Characterization of viremia at different stages of varicella-zoster virus infection.

Varicella-zoster virus (VZV) viremia at different stages of infection was characterized. Different approaches were used, polymerase chain reaction (PCR), isothermal transcription based nucleic acid amplification (NASBA), and immunofluorescence to describe and quantitate viral infection of peripheral blood mononuclear cells (PBMC). In patients with acute varicella 200 to 5,000 copies of the viral genome in every 150,000 PBMC were found with quantitative competitive PCR (QCPCR). With NASBA, viral transcriptional activity was detected in these cells. RNA transcribed from the immediate early gene IE 63 as well as from the late gene 68 were found, indicating a productive infection. Glycoprotein gE specific immunofluorescence visualized by confocal laser scanning microscopy revealed that only 1 in 10,000 to 100,000 PBMC was infected. T and B lymphocytes as well as monocytes expressed viral protein on their surface. Similar results were obtained with PBMC from immunocompetent zoster patients. In some cases a transient viremia was found shortly after the onset of rash, although the viral load seemed to be lower than in patients with varicella. Examination of blood samples from 16 persons with postherpetic neuralgia (PHN) signs of viral replication in PBMC were not detected. In conclusion, the data suggest that VZV viremia is a frequent event in patients with varicella and zoster, but not in those with postherpetic neuralgia. Moreover, the results indicated that subclinical reactivations occur both in immunocompromised and immunocompetent individuals.