Diarrhea caused by viruses in transplant recipients

Presentation, management, and outcomes of norovirus in adult and pediatric solid organ and hematopoietic stem cell transplant recipients: A multicenter, retrospective study

BACKGROUND

Norovirus (NoV) can cause chronic relapsing and remitting diarrhea in immunocompromised patients.  Few multicenter studies have described the clinical course, outcomes, and complications of chronic NoV in transplant recipients.

METHODS

A multicenter retrospective study of adult and pediatric SOT and HSCT recipients diagnosed with NoV between November 1, 2017, and February 28, 2021. Data were obtained from electronic medical records (EMR) and entered into a central REDCap database. Descriptive statistics were calculated.

RESULTS

A total of 280 NoV+ patients were identified across eight sites. The majority were adults (74.1%) and SOT recipients (91.4%). Initial diagnosis of NoV occurred a median of 36 months post-Tx (IQR [15.0, 90.0]). Most NoV cases had >3 diarrheal episodes daily (66.0%), nausea and vomiting (60.1%). Duration of diarrhea varied greatly (median = 10 days, mean = 85.9 days, range (1, 2100)). 71.3% were hospitalized. Adjustment of immunosuppression, including reduction and discontinuation of mToR inhibitor, CNI, and/or MMF, was the most common management intervention for NoV. Other therapies resulted only in temporary improvement. Four patients died within 30 days and three others died by 180 days postdiagnosis. Clinically significant renal dysfunction was observed in 12.5% by 30 days and 21.4% by 180 days post-NoV diagnosis.

CONCLUSION

In HSCT and SOT patients, NoV frequently resulted in severe symptoms, prolonged diarrhea (30% persistent with diarrhea for >30 days), and clinically significant renal dysfunction (up to 21% of patients). Utilized therapies did not reliably result in the resolution of infection demonstrating the need for more effective treatment.

Sapovirus: an emerging pathogen in kidney transplant recipients?

PURPOSE

Diarrhea is an important cause of morbidity and mortality in immunocompromised patients. After including sapovirus to the viral gastroenteritis screening of our institution's laboratory, we noticed an increase in sapovirus infections among kidney transplant recipients. Therefore, we assumed former gastrointestinal tract infections with unidentified pathogens could have been caused by sapovirus. To better understand the characteristics of a sapovirus infection in a high-risk group we initiated this study.

METHODS

Over a period of 6 months, all transplant recipients with diarrhea and later identified viral/unknown pathogens were included. Kidney function, levels of immunosuppressants and  c-reactive protein, acid-base balance, onset of symptoms and time of hospitalization were analyzed.

RESULTS

Among 13 hospitalized kidney transplant recipients sapovirus was detected in four patients, while in the remaining nine, three were diagnosed with norovirus, one with cytomegalovirus, one with inflammatory bowel disease and in four patients no pathogen was identified. Even though statistically not significant, creatinine levels at admission tended to be higher in sapovirus patients (median: sapovirus: 3.3 mg/dl (1.3; 5.0), non-sapovirus: 2.5 mg/dl (1.1; 4.9), p = 0.710). Also, Tacrolimus levels showed the same trend (sapovirus: 13.6 ng/ml (12.9; 13.6), non-sapovirus: 7.1 ng/ml (2.6; 22.6), p = 0.279). On discharge creatinine levels improved equally in both groups (sapovirus: 1.7 mg/dl (1.4; 3.2), non-sapovirus: 2 mg/dl (1.0; 3.6), p = 0.825).

CONCLUSION

In high-risk patients, early symptomatic treatment remains crucial to protect the transplant`s function. In our cohort all patients recovered well. Larger cohorts and longer follow-up times are needed to detect the long-term consequences and a potential need for further research regarding specific treatment.

TRIAL REGISTRATION

The study has been registered on DRKS (trialsearch.who.int), Reg. Nr. DRKS00033311 (December 28th 2023).

How we treat diarrhea in pediatric transplant patients: a brief review

Diarrhea is a common problem faced by both hematopoietic and solid organ transplant recipients. The differential diagnosis is wide, ranging from infectious to non-infectious causes and from benign to emergent illness. Here we present two patients with diarrhea and discuss our approaches to the diagnostic evaluation and management of transplant recipients with diarrhea. We also include a review of the literature and discuss areas in need of further study.

How I approach diarrhea in hematological transplant patients: A practical tool

Diarrhea in hematopoietic stem-cell transplantation (HSCT) remains a multifactorial challenge that demands a nuanced diagnostic approach. The causes of infectious diarrhea in HSCT recipients are diverse and influenced by patient-specific risk factors, the post-transplant timeline, and local epidemiology. During the past decade, our understanding of diarrhea in HSCT has witnessed a transformative shift through the incorporation of gastrointestinal (GI) multiplex polymerase chain reaction (PCR) panels. However, the judicious application of these panels is imperative to avoid overtesting and prevent adverse outcomes. The challenge lies in distinguishing between the diverse causes of diarrhea, ascertaining the clinical significance of detected pathogens, and navigating the diagnostic uncertainty presented by several non-infectious conditions such as mucositis, intestinal dysbiosis, and acute graft-versus-host disease (aGvHD), all of which mimic infection. This review examines the landscape of infectious diarrhea in the HSCT population, encompassing both established (e.g., Cytomegalovirus, Clostridioides difficile, and norovirus) and emerging pathogens (e.g., sapoviruses, astroviruses). We propose a multifaceted diagnostic algorithm that combines clinical assessment, risk stratification, and tailored utilization of molecular platforms. While multiplex GI panels present invaluable opportunities for rapid and comprehensive pathogen detection, their judicious use is pivotal in preserving diagnostic stewardship. Customization of diagnostic algorithms tailored to local epidemiology ensures optimal patient care and resource utilization.

Infections after organ transplantation and immune response

Organ transplantation has provided another chance of survival for end-stage organ failure patients. Yet, transplant rejection is still a main challenging factor. Immunosuppressive drugs have been used to avoid rejection and suppress the immune response against allografts. Thus, immunosuppressants increase the risk of infection in immunocompromised organ transplant recipients. The infection risk reflects the relationship between the nature and severity of immunosuppression and infectious diseases. Furthermore, immunosuppressants show an immunological impact on the genetics of innate and adaptive immune responses. This effect usually reactivates the post-transplant infection in the donor and recipient tissues since T-cell activation has a substantial role in allograft rejection. Meanwhile, different infections have been found to activate the T-cells into CD₄⁺ helper T-cell subset and CD₈⁺ cytotoxic T-lymphocyte that affect the infection and the allograft. Therefore, the best management and preventive strategies of immunosuppression, antimicrobial prophylaxis, and intensive medical care are required for successful organ transplantation. This review addresses the activation of immune responses against different infections in immunocompromised individuals after organ transplantation.

Quantitative norovirus viral load is not affected by home storage of stool

In preparation of a clinical trial of norovirus treatment, there were concerns raised by FDA about risk of self‐storage of stool from patients infected with norovirus affecting quantitative assessments of norovirus RNA. Specifically, most home freezers are frost‐free and may expose the samples to multiple rounds of freeze‐thaw. Stool samples collected by the study team were stored at different lengths in a frost‐free freezer and at −80°C. Quantitative PCRs of norovirus were performed on all samples using the same assay. By all measures, there was no significant change in measured viral load with home storage.

Long-Term Infectious Complications of Kidney Transplantation

Infections remain a common complication of solid-organ transplantation. Most infections in the first month after transplant are typically health care-associated infections, whereas late infections, beyond 6-12 months, are community-acquired infections. Opportunistic infections most frequently present in the first 12 months post-transplant and can be modulated on prior exposures and use of prophylaxis. In this review, we summarize the current epidemiology of postkidney transplant infections with a focus on key viral (BK polyomavirus, cytomegalovirus, Epstein-Barr virus, and norovirus), bacterial (urinary tract infections and Clostridioides difficile colitis), and fungal infections. Current guidelines for safe living post-transplant are also summarized. Literature supporting prophylaxis and vaccination is also provided.

Viral Enteritis in Solid-Organ Transplantation

Solid organ transplant recipients are at increased risk for infections due to chronic immunosuppression. Diarrhea is a commonly encountered problem post transplantation, with infectious causes of diarrhea being a frequent complication. Viral infections/enteritides in solid organ transplant recipients often result from frequently encountered pathogens in this population such as cytomegalovirus, adenovirus, and norovirus. However, several emerging viral pathogens are increasingly being recognized as more sensitive diagnostic techniques become available. Treatment is often limited to supportive care and reduction in immunosuppression, though antiviral therapies mayplay a role in the treatment in certain diseases. Viral enteritis is an important entity that contributes to morbidity and mortality in transplant recipients.

Clinical characteristics, risk factors and outcome of severe Norovirus infection in kidney transplant patients: a case-control study

Background

Human Norovirus (HuNoV) has recently been identified as a major cause of diarrhea among kidney transplant recipients (KTR). Data regarding risk factors associated with the occurrence of HuNoV infection, and its long-term impact on kidney function are lacking.

Methods

We conducted a retrospective case-control study including all KTR with a diagnosis of HuNoV diarrhea. Each case was matched to a single control according to age and date of transplantation, randomly selected among our KTR cohort and who did not develop HuNoV infection. Risk factors associated with HuNoV infection were identified using conditional logistic regression, and survival was estimated using Kaplan-Meier estimator.

Results

From January 2012 to April 2018, 72 cases of NoV diarrhea were identified among 985 new KT, leading to a prevalence of HuNoV infection of 7.3%. Median time between kidney transplantation and diagnosis was 46.5 months (Inter Quartile Range [IQR]:17.8–81.5), and the median duration of symptoms 40 days (IQR: 15–66.2). Following diagnosis, 93% of the cases had a reduction of immunosuppression. During follow-up, de novo Donor Specific Antibody (DSA) were observed in 8 (9%) cases but none of the controls (p = 0.01). Acute rejection episodes were significantly more frequent among cases (13.8% versus 4.2% in controls; p = 0,03), but there was no difference in serum creatinine level at last follow-up between the two groups (p = 0.08). Pre-transplant diabetes and lymphopenia below 1000/mm³ were identified as risks factors for HuNoV infection in multivariate analysis.

Conclusion

HuNoV infection is a late-onset and prolonged infection among KTR. The current management, based on the reduction of immunosuppressive treatment, is responsible for the appearance of de novo DSA and an increase in acute rejection episodes.

Mutations in the VP2 gene of rotavirus associated with benzimidazole sensitivity

Rotavirus species A (RVA) is the etiological agent of acute gastroenteritis in young individuals of various animal species, including humans. Vaccination has helped to reduce the impact of these viruses on humans and some species of domestic mammals, but they do not confer complete immunity, so antirotavirus agents are another important control option. In this study, millimolar concentrations of benzimidazole inhibited the replication of the Rhesus rotavirus (RRV) strain of RVA. Two mutants partially resistant to the inhibitory effect of benzimidazole were independently selected, and their genomes and those of their parental strains were fully sequenced. Most (7/11) mutations occurred in the gene that encodes the VP2 protein, and similarly most of the missense mutations (5/9), including the only one shared by the two mutants (G2,414 → R[G/A], D800 N), occurred in the VP2 gene. Our results identify the VP2 gene as the primary target affected by benzimidazole.

Recurring Norovirus & Sapovirus Infection in a Renal Transplant Patient

Noroviruses and sapoviruses are common causes of gastroenteritis and infectious diarrhea. Although these viruses are typically of short duration in healthy individuals, immunocompromised organ transplant recipients can develop chronic, relapsing symptoms with grave outcomes. We discuss a unique case of chronic norovirus infection with subsequent sapovirus infection in a kidney transplant recipient. Relief of norovirus symptoms occurred after the reduction of immunosuppression and treatment with nitazoxanide. Subsequently, a superimposed sapovirus infection developed. Patient developed renal transplant rejection due to reduction of immunosuppression. Findings from this case study suggest that norovirus and sapovirus are associated with chronic, relapsing symptoms and significant morbidity in immunocompromised renal transplant patients and that reduction of immunosuppression in order to overcome infection risks allograft rejection. Early detection and management are essential to reduce morbidity associated with these viruses among immunocompromised transplant recipients.

Molecular Diagnostic Advances in Transplant Infectious Diseases

PURPOSE OF REVIEW

The infectious complications of transplantation can have devastating consequences for patients. Early and accurate diagnosis is essential to good outcomes. This review describes recent advances in pathogen-directed diagnostic testing and discusses the role of new methods for transplant infectious diseases.

RECENT FINDINGS

Several molecular assays have been introduced into clinical practice in recent years. When the results of rapid testing are linked to patient-specific interventions, improved outcomes can be realized. Syndromic testing along with metagenomic next-generation sequencing (mNGS) represents novel approaches to infection diagnosis. However, the optimal use of these tests for transplant patients along with an overall assessment of cost-effectiveness demands further study. Molecular diagnostics are revolutionizing transplant care. Clinicians need to be aware of the current diagnostic landscape and have a working knowledge of the nuances related to test performance, result interpretation, and cost.

Diagnosis and management of diarrhea in solid-organ transplant recipients: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of diarrhea in the pre- and post-transplant period. Diarrhea in an organ transplant recipient may result in significant morbidity including dehydration, increased toxicity of medications, and rejection. Transplant recipients are affected by a wide range of etiologies of diarrhea with the most common causes being Clostridioides (formerly Clostridium) difficile infection, cytomegalovirus, and norovirus. Other bacterial, viral, and parasitic causes can result in diarrhea but are far less common. Further, noninfectious causes including medication toxicity, inflammatory bowel disease, post-transplant lymphoproliferative disease, and malignancy can also result in diarrhea in the transplant population. Management of diarrhea in this population is directed at the cause of the diarrhea, instituting therapy where appropriate and maintaining proper hydration. Identification of the cause to the diarrhea needs to be timely and focused.

Suppression of pyrimidine biosynthesis by targeting DHODH enzyme robustly inhibits rotavirus replication

Rotavirus infection remains a great health burden worldwide especially in some developing countries. It causes severe dehydrating diarrhea in infants, young children, as well as immunocompromised and organ transplanted patients. Viral replication heavily relies on the host to supply nucleosides. Thus, host enzymes involved in nucleotide biosynthesis represent potential targets for antiviral development. Dihydroorotate dehydrogenase (DHODH) is the rate-limiting enzyme in the de novo biosynthesis pathway of pyrimidines. In this study, we demonstrated that two specific DHODH enzyme inhibitors, brequinar (BQR) and leflunomide (LFM) robustly inhibited rotavirus replication in conventional human intestinal Caco2 cell line as well as in human primary intestinal organoids. The antiviral effect is conserved in both laboratory strain SA11 and rotavirus strain 2011K isolated from clinical sample. Mechanistic study indicated that BQR and LFM exerted their anti-rotavirus effect through targeting DHODH to deplete pyrimidine nucleotide pool. Therefore, targeting pyrimidine biosynthesis represents a potential approach for developing antiviral strategies against rotavirus.

Baseline graft status is a critical predictor of kidney graft failure after diarrhoea

Background

Diarrhoea is one of the most frequent complications after kidney transplantation (KT). Non-infectious diarrhoea has been associated with reduced graft survival in kidney transplant recipients. However, the risk factors for renal allograft loss following diarrhoea remain largely unknown.

Methods

Between January 2010 and August 2011, 195 consecutive KT recipients who underwent standardized microbiological workups for diarrhoea at a single centre were enrolled in this retrospective study.

Results

An enteric pathogen was readily identified in 91 patients (47%), while extensive microbiological investigations failed to find any pathogen in the other 104. Norovirus was the leading cause of diarrhoea in these patients, accounting for 30% of the total diarrhoea episodes. The baseline characteristics were remarkably similar between non-infectious and infectious diarrhoea patients, with the exception that the non-infectious group had significantly lower graft function before diarrhoea (P = 0.039). Infectious diarrhoea was associated with a longer duration of symptoms (P = 0.001) and higher rates of acute kidney injury (P = 0.029) and hospitalization (P < 0.001) than non-infectious diarrhoea. However, the non-infectious group had lower death-censored graft survival than the infectious group (Gehan–Wilcoxon test, P = 0.038). Multivariate analysis retained three independent predictors of graft failure after diarrhoea: diarrhoea occurring ≥5 years after KT [hazard ratio (HR) 4.82; P < 0.001], re-transplantation (HR 2.38; P = 0.001) and baseline estimated glomerular filtration rate <30 mL/min/1.73 m2 (HR 11.02; P < 0.001).

Conclusion

Our study shows that pre-existing conditions (re-transplantation, chronic graft dysfunction and late occurrence) determine the primary functional long-term consequences of post-transplant diarrhoea.

The evaluation of critically ill transplant patients with infectious diarrhea

PURPOSE OF REVIEW

The review summarizes the epidemiology, risk factors, clinical presentation, diagnosis and management of the most important etiologic agents of infectious diarrhea in critically ill transplant recipients.

RECENT FINDINGS

Diarrhea, frequently caused by infectious pathogens, can cause significant morbidity and mortality in transplant recipients. Diarrhea can lead to severe dehydration, acute renal failure, medication toxicity, rejection, graft-versus-host disease and impairs patients' quality of life. Opportunistic infectious pathogens can pose significant diagnostic and therapeutic challenges in immunocompromised hosts.

SUMMARY

In transplant recipients, it is vital to differentiate infectious from noninfectious diarrhea to adequately manage their therapeutic approach. Supportive measures and reduction in immunosuppression are essential for the treatment management.

PI3K-Akt-mTOR axis sustains rotavirus infection via the 4E-BP1 mediated autophagy pathway and represents an antiviral target

Rotavirus infection is a major cause of severe dehydrating diarrhea in infants younger than 5 y old and in particular cases of immunocompromised patients irrespective to the age of the patients. Although vaccines have been developed, antiviral therapy is an important complement that cannot be substituted. Because of the lack of specific approved treatment, it is urgent to facilitate the cascade of further understanding of the infection biology, identification of druggable targets and the final development of effective antiviral therapies. PI3K-Akt-mTOR signaling pathway plays a vital role in regulating the infection course of many viruses. In this study, we have dissected the effects of PI3K-Akt-mTOR signaling pathway on rotavirus infection using both conventional cell culture models and a 3D model of human primary intestinal organoids. We found that PI3K-Akt-mTOR signaling is essential in sustaining rotavirus infection. Thus, blocking the key elements of this pathway, including PI3K, mTOR and 4E-BP1, has resulted in potent anti-rotavirus activity. Importantly, a clinically used mTOR inhibitor, rapamycin, potently inhibited both experimental and patient-derived rotavirus strains. This effect involves 4E-BP1 mediated induction of autophagy, which in turn exerts anti-rotavirus effects. These results revealed new insights on rotavirus-host interactions and provided new avenues for antiviral drug development.

Intestinal Batf3-dependent dendritic cells are required for optimal antiviral T-cell responses in adult and neonatal mice

Although we know a great deal about which types of dendritic cells (DCs) promote T-cell priming in the periphery, less is known about which DC subset(s) provoke antiviral responses within the gut. Here we report that conventional Zbtb46-dependent DCs were critically required for antiviral CD8⁺ T-cell responses against rotavirus (RV), the major cause of childhood gastroenteritis worldwide. Furthermore, we found that in adult mice, Batf3-dependent DCs were required for generating optimal RV-specific CD8⁺ T-cell responses. However, in contrast to mice that lack Zbtb46-dependent DCs, a significant amount of interferon gamma-producing RV-specific CD8⁺ T cells were still detected in the small intestine of RV-infected adult Batf3^-/- mice, suggesting the existence of compensatory cross-presentation mechanisms in the absence of Batf3-dependent DCs. In contrast to adult mice, we found that Batf3-dependent DCs were absolutely required for generating RV-specific CD8⁺ T-cell responses in neonates. Loss of Batf3-dependent DCs also resulted in a skewed polyclonal CD4⁺ T-cell response in both adult and neonatal mice upon RV infection, although local and systemic RV-specific immunoglobulin A production kinetics and titers were unimpaired. Our results provide insights that inform early-life vaccination strategies against RV infection.

Pattern and Predictors of Hospital Readmission During the First Year After Lung Transplantation

Hospital readmission after lung transplantation negatively affects quality of life and resource utilization. A secondary analysis of data collected prospectively was conducted to identify the pattern of (incidence, count, cumulative duration), reasons for and predictors of readmission for 201 lung transplant recipients (LTRs) assessed at 2, 6, and 12 mo after discharge. The majority of LTRs (83.6%) were readmitted, and 64.2% had multiple readmissions. The median cumulative readmission duration was 19 days. The main reasons for readmission were other than infection or rejection (55.5%), infection only (25.4%), rejection only (9.9%), and infection and rejection (0.7%). LTRs who required reintubation (odds ratio [OR] 1.92; p = 0.008) or were discharged to care facilities (OR 2.78; p = 0.008) were at higher risk for readmission, with a 95.7% cumulative incidence of readmission at 12 mo. Thirty-day readmission (40.8%) was not significantly predicted by baseline characteristics. Predictors of higher readmission count were lower capacity to engage in self-care (incidence rate ratio [IRR] 0.99; p = 0.03) and discharge to care facilities (IRR 1.45; p = 0.01). Predictors of longer cumulative readmission duration were older age (arithmetic mean ratio [AMR] 1.02; p = 0.009), return to the intensive care unit (AMR 2.00; p = 0.01) and lower capacity to engage in self-care (AMR 0.99; p = 0.03). Identifying LTRs at risk may assist in optimizing predischarge care, discharge planning and long-term follow-up.

Chronic Norovirus Infections in Cardiac Transplant Patients

Norovirus is a common self-limiting gastrointestinal infection, but in transplant recipients, symptoms can last for months and result in serious health complications. As there is currently no established treatment for chronic norovirus infection in transplant patients, management has been directed at symptom control, trial of various antivirals, and ultimately reductions in immunosuppression. We present 3 cases of chronic norovirus infection in cardiac transplant patients to illustrate various approaches to diagnosis, the prolonged nature of disease symptoms, and treatment options. When managing a transplant recipient with chronic diarrhea, considering a broad differential as well as maintaining a high suspicion for infectious etiologies is key. A stepwise approach to management includes termination of diarrhea-causing medications, trials of nitazoxanide and immunoglobulin, and reductions in immunosuppressive therapies. Although brief discontinuation of immunosuppression is often required to achieve symptom, graft rejection is often a complication.

Viral gastrointestinal infections and norovirus genotypes in a paediatric UK hospital, 2014-2015

BACKGROUND

Diarrhoea in children is a common disease; understanding the incidence of causative viruses can aid infection control and vaccine development.

OBJECTIVES

Describe the incidence and characteristics of gastroenteric viruses including norovirus genotypes in a paediatric hospital cohort.

STUDY DESIGN

Norovirus, adenovirus, sapovirus, astrovirus, rotavirus qPCR and norovirus genotyping results for all stool specimens (n=4786; 1393 patients) at a UK paediatric tertiary referral hospital June 2014-July 2015.

RESULTS AND DISCUSSION

24% (329/1393) of patients were positive for a GI virus; the majority were positive for norovirus (44%, 144/329) or adenovirus (44%, 146/329). The overall incidence of rotavirus (2%) is reduced compared to pre-vaccination studies; however the incidence of other GI viruses has not increased. Norovirus infections had a significantly higher virus burden compared to other GI viruses (P ≤0.03); sapovirus infections had the lowest viral burden. The number of norovirus cases per month did not follow the typical winter seasonal trend of nationally reported outbreaks. The number of cases per month correlates with the number of hospital admissions (R=0.703, P=0.011); the number of admissions accounts for 50% of the variability in number of cases per month. The breadth of genotypes seen (48% non-GII.4), suggests a community source for many norovirus infections and has implications for vaccine development. All GI viruses caused chronic infections, with the majority (50-100%) in immunocompromised patients. Incidence or duration of infection in chronic norovirus infections did not differ between genotypes, suggesting host-mediated susceptibility.

Mycophenolic acid potently inhibits rotavirus infection with a high barrier to resistance development

Rotavirus infection has emerged as an important cause of complications in organ transplantation recipients. Immunosuppressants used to prevent alloreactivity can also interfere with virus infection, but the direct effects of the specific type of immunosuppressants on rotavirus infection are still unclear. Here we profiled the effects of different immunosuppressants on rotavirus using a 2D culture model of Caco2 human intestinal cell line and a 3D model of human primary intestinal organoids inoculated with laboratory and patient-derived rotavirus strains. We found that the responsiveness of rotavirus to Cyclosporine A treatment was moderate and strictly regulated in an opposite direction by its cellular targets cyclophilin A and B. Treatment with mycophenolic acid (MPA) resulted in a 99% inhibition of viral RNA production at the clinically relevant concentration (10 μg/ml) in Caco2 cells. This effect was further confirmed in organoids. Importantly, continuous treatment with MPA for 30 passages did not attenuate its antiviral potency, indicating a high barrier to drug resistance development. Mechanistically, the antiviral effects of MPA act via inhibiting the IMPDH enzyme and resulting in guanosine nucleotide depletion. Thus for transplantation patients at risk for rotavirus infection, the choice of MPA as an immunosuppressive agent appears rational.

Modeling rotavirus infection and antiviral therapy using primary intestinal organoids

Despite the introduction of oral vaccines, rotavirus still kills over 450,000 children under five years of age annually. The absence of specific treatment prompts research aiming at further understanding of pathogenesis and the development of effective antiviral therapy, which in turn requires advanced experimental models. Given the intrinsic limitations of the classical rotavirus models using immortalized cell lines infected with laboratory-adapted strains in two dimensional cultures, our study aimed to model infection and antiviral therapy of both experimental and patient-derived rotavirus strains using three dimensional cultures of primary intestinal organoids. Intestinal epithelial organoids were successfully cultured from mouse or human gut tissues. These organoids recapitulate essential features of the in vivo tissue architecture, and are susceptible to rotavirus. Human organoids are more permissive to rotavirus infection, displaying an over 10,000-fold increase in genomic RNA following 24h of viral replication. Furthermore, infected organoids are capable of producing infectious rotavirus particles. Treatment of interferon-alpha or ribavirin inhibited viral replication in organoids of both species. Importantly, human organoids efficiently support the infection of patient-derived rotavirus strains and can be potentially harnessed for personalized evaluation of the efficacy of antiviral medications. Therefore, organoids provide a robust model system for studying rotavirus-host interactions and assessing antiviral medications.

Primary Care of the Solid Organ Transplant Recipient

Solid organ transplantation (SOT) is one of the major advances in medicine. Care of the SOT recipient is complex and continued partnership with the transplant specialist is essential to manage and treat complications and maintain health. The increased longevity of SOT recipients will lead to their being an evolving part of primary care practice, with ever more opportunities for care, education, and research of this rewarding patient population. This review discusses the overall primary care management of adult SOT recipients.

Diarrhea in solid organ transplant recipients

PURPOSE OF REVIEW

Diarrhea is a common complaint in the solid organ transplant recipient. Unlike the immune-competent patient, diarrhea in an organ transplant recipient may result in dehydration, increased toxicity of medications, and rejection. There is a wide range of causes for diarrhea in transplant recipients, but the most common causes are Clostridium difficile infection, cytomegalovirus, and norovirus. This review will focus on new epidemiology data as to the cause of diarrhea in the transplant population.

RECENT FINDINGS

Recent data have identified C. difficile, cytomegalovirus, and norovirus as important causes of diarrhea in this population, and management should be focused on these causes. Newer diagnostic platforms (such as PCR) are being evaluated, which may help in identification of the cause of diarrhea.

SUMMARY

New epidemiologic data and new testing techniques offer an opportunity for research into better testing strategies for transplant patients with diarrhea. These newer testing strategies may offer better insight into the cause of diarrhea and more appropriate treatment for this illness.

Rotavirus in organ transplantation: drug-virus-host interactions

Although rotavirus is usually recognized as the most common etiology of diarrhea in young children, it can in fact cause severe diseases in organ transplantation recipients irrespective of pediatric or adult patients. This comprehensive literature analysis revealed 200 cases of rotavirus infection with 8 related deaths in the setting of organ transplantation been recorded. Based on published cohort studies, an average incidence of 3% (187 infections out of 6176 organ recipients) was estimated. Rotavirus infection often causes severe gastroenteritis complications and occasionally contributes to acute cellular rejection in these patients. Immunosuppressive agents, universally used after organ transplantation to prevent organ rejection, conceivably play an important role in such a severe pathogenesis. Interestingly, rotavirus can in turn affect the absorption and metabolism of particular immunosuppressive medications via several distinct mechanisms. Even though rotaviral enteritis is self-limiting in general, infected transplantation patients are usually treated with intensive care, rehydration and replacement of nutrition, as well as applying preventive strategies. This article aims to properly assess the clinical impact of rotavirus infection in the setting of organ transplantation and to disseminate the interactions among the virus, host and immunosuppressive medications.