HPV، Human papilloma virus
Date: 2 سال قبل
author: AmirAbad
Papillomavirus
Clinical Manifestations
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.
Structure
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.
Multiplication
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.
Pathogenesis
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.
Host Defenses
The roles of humoral and
cell-mediated immune responses in disease pathogenesis or prevention are not
known. Warts tend to regress spontaneously.
Epidemiology
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.
Diagnosis
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.
Control
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.
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