Human Papillomavirus Flashcards
Classification
Family: Papillomaviridae
Genus:
16 genera
Humans are affected by:
HPV 1 - 4
HPV 6, 11, 16, 18, 31 and 33
Characteristics
Naked virus
Icosahedral nucleocapsid
Circular dsDNA
No virion polymerase
There are at least 60 types, which are determined by DNA sequence not by antigenicity
- Many types infect the epithelium and cause papillomas at specific body sites
Transmission
- direct contact of skin or genital lesions
- sexual contact (most common)
Pathogenesis
Virus makes E6 and E7 proteins
E6 causes proteolysis of p53
E7 causes proteolysis of RB (retinoblastoma protein)
p53: cell cycle checkpoints at G1S phase (stops transition from G1 to S)
RB: tumour suppressor
Infected cells grows without inhibition —> leads to neoplasia (cervical cancer)
Risk factors:
- immunocompromised
- AIDs patient’s
- Smoking
- Use of oral contraceptives
Diseases
Papillomas
HPV 1 - 4 : cutaneous common warts = Verruca vulgaris
HPV 6 and 11 :
Laryngeal papilomatosis
(Mainly common in children > acquired at birth)
Condyloma acuminata = anogenital warts
(Acquired via sexual contact)
HPV 16 and 18 : anogenital squamous cell carcinoma
> > > 70% cases «<
HPV 31 and 33 : also anogenital carcinoma
[suspicion of cervical cancer: if a patient complains of “post-coital bleeding (bleeding after sex)
Microbiological diagnosis
- Pap smear —> screening for cervical cancer
> diagnosis is made clinically by finding koilocytes (large nuclei cells, that might be binucleated) - DNA hybridisation tests
Treatment and prevention
- Podophyllin or liquid nitrogen are most commonly used
- treatment varies according to the site of lesions:
Liquid nitrogen is used for skin lesions
Podophyllin for genital lesions
Salicylic acid for plantar lesions
Alpha interferon is also available
Prevention:
- Guardasil: HPV 6, 11, 16, 18 inactivated subunit vaccine
