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as the immunogen.
37
The mouse antisera show low levels of cross-
reactivity in ELISA using alkaline-denatured L1-capsids as the antigen.
HPV16 L1-capsids have conformationally dependent and linear
epitopes. Christensen
et al
.
38
characterized a panel of anti-HPV16 L1
mouse monoclonal antibodies (MAbs) in detail. Fourteen MAbs were
prepared by immunizing mice with HPV16 L1-capsids and examined
for their reactivity with L1-capsids of HPV16, 6, 11, 18, 31, 33, 35,
and 45. Three MAbs (H16.E70, H16.U4, and H16.V5) react with
intact HPV16 L1-capsids in ELISA exclusively, indicating that type-
specific conformationally dependent epitopes are displayed on the
surface of the capsids. One MAb (H16.H5) reacts with both intact
and denatured HPV16 L1-capsids and three MAbs (H16.C2,
H16.L4, and H16.O7) react with denatured HPV16 L1-capsid,
indicating that type-specific linear epitopes are either at the surface
or buried within. One MAb (H16.P2) is weakly reactive to a shared
conformationally dependent epitope present on L1-capsids of
HPV16, 31, and 35. The other MAbs (H16.B20, H16.D9, H16.F18,
H16.I23, H16.J4, and H16.S1) have various levels of cross-reactivity
with the denatured L1-capsids of various HPVs.
Neutralization with Anti-L1 Antibodies in vitro
Giroglou
et al
.
35
showed that antisera obtained by immunizing rabbits
with L1-capsids of HPV6, 11, 16, 18, 31, 33. 35, 39, and 45 neutralize
the infectivity of pseudovirions in a type-specific manner, as predicted
from the type-specific binding of antibodies against HPV L1-capsids.
Roden
et al
.
39
examined the neutralizing activity of the MAbs
against HPV16 pseudovirions having BPV1 genome. After incuba-
tion with each MAb ascites sample to be tested, approximately 100
focus-forming units of pseudovirus were inoculated to mouse C127
cell monolayers, and the number of foci formed three weeks later was
scored. Three type-specific and conformationally dependent MAbs
(H16.E70, H16.U4, and H16.V5) inhibit focus formation with the
pseudovirions, indicating that these MAbs have neutralizing activi-
ties
in vitro
. H16.D9, H16.H5, H16.J4, H16.L4, H16.O7 and
H16.S1 do not neutralize the pseudovirions. H16.E70 and H16.V5
