Type-specificity of HPV-reactive antibodies. A) Infection of human 293TT cells with HPV16 and HPV33 pseudovirions in the presence of type-specific neutralizing antibodies. Infectious events unaffected by HPV16-specific (mAb H16.56E) or HPV33-specific (mAbs H33.B6, H33.J3) monoclonal antibodies were monitored 72 hrs post infection. B) Interaction of type-specific antibodies with HPV16 and HPV33 virus-like particles (VLPs) in a Heparin-BSA ELISA assay. All three antibodies displayed type-specificity. Although background binding of mAb H33.E12 is significantly increased, specific binding is also restricted to particles of HPV type 33.