Papillomaviruses are very widely spread, they infect not only humans but also other mammals as well as birds and reptiles. There are over 100 different Human Papillomavirus(HPV) types. HPVs are very common viruses that are usually transmitted through sexual contact. HPVs can be divided into two groups, based on their ability to induce tumors: high-risk and low-risk. The most common cancer caused by Human Papillomaviruses is cervical cancer with 530 000 new cases each year. Although extensivly studied for few decades, not enough is still known about how these viruses persist in human epithelia long enough to cause severe problems.
Papillomaviruses infect basal epithelia and its life cycle is tightly connected to the differentiation of keratinocytes. All known papillomaviruses share almost identical viral genome which is circular dsDNA and it contains three regions:
- Early region which encodes regulatory proteins
- Late region which encodes capsid proteins
- Upstram-regulatory region - URR