Product pipeline: Human Papilloma Virus (pathophysiology)

Human papillomavirus (HPV) is the name of a group of viruses that include more than 100 different strains or types. In most cases an infection with HPV does not cause any clinical symptoms. The most common clinical manifestation of an infection with HPV are warts. The HPV type that causes these kinds of clinical symptoms is non cancerous. Other forms of HPV can be sexually transmitted and may eventually cause serious problems. Particularly HPV 16 may cause a variety of high-grade intraepithelial lesions and cancers such as:

• Cervical intraepithelial neoplasia (CIN) and cervical cancer
• Vulvar intraepithelial neoplasia (VIN) and vulvar cancer
• Vaginal intraepithelial neoplasia (VaIN) and vaginal cancer
• Oropharyngeal cancer and other head and neck cancers
• Anal intraepithelial neoplasia (AIN) and anal cancer
• Penile intraepithelial neoplasia (PIN) and penile cancer

Genital HPV infections are estimated to be the most common sexually transmitted infection in the Western world, with millions of persons becoming newly infected each year. About 10% of the population in the Western world and roughly 20% of the population in the developing countries are infected with HPV. Although the majority of infections cause no symptoms, are self-limiting, and are cleared by a spontaneous immune response without clinical consequences, genital HPV is of public health concern because persistent infection with certain high-risk types can cause cervical cancer in women. Fortunately, cervical cancer is an uncommon consequence of HPV, especially if women are regularly screened for cancer with Papanicolaou (Pap) tests followed by appropriate treatment. HPV 16 and 18, are known to cause up to 75% of cervical cancers.

Human Papilloma Virus (prophylactic and therapeutic vaccination)

Currently, two prophylactic vaccines are available. Several studies have mathematically modeled the impact of prophylactic vaccination on the incidence and prevalence of cervical cancer and CIN. These studies indicate that the effect of vaccination depends on a large number of variables, such as efficacy of the vaccine, age at vaccination, percentage of vaccinated women, combination of screening and vaccination, period of vaccine-induced protection, possible inclusion of a boost, etc. Nonetheless, combined, the studies conclude that the incidence and prevalence of CIN and cervical cancer will ultimately decrease by 45-75%.

Importantly, however, a major impact of vaccination is not expected to become visible until approximately 20 years after the first large (at least 70% vaccine coverage) groups of young girls have been vaccinated. In addition, such a high coverage in this age group is unlikely to be achieved in the short term. The impact of vaccination at age 18 is calculated to be significantly less. Meanwhile, there is still no treatment to prevent HPV infection from progressing to cancerous stages. Patients suffering from those stages could be treated with therapeutic HPV vaccines, once available.