HPV، Human papilloma virus
Date: 2 سال قبل
Clinical manifestations include benign papillomatous lesions of skin and mucous membranes (common warts, plantar warts, flat warts, anogenital warts, epidermodysplasia verruciformis, and laryngeal papillomas). Cervical intraepithelial neoplasia and cervical cancer are associated with human papillomavirus infection.
Papillomaviruses are similar to polyomaviruses, except that the particles are 55 nm in diameter, the DNA is 8 kbp in size, and the genome structure is more complex. All viral genes are encoded on one strand of DNA.
Classification and Antigenic Types
Classification is based on the structure of the viral particle. Reagents are not available for serotyping; human papillomavirus types are distinguished by DNA hybridization assays or DNA sequence analysis. There are more than 70 human types.
Replication is dependent on the differentiated state of epithelial cells. Viral DNA remains latent (not integrated) in basal cells of benign lesions. Replication occurs in differentiating cells. Capsid proteins and viral particles are found only in terminally differentiated epidermal cells. Viral DNA is integrated in cancer cells, which contain no replicating virus.
Different human papillomavirus types cause specific lesions. The pathogenic mechanisms are not well understood. A few specific types, notably human papillomavirus types 16 and 18, are associated with the development of premalignant and malignant genital lesions. Cofactors are required for cancer development.
The roles of humoral and cell-mediated immune responses in disease pathogenesis or prevention are not known. Warts tend to regress spontaneously.
Papillomaviruses are widely distributed. Transmission occurs by contact. Genital warts are sexually transmitted. Laryngeal papillomas may be due to human papillomavirus acquired during birth from a mother with genital warts. Prevalence data are incomplete, and there are no serologic assays to distinguish the different types.
Clinically, nucleic acid hybridization may be used to detect viral DNA in tissue samples. Serologic methods need to be developed to identify specific human papillomavirus types.
Instruments should be sterilized after examination of patients with human papillomavirus infections. The public should be educated about this disease to prevent sexual transmission. Most warts regress spontaneously. Available treatments include local destructive methods and application of caustic agents. Interferons are effective against laryngeal papillomas, common warts, and anogenital warts.