Human Papillomavirus Infections¶
Chapter 203 | Part 5: Infectious Diseases
KEY CLINICAL POINTS¶
- HPV is a nonenveloped, double-stranded DNA virus causing cervical, anal, vulvar, vaginal, and oropharyngeal cancers.
- 9-valent HPV vaccine (Gardasil-9) prevents 90% of cervical cancers and 96.7% of cancers from oncogenic HPV types 31, 33, 45, 52, 58.
- HPV transmission occurs via sexual contact, with ~50% of young women infected within months of first intercourse.
- Immunosuppression (e.g., HIV) accelerates HPV-related disease progression and increases cancer risk.
- Cervical cancer screening guidelines recommend Pap smears every 3 years for women 21–65, with HPV co-testing for women ≥ 30.
1. DEFINITION & OVERVIEW¶
Human papillomavirus (HPV) is an icosahedral, nonenveloped, 8000-base-pair, double-stranded DNA virus with a 55 nm diameter. It infects basal keratinocytes of specific anatomic tissues after microtrauma. Over 200 HPV types exist, with 40 regularly identified in the anogenital tract. Types 6/11 cause low-risk lesions (genital warts), while 16/18 are high-risk for cervical cancer.
HPV Types and Cancer Risk¶
| HPV Type | Cancer Risk | Clinical Manifestations |
|---|---|---|
| 6/11 | Low-risk | Genital warts, low-grade cervical lesions |
| 16/18 | High-risk | Cervical, anal, vulvar, vaginal, oropharyngeal cancers |
| 31/33/45/52/58 | High-risk | Cervical cancer, anal cancer |
1.1 Viral Structure¶
HPV is a nonenveloped, double-stranded DNA virus with an icosahedral capsid. The L1 protein self-assembles into virus-like particles (VLPs) that mimic virions but lack genetic material.
1.2 Host Range¶
Infects basal keratinocytes of specific anatomic tissues (e.g., genital epithelium, oral mucosa). Transmission occurs via direct contact with infected genital skin/mucosa or secretions.
2. EPIDEMIOLOGY¶
HPV is the most common sexually transmitted infection globally. Seroprevalence of HPV types 16/18 peaks at 80% by age 6 in Europe. In developing countries, cervical cancer accounts for ~10% of female cancer deaths. HIV-infected individuals have 5–10x higher risk of cervical cancer. Anal cancer incidence is 130/100,000 in HIV+ MSM vs 5/100,000 in HIV- MSM.
2.1 Global Burden¶
Over 600,000 women diagnosed with cervical cancer annually; 300,000 die. 85% of cases occur in low-income countries. HPV-associated oropharyngeal cancers (OPSCC) have increased 200% in the U.S. since 1973.
2.2 Risk Factors¶
Early sexual debut, multiple partners, smoking, immunosuppression (HIV), poor nutrition, chlamydial infection. HIV-infected individuals have 5–10x higher risk of cervical cancer.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
HPV infects basal keratinocytes, replicates during differentiation, and is transmitted via sexual contact. E6/E7 proteins inactivate p53/Rb tumor suppressors, leading to malignant transformation. Persistent infection is the most significant risk factor for cervical cancer. HPV types 16/18 cause ~70% of cervical squamous cell carcinomas and 85% of cervical adenocarcinomas.
3.1 Viral Oncogenesis¶
E6 protein binds p53 for degradation; E7 protein inactivates Rb, allowing uncontrolled cell proliferation. These proteins disrupt cell cycle regulation and promote genomic instability.
3.2 Immune Evasion¶
HPV lacks viremic phase, leading to incomplete antibody response. Immunosuppression (e.g., HIV) increases viral persistence and cancer risk. T cell responses to E2/E6 proteins correlate with cervical cancer prevention.
4. CLINICAL FEATURES¶
Symptoms include genital warts (types 6/11), cervical dysplasia, and cancer. In men, symptoms may include penile warts, anal lesions, or oropharyngeal masses. Cervical cancer presents with abnormal bleeding, pelvic pain, or mass. HPV-associated oropharyngeal cancers present with sore throat, ear pain, or neck masses.
4.1 Cutaneous Manifestations¶
Genital warts (types 6/11): soft, sessile growths with smooth/rough surface. Perianal warts: papillary proliferations with vascular loops. Vulvar warts: whitish papules with finger-like projections.
4.2 Malignant Lesions¶
Cervical cancer: exophytic mass, ulcerated lesions, or cervical canal masses. Anal cancer: rectal bleeding, anal mass, or fistulas. Oropharyngeal cancer: tonsillar/lingual masses, dysphagia.
5. DIFFERENTIAL DIAGNOSIS¶
Genital warts: HSV, syphilis, molluscum contagiosum. Cervical dysplasia: atrophic cervicitis, chlamydial infection. Anal cancer: squamous cell carcinoma vs basal cell carcinoma. Oropharyngeal cancer: laryngeal cancer, lymphoma.
5.1 Non-HPV Causes¶
Herpes simplex virus (HSV), syphilis, molluscum contagiosum, chlamydial infection, squamous cell carcinoma, lymphoma.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis via PCR for HPV DNA in cervical/vaginal swabs, anal swabs, or oral rinse. HPV typing (types 6/11/16/18) identifies low/high-risk infections. Cytology (Pap smear) detects cervical dysplasia. Colposcopy with acetic acid (VIA) for cervical cancer screening in resource-limited settings.
HPV Testing and Screening Guidelines¶
| Population | Recommended Test | Frequency |
|---|---|---|
| Women 21–29 | Pap smear | Every 3 years |
| Women 30–65 | Pap smear or HPV co-testing | Every 3 years or 5 years |
| HIV+ women | Pap smear | Annual within 1 year of HIV diagnosis |
6.1 Diagnostic Tests¶
PCR for HPV DNA, HPV typing (types 6/11/16/18), Pap smear, colposcopy, HPV DNA co-testing (women ≥ 30), anal Pap smear.
6.2 Screening Guidelines¶
Women 21–29: Pap smear every 3 years. Women 30–65: Pap smear every 3 years or HPV co-testing every 5 years. HIV+ women: annual Pap smear within 1 year of HIV diagnosis.
7. MANAGEMENT & TREATMENT¶
Treatment focuses on lesion removal, immunomodulation, and prevention. Options include imiquimod cream, interferon, cryotherapy, electrocautery, laser therapy, and surgical excision. Vaccination (9-valent vaccine) prevents 90% of cervical cancers and 96.7% of cancers from oncogenic HPV types.
7.1 Therapeutic Options¶
Imiquimod (5% cream): 3x/week for 16 weeks. Interferon α (1.0×10 I IU/lesion): 3x/week for 3 weeks. Cryotherapy: liquid nitrogen for 2–3 sessions. Laser therapy: for exophytic lesions. Surgical excision: for large lesions.
7.2 Vaccination¶
9-valent vaccine (Gardasil-9): prevents 90% of cervical cancers and 96.7% of cancers from oncogenic HPV types 31/33/45/52/58. Recommended for 9–45-year-olds. Efficacy 94.9% against CIN 2/3, 91.7% against CIN 3, 100% against AIS.
8. PROGNOSIS & COMPLICATIONS¶
Persistent HPV infection is the most significant risk factor for cervical cancer. Cervical cancer peaks in 5th–6th decade in developed countries, 10–15 years earlier in resource-poor countries. HPV-associated oropharyngeal cancers have 5-year survival ~50–60%. HIV-infected individuals have 5–10x higher risk of cervical cancer and 130/100,000 anal cancer incidence vs 5/100,000 in HIV- MSM.
8.1 Cancer Outcomes¶
Cervical cancer 5-year survival: 90% for stage I, 50–60% for stage III, 15–20% for stage IV. Oropharyngeal cancer 5-year survival: ~50–60%. Anal cancer 5-year survival: 70–80% for localized, 10–20% for distant.
9. SPECIAL CONSIDERATIONS¶
HPV vaccination is safe in HIV-infected individuals, with higher antibody responses in those with high CD4 counts. Pregnancy: imiquimod not recommended; cryotherapy/LEEP may be used for cervical dysplasia. HIV-infected women require annual Pap smears. HPV-associated oropharyngeal cancers are increasing in men, especially white males 40–50 years old.
9.1 HIV Considerations¶
HIV accelerates HPV-related disease progression. HIV+ individuals have 5–10x higher cervical cancer risk. HPV vaccination recommended for HIV+ 11–26-year-olds. Anal cancer incidence 130/100,000 in HIV+ MSM vs 5/100,000 in HIV- MSM.
9.2 Pregnancy¶
Imiquimod not recommended during pregnancy. Cryotherapy/LEEP may be used for cervical dysplasia. HPV-associated warts may resolve postpartum. No evidence of vertical transmission.
10. KEY POINTS & CLINICAL PEARLS¶
- HPV is the most common STI and causes ~90% of cervical cancers. 2. 9-valent vaccine prevents 90% of cervical cancers and 96.7% of cancers from oncogenic HPV types. 3. HIV-infected individuals have 5–10x higher cervical cancer risk. 4. Cervical cancer screening: Pap smear every 3 years for women 21–65. 5. HPV-associated oropharyngeal cancers are increasing in men, especially white males 40–50 years old. 6. Imiquimod is effective for genital warts but not for cervical/vaginal/anal lesions.