DETECTION OF HHV-6 GENOTYPES BY IN-SITU HYBRIDIZATION WITH VARIANT-SPECIFIC OLIGONUCLEOTIDE PROBES

Human herpesvirus-6 exists in two forms, HHV-6A which has not been cle arly associated with any disease, and HHV-6B, the causative agent of e xanthem subitum. The two variants have been distinguished by technique s such as dot blotting and restriction fragment length polymorphism of PCR products. This study aims to establish the prevalence of HHV-6A a nd HHV-6B in carcinoma tissues using variant-specific oligonucleotide probes. A total of 73 archived carcinoma biopsies from the oral, saliv ary gland, larynx, breast and cervix were obtained with seven histolog ically normal controls. In situ hybridization was carried out with non radioactively labelled variant-specific probes. Samples that hybridize d with both variant A and B probes were subjected further to nested PC R and digested with HindIII to distinguish the variants. A hybridizati on signal was observed in 76.2% of oral carcinoma tissue and 75.0% of salivary gland carcinoma tissue. In contrast, only 33.3% of cervical c arcinoma tissue were positive for HHV-6 DNA. A hybridization signal wa s noted in all 4 laryngeal carcinoma tissues studied. However, the 10 breast carcinoma tissues studied were negative, as was the histologica lly normal tissue. The virus possesses tumourigenic potential and demo nstrates virus transactivating properties. The frequency of HHV-6 vari ants in certain tumours suggest a cofactorial role in multistep carcin ogenesis. While PCR amplifies selectively the predominant variant in a sample, this was not seen by in situ hybridization. The in situ hybri dization technique allowed the localization of both HHV-6A and HHV-6B in the nuclei of transformed regions. (C) 1997 Elsevier Science B.V.