Noroviral diarrhea in solid organ transplant recipients: An analysis of interventions and outcomes

Infectious Diarrhea in Kidney Transplant Recipients

Introduction Infectious diarrhea represents a significant and frequent complication among kidney transplant recipients, primarily due to the immunosuppressive therapy required to prevent graft rejection. This condition poses substantial risks to both graft function and patient survival, driven by increased susceptibility to opportunistic pathogens and potential medication-related gastrointestinal effects. This study aims to characterize the pathogen spectrum and associated risk factors of infectious diarrhea in a German cohort of kidney transplant recipients, providing insights into regional patterns and clinical implications. Methods A retrospective cohort study was conducted, analyzing 604 patients, including 436 kidney transplant recipients, who were hospitalized with infectious diarrhea (ICD-10 codes A00-A09) at the Universitätsklinikum Düsseldorf (UKD) between January 2019 and December 2023. Nontransplant patients (n = 168) were included as a comparison group to evaluate pathogen distribution and infection risk specific to immunosuppressive therapy in transplant recipients. Pathogen identification was performed focusing on stool samples. Data collected included transplantation status, dates of admission and transplantation, recurrence rates, and detailed immunosuppressive regimens. Statistical analyses were applied to evaluate pathogen distribution, temporal patterns, and the influence of immunosuppression on infection risk. Results The most prevalent pathogens identified among kidney transplant recipients were Clostridioides difficile (26.3%), cytomegalovirus (CMV, 12.3%), enteropathogenic Escherichia coli (EPEC, 8.6%), and norovirus (4.8%). Immunosuppression significantly heightened infection susceptibility, with Clostridioides difficile infections occurring notably more frequently and CMV-related diarrhea observed exclusively in the transplant cohort. Recurrence rates were elevated for both CMV and Clostridioides difficile, underscoring their clinical persistence. Temporal analysis revealed a median onset of CMV infections at approximately 13 months post-transplantation, with no significant seasonal variation. Conclusions The predominance of opportunistic pathogens such as Clostridioides difficile and CMV in kidney transplant recipients reflects the profound impact of immunosuppression on infection risk and pathogen profiles. These findings emphasize the necessity for enhanced diagnostic approaches in kidney transplant recipients, including early and comprehensive pathogen screening, and targeted prevention strategies, such as optimized and maybe prolonged CMV prophylaxis and stringent hygiene protocols for Clostridioides difficile. It emphasizes close monitoring of a potential viral load in blood samples, especially after cessation of the routine CMV prophylaxis after kidney transplantation. This study contributes to a better understanding of infectious diarrhea in this vulnerable population and lays the groundwork for improved clinical management, overall cost reduction, and future prospective research.

Reconstitution of Norovirus-Specific T-Cell Responses Following Hematopoietic Stem Cell Transplantation in Patients With Inborn Errors of Immunity and Chronic Norovirus Infection

BACKGROUND

Chronic norovirus infection (CNI) causes significant morbidity in immunocompromised patients. No effective prevention or treatment currently exists.

METHODS

Two patients with inborn errors of immunity, X-linked severe combined immunodeficiency (X-SCID) and DOCK8 deficiency, were followed longitudinally for clinical course, immune reconstitution, norovirus-specific T-cell (NST) response, B-cell reconstitution, and norovirus-specific antibody production. Samples were obtained in the peri-hematopoietic stem cell transplant (HSCT) setting before and after CNI clearance. The norovirus strain causing CNI was followed longitudinally for norovirus stool viral loads and sequencing.

RESULTS

The noroviruses were identified as GII.4 Sydney[P4 New Orleans] in 1 patient and GII.17[P17] in the other. An exacerbation of diarrhea post-HSCT in the patient with X-SCID was consistent with norovirus infection but not with graft-versus-host disease on pathologic samples. Both patients recovered polyfunctional NSTs in the CD4 and CD8 T-cell compartments that recognized multiple norovirus structural and nonstructural viral antigens. T-cell responses were minimal during active CNI but detectable after resolution. Mapping of NST responses between the patient with DOCK8 deficiency and his matched sibling donor were nearly identical. B-cell reconstitution or new endogenous antibody production for immunoglobulin A or immunoglobulin G was not observed.

CONCLUSIONS

This report is the first to demonstrate reconstitution of NST immunity after HSCT closely temporally aligned with clearance of CNI, suggesting that cellular immunity is sufficient for norovirus clearance.

Viral diarrheas - newer advances in diagnosis and management

PURPOSE OF REVIEW

Viruses are the most common etiological agents of diarrhea in children. Despite rotavirus vaccine introduction, rotavirus remains as the leading cause of death globally, followed by norovirus, which represents a diagnostic challenge. Here, we describe new advances in the diagnosis and management of viral diarrheas.

RECENT FINDINGS

Although immunoassays are widely used for their fast turnaround time and low cost, molecular techniques have become the most reliable diagnostic method due to their high sensitivity and capacity to analyze multiple pathogens in gastrointestinal panels. Isothermal nucleic acid amplification assays (LAMP and RPA) are promising techniques since they do not require sophisticated equipment and can be used as point-of-care testing. CRISPR/Cas nucleic acid detection systems are new diagnostic methods with great potential. Several recent published articles describe the role of human intestinal enteroids to characterize norovirus infection, to test new drugs, and for vaccine development. The interaction between the human gut microbiota and gastrointestinal viral infections has been extensively reviewed and offers some innovative mechanisms for therapeutic and preventive measures.

SUMMARY

Although important advances have been made, more research is needed to address remaining challenges and further improve diagnostic capabilities and better management strategies for this critical infectious disease.

Viral gastroenteritis

Since the discovery of norovirus in 1972 as a cause of what was contemporarily known as acute infectious non-bacterial gastroenteritis, scientific understanding of the viral gastroenteritides has continued to evolve. It is now recognised that a small number of viruses are the predominant cause of acute gastroenteritis worldwide, in both high-income and low-income settings. Although treatment is still largely restricted to the replacement of fluid and electrolytes, improved diagnostics have allowed attribution of illness, enabling both targeted treatment of individual patients and prioritisation of interventions for populations worldwide. Questions remain regarding specific genetic and immunological factors underlying host susceptibility, and the optimal clinical management of patients who are susceptible to severe or prolonged manifestations of disease. Meanwhile, the worldwide implementation of rotavirus vaccines has led to substantial reductions in morbidity and mortality, and spurred interest in vaccine development to diminish the impact of the most prevalent viruses that are implicated in this syndrome.

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.