Seroconversion to human herpesvirus 6 following liver transplantation is a marker of cytomegalovirus disease

Cytokine Dynamics and Herpesvirus Interactions in Pediatric Liver and Kidney Transplant Recipients: The Distinct Behavior of HCMV, HHV6, HHV7 and EBV

Pediatric solid organ transplant (SOT) recipients face a challenging balance between immunosuppression and graft rejection. While Epstein-Barr Virus (EBV) and cytomegalovirus (HCMV) are known contributors to post-transplant lymphoproliferative disease and graft rejection, respectively, the roles of herpesvirus 6 and 7 (HHV6 and HHV7) and the impact of these herpesviruses on cytokine levels remain unclear, leading to gaps in clinical practice. In this associative study, we measured 17 cytokines using a Bio-Plex assay in a meticulously curated plasma sample pool (N = 158) from pediatric kidney and liver transplant recipients over a one-year follow-up period. The samples included virus-negative and virus-positive cases, either individually or in combination, along with episodes of graft rejection. We observed that the elevation of IL-4, IL-8, and IL-10 correlated with graft rejection. These cytokines were elevated in samples where HCMV or HHV6 were detected alone or where EBV and HHV7 were co-detected. Interestingly, latent EBV, when detected independently, exhibited an immunomodulatory effect by downregulating cytokine levels. However, in co-detection scenarios with β-herpesviruses, EBV transitioned to a lytic state, also associating with heightened cytokinemia and graft rejection. These findings highlight the complex interactions between the immune response and herpesviruses in transplant recipients. The study advocates for enhanced monitoring of not only EBV and HCMV but also HHV6 and HHV7, providing valuable insights for improved risk assessment and targeted interventions in pediatric SOT recipients.

Risk factors and outcome of concurrent and sequential multiviral cytomegalovirus, Epstein-Barr virus, BK virus, adenovirus and other viral reactivations in transplantation

PURPOSE OF REVIEW

Reactivation of viral infections occurs frequently in immunosuppressed populations, particularly in solid organ (SOT) or allogeneic haematopoietic cell (HCT) transplant patients. Concurrent and sequential multivirus infections are common, yet risk factors and outcomes remain unclear. This review aims to identify the patients vulnerable to multivirus infections and characterize the impact of increased viral burden to formulate prevention and treatment strategies.

RECENT FINDINGS

Incidences of up to 89% in SOT and 36% in HCT have been reported for two viruses, and 32% in SOT and 28% in HCT for at least three viruses. Risk factors appear related to an increased burden of immunosuppression, with most viral coinfections occurring within 12 months of transplantation. Direct viral complications such as cytomegalovirus disease are more frequent in coinfected patients, with documented prolonged duration of viraemia, higher viral load and increased end-organ disease. Graft dysfunction, acute rejection and graft-vs.-host disease (GVHD) have also been associated. Increased mortality is reported in the HCT population.

SUMMARY

Multivirus infections occur in a significant proportion of transplant patients and is linked to immunosuppressive burden. There is increasing evidence that this leads to worse graft and patient outcomes. Further prospective studies are required to further comprehensively characterise viral epidemiology, mechanisms and treatment strategies to ameliorate this risk.

The Contribution of Human Herpes Viruses to γδ T Cell Mobilisation in Co-Infections

γδ T cells are activated in viral, bacterial and parasitic infections. Among viruses that promote γδ T cell mobilisation in humans, herpes viruses (HHVs) occupy a particular place since they infect the majority of the human population and persist indefinitely in the organism in a latent state. Thus, other infections should, in most instances, be considered co-infections, and the reactivation of HHV is a serious confounding factor in attributing γδ T cell alterations to a particular pathogen in human diseases. We review here the literature data on γδ T cell mobilisation in HHV infections and co-infections, and discuss the possible contribution of HHVs to γδ alterations observed in various infectious settings. As multiple infections seemingly mobilise overlapping γδ subsets, we also address the concept of possible cross-protection.

The Impact of Infection on Chronic Allograft Dysfunction and Allograft Survival After Solid Organ Transplantation

Infectious diseases after solid organ transplantation (SOT) are a significant cause of morbidity and reduced allograft and patient survival; however, the influence of infection on the development of chronic allograft dysfunction has not been completely delineated. Some viral infections appear to affect allograft function by both inducing direct tissue damage and immunologically related injury, including acute rejection. In particular, this has been observed for cytomegalovirus (CMV) infection in all SOT recipients and for BK virus infection in kidney transplant recipients, for community-acquired respiratory viruses in lung transplant recipients, and for hepatitis C virus in liver transplant recipients. The impact of bacterial and fungal infections is less clear, but bacterial urinary tract infections and respiratory tract colonization by Pseudomonas aeruginosa and Aspergillus spp appear to be correlated with higher rates of chronic allograft dysfunction in kidney and lung transplant recipients, respectively. Evidence supports the beneficial effects of the use of antiviral prophylaxis for CMV in improving allograft function and survival in SOT recipients. Nevertheless, there is still a need for prospective interventional trials assessing the potential effects of preventive and therapeutic strategies against bacterial and fungal infection for reducing or delaying the development of chronic allograft dysfunction.

Strategies for the prevention of infection after solid organ transplantation

Infection is a frequent complication of organ transplantation and is associated with significant morbidity and mortality. Preventative antimicrobial strategies are a key component of the care received by transplant patients. This review summarizes the evidence supporting anti-infective prophylaxis in this setting. Specific recommendations for the prevention of bacterial, fungal, viral and parasitic infection after transplant are made, with a focus on recent developments in the field of transplant infectious diseases.

Human herpesviruses 6, 7 and 8 in solid organ transplant recipients

Human herpesviruses (HHV) 6 and 7 are ubiquitous infections that reactivate commonly in transplant recipients. However, clinical diseases due to these viruses are reported only in 1% of solid organ transplant recipients. Fever, rash and bone marrow suppression are the most common manifestations, but symptoms of tissue invasive disease may be observed. Treatment of HHV-6 and HHV-7 disease includes antiviral therapy and cautious reduction in immunosuppression. HHV-8 is an oncogenic gamma-herpesvirus that causes Kaposi's sarcoma, Castleman's disease and primary effusion lymphomas in transplant recipients. Nonmalignant diseases such as bone marrow suppression and multiorgan failure have also been associated with HHV-8. Reduction in immunosuppression is the first line treatment of HHV-8 infection. Other alternatives for treatment, especially for HHV-8 diseases not responsive to immuno-minimization strategies, are surgery and chemotherapy. Sirolimus has been shown to be a beneficial component for the treatment of Kaposi's sarcoma and the role of antivirals for HHV-8 infection is being investigated.

Human herpesvirus-6 infections in kidney, liver, lung, and heart transplantation: review

Human herpesvirus-6 (HHV-6), which comprises of HHV-6A and HHV-6B, is a common infection after solid organ transplantation. The rate of HHV-6 reactivation is high, although clinical disease is not common. Only 1% of transplant recipients will develop clinical illness associated with HHV-6 infection, and most are ascribable to HHV-6B. Fever, myelosuppression, and end-organ disease, including hepatitis and encephalitis, have been reported. HHV-6 has also been associated with various indirect effects, including a higher rate of CMV disease, acute and chronic graft rejection, and opportunistic infection such as invasive fungal disease. All-cause mortality is increased in solid organ transplant recipients with HHV-6 infection. HHV-6 is somewhat unique among human viruses because of its ability to integrate into the host chromosome. The clinical significance of chromosomally integrated HHV-6 is not yet defined, although a higher rate of bacterial infection and allograft rejection has been suggested. The diagnosis of HHV-6 is now commonly made using nucleic acid testing for HHV-6 DNA in clinical samples, but this can be difficult to interpret owing to the common nature of asymptomatic viral reactivation. Treatment of HHV-6 is indicated in established end-organ disease such as encephalitis. Foscarnet, ganciclovir, and cidofovir have been used for treatment.

Human Herpesvirus 6 Infection in Hemodialysis and Peritoneal Dialysis Patients

Background

Human herpesvirus 6 (HHV-6) infection occurs worldwide and can be reactivated from latency during periods of immunosuppression, especially after organ transplantation. No previous study has evaluated the influence of dialysis type on HHV-6 infection. The aim of the present study was to determine the prevalence of HHV-6 antibodies in hemodialysis (HD) and peritoneal dialysis (PD) patients.

Methods

W e studied 36 PD patients, 35 HD patients, and 20 healthy subjects, all with no history of organ transplantation. After systematic inquiries and a physical examination, blood was drawn for determination of biochemical parameters, cytomegalovirus immunoglobulin M (IgM) and immunoglobulin G (IgG), hepatitis B surface antigen, and the hepatitis C and human immunodeficiency virus antibodies. Titers of HHV-6 IgM and IgG antibodies were determined by ELISA.

Results

Titers for HHV-6 IgM antibody were positive in 9 HD patients (25.7%), 8 PD patients (22.2%), and 2 control subjects (10.0%, p > 0.05). More HD patients (20.0%) than PD patients (5.6%, p = 0.07) or control subjects (0.0%, p =0.03) were positive for HHV-6 IgG antibody. In HD patients, HHV-6 IgG seropositivity and duration of dialysis were positively correlated (R = 0.33, p = 0.05).

Conclusions

Infection with HHV-6 is not rare in PD and HD patients. In addition, HHV-6 IgG seropositivity was significantly higher in H D patients than in control subjects and approached significance when compared with seropositivity in PD patients. Moreover, in HD patients, HHV-6 IgG seropositivity correlated with duration on HD. These preliminary findings provide insight into the pre-transplantation period for patients and may aid our understanding of how to best protect patients against HHV-6 after transplantation.

Herpes viruses in transplant recipients: HSV, VZV, human herpes viruses, and EBV

The herpes viruses are responsible for a wide range of diseases in patients following transplant, resulting from direct viral effects and indirect effects, including tumor promotion. Effective treatments and prophylaxis exist for the neurotropic herpes viruses HSV-1, HSV-2, varicella zoster virus, and possibly HHV-6. Antivirals seem to be less effective at prevention of the tumor-promoting effects of Epstein-Barr virus and HHV-8. Reduction in immunosuppression is the cornerstone to treatment of many diseases associated with herpes virus infections.

Human herpesvirus 6-related pure red cell aplasia, secondary graft failure, and clinical severe immune suppression after allogeneic hematopoietic cell transplantation successfully treated with foscarnet

Human herpesvirus 6 (HHV-6) is frequently detected after allogeneic hematopoietic cell transplantation (allo-HCT); however, the clinical interpretation of HHV-6 viremia in a transplant patient is challenging as it may signify asymptomatic reactivation, chromosomal integration of the virus genome in the donor or recipient with no clinical significance, or severe HHV-6 disease. Here we present a case of HHV-6 disease after allo-HCT presenting as pure red cell aplasia, secondary graft failure, and severe immunosuppression causing multiple severe bacterial super-infections. Examination of pre-transplant patient and donor samples as well as serial determination of HHV-6 DNA copy numbers after transplantation were necessary to definitively interpret HHV-6 viremia as active HHV-6 infection with a causative role in pancytopenia and immune suppression. Foscarnet treatment resulted both in viral load decline and disappearance of HHV-6-related bone marrow suppression and predisposition to severe infections. Clinicians should be aware of the wide array of clinical manifestations and the diagnostic pitfalls of post-transplant HHV-6 disease. These issues are extremely challenging, as they may result either in dangerous underestimation of HHV-6 disease or in the institution of unnecessary antiviral therapy. Late bone marrow aplasia and late severe infections after allo-HCT without other obvious causes may be HHV-6 related.

Current concepts on cytomegalovirus infection after liver transplantation

Cytomegalovirus (CMV) is the most common viral pathogen that negatively impacts on the outcome of liver transplantation. CMV cause febrile illness often accompanied by bone marrow suppression, and in some cases, invades tissues including the transplanted allograft. In addition, CMV has been significantly associated with an increased predisposition to allograft rejection, accelerated hepatitis C recurrence, and other opportunistic infections, as well as reduced overall patient and allograft survival. To negate the adverse effects of CMV on outcome, its prevention, whether through antiviral prophylaxis or preemptive therapy, is regarded as an essential component to the medical management of liver transplant patients. Two recent guidelines have suggested that antiviral prophylaxis or preemptive therapy are similarly effective in preventing CMV disease in modest-risk CMV-seropositive liver transplant recipients, while antiviral prophylaxis is the preferred strategy over preemptive therapy for the prevention of CMV disease in high-risk recipients [CMV-seronegative recipients of liver allografts from CMV-seropositive donors (D+/R-)]. However, antiviral prophylaxis has only delayed the onset of CMV disease in many CMV D+/R- liver transplant recipients, and at least in one study, such occurrence of late-onset primary CMV disease was significantly associated with increased mortality after liver transplantation. Therefore, optimized strategies for prevention are needed, and aggressive treatment of CMV infection and disease should be pursued. The standard treatment of CMV disease consists of intravenous ganciclovir or oral valganciclovir, and if feasible, one should also reduce the degree of immunosuppression. In one recent controlled clinical trial, valganciclovir was found to be as effective and safe as intravenous ganciclovir for the treatment of mild to moderate CMV disease in solid organ (including liver) transplant recipients. In this article, the authors review the current state and the future perspectives of prevention and treatment of CMV disease after liver transplantation.

An assessment of the effect of human herpesvirus-6 replication on active cytomegalovirus infection after allogeneic stem cell transplantation

Human herpesvirus-6 (HHV-6) may enhance cytomegalovirus (CMV) replication in allogeneic stem cell transplant (allo-SCT) recipients either through direct or indirect mechanisms. Definitive evidence supporting this hypothesis are lacking. We investigated the effect of HHV-6 replication on active CMV infection in 68 allo-SCT recipients. Analysis of plasma HHV-6 and CMV DNAemia was performed by real-time PCR. Enumeration of pp65 and IE-1 CMV-specific IFNgamma CD8(+) and CD4(+)T cells was performed by intracellular cytokine staining. HHV-6 DNAemia occurred in 39.8% of patients, and was significantly associated with subsequent CMV DNAemia in univariate (P=.01), but not in multivariate analysis (P=.65). The peak of HHV-6 DNAemia was not predictive of the development of CMV DNAemia. Timing and kinetics of active CMV infection were comparable in patients either with or without a preceding episode of HHV-6 DNAemia. The occurrence of HHV-6 DNAemia had no impact on CMV-specific T cell immunity reconstitution early after transplant. The receipt of a graft from an HLA-mismatched donor was independently associated with HHV-6 (P=.009) and CMV reactivation (P=.04). The data favor the hypothesis that a state of severe immunosuppression leads to HHV-6 and CMV coactivation, but argue against a role of HHV-6 in predisposing to the development of CMV DNAemia or influencing the course of active CMV infection.

Cytomegalovirus infection in critically ill patients: a systematic review

INTRODUCTION

The precise role of cytomegalovirus (CMV) infection in contributing to outcomes in critically ill immunocompetent patients has not been fully defined.

METHODS

Studies in which critically ill immunocompetent adults were monitored for CMV infection in the intensive care unit (ICU) were reviewed.

RESULTS

CMV infection occurs in 0 to 36% of critically ill patients, mostly between 4 and 12 days after ICU admission. Potential risk factors for CMV infection include sepsis, requirement of mechanical ventilation, and transfusions. Prolonged mechanical ventilation (21 to 39 days vs. 13 to 24 days) and duration of ICU stay (33 to 69 days vs. 22 to 48 days) correlated significantly with a higher risk of CMV infection. Mortality rates in patients with CMV infection were higher in some but not all studies. Whether CMV produces febrile syndrome or end-organ disease directly in these patients is not known.

CONCLUSIONS

CMV infection frequently occurs in critically ill immunocompetent patients and may be associated with poor outcomes. Further studies are warranted to identify subsets of patients who are likely to develop CMV infection and to determine the impact of antiviral agents on clinically meaningful outcomes in these patients.

Immunobiology of human cytomegalovirus: from bench to bedside

SUMMARY

Following primary infection, human cytomegalovirus (HCMV) establishes lifelong latency and periodically reactivates without causing symptoms in healthy individuals. In the absence of an adequate host-derived immune response, this fine balance of permitting viral reactivation without causing pathogenesis is disrupted, and HCMV can subsequently cause invasive disease and an array of damaging indirect immunological effects. Over the last decade, our knowledge of the immune response to HCMV infection in healthy virus carriers and diseased individuals has allowed us to translate these findings to develop better diagnostic tools and therapeutic strategies. The application of these emerging technologies in the clinical setting is likely to provide opportunities for better management of patients with HCMV-associated diseases.

Cytomegalovirus infection after liver transplantation: Current concepts and challenges

Cytomegalovirus (CMV) is a common viral pathogen that influences the outcome of liver transplantation. In addition to the direct effects of CMV syndrome and tissue-invasive diseases, CMV is associated with an increased predisposition to acute and chronic allograft rejection, accelerated hepatitis C recurrence, and other opportunistic infections, as well as reduced overall patient and allograft survival. Risk factors for CMV disease are often interrelated, and include CMV D+/R- serostatus, acute rejection, female gender, age, use of high-dose mycophenolate mofetil and prednisone, and the overall state of immunity. In addition to the role of CMV-specific CD4+ and CD8+ T lymphocytes, there are data to suggest that functionality of the innate immune system contributes to CMV disease pathogenesis. In one study, liver transplant recipients with a specific polymorphism in innate immune molecules known as Toll-like receptors were more likely to develop higher levels of CMV replication and clinical disease. Because of the direct and indirect adverse effects of CMV disease, its prevention, whether through antiviral prophylaxis or preemptive therapy, is an essential component in improving the outcome of liver transplantation. In the majority of transplant centers, antiviral prophylaxis is the preferred strategy over preemptive therapy for the prevention of CMV disease in CMV-seronegative recipients of liver allografts from CMV-seropositive donors (D+/R-). However, the major drawback of antiviral prophylaxis is the occurrence of delayed-onset primary CMV disease. In several prospective and retrospective studies, the incidence of delayed-onset primary CMV disease ranged from 16% to 47% of CMV D+/R- liver transplant recipients. Current data suggests that delayed-onset CMV disease is associated with increased mortality after liver transplantation. Therefore, optimized strategies for prevention and novel drugs with unique modes of action are needed. Currently, a randomized controlled clinical trial is being performed comparing the efficacy and safety of maribavir, a novel benzimidazole riboside, and oral ganciclovir as prophylaxis against primary CMV disease in liver transplant recipients. The treatment of CMV disease consists mainly of intravenous (IV) ganciclovir, and if feasible, a reduction in the degree of immunosuppression. A recent controlled clinical trial demonstrated that valganciclovir is as effective and safe as IV ganciclovir for the treatment of CMV disease in solid organ (including liver) transplant recipients. In this article, the author reviews the current state and the future perspectives of prevention and treatment of CMV disease after liver transplantation.

Human herpesvirus 6 infection in adult living related liver transplant recipients

To analyze human herpesvirus 6 (HHV-6) infection in adult living related liver transplantation, we performed a virological analysis, including viral isolation, serological assay, and real-time polymerase chain reaction, of serially collected blood samples from 67 recipients. In addition, cytokine levels were measured to determine their role in viral reactivation. HHV-6 was isolated from only 4 recipients (6.0%), and viral DNA was detected in 15 (22.4%) of the 67 recipients. A significant increase in HHV-6 immunoglobulin G antibody titers was observed in 19 (28.4%) of the 67 recipients. Finally, 26 recipients (38.8%) had HHV-6 reactivation 2-6 weeks after transplantation. HHV-6 associated clinical features were analyzed in the 17 recipients presenting with either viremia or DNAemia. Two recipients with viremia and 3 recipients with DNAemia had unexplained fever at the time of viral infection. An increase in aminotransferase levels was observed in 2 recipients with viremia and 3 recipients with DNAemia. Recipients with liver cirrhosis caused by hepatitis B virus or hepatitis C virus infection as the underlying disease were more likely to have HHV-6 infection (P = 0.025). Mortality at the last follow-up in recipients with HHV-6 reactivation was significantly higher than in those without viral reactivation (P = 0.0118). Plasma interleukin-6 levels were significantly higher in the recipients with HHV-6 viremia than in the recipients without viremia at 4 weeks post-transplant (P = 0.0411). Moreover, tumor necrosis factor alpha levels were also higher in recipients with HHV-6 viremia (P < 0.0001) or reactivation (P = 0.0011) than in recipients without viremia or reactivation 4 weeks post-transplant.

Infecciones en los pacientes trasplantados de hígado

Infection is the main cause of morbidity and mortality in liver transplant patients. Infections appear in three different periods following transplantation and are related to surgical factors, the degree of immunosuppression, environmental exposure and the type of prophylaxis used. Bacterial infections occur in the first two months after transplantation as bacteremia, surgical wound and intra-abdominal infection, or pneumonia. Tuberculosis in the liver transplant recipient is more aggressive than in immunocompetent persons. Viruses produce direct infection in these patients; moreover, some viruses (e.g., cytomegalovirus and human herpes virus 6) are immunomodulators and can facilitate other infections and graft rejection. Polymerase chain reaction and antigenemia techniques have made possible prompt diagnosis of cytomegalovirus infection and the implementation of prophylactic strategies. Fungal infections still have a high associated mortality rate, despite new diagnostic techniques and new antifungal drugs.

Human herpesvirus 6 reactivation in trichloroethylene-exposed workers suffering from generalized skin disorders accompanied by hepatic dysfunction

Idiosyncratic generalized skin disorders resembling serious drug hypersensitivities have reportedly occurred after occupational exposure to trichloroethylene. However, factors associated with the disorders remain unknown except for trichloroethylene exposure. This study aimed at clarifying whether infectious diseases contributed to the development of rash or hepatitis in patients with trichloroethylene-related generalized skin disorders. Fifty-nine patients consecutively hospitalized between March 2002 and December 2003 and 59 healthy exposed workers selected on an age-matched basis in the patients' factories were enrolled in the study. Information on possible risk factors for rash and hepatitis was collected with structured checklists. Antibody titers were measured for hepatitis A, B and C viruses, Mycoplasma pneumoniae, herpes simplex viruses 1 and 2, Epstein-Barr virus, cytomegalovirus, human herpesvirus 6, measles and rubella virus. Thirty-six cases (59%) showed exfoliative dermatitis, 17 (28%) erythema multiforme, 4 (7%) Stevens-Johnson syndrome, and 4 (7%) toxic epidermal necrolysis. Before the onset of rash, 16 (27%) cases had received medication prescribed for the preceding fever, a main first symptom of the disorders. Marked increases in anti-human herpesvirus 6 IgG titer (> or =256), which indicated viral reactivation, were noted in 14 (25%) patients, while no abnormal increase was detected in the controls (p<0.001). Anti-measles IgM titer was positive in 2 (7%) cases but not in the controls (p=0.49). The involvement of other known risk factors of rash or hepatitis was ruled out. These results suggest that part of trichloroethylene-related generalized cutaneous disorders occurring in China and drug-induced hypersensitivity syndrome overlap in terms of human herpesvirus 6 reactivation.

Human herpesvirus-6 infection in solid organ and stem cell transplant recipients

HHV-6 has in recent years become recognized as a potential significant pathogen in both solid organ and stem cell transplant recipients. HHV-6 infections are common after transplantation regardless of the utilized diagnostic technique. Several different clinical manifestations have been described including fever, bone marrow suppression, encephalitis, skin rash, and hepatitis. The most important end-organ disease is encephalitis in stem cell transplant recipients that has been reported to have a mortality of at least 40%. HHV-6 is also considered an immunomodulatory and immunosuppressive virus that may facilitate super-infections with other opportunistic pathogens such as CMV and fungal infections and thereby contribute to overall mortality. No established therapy exists but both ganciclovir and foscarnet have been reported to have in vitro and in vivo efficacy against HHV-6.

Emerging viral infections in transplantation

Viral infections are an important complication of transplantation. The introduction of more potent immunosuppressive agents over the past decade correlates with an increase in the rate of hospitalizations of transplant patients with infections. Specifically, viral infections have emerged as a major source of morbidity and mortality in transplantation. There are several potential intervention strategies in the face of emerging infections and it is likely that the approach will differ depending on the virus in question. These include viral surveillance and pre-emptive therapy, intervention of the transplant community, and policy change at the level of government, blood bank and organ procurement organizations. This review focuses on the emergence of the herpesviruses; HHV-6 and HHV-7. In addition, the issue of virus transmission through organ transplant is addressed with a discussion of West Nile virus and the rabies virus.

A prospective survey of human herpesvirus-6 primary infection in solid organ transplant recipients

Human herpesvirus 6 (HHV-6) infection is potentially life-threatening to immunosuppressed patients. There is a lack of information regarding the risk and the clinical manifestations of primary HHV-6 infection in solid-organ transplant recipients. We prospectively evaluated patients undergoing solid organ transplantation with negative immunoglobulin (Ig) G antibodies against HHV-6 by means of HHV-6 quantitative polymerase chain reaction. Among 193 recipients, seven were HHV-6 seronegative (prevalence 3.6%). We detected a positive HHV-6 viral load in only one patient, and four patients seroconverted after one year posttransplantation. The patient with a positive HHV-6 viral load developed cholestatic hepatitis without fever and did not experience severe end-organ disease. In conclusion, our findings show a low incidence of symptomatic primary HHV-6 infection among seronegative solid-organ transplant recipients.

Infections in solid organ transplant recipients

A disturbing trend in evolution for sometime has culminated in the fact that resistant Gram-positive bacteria including enterococci and staphylococci have emerged as the leading pathogens at many transplant centers. Recently published reports have highlighted the formidable challenge such antimicrobial-resistant microorganisms now pose in transplant recipients. Studies published within the past year have documented the clinical relevance of human herpesvirus-6 after transplantation, as well as the transmission of human herpesvirus-8 by transplanted allograft and the subsequent development of Kaposi's sarcoma in these patients. A novel hepatitis virus has been discovered; studies to elucidate its significance in the transplant setting are underway.

HHV-6 and HHV-7 antigenemia related to CMV infection after liver transplantation

BACKGROUND

Betaherpesviruses human herpesvirus-6 and -7 (HHV-6, HHV-7), which are closely related to cytomegalovirus (CMV), have been reported in transplant patients. In this retrospective study, we investigated the occurrence of HHV-6 and HHV-7 antigenemia in relation to symptomatic CMV infection after liver transplantation.

METHODS

Sample material from 64 adult liver transplant recipients was included in the study. The patients were monitored weekly for CMV, HHV-6, and HHV-7. CMV infections were diagnosed by pp65-antigenemia and viral cultures. Concomitantly HHV-6 and HHV-7 antigens were demonstrated in peripheral blood mononuclear cells by monoclonal antibodies against both variants A and B and immunoperoxidase staining. Altogether 540 post-transplant blood specimens were analyzed.

RESULTS

Nineteen patients (30%) developed symptomatic CMV pp65 antigenemia during the first 3 months (mean 33 days, range 5-62 days) post-transplantation and were treated with intravenous ganciclovir. Concurrent HHV-6 antigenemia was detected in 16/19 (median 9 days, range 6-24 days) and HHV-7 antigenemia 15/19 patients (median 17 days, range 5-58 days) after transplantation. HHV-6 appeared before CMV in most cases (12/16), HHV-7 usually together with CMV. In those cases that HHV-6 preceded CMV antigenemia, it also was a possible cause of graft dysfunction. HHV-7 and CMV were so closely overlapping, that no symptoms could solely be linked with HHV-7.

CONCLUSION

HHV-6 and HHV-7 antigenemia usually occurred together with symptomatic CMV infection after liver transplantation. HHV-6 preceded CMV, but HHV-7 appeared together with CMV. Further investigation of the clinical significance of HHV-6 and HHV-7 antigenemia in organ transplant patients is necessary.

Pretransplant human herpesvirus 6 infection of patients with acute liver failure is a risk factor for posttransplant human herpesvirus 6 infection of the liver

BACKGROUND

Acute liver failure (ALF) is a significant cause of liver transplantation. We have previously reported that human herpesvirus-6 (HHV-6) was found in most livers of patients with ALF of unknown origin ending up with liver transplantation. In this study, we investigated the posttransplant HHV-6 infection of the liver graft in these patients.

METHODS

Thirty-two patients transplanted due to ALF were included in this retrospective study. Twelve of the 15 patients with unknown cause and four of 17 patients with a known cause of ALF had HHV-6 antigens in the explanted liver. Altogether, 18 patients had some pretransplant evidence of HHV-6. After transplantation, the patients were frequently monitored for the viruses, and biopsy histology was performed in every case of graft dysfunction. HHV-6 was demonstrated in liver tissue by immunohistochemistry.

RESULTS

During the follow-up of 6 months, hepatic HHV-6 infection was demonstrated in 9 of the 18 patients, at a mean 19 days (6-38 days) after transplantation. All patients with posttransplant HHV-6 showed graft dysfunction. In biopsy histology, seven out of these nine patients demonstrated viral infection, one of them also having CMV antigens in the liver. None of those patients without evidence of pretransplant HHV-6 showed HHV-6 in the posttransplant biopsies. Posttransplant HHV-6 was not treated and the virus had no effect on 1-year patient or graft survivals.

CONCLUSION

Pretransplant hepatic HHV-6 infection of patients with ALF is a risk factor for posttransplant HHV-6 infection and liver dysfunction, but has no effect on 1-year graft or patient survival.

Fever, Human Herpesvirus-6 (HHV-6) Seroconversion, and Acute Rejection Episodes as a Function of the Initial Seroprevalence for HHV-6 in Renal Transplant Recipients

Human herpesvirus-6 (HHV-6) is an opportunistic viral pathogen of emerging clinical significance in immunocompromised patients. We performed a seroepidemiological survey to test the relation between seroprevalence among donors and recipients for HHV-6 at three endpoints. Before transplantation sera obtained from cadaveric donors and from potential recipients were tested for IgG antibodies against HHV-6 using an enzyme-linked immunoassay. The group of recipient sera, including samples obtained before as well as 2, 4, 12, and 48 weeks after transplantation, were tested for anti-HHV-6 IgM antibodies using an indirect immunofluorescence assay. The statistical analysis was performed with the Cox proportional hazards models. The HHV-6 seronegative group (n = 11) compared with the HHV-6 seropositive group (n = 109) showed twice the risk of HHV-6 IgM seroconversion (RR = 2.24; P < .04), with a greater risk of fever, namely 3.8, which was on the verge of statistical significance. The opposite trend toward an association with acute rejection episodes was observed among HHV-6 seronegative patients (RR = 1.81). The presence of IgG antibody in the sera of donors to IgG seropositive recipients had no association with the occurrence of IgM seroconversion. In contrast, IgM antibodies to HHV-6 appeared in four of five seronegative patients who received allografts from IgG seropositive donors. These preliminary data suggest that the effects seem to be the consequence of HHV-6 transmission through a renal allograft.

Viral infection in the renal transplant recipient

Viruses are among the most common causes of opportunistic infection after transplantation and the most important. The risk for viral infection is a function of the specific virus encountered, the intensity of immune suppression used to prevent graft rejection, and other host factors governing susceptibility. Viral infection, both symptomatic and asymptomatic, causes the "direct effects" of invasive disease and "indirect effects," including immune suppression predisposing to other opportunistic infections and oncogenesis. Rapid and sensitive microbiologic assays for many of the common viruses after transplantation have replaced, for the most part, serologic testing and in vitro cultures for the diagnosis of infection. Furthermore, quantitative molecular tests allow the individualization of antiviral therapies for prevention and treatment of infection. This advance is most prominent in the management of cytomegalovirus, Epstein-Barr, hepatitis B, and hepatitis C viruses. Diagnostic advances have not been accompanied by the development of specific and nontoxic anti-viral agents or effective antiviral vaccines. Vaccines, where available, should be given to patients as early as possible and well in advance of transplantation to optimize the immune response. Studies of viral latency, reactivation, and the cellular effects of viral infection will provide clues for future strategies in prevention and treatment of viral infections.

Update on human herpesvirus 6 biology, clinical features, and therapy

Human herpesvirus 6 (HHV-6) is a betaherpesvirus that is closely related to human cytomegalovirus. It was discovered in 1986, and HHV-6 literature has expanded considerably in the past 10 years. We here present an up-to-date and complete overview of the recent developments concerning HHV-6 biological features, clinical associations, and therapeutic approaches. HHV-6 gene expression regulation and gene products have been systematically characterized, and the multiple interactions between HHV-6 and the host immune system have been explored. Moreover, the discovery of the cellular receptor for HHV-6, CD46, has shed a new light on HHV-6 cell tropism. Furthermore, the in vitro interactions between HHV-6 and other viruses, particularly human immunodeficiency virus, and their relevance for the in vivo situation are discussed, as well as the transactivating capacities of several HHV-6 proteins. The insight into the clinical spectrum of HHV-6 is still evolving and, apart from being recognized as a major pathogen in transplant recipients (as exemplified by the rising number of prospective clinical studies), its role in central nervous system disease has become increasingly apparent. Finally, we present an overview of therapeutic options for HHV-6 therapy (including modes of action and resistance mechanisms).

Risk-Adapted Preemptive Therapy for Cytomegalovirus Disease after Allogeneic Stem Cell Transplantation: A Single-Center Experience in Korea

Cytomegalovirus (CMV) remains a major cause of infection in recipients of hematopoietic stem cell transplants (HSCT) and results in significant mortality and morbidity. We present the results of CMV pp65 antigenemia-guided, risk-adapted preemptive therapy aimed at preventing CMV disease in allogeneic HSCT. Preemptive ganciclovir treatment was started when more than 5 CMV antigen-positive cells were detected in the low-risk group (with grade 0-I acute GVHD and matched related HSCT) and when any antigen-positive cells were seen in the high-risk group (with grade II-IV acute GVHD or matched unrelated HSCT). At least 1 episode of antigenemia was observed in 53 (59.6%) of 89 patients before day 100, and preemptive therapy was performed in 33 patients. CMV disease occurred in 6 patients (5 in the high-risk group and 1 in the low-risk group), and late CMV disease developed in 4 patients. Only 1 patient died of CMV pneumonitis before day 100. Neutropenia was observed in 51.5% of ganciclovir-treated patients, and coinfection/superinfection was observed in 42.4%. A strategy of ganciclovir treatment focusing on patients at higher risk could reduce the toxicity from the antiviral drug and be cost-effective. Extended surveillance for CMV disease using more sensitive diagnostic methods is necessary in high-risk patients.

Human cytomegalovirus: clinical aspects, immune regulation, and emerging treatments

After initial infection, human cytomegalovirus remains in a persistent state with the host. Immunity against the virus controls replication, although intermitent viral shedding can still take place in the seropositive immunocompetent person. Replication of cytomegalovirus in the absence of an effective immune response is central to the pathogenesis of disease. Therefore, complications are primarily seen in individuals whose immune system is immature, or is suppressed by drug treatment or coinfection with other pathogens. Although our increasing knowledge of the host-virus relationship has lead to the development of new pharmacological strategies for cytomegalovirus-associated infections, these strategies all have limitations-eg, drug toxicities, development of resistance, poor oral bioavailability, and low potency. Immune-based therapies to complement pharmacological strategies for the successful treatment of virus-associated complications should be prospectively investigated.

Activation of HHV-6 in lymphoproliferative disorders: a polymerase chain reaction-based study

HHV-6 is a latent herpes virus persisting throughout the adult life of the infected host in an integrated form and is often activated in immunocompromised situations. Detection of HHV-6 DNA in the plasma of an individual indicates the presence of active viral replication in the host. Because lymphomas are known to be associated frequently with host immunosupression, we studied activation of HHV-6 in 98 patients diagnosed with Hodgkin's disease (HD) or non-Hodgkin's lymphoma (NHL). HHV-6 activation was documented in 34% of cases of non-Hodgkin's lymphoma and 39% of those of Hodgkin's disease; however, no correlation of activation status with pathological types of Hodgkin's disease and between copy numbers in peripheral blood mononuclear cell DNA and the corresponding plasma DNA was noticeable.

Human herpesvirus 6 (HHV6) infection

Human herpes virus-6 was first reported in 1986 and is the sixth member of the herpes virus family. HHV-6 consists of two closely related variants HHV-6A and HHV-6B. The majority of infections occur in healthy infants with most infections caused by HHV-6B. The virus preferentially infects CD4+T-lymphocytes and the surface marker CD46 acts as a co-receptor. Infection is followed by persistence and latency in different cells and organs including monocytes/macrophages, salivary glands, the brain and the kidneys. In this article we will discuss the clinical manifestations of HHV-6 infection in healthy children and the syndromes associated with HHV-6 reactivation in immunocompromised patients. Evidence of association between HHV-6 infection and different clinical entities such as multiple sclerosis, malignancy, infectious momononucleosis, drug hypersensitivity syndromes and skin eruptions is discussed. Published data on the use and efficacy of antiviral agents in complicated infections and infections in immunocompromised patients is presented.

Human herpesvirus-6 in renal transplant recipients: potential risk factors for the development of human herpesvirus-6 seroconversion

Herpesviruses, including human herpesvirus-6 (HHV-6), reactivate and have the potential to be pathogenic in immunocompromised patients. Little information is available regarding the correlation between immunosuppressive therapy and HHV-6 seroconversion after organ transplantation. Serum samples obtained from 120 kidney and kidney/pancreas transplant recipients were tested to explore the potential risk factors for developing HHV-6 infection including types of immunosuppression and induction/rejection therapy. Stored serum samples obtained prior to and at the 2nd, 4th, 12th and 48th weeks after transplantation were tested for anti-HHV-6 immunoglobulin (Ig)M antibodies using indirect immunofluorescence assay. Prior to transplantation and 48 weeks after transplantation the sera were additionally tested for anti-HHV-6 IgG using enzyme-linked immunoassay. Ninety-one percent of 120 recipients were HHV-6 IgG-positive before transplantation. One hundred seven of 120 patients were anti-HHV-6 IgM-negative before transplantation. Primary/secondary HHV-6 seroconversion occurred in sera of 46.6% of these 107 patients. HHV-6 seroconversion most frequently occurred 2 to 4 weeks after transplantation. There was no significant relationship between HHV-6 seroconversion and the treatment with methylprednisolone (MP). The incidence of HHV-6 seroconversion was significantly higher in subjects who were treated with the regimens including Daclizumab or Sirolimus as compared with those who were on other protocols. HHV-6 seropositivity in the Polish population of organ transplant recipients is very high. We demonstrated a trend toward association of HHV-6 seroconversion with type of immunosuppressive therapy.

Human herpesvirus-6 infection after lung and heart-lung transplantation: a prospective longitudinal study

BACKGROUND

Although human herpesvirus (HHV)-6 is now recognized as a frequent pathogen after transplantation, the real impact of this infection in patients undergoing transplantation remains unclear.

METHODS

During 27 months, 30 consecutive heart-lung- and lung-transplant recipients were included on the day of transplantation and prospectively followed during 100 days for HHV-6 infection.

RESULTS

HHV-6 infection occurred in 20 (66%) patients after a median delay of 18 days after transplantation. The virus was detected by polymerase chain reaction or culture, or both, in 15.7 % of blood specimens, in 14.5% of bronchoalveolar lavage fluids, and in many organs at postmortem examination; it was found by culture in eight patients. No clinical manifestations could clearly be associated with HHV-6 alone. However, patients with HHV-6 infection had a higher mortality rate than patients without HHV-6 infection (7 of 20 vs. 0 of 10; P=0.04), and all the deceased patients died during periods of HHV-6 infection. We did not observe higher incidence of infectious or graft-rejection episodes in HHV-6-positive patients. However, eight of nine viral or fungal infections occurred during HHV-6 infection and three were directly responsible for death.

CONCLUSION

Although frequently detected after transplantation, HHV-6 was not associated with any specific clinical manifestation. The higher mortality rate observed in patients with HHV-6 infection was not related to a higher incidence of bacterial infections or graft rejection but might be associated with more viral and fungal infections.

Prevalence and clinical significance of human herpesviruses 6 and 7 active infection in pediatric liver transplant patients

Recent studies in adult liver transplant patients have suggested that both human herpesvirus (HHV)-6 and HHV-7 infection are important causes of morbidity following liver transplantation. However, the impact of HHV-6 and -7 infection in pediatric liver transplant patients remains largely unknown. The aims were to determine the prevalence of HHV-6 and -7 infection in pediatric liver transplant patients and to determine whether there is an association between HHV-6 and -7 infection with episodes of graft rejection and cytomegalovirus (CMV) infection. A total of 46 pediatric liver transplant patients transplanted at Mayo Clinic between January 1994 and January 2000 were evaluated. Quantitative polymerase chain reaction (PCR) assays for CMV, HHV-6 and HHV-7 were performed on stored sera obtained prior to transplant, weekly for 8 wk and at 4 months and 1 yr post-transplant. Pretransplant sera were tested for HHV-6 antibodies by indirect immunofluorescence assay. A total of 215 blood samples were tested (mean 6.5 +/- 3.1, range 3-18). CMV infection occurred in 11 of 33 (33.3%) patients, while CMV disease occurred in 4 of 33 (12%) patients. Infection with HHV-6 (variant B) was detected in three of 33 (9.1%) patients. HHV-7 infection was not detected. Case 1 and 2 were infants (10- and 11-month old, respectively). Both were seronegative for HHV-6 pretransplant. In both cases, HHV-6 infection was associated with concurrent episodes of moderate to severe acute graft rejection. Case 3 was a 16-yr-old girl who was seropositive for HHV-6 pretransplant. No clinical events were recorded and a liver biopsy performed per protocol showed no evidence of rejection. None of the three patients had concomitant CMV infection or disease. In this study, HHV-6 infection occurred in 9% of pediatric liver transplant patients while HHV-7 was not detected. A potential association between primary HHV-6 infection and allograft rejection warrants further investigation.

Human herpesvirus-6 and -7 infections in transplantation

Human herpesvirus-6 (HHV-6) and human herpesvirus-7 (HHV-7) are ubiquitous in the human population and cause exanthem subitum, a benign disease seen in infancy. The viruses remain latent in the body after primary infection, and reactivate in immunocompromised patients. HHV-6 infection occurs in nearly 50% of all bone marrow and in 20-30% of solid-organ transplant recipients, 2-3 weeks following the procedure. It has been suggested that the viral infection and activation result in clinical symptoms, including fever, skin rash, pneumonia, bone marrow suppression, encephalitis, and rejection. In order to understand the viral infection in greater detail, several studies investigating the route of viral transmission and diagnostic procedures have been carried out. In contrast to studies of HHV-6 infection in organ-transplant recipients, the number of studies examining HHV-7 infection in these patients is limited. According to several recent studies, HHV-7 may act as a cofactor for cytomegalovirus disease in organ-transplant recipients.

Human herpesvirus 6: molecular biology and clinical features

Human herpesvirus 6 (HHV-6) exists as distinct variants HHV-6A and HHV-6B. The complete genomes of HHV-6A and HHV-6B have been sequenced. HHV-6B contains 97 unique genes. CD46 is the cell receptor for HHV-6, explaining its broad tissue tropism but its restricted host-species range. HHV-6 utilizes a number of strategies to down-regulate the host immune response, including molecular mimicry by production of a functional chemokine and chemokine receptors. Immunosuppression is enhanced by depletion of CD4 T lymphocytes via direct infection of intra-thymic progenitors and by apoptosis induction. Infection is widespread in infants between 6 months and 2 years of age. A minority of infants develop roseola infantum, but undifferentiated febrile illness is more common. Reactivation from latency occurs in immunocompromised hosts. Organ-specific clinical syndromes occasionally result, but indirect effects including interactions with other viruses such as human immunodeficiency virus type 1 and human cytomegalovirus or graft dysfunction in transplant recipients may be more significant complications in this population. Recent advances in quantitative PCR are providing additional insights into the natural history of infection in paediatric populations and immunocompromised hosts.

Virus del herpes humano tipo 6 y tipo 7 en receptores de trasplantes

Recent years have witnessed a growing interest in the role of human herpesvirus (HHV) type 6 and type 7 as emerging pathogens or copathogens in transplant recipients. Both HHV-6 and HHV-7 belong to the beta-herpesvirus family and are closely related to another member of the family, cytomegalovirus. After the primary infection, these viruses remain latent in the human host and can reactivate after transplantation. Various clinical processes such as fever, rash, pneumonitis, encephalitis, hepatitis, and myelosuppression have been described in association with herpesvirus. Moreover, a growing body of evidence suggests that the major impact of HHV-6 and HHV-7 reactivation in transplantation is related to indirect effects, such as their association with cytomegalovirus disease, increased opportunistic infections, and graft dysfunction and rejection. The pathogenesis of HHV-6 and HHV-7 during the post-transplantation period, the methods used for their diagnosis, and the evaluation of antiviral drugs and strategies for their prevention and treatment are now the subject of extensive research.

Economic impact of cytomegalovirus in solid organ transplantation

Cytomegalovirus (CMV) infection has a direct effect on morbidity in solid organ transplantation patients, and indirect effects related to the development of opportunistic infections, allograft rejection, and patient mortality. Although intuitively it follows that costs attributable to CMV infections would be increased, direct proof has remained elusive. Accumulating evidence suggests, however, that CMV infection has a significant impact on the costs to transplantation programs, particularly in seronegative recipients of seropositive allografts (D+/R-), and additional costs may be incurred through the effects on CMV potentiating the risks of various opportunistic infections leading to graft rejection.

Detection of DNA of lymphotropic herpesviruses in plasma of human immunodeficiency virus-infected patients: frequency and clinical significance

The frequency and clinical significance of detection of DNA of cytomegalovirus (CMV), Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), HHV-7, and HHV-8 in plasma were investigated by PCR. The plasma was obtained from 120 selected human immunodeficiency virus (HIV)-infected patients, of whom 75 had AIDS-related manifestations, 32 had primary HIV infection (PHI), and 13 had asymptomatic infections. Nested PCR analysis revealed that none of the lymphotropic herpesviruses tested were found in patients with PHI, in asymptomatic HIV-positive individuals, or in HIV-negative controls. By contrast, DNA of one or more of the viruses was found in 42 (56%) of 75 patients with AIDS-related manifestations, including CMV disease (CMV-D) or AIDS-related tumors. The presence of CMV DNA in plasma was significantly associated with CMV-D (P < 0.001). By contrast, EBV detection was not significantly associated with AIDS-related lymphomas (P = 0.31). Interestingly, the presence of HHV-8 DNA in plasma was significantly associated with Kaposi's sarcoma (KS) disease (P < 0.001) and with the clinical status of KS patients (P < 0.001). CMV (primarily), EBV, and HHV-8 were the viruses most commonly reactivated in the context of severe immunosuppression (P < 0.05). In contrast, HHV-6 and HHV-7 infections were infrequent at any stage of disease. In conclusion, plasma PCR was confirmed to be useful in the diagnosis of CMV-D but not in that of tumors or other conditions possibly associated with EBV, HHV-6, and HHV-7. Our findings support the hypothesis of a direct involvement of HHV-8 replication in KS pathogenesis, thus emphasizing the usefulness of sensitive and specific diagnostic tests to monitor HHV-8 infection.