Prolonged inhibitory effect of 9-(1,3-dihydroxy-2-propoxymethyl)guanine against replication of Epstein-Barr virus

Effect of Herpesvirus Inhibition on Primary SIV Infection in Cynomolgus Monkeys

Foscarnet and (-)9-[4-hydroxy-2-(hydroxymethyl)butyl] guanine (H2G) have already been shown to inhibit herpesviruses in vitro and also to inhibit viral antigen production in primary SIV infection in monkeys. Attempts have been made to determine if these invivo effects on SIV were due to a direct effect on SIV or were mediated through inhibition of endogenous transactivating herpesviruses. The possible involvement of herpesviruses in primary SIVsm infection in monkeys was studied by the use of various inhibitors of herpesvirus replication. Subcutaneous injections of 3 × 5 mg kg−1 day−1 of aciclovir, 3 × 5 mg kg−1 day−1 of ganciclovir and 3 × 28 mg kg−1 day−1 of phosphonoacetic acid had no effect on primary SIVsm infection in cynomolgus monkeys. These doses of aciclovir, ganciclovir and phosphonoacetic acid are inhibitory to several herpesviruses. The results suggest that the effects of foscarnet and H2G on primary SIVsm infection in monkeys are direct and not mediated through inhibition of a replicating herpesvirus.

Population pharmacokinetics of valganciclovir prophylaxis in paediatric and adult solid organ transplant recipients

AIM

Our aims were to quantify ganciclovir pharmacokinetics in paediatric and adult kidney, liver and lung transplant patients taking a range of valganciclovir doses to prevent herpes virus infections, including a 450 mg regimen, and to identify sources of pharmacokinetic variability.

METHOD

Plasma samples were collected at 2, 4, 8 and 12 weeks post-transplant and at 4, 6, 8 and 12 months post-transplant in subjects prescribed longer courses. Ganciclovir was measured by liquid chromatography/ultraviolet detection. Non-linear mixed effects modelling was used to analyze the concentration-time data and evaluate demographic and transplant-related covariates.

RESULTS

A two compartment model with first order absorption best described the data. Given the range of body sizes, clearance and volume of distribution terms were scaled using standard weight-based allometric exponents. Creatinine clearance was included on apparent oral clearance. Final estimates in a standard 70 kg individual for apparent oral clearance, central volume of distribution, intercompartmental clearance and peripheral volume of distribution were 14.5 l h(-1) , 87.5 l, 4.80 l h(-1) and 42.6 l, respectively. The median terminal half-life for kidney, liver and lung transplant recipients was 9.4, 9.5 and 8.2 h, respectively. Median exposure (i.e. AUC(0,∞) in subjects taking valganciclovir 900 mg or 450 mg once daily was 57.4 and 34.3 μg ml(-1)  h, respectively.

CONCLUSION

Allometric scaling allowed simultaneous analysis of data from children and adults. Ganciclovir pharmacokinetics were similar among kidney, liver and lung transplant recipients. Ganciclovir exposure after valganciclovir 450 mg once daily may be suboptimal in some individuals and requires evaluation along with virologic outcomes data.

Progress and problems in understanding and managing primary Epstein-Barr virus infections

Epstein-Barr virus (EBV) is a gammaherpesvirus that infects a large fraction of the human population. Primary infection is often asymptomatic but results in lifelong infection, which is kept in check by the host immune system. In some cases, primary infection can result in infectious mononucleosis. Furthermore, when host-virus balance is not achieved, the virus can drive potentially lethal lymphoproliferation and lymphomagenesis. In this review, we describe the biology of EBV and the host immune response. We review the diagnosis of EBV infection and discuss the characteristics and pathogenesis of infectious mononucleosis. These topics are approached in the context of developing therapeutic and preventative strategies.

Viral DNA contamination is responsible for Epstein-Barr virus detection in cytotoxic T lymphocytes stimulated in vitro with Epstein-Barr virus B-lymphoblastoid cell line

Epstein-Barr virus (EBV)-transformed B-lymphoblastoid cell lines (LCLs) are used to prepare human EBV-specific T lymphocytes (EBV-CTL) in vitro. Within an LCL, up to 5-7% the cells release infectious EBV, and this has fostered safety concerns for therapeutic applications because of the exposure of T cells to EBV. The release of infectious viruses can be prevented by ganciclovir, but this drug may seriously affect LCL growth. In the wake of these concerns, the present work was designed to compile safety data on EBV-CTL preparation for the purpose of submission to a regulatory agency. We showed that further to supernatant exclusion, the number of EBV genome copies (EBVc) associated with the EBV-CTL always made up a constant proportion of the EBVc number detected in the culture supernatant. In addition, such was the case whether infectious virus could be produced by the LCL or not, suggesting that the EBV signal detected was due to a DNA contamination rather than an infection. Furthermore, we demonstrated that the number of EBVc associated with the EBV-CTL was highly sensitive to DNAse treatment, and finally that EBVc could no longer be detected after the EBV-CTL had been amplified in the absence of LCL. Consequently, during in vitro EBV-CTL preparation, either T cells cannot be infected or they die rapidly after EBV infection.

The pharmacokinetics of valganciclovir prophylaxis in pediatric solid organ transplant patients at risk for Epstein-Barr virus disease

Antiviral prophylaxis with valganciclovir is used frequently in pediatric solid organ transplant patients to prevent Epstein-Barr virus (EBV)-induced infections and tissue-invasive disease including post-transplant lymphoproliferative disorder (PTLD). This approach is untested in clinical trials and valganciclovir dosing strategies in children are highly variable. Our objective was to characterize the pharmacokinetics of ganciclovir in the plasma of pediatric kidney and liver transplant patients taking valganciclovir for EBV prophylaxis. Virologic response was also evaluated. Ganciclovir was measured by liquid chromatography/ultraviolet detection. EBV DNA was quantified by TaqMan(®) polymerase chain reaction. NONMEM(®) VI was used for data analysis. Ganciclovir plasma profiles were consistent with a one-compartment model. Final model estimates of apparent oral clearance (L/h), apparent volume of distribution (L), and absorption rate constant were 7.33, 35.1, and 0.85, respectively. There was evidence of lower bioavailability in children younger than three years. All eight subjects achieved ganciclovir plasma concentrations above reported in vitro concentrations needed to inhibit EBV replication by 50%. However, four subjects had detectable EBV DNA with a median (range) of 18,300 (4,400 to 54,900) copies/mL of whole blood. These findings support the need for further studies of the clinical pharmacology and efficacy of valganciclovir for EBV prophylaxis.

Valacyclovir pharmacokinetics and exploratory pharmacodynamics in young adults with Epstein-Barr virus infectious mononucleosis

Primary Epstein-Barr virus (EBV) infection often results in infectious mononucleosis and is associated with serious sequelae. No treatment is approved for EBV infection, and an antiviral intervention would be significant. The objectives of this study are to characterize the pharmacokinetics and explore the pharmacodynamics of acyclovir in plasma and oral washings of 8 subjects receiving 7 days of valacyclovir 1500 mg twice daily for EBV infectious mononucleosis. Virologic and clinical responses are assessed over 12 days. Acyclovir is measured by liquid chromatography/ultraviolet detection. EBV DNA is quantitated by TaqMan polymerase chain reaction. NONMEM VI and linear regression are used for data analysis. Acyclovir profiles in plasma and oral washings are consistent with a 1-compartment model. Final model estimates of clearance, volume of distribution, and fraction of acyclovir in oral wash supernatant are 49.9 L/h, 74.1 L, and 1.14%, respectively. The quantity of EBV DNA in oral washings and blood, and the severity of illness, measured by a graded scale, decrease during treatment. After treatment, viral rebound occurs in oral washings but not in blood, and the severity of illness continues to decline. Acyclovir pharmacokinetic parameters do not correlate with response metrics. These results support further studies of valacyclovir for EBV infectious mononucleosis.

Simultaneous determination of acyclovir, ganciclovir, and (R)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine in human plasma using high-performance liquid chromatography

Acyclovir, ganciclovir and (R)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine are active in vitro against the Epstein-Barr virus (EBV) but their in vivo anti-EBV activity is not well understood. We developed a novel, sensitive high-performance liquid chromatography assay with ultraviolet detection for measuring acyclovir, ganciclovir and (R)-9-[4-hydroxy-2-(hydroxymethyl)butyl]guanine in human plasma to identify quantitative relationships between in vitro anti-EBV activity and therapeutic response. Characteristics of the assay include a low plasma volume (200 microL), perchloric acid protein precipitation, use of penciclovir as the internal standard, run times less than 8 min and a 50 ng/mL lower limit of quantification. The within- and between-assay variability is 0.7-4.8 and 1.0-7.9%, respectively. Accuracy for all three drugs ranges from 89.5 to 106.4% for four quality controls (50, 100, 1000 and 10,000 ng/mL). This assay supports pharmacokinetic and pharmacodynamic studies of candidate anti-EBV drugs in children and adults with EBV infections.

Interfering with cellular signaling pathways enhances sensitization to combined sodium butyrate and GCV treatment in EBV-positive tumor cells

The combination of sodium butyrate (NaB) and ganciclovir (GCV) was considered to be a noteworthy therapeutic strategy in Epstein-Barr virus (EBV)-associated cancers. However, clinical studies have indicated that an extremely high dose of NaB is required to obtain the expected curative efficacy. This obviously limits the practical clinical application of the two drugs combined. In this study, we investigated the possibility of sensitizing tumor cells to NaB and GCV mediated cytotoxicity by modulating intracellular signal pathways. The results showed that the disruption of Ras/Raf activity by expressing dominant negative forms of both Ras and Raf-1 did not alter the potency of the NaB and GCV combination in the EBV-positive cell line, B95-8. However, blocking Akt activity by expressing its dominant negative form remarkably promoted NaB and GCV-mediated cytotoxicity via a thymidine kinase (TK)-independent mechanism. Interestingly, it was found that the constitutive activation of mitogen-activated protein kinase kinase kinase 1 (MEKK1) dramatically enhanced the sensitization of the cells to the combination of NaB and GCV, accompanied with an increase in TK expression in B95-8 cells. These results suggest that interfering with either the Akt or MEKK1 signaling pathway may be a useful therapeutic strategy to increase the sensitivity of EBV-positive tumor cells to the combination of NaB and GCV.

Inhibitory effects of some derivatives of glycyrrhizic acid against Epstein-Barr virus infection: structure-activity relationships

Glycyrrhizic acid (18β-GL or GL) is a herbal drug with a broad spectrum of antiviral activities and pharmacological effects and multiple sites of action. Previously we showed that GL inhibits Epstein-Barr virus (EBV) infection in vitro by interfering with an early step of the EBV replication cycle (possibly attachment/penetration). Here we tested the effects of 15 GL derivatives against EBV infection by scoring the numbers of cell expressing viral antigens and quantifying EBV DNA copy numbers in superinfected Raji cells. The derivatives were made either by transformation of GL on carboxyl and hydroxyl groups or by conjugation of amino acid residues into the carbohydrate part. We identified seven compounds active against EBV and all showed dose-dependent inhibition as determined by both assays. Among these active compounds, the introduction of amino acid residues into the GL carbohydrate part enhanced the antiviral activity in three of the seven active compounds. However, when Glu(OH)-OMe was substituted by Glu(OMe)-OMe, its antiviral activity was completely abolished. Introduction of potassium or ammonium salt to GL reduced the antiviral activity with no significant effect on cytotoxicity. The α-isomer (18α-GL) of 18β-GL was as potent as the β-form, but its sodium salt lost antiviral activity. The metabolic product of GL, 18β-glycyrrhetinic acid (18β-GA or GA), was 7.5-fold more active against EBV than its parental compound GL but, concomitantly, exhibited increased cytotoxicity resulting in a decreased therapeutic index.

Second malignancies after allogeneic hematopoietic cell transplantation

Allogeneic hematopoietic cell transplantation (allo-HCT) may prolong life and cure patients suffering from otherwise fatal diseases. However, the growing population of long-term survivors has led to the realization of multiple long-term complications, including the risk of second malignancies. Compared to the autologous setting, allo-HCT carries a much higher risk of posttransplant lymphoproliferative disorder (PTLD), which usually occurs within the first year after allo-HCT and is strongly associated with the Epstein-Barr virus (EBV). Treatment-related myelodysplastic syndromes (tMDS) and second leukemias are extremely rare. Both autologous and allo-HCT carry increased risks for second solid malignancies (SSM). The cumulative incidence of SSM continues to increase in each of the largest studies with as much as 20 years of follow-up, likely related to the long latency of radiation-related SSM. Systematic, prospective monitoring, vigilant screening processes, and well-maintained survivorship clinics and databases are absolute necessities, and should be included in the infrastructure of individual transplant centers and networks, with mandatory periodic reporting of second malignancy incidences. Primary care and transplant physicians alike must be aware of the risk of second malignancies after allo-HCT. Most importantly, guidelines should be developed in regard to screening and prevention of second malignancies, so that physicians can provide state-of-the-art counsel and care for the benefit of our patients.

A rapid DNA hybridization assay for the evaluation of antiviral compounds against Epstein-Barr virus

There is a need for additional therapies for Epstein-Barr virus (EBV) infections, but the routine screening of large numbers of potential inhibitors has been difficult due to the laborious nature of traditional assays. A new rapid assay was developed to evaluate compounds for antiviral activity against this virus that is both rapid and robust. Test compounds are added to cultures of Akata cells in 96-well plates that have been induced to undergo a lytic infection. Viral DNA produced during the infection is transferred to a membrane and quantified using a non-radioactive DNA hybridization assay. This assay was validated using a set of compounds with known activity against EBV and results compared favorably to an established real-time PCR assay. Subsequent experience with this assay has confirmed that it offers improved efficiency and robustness compared to other assays used routinely to evaluate candidate compounds for antiviral activity against EBV.

Real-time quantitative PCR for assessment of antiviral drug effects against Epstein-Barr virus replication and EBV late mRNA expression

This study assesses the ability of quantitative real-time PCR to measure the effects of virus DNA polymerase inhibitors on EBV DNA and late mRNAs syntheses in EBV-producing cell lines. In-house real-time quantitative PCRs were used to measure EBV DNA (thymidine kinase) and mRNAs (BLLF1 gene/gp350/220, BVRF2 gene/protease) in P3HR-1 and B95-8 cells induced for EBV production by PMA and exposed to ganciclovir, cidofovir and foscarnet. The calculated 50% effective concentrations (EC(50)) for viral DNA replication inhibition in P3HR-1 cells after 7 days of drug exposure were 0.28+/-0.06, 0.29+/-0.01 and 13.6+/-0.17 microg/mL for ganciclovir, cidofovir and foscarnet, respectively. The EC(50) for B95-8 cells were 0.44+/-0.02, 0.70+/-0.06 and 46.8+/-0.5 microg/mL, respectively. The quantitation of the late viral mRNAs showed a decrease of 79-89% in the mRNA amount after 4 days of antiviral treatment. Nevertheless, a substantial amount of mRNA still remained detectable after drug exposure. The real-time PCR is an improvement in the attempt to simplify EBV DNA-quantitation for antiviral assays. The quantitation of late mRNA does not appear as more informative than DNA quantitation for the assessment of the DNA polymerase inhibitor activity, but it may be useful to assess the antiviral activity of drugs acting by another mechanism.

A phase 1/2 trial of arginine butyrate and ganciclovir in patients with Epstein-Barr virus-associated lymphoid malignancies

Malignancies associated with latent Epstein-Barr virus (EBV) are resistant to nucleoside-type antiviral agents because the viral enzyme target of these antiviral drugs, thymidine kinase (TK), is not expressed. Short-chain fatty acids, such as butyrate, induce EBV-TK expression in latently infected B cells. As butyrate has been shown to sensitize EBV(+) lymphoma cells in vitro to apoptosis induced by ganciclovir, arginine butyrate in combination with ganciclovir was administered in 15 patients with refractory EBV(+) lymphoid malignancies to evaluate the drug combination for toxicity, pharmacokinetics, and clinical responses. Ganciclovir was administered twice daily at standard doses, and arginine butyrate was administered by continuous infusion in an intrapatient dose escalation, from 500 mg/(kg/day) escalating to 2000 mg/(kg/day), as tolerated, for a 21-day cycle. The MTD for arginine butyrate in combination with ganciclovir was established as 1000 mg/(kg/day). Ten of 15 patients showed significant antitumor responses, with 4 CRs and 6 PRs within one treatment cycle. Complications from rapid tumor lysis occurred in 3 patients. Reversible somnolence or stupor occurred in 3 patients at arginine butyrate doses of greater than 1000 mg/(kg/day). The combination of arginine butyrate and ganciclovir was reasonably well-tolerated and appears to have significant biologic activity in vivo in EBV(+) lymphoid malignancies which are refractory to other regimens.

Ganciclovir augments the lytic induction and apoptosis induced by chemotherapeutic agents in an Epstein-Barr virus-infected gastric carcinoma cell line

Epstein-Barr virus is an oncogenic herpesvirus and has been associated with several human malignancies, including gastric cancer. In Epstein-Barr virus-associated gastric cancer, Epstein-Barr virus is found in virtually all tumor cells, but rarely in normal epithelial cells, thus implying that Epstein-Barr virus-targeting therapies are likely to be an effective treatment strategy. Using the SNU-719 gastric cancer cell line, which is naturally infected with Epstein-Barr virus, we found that the chemotherapeutic agents, such as 5-fluorouracil, cis-platinum and taxol, induced the expressions of BMRF1, BZLF1 and BRLF1 proteins that are usually found in the lytic form of the virus. This effect was found to require various signal transduction pathways involving phosphatidylinositol 3' kinase, mitogen-activated protein/extracellular signal-regulated kinase, protein kinase C delta and p38 mitogen-activated protein kinase. Moreover, the combination of ganciclovir with these agents increased the lytic transformation and induced apoptosis in Epstein-Barr virus-associated gastric carcinoma. We conclude that ganciclovir enhances the therapeutic efficacy of 5-fluorouracil, cis-platinum and taxol in Epstein-Barr virus-positive gastric cancer cells. It is hoped that this information will be found useful during the establishment of treatment strategies for Epstein-Barr virus-associated gastric cancer.

Lytic induction and apoptosis of Epstein-Barr virus-associated gastric cancer cell line with epigenetic modifiers and ganciclovir

Epstein-Barr virus (EBV) is an oncogenic herpes virus. EBV gene transcription is regulated by an epigenetic mechanism to establish a persistent infection and to evade the host immune system. We found that low concentrations of epigenetic modifying agents, 5-aza-2'-deoxycytidine (5-aza-CdR) or trichostatin A (TSA), induced the expression of BMRF1, BZLF1, and BRLF1 genes, which are found in the lytic form of the virus, in an EBV-positive gastric cancer cell line. This effect did not involve PI3 kinase, MAP/ERK kinase, protein kinase C delta, or p38 MAPK signaling pathway. The cytotoxic effect of ganciclovir (GCV) was enhanced after the lytic induction by epigenetic modifiers, and the combination of GCV and epigenetic modifiers induced apoptosis, which is dependent on caspases. In conclusion, the combination of GCV with 5-aza-CdR or TSA might be a useful therapeutic strategy for EBV-induced human gastric cancer.

Ganciclovir is associated with low or undetectable Epstein-Barr virus DNA load in cerebrospinal fluid of patients with HIV-related primary central nervous system lymphoma

BACKGROUND

Epstein-Barr virus (EBV) is pathogenically linked to human immunodeficiency virus (HIV)-related primary central nervous system lymphoma (PCNSL) and is found in virtually all HIV-related PCNSL cases. The objective of this study was to assess the effect of ganciclovir on EBV DNA replication in patients with HIV-related PCNSL.

PATIENTS AND METHODS

EBV DNA was measured by real-time polymerase chain reaction in cerebrospinal fluid and plasma samples from 25 patients with HIV-related PCNSL. Eight of these patients were receiving ganciclovir for concurrent cytomegalovirus infections.

RESULTS

EBV DNA was detected in cerebrospinal fluid samples obtained from 15 (88%) of 17 ganciclovir-untreated patients and 4 (50%) of 8 ganciclovir-treated patients (P = .028). EBV DNA load was significantly lower for treated patients, compared with untreated patients (median value, 2.15 vs. 4.16 log copies/mL; P = .001). Analysis of sequential cerebrospinal fluid samples from 7 patients showed that EBV DNA decreased in samples obtained from 2 patients following the start of ganciclovir administration but did not decrease in samples obtained from the 5 untreated patients. In addition, patients who received ganciclovir survived longer than the untreated patients (median duration of survival, 181 vs. 72 days; P = .006).

CONCLUSION

The effect of ganciclovir on EBV DNA load in cerebrospinal fluid supports the hypothesis that EBV is replicating in patients with PCNSL. This observation, together with the effect of ganciclovir therapy on patient survival, suggests that this drug might be useful for the management of PCNSL.

Quantitative EBV viral loads and immunosuppression alterations can decrease PTLD incidence in pediatric liver transplant recipients

Epstein-Barr virus (EBV) is a common viral infection in pediatric liver transplant patients and can lead to development of post-transplant lymphoproliferative disorder (PTLD). Differing studies have used immunosuppression reduction, antiviral medications or i.v. CMV-immunogloublin for EBV prevention and treatment. The purpose of this study was to determine whether implementation of a protocol for frequent EBV monitoring and EBV viral load-driven immunosuppression reduction could decrease the incidence of PTLD in our patient population. All data were prospectively collected between 2001 and 2004 at a single institution. Seventy-three patients were entered into the study. Patients were divided into a historical control group (pre-2001, 30 patients) and a treatment group (post-2001, 43 patients). Approximately 1271 blood samples of 73 patients were collected between 2001 and 2004. Eleven out of 43 patients received immunosuppression tapering due to high EBV viral loads (>4000 copies/microg DNA). One patient developed allograft rejection after immunosuppression modulation. Prior to 2001, the incidence of PTLD at our institution was 16%. After instituting a protocol for EBV monitoring, the incidence of PTLD decreased to 2% (p-value<0.05). These findings illustrate that frequent EBV viral load monitoring and preemptive immunosuppression modulation have an integral role in preventing PTLD in the pediatric liver transplant population.

Impaired transporter associated with antigen processing-dependent peptide transport during productive EBV infection

Human herpesviruses, including EBV, persist for life in infected individuals. During the lytic replicative cycle that is required for the production of infectious virus and transmission to another host, many viral Ags are expressed. Especially at this stage, immune evasion strategies are likely to be advantageous to avoid elimination of virus-producing cells. However, little is known about immune escape during productive EBV infection because no fully permissive infection model is available. In this study, we have developed a novel strategy to isolate populations of cells in an EBV lytic cycle based on the expression of a reporter gene under the control of an EBV early lytic cycle promoter. Thus, induction of the viral lytic cycle in transfected EBV(+) B lymphoma cells resulted in concomitant reporter expression, allowing us, for the first time, to isolate highly purified cell populations in lytic cycle for biochemical and functional studies. Compared with latently infected B cells, cells supporting EBV lytic cycle displayed down-regulation of surface HLA class I, class II, and CD20, whereas expression levels of other surface markers remained unaffected. Moreover, during lytic cycle peptide transport into the endoplasmic reticulum, was reduced to <30% of levels found in latent infection. Because steady-state levels of TAP proteins were unaffected, these results point toward EBV-induced interference with TAP function as a specific mechanism contributing to the reduced levels of cell surface HLA class I. Our data implicate that EBV lytic cycle genes encode functions to evade T cell recognition, thereby creating a window for the generation of viral progeny.

Suppression of EBV release from irradiated B lymphoblastoid cell-lines: superior activity of ganciclovir compared with acyclovir

BACKGROUND

B lymphoblastoid cell-lines (BLCL), generated by exposure of PBMC to a laboratory strain of EBV, are commonly utilized in the preparation of T cells used for immunotherapy. Although most B cells are latently infected, BLCL contain a subset of cells that harbor infectious virus, which could be released into the infusion product during preparation. To reduce this known risk, laboratories have pretreated BLCL for > or = 14 days with 100 microM acyclovir (ACV), an inhibitor of viral DNA polymerase, prior to use. We tested the effectiveness of ACV in preventing the release of infectious virus from irradiated fresh and previously frozen BLCL, and compared its effects with those of ganciclovir (GCV).

METHODS

BLCL were grown for 14 days in medium containing various doses of ACV or GCV, washed, irradiated, and tested for the presence of infectious virus in co-culture assays with cord blood mononuclear cells(CBMC) (21 CBMC to BLCL). B-cell transformation was assessed at 3-4 weeks of culture.

RESULTS

Both fresh and previously frozen BLCL released infectious virus, which transformed nearly all (92%) of CBMC co-cultures (n = 52). Transformation was not prevented by treatment with 100 microM ACV (88%, n = 52). Increasing the ACV dose to 200 microM (or 50 microg/mL) still allowed transformation in 4/9 (44%) cultures, while this and higher doses severely reduced the proliferation rate of the BLCL during ACV exposure. Infectious virus release was detectable within 1 day of ACV removal and BLCL irradiation. In contrast, GCV was able to prevent infectious virus release in 12/12 co-cultures at a concentration (15 microM) that only modestly reduced BLCL growth.

DISCUSSION

These results indicate that GCV is more effective at preventing release of infectious EBV from irradiated BLCL than ACV at concentrations that do not severely inhibit B-cell growth.

Lytic induction therapy for Epstein-Barr virus-positive B-cell lymphomas

A novel therapy for Epstein-Barr virus (EBV)-positive tumors involves the intentional induction of the lytic form of EBV infection combined with ganciclovir (GCV) treatment. Virally encoded kinases (thymidine kinase and BGLF4) which are expressed only during the lytic form of infection convert GCV (a nucleoside analogue) into its active, cytotoxic form. However, tightly latent EBV infection in B cells has made it difficult to identify drugs that can be used clinically to induce lytic viral infection in B-cell lymphomas. Here we demonstrate that gemcitabine and doxorubicin (but not 5-azacytidine, cis-platinum, or 5-fluorouracil) induce lytic EBV infection in EBV-transformed B cells in vitro and in vivo. Gemcitabine and doxorubicin both activated transcription from the promoters of the two viral immediate-early genes, BZLF1 and BRLF1, in EBV-negative B cells. This effect required the EGR-1 motif in the BRLF1 promoter and the CRE (ZII) and MEF-2D (ZI) binding sites in the BZLF1 promoter. GCV enhanced cell killing by gemcitabine or doxorubicin in lymphoblastoid cells transformed with wild-type EBV, but not in lymphoblastoid cells transformed by a mutant virus (with a deletion in the BZLF1 immediate-early gene) that is unable to enter the lytic form of infection. Most importantly, the combination of gemcitabine or doxorubicin and GCV was significantly more effective for the inhibition of EBV-driven lymphoproliferative disease in SCID mice than chemotherapy alone. In contrast, the combination of zidovudine and gemcitabine was no more effective than gemcitabine alone. These results suggest that the addition of GCV to either gemcitabine- or doxorubicin-containing chemotherapy regimens may enhance the therapeutic efficacy of these drugs for EBV-driven lymphoproliferative disease in patients.

Contrasting roles of dendritic cells and B cells in the immune control of Epstein-Barr virus

The human gamma-herpesvirus, Epstein-Barr virus (EBV), has growth-transforming potential in vivo and in vitro. Despite this, most healthy carriers remain free of EBV-associated malignancies because of effective T cell-mediated immune control of the virus. A better understanding of these highly efficient control mechanisms is important in the development of new treatment strategies for EBV-associated malignancies. A rational approach to EBV immunotherapy requires answering two questions about the initiation of the protective EBV-specific immune response. The first question is, what is the antigen-presenting cell responsible for priming EBV specific immunity? Second, which viral antigen is central to protective EBV adaptive immunity seen in healthy carriers of the virus? We provide evidence in this review that dendritic cells rather than EBV-transformed B cells are responsible for orchestrating protective EBV immunity and that the EBV nuclear antigen 1 (EBNA1)-specific CD4+ T cell response probably plays a role in resistance against all types of EBV-associated malignancies in healthy carriers. This implies that EBNA1 targeting to dendritic cells should be a component of vaccine and immunotherapy development against EBV-associated malignancies.

Mechanism of action of glycyrrhizic acid in inhibition of Epstein-Barr virus replication in vitro

We report here that glycyrrhizic acid (GL), a component of licorice root (Glycyrrhiza radix), is active against EBV replication in superinfected Raji cells in a dose-dependent fashion. The IC(50) values for viral inhibition and cell growth were 0.04 and 4.8mM, respectively. The selectivity index (ratio of IC(50) for cell growth to IC(50) for viral DNA synthesis) was 120. Time of addition experiments suggested that GL interferes with an early step of EBV replication cycle (possibly penetration). GL had no effect on viral adsorption, nor did it inactivate EBV particles. Thus, GL represents a new class of anti-EBV compounds with a mode of action different from that of the nucleoside analogs that inhibit viral DNA polymerase.

Epstein-Barr virus and post-transplant lymphoproliferative disease

There is convincing evidence that Epstein-Barr virus (EBV) is associated with post-transplant lymphoproliferative disease (PTLD). Primary EBV infection following transplantation occurs in as many as 90% of cases of PTLD in children and pretransplant EBV seronegativity is a recognized risk factor for developing PTLD. Other risk factors include young age at the time of transplant, the type of transplant that the recipient receives and the type and intensity of immunosuppression. The clinical presentation is often nonspecific and tissue biopsy is necessary to establish the diagnosis. There appears to be a correlation between PTLD and EBV viral load measured by polymerase chain reaction (PCR) of the peripheral blood and quantitative PCR may be a useful guide in the management of PTLD. Antiviral drugs and cytomegalovirus-immunoglobulin G may have a role in preventing PTLD. Because PTLD results from functional over-immunosuppression, the initial treatment is reduction of immunosuppression. Antiviral agents, interferon, immuno-based monoclonal therapy, cell-based therapy and chemotherapy also have a potential role in treating this disorder. At the present time there is no standardized approach to the evaluation and treatment of PTLD.

The lytic cycle of Epstein-Barr virus is associated with decreased expression of cell surface major histocompatibility complex class I and class II molecules

Human herpesviruses utilize an impressive range of strategies to evade the immune system during their lytic replicative cycle, including reducing the expression of cell surface major histocompatibility complex (MHC) and immunostimulatory molecules required for recognition and lysis by virus-specific cytotoxic T cells. Study of possible immune evasion strategies by Epstein-Barr virus (EBV) in lytically infected cells has been hampered by the lack of an appropriate permissive culture model. Using two-color immunofluorescence staining of cell surface antigens and EBV-encoded lytic cycle antigens, we examined EBV-transformed B-cell lines in which a small subpopulation of cells had spontaneously entered the lytic cycle. Cells in the lytic cycle showed a four- to fivefold decrease in cell surface expression of MHC class I molecules relative to that in latently infected cells. Expression of MHC class II molecules, CD40, and CD54 was reduced by 40 to 50% on cells in the lytic cycle, while no decrease was observed in cell surface expression of CD19, CD80, and CD86. Downregulation of MHC class I expression was found to be an early-lytic-cycle event, since it was observed when progress through late lytic cycle was blocked by treatment with acyclovir. The immediate-early transactivator of the EBV lytic cycle, BZLF1, did not directly affect expression of MHC class I molecules. However, BZLF1 completely inhibited the upregulation of MHC class I expression mediated by the EBV cell-transforming protein, LMP1. This novel function of BZLF1 elucidates the paradox of how MHC class I expression can be downregulated when LMP1, which upregulates MHC class I expression in latent infection, remains expressed in the lytic cycle.

Biosynthetic ganciclovir triphosphate: its isolation and characterization from ganciclovir-treated herpes simplex thymidine kinase-transduced murine cells

A method is described for the preparation of ganciclovir triphosphate (GCV-TP) using murine colon cancer cells (MC38) transduced with the herpes simplex virus-thymidine kinase (MC38/HSV-tk). Murine cells transduced with viral-tk contain required viral and host enzymes needed for complete cellular synthesis of this potent antiviral metabolite. Dose response studies showed optimal intracellular levels of GCV-TP occurred after exposure of MC38/HSV-tk cells to 300 microM ganciclovir for 24 h producing 7.5 nmol GCV-TP/10(6) cells. This reflects cellular accumulation of GCV-TP to levels 25-fold greater than the medium concentration of parent drug. A simple isolation scheme included methanolic extraction and anion-exchange chromatography to recover the target triphosphate. Mass spectral analysis and selective enzyme degradation provided structural confirmation of the purified product. Biological activity of the purified GCV-TP was demonstrated by competitive inhibition experiments using human DNA polymerase alpha and HSV DNA polymerase that showed substantially greater sensitivity for the viral polymerase in agreement with previous reports. The GCV-TP obtained was further used to enzymatically prepare GCV mono- and diphosphate in high yield. This method provides an easily scalable means of preparing milligram amounts of the triphosphates of pharmacologically active acyclic nucleosides like ganciclovir.

Induction of the Epstein-Barr virus thymidine kinase gene with concomitant nucleoside antivirals as a therapeutic strategy for Epstein-Barr virus-associated malignancies

Lymphoproliferative diseases (LPDs) associated with the Epstein-Barr virus (EBV) include non-Hodgkin lymphomas, which occur in the setting of immunosuppression, including that induced by human immunodeficiency virus, and posttransplant lymphoproliferative disorders. These LPDs are characterized by actively proliferating, latently infected EBV-positive B lymphocytes and often follow a rapidly progressive fatal clinical course. Pharmacologic treatment for herpesvirus infections has targeted the virus-specific enzyme, thymidine kinase (TK), with nucleoside analogs. The lack of viral TK expression in EBV-positive tumors, caused by viral latency, however, makes antiviral therapy alone ineffective as an antineoplastic therapy. Arginine butyrate selectively activates the EBV TK gene in latently infected EBV-positive tumor cells. We have developed a strategy for treatment of EBV-associated lymphomas using pharmacologic induction of the latent viral TK gene and enzyme in tumor cells using arginine butyrate, followed by treatment with ganciclovir. A phase I/II trial, using an intrapatient dose escalation of arginine butyrate combined with ganciclovir, is underway. This combination therapy has produced complete clinical responses in 5 of 10 previously refractory patients, with partial responses occurring in 2 additional patients. This virus-targeted antitumor strategy may provide a new therapeutic approach to EBV-associated neoplasms.

Epstein--Barr virus post-transplant lymphoproliferative disease and virus-specific therapy: pharmacological re-activation of viral target genes with arginine butyrate

Lymphoproliferative disorders associated with the Epstein-Barr virus (EBV) include non-Hodgkin's lymphoma, Hodgkin's lymphoma, and "post-transplant lymphoproliferative disorders" (PTLD), which occur with immunosuppression after marrow and organ transplantation. PTLD is characterized by actively proliferating, latently infected EBV(+) B-lymphocytes, and often manifests a rapidly progressive fatal clinical course if the immunosuppression cannot be reversed. Lung transplant recipients are a subset of patients at special risk for developing PTLD. The incidence of PTLD development in these patients has been estimated at 5--10%. Whereas immunologic and antiviral therapy have been moderately effective for treating EBV-associated infections in the lytic phase, they have been less useful in the more common latent phase of the disease. One common treatment for herpesvirus infections has targeted the virus-specific enzyme thymidine kinase (TK). The lack of viral TK expression in EBV(+) tumor cells, due to viral latency, makes anti-viral therapy alone ineffective as an anti-neoplastic therapy, however. We have developed a strategy for the treatment of EBV-associated lymphomas/PTLD using pharmacologic induction of the latent viral TK gene and enzyme in the tumor cells, followed by treatment with ganciclovir. Arginine butyrate selectively activates the EBV TK gene in latently EBV-infected human lymphoid cells and tumor cells. A Phase I/II trial has been initiated, employing an intra-patient dose escalation of arginine butyrate combined with ganciclovir. In six patients with EBV-associated lymphomas or PTLD, all of which were resistant to conventional radiation and/or chemotherapy, this combination produced complete clinical responses in four of six patients, with a partial response occurring in a fifth patient. Pathologic examination in two of three patients demonstrated complete necrosis of the EBV lymphoma, with no residual disease, following a single three-week course of the combination therapy. Possible side-effects of the therapy included nausea and reversible lethargy at the highest doses. One patient suffered acute liver failure, thought to be secondary to release of FasL from the necrotic tumor. Analysis of patient-derived tumor cells in culture demonstrated that arginine butyrate produced selective induction of the EBV TK gene, which then conferred sensitivity to ganciclovir, resulting in tumor apoptosis. Additional patient accrual is sought for further evaluation of this therapy.

Diagnosis and management of posttransplant lymphoproliferative disorder in solid-organ transplant recipients

The Epstein-Barr virus (EBV) has a pivotal pathophysiologic role in the development of most lymphoproliferative disorders that occur after solid-organ transplantation. The term "EBV-associated posttransplant lymphoproliferative disorder" (PTLD) includes all clinical syndromes of EBV-associated lymphoproliferation, ranging from uncomplicated posttransplant infectious mononucleosis to true malignancies that contain clonal chromosomal abnormalities. PTLDs are historically associated with a high mortality rate in patients who have a monoclonal form of the disorder. Recently described approaches to pathology, diagnosis, treatment, and preventive strategies of PTLD, however, have the potential to improve outcome.

The role of antiviral and immunoglobulin therapy in the prevention of Epstein-Barr virus infection and post-transplant lymphoproliferative disease following solid organ transplantation

The recognition of the importance of Epstein-Barr virus (EBV) infection, including EBV-associated post-transplant lymphoproliferative disease (PTLD), has led to a new focus on the prevention of this problem. This paper reviews the scientific rationale behind, and clinical experience with, the use of chemoprophylaxis (using acyclovir or ganciclovir) and immunoprophylaxis (using intravenous immunoglobulin) in the prevention of EBV/PTLD. While some centers have already introduced the use of one or both of these agents as standard prophylaxis against the development of this complication, published data in support of these protocols are currently lacking. Well designed clinical trials are necessary to evaluate the potential role of both antiviral and immunoglobulin agents in the prevention of EBV/PTLD in organ transplant recipients.

Methylation of transcription factor binding sites in the Epstein-Barr virus latent cycle promoter Wp coincides with promoter down-regulation during virus-induced B-cell transformation

Two Epstein-Barr virus latent cycle promoters for nuclear antigen expression, Wp and Cp, are activated sequentially during virus-induced transformation of B cells to B lymphoblastoid cell lines (LCLs) in vitro. Previously published restriction enzyme studies have indicated hypomethylation of CpG dinucleotides in the Wp and Cp regions of the viral genome in established LCLs, whereas these same regions appeared to be hypermethylated in Burkitt's lymphoma cells, where Wp and Cp are inactive. Here, using the more sensitive technique of bisulfite genomic sequencing, we reexamined the situation in established LCLs with the typical pattern of dominant Cp usage; surprisingly, this showed substantial methylation in the 400-bp regulatory region upstream of the Wp start site. This was not an artifact of long-term in vitro passage, since, in cultures of recently infected B cells, we found progressive methylation of Wp (but not Cp) regulatory sequences occurring between 7 and 21 days postinfection, coincident with the period in which dominant nuclear antigen promoter usage switches from Wp to Cp. Furthermore, in the equivalent in vivo situation, i.e., in the circulating B cells of acute infectious mononucleosis patients undergoing primary EBV infection, we again frequently observed selective methylation of Wp but not Cp sequences. An effector role for methylation in Wp silencing was supported by methylation cassette assays of Wp reporter constructs and by bandshift assays, where the binding of two sets of transcription factors important for Wp activation in B cells, BSAP/Pax5 and CREB/ATF proteins, was shown to be blocked by methylation of their binding sites.

Modern immunosuppression

The current treatment of posttransplant lymphoproliferative disease (PTLD) includes prophylaxis at the time of transplant, decreasing or stopping immunosuppresion and initiation of antiviral therapy in patients with polymerase chain reaction or clinical evidence of PTLD, and judicial reintroduction of immunosuppression in patients who have cleared their PTLD and have begun to have rejection. The pharmacology, pharmacokinetics, notable side effects, and toxicities of the immunosuppressive agents are described in this article. At the conclusion of each section the author's current practice with these agents and treatment strategies are described.

Value of long-term administration of acyclovir and similar agents for protecting against AIDS-related lymphoma: case-control and historical cohort studies

Acyclovir or similar agents with activity against Epstein-Barr virus (EBV) theoretically may prevent non-Hodgkin's lymphoma (NHL) in AIDS. A case-control study of 29 patients with AIDS-related NHL and 58 matched control subjects assessed the frequency with which daily acyclovir (>/=800 mg/d) or similar agents were used for > or =1 year. In a historical cohort of 304 patients with AIDS for > or =2 years, the prevalence of NHL was assessed among 3 groups of patients: those who received long-term treatment with high-dose acyclovir (or similar agents) or low-dose or intermittent acyclovir; those treated with ganciclovir/foscarnet for <1 year; and those who had not previously been treated with acyclovir, ganciclovir, or foscarnet. In the case-control study, 22 patients (72.4%) with NHL never received acyclovir or similar drugs versus 19 control subjects (32.8%; P=. 002); 2 patients (6.9%) with NHL received acyclovir (> or =800 mg/d) for > or =1 year versus 27 (46.6%) of control subjects (P=.0001). In the cohort study, 6 (6.8%) of 88 patients who received acyclovir (> or =800 mg/d) for > or =1 year developed NHL versus 15 (15.5%) of 97 patients who received intermittent or lower-dose acyclovir and 30 (25.2%) of 119 patients who never received these agents (P=.002). Long-term administration (>1 year) of high-dose acyclovir or similar agents with anti-EBV activity may prevent NHL in patients with AIDS. A prospective, randomized study is warranted to confirm these results.

Antiviral activity of ganciclovir elaidic acid ester against herpesviruses

A fatty acid derivative of ganciclovir (GCV), elaidic acid ganciclovir (E-GCV), has been evaluated for its inhibitory activity against laboratory and clinical strains of herpes simplex type 1 (HSV-1) and type 2 (HSV-2), varicella-zoster virus (VZV) and human cytomegalovirus (HCMV) in human embryonic lung fibroblasts. GCV, cidofovir, acyclovir (ACV), brivudin (BVDU) and foscarnet (PFA) were included as reference compounds. The viruses studied were wild-type, thymidine kinase-deficient (TK(-)) and PFA-resistant (PFA(r)) HSV strains. The IC(50) values obtained for E-GCV were 5- to 30-fold lower than those observed for GCV, the IC(50) value of E-GCV for HSV-1 strain KOS being 0.07 nM. A similarly increased activity of E-GCV (as compared to GCV) was noted for TK(-) and PFA(r) HSV-1 or HSV-2 strains. However, E-GCV did not exhibit superior activity over GCV to VZV or HCMV in vitro. The antiviral efficacy of E-GCV was also evaluated in vivo against intracerebral HSV-2 infection in NMRI mice. Animals were treated intraperitoneally or perorally with E-GCV, GCV or placebo once daily for 10 days, starting the day of infection. E-GCV compared to GCV at equimolar doses, proved markedly more efficacious than GCV in terms of reduction of mortality rate and delay of mean time of death. The elaidic acid ester of GCV should therefore be considered as a novel approach towards the treatment of HSV infections.

Inhibitory effect of cycloSaligenyl-nucleoside monophosphates (cycloSal-NMP) of acyclic nucleoside analogues on HSV-1 and EBV

The in vitro antiviral activity of a new series of cycloSal-pro-nucleotides derived from the acyclic nucleoside analogues aciclovir and penciclovir against herpes simplex virus type 1 (HSV-1), thymidine kinase deficient (TK-) HSV-1, and Epstein-Barr virus (EBV) was evaluated. Using the XTT-based tetrazolium reduction assay EZ4U, the cycloSal derivatives were examined for their antiviral and cytotoxic effects in HSV-1 as well as HSV-1-TK--infected Vero cells. The anti-EBV activity was assessed by means of an EBV DNA hybridization assay using a digoxigenin-labeled probe specific for the Bam H1-W-fragment of the EBV genome and by measuring viral capsid antigen (VCA) expression in P3HR-1 cells by indirect immunofluorescence. Among the new cycloSal-phosphotriesters the three aciclovir monophosphates proved to be potent and selective inhibitors of HSV-1 replication, EBV DNA synthesis and EB-VCA expression. Of interest is the retention of activity of the aciclovir monophosphates in HSV-1-TK--infected cells. Particularly 3-methyl-cycloSal-aciclovir monophosphate retained the same effectiveness, as compared to the wild type virus strain. In contrast to the aciclovir pro-nucleotides the penciclovir cycloSal-phosphotriesters exhibited at best only a marginal antiviral effect on HSV and EBV replication.

The management of Epstein-Barr virus associated post-transplant lymphoproliferative disorders in pediatric solid-organ transplant recipients

Despite a growing understanding of the pathogenesis and spectrum of Epstein-Barr virus (EBV) and EBV-associated post-transplant lymphoproliferative disease (PTLD) in organ transplant recipients, the optimal management of this complication remains controversial. The absence of comparative data evaluating potential therapeutic strategies explains the lack of uniformly accepted guidelines for the management of PTLD. The purpose of this review is to provide an overview of potential therapies and offer a set of guidelines for the management of EBV-associated PTLD in children.

Inhibition of Epstein-Barr virus replication by a benzimidazole L-riboside: novel antiviral mechanism of 5, 6-dichloro-2-(isopropylamino)-1-beta-L-ribofuranosyl-1H-benzimidazole

Although a number of antiviral drugs inhibit replication of Epstein-Barr virus (EBV) in cell culture, and acyclovir (ACV) suppresses replication in vivo, currently available drugs have not proven effective for treatment of EBV-associated diseases other than oral hairy leukoplakia. Benzimidazole riboside compounds represent a new class of antiviral compounds that are potent inhibitors of human cytomegalovirus (HCMV) replication but not of other herpesviruses. Here we characterize the effects of two compounds in this class against lytic replication of EBV induced in a Burkitt lymphoma cell line latently infected with EBV. We analyzed linear forms of EBV genomes, indicative of lytic replication, and episomal forms present in latently infected cells by terminal probe analysis followed by Southern blot hybridization as well as the high-molecular-weight unprocessed viral DNA by pulsed-field gel electrophoresis. D-Ribofuranosyl benzimidazole compounds that act as inhibitors of HCMV DNA maturation, including BDCRB (5, 6-dichloro-2-bromo-1-beta-D-ribofuranosyl-1H-benzimidazole), did not affect the accumulation of high-molecular-weight or monomeric forms of EBV DNA in the induced cells. In contrast, the generation of linear EBV DNA as well as precursor viral DNA was sensitive to the L-riboside 1263W94 [5, 6-dichloro-2-(isopropylamino)-1-beta-L-ribofuranosyl-1H-benzimidazole]. The 50% inhibitory concentration range for 1263W94 was 0.15 to 1. 1 microM, compared with 10 microM for ACV. Thus, 1263W94 is a potent inhibitor of EBV. In addition, 1263W94 inhibited the phosphorylation and the accumulation of the essential EBV replicative cofactor, early antigen D.

Serial measurement of Epstein-Barr viral load in peripheral blood in pediatric liver transplant recipients during treatment for posttransplant lymphoproliferative disease

BACKGROUND

Few data are available describing the natural history of the Epstein-Barr virus (EBV) viral load after the diagnosis of EBV-associated posttransplant lymphoproliferative disease (PTLD). Accordingly, we prospectively followed the EBV viral load after the diagnosis of EBV/PTLD in seven pediatric orthotopic liver transplant recipients.

METHODS

EBV viral loads were serially measured by quantitative competitive polymerase chain reaction of the peripheral blood from pediatric patients with PTLD and correlated with the clinical course of these children. Viral loads >200 genome copies/10(5) peripheral blood lymphocytes were considered consistent with an increased risk of PTLD. Viral loads <200 obtained during treatment for PTLD were considered evidence of "clearance" of EBV; subsequent loads >200 were considered evidence of virologic "rebound."

RESULTS

The mean EBV viral load at the time of diagnosis of PTLD was 1029. All patients "cleared" their EBV viral load during the treatment of PTLD; patient and graft survival in this series was 100%. The mean time to clearance of EBV from the peripheral blood (18.8 days) was similar to the mean time to onset of first rejection (13.8 days). EBV viral load at the time of diagnosis of rejection after PTLD was always <100. A rebound in the EBV viral load to >200 was noted in five of seven patients a median of 3.5 months (range 2.3-13 months) after the diagnosis of EBV/PTLD. However, none of these children has had any evidence of PTLD recurrence.

CONCLUSIONS

Clearance of the EBV viral load from the peripheral blood seems to correlate with restoration of the host's immune response as noted both by the regression of the PTLD and the onset of rejection. Late rebound of the EBV viral load is common and does not seem to predict disease recurrence.

Prevention and preemptive therapy of postransplant lymphoproliferative disease in pediatric liver recipients

BACKGROUND

We have previously reported a 10% incidence of posttransplant lymphoproliferative disease (PTLD) in pediatric patients receiving first liver grafts and primarily immunosuppressed with tacrolimus. To decrease the incidence of PTLD, we developed a protocol utilizing preemptive intravenous ganciclovir in high-risk recipients (i.e., donor (D)+, recipient (R)-), combined with serial monitoring of peripheral blood for Epstein Barr virus (EBV) by polymerase chain reaction (PCR).

METHODS

Consecutive pediatric recipients of a first liver graft were immunosuppressed with oral tacrolimus (both induction and maintenance), and low-dose prednisone. EBV serologies were obtained at the time of orthotopic liver transplant in recipients and donors. Recipients were divided into groups: group 1, high-risk (D+R-), and group 2, low-risk (D+R+; D-R-; D-R+). In group 1 (high-risk), all patients received a minimum of 100 days of intravenous ganciclovir (6-10 mg/kg/day), while, in group 2 (low-risk), patients received intravenous ganciclovir during their initial hospitalization and then were converted to oral acyclovir (40 mg/kg/day) at discharge. Semiquantitative EBV-PCR determinations were made at 1-2-month intervals. In both groups, patients with an increasing viral copy number by EBV-PCR had tacrolimus levels decreased to 2-5 ng/ml. Tacrolimus was stopped, and intravenous ganciclovir reinstituted for PTLD. A positive EBV-PCR with symptoms, but negative histology, was defined as EBV disease; PTLD was defined as histologic evidence of polyclonal or monoclonal B cell proliferation.

RESULTS

Forty children who had survived greater than 2 months were enrolled. There were 18 children in group 1 (high-risk; mean age of 14+/-15 months and mean follow-up time of 243+/-149 days) and 22 children in group 2 (low-risk; mean age of 64+/-65 months and follow-up time of 275+/-130 days). In group 1 (high-risk), there was no PTLD and one case of EBV disease (mononucleosis-like syndrome), which resolved. In group 2 (low-risk), there were two cases of PTLD; both resolved when tacrolimus was stopped. Both children were 8 months old at time of transplant. Neither received OKT3, and they had one and two episodes of steroid-sensitive rejection, respectively. One child had EBV disease (mild hepatitis), which resolved.

CONCLUSIONS

Since instituting this protocol, the overall incidence of PTLD has fallen from 10% to 5% for children receiving primary tacrolimus therapy after OLT. No high-risk pediatric liver recipient treated preemptively with intravenous ganciclovir developed PTLD. Both children with PTLD were less than 1 year at OLT and considered low-risk. However, their positive EBV antibody titers may have been maternal in origin and not have offered long-term protection. Serial monitoring of EBV-PCR after pediatric OLT is recommended to decrease the risk of PTLD by allowing early detection of EBV infection, which is then managed by decreasing immunosuppression and continuing intravenous ganciclovir.