BPV-1 has become the model system, since can get transformation in tissue culture cells. Human Papilloma viruses. These infections are very rare in virgins. Infection is directly correlated with the number of partners a couple has had unprotected sex with. The oral mucosa similarly sensitive to these genital viruses.
Several viruses are exclusively infect the oral mucosa.
Characteristically the papilloma virus can be visualized by electron microscopy . The virus replicates only in squamous epithelial cells undergoing differentiation .It is assumed that the virus is present in plasmid form in the basal cell layer, but does not present its full viral protein complement until differentiation takes place. For this reason virus are only found in the top differentiated layers of the wart. Late viral proteins are only found in the terminally differentiated cells of the wart. This is probably why it is difficult to grow in culture.