizing conformationally dependent
epitopes in L1 are required for protecting rabbits against challenge
