Early diagnosis of adenovirus infection and treatment with cidofovir after bone marrow transplantation in children

Conserved CTL epitopes on the adenovirus hexon protein expand subgroup cross-reactive and subgroup-specific CD8+ T cells

Adenoviruses often cause lethal infections in immunocompromised individuals. Adoptive transfer of immune T cells offers a therapeutic option, but this strategy has been hindered by the paucity of information on molecular targets of cellular immunity and by the immunologic heterogeneity of the 51 human adenoviruses, which are grouped from A to F on the basis of genome size, composition, homology, and organization. Clonal analysis of the adenovirus-specific cytotoxic T lymphocyte (CTL) responses of seropositive individuals identified 5 novel CD8+ T-cell epitopes, all located in conserved regions of the capsid protein hexon. Reactive T cells were cross-reactive between 2 to 4 groups, while no T cells specific for a single subgroup were detected. Thus, by exploiting these peptide targets, it is possible to prepare a T-cell population capable of reacting with most adenoviruses that cause disease in immunocompromised patients.

Cidofovir for treating adenoviral hemorrhagic cystitis in hematopoietic stem cell transplant recipients

Adenovirus (AdV) infection is an important cause of morbidity and mortality in hematopoietic stem cell transplant (HSCT) recipients. We treated 16 patients with AdV hemorrhagic cystitis (HC) following HSCT with cidofovir (CDV; 1 mg/kg/day, three times weekly for 3 weeks). Patients included 10 males and six females with a median age of 50 years (range 10-62). Two of the 16 patients were unevaluable because of early death from nonadenoviral causes. CDV therapy cleared AdV from urine in 12 of 14 patients (86%). Of 14 patients, 10 (71%) showed clinical improvements in HC. Among 14 patients, seven (50%) had avoided renal damage, the most important CDV toxicity. One patient previously treated with foscarnet for cytomegalovirus (CMV) required hemodialysis, and CDV treatment was discontinued. In another patient, CDV treatment was discontinued because of grade 2 nephrotoxicity. Four patients became positive for CMV antigenemia while being treated with CDV, and two developed herpes simplex virus (HSV) stomatitis while being treated with CDV. CDV proved effective in treating AdV HC in transplant patients. However, CDV at 1 mg/kg/day given three times weekly failed to prevent breakthrough infection with CMV and HSV in some patients.

Adenoviral infection in hematopoietic stem cell transplantation: early diagnosis with quantitative detection of the viral genome in serum and urine

Early diagnosis and prompt introduction of effective therapy are imperative to manage systemic, often fatal adenoviral (AdV) disease following hematopoietic stem cell transplantation (SCT). We evaluated the usefulness of real-time polymerase chain reaction (PCR) in the diagnosis of AdV disease in SCT recipients. Seven SCT recipients, including three with AdV disease, were retrospectively evaluated for AdV genome detection. In serum specimens, the AdV genome was detected at >10(3) copies/ml in the pre-SCT period in two of the five recipients studied. These two patients subsequently developed AdV disease. The three patients with AdV disease had high levels of >10(5) copies/ml during the 4-6 weeks post-SCT period. In none of these patients was the AdV genome detected in urine specimens in pre-SCT period. However, three recipients with detectable urinary levels during the period 1-2 weeks post-SCT subsequently developed AdV disease. Regarding the outcome, two of the three patients with AdV disease died of progressive renal failure. Our results suggest that quantitative determination of the AdV genome in serum and urine is useful to identify patients at high risk of developing AdV disease. Prospectively applied, these measures are expected to improve the dismal outcome of AdV disease in SCT recipients.

Evolution of an adenovirus outbreak in a multidisciplinary children's hospital

OBJECTIVE

To describe the course of an evolving adenovirus outbreak in a multidisciplinary children's hospital with a high-risk patient population.

METHODS

Observational study in a 280-bed university hospital during June 2002. Active case finding identified children with adenovirus infection. Data are median (interquartile range) or n (%). Adenovirus infection was diagnosed in 49 children, median age 12 months (4-33).

RESULTS

New cases were diagnosed over 26 days and peaked on day 17 (n = 15). Total infected inpatients peaked on days 17-21 (n = 36). Twenty-three infections (47%) were community-acquired and 26 (53%) hospital-acquired. Thirty-three children (67%) had a coexistent high-risk condition. Median hospital stay before and after diagnosis was 9 days (3-18) and 9 days (4-29), respectively. Twenty-two children (45%) were admitted to PICU. Overall hospital mortality was 22% (n = 11) and mortality attributed to adenoviral disease 12% (n = 6). Hospital mortality was similar between community- and hospital-acquired infections (22% compared to 23%) (P = 1.0). Twenty children (41%) received intravenous immunoglobulin (IVIG). Children treated with IVIG had a longer hospital stay (median 40 days vs 14 days) than those who did not receive IVIG (P = 0.01). Neither PICU mortality (29% vs 12%), nor hospital mortality (35% vs 14%), differed significantly between IVIG treated and untreated children (P = 0.76 and P = 0.16, respectively).

CONCLUSION

The rapid spread of hospital-acquired adenovirus underlines the importance of effective infection control measures. Despite nosocomial infection amongst high-risk patients, mortality was similar to that of community-acquired infection. Administration of immunoglobulin was not associated with demonstrable benefit. A prospective randomized trial would be required to resolve this issue.

Treatment of adenovirus infections in the immunocompromised host

Adenovirus infections are increasing as causes of morbidity and mortality in severely immunocompromised patients. The currently available antiviral agents, ribavirin and cidofovir, have yielded mixed results in case reports and small case series. Similar to cytomegalovirus disease, established adenovirus disease is often difficult to treat. Therapy may yield poor results, even when effective antiviral drugs are used. New strategies, including pre-emptive therapy, should be tested in prospective, clinical trials. New agents and adoptive transfer of specific T-cells to adenovirus might improve the current situation.

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.

Management of infectious complications in the hematopoietic stem cell transplant recipient

Despite impressive accomplishments in supportive care over the past decade, infections with a diverse group of microorganisms remain leading causes of morbidity and mortality after hematopoietic stem cell transplantation. The epidemiology of infectious complications has shifted substantially in the past decade with changes in antimicrobial prophylaxis, conditioning regimens, and graft manipulation, such that invasive mould infections and late viral infections are now the overriding concerns. Individual patient risk for infections is predicated on multiple disease-specific, patient-specific, and transplant-related factors but often tracks with the cumulative level of immunosuppression (such as dose of corticosteroids used for the treatment of graft vs host disease [GVHD]). New antivirals and antifungals have entered clinical practice and hold considerable promise for improved outcomes.

Isolation and expansion of human adenovirus–specific CD4+ and CD8+ T cells according to IFN-γ secretion for adjuvant immunotherapy

OBJECTIVE

In patients with lymphopenia following allogeneic stem cell transplantation adenovirus (ADV) infection is associated with high morbidity and mortality despite aggressive antiviral drug therapy. Virus-specific T cells seem to be essential for virus elimination. The aim of this study was to isolate and expand donor-derived human ADV-specific T lymphocytes for adoptive transfer of sufficient cell numbers to restore protective immunity after allogeneic stem cell transplantation.

MATERIALS AND METHODS

A clinical-grade strategy to generate ADV-specific T cells using the interferon-gamma (IFN-gamma) secretion assay, followed by expansion to numbers sufficient for clinical application with interleukin-2 (IL-2) and feeder cell stimulation, is described.

RESULTS

A mean number of 3.4 x 10(6) (+/-3 SD) ADV antigen-specific T lymphocytes were isolated from 0.1 to 2 x 10(9) mononuclear cells from peripheral blood (n=5) or leukapheresis products (n=6). Characterization of ADV-specific T cells after isolation revealed a mean purity of 85.1% (+/-12% SD) using antigen-specific intracellular cytokine staining. Isolated cells were expanded ex vivo for a median of 18 days (range 7-29 days; n=5) to greater than 10(8) total cells using IL-2 and autologous feeder cell stimulation. ADV-specific response to adenovirus antigen was confirmed in the generated T cell lines, using intracellular cytokine staining, IFN-gamma Elispot assay, and (3)H-thymidine uptake. Generated T-cell lines showed specific killing of ADV-infected B-LCL (n=4). Alloreactive proliferation of generated T-cell lines in mixed lymphocyte cultures was significantly reduced when compared to unmanipulated PBMCs.

CONCLUSION

Generation of adenovirus-specific T cells in a simple and rapid clinical-grade protocol was established, using IFN-gamma secretion assay with short expansion times, leading to sufficient numbers of ADV-specific T cells that can be used for adoptive immunotherapy.

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.

Clinical potential of the acyclic nucleoside phosphonates cidofovir, adefovir, and tenofovir in treatment of DNA virus and retrovirus infections

The acyclic nucleoside phosphonates HPMPC (cidofovir), PMEA (adefovir), and PMPA (tenofovir) have proved to be effective in vitro (cell culture systems) and in vivo (animal models and clinical studies) against a wide variety of DNA virus and retrovirus infections: cidofovir against herpesvirus (herpes simplex virus types 1 and 2 varicella-zoster virus, cytomegalovirus [CMV], Epstein-Barr virus, and human herpesviruses 6, 7, and 8), polyomavirus, papillomavirus, adenovirus, and poxvirus (variola virus, cowpox virus, vaccinia virus, molluscum contagiosum virus, and orf virus) infections; adefovir against herpesvirus, hepadnavirus (human hepatitis B virus), and retrovirus (human immunodeficiency virus types 1 [HIV-1] and 2 [HIV-2], simian immunodeficiency virus, and feline immunodeficiency virus) infections; and tenofovir against both hepadnavirus and retrovirus infections. Cidofovir (Vistide) has been officially approved for the treatment of CMV retinitis in AIDS patients, tenofovir disoproxil fumarate (Viread) has been approved for the treatment of HIV infections (i.e., AIDS), and adefovir dipivoxil (Hepsera) has been approved for the treatment of chronic hepatitis B. Nephrotoxicity is the dose-limiting side effect for cidofovir (Vistide) when used intravenously (5 mg/kg); no toxic side effects have been described for adefovir dipivoxil and tenofovir disoproxil fumarate, at the approved doses (Hepsera at 10 mg orally daily and Viread at 300 mg orally daily).

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.

Adenoviral infections in children: the impact of rapid diagnosis

BACKGROUND

Adenovirus (ADV) infections were difficult to diagnose in the past, and many infections were unrecognized. Direct fluorescent assay (DFA) for the rapid diagnosis of ADV infection, as part of a viral respiratory panel, became available at Primary Children's Medical Center (Salt Lake City, UT) in December 2000.

OBJECTIVE

To describe children with ADV infection diagnosed by DFA and viral culture and document the impact of rapid ADV testing on patient care.

METHODS

DFA testing for respiratory viruses including ADV was performed on nasal wash specimens with parallel viral culture. Chart review was performed for all ADV-positive patients identified from microbiology records between December 2000 and May 2002.

RESULTS

Of 1901 patients positive for respiratory viruses, 143 (7.5%) were ADV-positive by DFA or culture. The mean age of ADV-positive children was 23 months; 90% were <or=60 months old. Eighty percent were previously healthy, and 56% required admission with a mean length of stay of 3.4 days. The most common diagnoses included fever (31%), bronchiolitis (24%), and pneumonia (14%). Other conditions included suspected Kawasaki disease (KD) and hepatitis. Forty-six percent of ADV-positive children were given antibiotics at presentation, but only 2 (1.4%) had documented bacterial infection (one had Escherichia coli urinary tract infection and one had Moraxella catarrhalis bacteremia). Thirty-six percent of children had a change in management based on positive ADV DFA. In children with suspected KD (n = 5), 100% had positive ADV DFA, and immune globulin was withheld in 4. One immunocompetent patient with fulminant liver failure received cidofovir treatment after a positive ADV DFA and recovered before liver transplant.

CONCLUSIONS

ADV is a common infection in young children and often results in admission and unnecessary antibiotic therapy. Identifying ADV as the cause of illness can favorably impact care and in some instances may be life-saving. DFA testing for ADV should be considered for infants and children requiring admission for fever, respiratory illness, suspected KD, and hepatitis.

Real-time blood plasma polymerase chain reaction for management of disseminated adenovirus infection

We evaluated the usefulness of quantifying blood plasma adenovirus DNA loads for the management of adenovirus infection. Quantification of adenovirus A, B, and C DNA loads was done with real-time polymerase chain reaction (PCR) assays. Blood plasma specimens obtained from 44 immunocompromised patients were screened prospectively with this method. PCR findings for 36 patients were negative, and none of the patients developed disseminated adenoviral disease. PCR findings for 8 patients were positive; all 8 had invasive adenoviral disease and were treated with cidofovir. Sequential measurements of adenovirus DNA loads were performed to monitor the effect of cidofovir therapy. Decrease in the blood plasma DNA load was significantly higher in patients with a good response to cidofovir than in patients with a poor response and was therefore correlated with survival. Detection of adenovirus DNA in blood plasma appears to be useful for identifying patients at risk for invasive disease. Moreover, quantification of adenovirus DNA loads in plasma is helpful for monitoring the efficacy of antiviral therapy.

Fiber-modified adenoviruses generate subgroup cross-reactive, adenovirus-specific cytotoxic T lymphocytes for therapeutic applications

Adenovirus (Ad) infections are responsible for considerable morbidity and mortality, particularly in pediatric hematopoietic stem cell transplant (HSCT) recipients. To date there is no therapy. The present study was motivated by the potential for using adoptive immunotherapy as either prophylaxis or treatment for Ad infections and associated diseases. The authors have developed a protocol to reactivate Ad-specific memory T cells from peripheral blood mononuclear cells (PBMCs) using a clinical-grade adenoviral vector. Such lines contain a specific CD4 and CD8 T-cell component and are capable of recognizing and lysing target cells infected with wild-type Ad serotypes from different Ad groups. Furthermore, the frequency of Ad-specific precursors can be determined in PBMCs ex vivo and used as a means to assess changes in Ad-specific T-cell memory responses after infusion. This is the first report of a simple and reproducible method to activate and expand Ad-specific cytotoxic T lymphocytes (CTLs), which should be protective against the range of different Ad subtypes that affect transplant recipients.

Successful cidofovir treatment of adenovirus-associated hemorrhagic cystitis and renal dysfunction after allogenic bone marrow transplant

We present a patient who developed hemorrhagic cystitis and renal dysfunction after unrelated bone marrow transplantation. Polyoma BK virus and adenovirus 11 were detected in the urine. Vidarabine was administered without effect. Relatively low dose cidofovir was efficacious. Renal function improved, and the urinary secretion of adenovirus stopped.

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.

Lymphocyte data in Epstein-Barr-virus induced post-transplant lymphoproliferative disorder treated by rituximab

Viral infection is an important cause of morbidity and mortality in the post-allograft period. Recently, a new therapeutic approach was developed in post-transplant lymphoproliferative disorder (PTLD) induced by Epstein-Barr virus (EBV): the anti-CD20 monoclonal antibody or rituximab. We performed a single-center study on the treatment effectiveness of rituximab in three EBV-induced PTLD and evaluated biologic data, such as T and B lymphocytes count, during PTLD development and treatment. Before PTLD treatment, blood cell profile showed a severe T lymphopenia with a progressive increase of CD8+ cells and B lymphopenia. Secondly, during treatment, there appeared a T response, as in primary EBV, and a regressive B lymphopenia.

Changes of serum growth factors (IGF-I,-II and IGFBP-2,-3) prior to and after stem cell transplantation in children with acute leukemia

SUMMARY

Insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) may play an important role in tumor proliferation. This study aimed to investigate the IGF system in children with acute leukemia prior to and after hematological stem cell transplantation (HSCT). In 51 patients (AML n=27; ALL n=24; mean age 11.2+/-4.8 years), serum parameters (IGF-I,-II, IGFBP-2,-3) were investigated up to 18 months after HSCT by RIA. Patients with AML showed a significant increase of IGFBP-2 up to 100 days after HSCT (mean +/-s.d. prior to HSCT: 3.2+/-3.6 SDS vs 100 days after HSCT: 5.3 degrees +/-3.4 SDS, P=0.005). Furthermore, IGF-I and IGFBP-3 were significantly decreased (IGF-I: -0.3+/-1.5 vs -0.7 +/-1.2 SDS, P=0.001; IGFBP-3: -0.3+/-1.1 vs -1.0+/-1.1 SDS, P=0.02). Children with AML showed significantly higher IGFBP-2 (P=0.04) and significantly lower IGF-I (P=0.03) and IGFBP-3 (P=0.05) levels than children with ALL at day 100 after HSCT. We conclude that children with acute leukemia show important changes in the IGF system after HSCT. In particular, IGFBP-2 was significantly elevated at day 100 after HSCT. Increased IGFBP-2 and decreased IGF-I and IGFBP-3 may be associated with the increased proliferation rate of transplanted bone marrow.

Acute renal failure due to adenovirus-associated obstructive uropathy and necrotizing tubulointerstitial nephritis in a bone marrow transplant recipient

Management of post-transplant complications caused by severe adenoviral infection remains a major therapeutic challenge. A 17-year-old male who had undergone bone marrow transplantation for the treatment of acute lymphoblastic leukemia developed complete anuria following hemorrhagic cystitis 34 days after the transplant procedure. The computed tomogram scan revealed bilateral hydronephrosis, indicating acute renal failure because of obstructive uropathy. The emergency procedure of percutaneous nephrostomy caused massive bleeding in the left kidney, which eventually required a nephrectomy. Adenovirus-positive severe necrotizing tubulointerstitial nephritis was the histopathological diagnosis. Post-transplant acute renal failure because of hydronephrosis, which could be complicated by adenovirus-induced renal parenchymal disease, is of great concern and may cause significant problems with interventional treatment.

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.

The impact of adenovirus infection on the immunocompromised host

Adenovirus (Ad) infections in immunocompromised hosts have increased in frequency as the number of patients with transplants of bone marrow, liver, kidney, heart and other organs increase in number and survive longer. The numbers of such patients have also increased because of the emergence of the HIV epidemic. Ad infections with the 51 different serotypes recognised to date have few pathognomonic signs and symptoms, and thus require a variety of laboratory-based procedures to confirm infection. These viruses have the ability to target various organs with relative serotype specificity and can cause diverse manifestations including serious life-threatening diseases characteristic of the organs involved. Ads have cytolytic and immunoregulatory properties. The clinical dilemma remains the prompt recognition of Ad-related disease, the differentiation of Ad infection from Ad disease and the differentiation from other causative agents. Since the armamentarium of effective antiviral agents available to treat Ads is unproven by controlled trials and the virus is often not acquired de novo, it is difficult to prevent reactivation in immunodeficient hosts or new acquisition from donor organs. Timely discontinuation of immunosuppressive agents is necessary to prevent morbid outcomes. The clinical diseases, diagnostic tests, antiviral agents and biological aspects of the Ads as pathogens in immunocompromised patients are discussed in the context of this review. Some of the newer diagnostic tests are based on the well-studied molecular biology of Ads, which also have been attenuated by selective viral DNA deletions for use as vectors in numerous gene therapy trials in humans.

Cidofovir for adenovirus infections after allogeneic hematopoietic stem cell transplantation: a survey by the Infectious Diseases Working Party of the European Group for Blood and Marrow Transplantation

Adenovirus is an important cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation and there is no established therapy. Cidofovir has in vitro efficacy against adenovirus. We performed a retrospective analysis of 45 patients treated with cidofovir for adenovirus from 10 centers. In total, 16 patients had definite adenovirus disease, 13 probable disease, and 16 asymptomatic infections. A total of 31 (69%) patients were successfully treated with cidofovir, 10 failed, and four were not evaluable owing to early death from other causes. Cidofovir therapy was successful in 10 patients with adenovirus disease, 10 patients with probable disease, and in 10 patients with asymptomatic infections. The overall survival at 28 days and 6 months after initiation of cidofovir therapy was 76 and 46%, respectively. Of the patients, 18 developed toxicity associated with cidofovir: 14 developed renal toxicity and four other types of toxicities. We conclude that cidofovir may be useful against adenovirus after allogeneic hematopoietic stem cell transplantation but additional studies are needed.

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.

Adenovirus infection in pediatric liver and intestinal transplant recipients: utility of DNA detection by PCR

To evaluate the incidence of adenovirus (AdV) infection in pediatric liver and intestinal transplant recipients, the records of patients with possible AdV infection were reviewed for demographic data, symptomatology, methods of diagnosis, treatment and outcome. To evaluate the impact of polymerase chain reaction (PCR) amplification and identification of AdV DNA as a diagnostic test, the incidence and outcome of AdV before and after the introduction of PCR were compared. Adenovirus infection was identified in 4.1% of liver recipients and 20.8% of intestinal transplant recipients. The overall incidence of AdV did not increase over time, even following the introduction of PCR for virus detection. The higher incidence of AdV in the pediatric intestinal transplant recipients may be attributed to the frequent application of PCR methodology to intestinal biopsy material. Detection of AdV by PCR was associated with reduced mortality compared with detection by culture, either because of earlier detection of invasive disease or because PCR detects the presence of latent as well as active AdV.

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.

Sequence changes in the human adenovirus type 5 DNA polymerase associated with resistance to the broad spectrum antiviral cidofovir

Although there is currently no FDA approved antiviral treatment for adenovirus (Ad) infections, the broad spectrum antiviral cidofovir (CDV) has demonstrated potent inhibitory activity against many Ad serotypes in vitro and in an in vivo ocular replication model. The clinical potential of CDV prompted the assessment for the emergence of CDV resistance in Ad5. Serial passage of Ad5 in increasing concentrations of CDV resulted in derivation of four different Ad5 variants with increased resistance to CDV. CDV resistance was demonstrated by ability to replicate viral DNA in infected cells at CDV concentrations that inhibit the parental virus, by ability to form plaques in CDV concentrations of >20 microg/ml and by increased progeny release following infection and growth in media containing CDV. Using marker rescue, the loci for CDV resistance in variant R1 was shown to be mediated by one residue change L741S, one of two mutations within the R1 encoded DNA polymerase. The CDV-resistant variants R4, R5 and R6 also contained mutations in their respective DNA polymerase sequences, but these were different from R1; variant R4 contained two changes (F740I and V180I), whereas both R5 and R6 variants contained the non-conserved mutation A359E. R6 contained additional alterations L554F and V817L. The location of the R1 change is close to a region of the DNA polymerase which is conserved with other polymerases that is predicted to involve nucleotide binding.

Immune reconstitution after haematopoietic transplantation with two different doses of pre-graft antithymocyte globulin

Antithymocyte globulin is widely used before haematopoietic transplantation with HLA-matched unrelated donors or mismatched relatives to prevent rejection and graft-versus-host disease (GVHD). However, optimal dosage is still under debate. Thirty-one consecutive children, mainly with haematological malignancies, were transplanted in a single institution with such donors, selected by HLA-A -B compatibility by serology and DRB1* by DNA typing. Antithymocyte globulin (Thymoglobuline; Sangstat) was infused at days -3, -2, -1. Total dosage varied: 16 patients received a median of 7.5 mg/kg (2.5 to 10.5: low-dose group), and 15 a median of 15.5 mg/kg (14.4 to 19.4: high-dose group). Post-transplant GVHD prophylaxis consisted of cyclosporine, short-course methotrexate and steroids. CD3(+), CD4(+) and CD19(+) cell reconstitution was slower in the high-dose group. Median time to reach 100 CD4(+) cells was 8 months vs 4 months (P = 0.03). Median time to normal CD19(+) cells was 16 months vs 8 months (P = 0.01). CD16(+)CD56(+) and CD8(+) cell reconstitution was similar. Nine patients in the high-dose group and two in the low-dose group experienced life-threatening opportunistic infections (P = 0.009). Although obtained from a limited number of patients, our data suggest that a higher pre-graft dose of antithymocyte globulin may negatively influence immune reconstitution.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Intravenous ribavirin treatment for severe adenovirus disease in immunocompromised children

BACKGROUND

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

OBJECTIVE

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

DESIGN/METHODS

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

RESULTS

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

DISCUSSION

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

CONCLUSIONS

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

Adenovirus inhibition by peptidomimetic integrin antagonists

Many viruses and bacterial pathogens are capable of exploiting host cell surface integrins during their replication cycles. The ligands for many integrins contain an arginine-glycine-aspartic acid (RGD) amino acid sequence that is essential for protein-protein interaction. Human adenovirus particles contain this sequence in the penton base protein, and previous studies support a role for this RGD in integrin-dependent internalization of the virus by the cell. As synthetic peptidomimetics of RGD have been shown in other experimental systems to be antagonists of the activities of specific integrins both in vitro and in vivo, we sought to determine whether these small molecules are antagonists of adenovirus infection. Such compounds inhibited viral infection of cultured cells with similar rank order potency to that determined in assays utilizing purified extracellular matrix proteins as integrin ligands. The maximal level of inhibition achieved with the peptidomimetics was comparable to that of RGD-containing peptides, whereas no significant effects were apparent with an RGE-containing peptide. An engineered adenovirus having a mutated RGD sequence in the penton base was not susceptible to the inhibition. The results obtained with these synthetic antagonists, which have varied structures and potencies, suggest that integrins interact with adenoviral RGD in a manner similar to that of other protein ligands such as vitronectin. Furthermore, the results confirm the role of RGD in the replication cycle, and suggest peptidomimetic compounds may be useful antimicrobial agents in the treatment of a variety of diseases.

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.

Rapid and sensitive detection of respiratory virus infections for directed antiviral treatment using R-Mix cultures

BACKGROUND

The development of new anti-influenza drugs has led to concerns regarding the impact on healthcare costs if they are used indiscriminately. Restricting their use to proven influenza virus infections has the potential to overcome costly inappropriate therapy. However, conventional culture (CC) does not generate results quickly enough to facilitate the timely initiation of treatment, and rapid detection tests have suboptimal sensitivity. We therefore investigated a new rapid culture system (R-Mix) that contains a mixture of two cell lines and detects respiratory viruses within 24 h.

OBJECTIVES

To compare the analytical sensitivity of R-Mix with CC and rapid detection methods, for the detection of influenza and other respiratory viruses. To compare the clinical sensitivity of R-Mix with CC and direct antigen detection for the detection of respiratory viruses in primary and acute care settings.

STUDY DESIGN

Stock cultures of influenza virus were titrated and tested by R-Mix, ZstatFlu and FLU OIA. Stock cultures of adenovirus and parainfluenza virus type 3 were titrated and tested by R-Mix and CC. Specimens, which had previously tested positive for influenza viruses, were titrated and tested by R-Mix and CC. In symptomatic patients, the majority of whom were from primary care settings, 124 sequential specimens were tested for influenza viruses by immunofluorescent direct antigen detection and R-Mix. A separate set of 111 sequential specimens, from various symptomatic patient groups, were tested for influenza viruses by CC and R-Mix. Additionally, in acute care patients being surveillance tested during periods of immunosuppression, 155 specimens were tested for respiratory viruses (influenza A and B, parainfluenza 1-3, adenovirus and respiratory syncytial virus (RSV)) by CC and R-Mix.

RESULTS

With titrated stock cultures, R-Mix showed an analytical limit of detection of ten infectious virus particles per vial for influenza A, compared with 100,000 particles per test for FLU OIA and 1,000,000 for ZstatFlu. R-Mix also showed a 100-fold greater sensitivity for the detection of influenza A and equivalent sensitivity for the detection of influenza B when compared with CC in titrated known positive specimens. Further, it showed equivalent sensitivity to CC for the detection of adenovirus and parainfluenza virus type 3 in titrated stock cultures. Among prospective specimens from symptomatic patients, the sensitivity of R-Mix, CC and direct antigen detection tests (DAT) for influenza virus detection, was 100, 67 and 66%, respectively, and the specificity was 100, 100 and 98%, respectively. In surveillance specimens from immunosuppressed patients, the sensitivities of R-Mix and CC for respiratory virus detection were equivalent. Moreover, R-Mix results were available within 24 h, and by altering the antibody staining reagents either influenza viruses, or all seven major respiratory viruses, could be detected and distinguished in a single test.

CONCLUSIONS

R-Mix is a simple, rapid and sensitive system for the detection of influenza viruses that facilitates the restriction of antiviral drugs to patients with culture-confirmed infections.

O-Phosphonatomethylcholine, its analogues, alkyl esters, and their biological activity

O-Phosphonatomethylcholine, an isopolar phosphocholine analogue with a phosphonomethyl ether group replacing a phosphomonoester residue, was prepared by reaction of diisopropyl 2-chloroethoxymethylphosphonate with dimethylamine followed by quaternization of the thus-obtained diisopropyl 2-dimethylaminoethoxymethylphosphonate with iodomethane; the ester groups in the quaternary intermediate were cleaved with bromotrimethylsilane. Replacement of dimethylamine in the reaction sequence by morpholine and/or pyrrolidine gave the N-methylmorpholinium or N-methylpyrrolidinium analogues of O-phosphonatomethylcholine. Reaction of O-phosphonomethylcholine monotetrabutylammonium salt with 1-bromoalkanes in acetonitrile afforded a series of the corresponding monoalkyl (C10-C16) esters. None of these compounds except for the hexadecyl ester exhibited any appreciable cytostatic activity against DU-145, H460, HT-29, or MES-SA cell lines in vitro (evaluated by 3H-Thd incorporation assay). The hexadecyl ester exhibited modest in vitro cytotoxic activity comparable to that of the anticancer drug miltefosine (hexadecyl O-phosphocholine). In vivo evaluation of hexadecyl O-phosphonomethylcholine [transplanted SD lymphoma in inbred SD/cub rats, 10 mg kg(-1) day(-1) intratumoral injection for 10 days] resulted in a 40% decrease in lymphoma mass.

Hematopoietic stem cell transplantation: current status of old issues

Since 1968 hematopoietic stem cell transplantation (HSCT) has progressed from an experimental to standard therapeutic procedure. There are many obstacles to the successful outcome of HSCT procedures. Some of these obstacles are lack of healthy histocompatible donors, graft versus host disease, graft rejection and infections. Many advances have been made to overcome these obstacles with significant success. However, these issues and associated problems continue to persist at different levels as the field evolves with expanding indications for HSCT, use of alternative sources for hematopoietic stem cells and alternative transplant procedures. Newer interventions have allowed us to overcome some of these obstacles.