Human papillomavirus (HPV) - MegaMicro

Go to content

Main menu:

Human papillomavirus (HPV)

Microbiology > Virology > DNA viruses
• A member of the Family Papillomaviridae, HPV is a small, nonenveloped virus with an icosahedral capsid containing a double-stranded DNA circular genome.
• HPV infects only humans, with over 200 genotypes identified, including 40 genotypes that preferentially infect the anogenital mucosa.

• The most common sexually transmitted disease worldwide, with approximately 14 million new infections  reported each year in the USA.
• HPV is present in nearly 100% of all cervical cancers, with HPV-16 and HPV-18 in 70% of them.  HPV-6 and HPV-11 are low risk genotypes for cervical cancer, but may cause condyloma acuminatum (anogenital warts), oral and laryngeal papillomas.
• 10% of women infected with high risk HPV genotypes will develop precancerous lesions.
• Transmission is by direct contact: (1) through small breaks in the skin or mucous membranes, (2) sexual intercourse, (3) while an infant is passing through an infected birth canal.  Asymptomatic shedding may promote transmission.

• The replication of the virus is integrally linked to epithelial cell differentiation.  The virus infects the basal stem cell via specific cellular receptors.  Upon desquamation of this short-lived cell, new virions are released for the next round of infection.
• The risk for persistence and progression to cancer varies by HPV genotype and host factors,  many which are poorly understood.

Disease manifestations:
• Most HPV infections are transient and asymptomatic.
• Different HPV genotypes have a propensity to infect different body sites and are thus associated with different diseases.
• Clinical syndromes include: skin warts (generally hands and feet), condyloma acuminate (anogenital warts), benign oral, laryngeal or conjunctival papillomas, cervical cancer and other anogenital and oral cancers.

Laboratory Diagnosis:
• PAP smear screening: cytological changes in cervical squamous epithelial cells (koilocytosis) associated with HPV infection.
• Molecular detection of HPV in cervical swabs or oropharyngeal tissue.
• HPV does not grow in culture and serology is only used in research settings.

Differential Diagnosis:

• Warts usually spontaneously regress, but this may take months to years.
• If removal is required, methods such as surgical cryotherapy, electrocautery or chemical means (podophyllin) are used.
• Cancerous lesions may involve surgery, chemotherapy and/or radiation.

Prevention and Control:
• Prevent exposure to infected tissue by safe sexual practices (for example, the use of condoms).
• Vaccination of individuals prior to sexual activity.  Three HPV vaccines are licensed in the USA, however, only the 9-valent vaccine (Gardasil 9, Merck) is being distributed as of 2016.  The vaccine is composed of virus-like particles prepared from recombinant L1 capsid protein prepared from the targeted HPV genotypes.

Related concepts
Papovaviruses, papilloma virus, anogenital warts, cervical cancer, oropharyngeal cancer

Copyright 2016. All rights reserved.
Back to content | Back to main menu