Development of Novel Single-Chain Antibodies against the Hydrophobic HPV-16 E5 Protein

The human papilloma virus type 16 infects genital mucosa with high prevalence in the oncogenesis of cervical and oropharyngeal cancers. The E5 protein of this virus is a small hydrophobic protein, whose expression generally decreases as the infection progresses to malignancy. These characteristics point to a role of E5 in the establishment of HPV infection and the initiation into cell transformation. The study of the HPV-16 E5 functions has been hindered because of the lack of antibodies. Detection is very difficult because of its hydrophobic nature, membrane location, and very low levels of expression. Thus, the objective of this study was to select single-chain antibodies against the full size E5 protein, which was coexpressed with maltose-binding protein. We report that the E5 protein was recognized by the antibody and was validated in W12 cells by fluorescent microscopy, including a colocalization with one of its host substrates. The use of this antibody could increase our knowledge about the functions of the oncogenic HPV-16 E5 protein during the earliest stages of keratinocyte infection in human.