Adenoviral disease in pediatric solid organ transplant recipients

An observation: Could the spread of Adenovirus in South Asia pose a hazard to global public health?

Background

One of the most pressing issues in healthcare today is the prevention of Adenovirus (AdV) infections. Children and the elderly, both of whom have weaker immune systems than healthy adults, are more vulnerable to infection.

Discussion

India has been the epicenter of a recent AdV epidemic in the South Asian area. Most of the nations, bordering India are still developing and have very low per capita incomes, yet their citizens often cross into India for trade, medical care, and vacation.

Conclusion

We are concerned that an epidemic of the AdV might occur in the Indian subcontinent, spread to other nations, and eventually affect the whole world if effective preventative and diagnostic measures are not taken.

Adenovirus Infection in Hematopoietic and Solid Organ Paediatric Transplant Recipients: Treatment, Outcomes, and Use of Cidofovir

BACKGROUND

human adenovirus (hAdV) infection constitutes an important cause of morbidity and mortality in transplant recipients, due to their immune status. Among drugs currently available, cidofovir (CDF) is the most prescribed.

METHODS

Retrospective study of hAdV infection in paediatric transplant recipients from a tertiary paediatric centre, describing characteristics, management, and outcomes, and focused on the role of CDF.

RESULTS

49 episodes of infection by hAdV were detected during a four-year period: 38 episodes in patients that received allogeneic hematopoietic stem cell transplantation (77.6%) and 11 in solid organ transplant recipients (22.4%). Twenty-five patients (52.1%) were symptomatic, presenting mainly fever and/or diarrhoea. CDF was prescribed in 24 patients (49%), with modest results. CDF use was associated with the presence of symptoms resulting in lower lymphocyte count, paediatric intensive care unit admission, and high viral load. Other therapeutic measures included administration of intravenous immunoglobulin, reducing immunosuppression, and T-lymphocyte infusion. Despite treatment, 22.9% of patients did not resolve the infection and there were three deaths related to hAdV infection. All-cause mortality was 16.7% (8 episodes) by 30 days, and 32.7% (16 episodes) by 90 days, of which, 3 episodes (3/16, 18.8%) were attributed to hAdV directly.

CONCLUSIONS

hAdV infection had high morbidity and mortality in our series. CDF use is controversial, and available therapeutic options are limited. Transplant patients with low lymphocyte count are at higher risk of persistent positive viremias, and short-term survival of these patients was influenced by the resolution of hAdV infection.

Adenovirus: Epidemiology, Global Spread of Novel Types, and Approach to Treatment

Adenoviruses (AdVs) are DNA viruses that typically cause mild infections involving the upper or lower respiratory tract, gastrointestinal tract, or conjunctiva. Rare manifestations of AdV infections include hemorrhagic cystitis, hepatitis, hemorrhagic colitis, pancreatitis, nephritis, or meningoencephalitis. AdV infections are more common in young children, due to lack of humoral immunity. Epidemics of AdV infection may occur in healthy children or adults in closed or crowded settings (particularly military recruits). The vast majority of cases are self-limited. However, the clinical spectrum is broad and fatalities may occur. Dissemination is more likely in patients with impaired immunity (e.g., organ transplant recipients, human immunodeficiency virus infection). Fatality rates for untreated severe AdV pneumonia or disseminated disease may exceed 50%. More than 100 genotypes and 52 serotypes of AdV have been identified and classified into seven species designated HAdV-A through -G. Different types display different tissue tropisms that correlate with clinical manifestations of infection. The predominant types circulating at a given time differ among countries or regions, and change over time. Transmission of novel strains between countries or across continents and replacement of dominant viruses by new strains may occur. Treatment of AdV infections is controversial, as prospective, randomized therapeutic trials have not been done. Cidofovir has been the drug of choice for severe AdV infections, but not all patients require treatment. Live oral vaccines are highly efficacious in reducing the risk of respiratory AdV infection and are in routine use in the military in the United States but currently are not available to civilians.

Approach to infection and disease due to adenoviruses in solid organ transplantation

PURPOSE OF REVIEW

Adenoviruses are an important cause of morbidity and mortality of solid organ transplant patients and remain a clinical challenge with regard to diagnosis and treatment. In this review, we provide an approach to identification and classification of adenovirus infection and disease, highlight risk factors, and outline management options for adenovirus disease in solid organ transplant patients.

RECENT FINDINGS

Additional clinical data and pathologic findings of adenovirus disease in different organs and transplant recipients are known. Unlike hematopoietic cell transplant recipients, adenovirus blood PCR surveillance and preemptive therapy is not supported in solid organ transplantation. Strategies for management of adenovirus disease continue to evolve with newer antivirals, such as brincidofovir and adjunctive immunotherapies, but more studies are needed to support their use.

SUMMARY

Distinguishing between adenovirus infection and disease is an important aspect in adenovirus management as treatment is warranted only in symptomatic solid organ transplant patients. Supportive care and decreasing immunosuppression remain the mainstays of management. Cidofovir remains the antiviral of choice for severe or disseminated disease. Given its significant nephrotoxic effect, administration of probenecid and isotonic saline precidofovir and postcidofovir infusion is recommended.

Disparate Entry of Adenoviruses Dictates Differential Innate Immune Responses on the Ocular Surface

Human adenovirus infection of the ocular surface is associated with severe keratoconjunctivitis and the formation of subepithelial corneal infiltrates, which may persist and impair vision for months to years following infection. Long term pathology persists well beyond the resolution of viral replication, indicating that the prolonged immune response is not virus-mediated. However, it is not clear how these responses are sustained or even initiated following infection. This review discusses recent work from our laboratory and others which demonstrates different entry pathways specific to both adenovirus and cell type. These findings suggest that adenoviruses may stimulate specific pattern recognition receptors in an entry/trafficking-dependent manner, leading to distinct immune responses dependent on the virus/cell type combination. Additional work is needed to understand the specific connections between adenoviral entry and the stimulation of innate immune responses by the various cell types present on the ocular surface.

Adenovirus persistence, reactivation, and clinical management

Adenoviral infections continue posing a major threat in severely immunocompromised patients including particularly allogeneic stem cell transplant recipients. Although exogenous infections occur in some instances, the majority of invasive events appear to arise from viral reactivation. In the pediatric setting, adenoviruses were demonstrated to persist in the gastrointestinal tract, and the intestinal epithelium serves as the main site of viral replication preceding invasive infection. Regular monitoring of serial stool samples for the presence and load of adenoviruses has therefore become a routine diagnostic tool for post-transplant patient surveillance, and can serve as a trigger for early initiation of treatment. In the adult setting, the source of infection or reactivation is less clear, and monitoring of peripheral blood specimens is the predominant approach for patient surveillance. Timely initiation of antiviral treatment is reportedly required for prevention or successful control of disseminated disease mediated by adenoviruses, and appropriate diagnostic monitoring is therefore of paramount importance. Currently available antiviral agents and immune therapeutic approaches have not been able to entirely overcome the life-threatening courses of invasive adenoviral infections in the immunocompromised clinical setting.

Outcomes of human adenovirus infection and disease in a retrospective cohort of pediatric solid organ transplant recipients

Information about HAdV infection in SOT recipients is limited. We aimed to describe HAdV infection epidemiology and outcomes in a single-center retrospective cohort during the era of PCR availability. SOT recipients transplanted at the CHOP 2004-2013 were followed up for 180 days post-transplant. HAdV infection was defined as a positive HAdV PCR from a clinical specimen. HAdV disease was defined by organ-specific radiologic and/or laboratory abnormalities. No HAdV surveillance protocols were employed during the study period; testing was solely per clinician discretion. Progression of HAdV infection was defined as HAdV disease or ≥1-log viral load increase since a corresponding site's first positive specimen. Of the assembled 425 SOT recipients, 227 (52.6%) had ≥1 HAdV PCR. Twenty-four (10.6%) had ≥1 HAdV-positive PCR. HAdV-positive subjects were younger than uninfected subjects (2.0 years vs 6.5, P = 0.001). Infection incidence rates were highest in liver recipients (15.3%), followed by heart (8.6%), kidney (8.3%), and lung (4.2%). Four subjects (16.7%) met HAdV disease criteria at virus detection. Five subjects (20.8%) had progression of HAdV infection. All-cause mortality rates in positive and negative subjects were 0% and 3.9%, respectively. HAdV infection was infrequently detected in SOT recipients. Over one-third of HAdV-positive patients met disease criteria at detection or had infection progression, but none died. This low all-cause mortality raises questions about benefits of HAdV surveillance. Larger multicenter studies are needed to assess incidence variance by center and comparative effectiveness of therapeutic interventions.

Prospective Assessment of Adenovirus Infection in Pediatric Kidney Transplant Recipients

BACKGROUND

Adenovirus infection is associated with graft dysfunction and graft loss in pediatric cardiac, lung, and liver transplants in prior retrospective studies, but data in pediatric kidney transplant recipients is limited.

METHODS

We conducted a prospective single-center cohort study of 75 consecutive pediatric kidney transplant recipients who underwent monthly screening for adenovirus viremia and symptom assessment for 2 years posttransplant.

RESULTS

Adenovirus viremia was detected in 11 (14.7%) patients at a median onset of 173 days (interquartile range, 109-310 days) posttransplant, 6 (8%) had asymptomatic viremia, and 5 (6.7%) had symptomatic disease (2 with hematuria and 3 with an acute febrile respiratory illness). Viremic patients did not differ from nonviremic patients in age, immunosuppression management, or cytomegalovirus or Epstein-Barr virus serostatus, but were more likely to develop cytomegalovirus viremia during the first 2 years posttransplant. No patient had an increase in creatinine from baseline during the time of adenovirus viremia. In a Cox proportional hazards regression, subclinical adenovirus viremia was not associated with a faster time to a 30% decline in estimated glomerular filtration rate.

CONCLUSIONS

Adenovirus infection is common among pediatric kidney transplant recipients and frequently causes symptomatic disease; however, symptoms are often mild and are not associated with a decline in graft function. Routine monitoring for adenovirus viremia in pediatric kidney transplant recipients may not be warranted.

Virologic response with 2 different cidofovir dosing regimens for preemptive treatment of adenovirus DNAemia in pediatric solid organ transplant recipients

ADV is frequently seen in our pediatric SOT population. It presents in a variety of clinical presentation and can cause severe disease. In this population, there are very few studies to determine the safety of CDV as a potential therapeutic agent. We present the findings of our retrospective study evaluating the efficacy and safety of CDV as 2 separate dosing regimens. Regimen A uses the standard 5 mg/kg once a week (Regimen A), and the second uses the 1 mg/kg 3 times per week (Regimen B). Overall, the dosing regimen did not differ in nephrotoxicity, but Regimen B had a higher, although non-significant, rate of viral load clearance. This suggests that more frequent dosing at lower levels may be more efficacious without any significant side effects in our SOT population.

Adenovirus

Adenoviruses are a highly prevalent infection that can cause a range of clinical syndromes in immunocompromised patients, ranging from localized disease of the respiratory tract, gastrointestinal tract, or urinary tract to disseminated disease. Adenovirus infections may develop in this unique population as the result of primary infection or reactivation of latent virus. Disease can be potentially progressive with high rates of mortality in patients with pneumonia and disseminated disease. Fortunately, cidofovir and its lipid ester, brincidofovir, appear to be effective for the treatment of adenovirus, although neither is specifically approved for this indication. Adenovirus should always be considered when immunocompromised patients present with any clinical syndrome that could be compatible with adenoviral infection. Once disease is suspected, cultures or molecular testing of appropriate specimens should be obtained and blood should be sent for adenovirus polymerase chain reaction (PCR) whenever adenovirus is suspected. Monitoring of quantitative viral loads in blood is helpful in predicting response to therapy with a significant drop (>1 log) associated with a higher probability of clinical response.

Risks and Epidemiology of Infections After Intestinal Transplantation

Intestinal transplantation has become a well-accepted and successful procedure to save the lives of patients suffering from intestinal failure and who have developed life-threatening complications of parenteral nutrition. Advances in all aspects of care, from the role of multidisciplinary intestinal rehabilitation services prior to transplant to the development strategies for early recognition of infectious sequelae and even the increasing availability of preventive strategies, have led to improved outcomes and a dramatic decline in infection-associated morbidity and mortality in children undergoing intestinal transplantation. Improvements in surgical techniques and immunosuppressive regimens have been essential components in these improvements, reducing risk of infection through reduction of technical complications and more optimal immunosuppression regimens. In addition, the development of molecular tools for early recognition of viral pathogens and an understanding of the timing and risks for infection have allowed for earlier and more successful treatments. Despite these improvements, infectious sequelae remain an important problem in this population, and additional efforts are needed to further minimize the risk of infectious sequelae in those children requiring this procedure.

A Case of Adenovirus Viremia in a Pediatric Liver Transplant Recipient With Neutropenia and Lymphopenia: Who and When Should We Treat?

Human adenovirus (HAdV) is one of the most feared infections among immunocompromised patients. In particular, in liver transplant patients, HAdV has been implicated in acute liver failure with resultant mortality. The development of current molecular techniques and surveillance testing protocols have provided tools for early detection of HAdV infection, prior to or at the early onset of HAdV disease. Although reduction in immune suppression is the mainstay of therapy, many researchers have also advocated for early administration of antiviral therapy. In multiple reports, cidofovir treatment has been associated with declines in HAdV viral loads or clinical improvement in solid organ and bone marrow transplant recipients. However, there have also been case reports that raise questions about the effectiveness of antiviral therapy in controlling systemic HAdV disease. We report a case of a 26-month-old male recipient of a liver transplantation for hepatoblastoma who developed adenoviremia with an associated hepatitis and gastroenteritis. He recovered with reduced immune suppression but without antiviral therapy, thus avoiding potential toxicities associated with cidofovir therapy. This case a contrast to previous reports, and it highlights the ambiguity regarding which patients should receive HAdV-specific antiviral therapy. Additional knowledge regarding specific pediatric host factors and HAdV factors that predict poor outcomes are needed. Such information would allow clinicians to better stratify patients by risk at the time of adenoviremia detection so that low-risk patients are not unnecessarily exposed to medications with potential toxicities.

Structures and organization of adenovirus cement proteins provide insights into the role of capsid maturation in virus entry and infection

Adenovirus cement proteins play crucial roles in virion assembly, disassembly, cell entry, and infection. Based on a refined crystal structure of the adenovirus virion at 3.8-Å resolution, we have determined the structures of all of the cement proteins (IIIa, VI, VIII, and IX) and their organization in two distinct layers. We have significantly revised the recent cryoelectron microscopy models for proteins IIIa and IX and show that both are located on the capsid exterior. Together, the cement proteins exclusively stabilize the hexon shell, thus rendering penton vertices the weakest links of the adenovirus capsid. We describe, for the first time to our knowledge, the structure of protein VI, a key membrane-lytic molecule, and unveil its associations with VIII and core protein V, which together glue peripentonal hexons beneath the vertex region and connect them to the rest of the capsid on the interior. Following virion maturation, the cleaved N-terminal propeptide of VI is observed, reaching deep into the peripentonal hexon cavity, detached from the membrane-lytic domain, so that the latter can be released. Our results thus provide the molecular basis for the requirement of maturation cleavage of protein VI. This process is essential for untethering and release of the membrane-lytic region, which is known to mediate endosome rupture and delivery of partially disassembled virions into the host cell cytoplasm.

Adenovirus: current epidemiology and emerging approaches to prevention and treatment

Infections caused by adenoviruses are associated with significant morbidity and mortality in both hematopoietic stem cell and solid organ transplant recipients. The risk seems to be highest in allogeneic hematopoietic stem cell transplant recipients as well as heart, lung and small-bowel transplant recipients. Management of these infections may be difficult and includes reduction of immunosuppression whenever possible combined sometimes with antiviral therapy (mainly cidofovir). The currently available antiviral therapy is limited by the need for intravenous administration, potentially significant renal and hematologic toxicities. New emerging therapies such as brincidofovir and transfusion of adenovirus-specific T-lymphocytes may increase the available armamentarium for these potentially life-threatening infections.

What do we know about adenovirus in renal transplantation?

Adenoviruses are common pathogens that have the potential to cause opportunistic infections with significant morbidity and mortality in immunocompromised hosts. The significance of adenoviral infection and disease is incompletely known in the setting of kidney transplantation. Reported adenovirus infections in renal transplant recipients have typically manifested as hemorrhagic cystitis and tubulointerstitial nephritis, less severe diseases than often seen in other solid organ transplant recipients (i.e. pneumonia, hepatitis and enteritis). The prevalent adenovirus subgroups associated with cystitis and nephritis are B1 and B2 with the serotypes 7, 11, 34, 35. However, disseminated or severe adenovirus infections, including fatal cases, have been described in renal transplant recipients. There is uncertainty regarding monitoring of and treatment of this virus. Although not supported by randomized clinical trials, cidofovir is used for the treatment of adenovirus disease not responding to reduction of immunosuppression.

Treatment of adenovirus hepatitis with cidofovir in a pediatric liver transplant recipient

AdV hepatitis is a rarely reported complication after pediatric liver transplantation that is associated with high rates of morbidity, mortality and graft failure. Successful treatment of AdV relies on early diagnosis of disease by quantitative PCR measurement of adenoviral DNA in blood and histological evidence in tissue biopsy. Pharmacologic treatment largely consists of antiviral therapy with CDV, an acyclic nucleoside phosphonate analog and reduction in immunosuppression. This report describes a case of AdV hepatitis in a pediatric liver transplant recipient successfully treated with a modified, renal sparing dosing of CDV.

Crystal structure of human adenovirus at 3.5 A resolution

Rational development of adenovirus vectors for therapeutic gene transfer is hampered by the lack of accurate structural information. Here, we report the x-ray structure at 3.5 angstrom resolution of the 150-megadalton adenovirus capsid containing nearly 1 million amino acids. We describe interactions between the major capsid protein (hexon) and several accessory molecules that stabilize the capsid. The virus structure also reveals an altered association between the penton base and the trimeric fiber protein, perhaps reflecting an early event in cell entry. The high-resolution structure provides a substantial advance toward understanding the assembly and cell entry mechanisms of a large double-stranded DNA virus and provides new opportunities for improving adenovirus-mediated gene transfer.

Ileocecal intussusception with histomorphological features of inflammatory neuropathy in adenovirus infection

The pathophysiological mechanisms for ileocecal intussusception in children with adenovirus infection are not well characterized. Here we demonstrate coincidence of adenovirus infection and inflammatory neuropathy of myenteric plexus in two children with ileocecal intussusception. Inflammatory neuropathy, an unspecific morphological feature which is found in peristalsis disorders, was morphologically characterized by the influx of CD3 positive lymphocytes in nervous plexus. To our knowledge, this is the first report suggesting peristalsis disorders from inflammatory neuropathy as additional mechanism in the pathophysiological concept of adenovirus-associated ileocecal intussusception.

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.

Insights into adenovirus host cell interactions from structural studies

Human adenoviruses cause a significant number of acute respiratory, enteric and ocular infections, however they have also served as useful model systems for uncovering fundamental aspects of cell and molecular biology. In addition, replication-defective forms of adenovirus are being used in gene transfer and vaccine clinical trials. Over the past decade, steady advances in structural biology techniques have helped reveal important insights into the earliest events in the adenovirus life cycle as well as virus interactions with components of the host immune system. This review highlights the continuing use of structure-based approaches to uncover the molecular features of adenovirus-host interactions.

Chronic norovirus and adenovirus infection in a solid organ transplant recipient

A 10-month-old boy developed chronic diarrhea 2 months after a combined liver, pancreas, and small bowel transplant. Norovirus and adenovirus were detected in multiple stool specimens during a 114-day period. Enteric viral infectious should be considered in solid organ transplant recipients with chronic diarrhea.

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.

Renal pathology in the pediatric transplant patient

Renal transplantation is a therapeutic goal for children with advanced chronic kidney disease. There are many causes of renal dysfunction in children with allografts--the transplanted kidney can develop a variety of morphologic alterations leading to dysfunction. Evaluation of the kidney biopsy is one of the best methods of determining the cause of graft dysfunction. Rejection is a major cause of renal allograft failure in children. The morphologic hallmarks of acute antibody-mediated and cell-mediated rejection and chronic allograft nephropathy have been codified in classification strategies that are useful in adults and children. Viral infection and Epstein-Barr virus-driven posttransplant lymphoproliferative disease also occur in the pediatric transplanted kidney. Drug toxicity from immunosuppressive agents also causes characteristic morphologic alterations in the renal allograft. As the survival of pediatric heart and liver transplant patients improves, the incidence of immunosuppression therapy-related disease in the native kidney in these patients will likely become more important clinically. In addition to renal lesions related to the allograft state, glomerular disease can recur or occur de novo in renal allografts. Here, we describe the pathology of the more common morphologic lesions in kidneys of children with a renal allograft.

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.