Internally controlled real-time PCR monitoring of adenovirus DNA load in serum or plasma of transplant recipients

Human adenovirus replication in immunocompetent Syrian hamsters can be attenuated with chlorpromazine or cidofovir

BACKGROUND

Adenoviruses can cause severe toxicity in children and in immunocompromised adults, and therefore a means to abrogate replication would be useful. With regard to cancer treatment, replication competent oncolytic adenoviruses have been safe in humans, although their efficacy has been variable. Therefore, more effective agents are now entering clinical testing and, consequently, replication-associated side effects remain a concern. Preclinical analysis of replication related toxicity has been hampered by a lack of permissive models. Therefore, it has been difficult to study modulation of human adenovirus replication in immune competent animals.

METHODS

We investigated four different hamster carcinoma cell lines for transduction and cell killing potency in vitro and in vivo. Gene transfer was assessed using replication-deficient adenoviruses expressing luciferase. Cell killing was studied in vitro and in vivo using an oncolytic adenovirus that kills tumor cells by viral replication. After the most promising animal model had been selected, abrogation of virus replication was assessed in vitro and in vivo using a TCID(50) assay.

RESULTS

The results obtained suggest wild-type adenovirus replication in all four tested Syrian hamster cell lines and also normal organs. Virus replication could be abrogated with chlorpromazine, cidofovir and cytosine arabinoside, and the effect occurred subsequent to nuclear delivery of the viral genome. Attenuation of virus replication also was seen in vivo both in tumors and the liver.

CONCLUSIONS

Syrian hamsters may comprise a valuable immune competent model for evaluating anti-adenoviral drugs. Furthermore, chlorpromazine or cidofovir might be useful in case of adenovirus replication-associated symptoms in humans.

Viral pneumonias in immunocompromised adult hosts

Viral infections have always been considered pediatric diseases. However, viral pneumonia has become an important cause of morbidity and mortality in immuncompromised adults. Improved diagnostic techniques, such as the introduction of highly sensitive nucleic acid amplification tests, have not only allowed us to discover new viruses but also to determine the etiology of viral pneumonia in immunocompromised adult hosts. Unfortunately, only a few antiviral agents are available. Thus, early diagnosis and treatment are crucial to patient outcome. In this article, we review the most common viruses that have been implicated as etiologic agents of viral pneumonia in immunocompromised adults. We discuss the epidemiologic characteristics and clinical presentation of these viral infections and the most appropriate diagnostic approaches and therapies when available.

Comparison of in-house real-time quantitative PCR to the Adenovirus R-Gene kit for determination of adenovirus load in clinical samples

In the context of hematopoietic stem cell transplantation, adenovirus infections are associated with relevant mortality and morbidity. Detection of adenovirus DNA by quantitative PCR is the "gold standard" for these patients. A total of 150 samples, namely, 78 whole-blood, 22 cerebrospinal fluid, 24 digestive biopsy, and 26 stool samples, from 29 patients, including 24 hematopoietic stem cell transplant recipients, were tested for the detection of adenovirus using an in-house real-time quantitative PCR assay (A. Heim, C. Ebnet, G. Harste, and P. Pring-Akerblom, J. Med. Virol. 70:228-239, 2003) and the commercially available Adenovirus R-Gene kit. Adenovirus DNA was automatically isolated from whole-blood samples (Magna Pure LC system; Roche) or was manually extracted from other specimens (QIAamp; Qiagen) using the appropriate kit. The intra- and interassay reproducibilities and sensitivities were evaluated with cell culture supernatant dilutions. Of the 150 samples tested, 86 were found to be positive and 55 were found to be negative using both techniques. Nine (6%) discordant results were obtained. In most cases, discrepant results concerned samples with low viral loads. Quantitative results for all concordant positive samples were analyzed using the Spearman correlation test. A good correlation between the results of the in-house assay and those of the kit assay was obtained (r = 0.95; P < 0.001). Regarding the threshold cycle value for internal control spiked samples, none of the 150 samples tested contained a PCR inhibitor. In conclusion, a relevant correlation of results between the in-house assay and the kit assay, as well as the high-quality reproducibility and sensitivity of the kit assay, warranted its use for follow-up of hematopoietic stem cell transplantation recipients.

Combined CD8+ and CD4+ adenovirus hexon-specific T cells associated with viral clearance after stem cell transplantation as treatment for adenovirus infection

BACKGROUND

Human adenovirus can cause morbidity and mortality in immunocompromised patients after allogeneic stem cell transplantation. Reconstitution of adenovirus-specific CD4(+) T cells has been reported to be associated with sustained protection from adenovirus disease, but epitope specificity of these responses has not been characterized. Since mainly CD4(+) T cells and no CD8(+) T cells specific for adenovirus have been detected after allogeneic stem cell transplantation, the relative contribution of adenovirus-specific CD4(+) and CD8(+) T cells in protection from adenovirus disease remains to be elucidated.

DESIGN AND METHODS

The presence of human adenovirus hexon-specific T cells was investigated in peripheral blood of pediatric and adult allogeneic stem cell transplant recipients, who showed spontaneous resolution of disseminated adenovirus infection. Subsequently, a clinical grade method was developed for rapid generation of adenovirus-specific T-cell lines for adoptive immunotherapy.

RESULTS

Clearance of human adenovirus viremia coincided with emergence of a coordinated CD8(+) and CD4(+) T-cell response against adenovirus hexon epitopes in patients after allogeneic stem cell transplantation. Activation of adenovirus hexon-specific CD8(+) and CD4(+) T cells with a hexon protein-spanning peptide pool followed by interferon-γ-based isolation allowed rapid expansion of highly specific T-cell lines from healthy adults, including donors with very low frequencies of adenovirus hexon-specific T cells. Adenovirus-specific T-cell lines recognized multiple MHC class I and II restricted epitopes, including known and novel epitopes, and efficiently lysed human adenovirus-infected target cells.

CONCLUSIONS

This study provides a rationale and strategy for the adoptive transfer of donor-derived human adenovirus hexon-specific CD8(+) and CD4(+) T cells for the treatment of disseminated adenovirus infection after allogeneic stem cell transplantation.

Different cytokine signatures in children with localized and invasive adenovirus infection after stem cell transplantation

HAdV infection is a dangerous complication after pediatric SCT. In this study, we aimed at determining the cytokine profile in plasma samples in case of HAdV infection after SCT to gain more knowledge about the HAdV-specific immune response. In this prospective study, 47 pediatric SCT recipients were included in three yr. By using particle-based MIA, 17 different cytokines were analyzed in 41 plasma samples of patients with a localized HAdV infection (presence of HAdV in feces, urine or throat detected by culture) and patients with invasive HAdV infection (HAdV viremia in blood, detected by PCR). In patients with invasive HAdV infection, but not in patients with localized HAdV infection, the pro-inflammatory cytokines IL1beta, IL6, IL8, IL12, IFNgamma, TNFalpha, and also IL17, MIP1alpha, OSM, and IP10 were produced. The simultaneous release of the cytokines IL1beta, IL17, IL18, OSM, MIP1alpha, and IP10 was related to invasive HAdV infections. We also show that cytokine signatures can be helpful to differentiate invasive HAdV infection from GvHD and EBV infections. In conclusion, after SCT, children with invasive HAdV infection have a different cytokine profile compared with patients with a localized HAdV infection.

Adenovirus infections in solid organ transplant recipients

PURPOSE OF REVIEW

Adenoviruses are emerging as important viral pathogens in solid organ transplant recipients, impacting morbidity, graft survival and even mortality. This review will discuss the current understanding of the epidemiology, diagnosis and therapy of adenovirus infection in transplant recipients.

RECENT FINDINGS

Advances in the field include the use of polymerase chain reaction in the diagnosis of adenoviral infection, a better understanding of the epidemiology, immune response and potential new therapies, including preemptive and adoptive immunotherapy strategies. Adenoviral infections appear to be common, especially in pediatric solid organ transplant. Generally well tolerated, some high-risk patients may develop disseminated disease causing graft failure, which may lead to retransplant and/or death. Antiviral therapy and immunotherapy may play a role in these patients, although prospective controlled data are not available at this time.

SUMMARY

Although new tools and a better understanding of the epidemiology, risk factors and therapies for adenovirus are beginning to materialize, prospective, controlled trials, using careful definitions, and standardized methodologies need to be performed to more fully clarify these issues in solid organ transplant recipients.

Hemorrhagic cystitis secondary to adenovirus infection in a kidney transplant recipient: case report

Increasingly potent immunosuppressive agents have reduced the incidence of rejection of transplanted organs while increasing patient susceptibility to opportunistic infections and cancer. Adenoviruses are increasingly recognized as contributors to morbidity and mortality in stem cell and solid-organ transplant recipients. Clinical findings range from asymptomatic viremia to respiratory and gastrointestinal disease, hemorrhagic cystitis, and severe disseminated illness. We describe the first case in Chile of hemorrhagic adenovirus cystitis after renal transplantation in an adult.

Real time PCR for rapid determination of susceptibility of adenovirus to antiviral drugs

Human adenoviruses (HAdV) are associated with respiratory, ocular and gastrointestinal infections as well as potentially fatal disseminated disease in highly immunocompromised patients. Although there is no specific FDA approved treatment for HAdV infections, some antivirals are used in certain patients. The in vitro antiviral assays for HAdV are not standardized and are usually time consuming. The objective of this study was to evaluate a real time PCR assay for rapid determination of susceptibility of HAdV to antiviral drugs. The nucleoside analogue stavudine (d4T) was used as test drug in A549 cells infected with HAdV5. The antiviral assay measured the reduction of the HAdV DNA levels in culture supernatants by real time PCR using specific primers that amplify a conserved region of the hexon gene. This real time PCR assay demonstrated that stavudine was a selective inhibitor for HAdV5, since the effective concentration 50% (EC(50)) ranged from 0.08 to 0.12 mM at multiplicity of infection between 0.001 and 1. Furthermore, EC(50) showed a high correlation with plaque reduction and virus yield inhibition assays (r(2)=0.9938 and r(2)=0.9468, respectively). In conclusion, the real time PCR-based antiviral assay is rapid, reproducible and could replace classical and more labor-intensive infectivity assays.

A clinical algorithm identifies high risk pediatric oncology and bone marrow transplant patients likely to benefit from treatment of adenoviral infection

BACKGROUND

Adenoviral infections cause morbidity and mortality in blood and marrow transplantation and pediatric oncology patients. Cidofovir is active against adenovirus, but must be used judiciously because of its nephrotoxicity and unclear indications. Therefore, before introducing cidofovir use during an adenoviral outbreak, we developed a clinical algorithm to distinguish low risk patients from those who merited cidofovir therapy because of significant adenoviral disease and high risk for death.

OBJECTIVE

This study was conducted to determine whether the algorithm accurately predicted severe adenovirus disease and whether selective cidofovir treatment was beneficial.

STUDY DESIGN

A retrospective analysis of a pediatric oncology/blood and marrow transplantation cohort prealgorithm and postalgorithm implementation was performed.

RESULTS

Twenty patients with adenovirus infection were identified (14 high risk and 6 low risk). All low-risk patients cleared their infections without treatment. Before algorithm implementation, all untreated high-risk patients died, 4 out of 5 (80%), from adenoviral infection. In contrast, cidofovir reduced adenovirus-related mortality in the high-risk group postalgorithm implementation (9 patients treated, 1 patient died; RR 0.14, P<0.05) and all treated high-risk patients cleared their virus.

CONCLUSIONS

The clinical algorithm accurately identified patients at high risk for severe fatal adenoviral disease who would benefit from selective use of cidofovir.

Development of duplex real-time PCR for detection of two DNA respiratory viruses

A method was developed for the detection and quantitation of HAdV (human adenovirus) and HBoV (human bocavirus) based on a duplex real-time PCR, the AB PCR, using a Smartcycler instrument. A control real-time PCR was carried out on albumin DNA to standardise the non-homogenous respiratory samples. No cross-reactivity was observed with viruses or bacteria that could be found in the respiratory tract. The diagnosis rate using the AB PCR on clinical samples was 10.7%: 3.4% for HBoV detection, 6.9% for HAdV detection and 0.3% double detection HBoV-HAdV. The clinical and epidemiological characteristics of the HAdV- and HBoV-infected patients were evaluated. In the HAdV-positive group and the HBoV-positive group the samples were classified according to the severity of the disease. The HAdV viral load did not appear to be linked to the severity of the disease. Conversely, the difference between the two HBoV groups, severe and non-severe, was significant statistically when the comparison was based on the viral load (P=0.006) or after adjustment of the viral load to the number of cells in the samples (P=0.02).

[Multiple organ failure and disseminated adenoviral infection]

BACKGROUND

Peripheral blood stem cell transplantation is a frequent option, especially for patients with hematological malignancies.

CASE REPORTS

A first patient received this treatment for acute myeloblastic leukemia, the second for Richter's syndrome (follicular lymphoma). In both cases, allograft (unrelated donor, non myeloablative conditioning) was followed by graft versus host disease (GVH) requiring an immunosuppressive treatment. Respectively 15 and three months after graft, these two patients presented with multiple organ failure including very severe hepatic dysfunction. The diagnosis was made according to positive blood PCR, positive BAL, and hepatic histological findings.

DISCUSSION

Adenoviruses, frequent in pediatrics, can be responsible for extremely severe infections among immunocompromised adults. T lymphocyte depletion plays a key role.

CONCLUSION

Adenoviral infections can be fatal among immunocompromised patients. Diagnostic improvement should lead to early treatment, which however, remains to be clearly defined.

Antiviral therapy for respiratory tract infections

Viruses are important pathogens causing respiratory tract infections both in the community and health‐care facility settings. They are extremely common causes of morbidity in the competent hosts and some are associated with significant mortality in the compromised individuals. With wider application of molecular techniques, novel viruses are being described and old viruses are found to have new significance in different epidemiological and clinical settings. Some of these emerging pathogens may have the potential to cause pandemics or global spread of a severe disease, as exemplified by severe acute respiratory syndrome and avian influenza. Antiviral therapy of viral respiratory infections is often unnecessary in the competent hosts because most of them are self‐limiting and effective agents are not always available. In the immunocompromised individuals or for infections caused by highly pathogenic viruses, such as avian influenza viruses (AIV), antiviral treatment is highly desirable, despite the fact that many of the agents may not have undergone stringent clinical trials. In immunocompetent hosts, antiviral therapy can be stopped early because adaptive immune response can usually be mounted within 5–14 days. However, the duration of antiviral therapy in immunosuppressed hosts depends on clinical and radiological resolution, the degree and duration of immunosuppression, and therefore maintenance therapy is sometimes needed after the initial response. Immunotherapy and immunoprophylaxis appear to be promising directions for future research. Appropriate and targeted immunomodulation may play an important adjunctive role in some of these infections by limiting the extent of end‐organ damage and multi‐organ failure in some fulminant infections.

Detection of respiratory viruses by molecular methods

SUMMARY

Clinical laboratories historically diagnose seven or eight respiratory virus infections using a combination of techniques including enzyme immunoassay, direct fluorescent antibody staining, cell culture, and nucleic acid amplification tests. With the discovery of six new respiratory viruses since 2000, laboratories are faced with the challenge of detecting up to 19 different viruses that cause acute respiratory disease of both the upper and lower respiratory tracts. The application of nucleic acid amplification technology, particularly multiplex PCR coupled with fluidic or fixed microarrays, provides an important new approach for the detection of multiple respiratory viruses in a single test. These multiplex amplification tests provide a sensitive and comprehensive approach for the diagnosis of respiratory tract infections in individual hospitalized patients and the identification of the etiological agent in outbreaks of respiratory tract infection in the community. This review describes the molecular methods used to detect respiratory viruses and discusses the contribution that molecular testing, especially multiplex PCR, has made to our ability to detect respiratory viruses and to increase our understanding of the roles of various viral agents in acute respiratory disease.

Adenoviruses in immunocompromised hosts

SUMMARY

The number of patients with acquired immunodeficiency has grown steadily as a result of both a larger number of patients receiving solid organ and hematopoietic stem cell transplants and their longer survival times. The use of newer, more potent immunosuppressive regimens has increased the frequency of severe adenovirus infections. Human adenoviruses are a large group of viruses, represented by at least 52 serotypes with various genotypes divided into genomic clusters, and these may cause a broad variety of clinical manifestations. The development of molecular methods has increased the sensitivity and rapidity of adenovirus infection diagnosis. The implementation of PCR assays has significantly contributed to the identification of patients with disseminated adenovirus disease. More recently, the development of real-time PCR assays has permitted virus quantification and patient follow-up. There is no treatment for adenovirus with demonstrated efficacy, although cidofovir is widely used. Sensitive diagnostic tests for adenovirus can contribute to the early diagnosis and successful treatment of life-threatening adenovirus infections, especially in complex immunocompromised patients. The development of improved adenovirus therapy still remains a challenge. Adenovirus genetic diversity should be considered for diagnosis, typing, and therapeutic interventions.

Real-time PCR with an internal control for detection of all known human adenovirus serotypes

The "gold standard" for the diagnosis of adenovirus (AV) infection is virus culture, which is rather time-consuming. Especially for immunocompromised patients, in whom severe infections with AV have been described, rapid diagnosis is important. Therefore, an internally controlled AV real-time PCR assay detecting all known human AV serotypes was developed. Primers were chosen from the hexon region, which is the most conserved region, and in order to cover all known serotypes, degenerate primers were used. The internal control (IC) DNA contained the same primer binding sites as the AV DNA control but had a shuffled probe region compared to the conserved 24-nucleotide consensus AV hexon probe region (the target). The IC DNA was added to the clinical sample in order to monitor extraction and PCR efficiency. The sensitivity and the linearity of the AV PCR were determined. For testing the specificity of this PCR assay for human AVs, a selection of 51 AV prototype strains and 66 patient samples positive for other DNA viruses were tested. Moreover, a comparison of the AV PCR method described herein with culture and antigen (Ag) detection was performed with a selection of 151 clinical samples. All 51 AV serotypes were detected in the selection of AV prototype strains. Concordant results from culture or Ag detection and PCR were found for 139 (92.1%) of 151 samples. In 12 cases (7.9%), PCR was positive while the culture was negative. In conclusion, a sensitive, internally controlled nonnested AV real-time PCR assay which is able to detect all known AV serotypes with higher sensitivity than a culture or Ag detection method was developed.

Quantification of adenovirus DNA in unrelated donor hematopoietic stem cell transplant recipients

BACKGROUND

Adenovirus (AdV) infection is a life threatening condition in immunosuppressed patients. Quantitative AdV assays can improve the clinical management of these patients.

OBJECTIVES

To evaluate quantitative measurement of AdV DNA with PCR in blood from hematopoietic stem cell transplant (HSCT) recipients.

STUDY DESIGN

Quantitative PCR was used to measure viral DNA levels of AdV in consecutive blood samples from 40 HSCT recipients (27 adults and 13 children) during a 1-year post-engraftment period. All patients received grafts from unrelated donors and were given anti-T-cell antibodies in the conditioning regimen.

RESULTS

In the group of 40 patients, six (15%) had detectable AdV DNA in blood for different lengths of time. None of these six patients suffered from severe graft-versus-host disease. In three of the patients a high AdV viral load (>10,000 copies/mL) was detected, one of whom also had high viral load of EBV and CMV and one of EBV only. These three patients died within 2 months after detection of ADV viremia. A low AdV viral load (<500 copies/mL) was detected in three surviving patients and they did not have concomitant high viral load of neither CMV nor EBV.

CONCLUSIONS

AdV viremia was present in 15% of the HSCT recipients and a high AdV viral load was associated with fatal outcome. Screening for AdV DNA with quantitative PCR in blood may be of clinical importance in allogeneic HSCT recipients in order to prevent severe clinical virological complications.

Fatal adenovirus hepatitis during maintenance therapy for childhood acute lymphoblastic leukemia

Disseminated adenoviral infection with hepatitis is rare in children undergoing standard chemotherapy. We report on a 3(1/2)-year-old male with fatal adenovirus hepatitis receiving maintenance chemotherapy for acute lymphoblastic leukemia (ALL). Adenoviral hepatitis was proven by histology, viral culture, and PCR in a liver biopsy. Quantitative real-time PCR in the peripheral blood showed adenoviral DNA copy number >10(9)/ml. Despite aggressive supportive care and antiviral treatment with cidofovir, the patient died rapidly due to fulminant liver failure. Diagnostic and treatment options for adenovirus infection remain unsatisfactory for these patients. We propose suggestions for diagnosis and therapy.

Treatment of adenovirus pneumonia with cidofovir in pediatric lung transplant recipients

BACKGROUND

Adenovirus pneumonia results in significant morbidity and mortality in lung transplant recipients. Cidofovir allows for directed therapy but can result in nephrotoxicity. We report our experience with cidofovir for the treatment of adenovirus pneumonia in pediatric lung transplant recipients.

METHODS

In a retrospective review, we identified four cases of culture-proven adenovirus pneumonia in children who underwent lung transplantation at Texas Children's Hospital (TCH). All patients received cidofovir 1 mg/kg every other day or three times a week for a total of 4 weeks. Probenecid and intravenous hydration were administered in conjunction with the cidofovir. Intravenous immunoglobulin (IVIg) was given as adjunctive therapy, and immunosuppression was not modified during the treatment course.

RESULTS

The four cases of adenovirus pneumonia comprised 4 of the 54 (7%) lung transplantations performed at TCH from 2002 to 2006, and all were in children <3 years of age. All patients developed pneumonia within 2 months after transplantation. With cidofovir treatment, three of the four children survived. Among the survivors, two developed early bronchiolitis obliterans within 1 year after transplant, and one has continued to have good graft function at 2 years after transplant. All patients maintained normal renal function throughout the treatment course.

CONCLUSIONS

Pediatric lung transplant recipients <3 years of age are at increased risk of adenovirus pneumonia early after transplantation. Cidofovir, when used in the modified dosing regimen and in combination with IVIg and renal protection measures, is a safe and potentially effective treatment option for adenovirus pneumonia in lung transplant recipients.

Human adenovirus modulates surfactant phospholipid trafficking

Surfactant, highly enriched with phosphatidylcholine (PC), is secreted into the airspace by a classic apical secretory route, thereby maintaining lung stability. Herein, we show that adenoviral infection decreases surfactant PC in lungs by inhibiting its apical secretion and redirecting its export in alveolar cells by a basolateral route. These effects were not observed with replication-deficient adenovirus (Ad), specifically lacking early region 1 (E1) gene products. Adenoviral stimulation of basolateral PC export from cells was not observed after pharmacologic inhibition of ATP-binding cassette proteins, after introduction of small interfering RNA to the lipid pump ATP-binding cassette transporter A1 (ABCA1) or in ABCA1-defective human Tangier disease fibroblasts. Adenovirus and its E1A gene product increased ABCA1 levels by transcriptionally activating the ABCA1 gene. Thus, Ad lowers surfactant, in part, by triggering ABCA1-directed basolateral PC export, thereby limiting the cellular pool of surfactant PC destined for apical secretion. The results support a novel pathway, whereby a viral pathogen disrupts surfactant trafficking.

Quantification of adenovirus species B and C viremia by real-time PCR in adults and children undergoing stem cell transplantation

Adenovirus infection during stem cell transplantation is associated with high morbidity and mortality. Adenovirus species B and C have been the main causes for these infections; however, epidemiological details about the species are still unclear. To clarify the contributions of species B and C adenovirus, the DNA was tested serially by quantitative real-time PCR in peripheral blood, stool and urine of 32 patients (16 adults and 16 children) undergoing stem cell transplantation. Adenovirus species B viremia was detected in 10 of 16 adult and 6 of 16 pediatric transplant recipients. Adenovirus species C viremia was also detected simultaneously in five adult and three pediatric recipients. The stool and urine of patients with adenovirus viremia were also positive for the same adenovirus species as in blood. In contrast, in none of 50 healthy adult controls was adenovirus species B or C viremia detected. Among patients who developed adenovirus viremia, one adult recipient developed disseminated disease and died from multiple organ failure. The remaining patients experienced fever of several degrees and/or diarrhea during the period of adenovirus viremia; however, they all recovered without antiviral therapy. The results indicated that stem cell transplantation was frequently associated with adenovirus species B or C viremia, although it did not always cause serious infectious complications.

Adenovirus infection after allogeneic stem cell transplantation

Adenovirus infection after allogeneic hematopoietic stem cell transplantation (HSCT) is an emerging pathogen causing relevant morbidity and mortality, with preponderance in children. During the last years, basic research on the biology of the virus and host immune response ameliorated the diagnostic, surveillance, and therapeutic strategies. Risk factors for infection commonly have an impact on T-cell reconstitution, such as T-cell depleted graft, unrelated or HLA-mismatched donor transplantation, and GvHD. Weekly surveillance by PCR in stool and blood till day 100 or longer post-HSCT and pre-emptive therapy with cidofovir are the mainstay of the current approach to adenoviral infections post-HSCT. Since a sufficient host T-cell response is essential to clear the virus, diagnostic procedures for detection of virus-specific T-cells have recently been developed to assess the risk of the infection. Furthermore, adoptive immunotherapy is a new treatment option for patients with absent specific T-cell response and present systemic adenoviral infection.

Granzyme H destroys the function of critical adenoviral proteins required for viral DNA replication and granzyme B inhibition

Granzymes are key components of the immune response that play important roles in eliminating host cells infected by intracellular pathogens. Several granzymes are potent inducers of cell death. However, whether granzymes use additional mechanisms to exert their antipathogen activity remains elusive. Here, we show that in adenovirus-infected cells in which granzyme B (gzmB) and downstream apoptosis pathways are inhibited, granzyme H (gzmH), an orphan granzyme without known function, directly cleaves the adenovirus DNA-binding protein (DBP), a viral component absolutely required for viral DNA replication. We directly addressed the functional consequences of the cleavage of the DBP by gzmH through the generation of a virus that encodes a gzmH-resistant DBP. This virus demonstrated that gzmH directly induces an important decay in viral DNA replication. Interestingly, gzmH also cleaves the adenovirus 100K assembly protein, a major inhibitor of gzmB, and relieves gzmB inhibition. These results provide the first evidence that granzymes can mediate antiviral activity through direct cleavage of viral substrates, and further suggest that different granzymes have synergistic functions to outflank viral defenses that block host antiviral activities.

Assessment of disseminated adenovirus infections using quantitative plasma PCR in adult allogeneic stem cell transplant recipients receiving reduced intensity or myeloablative conditioning

OBJECTIVES

Disseminated adenovirus (AdV) infections following allogeneic stem cell transplantation (allo-SCT) are increasingly recognised, particularly in children. This study evaluated the clinical relevance of disseminated AdV infections in adult allo-SCT recipients, after different conditioning regimens.

METHODS

In a cohort of 107 adult allo-SCT recipients, receiving either reduced intensity conditioning (RIC, n = 48) or myeloablative conditioning (MAC, n = 59), AdV DNA levels in plasma were determined retrospectively at 1, 3 and 6 months following transplantation. Results of this screening regimen were compared with a cohort of 58 paediatric allo-SCT recipients, in whom AdV DNA load was monitored prospectively, as part of a pre-emptive treatment strategy. In positive cases, the course of AdV DNA load and clinical outcome were assessed.

RESULTS

AdV DNA levels > or =1000 copies/mL were detected in five adults (4.7%) and eight children (13.8%). Screening for AdV viraemia at 1, 3 and 6 months would have detected seven of eight paediatric patients. One adult, receiving MAC, died with disseminated AdV disease and in four (three RIC and one MAC) AdV viraemia was transient without clinical symptoms specifically attributable to AdV. Seven paediatric patients with AdV viraemia were pre-emptively treated with ribavirin or cidofovir and in three of them disseminated AdV infection was related to a fatal outcome.

CONCLUSIONS

Disseminated AdV infections following allo-SCT was a rare event in the adults and cause morbidity in a minority of these patients. In four of five adult patients, spontaneous clearance of AdV viraemia occurred. Results did not differ between the conditioning regimens that were applied in the adult cohort.

Treatment of adenovirus disease in stem cell transplant recipients with cidofovir

Invasive adenovirus (AdV) disease is fatal in >50% of allogeneic hematopoietic stem cell transplant (SCT) recipients. Treatment with cidofovir may improve outcomes based on in vitro susceptibility data and case reports. Six consecutive cases of invasive AdV disease treated with cidofovir were reviewed among 84 allogeneic adult SCT recipients (incidence, 7.1%). Cidofovir was administered intravenously at 5 mg/kg per dose (1-7 doses). All patients received intravenous immune globulin. Blood AdV DNA levels (viral loads, VLs) were monitored with a real-time quantitative polymerase chain reaction assay. Published reports of cidofovir treatment of AdV disease in SCT recipients were critically reviewed. The primary manifestations of AdV disease were hepatitis (n = 3), colitis (n = 2), and nephritis (n = 1). All patients had detectable AdV VLs, with peak values from 5 x 10(5) to 2 x 10(8) copies/mL. All patients received CD34+ selected grafts (n = 3) and/or had graft-versus-host disease (n = 4) and had CD4 counts <100 cells/mm3. Only 1 of 5 patients (20%) who received >or=2 doses of cidofovir died with active AdV disease. Four patients exhibited improvement within days of treatment with cidofovir as documented by clinical criteria and declines in AdV VLs (without a change in immunosuppression). In contrast, 1 patient treated late after onset of AdV disease died after 1 dose of cidofovir. In our review of 70 published cases treated with >or=2 doses of cidofovir, 13 (19%) died from AdV disease. In conclusion, early treatment of AdV disease with cidofovir inhibits viral replication in vivo and reduces mortality in allogeneic SCT recipients compared with historical data.

Sequential emergence of multiple adenovirus serotypes after pediatric stem cell transplantation

BACKGROUND

Adenovirus infections after allogeneic stem cell transplantation (SCT), particularly in children, may be severe and protracted. Up to 51 different serotypes of adenovirus are presently recognized but serotyping is usually limited to initial viral isolates.

OBJECTIVES

A systematic and sustained analysis of adenovirus serotypes in a cohort of adenovirus-infected pediatric SCT recipients, correlated to transplant-associated variables.

STUDY DESIGN

Eighty-three consecutive pediatric SCT recipients were studied by culture of feces and adenoviruses isolated were serotyped by neutralization. Upon persistent viral excretion, serotyping was repeated for at least two isolates of any infectious episode, including initial and final isolates, and patients with single and multiple serotypes were compared. In a subset of cases, serotyping of fecal isolates was compared to genotypic analysis.

RESULTS

In 33 patients, adenovirus was isolated at least once after SCT. Serotyping uncovered 49 different adenoviruses, including three isolates without an assigned serotype. In 16 patients, a single serotype was present for a sustained period, whereas 12 patients (36%) showed multiple serotypes. Comparison of these groups demonstrated more frequent non-malignant primary disease with multiple infections (p<0.01), but otherwise no significant differences were observed, although single serotype infections had a lower survival rate. Remarkably, serotype 31 appeared initially in 7 out of 12 patients with multiple infections. Genotyping by sequencing confirmed neutralization assays at least at the species level in 14 of 18 isolates.

CONCLUSION

In 36% of adenovirus infections after SCT more than one serotype could be detected by sequential analysis. Multiple serotypes occurred more often with non-malignant disorders. Adenovirus serotype 31 was often included. This finding is relevant for diagnostic purposes and immunotherapeutic interventions and provides insight into the pathogenesis of this problem.

Spectrum of viruses and atypical bacteria in intercontinental air travelers with symptoms of acute respiratory infection

Respiratory infections after air travel are frequent, but epidemiological data are incomplete. Using sensitive polymerase chain reactions, we studied the spectrum of atypical bacteria and respiratory viruses in travelers fulfilling the case definition of severe acute respiratory syndrome. A pathogen was identified in 67 travelers (43.2%). Influenza and parainfluenza viruses were most prevalent, at 14.2% and 15.5%, respectively. Prevalences of adenoviruses, human metapneumovirus, coronaviruses, and rhinoviruses ranged between 2.6% and 4.8%. Human bocavirus, respiratory syncytial virus, and Legionella, Mycoplasma, and Chlamydophila species were absent or appeared at frequencies of <1%. To our knowledge, these are the first specific baseline data for the mentioned agents in the context of air travel.

Respiratory Viral Infections in Transplant Recipients

A wide range of viruses affect the respiratory tract of transplant recipients, including adenovirus, influenza, human metapneumovirus, parainfluenza virus, respiratory syncytial virus (RSV) and rhinovirus. Prospective studies using contemporary diagnostic techniques have recently improved our understanding of the epidemiology and importance of these respiratory viruses among transplant recipients. From these studies, rhinovirus, in particular, has been shown to be one of the most common causes of infection in stem cell and lung transplant recipients. In addition to epidemiological data, recent studies have also advanced our understanding of management of influenza, adenovirus, and RSV infections among transplant recipients.

A rapid quantitative PCR-based assay for testing antiviral agents against human adenoviruses demonstrates type specific differences in ribavirin activity

Human adenovirus (HAdV) infections are increasingly frequent and potentially fatal as a disseminated disease in highly immunocompromised patients. Determining the in vitro sensitivity of HAdV to antiviral agents is not an easy task because HAdV CPE reduction assays are difficult to interpret and may take more than 1 week. We developed a phenotypic assay for testing the antiviral activity during the first round of replication using HAdV DNA concentration as an objective readout within 30 h. After evaluating the assay with cidofovir, we focused on determining the antiviral of ribavirin against different HAdV serotypes because clinical response of HAdV infections towards ribavirin treatment varied considerably. Several HAdV prototypes (1, 2, 5, 11, 31, 34, 48) associated with disseminated infections and clinical isolates were tested. Predominating HAdV of species C were more sensitive to ribavirin (HAdV-2 and -5: EC(50)<10 microM, EC(99) 111 and 104 microM, respectively) than HAdV of other species, for example HAdV-31 (EC(50) 56 microM, EC(99)>500 microM). Differential ribavirin sensitivity of HAdV types may contribute to the variable outcome of ribavirin therapy. Rapid screening of antiviral agents with the rapid qPCR-based assay against a multitude of HAdV serotypes may also facilitate development of future antiviral agents.

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.

Detection and monitoring of virus infections by real-time PCR

The employment of polymerase chain reaction (PCR) techniques for virus detection and quantification offers the advantages of high sensitivity and reproducibility, combined with an extremely broad dynamic range. A number of qualitative and quantitative PCR virus assays have been described, but commercial PCR kits are available for quantitative analysis of a limited number of clinically important viruses only. In addition to permitting the assessment of viral load at a given time point, quantitative PCR tests offer the possibility of determining the dynamics of virus proliferation, monitoring of the response to treatment and, in viruses displaying persistence in defined cell types, distinction between latent and active infection. Moreover, from a technical point of view, the employment of sequential quantitative PCR assays in virus monitoring helps identifying false positive results caused by inadvertent contamination of samples with traces of viral nucleic acids or PCR products. In this review, we provide a survey of the current state-of-the-art in the application of the real-time PCR technology to virus analysis. Advantages and limitations of the RQ-PCR methodology, and quality control issues related to standardization and validation of diagnostic assays are discussed.

Longitudinal observation of enterovirus and adenovirus in stool samples from Norwegian infants with the highest genetic risk of type 1 diabetes

BACKGROUND

Enterovirus and adenovirus are common in infancy, causing mostly asymptomatic infections. However, even an asymptomatic infection may be associated with increased risk of development of certain chronic non-infectious diseases, as has been suggested for enterovirus and type 1 diabetes. Data on occurrence and course of the infections in infancy are therefore important for designing effective approaches towards study of the association.

OBJECTIVES

To estimate the frequency of enterovirus and adenovirus infections in Norwegian infants, to evaluate the duration of the infections, to investigate their association with symptoms, and to establish a robust procedure that will be used to study the association between these viruses and the development of auto-immunity leading to type 1 diabetes.

STUDY DESIGN

Parents of infants, recruited for a study on environmental triggers of type 1 diabetes, submitted monthly samples of infant faeces, as well as information on symptoms of infection. The samples were analysed for enterovirus and adenovirus using quantitative real-time PCR, and enterovirus-positive samples were sequenced.

RESULTS

Enteroviruses were found in 142/1,255 (11.3%), and adenoviruses in 138/1,255 (11.0%) of stool samples. Approximately half of the infants were exposed to these viruses at least once during the first year of observation (period 3-14 months of age). The presence of adenovirus was associated with fever and with symptoms of cold but not with diarrhoea and vomiting. The enterovirus positivity was not associated with any symptoms.

CONCLUSIONS

The prevalence of enterovirus and adenovirus in longitudinally obtained faecal samples from infants is sufficiently high to enable studies of their association with chronic diseases. The present protocol for evaluating exposure to these viruses is well suited for large-scale efforts aimed at assessing possible long-term consequences, particularly in relation to type 1 diabetes.

Detection and monitoring of virus infections by real-time PCR

The employment of polymerase chain reaction (PCR) techniques for virus detection and quantification offers the advantages of high sensitivity and reproducibility, combined with an extremely broad dynamic range. A number of qualitative and quantitative PCR virus assays have been described, but commercial PCR kits are available for quantitative analysis of a limited number of clinically important viruses only. In addition to permitting the assessment of viral load at a given time point, quantitative PCR tests offer the possibility of determining the dynamics of virus proliferation, monitoring of the response to treatment and, in viruses displaying persistence in defined cell types, distinction between latent and active infection. Moreover, from a technical point of view, the employment of sequential quantitative PCR assays in virus monitoring helps identifying false positive results caused by inadvertent contamination of samples with traces of viral nucleic acids or PCR products. In this review, we provide a survey of the current state-of-the-art in the application of the real-time PCR technology to virus analysis. Advantages and limitations of the RQ-PCR methodology, and quality control issues related to standardization and validation of diagnostic assays are discussed.

Adenoviral disease in pediatric solid organ transplant recipients

Adenoviral disease in pediatric SOT recipients is emerging as an important viral pathogen, with serious consequences impacting morbidity, mortality and graft survival. The optimal diagnostic techniques, as well as therapy have yet to be established. This article reviews the current epidemiology of AdV in orthotopic liver, intestinal, cardiothoracic and renal transplant recipients. Issues related to diagnosis, notably the use of newer non-culture based viral detection methods and therapy, including anti-adenoviral agents and adoptive immunotherapy are discussed.

Adenovirus infection in paediatric stem cell transplant recipients: increased risk in young children with a delayed immune recovery

Adenovirus (HAdV) infections are a frequent cause of morbidity and mortality after allogeneic human stem cell transplantation (HSCT). We report a retrospective single-centre study on 328 consecutive paediatric recipients of an allogeneic HSCT. During the first 6 months after HSCT, HAdV infection occurred in 37 children (cumulative incidence 12%). The highest incidence was found in young children up to 5 years of age, transplanted after 1994, with >2 log T-cell depletion of a graft of another than an HLA-genotypically identical related donor (actuarial frequency at 6 months 84%). Persistence of HAdV and spreading of the virus over multiple sites showed a trend towards the development of HAdV disease or death, but did not reach significance. Recovery of immunity after HSCT, that is, serum concentrations of IgM and peripheral blood counts of T cells and subsets, was delayed in children with an HAdV infection compared with noninfected children. In seven out of seven patients with HAdV DNA in serum and decreasing lymphocyte counts, the infection had a fatal course. Manipulation of cellular immunity either by tapering of immunosuppression, infusion of donor lymphocytes or immunotherapy using HAdV-specific T cells should be considered in graft recipients at risk for a severe HAdV infection.