Human papilloma virus
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The presentation covers all major aspects of the virus including oncogenicity, Structure, Pathogenesis. It also covers preventive measures and vaccines. This presentation is targeted to students at bachelors level for allied/optional microbiology paper
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Human papilloma virus
- 1. Human papilloma virus Human papillomavirus is the most common sexually transmitted infection. Most sexually active men and women being exposed to the virus at some point during their lifetime
- 2. Structure • small, non-enveloped, icosahedral DNA viruses that have a diameter of 52–55 nm. • single double-stranded DNA molecule of about 8000 base-pairs (bp) that is bound to cellular histones • a protein capsid composed of 72 pentameric capsomers. • capsid contains two structural proteins — late 1 and Late 2 — which are both virally encoded.
- 3. Classification • the International Committee on the Taxonomy of Viruses (ICTV) as two separate families — Papillomaviridae and Polyomaviridae. • HPV is divided into High risk HPV and Low risk HPV. Low- risk types cause warts and high-risk types can cause lesions or cancer.
- 4. Pathogenesis • HPV infection is limited to the basal cells of stratified epithelium • The virus cannot bind to live tissue • it infects epithelial tissues through micro-abrasions or other epithelial trauma that exposes segments of the basement membrane • HPV virion associates with receptors such as alpha integrins, laminins, and annexin A2
- 5. Pathogenesis How HPV causes Cancer? • Early proteins (E): E6/E7 proteins inactivate two tumor suppressor proteins, p53 (inactivated by E6) and Retinoblastoma (inactivated by E7) • E7 acts as the primary transforming protein. E7 competes for retinoblastoma protein binding, freeing the transcription factor E2F to transactivate its targets, thus pushing the cell cycle forward. • E6 in association with host E6-associated protein, which has ubiquitin ligase activity, acts to ubiquitinate p53, leading to its proteosomal degradation
- 6. Pathogenesis How HPV causes Cancer?
- 7. Symptoms • HPV may not cause symptoms at once, but they can appear years later. Some types can lead to warts, while others can cause cancer. Warts • Common symptoms of some types of HPV are warts, especially genital warts. • Genital warts may appear as a small bump, cluster of bumps, or stem-like protrusions. They commonly affect the vulva in women, or possibly the cervix, and the penis or scrotum in men. They may also appear around the anus and in the groin. • They can range in size and appearance and be large, small, flat, or cauliflower shaped, and may be white or flesh tone. • HPV6 and HPV11 are common causes of genital warts and laryngeal papillomatosis.
- 8. Symptoms Other warts associated with HPV include common warts, plantar, and flat warts. • Common warts - rough, raised bumps most commonly found on the hands, fingers, and elbows. • Plantar warts - described as hard, grainy growths on the feet; they most commonly appear on the heels or balls of the feet. • Flat warts - generally affect children, adolescents, and young adults; they appear as flat-topped, slightly raised lesions that are darker than normal skin color and are most commonly found on the face, neck, or areas that have been scratched.
- 9. Symptoms
- 10. Symptoms • Anogenital warts • Anal dysplasia (lesions) : pre cancerous condition in anal canal • Genital cancers • Epidermodysplasia verruciformis (Treeman syndrome, a high risk skin cancer) • Focal epithelial hyperplasia (benign neoplamic condition in mouth) • Mouth papillomas (benign epithelial tumor) • Oropharyngeal cancer • Laryngeal papillomatosis (aerodigestive benign cancer)
- 11. Symptoms Cancer • Other types of HPV can increase the risk of developing cancer. These cancers include cancer of the cervix, vulva, vagina, penis, anus, and oropharynx, or the base of the tongue and tonsils. It may take years or decades for cancer to develop. • early all cervical cancer is due to HPV with two types, HPV16 and HPV18, accounting for 70% of cases • These cancers in common involve sexually transmitted infection of HPV to the stratified epithelial tissue. • Individuals infected with both HPV and HIV have an increased risk of developing cervical or anal cancer.
- 12. Symptoms: Cervical Cancer As in many cancers, there may be no signs or symptoms of cervical cancer until it has progressed to a dangerous stage. However, if symptoms do occur they may include: • Abnormal vaginal bleeding • Pain in very advanced stages • Any bleeding from the vagina other than during menstruation. • Abnormal vaginal discharge
- 13. Transmission • HPV is transmitted through intimate skin-to-skin contact. • having vaginal, anal, or oral sex with someone who has the virus. • It is most commonly spread during vaginal or anal sex. • common that nearly all men and women get it at some point in their lives. • can be passed even when an infected person has no signs or symptoms. • can develop symptoms years after being infected, making it hard to know when you first became infected. In most cases, HPV goes away on its own and does not cause any health problems. But when HPV does not go away, it can cause health problems like genital warts and cancer.
- 14. Diagnosis The traditional methods of viral diagnosis such as electron microscopy, cell culture, and certain immunological methods are not suitable for HPV detection. HPV cannot be cultured in cell cultures. The important methods to diagnose HPV infection are: • Colposcopy and acetic acid test • Biopsy • DNA test (PCR, Southern Blot Hybridization, In Situ Hybridization) • Pap smear
- 15. Diagnosis Colposcopy: a procedure that allows illuminated stereoscopic and magnified viewing of the cervix. PCR-based methods: HPV DNA can be amplified selectively by a series of reactions that lead to an exponential and reproducible increase in viral sequences present in the biological specimen. serological assays: ELISA or western blot analysis
- 16. Diagnosis Biopsy: If the biopsy results show pre-cancer (dysplasia) or cancer, then treatment is recommended. The dysplasia may be mild, moderate, or severe. PAP smear or PAP test: It is a screening test. Apart from premalignant and malignant changes, viral infections like HPV infection and Herpes can also be detected. Acetic acid Test: A vinegar solution applied to HPV-infected genital areas turns them white. This may help in identifying difficult-to-see flat lesions.
- 17. Diagnosis: PAP smear test • Early precancerous changes detected on the Pap smear • A woman may have cervical cancer and not know it because she may not have any symptoms. • A Pap smear is usually part of a pelvic exam and accompanied by a breast exam • A sample of mucus and cells will be obtained from the cervix and endocervix using a wooden scraper or a small cervical brush or broom. • the sample is rinsed into a vial and sent to a lab for slide preparation and examination.
- 18. Treatment There is currently no specific treatment for HPV infection. However warts can be treated. • Salicylic acid. Over-the-counter treatments that contain salicylic acid work by removing layers of a wart a little at a time. • Imiquimod (Aldara, Zyclara). This prescription cream might enhance your immune system's ability to fight HPV. Common side effects include redness and swelling at the application site. • Podofilox (Condylox). Another topical prescription, podofilox works by destroying genital wart tissue. Podofilox may cause pain and itching where it's applied. • Trichloroacetic acid. This chemical treatment burns off warts on the palms, soles and genitals. It might cause local irritation.
- 19. Treatment Surgical and other procedures If medications don't work the following methods can e use to remove warts • Freezing with liquid nitrogen (cryotherapy) • Burning with an electrical current (electrocautery) • Surgical removal • Laser surgery "condom use may reduce the risk for genital human papillomavirus (HPV) infection"
- 20. Vaccination Three vaccines are available to prevent infection by some HPV types. All protect against initial infection with HPV types 16 and 18, which cause most of the HPV-associated cancer cases. Gardasil: protects against HPV types 6 and 11, which cause 90% of genital warts. quadrivalent vaccine Cervarix: bivalent, and is prepared from virus-like particles (VLP) of the L1 capsid protein. Gardasil 9: nonavalent, it has the potential to prevent about 90% of cervical, vulvar, vaginal, and anal cancers.
- 21. Prevention • Vaccination • Avoid skin-to-skin contact by not having sex with strangers. • Use condoms and/or dental dams every time you have vaginal, anal, or oral sex. • Though condoms and dental dams are not as effective against HPV as they are against other STDs like chlamydia and HIV, safer sex can lower your chances of getting HPV.