Detection of Marek's disease virus DNA in chicken but not in human plasma

Abstract

Marek's disease virus (MDV) causes a common lymphomatous and neuropathic disease in domestic chickens and, less commonly, turkeys and quail. It is a member of the alpha-herpesviruses and until now was considered to be strongly cell associated. In 1991, MDV was suggested to be the causative infectious agent of multiple sclerosis (MS) in humans. In a previous study, we investigated the leukocytes of 107 well-defined MS patients for the presence of MDV DNA but were unable to confirm a role for MDV in the pathogenesis of MS. A recent report (S. Laurent, E. Esnault, G. Dambrine, A. Goudeau, D. Choudat, and D. Rasschaert, J. Gen. Virol. 82:233-240, 2001) described the detection of MDV DNA in 20% of 202 human serum samples, regardless of whether the individuals were exposed to poultry. The detection of MDV DNA in chicken serum samples was reported as well. The aim of the present study was to investigate whether we can confirm the presence of MDV DNA in chickens and humans if we use plasma as the source for nucleic acid isolation. Leukocytes and plasma specimens from 16 chickens experimentally infected with MDV serotype 1 and plasma specimens from 300 volunteer blood donors were tested for MDV DNA by two different TaqMan PCR assays. MDV DNA was repeatedly found in the leukocytes as well as in the plasma specimens of all 16 animals. All human samples analyzed, however, tested negative by both assays. Accordingly, Marek's disease in chickens can be diagnosed by detection of MDV DNA in plasma as well as in leukocytes. Once again, we found no evidence for the spread of MDV to humans.

FIG. 1.

Amplification plots from the TaqMan MDV PCR (method 2) with chicken leukocytes (A) and chicken plasma specimens (B) (n = 16 each), as well as with one no-template control (NTC). The relative fluorescence units (ΔRn) for the MDV reporter dye over the course of cycles 10 to 40 are shown. The results presented here, as well as those presented in Fig. 2 and 3, are screen shots of the original experiments.

FIG. 2.

Comparison of TaqMan MDV PCR methods 1 and 2 performed with DNA isolated from the leukocytes of 14 of 16 chickens. For a clear arrangement, the results for two chickens with markedly higher C_T values were excluded (see Fig. 1B). The amplification plots of methods 1 and 2 are divided by the unlabeled arrow. Method 2 had lower C_T values and higher relative fluorescence units (ΔRn) and thus had a higher sensitivity than method 1. NTC, no-template control.

FIG. 3.

Amplification plots of a control TaqMan PCR for detection of human β-actin genomic sequences. The results of a representative experiment are shown. Plasma samples from 18 human blood donors that tested negative for MDV DNA by both PCR tests were analyzed. NTC, no-template control; ΔRn, relative fluorescence units.