Acyclovir and Epstein-Barr virus infection

Cytokine Storm Syndromes Associated with Epstein-Barr Virus

Epstein-Barr virus (EBV) is a ubiquitous and predominantly B cell tropic virus. One of the most common viruses to infect humans, EBV, is best known as the causative agent of infectious mononucleosis (IM). Although most people experience asymptomatic infection, EBV is a potent immune stimulus and as such it elicits robust proliferation and activation of the B-lymphocytes it infects as well as the immune cells that respond to infection. In certain individuals, such as those with inherited or acquired defects affecting the immune system, failure to properly control EBV leads to the accumulation of EBV-infected B cells and EBV-reactive immune cells, which together contribute to the development of often life-threatening cytokine storm syndromes (CSS). Here, we review the normal immune response to EBV and discuss several CSS associated with EBV, such as chronic active EBV infection, hemophagocytic lymphohistiocytosis, and post-transplant lymphoproliferative disorder. Given the critical role for cytokines in driving inflammation and contributing to disease pathogenesis, we also discuss how targeting specific cytokines provides a rational and potentially less toxic treatment for EBV-driven CSS.

EBV-associated diseases: Current therapeutics and emerging technologies

EBV is a prevalent virus, infecting >90% of the world's population. This is an oncogenic virus that causes ~200,000 cancer-related deaths annually. It is, in addition, a significant contributor to the burden of autoimmune diseases. Thus, EBV represents a significant public health burden. Upon infection, EBV remains dormant in host cells for long periods of time. However, the presence or episodic reactivation of the virus increases the risk of transforming healthy cells to malignant cells that routinely escape host immune surveillance or of producing pathogenic autoantibodies. Cancers caused by EBV display distinct molecular behaviors compared to those of the same tissue type that are not caused by EBV, presenting opportunities for targeted treatments. Despite some encouraging results from exploration of vaccines, antiviral agents and immune- and cell-based treatments, the efficacy and safety of most therapeutics remain unclear. Here, we provide an up-to-date review focusing on underlying immune and environmental mechanisms, current therapeutics and vaccines, animal models and emerging technologies to study EBV-associated diseases that may help provide insights for the development of novel effective treatments.

Clinical characteristics and effectiveness of antiviral agents in hospitalized children with infectious mononucleosis in China: A multicenter retrospective study

IMPORTANCE

The clinical characteristics of infectious mononucleosis (IM) in Chinese children have not been evaluated in multicenter studies, and the effectiveness of antiviral treatment are controversial.

OBJECTIVE

To investigate the clinical characteristics of Chinese children with IM and current status of antiviral therapy for affected patients.

METHODS

Hospitalized patients with IM were enrolled between 2018 and 2020 in five children's hospitals in China. The clinical characteristics were compared among four age groups: <3 years, 3-<6 years, 6-<10 years, and ≥10 years. The clinical characteristics of IM and effectiveness of antiviral therapy were compared among patients receiving acyclovir (ACV), ganciclovir (GCV), and no antiviral therapy (i.e., non-antiviral group).

RESULTS

In total, 499 patients were analyzed; most patients were 3-<6 years of age. The most common symptoms and signs included fever (100%), lymphadenopathy (98.6%), pharyngitis (86.4%), eyelid edema (76.8%), and snoring (72.9%). There were significant differences in rash, hepatomegaly, and liver dysfunction among the four age groups. Patients aged < 3 years had a lower incidence of liver dysfunction and a higher incidence of rash. Among the 499 patients, 50.1% were treated with GCV, 26.3% were treated with ACV, and 23.6% received no antiviral therapy. Compared with the non-antiviral group, patients in the ACV and GCV groups had longer durations of fever (P < 0.001). There were no significant differences in the incidences of complications among the three treatment groups.

INTERPRETATION

The incidence of IM in Chinese children peaked at 3-<6 years of age. Clinical features of IM varied according to age. Patients receiving antiviral therapy exhibited more serious clinical manifestations than did patients without antiviral therapy. The effectiveness of antiviral therapy for IM requires further analysis.

Herpesviridae prevalence in aqueous humor using PCR

Objective

The aim of this study was to determine the prevalence of Herpesviridae family in aqueous humor and the prevalence of antibodies against Herpesviridae family in serum.

Methods

Participants undergoing cataract surgery were included in the study. Serum for viral serology including herpes simplex virus (HSV), varicella zoster virus (VZV), Epstein-Barr virus (EBV), and cytomegalovirus (CMV) was collected. Aqueous humor specimen was tapped for PCR analysis.

Results

Ninety-two participants were included with a mean age of 67.67 years (SD ±12.51). The prevalence of positive serology tests was 83.3% for HSV, 94.0% for VZV, 98.8% for EBV, and 97.6% for CMV. A total of 66 aqueous humor specimens were negative for PCR of Herpesviridae family.

Conclusion

This study showed previous HSV, VZV, EBV and CMV infections in >90% of the Thai population, while no viral presence was detected in aqueous humor. Thus, the serology test is unrelated to the presence of virus in the eye. We suggest that PCR is a valuable tool to diagnose intraocular viral infection and detect virus presenting active infection.

Antiviral Drugs for EBV

Epstein–Barr virus (EBV) infects up to 95% of the adult human population, with primary infection typically occurring during childhood and usually asymptomatic. However, EBV can cause infectious mononucleosis in approximately 35–50% cases when infection occurs during adolescence and early adulthood. Epstein–Barr virus is also associated with several B-cell malignancies including Burkitt lymphoma, Hodgkin lymphoma, and post-transplant lymphoproliferative disease. A number of antiviral drugs have proven to be effective inhibitors of EBV replication, yet have resulted in limited success clinically, and none of them has been approved for treatment of EBV infections.

Antiviral agents for infectious mononucleosis (glandular fever)

BACKGROUND

Infectious mononucleosis (IM) is a clinical syndrome, usually caused by the Epstein Barr virus (EPV), characterised by lymphadenopathy, fever and sore throat. Most cases of symptomatic IM occur in older teenagers or young adults. Usually IM is a benign self-limiting illness and requires only symptomatic treatment. However, occasionally the disease course can be complicated or prolonged and lead to decreased productivity in terms of school or work. Antiviral medications have been used to treat IM, but the use of antivirals for IM is controversial. They may be effective by preventing viral replication which helps to keep the virus inactive. However, there are no guidelines for antivirals in IM.

OBJECTIVES

To assess the effects of antiviral therapy for infectious mononucleosis (IM).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, Issue 3, March 2016), which contains the Cochrane Acute Respiratory Infections (ARI) Group's Specialised Register, MEDLINE (1946 to 15 April 2016), Embase (1974 to 15 April 2016), CINAHL (1981 to 15 April 2016), LILACS (1982 to 15 April 2016) and Web of Science (1955 to 15 April 2016). We searched the World Health Organization (WHO) International Clinical Trials Registry Platform and ClinicalTrials.gov for completed and ongoing trials.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing antivirals versus placebo or no treatment in IM. We included trials of immunocompetent participants of any age or sex with clinical and laboratory-confirmed diagnosis of IM, who had symptoms for up to 14 days. Our primary outcomes were time to clinical recovery and adverse events and side effects of medication. Secondary outcomes included duration of abnormal clinical examination, complications, viral shedding, health-related quality of life, days missing from school or work and economic outcomes.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion, assessed the included studies' risk of bias and extracted data using a customised data extraction sheet. We used the GRADE criteria to rate the quality of the evidence. We pooled heterogeneous data where possible, and presented the results narratively where we could not statistically combine data.

MAIN RESULTS

We included seven RCTs with a total of 333 participants in our review. Three trials studied hospitalised patients, two trials were conducted in an outpatient setting, while the trial setting was unclear in two studies. Participants' ages ranged from two years to young adults. The type of antiviral, administration route, and treatment duration varied between the trials. The antivirals in the included studies were acyclovir, valomaciclovir and valacyclovir. Follow-up varied from 20 days to six months. The diagnosis of IM was based on clinical symptoms and laboratory parameters.The risk of bias for all included studies was either unclear or high risk of bias. The quality of evidence was graded as very low for all outcomes and so the results should be interpreted with caution. There were statistically significant improvements in the treatment group for two of the 12 outcomes. These improvements may be of limited clinical significance.There was a mean reduction in 'time to clinical recovery as assessed by physician' of five days in the treatment group but with wide confidence intervals (CIs) (95% CI -8.04 to -1.08; two studies, 87 participants). Prospective studies indicate that clinical signs and symptoms may take one month or more to resolve and that fatigue may be persistent in approximately 10% of patients at six-month follow-up, so this may not be a clinically meaningful result.Trial results for the outcome 'adverse events and side effects of medication' were reported narratively in only five studies. In some reports authors were unsure whether an adverse event was related to medication or complication of disease. These results could not be pooled due to the potential for double counting results but overall, the majority of trials reporting this outcome did not find any significant difference between treatment and control groups.There was a mean reduction in 'duration of lymphadenopathy' of nine days (95% CI -11.75 to -6.14, two studies, 61 participants) in favour of the treatment group.In terms of viral shedding, the overall effect from six studies was that viral shedding was suppressed while on antiviral treatment, but this effect was not sustained when treatment stopped.For all other outcomes there was no statistically significant difference between antiviral treatment and control groups.

AUTHORS' CONCLUSIONS

The effectiveness of antiviral agents (acyclovir, valomaciclovir and valacyclovir) in acute IM is uncertain. The quality of the evidence is very low. The majority of included studies were at unclear or high risk of bias and so questions remain about the effectiveness of this intervention. Although two of the 12 outcomes have results that favour treatment over control, the quality of the evidence of these results is very low and may not be clinically meaningful. Alongside the lack of evidence of effectiveness, decision makers need to consider the potential adverse events and possible associated costs, and antiviral resistance. Further research in this area is warranted.

A case report of Epstein-Barr virus-associated retinal vasculitis: successful treatment using only acyclovir therapy

The purpose of this study was to describe a presumed case of Epstein–Barr virus (EBV)-associated retinal vasculitis in a 42-year-old female with sudden unilateral vision loss and successful treatment with acyclovir therapy. Diagnostic vitreous biopsy of the right eye was performed to test for EBV and other known infectious causes of retinitis and evaluate vitreous cells and serological testing. Vitreous polymerase chain reaction viral DNA testing result was positive for EBV but negative for herpes simplex virus, varicella-zoster virus, and cytomegalovirus. Serologic testing was negative for toxoplasma gondii, syphilis, tuberculosis, and HIV. Histopathologic analysis of vitreous cells revealed atypical lymphocytes. Fluorescein angiography showed disk leakage, occluded retinal artery, peripheral vascular leakage, and ischemic area of the right eye. Intravenous acyclovir, 10 mg/kg/d, was prescribed for 14 days followed by oral acyclovir for 3 months. All lesions have become quiet. EBV may be a cause of retinal disease, and intravenous acyclovir is a successful treatment choice.

The Effect of Acyclovir on the Acute and Latent Murine Gammaherpesvirus-68 Infection of Mice

Mice inoculated intranasally with murine gammaherpesvirus-68 were used to evaluate the efficacy of acyclovir (ACV) in the treatment of acute and latent infections. Effectiveness was measured by infectious virus assay of the lung (site of active replication) and infectious centre assay of spleen cells (site of latency). Intraperitoneal administration of ACV at 6-h intervals starting soon after inoculation was more effective in reducing infectious virus in the lung than was treatment with 12-hourly injections commencing 3 days post-infection. Further, ACV treatment during acute infection resulted in an approximately 10-fold reduction in the number of infectious centres in the spleen as compared to placebo-treated animals. However, once latency was established, ACV treatment was not effective in reducing the number of infectious centres in the spleen. This is the first report demonstrating that ACV can be used to minimize the replication of murine gammaherpesvirus in mice at the site of primary infection, resulting in a reduction in the number of latently infected spleen lymphocytes.

Epstein-Barr Virus Encephalitis in an Immunocompetent Child: A Case Report and Management of Epstein-Barr Virus Encephalitis

Epstein-Barr virus (EBV) usually causes mild, asymptomatic, and self-limited infections in children and adults; however, it may occasionally lead to severe conditions such as neurological diseases, malignant diseases, hepatic failure, and myocarditis. Epstein-Barr virus-related neurological disorders include meningitis, encephalitis, and cranial or peripheral neuritis, which are mostly seen in immunocompromised patients. The therapeutic modalities for EBV-related severe organ damage including central nervous system manifestations are still uncertain. Herein, we describe a seven-year-old boy with EBV encephalitis who presented with prolonged fever, exudative pharyngitis, reduced consciousness, and neck stiffness. Cranial magnetic resonance imaging showed contrast enhancement in the bilateral insular cortex and the right hypothalamus. The diagnosis was made by EBV-DNA amplification in both the blood and cerebrospinal fluid samples. He was discharged with acyclovir therapy without any sequelae.

A Therapeutic Trial of Valganciclovir in Patients with Uveitis and Positive Epstein-Barr virus Early Antigen D IgG Titers

Purpose

To evaluate the effectiveness of a therapeutic trial of valganciclovir in patients with uveitis with positive Epstein-Barr virus early antigen D immunoglobulin G titers (EBV EA-D).

Methods

We performed a retrospective chart review of 14 patients at the Massachusetts Eye Research and Surgery Institution who had uveitis with positive EBV EA-D but negative studies for all other causes of uveitis and were treated with valganciclovir 450 mg twice a day or valganciclovir 900 mg twice a day between January 2010 and August 2014.

Results

Nine of 14 patients, who had presumed EBV reactivation with associated intraocular inflammation, were successfully treated with valganciclovir: 3 of these were treated with valganciclovir 450 mg twice a day and 6 were treated with valganciclovir 900 mg twice a day. Five of 14 patients failed to respond to valganciclovir with persistent inflammation after at least 2 weeks of valganciclovir therapy, and were subsequently treated with immunomodulatory therapy to control inflammation.

Conclusions

Uveitis can be caused by EBV infection/reactivation. A therapeutic trial with valganciclovir 450 mg twice a day for 1 month in patients with uveitis with positive EBV EA antibody may be beneficial.

Maribavir inhibits Epstein-Barr virus transcription through the EBV protein kinase

Maribavir (MBV) inhibits Epstein-Barr virus (EBV) replication and the enzymatic activity of the viral protein kinase BGLF4. MBV also inhibits expression of multiple EBV transcripts during EBV lytic infection. Here we demonstrate, with the use of a BGLF4 knockout virus, that effects of MBV on transcription take place primarily through inhibition of BGLF4. MBV inhibits viral genome copy numbers and infectivity to levels similar to and exceeding levels produced by BGLF4 knockout virus.

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.

Antiviral treatment for severe EBV infections in apparently immunocompetent patients

BACKGROUND

Infectious mononucleosis usually runs a mild self-limiting course. Complications arise rarely and when so, corticosteroids are the mainstay of their treatment. The role of antivirals in the management of severe EBV infections is debatable.

METHODS

We sought to review the usage of antivirals for severe EBV infection in apparently immunocompetent patients. For this reason a search in PubMed and Scopus was performed for the time period from 1982 to 2009.

RESULTS

45 patients with severe manifestations of infectious mononucleosis received antivirals (as an adjunct to steroids in 26 of them). Specifically 21 patients with CNS involvement (meningoencephalitis, cerebellitis), 4 with peripheral nervous system involvement (Guillain-Barré, myeloradiculitis, facial nerve palsy), 5 with hepatitis and 15 with other afflictions (including adult respiratory distress syndrome, thrombocytopenia, aplastic anemia, acute renal failure, ulcerations, myocarditis, and frosted branch vasculitis) received antiviral medications. Thirty-nine out of these 45 patients had a favourable outcome (27 were cured and 12 showed clinical improvement) while 6 patients died. The most commonly prescribed antiviral regimen was acyclovir monotherapy (35 patients). Three patients received combinations of acyclovir with other antivirals and 1 received famciclovir. Three patients received ganciclovir monotherapy, 1 ganciclovir plus foscarnet, 1 foscarnet and 1 vidarabine.

CONCLUSION

The available data derive from case reports and case series and thus the deduction of conclusions regarding the effect, if any, of antiviral treatment is debatable. However, physicians may consider using antiviral agents in severe manifestations of EBV infections in immunocompetent patients as an adjunct to steroid treatment.

Famciclovir, from the bench to the patient--a comprehensive review of preclinical data

Famciclovir is converted rapidly and efficiently after oral administration to the selective antiviral compound, penciclovir. In cell culture, penciclovir is a potent inhibitor of herpes simplex virus (HSV) types 1 and 2, varicella-zoster virus (VZV), Epstein-Barr virus (EBV) and hepatitis B virus (HBV). Phosphorylation of penciclovir and aciclovir in uninfected cells is limited, and penciclovir, like aciclovir, has minimal effect on replicating cells in culture as expected for a selective antiviral agent. Mode of action studies with VZV and HSV have shown that the phosphorylation of penciclovir in infected cells is far more efficient than for aciclovir. This compensates for differences observed between penciclovir triphosphate and aciclovir triphosphate in the inhibition of HSV and VZV DNA polymerases. Because HBV is not known to encode a thymidine kinase, a different rationale for the selective inhibition of this virus by penciclovir is required. Recent data indicate that the DNA polymerase of HBV is far more sensitive to inhibition by penciclovir triphosphate than cellular DNA polymerases, suggesting that for this virus, selectivity operates at the DNA polymerase. Penciclovir triphosphate is more stable within infected cells than aciclovir triphosphate, and consequently penciclovir has more prolonged antiviral activity than aciclovir. Similarly, famciclovir is more effective than aciclovir or valaciclovir in suppressing HSV replication when given at a lower dosing frequency in certain animal models. These preclinical properties have helped to provide the foundation for the famciclovir clinical programme.

A virologic pilot study of valacyclovir in infectious mononucleosis

BACKGROUND

Infectious mononucleosis decreases the productivity of many college students and Epstein-Barr virus (EBV) infection may result in long-term immune damage.

OBJECTIVES

Evaluate the antiviral effect of valacyclovir during EBV-related acute infectious mononucleosis and explore potential clinical benefits.

STUDY DESIGN

University students who presented during the first 7 days of illness were randomized to receive valacyclovir 3g/day for 14 days or not. The quantity of Epstein-Barr virus (EBV) DNA in oral and whole blood samples was determined by real-time (TaqMan) PCR. The primary outcome was the proportion of subjects with laboratory-confirmed primary EBV infection who had >or=2 log10 decrease in EBV copies/mL in oral washes during the treatment period. Secondary outcomes included clinical effects.

RESULTS

Twenty subjects were studied. The proportion of valacyclovir recipients versus control subjects who had >or=2 log10 decrease in EBV copies was significantly greater for both oral wash fluid-derived cell pellet (P=0.03) and supernatant (P=0.001) samples. At the end of the treatment period, the number of reported symptoms (P=0.03) and the severity of illness (P=0.049) were reduced among valacyclovir recipients as compared with controls.

CONCLUSIONS

Valacyclovir therapy caused a reduction of EBV excretion and possibly produced a clinical benefit in infectious mononucleosis. Because our study was small and not placebo-controlled, these results must be confirmed by a larger, placebo-controlled trial.

Achievements and challenges in antiviral drug discovery

The last 40 years have seen the development of several antiviral drugs with therapeutic value in treating life-threatening or debilitating diseases such as those caused by HIV, hepatitis B virus, herpesviruses (such as herpes simplex virus and varicella zoster virus) and influenza virus. These relatively recent advances have been due to technical breakthroughs in the cultivation of viruses in the laboratory, identification of viral enzymes and, more recently, their molecular biology. We describe here the antecedence of several of the existing antivirals and their strengths and weaknesses. We indicate where the major challenges lie for future improvements of current therapies and possible new indications, such as hepatitis C virus and papillomavirus. We also describe how current antiviral therapies are restricted to a rather limited number of viral diseases of sufficient interest to the pharmaceutical industry. Finally we describe the potential threat of emerging viruses and bio-weapons and the challenges that they present to therapy.

Epstein-Barr virus infections: prospects for treatment

Epstein-Barr virus (EBV) causes infectious mononucleosis and oral hairy leucoplakia, and is associated with a number of malignancies. There are, however, no regulatory agency-approved treatments for EBV-related diseases. Several antiviral drugs inhibit replication of EBV in cell culture including acyclic nucleoside and nucleotide analogues and pyrophosphate analogues, all of which inhibit the EBV DNA polymerase. Despite their potency in vitro, these drugs have limited use in vivo for treatment of acute primary EBV infection as well as EBV-associated malignancies for several reasons. Here we discuss novel anti-EBV compounds, including maribavir, potentially useful for the treatment of acute EBV infections. A number of experimental approaches for treatment of EBV-related malignancies that are not susceptible to conventional antiviral drug treatment are also discussed.

Emerging therapies for herpes viral infections (types 1 – 8)

There are eight members of the herpesviridae family: herpes simplex virus-1 (HSV-1), HSV-2, varicella-zoster virus, Epstein-Barr virus, cytomegalovirus, human herpes virus-6, human herpes virus-7 and human herpes virus-8. The diseases caused by viruses of the herpesviridae family are treated with and managed by systemic and topical antiviral therapies and immunomodulating drugs. Because these viruses establish a latent state in hosts, antiherpetic agents, such as nucleoside analogues, only control symptoms of disease or prevent outbreaks, and cannot cure the infections. There is a need for treatments that require less frequent dosing, can be taken even when lesions are more advanced than the first signs or symptoms, and can treat resistant strains of the viruses without the toxicities of existing therapies. Immunomodulating agents, such as resiquimod, can act on the viruses indirectly by inducing host production of cytokines, and can thereby reduce recurrences of herpes. The new helicase primase inhibitors, which are the first non-nucleoside antiviral compounds, are being investigated for treatment of HSV disease, including infections resistant to existing therapy.

Virologic Diagnosis, Viral Monitoring, and Treatment of Epstein-Barr Virus Infectious Mononucleosis

Epstein-Barr virus (EBV) is the cause of infectious mononucleosis and is associated with severe infections in immunocompromised patients. EBV is also causally linked with several human malignancies. The heterophile antibody test and EBV-specific antibody tests remain the principal means of diagnosis of initial infection in otherwise healthy patients. Enzyme-linked immunosorbent assays have replaced the traditional immunofluorescence assays for EBV-specific antibodies. Several newer molecular diagnostic tests have become available that facilitate accurate monitoring of infection. The role of these tests for patients with uncomplicated infectious mononucleosis is limited, although these tests are being increasingly used to monitor the state and level of EBV replication for severe infections and among immunocompromised patients. Antiviral therapy has a limited, short-term effect on oropharyngeal shedding but has proven ineffective for the clinical manifestations of infectious mononucleosis. Patients with selected complications frequently benefit from short-term corticosteroid therapy.

Severe thrombocytopenia as a complication of acute Epstein-Barr virus infection

Severe thrombocytopenia is an extremely rare complication of acute Epstein-Barr virus (EBV) infection. EBV infection usually causes hematological abnormalities, mainly atypical lymphocytosis, which is a feature of infectious mononucleosis, and uncomplicated cases often present with mild decreases in platelet counts. Our otherwise healthy, 21-year-old male Caucasian patient had thrombocytopenia and bleeding diathesis with platelet counts of 8 x 10(9)/L without other signs and symptoms of infectious mononucleosis. We commenced treatment with intravenous methylprednisolone before the acute EBV infection was serologically confirmed. Platelet counts initially rose and then fell after we stopped administrating corticosteroids. Repeated administration of methylprednisolone was followed by full recovery of the platelet count and normalization of formerly elevated transaminases. EBV infection may happen in children, adolescents and adults and this differential diagnosis should be considered in every patient presenting with acute thrombocytopenia.

Epstein-Barr virus-recent advances

Epstein-Barr virus is a tumorigenic herpes virus that is ubiquitous in the adult population. The virus is generally spread to and between young children through salivary contact, and only causes clinical illness where primary infection is delayed until adolescence or beyond, when an intense immunopathological reaction leads to the symptoms of infectious mononucleosis in roughly 50% of cases. More than 90% of the world's population carry Epstein-Barr virus as a life-long, latent infection of B lymphocytes. Recent data show that by mimicking B-cell antigen-activation pathways the virus enters the long-lived memory B lymphocyte pool where it evades immune elimination by severely restricting its own gene expression. By influencing B-cell survival mechanisms Epstein-Barr virus may induce tumours such as B lymphoproliferative disease and Hodgkin's disease. Vaccines are being developed to prevent and/or treat these conditions, but an animal model is required to study pathogenesis before a rational vaccine strategy can be formulated.

Antiviral agents: Nonantiviral drugs

The current arsenal of antiviral agents available to the practitioner is expanding rapidly, such that by the time this article goes to press, new drugs may have already been added. Although the majority of approved drugs have been developed for use in only a few viral infections (eg, HIV, herpesviruses, and papillomavirus), discoveries made in the development of these drugs may lead to antiviral agents effective against other viruses. In addition, new uses for the currently available drugs are under evaluation. This review of antiviral agents discusses the treatments available for viral infections such as herpes simplex virus, varicella zoster virus, cytomegalovirus, human papillomavirus, chronic viral hepatitis, and others.

Acute complications of Epstein-Barr virus infectious mononucleosis

Infectious mononucleosis caused by Epstein-Barr virus (EBV) usually resolves over a period of weeks or months without sequelae but may occasionally be complicated by a wide variety of neurologic, hematologic, hepatic, respiratory, and psychological complications. The strength of association of EBV with many of these complications remains based on scattered case reports, often using unsophisticated diagnostic tests, and the evidence for causation in many instances is unconvincing. There is little benefit of antiviral treatment of uncomplicated or complicated infectious mononucleosis. Corticosteroids may have a role in hastening resolution of some complications, especially upper airway obstruction and possibly immune-mediated anemia and thrombocytopenia, but should be used judiciously.

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.

Inhibitory effects of novel nucleoside and nucleotide analogues on Epstein-Barr virus replication

The anti-Epstein-Barr virus (EBV) activity of different classes of compounds was assessed by means of an EBV DNA hybridization assay using a digoxigenin-labelled probe specific for the BamHI W fragment of the EBV genome, as well as by measuring viral capsid antigen (VCA) expression after a 7 day incubation period of P3HR-1 producer cells with the test substances. Acyclovir, ganciclovir, cidofovir and zidovudine were included as reference compounds. Several compounds proved to be potent and selective inhibitors of EBV DNA synthesis and VCA expression. Of the new compounds that were evaluated for their anti-EBV activity, the highest efficacy (lowest EC50) and highest selectivity index (SI) were shown by the purine nucleoside analogue 2-amino-7-[(1,3-dihydroxy-2-propoxy)methyl]purine (S2242) (EC50 0.6 ng/ml; SI 600), the acyclic nucleoside phosphonate analogues 9-(2-phosphono -methoxyethyl)-6-dimethylaminopurine (EC50 1.1 micrograms/ml; SI 91), 9-(2-phosphonomethoxyethyl)-2- amino-6-benzhydrylaminopurine (EC50 1.3 micrograms/ml; SI 29), 7-(2-phosphonomethoxyethyl)-6-dimethyl-aminopurine (EC50 0.8 microgram/ml; SI 56), 9-(R)-(2-phosphonomethoxypropyl)-6-(2-dimethylaminoethyl)-aminopur ine (EC50 0.5 microgram/ml; SI 42), the 2',3'-dideoxythymidine derivative 3'-oximino-2',3'-dideoxythymidine (EC50 1.5 micrograms/ml; SI 65), and 1-(2,3- dideoxy-3-N-hydroxyamino-beta-D-threo-pentafuranyl)pentafuranos yl)thymine (EC50 4.1 micrograms/ml; SI > 24).

Epstein-Barr virus infection associated with interstitial nephritis and chronic fatigue

Severe renal disease in the setting of Epstein-Barr virus (EBV) infection is exceedingly rare. We report here the case of a 22-year-old man with acute EBV infection associated with severe interstitial nephritis. The patient developed chronic fatigue and chronic renal failure with a serological profile typical of primary EBV infection. Clinical improvement with anti-EBNA seroconversion occurred after acyclovir therapy. Our patient illustrates that chronic fatigue with major organ dysfunction and a serological profile of primary infection can be seen in chronic EBV infection. In such a case, acyclovir may prove beneficial.

Activity of penciclovir against Epstein-Barr virus

Penciclovir inhibited the productive replication cycle of Epstein-Barr virus (EBV) in assays measuring infectious virus production, viral antigen expression, and viral DNA synthesis. In the test measuring inhibition of EBV DNA synthesis, 50% effective concentrations of penciclovir and acyclovir were 2.3 +/- 0.8 and 2.2 +/- 0.6 micrograms/ml, respectively. The 50% cell growth inhibitory concentration of penciclovir was > 100 micrograms/ml for both P3HR-1 and Raji cells. Penciclovir is a selective inhibitor of EBV in cell culture.

Ocular disease associated with Epstein-Barr virus infection

Epstein-Barr virus (EBV) is a ubiquitous DNA virus of the herpesvirus genus with a high prevalence rate for antibody (about 90%) in the adult population. It is the most common causative agent of infectious mononucleosis syndrome. During recent years an increasing number of ocular disease entities have been reported to be linked to EBV infection. These entities include oculoglandular syndrome, conjunctivitis, dry eye, keratitis, uveitis, choroiditis, retinitis, papillitis and ophthalmoplegia. While EBV-specific serologic tests can now document recent and past primary infection with EBV and also identify patients manifesting atypical immunologic reactions to EBV, the lack of an animal model, the absence of clear-cut response to therapy and the paucity of documentation by culture render the pathogenesis uncertain or the association questionable in many of these cases.

Oral hairy leukoplakia

Oral hairy leukoplakia occurs almost exclusively in human immunodeficiency virus (HIV)-infected patients and is predictive for the development of acquired immunodeficiency syndrome (AIDS). It presents as a white plaque with a rough surface, most commonly on the sides of the tongue. The eruption is frequently overlooked, and, because it is commonly mistaken for oral candidiasis, its true incidence is unknown. The leukoplakia is the result of permissive infection of epithelial cells by the Epstein-Barr virus. Antiviral therapy that inhibits Epstein-Barr virus replication can result in clinical improvement. Oral hairy leukoplakia provides a unique clinical model for investigations on the pathogenesis of Epstein-Barr virus infection.

Ganciclovir. A review of its antiviral activity, pharmacokinetic properties and therapeutic efficacy in cytomegalovirus infections

Ganciclovir is a nucleoside analogue with antiviral activity in vitro against members of the herpes group and some other DNA viruses. It has demonstrated efficacy against human cytomegalovirus infections and should be considered a first-line therapy in the treatment of life- or sight-threatening cytomegalovirus infection in immunocompromised patients. Clinical efficacy varies with the underlying aetiology of immunocompromise and the site of disease, and prompt diagnosis and early treatment initiation appear to improve the response. In patients with cytomegalovirus pneumonia, particularly bone marrow transplant recipients, concomitant administration of cytomegalovirus immune globulin may significantly improve clinical outcome. Maintenance therapy to prevent recurrence is usually required by bone marrow transplant recipients until the recovery of adequate immune function, whereas AIDS patients may require indefinite ganciclovir maintenance therapy to prevent disease progression, as ganciclovir (like other antivirals) does not eradicate latent viral infection. Haematological effects occur relatively frequently during ganciclovir administration but are usually reversible. Ganciclovir has not been directly compared with other antiviral drugs because of the absence until recently of other effective treatments. However, comparative studies with foscarnet, particularly in cytomegalovirus retinitis, will be of considerable interest. Thus, ganciclovir represents a major advance in the therapy of severe cytomegalovirus infections in immunocompromised patients. Comparative studies, and investigation of ways of reducing toxicity (intravitreal administration; concomitant use of stimulants of haematopoiesis; use in conjunction with other antivirals with differing mechanisms of action), may further expand its eventual role.

Nobel Lecture. The purine path to chemotherapy

Antimetabolites of purine metabolism have found a use as anti-leukaemic, antiprotozoal and antiviral drugs, in immunosuppression and transplantation, and in gout and hyperuricemia. Their mechanisms of action are reviewed.

Comparison of the efficacy of surgery and acyclovir therapy in oral hairy leukoplakia

To compare the therapeutic effects of surgical excision and orally administered acyclovir therapy on symptomatic oral hairy leukoplakia, 45 homosexual men who were seropositive for human immunodeficiency virus participated in a 3-month open-label study. In the 14 patients who had surgical excision, pain resolved in four symptomatic patients and the leukoplakia did not recur in the areas of excision. New foci of leukoplakia, however, appeared in 10 patients after 3 months. Of the 16 patients who received acyclovir therapy, 12 had a clinical regression, although recurrences were noted in all patients after 3 months. Three patients had resolution of pain while taking acyclovir; in two the pain recurred after acyclovir was discontinued. No spontaneous remissions of the leukoplakia occurred in the 15 patients who refused therapy. We conclude that surgical excision is effective in patients with symptomatic oral hairy leukoplakia.

The purine path to chemotherapy

Research on antimetabolites of nucleic acid purines led to drugs for the treatment of acute leukemia (6-mercaptopurine and thioguanine), gout and hyperuricemia (allopurinol), and herpesvirus infections (acyclovir), and for the prevention of organ transplant rejection (azathioprine).

The Epstein-Barr virus:host balance in acute infectious mononucleosis patients receiving acyclovir anti-viral therapy

This report describes the first of 2 investigations studying mechanisms of Epstein-Barr virus (EBV) persistence in the infected host; specifically, we wish to determine the extent to which virus carriage within the B-cell system is dependent upon continued replication of the virus in permissive oropharyngeal epithelium. Levels of EBV infection at these 2 sites have been monitored in 21 acute infectious mononucleosis (IM) patients before, during and after treatment with high doses of acyclovir (ACV). Twelve patients received oral ACV for 10 days and 9 patients received i.v. ACV for 5 days before the 10-day oral course; all were followed prospectively for 28 days. Infectious EBV, detectable at high initial levels in the patients' throat washings, disappeared almost completely during ACV treatment, then returned again to high levels post treatment. In contrast, levels of virus-infected B cells in the blood showed no reduction linked to the period of ACV treatment nor any increase with resumption of EBV shedding. During IM, therefore, maintenance of high levels of virus carriage within the B-cell pool is not dependent upon the continual recruitment of newly infected B cells. This might reflect an inability of the immune T-cell response in acute IM patients to prevent continued expansion of the existing EBV-infected B-cell pool. Alternatively, it raises the possibility that EBV carriage in B cells in vivo is maintained through a virus:cell interaction which is not sensitive to virus-specific T-cell surveillance.