Chronic Norovirus Infections in Cardiac Transplant Patients

Adult and late adolescent complications of pediatric solid organ transplantation

BACKGROUND

There have been over 51 000 pediatric solid organ transplants since 1988 in the United States alone, leading to a growing population of long-term survivors who face complications of childhood organ failure and long-term immunosuppression.

AIMS

This is an educational review of existing literature.

RESULTS

Pediatric solid organ transplant recipients are at increased risk for risk for cardiovascular and kidney disease, skin cancers, and growth problems, though the severity of impact may vary by organ type. Pediatric recipients often are able to complete schooling, maintain a job, and form family and social networks in adulthood, though at somewhat lower rates than the general population, but face additional challenges related to neurocognitive deficits, mental health disorders, and discrimination.

CONCLUSIONS

Transplant centers and research programs should expand their focus to include long-term well-being. Increased collaboration between pediatric and adult transplant specialists will be necessary to better understand and manage long-term complications.

Standardization of an antiviral pipeline for human norovirus in human intestinal enteroids demonstrates nitazoxanide has no to weak antiviral activity

Human noroviruses (HuNoVs) are the leading cause of acute gastroenteritis. In immunocompetent hosts, symptoms usually resolve within 3 days; however, in immunocompromised persons, HuNoV infection can become persistent, debilitating, and sometimes life-threatening. There are no licensed therapeutics for HuNoV due to a near half-century delay in its cultivation. Treatment for chronic HuNoV infection in immunosuppressed patients anecdotally includes nitazoxanide, a broad-spectrum antimicrobial licensed for treatment of parasite-induced gastroenteritis. Despite its off-label use for chronic HuNoV infection, nitazoxanide has not been clearly demonstrated to be an effective treatment. In this study, we standardized a pipeline for antiviral testing using multiple human small intestinal enteroid lines representing different intestinal segments and evaluated whether nitazoxanide inhibits replication of five HuNoV strains in vitro. Nitazoxanide did not exhibit high selective antiviral activity against any HuNoV strain tested, indicating it is not an effective antiviral for HuNoV infection. Human intestinal enteroids are further demonstrated as a model to serve as a preclinical platform to test antivirals against HuNoVs to treat gastrointestinal disease. Abstr.

A Standardized Antiviral Pipeline for Human Norovirus in Human Intestinal Enteroids Demonstrates No Antiviral Activity of Nitazoxanide

Human noroviruses (HuNoVs) are the leading cause of acute gastroenteritis. In immunocompetent hosts, symptoms usually resolve within three days; however, in immunocompromised persons, HuNoV infection can become persistent, debilitating, and sometimes life-threatening. There are no licensed therapeutics for HuNoV due to a near half-century delay in its cultivation. Treatment for chronic HuNoV infection in immunosuppressed patients anecdotally includes nitazoxanide, a broad-spectrum antimicrobial licensed for treatment of parasite-induced gastroenteritis. Despite its off-label use for chronic HuNoV infection, nitazoxanide has not been clearly demonstrated to be an effective treatment. In this study, we established a standardized pipeline for antiviral testing using multiple human small intestinal enteroid (HIE) lines representing different intestinal segments and evaluated whether nitazoxanide inhibits replication of 5 HuNoV strains in vitro . Nitazoxanide did not exhibit high selective antiviral activity against any HuNoV strains tested, indicating it is not an effective antiviral for norovirus infection. HIEs are further demonstrated as a model to serve as a pre-clinical platform to test antivirals against human noroviruses to treat gastrointestinal disease.

Norovirus disease among older adults

Norovirus, a leading cause of gastroenteritis outbreaks worldwide, results in substantial direct and indirect healthcare costs. Adults older than 65 years of age bear a significant proportion of the disease burden, and the disease course in this population is often more severe and protracted. In this narrative review, we discuss the epidemiology of norovirus infection, mechanisms of pathogenesis, and transmission pertinent to outbreaks along with infection prevention and control efforts. We also describe the clinical manifestations of norovirus disease with a focus on individuals older than 65 years of age, diagnosis and available treatment options, and the challenges and progress within vaccine development.

Infectious Gastroenteritis in Transplant Patients

Infectious gastroenteritis is common after transplantation and can lead to increased morbidity and mortality. A wide range of organisms can lead to gastroenteritis in this patient population. Clostridioides difficile, cytomegalovirus, and norovirus are the most common pathogens. Newer diagnostic methods, especially multiplex polymerase chain reaction, have increased the diagnostic yield of infectious etiologies. In this review, we describe the epidemiology and risk factors for common infectious pathogens leading to gastroenteritis.

Norovirus antivirals: Where are we now?

Human noroviruses inflict a significant health burden on society and are responsible for approximately 699 million infections and over 200 000 estimated deaths worldwide each year. Yet despite significant research efforts, approved vaccines or antivirals to combat this pathogen are still lacking. Safe and effective antivirals are not available, particularly for chronically infected immunocompromised individuals, and for prophylactic applications to protect high-risk and vulnerable populations in outbreak settings. Since the discovery of human norovirus in 1972, the lack of a cell culture system has hindered biological research and antiviral studies for many years. Recent breakthroughs in culturing human norovirus have been encouraging, however, further development and optimization of these novel methodologies are required to facilitate more robust replication levels, that will enable reliable serological and replication studies, as well as advances in antiviral development. In the last few years, considerable progress has been made toward the development of norovirus antivirals, inviting an updated review. This review focuses on potential therapeutics that have been reported since 2010, which were examined across at least two model systems used for studying human norovirus or its enzymes. In addition, we have placed emphasis on antiviral compounds with a defined chemical structure. We include a comprehensive outline of direct-acting antivirals and offer a discussion of host-modulating compounds, a rapidly expanding and promising area of antiviral research.

Successfully Treated Norovirus- and Sapovirus-Associated Diarrhea in Three Renal Transplant Patients

Objectives

To examine the burden of norovirus- and sapovirus-related diarrhea in renal transplant patients and to propose the use of nitazoxanide as a therapeutic option for treatment.

Methods

We reviewed three renal transplant patients with viral diarrhea requiring hospitalization due to acute renal failure and signs of graft rejection. All three patients were treated with nitazoxanide. We examined their clinical courses after therapy and compared time to resolution of symptoms and viral shedding.

Results

In all three renal transplant patients, improvement of diarrheal illness was witnessed within one week of nitazoxanide initiation.

Conclusions

Infectious diarrhea remains an underestimated yet significant cause of morbidity in solid organ transplant patients. Norovirus and sapovirus are often responsible for this presentation. Nitazoxanide was used as a treatment modality with success in reduction of symptoms, decreased duration of illness, and cessation of viral shedding.

Successful treatment of chronic norovirus gastroenteritis with nitazoxanide in a pediatric kidney transplant recipient

Uncontrolled studies suggest a benefit of nitazoxanide for the treatment of norovirus gastroenteritis in immunocompromised individuals. Here, we report the use of nitazoxanide in a 13-year-old male kidney transplant recipient who developed intractable norovirus gastroenteritis. Reduction of immunosuppression was not possible due to refractory TCMR. Administration of oral immunoglobulin and switching from tacrolimus to sirolimus failed to produce a meaningful clinical response. Treatment with a 14-day course of nitazoxanide resulted in prompt resolution of diarrhea as well as clearance of norovirus from the stool despite intense immunosuppression. Nitazoxanide may be considered as an option for the treatment of intractable norovirus gastroenteritis in pediatric transplant patients when reduced immunosuppression is not feasible or other treatment options have failed. Further studies to evaluate the safety and effectiveness of nitazoxanide in immunocompromised children are needed.

Norovirus Infection in Older Adults: Epidemiology, Risk Factors, and Opportunities for Prevention and Control

Norovirus is the leading cause of acute gastroenteritis. In older adults, it is responsible for an estimated 3.7 million illnesses; 320,000 outpatient visits; 69,000 emergency department visits; 39,000 hospitalizations; and 960 deaths annually in the United States. Older adults are particularly at risk for severe outcomes, including prolonged symptoms and death. Long-term care facilities and hospitals are the most common settings for norovirus outbreaks in developed countries. Diagnostic platforms are expanding. Several norovirus vaccines in clinical trials have the potential to reap benefits. This review summarizes current knowledge on norovirus infection in older adults.