Retrospective analysis of varicella zoster virus (VZV) copy DNA numbers in plasma of immunocompetent patients of with herpes zoster, of immunocompromised patients with disseminated VZV disease, and of asymptomatic solid organ transplant recipients

Background. Varicella zoster virus (VZV) causes significant morbidity and mortality in immunocompromised patients. Subclinical reactivation has been described in solid organ recipients and has been associated with graft versus host disease in bone marrow transplantation. Newer studies assessing the prevalence and impact of subclinical VZV reactivation in solid organ transplant (SOT) recipients are lacking. Methods and results. In a first step we developed a highly sensitive quantitative polymerase chain reaction (qPCR) assay for VZV DNA with a detection limit of <= 20 copies/mL. Using this assay we retrospectively analyzed plasma samples of different patient groups for VZV DNA. VZV DNA was found in 10/10 plasma samples of immunocompentent patients with herpes zoster (VZV copy numbers/mL: mean +/- SEM 1710 +/- 1018), in 1/1 sample of a human immunodeficiency virus-infected patient with primary VZV DISEASE (15,192 copies/mL) and in 4/4 plasma samples of immuno-compromised patients with visceral VZV disease (mean of first value 214,214 +/- 178,572). All 108 plasma samples of asymptomatic SOT recipients off any antiviral therapy, randomly sampled over 1 year, were negative for VZV DNA. Conclusion. Our qPCR assay proved to be highly sensitive (100%) in symptomatic VZ V disease. We did not detect subclinical reactivation in asymptomatic SOT recipients during the first post-transplant year. Thus, subclinical VZV reactivation is either a rare event or does not exist. These data need to be confirmed in larger prospective trials.