Different spectra of therapeutic vaccine development against HPV infections

Human papillomaviruses (HPVs) are simple, non-enveloped, double-stranded DNA viruses and responsible for an enormous global burden of genital disease. HPV is annually associated with 500,000 new cases of cervical cancer and 250,000 cervical cancer deaths worldwide. The association between HPV infection and cervical cancer indicates that HPV serves as an ideal target for development of preventive and therapeutic vaccines. A novel approach for primary prevention of cervical cancer has become available by the discovery of efficient prophylactic HPV vaccines based on virus-like particles. Therapeutic vaccination has been limited by inadequate antigen-specific immune responses. Different therapeutic strategies have been developed including peptide immunization-based therapies, DNA vector-based therapies, viral/bacterial vector-based therapies, immune response modifiers, photodynamic therapy (PDT) and T cell receptor based therapy. At present, the design of therapeutic vaccines to control the growth of HPV-induced tumors has focused on utilization of E6 and E7 proteins or peptides as vaccine antigens. Human trials are the most important test for the efficacy of HPV16/18 E6 and E7 proteins as immunotherapy for cervical cancer. This review attempts to describe different therapeutic vaccinations against HPV infections.