Molecular monitoring of viral infections after hematopoietic stem cell transplantation

Torque teno virus-DNA load as individual cytomegalovirus risk assessment parameter upon allogeneic hematopoietic stem cell transplantation

BACKGROUND

Immune recovery following allogeneic hematopoietic stem cell transplantation (allo-HSCT) decisively influences the occurrence of opportunistic infections, one of the leading causes of death among this group of patients. Yet, today, there are no laboratory parameters mirroring immune function sufficiently. Torque teno virus (TTV) has already proven itself as a functional immune marker in other settings.

AIMS

In this analysis, we investigated whether monitoring of TTV-DNA load in whole blood is able to provide additional information on the capacity of the immune system to control cytomegalovirus (CMV) replication in allo-HSCT recipients.

METHODS

Whole blood samples from 59 patients were collected upon allo-HSCT (between Day -7 and +10), on Day +14, +21, +28, +56, +90, and +365 post-transplant. TTV-DNA loads and other relevant clinical information were correlated with the risk of CMV infections or reactivations, defined by evidence of viral replication in blood.

RESULTS

CMV serostatus of the recipient and a TTV load below 1000 copies/mL upon allo-HSCT were significantly associated with an increased incidence of CMV infection or reactivation.

CONCLUSIONS

Quantification of TTV load in the early phase of allo-HSCT procedure could provide additional information in order to identify patients at risk for CMV infection or reactivation.

Febrile illness in high-risk children: a prospective, international observational study

To assess and describe the aetiology and management of febrile illness in children with primary or acquired immunodeficiency at high risk of serious bacterial infection, as seen in emergency departments in tertiary hospitals. Prospective data on demographics, presenting features, investigations, microbiology, management, and outcome of patients within the 'Biomarker Validation in HR patients' database in PERFORM, were analysed. Immunocompromised children (< 18 years old) presented to fifteen European hospitals in nine countries, and one Gambian hospital, with fever or suspected infection and clinical indication for blood investigations. Febrile episodes were assigned clinical phenotypes using the validated PERFORM algorithm. Logistic regression was used to assess the effect size of predictive features of proven/presumed bacterial or viral infection. A total of 599 episodes in 482 children were analysed. Seventy-eight episodes (13.0%) were definite bacterial, 67 episodes probable bacterial (11.2%), and 29 bacterial syndrome (4.8%). Fifty-five were definite viral (9.2%), 49 probable viral (8.2%), and 23 viral syndrome (3.8%). One hundred ninety were unknown bacterial or viral infections (31.7%), and 108 had inflammatory or other non-infectious causes of fever (18.1%). Predictive features of proven/presumed bacterial infection were ill appearance (OR 3.1 (95% CI 2.1-4.6)) and HIV (OR 10.4 (95% CI 2.0-54.4)). Ill appearance reduced the odds of having a proven/presumed viral infection (OR 0.5 (95% CI 0.3-0.9)). A total of 82.1% had new empirical antibiotics started on admission (N = 492); 94.3% proven/presumed bacterial (N = 164), 66.1% proven/presumed viral (N = 84), and 93.2% unknown bacterial or viral infections (N = 177). Mortality was 1.9% (N = 11) and 87.1% made full recovery (N = 522).   Conclusion: The aetiology of febrile illness in immunocompromised children is diverse. In one-third of cases, no cause for the fever will be identified. Justification for standard intravenous antibiotic treatment for every febrile immunocompromised child is debatable, yet effective. Better clinical decision-making tools and new biomarkers are needed for this population. What is Known: • Immunosuppressed children are at high risk for morbidity and mortality of serious bacterial and viral infection, but often present with fever as only clinical symptom. • Current diagnostic measures in this group are not specific to rule out bacterial infection, and positivity rates of microbiological cultures are low. What is New: • Febrile illness and infectious complications remain a significant cause of mortality and morbidity in HR children, yet management is effective. • The aetiology of febrile illness in immunocompromised children is diverse, and development of pathways for early discharge or cessation of intravenous antibiotics is debatable, and requires better clinical decision-making tools and biomarkers.

Target Enrichment Metagenomics Reveals Human Pegivirus-1 in Pediatric Hematopoietic Stem Cell Transplantation Recipients

Human pegivirus-1 (HPgV-1) is a lymphotropic human virus, typically considered nonpathogenic, but its infection can sometimes cause persistent viremia both in immunocompetent and immunosuppressed individuals. In a viral discovery research program in hematopoietic stem cell transplant (HSCT) pediatric patients, HPgV-1 was detected in 3 out of 14 patients (21.4%) using a target enrichment next-generation sequencing method, and the presence of the viruses was confirmed by agent-specific qRT-PCR assays. For the first time in this patient cohort, complete genomes of HPgV-1 were acquired and characterized. Phylogenetic analyses indicated that two patients had HPgV-1 genotype 2 and one had HPgV-1 genotype 3. Intra-host genomic variations were described and discussed. Our results highlight the necessity to screen HSCT patients and blood and stem cell donors to reduce the potential risk of HPgV-1 transmission.

Enhancement of Antiviral T-Cell Responses by Vitamin C Suggests New Strategies to Improve Manufacturing of Virus-Specific T Cells for Adoptive Immunotherapy

Allogeneic and autologous transplantation of hematopoietic stem cells (HSCT) are being routinely used to treat patients with leukemia and lymphoma. Due to the required immunosuppression after stem cell transplantation, infection and reactivation by viruses are life-threatening complications. In recent years, adoptive transfer using virus-specific T cells (VSTs) has emerged as alternative to conventional therapies. Since vitamins are described to influence the immune system and its cellular components, the aim of this study was to examine whether vitamins modulate VST function and thereby enable an improvement of therapy. For that, we investigated the impact of vitamin C and D on the functionality of cytomegalovirus (CMV)-specific T cells isolated from CMV-seropositive healthy donors. We were able to show that vitamin C increases the expansion and activation state of CMV-specific T cells, and an increased influence of vitamin C was observed on cells isolated from male donors and donors above 40 years of age. A higher frequency of the terminally differentiated effector memory CD8+ T-cell population in these donors indicates a connection between these cells and the enhanced response to vitamin C. Thus, here we provide insights into the impact of vitamin C on cytotoxic T cells as well as possible additional selection criteria and strategies to improve VST functionality.

A Comprehensive Statistical Framework for Determination of Commutability, Accuracy, and Agreement in Clinical DNAemia Assays

Despite advances in the standardization of quantitative DNAemia tests and efforts to better understand and characterize the performance of reference materials in different assays, it remains unclear how the commutability performance of reference materials is related to intra- and interassay agreement. Building upon previous work, we describe a comprehensive framework to determine the relationship of commutability with assay accuracy and agreement. The use of this framework is illustrated using previously generated data regarding the performance of four quantitative Epstein-Bar virus (EBV) PCR assays with the WHO and ABI standards as examples. The use of these statistical tools can link the performance characteristics of one or more assays with predetermined clinical decision limits and may help improve the development, validation, and clinical utility of such DNAemia tests.

Performance of an in-house real-time PCR assay for detecting Cytomegalovirus infection among transplant patients from a tertiary care centre

Background

Quantitative Cytomegalovirus (CMV) polymerase chain reactions are increasingly being used for monitoring CMV DNAemia in haematopoietic stem cell transplants and solid organ transplants.

Objective

In this study, a commercial CMV viral load assay was compared with an in-house viral load assay.

Materials and Methods

A total of 176 whole-blood samples were tested for CMV DNAemia using both assays.

Results

Our evaluation showed a difference of 1 log₁₀copies/ml between the two assay systems in determining CMV viral loads in the clinical samples.

Conclusion

The in-house viral load assay had a better correlation with clinical findings compared to the commercial assay. Quality assessment of these assays was done by the United Kingdom National External Quality Assessment Scheme (UKNEQAS), an external proficiency testing programme, and by the National Institute for Biological Standard and Control (NIBSC) standard. For UKNEQAS and NIBSC standards, the bias between the assays was 0.73 log₁₀and 0.85 log₁₀, respectively. This difference is well within the acceptable range already reported in the literature.

The Case for Laboratory Developed Procedures: Quality and Positive Impact on Patient Care

An explosion of knowledge and technology is revolutionizing medicine and patient care. Novel testing must be brought to the clinic with safety and accuracy, but also in a timely and cost-effective manner, so that patients can benefit and laboratories can offer testing consistent with current guidelines. Under the oversight provided by the Clinical Laboratory Improvement Amendments, laboratories have been able to develop and optimize laboratory procedures for use in-house. Quality improvement programs, interlaboratory comparisons, and the ability of laboratories to adjust assays as needed to improve results, utilize new sample types, or incorporate new mutations, information, or technologies are positive aspects of Clinical Laboratory Improvement Amendments oversight of laboratory-developed procedures. Laboratories have a long history of successful service to patients operating under Clinical Laboratory Improvement Amendments. A series of detailed clinical examples illustrating the quality and positive impact of laboratory-developed procedures on patient care is provided. These examples also demonstrate how Clinical Laboratory Improvement Amendments oversight ensures accurate, reliable, and reproducible testing in clinical laboratories.

Dynamics of Torque Teno virus viremia could predict risk of complications after allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an established treatment option for several hematological diseases. However, the first year post-transplantation is often complicated by infections and graft-versus-host disease (GVHD). Improvements in immunological monitoring could reduce such post-transplant complications. Torque Teno virus (TTV), a chronically persisting DNA virus, is reported to be a marker for immune function in immunocompromised patients. In the present study, the TTV kinetics were analyzed to investigate the potential role of TTV viremia as immune-competence read-out after allo-HSCT. Twenty-three monocentric allo-HSCT recipients were retrospectively tested for TTV-DNA in whole blood at given day post-transplant. Dynamics of TTV viremia was analyzed with respect to episodes of non-TTV viral reactivations (CMV, EBV, and BKPyV), acute GVHD, and recovery of immune cells. Recipients affected by persisting viral infections and/or GVHD during the first 100 days after allo-HSCT showed a significantly higher median TTV load at day +30 than patients with a less complicated clinical course (p = 0.005). This was also associated with a total lymphocyte count <5.5E+08 cells/L in this high-risk group (p = 0.039). These findings suggest that TTV could represent an additional parameter to identify patients at higher risk for complications in the first 100 days following allo-HSCT. Prospective studies, including the monitoring of lymphocyte subsets, are required to define the potential use of TTV in immunological monitoring after allo-HSCT.

Comparative Performance of Reagents and Platforms for Quantitation of Cytomegalovirus DNA by Digital PCR

A potential benefit of digital PCR is a reduction in result variability across assays and platforms. Three sets of PCR reagents were tested on two digital PCR systems (Bio-Rad and RainDance), using three different sets of PCR reagents for quantitation of cytomegalovirus (CMV). Both commercial quantitative viral standards and 16 patient samples (n = 16) were tested. Quantitative accuracy (compared to nominal values) and variability were determined based on viral standard testing results. Quantitative correlation and variability were assessed with pairwise comparisons across all reagent-platform combinations for clinical plasma sample results. The three reagent sets, when used to assay quantitative standards on the Bio-Rad system, all showed a high degree of accuracy, low variability, and close agreement with one another. When used on the RainDance system, one of the three reagent sets appeared to have a much better correlation to nominal values than did the other two. Quantitative results for patient samples showed good correlation in most pairwise comparisons, with some showing poorer correlations when testing samples with low viral loads. Digital PCR is a robust method for measuring CMV viral load. Some degree of result variation may be seen, depending on platform and reagents used; this variation appears to be greater in samples with low viral load values.

Quantitative Assessment of Commutability for Clinical Viral Load Testing Using a Digital PCR-Based Reference Standard

Given recent advances in the development of quantitative standards, particularly WHO international standards, efforts to better understand the commutability of reference materials have been made. Existing approaches in evaluating commutability include prediction intervals and correspondence analysis; however, the results obtained from existing approaches may be ambiguous. We have developed a "deviation-from-ideal" (DFI) approach to evaluate commutability of standards and applied it to the assessment of Epstein-Bar virus (EBV) load testing in four quantitative PCR assays, treating digital PCR as a reference assay. We then discuss advantages and limitations of the DFI approach as well as experimental design to best evaluate the commutability of an assay in practice.

Analysis of the shedding of three β-herpesviruses DNA in Polish patients subjected to allogeneic hematopoietic stem cell transplantation: Six-year follow up

BACKGROUND

Infections with human β-herpesviruses are common worldwide and are still frequent in patients after hematopoietic stem cell transplantation. Some data suggest that HHV-6 and HHV-7 could take part in CMV reactivation from latency and/or progression of CMV disease in immunosupressed patients.

OBJECTIVES

The aims of this study were: (1) to summarise retrospectively the results of β-herpesviruses DNA detection in a large group of adult allogeneic haematopoietic stem cell transplant recipients; and (2) to find a potential correlation between viruses belonging to this subfamily.

STUDY DESIGN

AlloHSCT recipients (N=142) were examined in the early post-transplant period (median=89 days). The presence of CMV, HHV-6 and HHV-7 was confirmed through detection and quantification of viral DNA, isolated from 1679 sera samples.

RESULTS

CMV DNA alone was detected in 23.9% of patients, while single HHV-6 and HHV-7 were detected in 14.8% and 9.9% of individuals, respectively. The reactivation of more than one virus was identified in 31% of analysed patients. In cases of concurrent infection, HHV-7 was detected at the same time as HHV-6, and both of them were usually reactivated before CMV. The kinetics of virus reactivation and measured viral load may suggest a potential role of HHV-6 and HHV-7 as co-factors in CMV reactivation.

CONCLUSIONS

The observed kinetics of virus reactivation may strongly suggest a potential role of HHV-6 and/or HHV-7 as co-factors of CMV reactivation. The co-infection with these β-herpesviruses could predispose patients after hematopoietic stem cell transplantation to a longer and more severe CMV infection.

Prolonged outbreak of adenovirus A31 in allogeneic stem cell transplant recipients

BACKGROUND

An outbreak of human adenovirus (HAdV) A31 occurred from December 2011 to March 2012 at the Center for Allogeneic Stem Cell Transplantation (CAST), Karolinska University Hospital in Sweden. We analyzed the outbreak, the routes of transmission, and report the medical consequences.

METHODS

The medical records of all patients admitted to CAST during the outbreak period were studied. Phylogenetic analysis of the patient HAdV strains was performed by sequencing the hexon gene and the more variable E3 gene.

RESULTS

We identified 9 cases of HAdV A31. Hygiene measures were implemented, but transmission continued for 2 months. All 9 patients had been admitted to the ward, but 2 had no connection in time to other known HAdV A31 cases. DNA sequencing of the patient strains strongly suggested nosocomial transmission. Transplantation was postponed and then cancelled in 1 patient, and 5 patients were treated with cidofovir because of high levels of viremia. In 7 patients, concomitant graft-versus-host disease (GVHD) grade II-V complicated the clinical picture, as it was difficult to distinguish symptoms of GVHD from those of HAdV infection.

CONCLUSION

An outbreak of HAdV in HSCT recipients can be difficult to control. Although none of the patients had severe disease, the medical consequences were significant. It is possible that unidentified cases with mild symptoms may have caused continuous transmission at the unit. Regular testing of all patients several weeks beyond the last case identified may be an important measure to control transmission.

Characteristics and outcomes of patients diagnosed with norovirus gastroenteritis after allogeneic hematopoietic stem cell transplantation based on immunochromatography

Norovirus gastroenteritis (NV-GE) is a highly transmittable disease that can lead to fatal outcomes in vulnerable populations including patients after hematopoietic stem cell transplantation (HSCT). Prompt detection of NV is therefore important for HSCT recipients. Immunochromatography (IC) can be used to easily and rapidly diagnose NV-GE by detecting NV antigens. In this study, we examined 642 stool specimens in patients who developed diarrhea after allogeneic HSCT between January 2007 and June 2011. NV was detected in 10 of 350 (2.9 %) HSCT recipients. The median onset of symptoms was 36 days (range 3-93) after HSCT. The median duration of symptoms was 42 days (3-135). A second or subsequent allogeneic HSCT was associated with a higher incidence of NV-GE (P = 0.034). Of four patients who underwent colonoscopy, two showed intestinal graft-versus-host disease (GVHD) histopathology, whereas the other two showed no evidence of GVHD, and thus no need for intensified immunosuppression. None of the patients died of NV-GE. In conclusion, IC may be useful in the differential diagnosis of diarrhea after allogeneic HSCT, and could enable the appropriate adjustment of immunosuppressive drugs and prompt preventive measures.

Comparative evaluation of three commercial quantitative cytomegalovirus standards by use of digital and real-time PCR

The recent development of the 1st WHO International Standard for human cytomegalovirus (CMV) and the introduction of commercially produced secondary standards have raised hopes of improved agreement among laboratories performing quantitative PCR for CMV. However, data to evaluate the trueness and uniformity of secondary standards and the consistency of results achieved when these materials are run on various assays are lacking. Three concentrations of each of the three commercially prepared secondary CMV standards were tested in quadruplicate by three real-time and two digital PCR methods. The mean results were compared in a pairwise fashion with nominal values provided by each manufacturer. The agreement of results among all methods for each sample and for like concentrations of each standard was also assessed. The relationship between the nominal values of standards and the measured values varied, depending upon the assay used and the manufacturer of the standards, with the degree of bias ranging from +0.6 to -1.0 log10 IU/ml. The mean digital PCR result differed significantly among the secondary standards, as did the results of the real-time PCRs, particularly when plotted against nominal log10 IU values. Commercially available quantitative secondary CMV standards produce variable results when tested by different real-time and digital PCR assays, with various magnitudes of bias compared to nominal values. These findings suggest that the use of such materials may not achieve the intended uniformity among laboratories measuring CMV viral load, as envisioned by adaptation of the WHO standard.

Cytomegalovirus infection in patients who underwent allogeneic hematopoietic stem cell transplantation in Portugal: a five-year retrospective review

Cytomegalovirus (CMV) infection is 1 of the leading causes of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (aHSCT), mainly within the first 100 days after transplantation. We aimed to characterize CMV infection in a cohort of 305 patients with different malignancies undergoing aHSCT at the Portuguese Institute of Oncology of Porto between January 2008 and December 2012. In total, 184 patients (60.3%) developed CMV infection, mainly viral reactivations rather than primary infections (96.2% versus 3.8%, respectively). The majority of patients (166 of 184) developed CMV infection ≤100 days after transplantation, with median time to infection of 29 days (range, 0 to 1285) and median duration of infection of 10 days (range, 2 to 372). Multivariate analysis revealed that CMV infection was increased in donor (D)-/recipient (R)+ and D+/R+ (odds ratio [OR], 10.5; 95% confidence interval [CI], 4.35 to 25.4; P < .001) and in patients with mismatched or unrelated donors (OR, 2.54; 95% CI, 1.34 to 4.80; P = .004). Cox regression model showed that the risk of death was significantly increased in patients >38 years old (OR, 1.89; 95% CI, 1.14 to 3.12; P = .0137), who underwent transplantation with peripheral blood (OR, 3.02; 95% CI, 1.33 to 6.86; P = .008), with mismatched or unrelated donor (OR, 2.16; 95% CI, 1.48 to 3.13; P < .001), and who developed CMV infection (OR, 1.76; 95% CI, 1.07 to 2.90; P = .025). Moreover, patients who developed CMV infection had a significantly reduced median post-transplantation survival (16 versus 36 months; P = .002).

Epstein-Barr virus reactivation in allogeneic stem cell transplantation is highly related to cytomegalovirus reactivation

Monitoring of Epstein-Barr virus (EBV) load and pre-emptive rituximab is an appropriate approach to prevent post-transplant lymphoproliferative disease (PTLD) occurring after hematopoietic stem cell transplantation (HSCT). This pre-emptive approach, based on EBV-DNA monitoring through a quantitative polymerase chain reaction, was applied to 101 consecutive patients who underwent allo HSCT at our Institute (median age 50). A single infusion of rituximab was administered to 11 of 16 patients who were at high risk for progression to PTLD, defined as a DNA value >10 000 copies/mL. All patients cleared EBV DNAemia, without any recurrences. Main factors significantly associated with high risk for PTLD were as follows: (i) unrelated vs. sibling (26% vs. 7%; p = 0.011); (ii) T-cell depletion (29% vs. 6%; p = 0.001); (iii) graft versus host disease (GVHD; 30% vs. 7%; p = 0.002); and (iv) cytomegalovirus (CMV) reactivation (29% vs. 4%; p = 0.001). Multivariate analysis showed that CMV reactivation was the only independent variable associated with EBV reactivation. We conclude that: (i) a single infusion of rituximab is able to prevent the risk of progression into EBV-related PTLD; and (ii) CMV reactivation is strongly associated with EBV reactivation; therefore, an intensive EBV monitoring strategy could be advisable only in case of CMV reactivation.

Impact of pretransplant donor and recipient cytomegalovirus serostatus on outcome for multiple myeloma patients undergoing reduced intensity conditioning allogeneic stem cell transplantation

Scope of the study was to investigate the impact of pre-transplant CMV serostatus of the donor and/or recipient on the outcome of patients undergoing allogeneic hematopoietic stem cell transplantation (Allo-SCT) for Multiple Myeloma (MM). To our knowledge no data are available in the literature about this issue. We retrospectively followed 99 consecutive patients who underwent reduced-intensity conditioning (RIC) Allo-SCT for MM in our cancer center at Marseille between January 2000 and January 2012. Based upon CMV serostatus, patients were classified as low risk (donor [D]-/recipient [R] -) 17 patients (17.1%), intermediate risk (D+/R) 14 patients (14.1%), or high risk - either (D-/R+) 31 patients (31.3%) or (D+/R+), 37 patients (37.3%). Cumulative incidence of CMV reactivation was 39% with a median time of 61 days (26-318). Three patients (3%) developed CMV disease. Two factors were associated with CMV reactivation: CMV serostatus group (low: 0% vs. intermediate: 29% vs. high: 50%; p=0.001) and the presence of grade II-IV acute GvHD (Hazard Ratio: HR=2.1 [1.1-3.9]). Thirty-six of the 39 patients (92%) with CMV reactivation did not present positive detection of CMV after a 21-day median duration preemptive treatment with ganciclovir. Cumulative incidence of day 100 grade II-IV acute GvHD, 1-year chronic GvHD and day 100 transplantation related mortality (TRM) were 37%, 36% and 9%, respectively. CMV reactivation and serostatus were not associated with increased GvHD and TRM or short survival. Only the presence of acute GvHD as a time dependent variable was significantly associated with increased TRM (p=0.005). Two-year overall and progression free survival were 56% and 34%, respectively. Donor and recipient CMV serostatus and acute GvHD are independent factors for increased CMV reactivation in high-risk MM patients undergoing RIC Allo-SCT. However, we did not find any influence of CMV reactivation on post transplantation outcome. CMV monitoring and pre-emptive treatment strategy could in part explain these results. Novel prophylactic measures such as immunotherapy and drug prophylaxis need to be considered in this group of patients, warranting further prospective studies.

Comparison of droplet digital PCR to real-time PCR for quantitative detection of cytomegalovirus

Quantitative real-time PCR (QRT-PCR) has been widely implemented for clinical viral load testing, but a lack of standardization and relatively poor precision have hindered its usefulness. Digital PCR offers highly precise, direct quantification without requiring a calibration curve. Performance characteristics of real-time PCR were compared to those of droplet digital PCR (ddPCR) for cytomegalovirus (CMV) load testing. Tenfold serial dilutions of the World Health Organization (WHO) and the National Institute of Standards and Technology (NIST) CMV quantitative standards were tested, together with the AcroMetrix CMV tc panel (Life Technologies, Carlsbad, CA) and 50 human plasma specimens. Each method was evaluated using all three standards for quantitative linearity, lower limit of detection (LOD), and accuracy. Quantitative correlation, mean viral load, and variability were compared. Real-time PCR showed somewhat higher sensitivity than ddPCR (LODs, 3 log(10) versus 4 log(10) copies/ml and IU/ml for NIST and WHO standards, respectively). Both methods showed a high degree of linearity and quantitative correlation for standards (R(2) ≥ 0.98 in each of 6 regression models) and clinical samples (R(2) = 0.93) across their detectable ranges. For higher concentrations, ddPCR showed less variability than QRT-PCR for the WHO standards and AcroMetrix standards (P < 0.05). QRT-PCR showed less variability and greater sensitivity than did ddPCR in clinical samples. Both digital and real-time PCR provide accurate CMV load data over a wide linear dynamic range. Digital PCR may provide an opportunity to reduce the quantitative variability currently seen using real-time PCR, but methods need to be further optimized to match the sensitivity of real-time PCR.

Epstein-Barr virus: general factors, virus-related diseases and measurement of viral load after transplant

The Epstein-Barr virus is responsible for infectious mononucleosis syndrome and is also closely associated to several types of cancer. The main complication involving Epstein-Barr virus infection, both in recipients of hematopoietic stem cells and solid organs, is post-transplant lymphoproliferative disease. The importance of this disease has increased interest in the development of laboratory tools to improve post-transplant monitoring and to detect the disease before clinical evolution. Viral load analysis for Epstein-Barr virus through real-time polymerase chain reaction is, at present, the best tool to measure viral load. However, there is not a consensus on which sample type is the best for the test and what is its predictive value for therapeutic interventions.

Mesenchymal stromal cells do not increase the risk of viral reactivation nor the severity of viral events in recipients of allogeneic stem cell transplantation

Mesenchymal stromal cells (MSC) are tested in clinical trials to treat graft versus host disease (GvHD) after stem cell transplantation (SCT). In vitro studies demonstrated MSC's broad immunosuppressive activity. As infections represent a major risk after SCT, it is important to understand the role of MSC in this context. We analyzed 24 patients (pts) receiving MSC for GvHD in our Unit between 2009 and 2011. We recorded viral reactivations as measured in whole blood with polymerase chain reaction for 100 days following MSC administration. In patients with a documented viral reactivation in the first 3 days following MSCs infusion the frequency of virus-specific IFNgamma-producing cells was determined through enzyme-linked immunospot assay. In our cohort of patients viral reactivation after MSC infusion occurred in 45% of the cases, which did not significantly differ from the incidence in a historical cohort of patients affected by steroid resistant GvHD and treated with conventional immunosuppression. No patient presented severe form of infection. Two cases could be checked for immunological response to viral stimulus and demonstrated virus specific T-cytotoxic lymphocyte activity. In our experience MSC infusion did not prove to trigger more frequent or severer viral reactivations in the post transplantation setting.

Adenoviral load diagnostics by quantitative polymerase chain reaction: techniques and application

Human adenoviruses (HAdV) can cause fatal complications such as disseminated disease especially in a post-transplant setting. With conventional methods, disseminated HAdV disease could only be diagnosed with delay. Quantification of the HAdV load by real-time PCR in peripheral blood promised to solve this diagnostic dilemma. Here we review the development, applications and significance of quantitative HAdV PCR. The high genetic divergence of the 56 HAdV types was a major obstacle for developing a quantitative HAdV PCR covering all types. Several protocols focused either on a few, probably predominating types or tried to detect all known HAdV types by using a bundle of assays or a few multiplexed PCRs. Alternatively, generic quantitative real-time HAdV PCR protocols using primer and probe consensus sequences have been designed, providing considerable reduction of costs and hands-on time. Application of HAdV load testing by several studies on stem cell transplant (SCT) recipients indicated that rapidly increasing HAdV blood loads as well as high HAdV DNAemia (e.g. >10(4) copies/ml) are predictive for disseminated HAdV disease although a universal threshold value has not yet been established. HAdV load testing has been implemented for systematic screening of SCT patients permitting early diagnosis, pre-emptive treatment initiation and monitoring of antiviral therapy. However, further investigations are required to validate proposed virus load thresholds. Moreover, other applications of quantitative HAdV PCR, such as the diagnosis of localized HAdV disease, the analysis of environmental samples and monitoring of gene therapy with adenoviral vectors will be addressed in this review.

Dominance of variant A in human herpesvirus 6 viraemia after renal transplantation

Background

Human herpesvirus 6 (HHV-6), mostly variant B reactivation in renal transplant patients has been published by other authors, but the pathogenetic role of HHV-6 variant A has not been clarified. Our aims were to examine the prevalence of HHV-6, to determine the variants, and to investigate the interaction between HHV-6 viraemia, human cytomegalovirus (HCMV) infection and clinical symptoms.

Methods

Variant-specific HHV-6 nested PCR and quantitative real-time PCR were used to examine blood samples from renal transplant patients and healthy blood donors for the presence and load of HHV-6 DNA and to determine the variants. Active HHV-6 infection was proved by RT-PCR, and active HCMV infection was diagnosed by pp65 antigenaemia test.

Results

HHV-6 viraemia was significantly more frequent in renal transplant patients compared to healthy blood donors (9/200 vs. 0/200; p = 0.004), while prevalence of HHV-6 latency was not significantly different (13/200 vs. 19/200; p > 0.05). Dominance of variant A was revealed in viraemias (8/9), and the frequency of HHV-6A was significantly higher in active infections compared with latency in renal transplant patients (8/9 vs. 2/13; p = 0.0015). Latency was established predominantly by HHV-6B both in renal transplant patients and in healthy blood donors (11/13 and 18/19). There was no statistical significant difference in occurrence of HCMV and HHV-6 viraemia in renal transplant patients (7/200 vs. 9/200). Statistical analysis did not reveal interaction between HHV-6 viraemia and clinical symptoms in our study.

Conclusions

Contrary to previous publications HHV-6A viraemia was found to be predominant in renal transplant patients. Frequency of variant A was significantly higher in cases of active infection then in latency.