Antigenic specificity of immune sera. Analysis of Day 56 antiserum from individual rabbits immunized with HPV-11 L1 NLS- plant protein extract. Sera were tested against equal concentrations of denatured and non-denatured insect cell-derived HPV-11 L1 NLS+ and NLS- VLPs at a concentration of 0.4 μg/well. Error bars represent the standard deviation calculated from triplicate analysis of samples. Insect cell-derived VLPs were denatured at 100°C for 10 min. Rabbits #11 and #12 were immunized with A. thaliana-derived HPV-11 L1 NLS- antigen. Rabbits #13 and #14, #15 and #16, and #17 and #18 were inoculated with N. tabacum-derived protein extract from T1 generation transgenic plant lines X1, Xh and Xi respectively.