Immune responses to human papillomavirus.

The immune system uses innate and adaptive immunity to recognize and combat foreign agents that invade the body, but these methods are sometimes ineffective against human papillomavirus (HPV). HPV has several mechanisms for avoiding the immune system. HPV infects, and multiplies in keratinocytes, which are distant from immune centers and have a naturally short lifespan. The naturally short life cycle of the keratinocyte circumvents the need for the virus to destroy the cell, which would trigger inflammation and immune response. In addition, HPV downregulates the expression of interferon genes. Despite viral immune evasion, the immune system effectively repels most HPV infections, and is associated with strong localized cell mediated immune responses. New prophylactic L1 virus-like protein vaccines for HPV 16 and 18 and HPV 6, 11, 16, and 18 are in phase 3 trials. Available data suggests that these vaccines are safe, produce high levels of antibodies, and are effective at preventing HPV infection.