Role of L2 cysteines in papillomavirus infection and neutralization

Table 1 Assembly, infectivity and RG-1 antibody reactivity of pseudovirions carrying mutant L2

Mutation within HPV16 L2	Infectivity of mutant HPV16 pseudovirion relative to w.t. L2	Co-assembly of L2 and encapsidation as for w.t.	RG-1 Mab Binding (WB)	% Binding of polyclonal 17-36 antiserum (ELISA)
Δ17 - 30	>0.1%	Yes	No	-
Δ23 - 36	>0.1%	Yes	No	-
Δ353 - 362	100%	Yes	Yes	-
Δ393 - 403	100%	Yes	Yes	-
Y19A	100%	Yes	Yes	-
K20A	100%	Yes	No	100%
C22A	>0.1%	Yes	No	84%
C22S	>0.1%	Yes	No	96%
K23A	100%	Yes	Yes	-
Q24A	100%	Yes	Yes	-
C28A	>0.1%	Yes	No	74%
C28S	>0.1%	Yes	No	72%
P29A	100%	Yes	Weak	100%
C22/28S	>0.1%	Yes	-	120%
L1 alone	>0.1%	-	-	-

HPV16 pseudovirions were prepared using expression vectors for SEAP, HPV16 L1 and wild type L2 or the L2 deletion mutants or point mutants indicated. The preparations were treated with benzonase to remove unencapsidated DNA, and virions purified on an optiprep gradient. The purified virions were examined for L1 by Western blot (WB) with MAb885 antibody, or for L2 with RG-1 antibody or a full length HPV16L2-specific polyclonal antibody, or for encapsidated DNA by agarose gel-electrophoresis after extraction. The infectivity of 2-fold serially diluted pseudovirions was examined by measuring SEAP activity of 293TT cells three days after treatment with different volumes of the pseudovirion preparations. Rabbit polyclonal antiserum to HPV16 L2 17-36 peptide was tested for binding to HPV16 pseudovirions containing mutant L2 versus wild type L2 in an ELISA. (-) not done.

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