High levels of adenovirus DNA in serum correlate with fatal outcome of adenovirus infection in children after allogeneic stem-cell transplantation

Adenovirus infection rates in pediatric recipients of alternate donor allogeneic bone marrow transplants receiving either antithymocyte globulin (ATG) or alemtuzumab (Campath)

Infectious complications due to adenovirus are of increasing concern after allogeneic stem cell transplantation. Over the past 4 years, we have modified our conditioning regimens to use alemtuzumab in preference to anti-thymocyte globulin (ATG) for pediatric patients receiving stem cell transplants from alternate donors. Recent reports in adult studies implicate alemtuzumab as a risk factor for adenovirus infection. We therefore evaluated the incidence of adenovirus infection in pediatric patients receiving either ATG or alemtuzumab in their conditioning regimens. Of the 111 patients evaluated, a total of 54 patients received ATG and 57 patients received alemtuzumab. In total, 35/111 (32%) patients were infected by adenovirus, and 9/111 (8%) had adenovirus disease (AD). Adenovirus infection was greater in the alemtuzumab group than the ATG group (23/57 vs 12/54) (P=0.039) and disseminated AD was more frequent in the alemtuzumab group vs the ATG group (8/57 and 1/54 respectively) (P=0.032). The presence of Grade 3-4 graft-versus-host disease was a risk factor for adenovirus infection. Our findings highlight the fact that adenovirus infection is a frequent complication after stem cell transplantation from alternate donors in the pediatric population and that alemtuzumab increases the risk of infection compared to ATG. This work will help in identifying at-risk populations for our upcoming immunotherapy trial using adoptively transferred donor-derived adenovirus-specific cytotoxic T lymphocytes.

Molecular detection and quantitative analysis of the entire spectrum of human adenoviruses by a two-reaction real-time PCR assay

Adenoviruses (AdV) can cause life-threatening infections in immunosuppressed patients. Reliable diagnostic tests are therefore of paramount importance. Apparently, any of the six AdV species (A to F), currently comprising 51 different serotypes, can play a clinically important role in patients with impaired immune response. It is imperative therefore that diagnostic assays cover the entire spectrum of these viruses. We have sequenced presumably conserved regions of the adenoviral genome in all AdV serotypes. Based on the complete sequence information of the hexon gene, we were able to develop a two-reaction real-time PCR assay covering all human adenoviruses with equally high specificity and sensitivity. The detection systems were tested using reference strains for all 51 serotypes and >1,000 clinical samples derived from peripheral blood and stool specimens from pediatric patients after allogeneic stem cell transplantation. The two-reaction assay presented permits highly specific detection and quantification of adenoviral DNA of any serotype. From the perspective of routine clinical diagnosis, the assay represents an important improvement over existing approaches by providing a sensitive and economic technique for early detection and monitoring of adenoviral infections.

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

Adenoviruses have been recognized as important pathogens in immunocompromised hosts. Particularly in pediatric allogeneic stem cell transplant recipients, the morbidity of the patients and mortality in those patients with disseminated infections have been found to increase over the last few years. Severe infections are predominantly but not exclusively caused by subgroup C adenoviruses. A multiplex real-time PCR assay using molecular beacons as probes was developed to enable monitoring of adenovirus DNA in those patients with simultaneous identification of subgroups. An internal control was coamplified in the multiplex PCR to check for the DNA isolation procedure as well as the presence of inhibitors in the clinical samples. The assay has been applied retrospectively in patient groups with different clinical outcomes of infection. In fatal cases, significantly higher adenovirus loads developed, exceeding even 10(11) copies/ml of serum or plasma. Patients with viral loads over 10(6) copies/ml appear to have an increased risk for fatal complications. This quantitative real-time PCR assay has been prospectively used clinically since 2002 to study the course of adenovirus infection. In addition, the assay provides objective start and end points of therapeutic interventions, including the clinically important evaluation of antiviral drugs.

Development of a PCR-based assay for detection, quantification, and genotyping of human adenoviruses

BACKGROUND

Adenoviruses (AdVs) can cause serious disease in immunosuppressed patients, particularly those undergoing allogeneic stem cell transplantation. A method for virus quantification in clinical specimens is essential for monitoring patient adenoviral loads and evaluating new therapeutic approaches.

METHODS

We developed a PCR-based assay that combines detection and genotyping of human AdVs, targeting a highly conserved region of the adenoviral genome coding for the DNA polymerase (AdV DPol PCR). We tested the diagnostic applicability of this PCR-based assay by analyzing 159 clinical specimens from children with respiratory disease and comparing the results with those obtained by nested PCR analysis.

RESULTS

The PCR assay detected all currently known AdV serotypes, with a detection limit of approximately 10 genome equivalents per reaction for 49 of 51 serotypes. No cross-reactivity to human DNA or other DNA viruses was observed. In addition, genotyping of PCR-positive samples was achieved within minutes by fluorescence curve melting analysis in a LightCycler instrument using 6 pairs of hybridization probes, each specific for a single AdV species. Results for clinical specimens were in good concordance with those obtained by nested PCR.

CONCLUSION

The presented assay is a suitable tool for the detection and genotyping of human AdVs in clinical samples.

Detection of adenovirus DNA in clinical samples by SYBR Green real-time polymerase chain reaction assay

BACKGROUND

Adenoviruses are associated with a variety of diseases including upper respiratory tract infections, acute conjunctivitis, cystitis and gastroenteritis. Adenoviruses can also cause fatal disseminated infections in patients undergoing stem cell transplantation. Measurement of adenovirus load in clinical samples from localized adenovirus infections or disseminated adenovirus infections may provide important information for analyzing the pathogenesis of various adenovirus infections. The purpose of the present study was to develop and optimize a highly sensitive real-time polymerase chain reaction (PCR) assay to detect a wide range of adenoviruses and to detect adenovirus DNA in clinical samples from immunocompetent children.

METHODS

Clinical samples of throat swabs and blood were collected from 111 patients suspected of having adenovirus infection. The copy number of adenovirus DNA was measured by real-time PCR assay.

RESULTS

SYBR Green real-time PCR assay is able to detect 10-10(6) copies of standard adenovirus DNA per run. Adenovirus DNA was detected in all culture-positive samples serotyped as 1, 2, 3, 4, 5, 6, 8 and 11. Viral loads on throat swabs from immunocompetent children with adenovirus infection ranged from 10(5) to 10(11) copies/mL. Adenovirus DNA was detected in 60% of blood samples and copy number ranged from 10(3) to 10(5) copies/mL.

CONCLUSION

SYBR Green real-time PCR is a useful quantitative tool for analysis of adenovirus DNA. The present results for immunocompetent children with adenovirus infections provided basic data for comparison with data obtained from immunocompromised patients.

Adenovirus infection in children after allogeneic stem cell transplantation: diagnosis, treatment and immunity

Human adenoviruses (HAdV) are a frequent cause of potentially fatal infections in patients after allogeneic stem cell transplantation, especially in children. Monitoring of serum/plasma by real-time quantitative PCR is a sensitive tool for the recognition of patients at risk of a potentially fatal infection and for the evaluation of the efficacy of treatment. Data from a retrospective study and from a prospective study demonstrate that recovery of immunity after transplantation is essential for the elimination of HAdV infection. The feasibility of several approaches for the manipulation of immunity in the immunocompromised host to prevent a fatal course of the infection is discussed.

Real-time quantitative PCR assays for detection and monitoring of pathogenic human viruses in immunosuppressed pediatric patients

A panel of 23 real-time PCR assays based on TaqMan technology has been developed for the detection and monitoring of 16 different viruses and virus families including human polyomaviruses BK virus and JC virus, human herpesviruses 6, 7, and 8, human adenoviruses, herpes simplex viruses 1 and 2, varicella-zoster virus, cytomegalovirus, Epstein-Barr virus, parvovirus B19, influenza A and B viruses, parainfluenza viruses 1 to 3, enteroviruses, and respiratory syncytial virus. The test systems presented have a broad dynamic range and display high sensitivity, reproducibility, and specificity. Moreover, the assays allow precise quantification of viral load in a variety of clinical specimens. The ability to use uniform PCR conditions for all assays permits simultaneous processing and detection of many different viruses, thus economizing the diagnostic work. Our observations based on more than 50,000 assays reveal the potential of the real-time PCR tests to facilitate early diagnosis of infection and to monitor the kinetics of viral proliferation and the response to treatment. We demonstrate that, in immunosuppressed patients with invasive virus infections, surveillance by the assays described may permit detection of increasing viral load several days to weeks prior to the onset of clinical symptoms. In virus infections for which specific treatment is available, the quantitative PCR assays presented provide reliable diagnostic tools for timely initiation of appropriate therapy and for rapid assessment of the efficacy of antiviral treatment strategies.

Quantitation of adenovirus genome during acute infection in normal children

BACKGROUND

Adenovirus infection causes a wide range of clinical illness in normal children. New molecular techniques allow quantitation of viral genome to study the natural history of adenovirus infection and viral load in normal children.

METHODS

Clinical samples were collected from 38 previously healthy, febrile children, and viral cultures were performed. Quantitative polymerase chain reaction (PCR) was used to detect adenovirus genome and to determine viral load. Adenovirus isolates were genotyped with a PCR-based assay.

RESULTS

Adenovirus culture was positive in 6 children who were diagnosed with acute adenovirus infection. Throat swabs contained high copy numbers of adenovirus genome (1.6 x 10(6)-6 x 10(7) copies/swab) from 4 of 4 adenovirus culture-positive children. Only 2 of 32 adenovirus culture-negative children had detectable adenovirus genome from throat swabs, but with a lower copy number (8 x 10(2) copies/swab). Adenovirus genome was not detected in blood samples from 5 of 6 adenovirus culture-positive children with uncomplicated upper respiratory tract infection and from all adenovirus culture-negative children. High level viremia (1.8 x 10(8)/ml) was detected in an adenovirus culture-positive 6-month-old infant with fever, pneumonia, conjunctivitis and hepatitis. Subsequent reduction in viral load paralleled her clinical recovery. Adenovirus viruria (1 x 10(9) copies/ml) with normal urinanalysis was detected in another adenovirus culture-positive child. All 6 adenovirus isolates were genotyped as adenovirus type 7h.

CONCLUSION

Viral load assessment in clinical samples determined by quantitative PCR can be useful in the diagnosis of adenovirus infection in immunocompetent, febrile children.

Adenovirus infections in stem cell transplant recipients: recent developments in understanding of pathogenesis, diagnosis and management

Adenovirus is increasingly recognized as an important pathogen in stem cell transplant recipients, reflecting increased awareness about the virus, together with changes in transplant practice such as the performance of more high-risk transplants, and improvements in diagnostic methods. In retrospective studies, the reported incidence of adenovirus infections ranged between 4-20% with a similar variation in the proportion of patients developing invasive disease. In contrast, the incidence of adenovirus infection varies between 20-30% in recent prospective studies on T-cell depleted or mismatched allografts and about 30-40% of these patients develop invasive disease. These prospective studies have established a relationship between the risk of invasive adenovirus disease and a number of factors such as the extent of T-cell depletion, the intensity of immunosuppressive therapy and the kinetics of lymphocyte recovery post-transplant. Polymerase chain reaction (PCR) assays to detect adenovirus DNA in peripheral blood have shown a strong correlation between viremia and the risk of disseminated adenovirus disease. These developments have led to the possibility of a preemptive antiviral treatment strategy for asymptomatic adenovirus infections. In addition, a better understanding of the interactions between adenovirus and host immune system in the post-transplant setting might enable development of effective immunotherapeutic strategies against adenovirus infections.

Viral loads in clinical specimens and SARS manifestations

A retrospective viral load study was performed on clinical specimens from 154 patients with laboratory-confirmed severe acute respiratory syndrome (SARS); the specimens were prospectively collected during patients' illness. Viral load in nasopharyngeal aspirates (n = 142) from day 10 to day 15 after onset of symptoms was associated with oxygen desaturation, mechanical ventilation, diarrhea, hepatic dysfunction, and death. Serum viral load (n = 53) was associated with oxygen desaturation, mechanical ventilation, and death. Stool viral load (n = 94) was associated with diarrhea, and urine viral load (n = 111) was associated with abnormal urinalysis results. Viral replications at different sites are important in the pathogenesis of clinical and laboratory abnormalities of SARS.

Monitoring of adenovirus infection in pediatric transplant recipients by quantitative PCR: report of six cases and review of the literature

Adenoviral (AdV) infections after transplantation remain a challenge in pediatric patients. Qualitative and quantitative PCR offer new approaches to early diagnosis and monitoring. However, their role in the management of AdV infections in pediatric transplant recipients remains to be determined. We report six children with positive qualitative serum-PCR for AdV on routine follow-up after transplantation (liver n = 4, hematopoetic stem cells (HSCT) n = 1, combined liver and HSCT n = 1). None of these children were symptomatic at the time of first detection of AdV. Two patients remained asymptomatic, one developed hemorrhagic cystitis and enteritis. Three children with positive PCR developed high viral load on quantitative PCR, all developed clinical AdV sepsis with further rising virus load. Despite antiviral therapy with cidofovir, these three patients died of septic multiorgan failure. Positive qualitative AdV-PCR from blood after pediatric transplantation is not necessarily followed by clinical disease. In case of positive AdV-PCR, monitoring by serial quantitative PCR is useful regarding treatment decision and prevention of fatal disease.

Prospective study of respiratory viral infections in pediatric hemopoietic stem cell transplantation patients

BACKGROUND

Community-acquired respiratory viruses are an important cause of respiratory disease in pediatric patients undergoing hemopoietic stem cell transplantation. However, there are no studies examining the impact of more rapid and sensitive diagnosis by real time polymerase chain reaction (PCR) in this population. We performed a prospective study to assess the impact of real time PCR diagnosis as well as protective isolation for community-acquired respiratory virus infections in pediatric patients undergoing hemopoietic stem cell transplantation.

METHODS

During a 2-year period, 39 pediatric patients undergoing hemopoietic stem cell transplantation were analyzed for presence of respiratory viruses. Samples were taken at regular intervals and analyzed by culture and newly developed real time PCR methods. All patients were cared for in protective isolation.

RESULTS

Respiratory symptoms were observed in 10 of the 39 cases (26%) and a virus was identified in 8 and 6 of these cases by PCR and culture, respectively. The PCR detected the respiratory infection a median of 8 days before culture. However, the morbidity of the respiratory infections was generally mild, and no mortality was observed. Additionally all infections were observed pretransplant or after discharge; no nosocomial infections were observed.

CONCLUSIONS

The real time PCR assay is more rapid and sensitive than culture and could be used to screen patients before transplant or as respiratory symptoms present for timely diagnosis.

Effect of Ribavirin on the Plasma Viral DNA Load in Patients with Disseminating Adenovirus Infection

Adenovirus (AdV) infections are an increasingly frequent and potentially fatal complication in allogeneic stem cell transplant recipients. To determine the antiviral potential of ribavirin in an unbiased way, 4 patients without immune recovery were prospectively analyzed by quantitative measurement of plasma AdV DNA load. Administration of ribavirin at the first signs of AdV dissemination was not accompanied by a decrease in the plasma AdV DNA load in any of these patients, and an increase in the AdV load was even documented in 3. These observations question the potential of ribavirin to improve the outcome for patients with disseminating AdV infection and support a critical evaluation of antiviral treatments for AdV infection that involves the kinetics of virus DNA load as an objective parameter of viral replication.

Adoptive immunotherapy for posttransplantation viral infections

Viral diseases are a major cause of morbidity and mortality after hemopoietic stem cell transplantation. Because viral complications in these patients are clearly associated with the lack of recovery of virus-specific cellular immune responses, reconstitution of the host with in vitro expanded cytotoxic T lymphocytes is a potential approach to prevent and treat these diseases. Initial clinical studies of cytomegalovirus and Epstein-Barr virus in human stem cell transplant patients have shown that adoptively transferred donor-derived virus-specific T cells may restore protective immunity and control established infections. Preclinical studies are evaluating this approach for other viruses while strategies for generating T cells specific for multiple viruses to provide broader protection are being evaluated in clinical trials. The use of genetically modified T cells or the use of newer suicide genes may result in improved safety and efficacy.

Multiplexed, real-time PCR for quantitative detection of human adenovirus

Adenovirus infection is becoming increasingly recognized as a cause of morbidity and mortality in the immunosuppressed patient population. While early detection and quantitation of adenovirus in peripheral blood has been suggested as a means of directing and monitoring antiviral therapy in these patients, few methods have been published, particularly with respect to viral quantitation. A multiplexed real-time PCR assay was developed that can quantitatively detect a wide range of known serotypes of human adenovirus, including all of subgroups A to C. This assay was compared to a qualitative, Southern blot-based PCR assay by using 45 peripheral blood specimens from 16 patients. There was 100% concordance between the two tests in terms of qualitative results. The real-time assay detected adenovirus in patient samples at levels from <200 to 266,681 copies/ml of blood. By using control viral samples, sensitivity was demonstrated to less than 10 copies of viral genome per reaction and quantitative linearity was demonstrated from 10 to 10(6) copies of input viral DNA. Equivalent sensitivity and linearity were demonstrated for 15 different reference serotypes of adenovirus. Eleven other viral serotypes have complete target region sequence homology to one or more of the strains tested. No cross-reactivity was noted with other commonly isolated viral species. Sequence analysis showed no significant homology with any other human pathogens (bacterial or viral). This assay allows rapid, sensitive, and specific quantitation of adenovirus and may have a significant impact on the care of immunocompromised patients at risk for disseminated viral infection.

Sequential Switching of Dna Polymerase and Thymidine Kinase-Mediated Hsv-1 Drug Resistance in An Immunocompromised Child

Sequential herpes simplex virus type 1 (HSV-1) isolates were obtained from a paediatric haematopoietic stem cell transplant (HSCT) patient who received prolonged therapy with acyclovir (ACV) followed by foscarnet (PFA) and topical cidofovir (HPMPC) for severe persistent mucocutaneous HSV-1 infection. The isolates were retrospectively studied for drug resistance. The first resistant isolate associated with clinical failure of antiviral therapy emerged 44 days post-ACV treatment initiation. Susceptibility testing revealed an ACV-resistant HSV strain that demonstrated cross resistance to PFA in the absence of any previous PFA treatment. The observed cross resistance was conferred by a single amino acid substitution, Ser724Asn, in the HSV DNA polymerase (DNA pol) gene. During the subsequent course of ACV therapy, the ACV/PFA-cross-resistant isolates were replaced by ACV-resistant, PFA-sensitive isolates. These isolates carried no DNA pol mutations, but had an Arg163His substitution in the thymidine kinase gene. Upon subsequent switching of antiviral therapy from ACV to PFA, the original ACV/PFA-cross-resistant DNA pol mutant re-appeared. Our study shows the emergence of different drug-resistant HSV variants during ongoing, unchanged ACV therapy. Furthermore, a rapid re-selection of the original resistant variant was observed after switch. For optimal antiviral management of HSV infections in HSCT recipients, therapeutic decisions should be guided by drug susceptibility results whenever therapeutic failure is observed and/or when changes in antiviral treatment are considered.

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: 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.