Cytomegalovirus, human herpesvirus-6, and human herpesvirus-7 in hematological patients

Oral shedding of herpesviruses and clinical outcomes in hematopoietic stem cell transplant patients

OBJECTIVES

To characterize the oral shedding of herpes viruses in patients who underwent allogeneic hematopoietic stem cell transplantation (alloHSCT) and investigate its relationship with clinical outcomes.

MATERIALS AND METHODS

Polymerase chain reaction and enzymatic digestion were performed to identify the oral shedding of the members of the Herpesviridae family in 31 patients. The samples were collected from the oral cavity at five timestamps.

RESULTS

The presence of each herpesvirus in the oral cavity was observed in 3.2%, 12.9%, 19.3%, 32.2%, 54.8% and 93.5% patients for human herpesvirus (HHV)-6A, herpes simplex virus-1, HHV-6B, cytomegalovirus (CMV), Epstein-Barr virus (EBV) and HHV-7, respectively. Oral shedding of herpes virus was not uncommon after alloHSCT. There was a statistically significant association between the EBV and CMV oral shedding at C1 and the cumulative incidence of acute graft-versus-host disease (aGVHD). The results suggested that the presence of HSV-1 at C2 was related to a relapse. The HHV-7 oral shedding at C2 suggests a possible link between relapse, progression-free survival and overall survival of the patients.

CONCLUSIONS

Patients who developed aGVHD showed higher CMV and EBV shedding in the oral cavity at aplasia, suggesting modifications to the pattern of immune cell response and inflammatory microenvironment.

Α case of seronegative autoimmune encephalitis associated with human herpesvirus-7 (HHV-7)

In the last 10 years, an increased number of patients presenting with acute encephalitis is being observed, a finding that is attributed to autoimmune mechanisms. Despite the fact that autoantibodies usually target the neuronal cell surface or synaptic proteins in the central nervous system (CNS), in many cases these remain undetectable, constituting a future diagnostic and therapeutic challenge. Human herpesvirus-7 (HHV-7) is proven to be a neurotropic virus, causing various neurological complications mostly in the adult population. We present the case of a 10-year-old girl, with confirmed active HHV-7 infection of the CNS, who developed acute seronegative autoimmune encephalitis. To our best knowledge, there is no literature concerning pediatric cases of autoimmune encephalitis following HHV-7 infection.

Emerging strategies for enhancing the homing of hematopoietic stem cells to the bone marrow after transplantation

Bone marrow failure is the primary cause of death after nuclear accidents or intentional exposure to high or low doses of ionizing radiation. Hematopoietic stem cell transplantation is the most potent treatment procedure for patients suffering from several hematopoietic malignancies arising after radiation injuries. Successful hematopoietic recovery after transplantation depends on efficient homing and subsequent engraftment of hematopoietic stem cells in specific niches within the bone marrow. It is a rapid and coordinated process in which circulating cells actively enter the bone marrow through the process known as transvascular migration, which involves the tightly regulated relay of events that finally leads to homing of cells in the bone marrow. Various adhesion molecules, chemokines, glycoproteins, integrins, present both on the surface of stem cells and sinusoidal endothelium plays a critical role in transvascular migration. But despite having an in-depth knowledge of homing and engraftment and the key events that regulate it, we are still not completely able to avoid graft failures and post-transplant mortalities. This deems it necessary to design a flawless plan for successful transplantation. Here, in this review, we will discuss the current clinical methods used to overcome graft failures and their flaws. We will also discuss, what are the new approaches developed in the past 10-12 years to selectively deliver the hematopoietic stem cells in the bone marrow by adopting proper targeting strategies that can help revolutionize the field of regenerative and translational medicine.

Impact of High-Frequency HLA Haplotypes on Clinical Cytomegalovirus Reactivation in Allogeneic Hematopoietic Stem Cell Transplantation

Some studies support the hypothesis that HLA genes and haplotypes evolved by natural selection through their protective abilities against specific infectious pathogens. However, very little is known regarding the impact of high-frequency HLA haplotypes on the risk of relevant infectious diseases among a given ethnic group. We evaluated the impact of high-frequency HLA haplotypes on cytomegalovirus (CMV) reactivation and infection in allogeneic hematopoietic stem cell transplantation (allo-HSCT) in a Japanese population as a model of infectious disease that has coexisted with humans. A total of 21,127 donor-patient pairs were analyzed. HLA-A-B-DRB1 haplotypes were estimated using the maximum probability algorithm. Seven haplotypes with >1% frequency were defined as high-frequency haplotypes (HfHPs). Homozygotes of HfHP and heterozygotes had significantly lower risk of CMV reactivation and infection (hazard ratio [HR] = 0.88, P = .009 and HR = 0.93, P = .003, respectively) than homozygotes of low-frequency HLA haplotypes (LfHPs). In subgroup analyses of a different donor source, these associations were statistically significant in unrelated donor transplants. Finally, CMV risk for homozygotes and heterozygotes of each HfHP was compared with that of homozygotes of LfHPs. The 2 most predominant HfHP groups (A*24:02-B*52:01-DRB1*15:02 group and A*24:02-B*07:02-DRB1*01:01 group) had a significantly lower risk of CMV reactivation and infection (HR = 0.86, P < .001 and HR = 0.91, P = .033, respectively). Our findings suggest that HfHPs may be protective against CMV reactivation and infection and that increased care regarding CMV reactivation and infection may be necessary for patients with LfHP after allo-HSCT.

Transfusion support issues in hematopoietic stem cell transplantation

BACKGROUND

Patients receiving hematopoietic stem cell transplantation require extensive transfusion support until red blood cell and platelet engraftment occurs. Rare but predictable complications may arise when the transplanted stem cells are incompatible with the native ABO type of the patient. Immediate and delayed hemolysis is often seen.

METHODS

A literature review was performed and the results from peer-reviewed papers that contained reproducible findings were integrated.

RESULTS

A strong body of clinical evidence has developed around the common complications experienced with ABO-incompatible hematopoietic stem cell transplantation. These complications are discussed and the underlying pathophysiology is explained. General treatment options and guidelines are enumerated.

CONCLUSIONS

ABO-incompatible hematopoietic stem cell transplantations are frequently performed. Immune-related hemolysis is a commonly encountered complication; therefore, health care professionals must recognize the signs of immune-mediated hemolysis and understand the various etiologies that may drive the process.

Adoptive transfer of cytomegalovirus-specific effector CD4+ T cells provides antiviral protection from murine CMV infection

Cytomegalovirus (CMV) infects a majority of the human population and establishes a life-long persistence. CMV infection is usually asymptomatic but the virus carries pathogenic potential and causes severe disease in immunocompromised individuals. T-cell-mediated immunity plays an essential role in control of CMV infection and adoptive transfer of CMV-specific CD8(+) T cells restores viral immunity in immunosuppressed patients but a role for CD4(+) T cells remains elusive. Here, we analyzed in adoptive transfer studies the features and antiviral functions of virus-specific CD4(+) T cells during primary murine CMV (MCMV) infection. MCMV-specific CD4(+) T cells expanded upon MCMV infection and displayed an effector phenotype and function. Adoptive transfer of in vivo activated MCMV-specific CD4(+) T cells to immune-compromised mice was protective during pathogenic MCMV infection and IFN-γ was a crucial mediator of this protective capacity. Moreover, co-transfer of low doses of both MCMV-specific CD4(+) T cells and CD8(+) T cells synergized in control of lytic viral replication in immune-compromised mice. Our data reveal a pivotal antiviral role for virus-specific CD4(+) T cells in protection from pathogenic CMV infection and provide evidence for their antiviral therapeutic potential.

Longitudinal analysis of antibody response to immunization in paediatric survivors after allogeneic haematopoietic stem cell transplantation

The long-term antibody responses to re-immunization in recipients of allogeneic haematopoietic stem cell transplantation (allo-HSCT) have not been well studied. We prospectively and longitudinally evaluated the antibody responses to eight vaccine antigens (diphtheria, tetanus, pertussis, measles, mumps, rubella, hepatitis B, and poliovirus) and assessed the factors associated with negative titres in 210 allo-HSCT recipients at St. Jude Children's Research Hospital. Antibody responses lasting for more than 5 years after immunization were observed in most patients for tetanus (95.7%), rubella (92.3%), poliovirus (97.9%), and, in diphtheria-tetanus-acellular pertussis (DTaP) recipients, diphtheria (100%). However, responses to pertussis (25.0%), measles (66.7%), mumps (61.5%), hepatitis B (72.9%), and diphtheria in tetanus-diphtheria (Td) recipients (48.6%) were less favourable, with either only transient antibody responses or persistently negative titres. Factors associated with vaccine failure were older age at immunization; lower CD3, CD4 or CD19 counts; higher IgM concentrations; positive recipient cytomegalovirus serology; negative titres before immunization; acute or chronic graft-versus-host disease; and radiation during preconditioning. These response patterns and clinical factors can be used to formulate re-immunization and monitoring strategies. Patients at risk for vaccine failure should have long-term follow-up; those with loss of antibody response or no seroconversion should receive booster immunizations.

The roles of viruses in brain tumor initiation and oncomodulation

While some avian retroviruses have been shown to induce gliomas in animal models, human herpesviruses, specifically, the most extensively studied cytomegalovirus, and the much less studied roseolovirus HHV-6, and Herpes simplex viruses 1 and 2, currently attract more and more attention as possible contributing or initiating factors in the development of human brain tumors. The aim of this review is to summarize and highlight the most provoking findings indicating a potential causative link between brain tumors, specifically malignant gliomas, and viruses in the context of the concepts of viral oncomodulation and the tumor stem cell origin.

Transmission of cytomegalovirus (CMV) infection by leukoreduced blood products not tested for CMV antibodies: a single-center prospective study in high-risk patients undergoing allogeneic hematopoietic stem cell transplantation (CME)

BACKGROUND

Measures to prevent transfusion-transmitted cytomegalovirus (TT-CMV) infection after hematopoietic stem cell transplantation (HSCT) include transfusion of CMV antibody-negative blood units and/or transfusion of leukoreduced cellular blood products. We assessed the incidence of TT-CMV in CMV-seronegative patients receiving CMV-seronegative HSC transplants, who were transfused with leukoreduced cellular blood products not tested for anti-CMV.

STUDY DESIGN AND METHODS

In a prospective observational study between 1999 and 2009, all HSCT patients received leukoreduced cellular blood products not tested for anti-CMV. Patients were screened for CMV serostatus and CMV-negative recipients of CMV-negative transplants were systematically monitored for TT-CMV clinically and by CMV nucleic acid testing. Anti-CMV antibodies (immunoglobulin [Ig]G and IgM) were assessed after three time intervals (Interval 1, study inclusion to Day +30 after HSCT; Interval 2, Day +30-Day +100; Interval 3, after Day +100).

RESULTS

Among 142 patients treated with allogeneic HSCT, 23 CMV-negative donor-patient pairs were identified. These 23 patients received 1847 blood products from 3180 donors. All patients remained negative for CMV DNA and none developed CMV-associated clinical complications. This results in a risk for TT-CMV per donor exposure of 0% (95% confidence interval, 0.0%-0.12%). However, 17 of 23 patients seroconverted for anti-CMV IgG, but none for anti-CMV IgM. CMV IgG seroconverters received significantly more transfusions per week than nonconverters.

CONCLUSION

The risk of TT-CMV is low in high-risk CMV(neg/neg) HSCT patients transfused with leukoreduced blood products not tested for anti-CMV. The cause of anti-CMV IgG seroconversion is most likely passive antibody transmission by blood products.

Natural killer cell receptor repertoire and their ligands, and the risk of CMV infection after kidney transplantation

Cytomegalovirus (CMV) infection is the most common viral complication after solid organ transplantation (SOT). Whilst current immunosuppression is known to impair antiviral-specific T-cell immunity in SOT, a potential role for natural killer (NK) cells not affected by immunosuppressive therapy remains to be determined. To address this, we compared the genotype of the NK immunoglobulin-like receptor (KIR) genes and their HLA cognate ligands to the rate of CMV infection in 196 kidney transplant recipients. We have shown that the absence of the HLA-C ligand for inhibitory KIR and the presence of activating KIR genes in the recipients were both associated with a lower rate of CMV infection after transplantation. In a cohort of 17 recipients with acute CMV infection, NK cells were phenotyped over a period of time after diagnosis by their expression profile of C-type lectin receptors and capacity to secrete IFN-gamma. The increased expression of the activating C-type lectin receptors NKG2C and NKG2D was paralleled by the decreased IFN-gamma secretion during the early phase of CMV infection. In conclusion, our findings suggest that KIR/HLA genotype and expression of NKG2C and NKG2D might play a significant role in regulating NK cell function and anti-CMV immunity after kidney transplantation.

Crucial role of FLT3 ligand in immune reconstitution after bone marrow transplantation and high-dose chemotherapy

Almost 5 decades after the first clinical transplantations, delayed immune reconstitution remains a considerable hurdle in bone marrow transplantation, and the mechanisms regulating immune reconstitution after transplantation remain to be established. Whereas adult fms-like tyrosine kinase 3 ligand-deficient (FL(-/-)) mice have reduced numbers of early B- and T-cell progenitors, they sustain close to normal levels of mature B and T cells. Herein, we demonstrate that adult bone marrow cells fail to reconstitute B-cell progenitors and conventional B cells in lethally irradiated FL(-/-) recipients, which also display delayed kinetics of T-cell reconstitution. Similarly, FL is essential for B-cell regeneration after chemotherapy-induced myeloablation. In contrast, fetal progenitors reconstitute B lymphopoiesis in FL(-/-) mice, albeit at reduced levels. A critical role of FL in adult B lymphopoiesis is further substantiated by an age-progressive decline in peripheral conventional B cells in FL(-/-) mice, whereas fetally and early postnatally derived B1 and marginal zone B cells are sustained in a FL-independent manner. Thus, FL plays a crucial role in sustaining conventional B lymphopoiesis in adult mice and, as a consequence, our findings implicate a critical role of FL in promoting immune reconstitution after myeloablation and bone marrow transplantation.

Hepatic complications of hematopoietic cell transplantation

Acute and chronic liver disease contributes significantly to morbidity and mortality following hematopoietic cell transplantation (HCT). The best prognostic indicator for the development of severe liver dysfunction is an early rise in liver function test results after HCT. The leading causes soon after HCT are acute graft-versus-host disease (GVHD), sinusoidal obstruction syndrome, drug and total parenteral nutrition hepatotoxicity, sepsis, and viral infection. Hepatic herpesvirus and fungal infections after HCT, though uncommon, can be life-threatening and warrant immediate diagnosis and treatment. Hepatitis B, hepatitis C virus, iron overload, and chronic GVHD are among the most common causes for chronic liver disease after HCT. Because treatments are directed at the underlying etiology of liver disease, prompt diagnosis by means of laboratory tests, hepatic imaging, and often liver biopsy is required after HCT.

The KSHV and other human herpesviral G protein-coupled receptors

Kaposi sarcoma-associated herpesvirus (KSHV) is a gamma2-herpesvirus discovered in 1994 and is the agent responsible for Kaposi sarcoma (KS), an endothelial cell malignancy responsible for significant morbidity and mortality worldwide. Over time, KSHV has pirated many human genes whose products regulate angiogenesis, inflammation, and the cell cycle. One of these encodes for a mutated G protein-coupled receptor (GPCR) that is a homologue of the human IL-8 receptor. GPCRs are the largest family of signaling molecules and respond to a wide array of ligands. Unlike its normal counterpart, the mutations present in KSHV vGPCR result in constitutive, ligand-independent signaling activity. Signaling by the KSHV vGPCR results in the elaboration of many mitogenic and angiogenic cytokines that are vital to the biology of KS and other KSHV-driven malignancies. Several other herpesviruses also encode GPCRs, the functions of which are under ongoing investigation. In addition, several human diseases are associated with mutated mammalian GPCRs in germline or somatic cells.

The human herpesvirus 6 G protein-coupled receptor homolog U51 positively regulates virus replication and enhances cell-cell fusion in vitro

Human herpesvirus 6 (HHV-6) is a ubiquitous T-lymphotropic betaherpesvirus that encodes two G protein-coupled receptor homologs, U12 and U51. HHV-6A U51 has been reported to bind to CC chemokines including RANTES, but the biological function of U51 remains uncertain. In this report, we stably expressed short interfering RNAs (siRNAs) specific for U51 in human T cells and then infected these cells with HHV-6. Viral DNA replication was reduced 50-fold by the U51 siRNA, and virally induced cytopathic effects were also inhibited. In contrast, viral replication and syncytium formation were unaltered in cells that expressed a scrambled derivative of the siRNA or an irrelevant siRNA and were restored to normal when a human codon-optimized derivative of U51 was introduced into cells containing the U51 siRNA. To examine the mechanism whereby U51 might contribute to viral replication, we explored the signaling characteristics of U51. None of the chemokines and opioids tested was able to induce G protein coupling by U51, and no evidence for opioid ligand binding by U51 was obtained. The effect of U51 on cell-cell fusion was also evaluated; these studies showed that U51 enhanced cell fusion mediated by the G protein of vesicular stomatitis virus. However, a U51-specific antiserum had no virus-neutralizing activity, suggesting that U51 may not be involved in the initial interaction between the virus particle and host cell. Overall, these studies suggest that HHV-6 U51 is a positive regulator of virus replication in vitro, perhaps because it may promote membrane fusion and facilitates cell-cell spread of this highly cell-associated virus.

Effect of prophylactic valacyclovir on the presence of human herpesvirus DNA in saliva of healthy individuals after dental treatment

Human herpesviruses (HHVs) are ubiquitous pathogens that intermittently reactivate from latency. Transmission is believed to be facilitated by their frequent appearance in saliva. This study sought to understand the factors that influence the appearance of these viruses in saliva by examining the prevalence, pattern, and quantity of all eight HHVs in saliva of immunocompetent adults with a history of recurrent oral herpes simplex virus (HSV) infections following dental treatment and antiviral therapy. Valacyclovir or matched placebo was given (2 g twice on the day of treatment and 1 g twice the following day) to 125 patients in a randomized, double-blind controlled trial. Saliva, collected on the day of dental treatment and 3 and 7 days later, was analyzed using real-time quantitative PCR. At all visits, HHVs coinfected saliva. Over the course of the week, the DNAs of HHV-6 and HHV-7 were detected significantly more often (97% to 99% of patients) than Epstein-Barr virus (EBV; 64.8%), HSV-1 (13.0%), HHV-8 (3.2%), cytomegalovirus (2.4%), HSV-2 (0%), and varicella-zoster virus (0%), irrespective of drug treatment (P < 0.002). Mean genome copy numbers were highest for HSV-1 and HHV-6. Dental treatment did not influence asymptomatic viral shedding patterns. However, valacyclovir treatment resulted in significantly fewer patients shedding EBV at both postoperative visits compared with placebo (P < 0.008). These results suggest that HHVs are simultaneously present in the saliva of healthy adults at levels that could facilitate transmission, and valacyclovir therapy decreases the prevalence of EBV in saliva but has little effect on HHV-6 and HHV-7.

Cytomegalovirus Infection of the Heart Is Common in Patients with Fatal Myocarditis

BACKGROUND

Although enteroviruses and adenoviruses are considered to be the leading causes of the usually mild clinical myocarditis, little is known about the etiology of severe or fatal myocarditis.

METHODS

We collected all available clinical records and myocardial autopsy samples for patients who had myocarditis recorded as the underlying cause of death in Finland during the period of 1970-1998. Findings for all available patients (20 men and 20 women; median age, 49 years) with myocarditis that fulfilled the Dallas criteria and who had sufficient data were included in the study. Twelve subjects who had died accidentally served as control subjects. Polymerase chain reaction (PCR) and in situ hybridization assays were used for detection of viral genomes (adenovirus, cytomegalovirus, enterovirus, human herpesvirus 6, influenza A and B viruses, parvovirus B19, and rhinovirus) in heart samples.

RESULTS

Viral nucleic acids were found in the hearts of 17 patients (43%), including cytomegalovirus (15 patients), parvovirus B19 (4 patients), enterovirus (1 patient), and human herpesvirus 6 (1 patient). In 4 patients, cytomegalovirus DNA was found in addition to parvovirus B19 or enterovirus genomes. No adenoviruses, rhinoviruses, or influenza viruses were detected in this study of fatal myocarditis. In 67% of the patients for whom PCR was positive for cytomegalovirus, in situ hybridization revealed viral DNA in cardiomyocytes. Only 1 of these patients was immunocompromised. In the control group, only human herpesvirus 6 (1 subject) and parvovirus B19 (1 subject) DNA were detected.

CONCLUSIONS

In this population-based study, cytomegalovirus was found to be the most common specific finding in immunocompetent patients with fatal myocarditis. This may have important clinical implications for the treatment of severe acute myocarditis.

Detection of human herpesvirus 7 DNA in peripheral blood reflects mainly CD4+ cell count in patients infected with HIV

The opportunistic behavior and the potential interactions of human herpesvirus 7 (HHV-7) with human immunodeficiency virus (HIV)-1 in HIV-1-infected patients were investigated in comparison with HHV-6, another human roseolovirus. Roseolovirus DNAs were detected and quantified in peripheral blood mononuclear cells (PBMCs) from 198 HIV-seronegative healthy blood donors, 38 HIV-1-infected patients classified as long-term non-progressors, and 99 HIV-1-infected patients classified as progressors. The rate of HHV-7 DNA detection was higher in healthy donors (78%) than in long-term non-progressors (47%; P = 0.0003) or in progressors (52%; P < 0.0001). HHV-7 cell load was higher in healthy donors (median: 212 EqCop/10(6) PBMCs) and in long-term non-progressors (median: 105 EqCop/10(6) PBMCs) than in progressors (median: 48 EqCop/10(6) PBMCs; P < 0.0001 and P = 0.015, respectively). Among progressors, HHV-7 detection was correlated positively with the CD4(+) T-lymphocyte count (P = 0.028). Neither HHV-7 detection rate nor cell load was correlated with the HIV-1 plasma load. As a whole, HHV-6 detection rate and cell load were lower than the HHV-7 counterparts, albeit exhibiting similar differences between healthy donors, long-term non-progressors, and progressors. In conclusion, HHV-7 infection does not appear to be stimulated by HIV-1 infection, nor interact with it. Rather, HHV-7 detection rate and cell load reflect CD4(+) T-lymphocyte count, with higher values in healthy donors and long-term non-progressors than in progressors.

Update on neuroimaging in infectious central nervous system disease

PURPOSE OF REVIEW

Neuroimaging constitutes an important component in the diagnosis of the underlying infectious agents in central nervous system infection. This review summarizes progress in the neuroimaging of infectious central nervous system disease since January 2003. It focuses on imaging of viral encephalitis, including that caused by exotic and emerging viruses, and on imaging in immunodeficient patients.

RECENT FINDINGS

Diffusion-weighted imaging has been shown to be superior to conventional magnetic resonance imaging for the detection of early signal abnormalities in herpes simplex virus encephalitis but also in enterovirus 71 encephalitis and in West Nile encephalitis. Several studies defined the pattern of magnetic resonance imaging signal changes in endemic diseases such as West Nile encephalitis, Murray Valley encephalitis, enterovirus 71 encephalitis and Japanese encephalitis, but also in encephalitides due to ubiquitous viruses such as measles virus and Lyssavirus (rabies). In patients with HIV infection, apparent diffusion coefficient ratios obtained by diffusion-weighted imaging were significantly greater in lesions due to Toxoplasma encephalitis than in primary central nervous system lymphomas.

SUMMARY

The diagnosis of unclear infectious central nervous system diseases remains a challenge. More recent magnetic resonance imaging techniques, such as diffusion-weighted imaging and magnetic resonance spectroscopy, provide additional helpful information. However, the mainstay of diagnosis remains the detection of viral DNA or serological markers of specific infectious agents within the cerebrospinal fluid.