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  • There are studies that evaluated the stability of CMV


    There are studies that evaluated the stability of CMV DNA over different periods of time. A study that evaluated stability of EDTA plasma samples stored over a 21-day period at 4 °C found no significant change in the viral loads or any trend of continued DNA degradation [9]. Another study did not find a reduction in CMV viability evaluated by TCID50 for breast milk samples stored at 4 °C or −20 °C up to 21 days [10]. Our findings are in agreement with these studies as the results showed no significant change on CMV stability with prolonged storage at −20 °C for 90 days.
    Funding This work was supported in part by the Emory Center for AIDS Research (P30 AI050409).
    Competing interests
    Ethical approval
    Background Allogenic hematopoietic stem cell transplantation (alloHSCT) recipients are at significant risk for infectious complications [[1], [2]]. The human cytomegalovirus (CMV) is a life-long persisting virus with a prevalence between 45 and 100% in the general adult population [3]. Recurrent reactivations in healthy individuals are common, but occur usually in the absence of symptoms [4]. In immunocompromised individuals like alloHSCT recipients, CMV reactivation is associated with severe and fatal complications. Prophylaxis and preemptive antiviral therapy with ganciclovir or valganciclovir guided by regular quantitative real-time PCR surveillance are currently well-established strategies to prevent significant CMV reactivation [[5], [6]]. However, these strategies may lead to unintended side-effects [7], development of antiviral resistance [8] and increased costs for drugs and diagnostic surveillance [9]. To optimize prophylaxis and preemptive therapy, monitoring of the CMV-specific CD8+ T-cell immune response by the QuantiFERON (QF)-CMV-assay has been established and described in numerous studies concerning patients undergoing bone marrow or solid organ transplantations [[9], [10], [11]]. The QF-CMV-assay is a whole blood ELISA-based interferon-γ (IFN-γ) assay that allows IFN-γ level quantification in a defined blood volume. The test consists of 23 CMV peptides from diverse HLA cox pathway covering approximately 95% of the general population [12]. This procedure is useful in identifying individuals at high-risk for CMV in solid organ and hematopoetic stem cell transplantation [[10], [13], [14], [15]]. Furthermore, combined virological and immunological monitoring allows estimating the individual risk for CMV reactivation after transplantation and adjusting antiviral treatment. However, a close CMV-PCR monitoring is still needed and an IFN-γ threshold determined by the QF-CMV-assay correlating with protection from high-level viremia (CMV-DNA > 5000 copies/ml) has not yet been determined.
    Study design
    Discussion Recurrent CMV reactivations in HSCT recipients resulting in CMV-associated complications including pneumonia, gastrointestinal infections, retinitis or central nervous system infections are a serious health problem and have a major impact on morbidity and mortality in these patients [17]. Optimal monitoring and preemptive treatment of CMV after alloHSCT can significantly improve overall outcomes. A major challenge in monitoring transplant recipients for CMV reactivations is the determination of a CMV-DNA threshold that is associated with CMV-disease. Numerous studies with solid organ or bone marrow transplants suggested different CMV-DNA levels ranging from 600 to 10,000 copies/ml plasma/blood as a cutoff for predicting disease [[18], [19], [20]]. Unfortunately, there is no consensus concerning the magnitude of CMV viral loads, which indicate antiviral treatment after HSCT [[21], [22]]. Some clinical centers begin antiviral therapy once CMV-DNA is detectable regardless of viral loads, while others have set a CMV viral load threshold at higher levels. On the basis of the clinical experience of our center, we consider 5000 copies/ml as a threshold for high-level viremia enhancing the risk for CMV-associated complications. In this study, we observed CMV-associated symptoms only in two patients. Both were at high risk (D−/R+) for CMV-disease and developed colitis in correlation with high-level viremia. Usually, antiviral treatment with ganciclovir or valganciclovir is started, if a reduction of immunosuppressive therapy is not possible or ineffective [22]. Particularly, because of bone marrow and renal toxic side effects of these drugs a more precise prediction of the risk for CMV-associated complication is needed [21]. The QF-CMV-assay determining the reconstitution of protective T-cell immunity was developed as an additional diagnostic tool for assessing the risk for CMV reactivation and disease [12]. The control of CMV viremia is dependent upon an adequate expansion of functional CMV-specific T-cells [23]. The limit of detection of the QF-CMV-assay is given with ≥ 0.2 IU/l. However, there is no evidence that this value correlates with the biological function of T-cells and with protection from high-level viremia. Although numerous studies in solid organ or bone marrow transplants have been undertaken, no IFN-γ threshold associated with protection from high-level CMV reactivation has been determined to date.