Detection of Human Herpesvirus - 6 in Carcinomas

Abstract

Human herpesvirus-6 (HHV-6), an ubiquitous virus, is the causative agent for exanthem subitum in children, and is frequently associated with lymphoproliferative disorders, including lymphomas. Recently, HHV-6 was reported in oral carcinoma tissue suggesting that it may be a copathogen in these tissues. The objective of this study was to examine the presence of HHV-6
DNA in selected epithelial cell tumours namely, oral carcinoma, salivary gland carcinoma, breast carcinoma and cervical carcinoma. Formalin-fixed, paraffin-embedded archival tissue were examined for the presence of HHV-6 by in situ DNA hybridization. Variant-specific oligonucleotide probes that distinguish HHV-6 type A from type B were used to further classify the viral DNA present. Hybridization studies showed 18/20 (90%) oral carcinoma cases contained HHV-6 DNA. Of the 8 salivary gland tumours, 6 (75%) were positive. A total of 6/20 (30%) cervical carcinoma cases were positive for HHV-6. It was observed that HHV-6 B was the predominant variant in these tissues. All of the 10 breast carcinoma cases were HHV-6 negative. HHV-6 DNA was found in most of the oral carcinoma tissue and in almost a third of the cervical carcinoma tissues studied suggesting a possible role for the agent in these tumours. HHV-6 genome contains at least two genes which may have an oncogenic potential. Also, the virus has the ability to transactivate Human papillomavirus and Human Immunodeficiency virus. Our observations suggest that HHV-6 may be an important cofactor in the pathogenesis of some carcinomas.