Human Herpes-8 virus copy to cell ratio: A diagnostic tool in primary effusion lymphoma

Primary effusion lymphoma (PEL) is a serious sequel to Human Herpes Virus 8 (HHV8) infection in the immunosuppressed host. Usually requiring a cytological diagnosis, body cavity effusions are often referred for investigation for possible PEL. Although absence of HHV8 effectively refutes this, the presence of HHV8 DNA, though indicative is not diagnostic. Referred effusion and plasma samples from 10 patients with HHV8-related pleural and pericardial effusions were submitted for quantitative investigations. HHV8 DNA and human DNA from unseparated effusion extracts have been quantified allowing estimation of virus-to-cell ratios in effusion fluid. These ratios varied widely between 0.003 and 700. Five fluids had in excess of 10⁶ HHV-8 DNA genome equivalents per ML (GEq/ML), ranging between 18 and 300 million GEq/ML. Four of these five effusions were from patients with cytologically proven PEL and had virus to cell (V:C) ratios between 100 and 700 to 1. The remaining high load effusion exhibited a ratio of 1.6 to 1 and came from a patient with extensive thoracic Kaposi's sarcoma. Five effusion fluids with low viral loads exhibited virus to cell ratios between 0.003 and 0.5. High effusion HHV8 load, though supportive of a diagnosis of PEL is less accurate than using virus to cell ratios.