Adenoviruses in the immunocompromised host

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.

Molecular monitoring of adenovirus in peripheral blood after allogeneic bone marrow transplantation permits early diagnosis of disseminated disease

Adenovirus (AdV) infection in the course of allogeneic stem cell transplantation (SCT) is associated with high transplant-related morbidity and mortality. Disseminated AdV disease is lethal in most instances. Early detection of AdV infection and identification of patients carrying a high risk of disseminated disease therefore remain a major challenge. In view of the large number of existing AdV types, we have established real-time polymerase chain reaction (PCR) assays permitting sensitive detection and quantification of all 51 currently known human AdV serotypes. In a series of 132 consecutive pediatric patients undergoing SCT, more than 5000 samples derived from peripheral blood (PB), stool, urine, and throat were screened for adenovirus infection by PCR during the posttransplantation period. Thirty-six patients (27%) tested positive by PCR, revealing AdV types of the subgenera A, B, C, D, and F. Except for enteritis in some patients with AdV positivity in stool, detection of the virus at sites other than PB was not associated with clinical signs of virus disease, and transplant-related mortality was not significantly different from AdV-negative patients. By contrast, 82% of patients who had detectable AdV in PB died from infectious complications (P <.001). Monitoring of PB specimens by real-time PCR permitted early diagnosis of invasive AdV infection in all instances. In patients who developed disseminated AdV disease, detection of the virus in PB preceded onset of clinical symptoms by a median of more than 3 weeks. The observation of AdV in peripheral blood may therefore serve as a basis for early initiation of preemptive antiviral treatment.

Adenovirus infection in pediatric small bowel transplantation recipients

BACKGROUND

The purpose of this study was to determine the prevalence of adenoviral infection in pediatric small bowel transplantation (SBT) recipients, examine risk factors for progression to histologic disease, and examine the impact of adenovirus on outcome.

METHODS

Beginning in July 2000, all SBT recipients had viral cultures for adenovirus, cytomegalovirus (CMV), and herpes simplex virus (HSV) obtained routinely during graft biopsies. The medical records were retrospectively reviewed for frequency and site of viral culture, types and doses of immunosuppressive drugs, episodes of rejection, histology of allograft biopsies, and other infections. Adenoviral isolates were typed by polymerase chain reaction and type-specific neutralization assays.

RESULTS

All 14 SBT recipients who met enrollment criteria had evidence of adenoviral infection (intestinal graft, 13; liver graft, 1). Eight of 14 developed histologic disease with identifiable adenoviral intranuclear inclusions. In contrast, CMV enteritis was identified in only one patient, who subsequently also developed adenoviral disease. No other viruses were detected. Adenoviral cultures were first positive within 30 days of transplant in nine. Patients with histologic disease were more likely than those without to have received intensive corticosteroid therapy (P<0.007), had virus isolated from more than one site (P=0.03), and had persistent positive cultures (P<0.01).

CONCLUSIONS

Adenovirus was commonly isolated from children undergoing intestinal transplantation. Progression to disease may be associated with more intensive immunosuppressive therapy and inability to clear virus.

Extensive cross-reactivity of CD4+ adenovirus-specific T cells: implications for immunotherapy and gene therapy

Adenovirus (Ad)-specific T-cell responses in healthy adult donors were investigated. Ad5, inactivated by methylene blue plus visible light, induced proliferation and gamma interferon (IFN-gamma) production in peripheral blood mononuclear cells of the majority of donors. Responding T cells were CD4(+) and produced IFN-gamma upon restimulation with infectious Ad5 and Ads of different subgroups. T-cell clones showed distinct cross-reactivity patterns recognizing Ad serotypes from either one subgroup (C), two subgroups (B and C), or three subgroups (A, B, and C). This cross-reactivity of Ad-specific T cells has relevance both for Ad-based gene therapy protocols, as well as for the feasibility of T-cell-mediated adoptive immunotherapy in recipients of an allogeneic stem cell transplantation.

Adenovirus infection in hematopoietic stem cell transplantation: effect of ganciclovir and impact on survival

Adenoviruses (ADV) are emerging as important causes of morbidity and mortality in patients undergoing hematopoietic stem cell transplantation (HSCT). In mainly non-T-cell depleted HSCT recipients, we analyzed the incidence of ADV infection, risk factors for infection, the effect of ganciclovir administered for prevention of cytomegalovirus (CMV), and the impact of ADV infection on survival. The overall incidence of ADV, irrespective of the method of detection, was 8.5% (450/5233) and 12.3% (43/348) after the first or second allogeneic HSCT, and 6.3% (78/1219) and 6.5% (5/77) after the first or second autologous HSCT, respectively. The most frequent sites of infection and disease were stool and gastrointestinal tract, respectively. Statistically significant risk factors associated with ADV infections among allogeneic recipients included younger age, grade II to IV graft-versus-host disease, year of transplantation, and a second allogeneic HSCT. Furthermore, allogeneic patients seronegative for CMV at transplantation and seropositive allogeneic patients who did not receive ganciclovir, either at engraftment or as pre-emptive therapy on CMV reactivation, were at higher risk of developing ADV infections compared with seropositive patients who received ganciclovir (odds ratio=1.8, 95% confidence interval (CI) 1.2 to 2.8, P=.005 and odds ratio=3.4, 95% CI 2.1 to 5.55, P<.0001, respectively). The hazard of overall mortality was higher in patients who contracted ADV compared with those who did not (hazard ratio 1.5, 95% CI 1.3 to 1.7, P<.0001). This study shows that ADV infections are associated with poor transplantation outcome in T-cell repleted HSCT recipients. Ganciclovir, given for CMV prevention, may have a protective effect. Controlled treatment and prevention studies are warranted.

Adenovirus meningoencephalitis in a patient with large B-cell lymphoma

We report a case of a 58-year-old female with neuromeningeal relapse of a large B-cell lymphoma which developed a meningoencephalitis due to adenovirus (ADV). Diagnosis of suspected viral meningoencephalitis was based on computed tomography (CT) scan radiological pictures, which were atypical for CNS neoplastic infiltrations, and it was confirmed by direct immunofluorescence performed on cerebrospinal fluid. Cultural exams identified adenovirus type 7. The ADV infection resolved after treatment with total four doses of cidofovir. Unfortunately, the hematological disease progressed and the patient died 2 months later from disseminated lymphoma.

Fulminant adenovirus hepatitis following bone marrow transplantation. A case report and brief review of the literature

Adenovirus infections are frequently encountered in immunocompromised patients and transplant recipients. However, fulminant hepatic failure due to adenovirus infection as a fatal complication in bone marrow transplant recipients is extremely rare. We report a case of fulminant adenovirus hepatitis in a 21-year-old allogeneic bone marrow transplant recipient who subsequently died of the disease. The diagnosis was established by histologic and immunohistochemical examination of a liver biopsy and was confirmed by liver tissue and blood cultures.

Fatal adenovirus infection during alemtuzumab (anti-CD52 monoclonal antibody) treatment of a patient with fludarabine-refractory B-cell chronic lymphocytic leukemia

Alemtuzumab (Campath-1H) is a humanized CD52 monoclonal antibody that targets normal as well as malignant B- and T-lymphocytes. Alemtuzumab has significant antitumor activity in chronic lymphocytic leukemia (B-CLL) but also induces immunosuppression. We describe a case of fatal adenovirus infection in a heavily pretreated patient with fludarabine-refractory B-CLL receiving alemtuzumab therapy, drawing attention to the fact that also viruses other than cytomegalovirus (CMV) and herpes simplex (HSV) need to be considered in B-CLL patients with fever of unknown origin while on alemtuzumab treatment.

Clinical assessment of a generic DNA amplification assay for the identification of respiratory adenovirus infections

BACKGROUND

respiratory adenoviruses are common, often resulting in serious sporadic and epidemic infections and impaired immunity can dramatically increase their severity. They are now thought capable of establishing latency. Diagnosis by culture is slow while direct antigen detection by immunofluorescence lacks sensitivity. Molecular diagnosis can be both rapid and sensitive but the genetic heterogeneity of adenoviruses poses problems.

OBJECTIVES

to design a generic adenovirus nested polymerase chain amplification assay designed to be capable of detecting all respiratory adenoviruses. This was achieved through optimised thermal cycling and the development of a generic degenerate primer set targeting the adenovirus hexon gene.

STUDY DESIGN

this was a cross-sectional study on 172 respiratory specimens from hospital-based patients, and one from a general practice, in Northern Ireland. A comparison was made between the amplification assay, virus culture and immunofluorescence.

RESULTS

the nested polymerase chain reaction (nPCR) assay had a generic capacity for adenovirus detection and an analytical sensitivity of 6.4x10(2) copies/ml. Using an expanded gold standard (defined as a true positive or a true negative where a specimen was positive or negative by at least two of the study assays, respectively), PCR had a clinical sensitivity and specificity of 46/46 (100%) and 15/126 (91.3%), respectively. Patients with acute respiratory adenovirus infections were more likely to be male (chi(2), p=0.005) and to present with a fever (chi(2), p=0.02) than patients diagnosed with another respiratory virus. Co-infection was identified in 12/172 patients.

CONCLUSIONS

the nested amplification assay proved highly sensitive in both the analytical and clinical settings for the detection of respiratory adenovirus infections.

Adenovirus infection of a renal allograft

One month after renal transplantation, a 60-year-old man developed acute allograft dysfunction associated with gross hematuria and dysuria. Urinary cytological examination showed viral inclusion-bearing epithelial cells. A renal transplant biopsy specimen showed granulomatous interstitial nephritis, tubular necrosis, and ground glass-like intranuclear viral inclusion bodies in tubular cells caused by an adenovirus (ADV) infection. A reduction in baseline immunosuppressive therapy resulted in rapid normalization of allograft function and ultimately viral clearance. We report this case not only to illustrate an exceptional manifestation of an ADV infection in a renal allograft, but also to highlight the beneficial effect of reduction in immunosuppressive therapy on viral replication and clinical outcome.

Adenovirus: an increasingly important pathogen in paediatric bone marrow transplant patients

Adenovirus is increasingly being recognised as a significant pathogen in children following bone marrow transplantation. The virus is endemic in the general paediatric population, and frequently causes severe disease in immunocompromised patients, especially children. Immune responses to adenovirus infection are not fully understood but T-cell responses appear to be important for recovery. Infections can affect a variety of organs with gastrointestinal and urinary tract diseases being the most common. When disseminated infection occurs, reported mortality rates are as high as 60%. The responses to treatment in immunocompromised patients have generally been disappointing. New molecular diagnostic techniques have meant that adenoviral infections can now be detected early, often before symptoms have developed. Clinicians now screen for adenovirus infection to allow early initiation of treatment. It is hoped that this approach, together with effective antiviral therapy, will reduce the deaths from this common virus in high-risk children.

A canine conditionally replicating adenovirus for evaluating oncolytic virotherapy in a syngeneic animal model

Oncolytic adenoviruses, which selectively replicate in and subsequently kill cancer cells, have emerged as a promising approach for treatment of tumors resistant to other modalities. Although preclinical results have been exciting, single-agent clinical efficacy has been less impressive heretofore. The immunogenicity of adenoviruses, and consequent premature abrogation of replication, may have been a partial reason. Improving the oncolytic potency of agents has been hampered by the inability to study host-vector interactions in immune-competent systems, since human serotype adenoviruses do not productively replicate in animal tissues. Therefore, approaches such as immunomodulation, which could result in sustained replication and subsequently increased oncolysis, have not been studied. Utilizing the osteocalcin promoter for restricting the replication of a canine adenovirus to dog osteosarcoma cells, we generated and tested the first nonhuman oncolytic adenovirus. This virus effectively killed canine osteosarcoma cells in vitro and yielded a therapeutic benefit in vivo. Canine osteosarcoma is the most frequent malignant disease in large dogs, with over 8000 cases in the United States annually, and there is no curative treatment. Therefore, immunomodulation for increased oncolytic potency could be studied with clinical trials in this population. This could eventually translate into human trials.

Use of polymerase chain reaction for diagnosis of disseminated adenovirus infection

We report a fatal case of disseminated adenovirus infection with fulminant hepatic failure in an 8-month-old child after peripheral blood stem cell transplantation. The virus was identified in blood, urine, respiratory aspirate and stool samples and was typed as adenovirus type 2 through PCR and sequencing of part of the hexon gene, with the use of degenerated consensus primers.

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.

Exploiting the natural diversity in adenovirus tropism for therapy and prevention of disease

Since targeting of recombinant adenovirus vectors to defined cell types in vivo is a major challenge in gene therapy and vaccinology, we explored the natural diversity in human adenovirus tissue tropism. Hereto, we constructed a library of Ad5 vectors carrying fibers from other human serotypes. From this library, we identified vectors that efficiently infect human cells that are important for diverse gene therapy approaches and for induction of immunity. For several medical applications (prenatal diagnosis, artificial bone, vaccination, and cardiovascular disease), we demonstrate the applicability of these novel vectors. In addition, screening cell types derived from different species revealed that cellular receptors for human subgroup B adenoviruses are not conserved between rodents and primates. These results provide a rationale for utilizing elements of human adenovirus serotypes to generate chimeric vectors that improve our knowledge concerning adenovirus biology and widen the therapeutic window for vaccination and many different gene transfer applications.

Human adenoviruses of subgenera B, C, and E with various tropisms differ in both binding to and replication in the epithelial A549 and 293 cells

Adenoviruses of six subgenera, namely, adenovirus 31 (Ad31) (subgenus A), Ad3, Ad7, Ad11p, Ad11a, and Ad35 (subgenus B), Ad5v and Ad5p (subgenus C), Ad37 (subgenus D), Ad4 (subgenus E), and Ad41 (subgenus F), were studied. The relative binding properties of different adenoviruses to 293 (human kidney embryonic cells) and A549 (human lung carcinoma cells) cells were compared by flow cytometry. All analyzed adenoviruses bound to cells in a dose-dependent manner. The binding capacity showed that Ad11p, Ad35 (subgenus B:2) with kidney tropism, and Ad4 (subgenus E), which can cause adenopharyngoconjunctivitis, bound strongly to both A549 and 293 cells. The other members of subgenus B and Ad37 of subgenus D manifested an intermediate binding capacity. The analyzed adenoviruses of subgenera A, C, and F manifested a low affinity. Adenoviruses of subgenera B:2 and E manifested high binding affinity to preparations of cell membranes from the epithelial cell lines. Reciprocal competition experiments using Ad11p and Ad4 demonstrated that the two viruses did not block each other. Antibodies against alphavbeta3 and alphavbeta5 reduced the binding of Ad5v virions and slightly impaired the binding of Ad4 but did not affect Ad11p binding to the A549 cell surface. Recombinant fiber proteins of Ad11p and Ad35 reciprocally blocked the binding of both viruses to the epithelial cells but they could not block Ad4. The hexon protein expression of Ad11p and Ad4 was 100 times more efficient than that of the Ad5 vector (pFG140), whereas the infectivity of Ad11p and Ad4 was 40- to 200-fold that of the commonly used Ad5v vector. Taken together, our findings demonstrate that Ad11p and Ad4 bind different receptor molecules and that the fibers of these two viruses provide the predominant high degree of binding, which obviously is a requirement for subsequent internalization and efficacious expression.

Quantification of adenovirus DNA in plasma for management of infection in stem cell graft recipients

We used a real-time polymerase chain reaction method for quantification of adenovirus to monitor the dynamics of viral DNA load in plasma in pediatric stem-cell graft recipients. Two cases are described to demonstrate that detection and quantification of the adenovirus DNA load at regular intervals may be important to document the stage of adenovirus infection, to make decisions on clinical intervention, and to accurately monitor the response to antiviral therapy.

Emerging new therapies for chemotherapy-resistant cancer using adenoviral vectors

The treatment of cancer by genetic manipulation of either the tumor itself or the patient as a whole offers new avenues for the treatment of otherwise refractory cancers. Gene therapy seeks to correct underlying genetic defects in malignant tissue or to augment the host defense response or to promote selectivity of other therapies. Many innovative and exciting genetic targets have been recently identified. However, the field as a whole is still constrained by limitations of gene delivery. The most common vector for gene delivery is modified adenovirus. In this review, we survey a sampling of current therapeutic approaches that depend upon adenoviral delivery vehicles and outline the advantages and disadvantages of this vector system.

Head and neck cancer: gene therapy approaches. Part 1: adenoviral vectors

Treatment options for recurrent or refractory head and neck cancer are limited. The goal of gene therapy is to introduce new genetic material into cancer cells without affecting toxicity to surrounding malignant cells. The most common vehicles for delivery of genes are adenoviruses. Adenoviruses gain access to malignant and normal cell cytoplasm via viral ligand binding to a unique cell surface receptor (the coxsackie adenovirus receptor [CAR]). However, this receptor is not cancer specific. Genetic modification of adenoviral DNA can create cancer specific targeting. Adenoviruses can be modified to express cancer specific ligands thereby focusing binding to malignant tissue. Furthermore, adenoviral delivered genes can be put under cancer specific promoter control to further limit gene expression in malignant tissue. Increased antitumour activity from such modifications has been demonstrated preclinically and several clinical trials have been completed demonstrating safety and clinical activity of non-replicating and conditional replicating adenoviral vector thereby opening the door for gene delivery and cancer specific targeting.

Transplant-related toxicity and mortality: an AIEOP prospective study in 636 pediatric patients transplanted for acute leukemia

Hematopoietic stem cell transplantation can cure high-risk acute leukemia (AL), but the occurrence of non-leukemic death is still high. The AIEOP conducted a prospective study in order to assess incidence and relationships of early toxicity and transplant-related mortality (TRM) in a pediatric population. Between 1990 and 1997 toxicities reported in eight organs (central nervous system, heart, lungs, liver, gut, kidneys, bladder, mucosa) were classified into three grades (mild, moderate, severe) and prospectively registered for 636 consecutive children who underwent autologous (216) or allogeneic (420) transplantation, either from an HLA compatible related (294), or alternative (126) donor in 13 AIEOP transplant centers. Overall, 47% of the patients are alive in CR (3-year EFS: 45.2%, s.e.: 2.1), 19% died in CR at a median of 60 days (90-day TRM: 14.3%, s.e.: 1.4), 34% relapsed. Toxicity of any organ, but mucosa and gut, was positively correlated with early death; moderate and severe toxicity to heart, lungs, liver and kidneys significantly increased early TRM, with estimated relative risks of 9.1, 5.5, 2.7 and 2.8, respectively, as compared to absent or mild toxicity. Patients with grade III-IV aGVHD experienced more than double (56% vs. 19%) TRM than patients with grade 0-II aGVHD. A higher cumulative toxicity score, estimating the impact of toxicity on TRM, was significantly associated with transplantation from an alternative donor. Quantitative assessment allowed us to describe the extent to which 'grade' of toxicity and 'type' of involved organs were related to mortality and pre-transplant characteristics and yielded a prognostic score potentially useful to compare different conditioning regimens and predict probability of early death.

Antiviral activity of NMSO3 against adenovirus in vitro

NMSO3, a sulfated sialyl lipid, was evaluated for its efficacy against adenovirus (AdV) in vitro. The median effective concentration (50% effective concentration, EC(50)) of NMSO3 against replication of AdV type 2 (AdV2), type 4 (AdV4), type 8 (AdV8) and type 37 (AdV37) was 0.21-0.71 microg/ml in HEp-2 cells and 1.01-1.41 microg/ml in MKN-28 cells. The EC(50) values of NMSO3 were lower than those of HPMPC and ddC, which were also evaluated. NMSO3 exhibited minimal cytotoxicity against HEp-2 cells and MKN-28 cells, both for which the median cytotoxic concentration (50% cytotoxic concentration, CC(50)) was more than 1000 microg/ml. NMSO3 was the most potent and selective anti-AdV compound of those examined. NMSO3 inhibited AdV infection of HEp-2 cells only when present during the virus adsorption period. A virus binding assay using radiolabeled AdV4 revealed that NMSO3 inhibited viral binding to the HEp-2 cells. NMSO3 itself bound to the virus particles, but not to the HEp-2 cell membrane. Thus, the mechanism of anti-AdV activity by NMSO3 involves inhibition of virus adsorption to cells by NMSO3 binding to viral particles.

Infectious complications of lung transplantation

Lung transplantation is associated with a high incidence of infection which directly impacts the morbidity and mortality associated with the procedure. In addition, these infections may also have immunologic consequences that play a role in the evolution of lung injury syndromes, resulting in earlier loss of graft than otherwise would be expected to occur. Although bacteria are responsible for the majority of infections following lung transplantation, fungal infections are associated with the highest mortality. This paper is an overview of the major infectious complications encountered in the lung transplant population. The epidemiology, prophylaxis, and treatment of infections following lung transplantation are critical areas for continued research.

Community respiratory virus infections following lung transplantation

Respiratory infections remain a significant cause of morbidity and mortality after lung transplantation. In addition to cytomegalovirus, the community respiratory viruses such as respiratory syncytial virus (RSV), parainfluenza virus (PIV), influenza virus, and adenovirus, are important causes of infection in transplant recipients, often involve the lower respiratory tract, and may be associated with significant morbidity and mortality. In this review, we summarize the current state of knowledge regarding the epidemiology, clinical manifestations, diagnosis, treatment and outcomes associated with RSV, PIV, influenza virus, and adenovirus infections in lung transplant recipients.

Fulminant hepatic failure secondary to adenovirus following fludarabine-based chemotherapy for non-Hodgkin's lymphoma

Self-limited adenoviral infections are very common with the majority of infections resolving rapidly. Fatal complications may occur in severely immunocompromised patients. We describe a case of fulminant hepatic failure due to adenovirus in a 54-year-old man treated with fludarabine and cyclophosphamide for non-Hodgkin's lymphoma. There are no previous reports of this complication in conjunction with purine nucleoside therapy.

Prediction of severe disseminated adenovirus infection by serum PCR

Adenoviruses are increasingly recognised as viral pathogens that can cause fatal infections in immunocompromised patients, particularly recipients of haematopoietic stem-cell grafts. Adenovirus infections are not easily diagnosed and the development of a severe infection cannot be predicted by standard culture techniques. In a pilot study, we investigated the value of adenovirus DNA detection in serum as a marker of disseminated disease in 14 patients with defined patterns of adenovirus infections. The results show that the appearance of adenoviral DNA in serum preceded the development of a severe or fatal adenovirus infection. Because proper management is dependent on early diagnosis and differentiation from other conditions, this test may be a valuable tool in the management of adenovirus infection.

Adenoviral infection after allogeneic stem cell transplantation (SCT): report on 130 patients from a single SCT unit involved in a prospective multi center surveillance study

The incidence of adenovirus (AV) infections following SCT was determined in a prospective multicenter trial. Over 1 year, 130 consecutive patients undergoing allogeneic SCT at Essen University Hospital were included and followed for 6 months. Source of stem cells was blood in 68 cases. Fifty-eight patients had HLA-identical sibling donors. Throat swabs, urine and stool samples were screened weekly for AV antigen and DNA by ELISA and nested PCR, respectively. In 35 cases adenovirus infection was detected. There was no seasonal variation. Throat swabs were positive in 24, urine in 12, and stool in 11 cases, resulting in a cumulative risk of infection of 29%. The incidences of AV infection of the respiratory, gastrointestinal and urinary tract were 19%, 10%, and 9%, respectively, and infections were diagnosed after a median (range) interval of 44 (-2-179), 37 (-2-168), and 53 (17-153) days after transplantation. On multivariate analysis, presence of AV antibody in the donor and acute graft-versus-host disease grade IV were found to be independent risk factors for AV infection. Eleven patients had AV isolated from more than one site and five patients had probable AV disease. We were not able to identify patients in whom AV infection was the leading cause of death. The majority of patients infected with AV suffered from severe acute graft-versus-host disease often accompanied by other opportunistic infections, such as aspergillosis or CMV reactivation. Nineteen out of 36 patients who died during the observation period had AV infection. In summary, AV infection after allogeneic SCT was observed in a substantial number of patients. In addition to well-known risk factors for viral infection after SCT we were able to demonstrate that a positive AV antibody test in the donor is an important risk factor for AV infection. Further studies are needed, however, before final conclusions on the clinical sequelae of AV infection can be made and the role of preventive and therapeutic strategies toward AV infection after allogeneic SCT can be defined.

Fatal disseminated adenoviral infection in a renal transplant patient

Immunosuppressed patients are more susceptible to adenoviral infection and carry a significantly higher mortality than immunocompetent patients. Renal transplant patients with adenoviral infection most often present with infection of the kidney and urinary tract within weeks to months of transplant surgery, suggesting reactivation of the latent adenovirus in the immunosuppressed host as the source of infection. We describe the first case of a fatal adenovirus infection after several years of immunosuppression in a kidney transplant patient. Postmortem examination of several tissues, using standard viral culture and polymerase chain reaction, was positive for adenovirus serotype 21. This case is unusual in that the fatal disseminated viral infection occurred after 6 years of immunosuppression, suggesting that the source of adenovirus was a novel infection rather than reactivation of latent infection, or infection from the transplanted tissue. Furthermore, this is the first report of adenovirus type 21 in an immunosuppressed patient.

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.

Adenovirus infections in adult recipients of blood and marrow transplants

Adenoviruses are increasingly recognized pathogens that affect blood and marrow transplant (BMT) recipients. Experiences with 2889 adult BMT recipients were reviewed to study the incidence, clinical spectrum, risk factors for dissemination, response to therapy, and outcome of adenovirus infections. Eight-five patients (3%) were diagnosed by means of culture (n=85) or culture and histopathological examination (n=6). Nine patients had asymptomatic viruria, and 76 had symptomatic infections, which included upper respiratory tract infection (n=20), enteritis (n=18), hemorrhagic cystitis (n=10), pneumonia (n=15), and disseminated disease (n=13). The overall mortality rate was 26%. A higher mortality rate was observed among patients with pneumonia (73%) and disseminated disease (61%). Risk factors for dissemination included receipt of an allogeneic transplant, presence of graft-versus-host disease (GVHD), and receipt of concurrent immunosuppressive therapy. Intravenous ribavirin was not associated with an appreciable benefit among 12 patients who received this treatment. In conclusion, adenovirus infections are an important cause of morbidity and mortality in adult BMT recipients, particularly allogeneic transplant recipients with GVHD who are receiving immunosuppressive therapy. The need for an effective, nontoxic antiviral therapy is apparent.