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