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Introduction
1. Anatomy
2. Microbiology
2.1 General bacteriology
2.2 Introduction to systemic bacteriology
2.3 Gram positive cocci
2.4 Gram negative cocci
2.5 Gram positive bacilli
2.6 Gram negative bacilli
2.7 Other important bacteria
2.8 Virology
2.8.1 Overview
2.8.2 Herpesviruses
2.8.3 Poxviruses
2.8.4 Adenovirus
2.8.5 Papilloma and Polyoma viruses
2.8.6 Parvovirus
2.8.7 Orthomyxoviruses and Paramyxoviruses
2.8.8 Viruses causing diarrhea
2.8.9 Picornavirus
2.8.10 Hepatitis Viruses
2.8.11 Arboviruses
2.8.12 Retroviruses
2.8.13 Other important viruses
2.8.14 Additional information
2.9 Parasitology
2.10 Mycology
3. Physiology
4. Pathology
5. Pharmacology
6. Immunology
7. Biochemistry
8. Cell and molecular biology
9. Biostatistics and epidemiology
10. Genetics
11. Behavioral science
Wrapping up
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2.8.5 Papilloma and Polyoma viruses
Achievable USMLE/1
2. Microbiology
2.8. Virology

Papilloma and Polyoma viruses

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They’re in the Papovavirus family. They cause several easily identifiable diseases.

Human papillomavirus (HPV)

HPV is widely known for causing cervical cancer and is the reason behind routine cervical Pap smear screening. The E6 and E7 proteins of HPV are essential for oncogenesis:

  • E6 binds to p53 and targets it for degradation by ubiquitin ligase.
  • E7 binds to the Rb tumor suppressor protein family and interferes with the function of E2F transcription factors.

Infection is thought to occur in cells of the basal layer of stratified epithelia, where viral genomes are established as episomes and replicate synchronously with chromosomal DNA. Transmission occurs through skin-to-skin and genital contact.

Clinical features: HPV types 1, 2, 3, and 4 cause benign warts on the hands and feet. Types 6 and 11 cause laryngeal papillomas and genital warts (condyloma acuminata), which may become malignant. Types 16 and 18 are most commonly associated with cervical cancer, anal cancer, penile cancer, and some cases of oral cancer. HPV 31, 33, and 45 are also associated with cervical cancers. Remember that, histologically, it’s a squamous cell carcinoma.

Laboratory diagnosis of HPV infections: Koilocytes are vacuolated squamous cells that can be seen in lesions. DNA hybridization can also be used to detect viral DNA. E6 and E7 mRNA detection assays have been used recently to predict the risk of developing cervical carcinoma.

Polyoma virus

The important ones are JC and BK viruses. After primary infection, they become latent in immunocompetent individuals. They’ve been loosely associated with oncogenesis and autoimmune disorders.

  • JC virus causes progressive multifocal leukoencephalopathy in AIDS and other immunodeficiencies.
  • BK virus causes hemorrhagic cystitis in bone marrow transplant recipients and transplant nephropathy, which can lead to renal allograft failure.

Diagnosis is made by quantifying polyoma virus DNA in blood, CSF, and urine. Urine can be screened for typical “decoy” cells, which are infected epithelial cells with intranuclear inclusions. These can be detected in urine cytology by Papanicolaou stain or phase contrast microscopy. Brain or renal biopsy specimens show glassy, basophilic intranuclear viral inclusions.

Human papillomavirus (HPV)

  • Causes cervical cancer; routine Pap smear screening
  • E6 protein degrades p53; E7 protein inactivates Rb tumor suppressor
  • Infects basal layer of stratified epithelia; transmitted skin-to-skin, genital contact
  • Clinical types:
    • Types 1, 2, 3, 4: benign warts (hands, feet)
    • Types 6, 11: laryngeal papillomas, genital warts (condyloma acuminata)
    • Types 16, 18, 31, 33, 45: cervical, anal, penile, oral cancers (squamous cell carcinoma)
  • Diagnosis:
    • Koilocytes in lesions
    • DNA hybridization, E6/E7 mRNA assays

Polyoma virus

  • Includes JC and BK viruses; latent after primary infection
  • JC virus: progressive multifocal leukoencephalopathy (AIDS, immunodeficiencies)
  • BK virus: hemorrhagic cystitis (bone marrow transplant), transplant nephropathy (renal allograft failure)
  • Diagnosis:
    • Quantify viral DNA in blood, CSF, urine
    • “Decoy” cells in urine cytology (Papanicolaou stain, phase contrast)
    • Biopsy: glassy, basophilic intranuclear inclusions
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Papilloma and Polyoma viruses

They’re in the Papovavirus family. They cause several easily identifiable diseases.

Human papillomavirus (HPV)

HPV is widely known for causing cervical cancer and is the reason behind routine cervical Pap smear screening. The E6 and E7 proteins of HPV are essential for oncogenesis:

  • E6 binds to p53 and targets it for degradation by ubiquitin ligase.
  • E7 binds to the Rb tumor suppressor protein family and interferes with the function of E2F transcription factors.

Infection is thought to occur in cells of the basal layer of stratified epithelia, where viral genomes are established as episomes and replicate synchronously with chromosomal DNA. Transmission occurs through skin-to-skin and genital contact.

Clinical features: HPV types 1, 2, 3, and 4 cause benign warts on the hands and feet. Types 6 and 11 cause laryngeal papillomas and genital warts (condyloma acuminata), which may become malignant. Types 16 and 18 are most commonly associated with cervical cancer, anal cancer, penile cancer, and some cases of oral cancer. HPV 31, 33, and 45 are also associated with cervical cancers. Remember that, histologically, it’s a squamous cell carcinoma.

Laboratory diagnosis of HPV infections: Koilocytes are vacuolated squamous cells that can be seen in lesions. DNA hybridization can also be used to detect viral DNA. E6 and E7 mRNA detection assays have been used recently to predict the risk of developing cervical carcinoma.

Polyoma virus

The important ones are JC and BK viruses. After primary infection, they become latent in immunocompetent individuals. They’ve been loosely associated with oncogenesis and autoimmune disorders.

  • JC virus causes progressive multifocal leukoencephalopathy in AIDS and other immunodeficiencies.
  • BK virus causes hemorrhagic cystitis in bone marrow transplant recipients and transplant nephropathy, which can lead to renal allograft failure.

Diagnosis is made by quantifying polyoma virus DNA in blood, CSF, and urine. Urine can be screened for typical “decoy” cells, which are infected epithelial cells with intranuclear inclusions. These can be detected in urine cytology by Papanicolaou stain or phase contrast microscopy. Brain or renal biopsy specimens show glassy, basophilic intranuclear viral inclusions.

Key points

Human papillomavirus (HPV)

  • Causes cervical cancer; routine Pap smear screening
  • E6 protein degrades p53; E7 protein inactivates Rb tumor suppressor
  • Infects basal layer of stratified epithelia; transmitted skin-to-skin, genital contact
  • Clinical types:
    • Types 1, 2, 3, 4: benign warts (hands, feet)
    • Types 6, 11: laryngeal papillomas, genital warts (condyloma acuminata)
    • Types 16, 18, 31, 33, 45: cervical, anal, penile, oral cancers (squamous cell carcinoma)
  • Diagnosis:
    • Koilocytes in lesions
    • DNA hybridization, E6/E7 mRNA assays

Polyoma virus

  • Includes JC and BK viruses; latent after primary infection
  • JC virus: progressive multifocal leukoencephalopathy (AIDS, immunodeficiencies)
  • BK virus: hemorrhagic cystitis (bone marrow transplant), transplant nephropathy (renal allograft failure)
  • Diagnosis:
    • Quantify viral DNA in blood, CSF, urine
    • “Decoy” cells in urine cytology (Papanicolaou stain, phase contrast)
    • Biopsy: glassy, basophilic intranuclear inclusions