What is detected by an HPV test, based on antibodies against viral capsid proteins?
Some HPV tests are based on the detection of viral capsid antigens. Usually viral replication occurs in differentiated keratinocytes. Under the influence of viral proteins, the host cell provides all the components needed for assembly of new infectious particles. So the viral capsid proteins are expressed in differentiating epithelial cells. In HPV-related carcinogenesis normal cellular processes such as differentiation are greatly disturbed, and as transformation proceeds, proper viral propagation is prevented. Therefore expression of viral capsid proteins in high-grade lesions and in invasive cervical carcinomas is rarely detected even though genetic material of HPV can be found. Detection of the viral capsid proteins is more a characteristic of an acute HPV infection, versus p16INK4a over-expression being a marker of a transforming HPV infection.
