The association of herpes simplex virus with squamous carcinoma of the cervix, and studies of the virus thymidine kinase gene

Herpes simplex virus (HSV) is an endemic human virus characterized by latent infection of sensory ganglia, with reactivation leading to peripheral lesions in a proportion of cases. The virus genome (145 500 base pairs) comprises two segments, L and S, bounded by inverted repeat regions of approximately 10500 base pairs (TR L and IR L ) and 6000 base pairs (IR s and TR s ) respectively. A direct terminal repeat of about 300 base pairs is also present in an inverted form at the junction between L and S. Numerous indirect studies have suggested an association of the venereal serotype (HSV-2) with squamous carcinoma of the cervix (Nahmias et al . 1970; Thomas & Rawls 1978). Direct evidence has been notably lacking, but the presence of HSV RNA in cervical neoplasms has recently been reported (Jones et al . 1979; McDougall et al . 1980), with in situ hybridization to tritiated HSV DNA. In collaboration with Dr Frank Sharp of the Department of Midwifery, Glasgow University, we have now completed a major screening of cervical neoplasms by the in situ technique. Patients referred to Dr Sharp’s clinic for colposcopic examination were swabbed to detect intracervical infectious HSV. Punch biopsy samples (approximately 5 mm in section) were taken for pathological examination and categorization as non­-neoplastic cervical intraepithelial neoplasia (c. i. n.) or squamous carcinoma. Parallel punches were snap-frozen and thin sections (7 µm) mounted on glass slides, fixed and then hybridized to in vitro 125 I-labelled HSV-2, Ad2, Ad5 or phage lambda DNA. Biopsies of primary adenocarcinomas of the cervix were treated in the same way. After washing and autoradiography, results are expressed as background-corrected mean grain counts per field (mean of ten fields per sample, 3.6 x 10 –2 mm 2 per field; ca . 20 cells per field).