Human papilloma virus

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"human papillomavirus"[MeSH Terms] AND (vaccine OR cervical cancer OR carcinogenesis)

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HPV vaccine cervical cancer prevention

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human papillomavirus HPV pathogenesis types oncogenesis vaccine overview 2024

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https://pmc.ncbi.nlm.nih.gov/articles/PMC11277246

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Human Papillomavirus (HPV)

Overview

Human papillomavirus is a small, non-enveloped, double-stranded DNA virus belonging to the family Papillomaviridae. It is the most common sexually transmitted infection worldwide, with over 200 identified genotypes. Not all types cause the same disease - the clinical outcome depends heavily on the tropism (skin vs. mucosa) and oncogenic potential of the specific type.

Classification

By Oncogenic Risk

Risk Category	HPV Types	Associated Diseases
High-risk (HR)	16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68, 73, 82	Cervical, anal, oropharyngeal, vulvar, penile carcinomas
Low-risk (LR)	6, 11, 40, 42, 44, 54, 55, 61, 62, 71, 74, 81, 84, 89, 90	Condylomata acuminata (genital warts), recurrent respiratory papillomatosis
Cutaneous	1, 2, 3, 7, 10, 27, 57, 73	Common warts, plantar warts, flat warts
EV-associated	5, 8, 9, 10, 14, 17, 20-25, 37, 38	Epidermodysplasia verruciformis (risk of skin SCC)

HPV 16 and 18 alone account for approximately 70% of all cervical cancers. HPV 6 and 11 cause ~90% of genital warts and virtually all cases of recurrent respiratory papillomatosis.

Genome Structure and Key Proteins

The HPV genome (~8 kb circular dsDNA) is divided into three regions:

Long Control Region (LCR) - non-coding regulatory region controlling transcription and replication
Early genes (E1, E2, E4, E5, E6, E7) - expressed early in infection; regulate replication and oncogenesis
Late genes (L1, L2) - encode the major (L1) and minor (L2) capsid proteins

Oncoproteins - the Key Cancer Drivers

E6 - binds and promotes ubiquitin-mediated degradation of p53 (the "guardian of the genome"), blocking apoptosis and allowing DNA damage to accumulate
E7 - binds and inactivates pRb (retinoblastoma protein), releasing transcription factor E2F and pushing cells into uncontrolled S-phase entry
E5 - enhances EGFR signaling, promotes immune evasion
E1 / E2 - regulate viral DNA replication; loss of E2 (via chromosomal integration) removes the brake on E6/E7 transcription, a critical step toward malignancy

The most conserved genes across HPV types are E1, E2, and L2. The oncoproteins E5-E7 show the highest variability, which partly explains differences in oncogenic potential between types.

Pathogenesis and Oncogenesis

Steps to Infection

HPV enters through microabrasions in stratified squamous epithelium (skin/mucosa)
Infects basal keratinocytes (the only dividing cells in the epithelium)
Viral genome maintained as episome (extrachromosomal); E1/E2 regulate replication
As cells differentiate and migrate upward, late genes (L1, L2) are expressed and virions assembled in superficial layers
Viral shedding occurs from superficial cells

From Infection to Cancer

Most HPV infections (>90%) are cleared by the immune system within 1-2 years. Persistent infection with high-risk types - especially in the setting of co-factors - drives malignant transformation:

Viral integration into host chromosomes disrupts E2, upregulating E6 and E7
E6 degrades p53 → loss of apoptosis and cell cycle arrest
E7 inactivates Rb → uncontrolled cell proliferation
Genomic instability accumulates → CIN (Cervical Intraepithelial Neoplasia) progression: CIN I → CIN II → CIN III → invasive carcinoma

Co-factors that accelerate progression: tobacco use, immunosuppression (HIV, transplant), high parity, long-term OCP use, folate deficiency, UV radiation (for cutaneous types), co-infection with other STIs.

Transformation Zone

In the cervix, the squamocolumnar junction (the "transformation zone") is the site where columnar cells undergo squamous metaplasia and are most vulnerable to HPV infection and neoplastic change.

Clinical Manifestations

Anogenital Disease

Condylomata acuminata (genital warts) - soft, flesh-colored, cauliflower-like papules; caused by HPV 6 and 11; highly contagious; rarely malignant
Cervical cancer - usually squamous cell carcinoma; HPV 16, 18 predominate; preceded by CIN
Vulvar/vaginal intraepithelial neoplasia (VIN/VaIN) - HPV 16 major type
Anal/rectal carcinoma - high incidence in MSM with HIV; HPV 16, 18
Penile carcinoma - HPV 16, 18 involved in ~40-50% of cases
Bowenoid papulosis - pigmented papules with carcinoma-in-situ histology; HPV 16, 18

Non-Genital Cutaneous Disease

Disease	Types
Common warts (verruca vulgaris)	1, 2, 4, 27
Plantar warts (verruca plantaris)	1, 2, 4, 57
Flat warts (verruca plana)	3, 10, 27, 28
Butcher's warts	1-4, 7, 10, 28
Epidermodysplasia verruciformis	5, 8 (malignant potential)

Oropharyngeal / Head & Neck Disease

Recurrent respiratory papillomatosis (RRP) - laryngeal/tracheal papillomas from HPV 6, 11; can be life-threatening; juvenile form acquired perinatally
Oropharyngeal SCC (tonsil, base of tongue) - HPV 16; incidence rising sharply in developed countries; better prognosis than HPV-negative HNSCC
Oral leukoplakia, oral carcinoma - HPV 16, 18

Diagnosis

Cytology (Pap smear) - screening for cervical precancer; koilocytes (perinuclear halo, nuclear atypia) are the hallmark HPV-infected cells
HPV DNA testing (co-test) - detects high-risk HPV types; used alone (primary screening) or with Pap smear
Colposcopy + biopsy - for abnormal cytology/HPV results; biopsy for histological grading
p16/Ki-67 immunostaining - surrogate marker for high-risk HPV transcriptional activity; used in histopathology and cytology triage
Genotyping - identifies specific types (e.g., HPV 16/18 separately)

Vaccines (Prophylactic)

Three vaccines have been developed; all are based on virus-like particles (VLPs) made from recombinant L1 capsid protein - they are non-infectious and highly immunogenic.

Vaccine	Types Covered	Trade Name
Bivalent	16, 18	Cervarix (no longer sold in the US)
Quadrivalent	6, 11, 16, 18	Gardasil
9-valent	6, 11, 16, 18, 31, 33, 45, 52, 58	Gardasil-9 (current standard)

Efficacy

Efficacy against CIN, VIN, and PIN caused by covered types: >90% (approaching 100% in HPV-naive recipients)
Efficacy against genital warts (Gardasil/Gardasil-9): 89-98%
HPV infections for vaccine-covered types decreased >80% among US women aged 14-24 between 2003-2006 and 2015-2018
Scottish national data (2024) showed zero invasive cervical cancers among 448,000 women vaccinated at ages 12-13
Anal cancers/precancers decreased ~70% in young women vaccinated before age 17 (Denmark 2024)
Cervical cancer rates fell 69% among US women aged 20-24 between 2013-2021

A 2025 Cochrane network meta-analysis (PMID: 41276263) confirmed vaccination for prevention of cervical cancer and HPV-related diseases across vaccine types.

Vaccination Schedule (US - CDC 2024)

Ages 9-14: 2-dose series (0, 6-12 months)
Ages 15-26: 3-dose series (0, 1-2, 6 months)
Ages 27-45: Shared clinical decision-making (less benefit due to likely prior exposure)
Recommended for all genders
Best given before sexual debut (no therapeutic effect on existing infection)

Treatment

There is no antiviral treatment that eliminates HPV itself. Management is directed at HPV-induced lesions:

Genital Warts

Patient-applied: Imiquimod (5%), podophyllotox (0.5%), sinecatechins (15% ointment)
Provider-applied: Trichloroacetic acid (TCA), cryotherapy, surgical excision, laser
High recurrence rates (~30-70%) due to latent virus in surrounding tissue

Cervical Precancer (CIN)

CIN I: Observation (most regress spontaneously)
CIN II/III: LEEP (loop electrosurgical excision procedure), cold knife conization, cryotherapy
Post-treatment HPV vaccination may reduce recurrence (PMID: 40919695 - 2025 Cochrane review on HPV vaccination after conisation)

Invasive Cervical Cancer

Surgery (radical hysterectomy), radiotherapy, cisplatin-based chemotherapy depending on stage
Pembrolizumab (anti-PD-1) now approved for recurrent/metastatic cervical cancer with PD-L1 expression

Recurrent Respiratory Papillomatosis

Serial surgical debulking (CO2 laser, microdebrider); adjuvant intralesional cidofovir or bevacizumab in refractory cases; no cure

Therapeutic Vaccines (Investigational)

Multiple therapeutic vaccines targeting E6/E7 oncoproteins are in clinical trials - including DNA, mRNA, peptide, and viral vector platforms. None are yet approved.

Epidemiology

~340 million prevalent HPV infections worldwide at any time
Cervical cancer: ~660,000 new cases and ~350,000 deaths annually (global; predominantly in low- and middle-income countries with limited screening access)
HPV is responsible for virtually 100% of cervical cancers, ~90% of anal cancers, ~70% of oropharyngeal cancers, ~40-50% of penile/vulvar cancers
Oropharyngeal HPV-related cancers are increasing in high-income countries despite declining cervical cancer rates

Key Points Summary

HPV is a DNA virus with >200 types; high-risk types (especially 16, 18) drive most HPV-related cancers via E6 (degrades p53) and E7 (inactivates Rb)
Most infections are cleared; persistent infection plus co-factors leads to neoplasia
9-valent vaccine (Gardasil-9) is the current standard, with near-100% efficacy in HPV-naive individuals
Screening (Pap + HPV co-test) and vaccination together are the pillars of cervical cancer prevention
No antiviral exists; treatment targets lesions (excision, ablation, topical agents)

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