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Infections with herpesvirus and adenovirus is a major cause of morbidity and mortality in patients undergoing stem cell transplantation (SCT). In those patients, the frequency of herpesvirus and adenovirus co-infections as well as their contribution to the infectious burden remain so far unclear. In this study, we have postulated that co-infections with herpesviruses and adenoviruses are frequent in the 100 days following SCT, contributing significantly to the infectious burden. To address this issue, 615 blood samples collected from patients undergoing SCT (n=35) were retrospectively tested by quantitative real-time PCR for the presence of HSV 1/2, VZV, EBV, CMV, HHV6 A/B, and adenovirus. Infections with a single virus were detected in 46.1% (283/615) of the samples, whereas co-infections with two or three viruses were detected in 9.9% (61/615) and 2.1% (13/615) of the samples, respectively. Interestingly, about 50% of the patients (17/35) displayed a co-infection with two or more viruses, with [CMV+HHV6 A/B], and [EBV + HHV6 A/B +adenovirus] being most frequently detected, respectively. Comparison of viral loads indicated that the infectious burden increases proportionally to the number of viruses detected. Moreover, a DNA-microarray allowing simultaneous detection of HSV 1/2, VZV, EBV, CMV, HHV6 A/B, and adenovirus was developed. The assay displayed a high diagnostic accuracy, being an attractive device for routine assessment of the infectious burden in immunocompromised patients after SCT.

Herpesviruses and adenovirus are an important cause of end-organ disease (EOD) and are associated with graft versus host disease (GVHD) in patients undergoing allogeneic stem cell transplantation (SCT). Detection and monitoring of those viruses is routinely performed by simplex quantitative real-time PCR. Since more than one herpes- or adenovirus are reported to be present shortly after transplantation, detection of all possible (sub-)clinical viral infections is still time-consuming and cost-intense. We therefore designed a DNA-microarray for the simultaneous detection of herpes-simplex-virus-1 and -2 (HSV-1/2), cytomegalovirus (CMV), varicella-zoster-virus (VZV), Epstein-Barr-virus (EBV), human herpesvirus-6 (HHV-6) and adenovirus. The DNA-microarray was validated in comparison to simplex quantitative PCR routinely used in our diagnostic laboratory. We retrospectively screened 608 samples of 35 patients undergoing allogeneic SCT on a regular basis until day 100 post-transplantation. The detection limit of the DNA-microarray is 10 genome equivalents (GE)/ml. We detected one or more viruses in 367 samples (60,2%). Of the positive samples, CMV was detected in 272 (74,1%), EBV in 103 (28,1%), HHV-6 in 81 (22,1%), adenovirus in 35 (9,5%), HSV-1/2 in 21 (5,7%) and VZV in 14 samples (5,2%), respectively. Of the samples containing two viruses (n=62), we detected CMV/EBV in 19 (30,6%), CMV/HHV-6 in 27 (43,6%) and HHV-6/EBV in 7 (11,3%) samples, respectively. CMV/EBV/HHV-6 was detected in 4 (36,4%) of the samples containing 3 viruses (n=11). Results of the DNA-microarray showed good overall agreement in comparison to the simplex quantitative PCR. We conclude that the DNA-microarray is a highly sensitive and specific method for the simultaneous detection of up to six viruses in a single sample. By screening and monitoring SCT-patients for viruses known to be associated with EOD or GVHD we herewith introduce an innovative molecular technique that can simultaneously detect multiple viral infections on a large scale. The assay is currently used to determine the impact of multi-virus detection on clinical end-points like GVHD and infectious complications in patients undergoing allogeneic stem cell transplantation.