Highlights
- •Human cytomegalovirus (HCMV)-seropositive (IgG-positive/IgM-negative) hematopoietic stem cell transplantation recipients exhibited a high rate of herpesvirus infections, particularly Epstein–Barr virus (EBV).
- •Anti-thymocyte globulin and male sex were strongly associated with an increased risk of EBV infection.
- •Graft-versus-host disease prophylaxis with prednisone was determined to affect both EBV and HCMV infections.
- •Prior infection with EBV was shown to promote human herpes virus type 6 infection.
Summary
Background
Viral infections are a major cause of morbidity and mortality after hematopoietic stem cell transplantation (HSCT). The effect of herpesvirus infections in human cytomegalovirus (HCMV)-seropositive (IgG-positive/IgM-negative) HSCT recipients remains poorly understood. The risk factors associated with Epstein–Barr virus (EBV), HCMV, and human herpes virus type 6 (HHV-6) infections after HSCT, both alone and in combination, were investigated in this study.
Methods
Peripheral blood specimens were collected from 44 HSCT recipients and examined for viral DNA using quantitative fluorescence PCR assays. Risk factors for EBV, HCMV, and HHV-6 infections were analyzed by binary logistic regression, and relationships between these viruses were analyzed using the Chi-square test.
Results
EBV, HCMV, and HHV-6 were detected in 50%, 45.45%, and 25% of HCMV-seropositive (IgG-positive/IgM-negative) HSCT recipients, respectively. Male sex (p = 0.007) and conditioning regimens including anti-thymocyte globulin (ATG) (p = 0.034) were strongly associated with an increased risk of EBV infection. Graft-versus-host disease (GVHD) prophylaxis with corticosteroids was a risk factor for both EBV (p = 0.013) and HCMV (p = 0.040) infections, while EBV infection (p = 0.029) was found to be an independent risk factor for HHV-6 infection. Pre-existing HHV-6 infection was associated with lower rates of HCMV infection (p = 0.002); similarly, pre-existing HCMV infection was protective against HHV-6 infection (p = 0.036).
Conclusions
HCMV-seropositive (IgG-positive/IgM-negative) HSCT recipients exhibited a high rate of herpesvirus infections, particularly EBV. ATG and male sex were strongly associated with an increased risk of EBV infection. GVHD prophylaxis with prednisone was found to affect both EBV and HCMV infections. Prior infection with EBV was shown to promote HHV-6 infection. Taken together, these data highlight the need for active monitoring of herpesvirus infections in patients undergoing HSCT.
Keywords
1. Introduction
Hematopoietic stem cell transplantation (HSCT) has proven to be an effective measure in the treatment of hematological malignancies. However, this procedure is not without significant risks, particularly that of viral infections, which remain one of the major causes of morbidity and mortality after HSCT.
1
, 2
Transplantation is often accompanied by the use of potent immunosuppressive drugs to both prevent and treat graft-versus-host disease (GVHD). The use of these drugs results in a severely compromised immune system, making HSCT patients more vulnerable to primary viral infections and reactivation.Herpesviruses are among the most common opportunistic viral infections in HSCT recipients. Of these infections, human cytomegalovirus (HCMV) pneumonia and enteritis are the most serious and often fatal complications, with a mortality rate exceeding 50% after HSCT.
3
Primary Epstein–Barr virus (EBV) infection and lymphoproliferative disorders can occur after T-cell-depleted HSCT,4
while human herpesvirus 6 (HHV-6),5
a member of the β-herpesvirus family along with HCMV, can achieve lifelong latency in the host. Reactivation of these latent infections after HSCT has been associated with a variety of symptoms including skin rash, fever, interstitial pneumonitis, bone marrow suppression, encephalitis, and GVHD.6
, 7
, 8
, 9
The vast majority of research into herpesvirus infections in HSCT recipients has focused on HCMV, with very little known regarding either EBV or HHV-6. Moreover, few studies have examined the effects of these viruses in combination, particularly in the context of HCMV-seropositive (IgG-positive/IgM-negative) HSCT recipients. In previous studies examining the relationships between the herpesviruses, β-herpesviruses were found to transactivate each other, while HCMV infection appeared to trigger HHV-6 and/or HHV-7 co-infection and vice versa.
10
However, the relationship between EBV and β-herpesvirus infections remains poorly understood. In this study, HSCT recipients who were seropositive for HCMV (IgG-positive/IgM-negative) before transplantation were examined to assess the relationships between HCMV, EBV, and HHV-6 infections after HSCT and to identify potential risk factors for viral infection.2. Methods
2.1 Human subjects and samples
HSCT recipients treated at the study hospital between January 2012 and June 2012 were tested for seropositivity (IgG and IgM) to HCMV prior to transplantation; almost all of the patients were infected with HCMV before transplantation. Following the exclusion of the few HCMV IgG-negative patients, 44 patients with IgG-positive/IgM-negative HCMV were enrolled in this study. Detailed demographic and clinical data for these patients are shown in Table 1. Plasma samples were collected once weekly in the first month, twice in the second and third months after transplantation, and then every 1–2 months until December 2012 (range 3 months to 1 year). In total, 392 peripheral blood specimens (range 5–17 samples per patient) were collected, from which peripheral blood leukocytes (PBLs) were isolated and stored at −70 °C until DNA extraction. For some patients, the number of follow-up samples was limited due to early death or loss to follow-up.
Table 1Characteristics of the study patients
| Characteristics of patients | Value |
|---|---|
| Patients, n | 44 |
| Age, years, median (range) | 26 (16–55) |
| Sex, n (%) | |
| Male | 23 (52.30%) |
| Female | 21 (47.70%) |
| Underlying disease | |
| Acute myelogenous leukemia | 19 (43.20%) |
| Acute lymphoblastic leukemia | 18 (40.90%) |
| Non-Hodgkin lymphoma | 1 (2.27%) |
| Myelodysplastic syndrome | 5 (11.36%) |
| Lymphosarcoma cell leukemia | 1 (2.27%) |
| Conditioning regimen | |
| Ara-c + BUCY + MeCCNU + ATG | 21 (47.73%) |
| Ara-C + BUCY + MeCCNU | 4 (9.09%) |
| BUCY + ATG + MeCCNU | 5 (11.36%) |
| Ara-C + BUCY + ATG | 1 (2.27%) |
| BUCY + MeCCNU | 11 (25.00%) |
| BUCY + ATG | 1 (2.27%) |
| BUCY | 1 (2.27%) |
| Type of donor | |
| HLA-identical sibling | 16 (36.36%) |
| Mismatched related donor | 14 (31.82%) |
| Matched unrelated donor | 11 (25.0%) |
| Mismatched unrelated donor | 3 (6.82%) |
| Stem cell source | |
| Peripheral blood | 42 (95.45%) |
| Peripheral blood and bone marrow | 2 (4.55%) |
| GVHD prophylaxis | |
| Mycophenolate mofetil + cyclosporine | 10 (22.73%) |
| Mycophenolate mofetil + cyclosporine + prednisone | 34 (77.27%) |
| aGVHD | |
| Grade 0–I | 36 (81.82%) |
| Grade II–IV | 8 (13.64%) |
| Death | 5 (11.36%) |
| Pulmonary fungal infection | 2 (4.55%) |
| Pulmonary hemorrhage | 1 (2.27%) |
| Hemorrhage of digestive tract | 1 (2.27%) |
| Pulmonary fungal infection and hemorrhage of digestive tract | 1 (2.27%) |
Ara-C, cytosine arabinoside; BU, busulfan; CY, cyclophosphamide; MeCCNU, methylcyclohexylnitrosamine; ATG, anti-thymocyte globulin; HLA, human leukocyte antigen; GVHD, graft-versus-host disease; aGVHD, acute graft-versus-host disease.
a Death: these deaths had no direct correlation with the viral infections.
2.2 Conditioning regimen and post-transplant treatment
HSCT recipients were treated with or without anti-thymocyte globulin (ATG) before transplantation. Patients were treated with mycophenolate mofetil plus cyclosporine in combination with short-term methotrexate and intravenous ganciclovir (5 mg/kg per day) for HCMV, for 7 days prior to transplantation. This was followed by long-term mycophenolate mofetil plus cyclosporine and prednisone, or mycophenolate mofetil plus cyclosporine for GVHD prophylaxis, sulfamethoxazole for Pneumocystis carinii pneumonia (4 tablets, twice daily), and intravenous ganciclovir for HCMV (5 mg/kg per day for the first 2 weeks) after transplantation. Acute GVHD and chronic GVHD were diagnosed and graded according to standard criteria.
11
Corticosteroids were used in patients with grade II–IV acute GVHD, with varying durations.2.3 DNA detection of herpesviruses
2.3.1 Primers and probes
Herpesvirus DNA was extracted using a commercial DNA extraction kit (Promega Biological Technology Co. Ltd, Beijing, China) in accordance with the manufacturer's instructions. The primers and probes used to detect EBV, HCMV, and HHV-6 have been described previously.
4
, 12
, 13
Briefly, PCR primers and probes for EBV were selected from BALF5,4
those for HCMV from the immediate early (IE) gene,13
and those for HHV-6 from the U31 gene.12
All primers and probes were synthesized by ZeHeng Technology (Shanghai, China).2.3.2 Quantitative fluorescence PCR assay
Quantitative fluorescence PCR was performed using a TaqMan PCR Kit (Takara, Dalian, China) and run on an ABI 7500 Real-Time PCR System (USA), as described previously.
3
Standard strains were used as positive controls in each amplification (B95-8 for EBV, AD169 for CMV, and GS for HHV-6A). In addition to a blank control, distilled water was used as a negative control. Real-time fluorescence was measured, and cycle threshold (Ct) values were calculated for each sample .Specificity was confirmed using viral DNA from standard strains. Sensitivity was confirmed by TaqMan Qualitative fluorescence PCR using serial dilutions of standard strains, with a minimum detectable Ct value of 48 relative to undiluted samples, which produced Ct values of 16. No peaks were detected in the negative control.
2.4 Statistical analyses
All statistical analyses were performed using SPSS version 16.0 (SPSS Inc., Chicago, IL, USA). Qualitative variables, such as the clinical characteristics of the HSCT recipients, were recorded as the percentage of the positive results, and differences in these variables were evaluated using the Chi-square test. Quantitative variables, such as age, were recorded as the median and range. Risk factors for EBV, HCMV, and HHV-6 were analyzed using binary logistic regression. The results were expressed as the odds ratio (OR) with corresponding 95% confidence interval (CI). A p-value of <0.05 was considered statistically significant.
3. Results
The aim was to examine HCMV, EBV, and HHV-6 viral infections, the risk factors for infection, and their relationships in HSCT recipients. The Ct value can reflect the concentration of virus. As the Ct value was considered sufficient for the purposes of this research, the quantitation of standard strains was not performed. Serial dilutions of standard strains detected in the study were used to verify the validity of PCR and the relative detection range, in order to ensure the reliability of the PCR. The aim when obtaining multiple specimens for an objective is to observe the change in viruses over a period of time. As the overall relationship of the three virus infections was analyzed in this study, the use of the median Ct value was considered sufficient for this purpose and not to have any influence on the analysis. The use of the Ct value to determine expression has been reported previously in the literature.
14
3.1 Herpesvirus infections
The first sample was collected from each patient during the first week after transplantation. These first patient samples were all PCR-negative for the viruses. Among the 44 HCMV-seropositive (IgG-positive/IgM-negative) HSCT recipients included in this study, 22 (50%) tested positive for EBV after transplantation at a median Ct value of 35.42 (range 31.04 to 38.67 cycles). The median time to EBV DNA detection was 45 days post-transplantation (range 14–88 days). Twenty patients (45.45%) tested positive for HCMV at a median Ct value of 23.90 (range 17.96 to 27.42 cycles). The median time to HCMV DNA detection was 32 days post-transplantation (range 11–76 days). Eleven patients (25%) tested positive for HHV-6 at a median Ct value of 35.00 (range 30.90–37.44 cycles). The median time to HHV-6 DNA detection was 39 days post-transplantation (range 24–87 days) (Table 2 ). Co-infections were observed in 18 patients. Ten patients (22.73%) were co-infected with EBV and HCMV, of whom five tested positive for EBV first, four for HCMV first, and one for both simultaneously. Six patients (13.64%) were co-infected with EBV and HHV-6, of whom three tested positive for EBV first, one for HHV-6 first, and two for both infections at the same time. Finally, two patients (4.55%) were co-infected with all three viruses, both of whom tested positive for HCMV, then EBV, and finally HHV-6 (Table 2).
Table 2Herpesvirus infections after HSCT
| Virus | Patients | Ct value | Time to infection, days | ||
|---|---|---|---|---|---|
| Median | Range | Median | Range | ||
| EBV | 22 (50%) | 35.42 | 31.04–38.67 | 45 | 14–88 |
| HCMV | 20 (45.45%) | 23.90 | 17.96–27.42 | 32 | 11–76 |
| HHV-6 | 11 (25%) | 35.00 | 30.90–37.44 | 39 | 24–87 |
| EBV + HCMV | 10 (22.73%) | ||||
| EBV + HHV-6 | 6 (13.64%) | ||||
| HCMV + HHV-6 | 0 (0%) | ||||
| EBV + HCMV + HHV-6 | 2 (4.55%) | ||||
HSCT, hematopoietic stem cell transplantation; Ct, cycle threshold; EBV, Epstein–Barr virus; HCMV, human cytomegalovirus; HHV-6, human herpes virus type 6.
3.2 Risk factors for EBV, HCMV, and HHV-6 infections after HSCT
Potential risk factors for EBV, HCMV, and HHV-6 infections in HSCT recipients were analyzed using binary logistic regression.
3
, 10
, 12
, 15
, 16
, 17
, 18
Male patients were 13.24 times more susceptible to EBV infection than female patients (p = 0.007). Conditioning regimens that included ATG (OR 7.690, p = 0.034) and GVHD prophylaxis regimens that included prednisone (OR 23.681, p = 0.013) were also strongly associated with an increased risk of EBV infection. Similarly, GVHD prophylaxis regimens that included prednisone (OR 13.565, p = 0.040) were also significantly associated with an increased risk of HCMV infection. EBV infection (OR 6.726, p = 0.029) was identified as an independent risk factor for HHV-6 infection (Table 3). Other potential risk factors, such as a sex mismatch between the donor and recipient, ABO blood type mismatch, human leukocyte antigen (HLA) mismatches, etc. were found not to be risk factors for EBV, HCMV, and HHV-6 infections.Table 3Binary logistic analysis for EBV, HCMV, and HHV-6 risk factors
| Virus | Factors | Coefficient (B) | OR (95% CI) | p-Value |
|---|---|---|---|---|
| EBV | Male donor | 2.583 | 13.240 (2.006–87.387) | 0.007 |
| GVHD prophylaxis including corticosteroids | 3.165 | 23.681 (1.924–291.449) | 0.013 | |
| ATG included in conditioning regimen | 2.040 | 7.690 (1.171–50.493) | 0.034 | |
| HCMV | GVHD prophylaxis including corticosteroids | 2.607 | 13.565 (1.125–163.496) | 0.040 |
| HHV-6 | EBV infection | 1.906 | 6.726 (1.213–37.303) | 0.029 |
EBV, Epstein–Barr virus; HCMV, human cytomegalovirus; HHV-6, human herpes virus type 6; OR, odds ratio; CI, confidence interval; GVHD, graft-versus-host disease; ATG, anti-thymocyte globulin.
3.3 Relationships between EBV, HCMV, and HHV-6 infections after HSCT
Prior to EBV detection, 15 patients were already infected with HCMV and six with HHV-6; seropositivity for both of these infections did not affect EBV infection (p = 0.750, p = 1.000). Among the HCMV-infected individuals, six were pre-infected with EBV and nine were pre-infected with HHV-6. EBV status did not affect the infection rate, while HHV-6 pre-infection was associated with a significantly lower rate of HCMV infection (p = 0.002). Finally, among the HHV-6-infected patients, seven were pre-infected with EBV and two with HCMV. HCMV pre-infection was also found to be a protective factor for HHV-6 infection (p = 0.036); no effect was seen for EBV. The relationships between EBV, HCMV, and HHV-6 infection rates in HSCT recipients are shown in Table 4.
Table 4Relationships of EBV, HCMV, and HHV-6 infections
| Total | EBV infection | Total | HCMV infection | Total | HHV-6 infection | ||||
|---|---|---|---|---|---|---|---|---|---|
| Number | p-Value | Number | p-Value | Number | p-Value | ||||
| Total | 44 | 22 | 44 | 20 | 44 | 11 | |||
| EBV pre-infection | 0.423 | 0.223 | |||||||
| Yes | 16 | 6 | 21 | 7 | |||||
| No | 28 | 14 | 23 | 4 | |||||
| HCMV pre-infection | 0.750 | 0.036 | |||||||
| Yes | 15 | 7 | 20 | 2 | |||||
| No | 29 | 15 | 24 | 9 | |||||
| HHV-6 pre-infection | 1.000 | 0.002 | |||||||
| Yes | 6 | 3 | 9 | 0 | |||||
| No | 41 | 19 | 35 | 20 | |||||
EBV, Epstein–Barr virus; HCMV, human cytomegalovirus; HHV-6, human herpes virus type 6.
4. Discussion
HCMV is one of the most common human pathogens, with seroprevalence ranging from 40% to 100%.
19
Despite its prevalence, little is known of its co-occurrence with other common viruses such as EBV and HHV-6, particularly in the context of HCMV-seropositive HSCT recipients. In this study, HSCT recipients who were seropositive for HCMV (IgG-positive/IgM-negative) before HSCT were examined. The rate of HCMV infection after HSCT was 45.45% (20 patients), a rate similar to that seen in previous studies.15
, 20
Immunosuppressive drug regimens put transplant recipients at a higher risk of EBV infection, which often manifests in the form of post-transplantation lymphoproliferative disease.21
In this study, EBV was detected in 22 HSCT recipients (50%), a rate similar to those in other reports.16
, 17
HHV-6 and HCMV are closely related members of the b-herpesvirus family and share many characteristics. Zerr et al. reported that more than 90% of the population are infected with HHV-6 within the first 18 months of life.
6
Among the 44 patients included in this study, 25% (11 patients) tested positive for HHV-6 DNA in their PBLs, a much lower rate than reported for the two viruses described above. These observations are similar to those of a previous report,16
although considerable variation is seen in the literature.1
, 7
, 17
When comparing the studies, it is important to note that the HSCT recipients in the present study were adults and teenagers, with most being adults (81.82%), while the previously reported HSCT recipients with higher HHV-6 infection rates were all children.1
, 7
, 17
In addition, different sample types (e.g., whole blood samples, plasma, or PBLs) and the lack of internationally standardized PCR assays are likely to account for some of the discrepancies in HHV-6 infection rates. The three herpesviruses described here were all detected within the first 3 months post-transplantation, with HCMV infection occurring first, followed by EBV and then HHV-6, a pattern consistent with those seen in previous studies.5
, 16
, 17
Reported risk factors for EBV, HCMV, and HHV-6 after HSCT include age, HLA mismatch, the presence of acute GVHD, ATG, and GVHD prophylaxis regimens containing corticosteroids.
3
, 10
, 12
, 15
, 16
, 17
, 18
In addition to these known risk factors, other potential risk factors include the sex of the recipient and donor, sex mismatch between the donor and recipient, ABO blood type mismatch, and other viral infections.It was found that GVHD prophylaxis regimens including prednisone represented an independent risk factor for HCMV infection, consistent with other studies.
3
, 15
Immunosuppressed patients exhibit delayed or reduced immune reconstitution, which has been shown to have a direct effect on viral replication dynamics in vivo;22
this effect may in turn affect HCMV replication. Close monitoring for HCMV is therefore extremely important in patients whose immunosuppression therapy includes corticosteroids.In this study, the use of ATG in the conditioning regimen and GVHD prophylaxis regimens containing corticosteroids were associated with significant increases in EBV infection post-transplantation, with patients 7.7- to 23.7-times more likely to become infected; this is similar to the findings of previous studies.
12
, 16
, 17
, 18
This effect is likely due to the action of ATG on cellular immunity. As more than 90% of adults have been infected with EBV, exposure to the virus is inevitable. After infection, EBV persists within the body in resting memory B-cells, with cellular immune responses controlling proliferating EBV-infected B-cells. High-level immunosuppression, as achieved with ATG plus high-dose corticosteroids, affects both the number and function of T-cells to the point where existing T-cells may be unable to control EBV proliferation, whether due to primary infection or reactivation.17
This model is also supported by the well-established mechanism of action of ATG in terms of in vivo partial T-cell depletion.18
, 23
The sex of the donor was also found to be a significant risk factor for EBV infection, although the specific reasons underlying this effect remain unknown.GVHD, the administration of steroids for GVHD, and allele mismatched donors have previously been associated with an increased risk of active HHV-6 infection,
7
, 10
although these findings were not confirmed in the present study. However, a surprising finding was that EBV pre-infection facilitated HHV-6 infection thereafter (Table 3). This association may be due to impaired T-cell immunity stemming from the GVHD prophylaxis regimen, resulting in an immune system unable to suppress EBV reactivation.17
EBV proliferation would further suppress T-lymphocyte function and/or exhaust T-cells, enabling opportunistic infections such as HHV-6. Alternatively, EBV proliferation may induce the synthesis of proinflammatory cytokines and suppress HHV-6-specific lymphoproliferative responses, triggering HHV-6 primary infection followed by proliferation and reactivation.Different studies may identify different risk factors depending on the target population, methods and samples used, etc. The risk factors identified in the present study are just possibilities. However, as potential risk factors, they are worthy of attention.
Despite the apparent associations observed between viral infections, it is difficult to determine whether these co-infections represent new or reactivated infections, and what effects these viruses may have on each other in vivo. Growing evidence suggests that the β-herpesviruses are able to reversely activate other β-herpesviruses due to their effects on immune regulation.
10
, 24
, 25
, 26
, 27
, 28
, 29
However, Tormo et al. have argued against a role for HHV-6 in promoting HCMV replication by inhibiting the reconstitution of HCMV-specific T-cell immunity, which is consistent with the present findings.10
Here, both HCMV and HHV-6 were found to decrease susceptibility to the other virus. While the exact mechanism remains unknown, it has been suggested that virus-specific IgG raised against one virus may confer cross-immunity to the other, thereby minimizing further infection. Alternatively, due to the strong homology between HCMV and HHV-6, prior infection may confer resistance due to competition for shared replication machinery. Further research will be necessary to validate these hypotheses.Few studies have examined the relationship between β-herpesviruses and EBV. Aalto et al.
30
and Razonable et al.31
have suggested that HCMV infection may induce EBV infection and proliferation. In this study, no relationship was found between HCMV and EBV, or between HHV-6 and EBV, as analyzed by Chi-square test (Table 4). However, EBV pre-infection was found to be an independent risk factor for HHV-6 infection on binary logistic regression analysis (Table 3). The exact pathophysiological basis underlying this interaction is largely unknown, although it remains possible that the immunosuppressive effects of the EBV system may facilitate other infections such as HHV-6. Further research will be necessary to validate this hypothesis.Taken together, the data presented here reveal a frequent co-occurrence of EBV, HCMV, and HHV-6 in HCMV-seropositive (IgG-positive/IgM-negative) HSCT recipients, with EBV being the most common. Furthermore, these results confirm the strong association between T-cell depletion, male sex, and EBV reactivation. GVHD prophylaxis regimens containing corticosteroids were identified as a risk factor for both EBV and HCMV infections, with each of the three viruses exhibiting some form of relationship. HCMV and HHV-6 appear to serve as protective factors preventing further infection, while EBV helps facilitate HHV-6 infection.
Some encouraging results were obtained and conclusions drawn from this study, but there are some inevitable limitations. First, the herpesvirus family includes a variety of viruses: herpes simplex virus (HSV)-1, HSV-2, varicella zoster virus (VZV), HCMV, EBV, HHV-6, HHV-7, and HHV-8. Unfortunately only three viruses were investigated in this study (HCMV, EBV, and HHV-6). However, this study will form part of a series of future studies on herpesviruses, which will be performed step by step. A second limitation was the use of Ct values; however, these were considered sufficiently accurate for the purposes of this study and not to have any influence on the analysis. Nevertheless it would be better to report the number of copies of viral DNA to demonstrate the change in virus infection. Third, the aim of this study was to investigate virus infections in HSCT recipients who were HCMV-seropositive (IgG-positive/IgM-negative) before transplantation, while EBV and HHV-6 were not detected before transplantation. This would not, therefore, allow us to determine whether the infection that occurred later was a consequence of reactivation or a primary infection. This should be clarified in future studies. Finally, the rate of HHV-6 infection is higher in children than in adults.
1
, 7
, 17
Whether younger adults have a higher rate of infection should also be studied in the future.Acknowledgements
This study was supported by the Medical Science and Technology Project of Zhejiang Province (2013KYB084), the National Natural Science Foundation of China (30872239), the Zhejiang Provincial Natural Science Foundation of China (LY14H190002), and the Independent Research Topics of State key Laboratory for Diagnosis and Treatment of Infectious Diseases.
Ethical approval: This study was approved by the Ethics Committee of the First Affiliated Hospital of Zhejiang University. Informed consent was obtained from the patients.
Conflict of interest: None.
Contributions: Study design: Jianhua Hu, Jun Fan, Weihang Ma; performance of the experiments: Min Jing, Jun Fan, Yaping Huang, Rong Yang; provision of patients: Meifang Yang, Xuan Zhang, Hong Zhao, Hainv Gao; data collection: Lichen Xu, Hanying Liang, Genyong Gui, Huiqi Wang, Shengnan Gong, Jindong Wang; data analysis: Jianhua Hu, Min Jing, Meifang Yang, Huihui Dong; writing of the paper: Jun Fan.
References
- Human herpes virus 6 plasma DNA positivity after hematopoietic stem cell transplantation in children: an important risk factor for clinical outcome.Biol Blood Marrow Transplant. 2008; 14: 831-839
- Activity of broad-spectrum T cells as treatment for AdV, EBV, CMV, BKV, and HHV6 infections after HSCT.Sci Transl Med. 2014; 6: 242ra83
- Cytomegalovirus in hematopoietic stem cell transplant recipients.Infect Dis Clin North Am. 2010; 24: 319-337
- DNA sequence and expression of the B95-8 Epstein–Barr virus genome.Nature. 1984; 310: 207-211
- Monitoring of human herpesviruses after allogeneic peripheral blood stem cell transplantation and bone marrow transplantation.Br J Haematol. 1999; 105: 295-302
- A population-based study of primary human herpesvirus 6 infection.N Engl J Med. 2005; 352: 768-776
- Human herpesvirus 6 DNA in plasma after allogeneic stem cell transplantation: incidence and clinical significance.J Infect Dis. 2006; 193: 68-79
- Early human herpesvirus type 6 reactivation after allogeneic stem cell transplantation: a large-scale clinical study.Biol Blood Marrow Transplant. 2012; 18: 1080-1089
- Human herpesvirus 6 reactivation on the 30th day after allogeneic hematopoietic stem cell transplantation can predict grade 2-4 acute graft-versus-host disease.Transpl Infect Dis. 2014; 16: 440-449
- An assessment of the effect of human herpesvirus-6 replication on active cytomegalovirus infection after allogeneic stem cell transplantation.Biol Blood Marrow Transplant. 2009; 16: 653-661
- 1994 Consensus Conference on Acute GVHD Grading.Bone Marrow Transplant. 1995; 15: 825-828
- Simultaneous quantification of Epstein–Barr virus, cytomegalovirus, and human herpesvirus 6 DNA in samples from transplant recipients by multiplex real-time PCR assay.J Clin Microbiol. 2007; 45: 1426-1432
- The structure of the major immediate early gene of human cytomegalovirus strain AD169.Virus Res. 1985; 2: 107-121
- Correlation of real time PCR cycle threshold cut-off with Bordetella pertussis clinical severity.PLoS One. 2015; 10: e0133209
- Cytomegalovirus infection and disease after allogeneic hematopoietic stem cell transplantation: experience in a center with a high seroprevalence of both CMV and hepatitis B virus.Ann Hematol. 2011; 91: 587-595
- Opportunistic virus DNA levels after pediatric stem cell transplantation: serostatus matching, anti-thymocyte globulin, and total body irradiation are additive risk factors.Transpl Infect Dis. 2011; 13: 122-130
- Prospective, comprehensive, and effective viral monitoring in children undergoing allogeneic hematopoietic stem cell transplantation.Biol Blood Marrow Transplant. 2010; 16: 1428-1435
- Features of Epstein–Barr virus (EBV) reactivation after reduced intensity conditioning allogeneic hematopoietic stem cell transplantation.Leukemia. 2011; 25: 932-938
- Antiviral strategies to combat cytomegalovirus infections in transplant recipients.Curr Opin Pharmacol. 2008; 8: 541-548
- Cytomegalovirus in hematopoietic stem cell transplant recipients: current status, known challenges, and future strategies.Biol Blood Marrow Transplant. 2003; 9: 543-558
- Expression of Epstein–Barr virus transformation-associated genes in tissues of patients with EBV lymphoproliferative disease.N Engl J Med. 1989; 321: 1080-1085
- Application of viral-load kinetics to identify patients who develop cytomegalovirus disease after transplantation.Lancet. 2000; 355: 2032-2036
- Epstein–Barr virus reactivation in allogeneic stem cell transplantation is highly related to cytomegalovirus reactivation.Clin Transplant. 2013; 27: E491-E497
- CMV infection is usually associated with concurrent HHV-6 and HHV-7 antigenemia in liver transplant patients.J Clin Virol. 2002; 25: S57-S61
- Human herpesvirus-6 DNAemia is a sign of impending primary CMV infection in CMV sero-discordant renal transplantations.J Clin Virol. 2013; 58: 422-426
- Human herpesvirus 6 infection and cytomegalovirus-specific lymphoproliferative responses in allogeneic stem cell transplant recipients.Bone Marrow Transplant. 2002; 30: 521-526
- Detection of simultaneous beta-herpesvirus infections in clinical syndromes due to defined cytomegalovirus infection.Clin Transplant. 2003; 17: 114-120
- Tissue HHV6 and 7 determination in pediatric solid organ recipients—a pilot study.Pediatr Transplant. 2003; 7: 458-463
- Human beta-herpesvirus interactions in solid organ transplant recipients.J Infect Dis. 2001; 183: 179-184
- Immunoreactivation of Epstein–Barr virus due to cytomegalovirus primary infection.J Med Virol. 1998; 56: 186-191
- Herpesvirus infections in solid organ transplant patients at high risk of primary cytomegalovirus disease.J Infect Dis. 2005; 192: 1331-1339
Article info
Publication history
Published online: April 04, 2016
Accepted:
March 30,
2016
Received in revised form:
March 8,
2016
Received:
January 6,
2016
Corresponding Editor: Eskild Petersen, Aarhus, Denmark.Identification
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