Chapter 18 - Kaposi's Sarcoma and Human Herpesvirus 8

Abstract

Identification of sequences from a new human herpesvirus in tumour tissue from AIDS-related Kaposi's sarcoma (KS) is done using the technique of Representational Difference Analysis (RDA). This technique uses cycles of polymerase chain reaction (PCR) and subtractive hybridization to amplify and enrich low-abundance DNA sequences present in only one of two otherwise identical DNA populations, and is therefore ideal for determining small differences between complex genomes. KS tumour usually appears as brownish-purple lesions, often on the extremities, but may in more aggressive forms of the disease progress to involve organs such as the lungs, lymph nodes, and gastrointestinal tract. The lesions contain many types of cell but are characterized histologically by the presence of elongated spindle cells and irregular slit-like vascular spaces. Seroepidemiology and PCR studies strongly suggest that HHV-8 is the cause of Kaposi's sarcoma and primary effusion lymphoma, and is also associated with multicentric Castleman's disease. Although HHV-8 has not yet been shown to be a transforming virus in vitro, the virus encodes several proto-oncogenes capable of the deregulation of cell cycle control, inhibition of apoptosis and control of growth differentiation, which could contribute to tumour formation.