Treatment with ganciclovir of adenovirus pneumonia in a cardiac transplant patient

Emerging antiviral therapeutics for human adenovirus infection: Recent developments and novel strategies

Human adenoviruses (HAdV) are ubiquitous human pathogens that cause a significant burden of respiratory, ocular, and gastrointestinal illnesses. Although HAdV infections are generally self-limiting, pediatric and immunocompromised individuals are at particular risk for developing severe disease. Currently, no approved antiviral therapies specific to HAdV exist. Recent outbreaks underscore the need for effective antiviral agents to treat life-threatening infections. In this review we will focus on recent developments in search of potential therapeutic agents for controlling HAdV infections, with a focus on those targeting post-entry stages of the virus replicative cycle.

A case of severe pneumonia with viremia caused by adenovirus B7 identified by off-label use of a multiplex PCR system

Severe infection with human adenovirus (HAdV) is uncommon in adults, and the lack of reliable point-of-care testing makes the diagnosis challenging. A 39-year-old immunocompetent Indian man developed severe pneumonia, and his condition became life-threatening despite antimicrobial therapy. While sputum and blood cultures remained negative, a multiplex PCR respiratory panel (Filmarray Respiratory Panel), which is only approved for use with nasopharyngeal samples, detected HAdV in the serum and tracheal aspirates on day 5. We therefore initiated ganciclovir, steroids, and intravenous immunoglobulin. The patient's respiratory condition improved significantly, and he eventually recovered without complications. We later confirmed that conventional PCR of serum detected HAdV-B7. Our case illustrated that a respiratory panel using multiplex PCR successfully detected HAdV in unapproved samples. Such off-label analyses may support the early diagnosis of infections caused by pathogens that are difficult to identify by routine microbiological examination.

In vitro co-infection by cytomegalovirus improves the antiviral activity of ganciclovir against human adenovirus

Human adenovirus (HAdV) infection has an important clinical impact in the immunosuppressed population and is associated with high morbidity and mortality rates. The lack of a specific, safe and effective antiviral treatment against HAdV makes necessary the search for new therapeutic options. The aim of this study was to evaluate the in vitro activity of ganciclovir (GCV) against HAdV in co-infection by human cytomegalovirus (HCMV) and HAdV in cellular cultures. Quantitative real-time polymerase chain reaction (qPCR) was used to measure HAdV and HCMV DNA replication efficiency in monocultures and in co-infection situations in the presence of both cidofovir (CDV) and GCV. The effects of GCV and CDV were also evaluated in a burst assay (used to measure the production of virus particles) for both viruses, alone and in combination. GCV decreased by 1-log the HAdV DNA replication efficiency in co-infection with HCMV compared with its activity in HAdV monoculture. The burst assay showed that the reductions in virus yield in the presence of GCV were higher for HCMV and co-infection than for HAdV in monoculture (145.2±35.5- vs. 116.4±27.3- vs. 23.0±10.0-fold, respectively, P<0.05). The improved anti-HAdV activity of GCV during co-infection may be because of the more efficient phosphorylation of GCV by the HCMV protein kinase, UL97. Patients treated with GCV as pre-emptive therapy for HCMV infection may be considered as low-risk for developing HAdV infections; however, further evaluations are required to confirm these results.

Drug development against human adenoviruses and its advancement by Syrian hamster models

The symptoms of human adenovirus infections are generally mild and self-limiting. However, these infections have been gaining importance in recent years because of a growing number of immunocompromised patients. Solid organ and hematopoietic stem cell transplant patients are subjected to severe immunosuppressive regimes and cannot efficaciously eliminate virus infections. In these patients, adenovirus infections can develop into deadly multi-organ disseminated disease. Presently, in the absence of approved therapies, physicians rely on drugs developed for other purposes to treat adenovirus infections. As there is a need for anti-adenoviral therapies, researchers have been developing new agents and repurposing existing ones to treat adenovirus infections. There are several small molecule drugs that are being tested for their efficacy against human adenoviruses; some of these have reached clinical trials, while others are still in the preclinical phase. Besides these compounds, research on immunotherapy against adenoviral infection has made significant progress, promising another modality for treatment. The availability of an animal model confirmed the activity of some drugs already in clinical use while proving that others are inactive. This led to the identification of several lead compounds that await further development. In the present article, we review the current status of anti-adenoviral therapies and their advancement by in vivo studies in the Syrian hamster model.

Valganciclovir inhibits human adenovirus replication and pathology in permissive immunosuppressed female and male Syrian hamsters

Adenovirus infections of immunocompromised pediatric hematopoietic stem cell transplant patients can develop into serious and often deadly multi-organ disease. There are no drugs approved for adenovirus infections. Cidofovir (an analog of 2-deoxycytidine monophosphate) is used at times but it can be nephrotoxic and its efficacy has not been proven in clinical trials. Brincidofovir, a promising lipid-linked derivative of cidofovir, is in clinical trials. Ganciclovir, an analog of 2-deoxyguanosine, has been employed occasionally but with unknown efficacy in the clinic. In this study, we evaluated valganciclovir against disseminated adenovirus type 5 (Ad5) infection in our permissive immunosuppressed Syrian hamster model. We administered valganciclovir prophylactically, beginning 12 h pre-infection or therapeutically starting at Day 1, 2, 3, or 4 post-infection. Valganciclovir significantly increased survival, reduced viral replication in the liver, and mitigated the pathology associated with Ad5 infection. In cultured cells, valganciclovir inhibited Ad5 DNA replication and blocked the transition from early to late stage of infection. Valganciclovir directly inhibited Ad5 DNA polymerase in vitro, which may explain, at least in part, its mechanism of action. Ganciclovir and valganciclovir are approved to treat infections by certain herpesviruses. Our results support the use of valganciclovir to treat disseminated adenovirus infections in immunosuppressed patients.

Ganciclovir inhibits human adenovirus replication and pathogenicity in permissive immunosuppressed Syrian hamsters

Adenovirus infections of immunocompromised patients can develop into deadly multiorgan or systemic disease. The virus is especially threatening for pediatric allogeneic hematopoietic stem cell transplant recipients; according to some studies, 10% or more of these patients succumb to disease resulting from adenovirus infection. At present, there is no drug approved for the treatment or prevention of adenovirus infections. Compounds that are approved to treat other virus infections are used off-label to combat adenovirus, but only anecdotal evidence of the efficacy of these drugs exists. Ganciclovir, a drug approved for the treatment of herpesvirus infection, was previously reported to be effective against human adenoviruses in vitro. To model adenovirus infections in immunocompromised humans, we examined ganciclovir's efficacy in immunosuppressed Syrian hamsters intravenously infected with type 5 human adenovirus (Ad5). This animal model is permissive for Ad5 replication, and the animals develop symptoms similar to those seen in humans. We demonstrate that ganciclovir suppresses Ad5 replication in the liver of infected hamsters and that it mitigates the consequences of Ad5 infections in these animals when administered prophylactically or therapeutically. We show that ganciclovir inhibits Ad5 DNA synthesis and late gene expression. The mechanism of action for the drug is not clear; preliminary data suggest that it exerts its antiadenoviral effect by directly inhibiting the adenoviral DNA polymerase. While more extensive studies are required, we believe that ganciclovir is a promising drug candidate to treat adenovirus infections. Brincidofovir, a drug with proven activity against Ad5, was used as a positive control in the prophylactic experiment.

Allograft adenovirus nephritis

We present an uncommon case of allograft adenovirus tubulointerstitial nephritis in a 63-year-old male 6 weeks following cadaveric renal transplantation for end-stage renal failure secondary to hypertensive nephrosclerosis. The patient presented with acute onset of fevers, dysuria, haematuria and diarrhoea with acute graft dysfunction. A renal biopsy demonstrated necrotizing tubulointerstitial nephritis with viral cytopathic changes and no evidence of rejection. Adenovirus was identified as the pathogen. Treatment involved the reduction in the patient's usual immunosuppression, intravenous immunoglobulin, piperacillin-tazobactam and ganciclovir. We present the clinical and pathological findings of necrotizing adenoviral nephropathy, highlighting the importance of considering this diagnosis in renal transplant recipients presenting with interstitial nephritis in the setting of a systemic illness.

Antiadenoviral effects of ganciclovir in types inducing keratoconjunctivitis by quantitative polymerase chain reaction methods

Purpose

The most common external ocular viral infections are caused by several human adenovirus (HAdV) types. Ganciclovir has been reported to inhibit cytomegalovirus, herpes simplex virus types 1 and 2, varicella zoster virus, and Epstein–Barr virus. Ganciclovir ophthalmic gel, 0.15% (Virgan®) is commercially available for cytomegalovirus or herpes virus keratitis. However its inhibitory activity against HAdV is reported only for types 2 and 5. We investigated the antiadenoviral activity of ganciclovir in vitro in several common types currently inducing keratoconjunctivitis.

Materials and methods

A549 cells were used for viral cell culture, and adenovirus types 3 (HAdV3; species B), 4 (species E), and 8, 19a, and 37 (species D) were used. After pretreatment of A549 with serial dilutions of ganciclovir for 24 hours, adenovirus was cultured for 7 days, and adenoviral deoxyribonucleic acid was quantitatively measured by real-time polymerase chain reaction (PCR).

Results

The 50% cytotoxic concentration of ganciclovir was 212 μg/mL. The 50% effective concentration of ganciclovir obtained by real-time PCR ranged between 2.64 and 5.10 μg/mL. A significant inhibitory effect of ganciclovir on adenoviral proliferation was found in all types in a dose-dependent manner. The selectivity index of ganciclovir ranged between 41.6 and 80.3.

Conclusion

Ganciclovir showed significant inhibitory activity against HAdV3, 4, 8, 19a, and 37, which induce epidemic keratoconjunctivitis. These results indicate that ganciclovir is a possible candidate for the treatment of HAdV keratoconjunctivitis, and ganciclovir ophthalmic gel could be applied to adenoviral keratoconjunctivitis in the future.

Adenovirus infections in heart transplantation

Adenovirus infections have been associated with significant morbidity and mortality in immunocompromised hosts. The clinical significance of adenovirus disease in heart transplantation is not well-defined; in particular, the significance of adenovirus identification in myocardium remains unclear. Although severe adenovirus disease has been described in heart transplant recipients, adenovirus infections seem to be more frequently associated with increased risk of adverse cardiac events, such as rejection, ventricular dysfunction, coronary vasculopathy, need for retransplantation, and graft loss because of death. Cidofovir is currently considered the standard of treatment for adenovirus disease not responding to reduction of immunosuppression.

Molecular diagnosis and management of viral infections in hematopoietic stem cell transplant recipients

Viral infections after allogeneic hematopoietic stem cell transplantation (HSCT) are important complications associated with high morbidity and mortality. In this setting, reactivations of persisting latent viral pathogens from donor and/or recipient cells play a central role whereas the sterile environment of transplant units renders new infections less likely. The viruses currently regarded as most relevant in the HSCT setting include particularly the herpes virus family--specifically cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpesvirus 6 (HHV-6)--as well as human adenoviruses (AdVs) and the polyoma virus BK (BKV). Timely detection and monitoring of virus copy numbers are prerequisites for successful preemptive treatment approaches. Pre- and post-transplant surveillance by sensitive and quantitative molecular methods has therefore become an essential part of the diagnostic routine. In this review, we discuss diagnostic aspects and the clinical management of the most important viral infections in HSCT recipients, with a focus on pediatric patients.

The other causes of 'atypical' pneumonia

Mycoplasma, Chlamydia and Legionella are the usual organisms considered to be the etiologic agents of 'atypical' pneumonia. Other microorganisms such as bacteria, viruses, parasites, fungi and mycobacteria can also present with atypical pneumonia manifestations. Outbreaks and isolated cases of respiratory viruses with atypical pneumonia presentations have been reported among immunocompetent and immunosuppressed patients. Severe infections due to these respiratory viruses alone or as a concomitant bacterial or viral infection have been observed. Additionally, in endemic areas, certain zoonotic infections may present as atypical pneumonia.

Acute meningoencephalitis caused by adenovirus serotype 26

Adenoviridae are rare causes of meningoencephalitis in both immunocompetent and immunocompromised hosts. In this article the authors report a case of adenoviral meningoencephalitis caused by serotype 26 and its identification, not described previously, in cerebrospinal fluid (CSF) by PCR and brain tissue by immunohistochemical staining.

Adenovirus infections in transplant recipients

Adenoviruses are increasingly recognized as contributors to morbidity and mortality among stem cell and solid-organ transplant recipients. Clinical presentations range from asymptomatic viremia to respiratory and gastrointestinal disease, hemorrhagic cystitis, and severe disseminated illness. The limited clinical data available support the use of cidofovir for many of these illnesses. Prospective studies are needed to better understand the pathogenesis of and therapeutic options for adenoviral infections in this patient population.

Adenovirus tubulointerstitial nephritis presenting as a renal allograft space occupying lesion

This report describes a case of adenovirus infection in a renal allograft 36 days after transplantation that presented with transient macroscopic hematuria, prominent systemic features and acute renal dysfunction. The patient had persistent high fevers despite broad antibiotic cover. A CT scan demonstrated a new discrete space occupying lesion in the allograft, which was devoid of blood flow on Doppler sonography. A targeted renal biopsy showed florid and focal necrotizing interstitial nephritis with intranuclear tubular viral inclusions. Treatment with ganciclovir and reduction in immunosuppression resulted in a rapid improvement. Immunohistochemistry and electron microscopy confirmed adenovirus infection. This case demonstrates an uncommon presentation of necrotizing adenoviral nephropathy, which should be considered in cases of renal allograft mass lesions.

Community acquired respiratory viral infections after lung transplantation: clinical features and long-term consequences

Community acquired respiratory viruses (CARVs) are increasingly recognized as serious threats to lung transplant recipients. While CARVs such as respiratory syncytial virus, parainfluenza, influenza, and adenovirus usually cause self-limited illnesses in immunocompetent subjects, infections in the transplant recipient can be dramatic. As transplant recipients live longer and diagnostic methods improve, the burden of CARVs will undoubtedly increase. Because of limited therapeutic options, some patients may succumb to CARV infections, while many survivors develop chronic allograft dysfunction. Recognition of this latter phenomenon has implicated CARVs in the pathogenesis of bronchiolitis obliterans.

Prospects for adenovirus antivirals

Adenoviruses cause a number of self-limiting but often highly infectious diseases that affect multiple organs, most commonly those associated with respiratory, genitourinary and gastrointestinal tracts and the ocular surface. Many factors have driven a search for effective topical and systemic antivirals to adenoviruses. These include patient morbidity, economic losses and chronic visual disturbances associated with epidemic keratoconjunctivitis; and the startling recent trend of high morbidity and rising mortality associated with systemic adenoviral infections in the immunosuppressed, particularly paediatric bone marrow transplant recipients. The development of effective antivirals has proven to be a complex task, owing to the fact that multiple and often genetically divergent adenovirus serotypes can cause similar diseases. Currently, there remains no licensed systemic or topical treatment in the USA or Europe. However, many compounds have been explored for activity against adenoviruses, and some have been evaluated clinically in either a topical setting for ocular disease or in the setting of systemic treatment in the face of life-threatening adenovirus infections. This article outlines such compounds, discusses the potential for their clinical development, and highlights some problems that may be faced in evaluating their efficacy clinically.

Fatal Type 3 Adenoviral Pneumonia in Immunocompetent Adult Identical Twins

We describe adult twin sisters who developed severe adenoviral pneumonia with relative leukopenia, progressive focal infiltrates, shock, and hypoxia. Potential determinants of severe adenoviral disease are discussed.

Comparison of HSV-1 thymidine kinase-dependent and -independent inhibition of replication-competent adenoviral vectors by a panel of drugs

Replication-competent adenoviral vectors hold the promise to be more efficient gene delivery vehicles than their replication-deficient counterparts, but they are also associated with a higher risk for adverse effects, especially in light of the fact that there is no established effective therapy for serious, disseminated adenovirus infection. To assess whether the therapeutic options to inhibit adenoviral replication can be enhanced by expressing a suicide gene, we examined the antiadenoviral effects of 15 drugs against wild-type adenovirus type 5 (Ad5) and an Ad5-based replication-competent vector expressing herpes simplex virus-1 thymidine kinase (HSV-tk) (Ad.OW34) using a real-time polymerase chain reaction -based assay and flow cytometry. Ad5 and Ad.OW34 were highly susceptible to the fluorinated pyrimidine analogs 5-fluoro-2'-deoxyuridine (FUdR), 5-fluorouridine (FUR), and trifluorothymidine (TFT), with a mean 50% inhibitory concentration (IC(50)) ranging from 0.12 to 0.32 microM. The mean IC(50) of ribavirin and cidofovir (CDV) for Ad5, the most frequently used drugs to treat adenovirus disease, was 6.87 and 3.19 microM, respectively. In contrast to Ad5, the Ad.OW34 vector was susceptible to (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVdU, IC(50) 0.09 microM), ganciclovir (GCV, IC(50) 0.19 microM), and acyclovir (ACV, IC(50) 32.04 microM). Additionally, we demonstrated in an animal model that Ad.OW34 vector replication can be inhibited significantly by GCV, CDV, and TFT by 35.2, 7.7, and 3.7-fold, respectively, compared to untreated animals. The observed antiadenoviral effects were primarily not through cell killing, since the in vitro 50% cytotoxic concentrations (CC(50)) were more than 1000 times higher than the antiadenoviral IC(50) of the drugs examined, even in cells stably expressing HSV-tk. Since for HSV-tk-dependent inhibition of adenoviral vectors, stability of HSV-tk expression is crucial, we examined Ad.OW34 vector stability, by passaging the vector 10 times serially in the presence of 10 microM GCV. The HSV-tk/GCV system neither changed the susceptibility of Ad.OW34 to GCV significantly nor detectable vector rearrangements occurred, suggesting that the system might be suitable as a fail-safe mechanism to stop adenoviral vector replication.

Viral infections in immunocompromised patients: what's new with respiratory viruses?

PURPOSE OF REVIEW

The leading cause of death in solid organ and hematopoietic stem cell transplant recipients is infection. The respiratory viruses, particularly respiratory syncytial virus, influenza, parainfluenza, adenovirus, and picornaviruses, are increasingly recognized as significant pathogens in these populations.

RECENT FINDINGS

Respiratory syncytial virus has again been found to be the most common of the respiratory viruses causing severe infections in transplant recipients. Advances in prevention, particularly with regard to infection control practices, and to lesser extent treatment have had a substantial impact on the frequency and outcomes of this infection. New studies have clarified the impact of influenza in the hematopoietic stem cell transplant recipients and have provided evidence to support the use of M2 and neuraminidase inhibitors for early treatment. The epidemiology of parainfluenza and adenovirus in transplant recipients has been clarified, although therapeutic modalities are still limited and understudied. New antiviral medications may bring improved outcomes of picornavirus infections in this population. Finally, a new virus, the human metapneumovirus, has recently been described and may be a significant respiratory pathogen in immunocompromised transplant recipients.

SUMMARY

Studies published over the past year have documented a new respiratory pathogen. They have also resulted in improved understanding of the epidemiology of all of the respiratory virus pathogens, and have contributed to improve management of respiratory syncytial virus and influenza infection in hematopoietic stem cell transplant and solid organ transplant recipients.

Intravenous ribavirin treatment for severe adenovirus disease in immunocompromised children

BACKGROUND

Adenovirus is an important cause of morbidity and mortality in the immunocompromised host. The incidence of severe adenovirus disease in pediatrics is increasing in association with growing numbers of immunocompromised children, where case fatality rates as high as 50% to 80% have been reported. There are no approved antiviral agents with proven efficacy for the treatment of severe adenovirus disease, nor are there any prospective randomized, controlled trials of potentially useful anti-adenovirus therapies. Apparent clinical success in the treatment of severe adenovirus disease is limited to a few case reports and small series. Experience is greatest with intravenous ribavirin and cidofovir. Ribavirin, a guanosine analogue, has broad antiviral activity against both RNA and DNA viruses, including documented activity against adenovirus in vitro. Ribavirin is licensed in aerosol form for the treatment of respiratory syncytial virus infection, and orally in combination with interferon to treat hepatitis C. Intravenous ribavirin is the treatment of choice for infection with hemorrhagic fever viruses. The most common adverse effect of intravenous ribavirin is reversible mild anemia. The use of cidofovir in severe adenovirus infection has been limited by adverse effects, the most significant of which is nephrotoxicity.

OBJECTIVE

We report our experience with intravenous ribavirin therapy for severe adenovirus disease in a series of immunocompromised children and review the literature.

DESIGN/METHODS

We retrospectively reviewed the medical records of 5 children treated with intravenous ribavirin for documented severe adenovirus disease. Two patients developed adenovirus hemorrhagic cystitis after cardiac and bone marrow transplants, respectively. The bone marrow transplant patient also received intravenous cidofovir for progressive disseminated disease. An additional 3 children developed adenovirus pneumonia; 2 were neonates, 1 of whom had partial DiGeorge syndrome. The remaining infant had recently undergone a cardiac transplant. Intravenous ribavirin was administered on a compassionate-use protocol.

RESULTS

Complete clinical recovery followed later by viral clearance was observed in 2 children: the cardiac transplant recipient with adenovirus hemorrhagic cystitis and the immunocompetent neonate with adenovirus pneumonia. The remaining 3 children died of adenovirus disease. Intravenous ribavirin therapy was well tolerated. Use of cidofovir in 1 child was associated with progressive renal failure and neutropenia.

DISCUSSION

Our series of patients is representative of the spectrum of immunocompromised children at greatest risk for severe adenovirus disease, namely solid-organ and bone marrow transplant recipients, neonates, and children with immunodeficiency. Although intravenous ribavirin was not effective for all children with severe adenovirus disease in this series or in the literature, therapy is unlikely to be of benefit if begun late in the course of the infection. Early identification, eg by polymerase chain reaction of those patients at risk of disseminated adenovirus disease may permit earlier antiviral treatment and better evaluation of therapeutic response.

CONCLUSIONS

Two of 5 children with severe adenovirus disease treated with intravenous ribavirin recovered. The availability of newer rapid diagnostic techniques, such as polymerase chain reaction, may make earlier, more effective treatment of adenovirus infection possible. Given the seriousness and increasing prevalence of adenovirus disease in certain hosts, especially children, a large, multicenter clinical trial of potentially useful anti-adenoviral therapies, such as intravenous ribavirin, is clearly required to demonstrate the most effective and least toxic therapy.

Gastrointestinal infections in the immunocompromised host

Gastrointestinal disease is a significant cause of morbidity and mortality in the immunocompromised patient. This article focuses on the infectious gastrointestinal complications associated with the treatment of malignant disease and with solid organ transplantation but not HIV. Gastrointestinal defenses and the various mechanisms by which they are impaired are reviewed. The major pathogens and malignancies of this patient population and an approach to their diagnosis, treatment, and prevention are discussed.

Viral infections after renal transplantation

Viral infections are a leading cause of posttransplantation morbidity and mortality. A number of recent developments have altered our understanding and management of these disorders. The pathogenetic roles of several viruses, including human herpesviruses 6 and 8, have been newly established. Molecular-based diagnostic tests now make more rapid diagnosis possible. The licensing of new potent antiviral agents offers a wider choice of drugs for viral prophylaxis and treatment. The use of more potent immunosuppressive agents is responsible in part for the increasing incidence of some viral infections, but this varies among drugs, and individual viruses differ in their sensitivity to immunosuppressive agents. This review summarizes the natural history, diagnosis, prevention, and treatment of many common viral infections after renal transplantation.