Rotavirus infection of infant and young adult nonobese diabetic mice involves extraintestinal spread and delays diabetes onset

Beyond faecal microbiota transplantation, the non-negligible role of faecal virome or bacteriophage transplantation

Intestinal microbiota, which contains bacteria, archaea, fungi, protists, and viruses including bacteriophages, is symbiotic and evolves together with humans. The balanced intestinal microbiota plays indispensable roles in maintaining and regulating host metabolism and health. Dysbiosis has been associated with not only intestinal diseases but other diseases such as neurology disorders and cancers. Faecal microbiota transplantation (FMT) or faecal virome or bacteriophage transplantation (FVT or FBT), transfers faecal bacteria or viruses, with a focus on bacteriophage, from one healthy individual to another individual (normally unhealthy condition), and aims to restore the balanced gut microbiota and assist in subduing diseases. In this review, we summarized the applications of FMT and FVT in clinical settings, discussed the advantages and challenges of FMT and FVT currently and proposed several considerations prospectively. We further provided our understanding of why FMT and FVT have their limitations and raised the possible future development strategy of FMT and FVT.

Lactobacillus delbrueckii CRL 581 Differentially Modulates TLR3-Triggered Antiviral Innate Immune Response in Intestinal Epithelial Cells and Macrophages

Lactobacillus delbrueckii subsp. lactis CRL 581 beneficially modulates the intestinal antiviral innate immune response triggered by the Toll-like receptor 3 (TLR3) agonist poly(I:C) in vivo. This study aimed to characterize further the immunomodulatory properties of the technologically relevant starter culture L. delbrueckii subsp. lactis CRL 581 by evaluating its interaction with intestinal epithelial cells and macrophages in the context of innate immune responses triggered by TLR3. Our results showed that the CRL 581 strain was able to adhere to porcine intestinal epithelial (PIE) cells and mucins. The CRL 581 strain also augmented the expression of antiviral factors (IFN-α, IFN-β, Mx1, OAS1, and OAS2) and reduced inflammatory cytokines in PIE cells triggered by TLR3 stimulation. In addition, the influence of L. delbrueckii subsp. lactis CRL 581 on the response of murine RAW macrophages to the activation of TLR3 was evaluated. The CRL 581 strain was capable of enhancing the expression of IFN-α, IFN-β, IFN-γ, Mx1, OAS1, TNF-α, and IL-1β. Of note, the CRL 581 strain also augmented the expression of IL-10 in macrophages. The results of this study show that the high proteolytic strain L. delbrueckii spp. lactis CRL 581 was able to beneficially modulate the intestinal innate antiviral immune response by regulating the response of both epithelial cells and macrophages relative to TLR3 activation.

Enteric viruses evoke broad host immune responses resembling those elicited by the bacterial microbiome

The contributions of the viral component of the microbiome-the virome-to the development of innate and adaptive immunity are largely unknown. Here, we systematically defined the host response in mice to a panel of eukaryotic enteric viruses representing six different families. Infections with most of these viruses were asymptomatic in the mice, the magnitude and duration of which was dependent on the microbiota. Flow cytometric and transcriptional profiling of mice mono-associated with these viruses unveiled general adaptations by the host, such as lymphocyte differentiation and IL-22 signatures in the intestine, as well as numerous viral-strain-specific responses that persisted. Comparison with a dataset derived from analogous bacterial mono-association in mice identified bacterial species that evoke an immune response comparable with the viruses we examined. These results expand an understanding of the immune space occupied by the enteric virome and underscore the importance of viral exposure events.

Inflammasomes and Type 1 Diabetes

Microbiota have been identified as an important modulator of susceptibility in the development of Type 1 diabetes in both animal models and humans. Collectively these studies highlight the association of the microbiota composition with genetic risk, islet autoantibody development and modulation of the immune responses. However, the signaling pathways involved in mediating these changes are less well investigated, particularly in humans. Importantly, understanding the activation of signaling pathways in response to microbial stimulation is vital to enable further development of immunotherapeutics, which may enable enhanced tolerance to the microbiota or prevent the initiation of the autoimmune process. One such signaling pathway that has been poorly studied in the context of Type 1 diabetes is the role of the inflammasomes, which are multiprotein complexes that can initiate immune responses following detection of their microbial ligands. In this review, we discuss the roles of the inflammasomes in modulating Type 1 diabetes susceptibility, from genetic associations to the priming and activation of the inflammasomes. In addition, we also summarize the available inhibitors for therapeutically targeting the inflammasomes, which may be of future use in Type 1 diabetes.

Rotavirus-related systemic diseases: clinical manifestation, evidence and pathogenesis

Rotaviruses, double-stranded, non-enveloped RNA viruses, are a global health concern, associated with acute gastroenteritis and secretory-driven watery diarrhoea, especially in infants and young children. Conventionally, rotavirus is primarily viewed as a pathogen for intestinal enterocytes. This notion is challenged, however, by data from patients and animal models documenting extra-intestinal clinical manifestations and viral replication following rotavirus infection. In addition to acute gastroenteritis, rotavirus infection has been linked to various neurological disorders, hepatitis and cholestasis, type 1 diabetes, respiratory illness, myocarditis, renal failure and thrombocytopenia. Concomitantly, molecular studies have provided insight into potential mechanisms by which rotavirus can enter and replicate in non-enterocyte cell types and evade host immune responses. Nevertheless, it is fair to say that the extra-intestinal aspect of the rotavirus infectious process is largely being overlooked by biomedical professionals, and there are gaps in the understanding of mechanisms of pathogenesis. Thus with the aim of increasing public and professional awareness we here provide a description of our current understanding of rotavirus-related extra-intestinal clinical manifestations and associated molecular pathogenesis. Further understanding of the processes involved should prove exceedingly useful for future diagnosis, treatment and prevention of rotavirus-associated disease.

Rotavirus and Type 1 Diabetes-Is There a Connection? A Synthesis of the Evidence

Although the etiology of type 1 diabetes (T1D) is not well understood, it is believed to comprise both genetic and environmental factors. Viruses are the most well studied environmental trigger, and there is a small but growing body of research on the potential influence of rotavirus on T1D. Rotavirus infections were initially identified as possible triggers of T1D given similarities between viral peptide sequences and T1D autoantigen peptide sequences. Furthermore, rotavirus infection has been shown to modify T1D risk in T1D-prone mice. However, research into associations of rotavirus infections with T1D development in humans have yielded mixed findings and suggested interactions with age and diet. As global availability of rotavirus vaccines increases, recent studies have assessed whether rotavirus vaccination modifies T1D development, finding null or protective associations. Overall, evidence to date suggests a possible triggering relationship between some wild-type rotavirus infections and T1D, but the potential effect of rotavirus vaccination remains unclear.

Association Between Rotavirus Vaccination and Type 1 Diabetes in Children

IMPORTANCE

Because rotavirus infection is a hypothesized risk factor for type 1 diabetes, live attenuated rotavirus vaccination could increase or decrease the risk of type 1 diabetes in children.

OBJECTIVE

To examine whether there is an association between rotavirus vaccination and incidence of type 1 diabetes in children aged 8 months to 11 years.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective cohort study of 386 937 children born between January 1, 2006, and December 31, 2014, was conducted in 7 US health care organizations of the Vaccine Safety Datalink. Eligible children were followed up until a diagnosis of type 1 diabetes, disenrollment, or December 31, 2017.

EXPOSURES

Rotavirus vaccination for children aged 2 to 8 months. Three exposure groups were created. The first group included children who received all recommended doses of rotavirus vaccine by 8 months of age (fully exposed to rotavirus vaccination). The second group had received some, but not all, recommended rotavirus vaccines (partially exposed to rotavirus vaccination). The third group did not receive any doses of rotavirus vaccines (unexposed to rotavirus vaccination).

MAIN OUTCOMES AND MEASURES

Incidence of type 1 diabetes among children aged 8 months to 11 years. Type 1 diabetes was identified by International Classification of Diseases codes: 250.x1, 250.x3, or E10.xx in the outpatient setting. Cox proportional hazards regression models were used to analyze time to type 1 diabetes incidence from 8 months to 11 years. Hazard ratios and 95% CIs were calculated. Models were adjusted for sex, race/ethnicity, birth year, mother's age, birth weight, gestational age, number of well-child visits, and Vaccine Safety Datalink site.

RESULTS

In a cohort of 386 937 children (51.1% boys and 41.9% non-Hispanic white), 360 169 (93.1%) were fully exposed to rotavirus vaccination, 15 765 (4.1%) were partially exposed to rotavirus vaccination, and 11 003 (2.8%) were unexposed to rotavirus vaccination. Children were followed up a median of 5.4 years (interquartile range, 3.8-7.8 years). The total person-time follow-up in the cohort was 2 253 879 years. There were 464 cases of type 1 diabetes in the cohort, with an incidence rate of 20.6 cases per 100 000 person-years. Compared with children unexposed to rotavirus vaccination, the adjusted hazard ratio was 1.03 (95% CI, 0.62-1.72) for children fully exposed to rotavirus vaccination and 1.50 (95% CI, 0.81-2.77) for children partially exposed to rotavirus vaccination.

CONCLUSIONS AND RELEVANCE

The findings of this study suggest that rotavirus vaccination does not appear to be associated with type 1 diabetes in children.

Norovirus Changes Susceptibility to Type 1 Diabetes by Altering Intestinal Microbiota and Immune Cell Functions

Environmental factors contribute to Type 1 diabetes (T1D) susceptibility. The gut microbiome, which includes bacteria, viruses, and fungi, contributes to this environmental influence, and can induce immunological changes. The gut viral component of the microbiome, related to T1D has mostly focused on coxsackieviruses and rotavirus. The role of norovirus, another common enteric virus, in susceptibility to T1D was hitherto unknown. Norovirus is highly infectious and encountered by many children. We studied the mouse norovirus 4 (MNV4), related to human noroviruses, in the Non-obese diabetic (NOD) mouse model, to determine its role in influencing susceptibility to T1D. We infected MNV-free NOD mice with MNV4 by exposing the mice to MNV4-positive bedding from an endemically-infected mouse colony to mimic a natural infection. Control MNV-free NOD mice were exposed to MNV-free bedding from the same colony. Interestingly, MNV4 infection protected NOD mice from the development of T1D and was associated with an expansion of Tregs and reduced proinflammatory T cells. We also found MNV4 significantly modified the gut commensal bacteria composition, promoting increased α-diversity and Firmicutes/Bacteroidetes ratio. To elucidate whether T1D protection was directly related to MNV4, or indirectly through modulating gut microbiota, we colonized germ-free (GF) NOD mice with the MNV4-containing or non-MNV4-containing viral filtrate, isolated from filtered fecal material. We found that MNV4 induced significant changes in mucosal immunity, including altered Tuft cell markers, cytokine secretion, antiviral immune signaling markers, and the concentration of mucosal antibodies. Systemically, MNV4-infection altered the immune cells including B cell subsets, macrophages and T cells, and especially induced an increase in Treg number and function. Furthermore, in vitro primary exposure of the norovirus filtrate to naïve splenocytes identified significant increases in the proportion of activated and CTLA4-expressing Tregs. Our data provide novel knowledge that norovirus can protect NOD mice from T1D development by inducing the expansion of Tregs and reducing inflammatory T cells. Our study also highlights the importance of distinguishing the mucosal immunity mediated by bacteria from that by enteric viruses.

The Intestinal Virome and Immunity

The composition of the human microbiome is considered a major source of interindividual variation in immunity and, by extension, susceptibility to diseases. Intestinal bacteria have been the major focus of research. However, diverse communities of viruses that infect microbes and the animal host cohabitate the gastrointestinal tract and collectively constitute the gut virome. Although viruses are typically investigated as pathogens, recent studies highlight a relationship between the host and animal viruses in the gut that is more akin to host-microbiome interactions and includes both beneficial and detrimental outcomes for the host. These viruses are likely sources of immune variation, both locally and extraintestinally. In this review, we describe the components of the gut virome, in particular mammalian viruses, and their ability to modulate host responses during homeostasis and disease.

Rotavirus Infection Enhances Levels of Autoantibodies Against Islet Cell Antigens GAD65 and IA-2 in Children with Type 1 Diabetes

BACKGROUND

Some studies implicate rotavirus infection as a trigger for the development of type 1 diabetes mellitus (T1DM) in children, however findings are controversial.

OBJECTIVES

We investigated the link between rotavirus infection and autoantibodies against islet antigens and T1DM in children.

METHODS

Serum samples from 80 new-onset diabetic and 80 nondiabetic children were screened for anti-rotavirus IgG, anti-GAD65 and anti-IA-2 autoantibodies using ELISA kits.

RESULTS

Positivity percentages of anti-rotavirus IgG detection in diabetic and nondiabetic children were 51.3% and 35.0%, respectively (p = 0.03). The mean anti-GAD65 and anti-IA-2 antibody titers in anti-rotavirus IgG positive samples were statistically higher than that the anti-rotavirus IgG negative samples. A positive correlation was found between anti-rotavirus IgG and anti-GAD65 antibody levels (p = 0.004; r = 0.22).

CONCLUSIONS

Our findings support the hypothesis that rotovirus infection may induce T1DM in children.

Rotavirus infection

Rotavirus infections are a leading cause of severe, dehydrating gastroenteritis in children <5 years of age. Despite the global introduction of vaccinations for rotavirus over a decade ago, rotavirus infections still result in >200,000 deaths annually, mostly in low-income countries. Rotavirus primarily infects enterocytes and induces diarrhoea through the destruction of absorptive enterocytes (leading to malabsorption), intestinal secretion stimulated by rotavirus non-structural protein 4 and activation of the enteric nervous system. In addition, rotavirus infections can lead to antigenaemia (which is associated with more severe manifestations of acute gastroenteritis) and viraemia, and rotavirus can replicate in systemic sites, although this is limited. Reinfections with rotavirus are common throughout life, although the disease severity is reduced with repeat infections. The immune correlates of protection against rotavirus reinfection and recovery from infection are poorly understood, although rotavirus-specific immunoglobulin A has a role in both aspects. The management of rotavirus infection focuses on the prevention and treatment of dehydration, although the use of antiviral and anti-emetic drugs can be indicated in some cases.

Rotavirus acceleration of type 1 diabetes in non-obese diabetic mice depends on type I interferon signalling

Rotavirus infection is associated with childhood progression to type 1 diabetes. Infection by monkey rotavirus RRV accelerates diabetes onset in non-obese diabetic (NOD) mice, which relates to regional lymph node infection and a T helper 1-specific immune response. When stimulated ex vivo with RRV, plasmacytoid dendritic cells (pDCs) from naïve NOD mice secrete type I interferon, which induces the activation of bystander lymphocytes, including islet-autoreactive T cells. This is our proposed mechanism for diabetes acceleration by rotaviruses. Here we demonstrate bystander lymphocyte activation in RRV-infected NOD mice, which showed pDC activation and strong upregulation of interferon-dependent gene expression, particularly within lymph nodes. The requirement for type I interferon signalling was analysed using NOD mice lacking a functional type I interferon receptor (NOD.IFNAR1(-/-) mice). Compared with NOD mice, NOD.IFNAR1(-/-) mice showed 8-fold higher RRV titers in lymph nodes and 3-fold higher titers of total RRV antibody in serum. However, RRV-infected NOD.IFNAR1(-/-) mice exhibited delayed pDC and lymphocyte activation, no T helper 1 bias in RRV-specific antibodies and unaltered diabetes onset when compared with uninfected controls. Thus, the type I interferon signalling induced by RRV infection is required for bystander lymphocyte activation and accelerated type 1 diabetes onset in genetically susceptible mice.

Systemic features of rotavirus infection

A growing body of evidence warrants a revision of the received/conventional wisdom of rotavirus infection as synonymous with acute gastroenteritis. Rotavirus vaccines have boosted our interest and knowledge of this virus, but also importantly, they may have changed the landscape of the disease. Extraintestinal spread of rotavirus is well documented, and the clinical spectrum of the disease is widening. Furthermore, the positive impact of current rotavirus vaccines in reducing seizure hospitalization rates should prompt a reassessment of the actual burden of extraintestinal manifestations of rotavirus diseases. This article discusses current knowledge of the systemic extraintestinal manifestations of rotavirus infection and their underlying mechanisms, and aims to pave the way for future clinical, public health and research questions.

Innate immune responses to rotavirus infection in macrophages depend on MAVS but involve neither the NLRP3 inflammasome nor JNK and p38 signaling pathways

Rotavirus infection is a major cause of life-threatening infantile gastroenteritis. The innate immune system provides an immediate mechanism of suppressing viral replication and is necessary for an effective adaptive immune response. Innate immunity involves host recognition of viral infection and establishment of a powerful antiviral state through the expression of pro-inflammatory cytokines such as type-1 interferon (IFN). Macrophages, the front-line cells of innate immunity, produce IFN and other cytokines in response to viral infection. However, the role of macrophages during rotavirus infection is not well defined. We demonstrate here that RRV rotavirus triggers the production of proinflammatory cytokines from mouse bone marrow-derived macrophages. IFN and antiviral cytokine production was abolished in rotavirus-infected MAVS (-/-) macrophages. This indicates that rotavirus triggers innate immunity in macrophages through RIG-I and/or MDA5 viral recognition, and MAVS signaling is essential for cytokine responses in macrophages. Rotavirus induced IFN expression in both wild type and MDA5 (-/-) macrophages, showing that MDA5 is not essential for IFN secretion following infection, and RIG-I and MDA5 may act redundantly in promoting rotavirus recognition. Interestingly, rotavirus neither stimulated mitogen-activated protein kinases p38 and JNK nor activated the NLRP3 inflammasome, demonstrating that these components might not be involved in innate responses to rotavirus infection in macrophages. Our results indicate that rotavirus elicits intracellular signaling in macrophages, resulting in the induction of IFN and antiviral cytokines, and advance our understanding of the involvement of these cells in innate responses against rotavirus.

Lessons from the mouse: potential contribution of bystander lymphocyte activation by viruses to human type 1 diabetes

Viruses are considered to be potential key modulators of type 1 diabetes mellitus, with several possible mechanisms proposed for their modes of action. Here we discuss the evidence for virus involvement, including pancreatic infection and the induction of T cell-mediated molecular mimicry. A particular focus of this review is the further possibility that virus infection triggers bystander activation of pre-existing autoreactive lymphocytes. In this scenario, the virus triggers dendritic cell maturation and proinflammatory cytokine secretion by engaging pattern recognition receptors. These proinflammatory cytokines provoke bystander autoreactive lymphocyte activation in the presence of cognate autoantigen, which leads to enhanced beta cell destruction. Importantly, this mechanism does not necessarily involve pancreatic virus infection, and its virally non-specific nature suggests that it might represent a means commonly employed by multiple viruses. The ability of viruses specifically associated with type 1 diabetes, including group B coxsackievirus, rotavirus and influenza A virus, to induce these responses is also examined. The elucidation of a mechanism shared amongst several viruses for accelerating progression to type 1 diabetes would facilitate the identification of important targets for disease intervention.

Rotavirus infection induces transient pancreatic involution and hyperglycemia in weanling mice

Rotavirus is a ubiquitous double-stranded RNA virus responsible for most cases of infantile gastroenteritis. It infects pancreatic islets in vitro and is implicated as a trigger of autoimmune destruction of islet beta cells leading to type 1 diabetes, but pancreatic pathology secondary to rotavirus infection in vivo has not been documented. To address this issue, we inoculated 3 week-old C57Bl/6 mice at weaning with rhesus rotavirus, which is closely related to human rotaviruses and known to infect mouse islets in vitro. Virus was quantified in tissues by culture-isolation and enzyme-linked immunosorbent assay. A requirement for viral double stranded RNA was investigated in toll-like receptor 3 (TLR3)-deficient mice. Cell proliferation and apoptosis, and insulin expression, were analyzed by immunohistochemistry. Following rotavirus inoculation by gavage, two phases of mild, transient hyperglycemia were observed beginning after 2 and 8 days. In the first phase, widespread apoptosis of pancreatic cells was associated with a decrease in pancreas mass and insulin production, without detectable virus in the pancreas. These effects were mimicked by injection of the double-stranded RNA mimic, polyinosinic-polycytidylic acid, and were TLR3-dependent. By the second phase, the pancreas had regenerated but islets were smaller than normal and viral antigen was then detected in the pancreas for several days. These findings directly demonstrate pathogenic effects of rotavirus infection on the pancreas in vivo, mediated initially by the interaction of rotavirus double-stranded RNA with TLR3.

Rotavirus activates lymphocytes from non-obese diabetic mice by triggering toll-like receptor 7 signaling and interferon production in plasmacytoid dendritic cells

It has been proposed that rotavirus infection promotes the progression of genetically-predisposed children to type 1 diabetes, a chronic autoimmune disease marked by infiltration of activated lymphocytes into pancreatic islets. Non-obese diabetic (NOD) mice provide a model for the human disease. Infection of adult NOD mice with rhesus monkey rotavirus (RRV) accelerates diabetes onset, without evidence of pancreatic infection. Rather, RRV spreads to the pancreatic and mesenteric lymph nodes where its association with antigen-presenting cells, including dendritic cells, induces cellular maturation. RRV infection increases levels of the class I major histocompatibility complex on B cells and proinflammatory cytokine expression by T cells at these sites. In autoimmunity-resistant mice and human mononuclear cells from blood, rotavirus-exposed plasmacytoid dendritic cells contribute to bystander polyclonal B cell activation through type I interferon expression. Here we tested the hypothesis that rotavirus induces bystander activation of lymphocytes from NOD mice by provoking dendritic cell activation and proinflammatory cytokine secretion. NOD mouse splenocytes were stimulated with rotavirus and assessed for activation by flow cytometry. This stimulation activated antigen-presenting cells and B cells independently of virus strain and replicative ability. Instead, activation depended on virus dose and was prevented by blockade of virus decapsidation, inhibition of endosomal acidification and interference with signaling through Toll-like receptor 7 and the type I interferon receptor. Plasmacytoid dendritic cells were more efficiently activated than conventional dendritic cells by RRV, and contributed to the activation of B and T cells, including islet-autoreactive CD8+ T cells. Thus, a double-stranded RNA virus can induce Toll-like receptor 7 signaling, resulting in lymphocyte activation. Our findings suggest that bystander activation mediated by type I interferon contributes to the lymphocyte activation observed following RRV infection of NOD mice, and may play a role in diabetes acceleration by rotavirus.

Evidences and consequences of extra-intestinal spread of rotaviruses in humans and animals

Rotavirus is recognized as one of the main diarrheal pathogens in young children and animals. The prevailing central dogma of rotavirus infection states that the infection is confined in the gastrointestinal tract. However, increasing evidences indicate that rotavirus infection is systemic. Clinical case reports of systemic manifestations to rotavirus infection in children has continued to accumulate over the past years. The use of animal models provided pathological and molecular evidences for extra-intestinal infection of rotaviruses. The mechanism correlated with the extra-intestinal spread of rotavirus infection from the intestine is through cell-free and cell-associated viremia. The extent of the extra-intestinal spread of rotavirus infection has not yet been fully elucidated; whether it can only affect a limited number of organs and tissues or capable of involving the body as a whole. Moreover, the influence of systemic rotavirus infections remains to be determined. In this review, combination of previous and new data are outlined to help in better understanding of the extra-intestinal infections of rotaviruses.

Systemic rotavirus infection

A new paradigm of rotavirus disease is emerging and rotavirus infection is no longer considered to be localized and confined to the GI tract. New evidence indicates that rotavirus infection is systemic. Viral antigen and infectious virus frequently enter the circulation in both children and animal model systems. Clinical case reports of systemic sequelae to rotavirus infection in children continue to accumulate, suggesting involvement in systemic disease syndromes. The use of animal models is providing biological and molecular evidence for infection at peripheral sites. Thus, infection at peripheral sites may account for reports of systemic sequelae to rotavirus infection. The importance of systemic sequelae and the ability of vaccination to prevent such sequelae remains to be determined.

Malarial infection of female BWF1 lupus mice alters the redox state in kidney and liver tissues and confers protection against lupus nephritis

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by an imbalanced redox state and increased apoptosis. Tropical infections, particularly malaria, may confer protection against SLE. Oxidative stress is a hallmark of SLE. We have measured changes in the levels of nitric oxide (NO), hydrogen peroxide (H₂O₂), malondialdehyde (MDA), and reduced glutathione (GSH) in both kidney and liver tissues of female BWF1 lupus mice, an experimental model of SLE, after infection with either live or gamma-irradiated malaria. We observed a decrease in NO, H₂O₂, and MDA levels in kidney tissues after infection of lupus mice with live malaria. Similarly, the levels of NO and H₂O₂ were significantly decreased in the liver tissues of lupus mice after infection with live malaria. Conversely, GSH levels were obviously increased in both kidney and liver tissues after infection of lupus mice with either live or gamma-irradiated malaria. Liver and kidney functions were significantly altered after infection of lupus mice with live malaria. We further investigated the ultrastructural changes and detected the number of apoptotic cells in kidney and liver tissues in situ by electron microscopy and TUNEL assays. Our data reveal that infection of lupus mice with malaria confers protection against lupus nephritis.

Virus infections in type 1 diabetes

The precise etiology of type 1 diabetes (T1D) is still unknown, but viruses have long been suggested as a potential environmental trigger for the disease. However, despite decades of research, the body of evidence supporting a relationship between viral infections and initiation or acceleration of islet autoimmunity remains largely circumstantial. The most robust association with viruses and T1D involves enterovirus species, of which some strains have the ability to induce or accelerate disease in animal models. Several hypotheses have been formulated to mechanistically explain how viruses may affect islet autoimmunity and β-cell decay. The recent observation that certain viral infections, when encountered at the right time and infectious dose, can prevent autoimmune diabetes illustrates that potential relationships may be more complex than previously thought. Here, we provide a concise summary of data obtained in mouse models and humans, and identify future avenues toward a better characterization of the association between viruses and T1D.

Innate cellular responses to rotavirus infection

Rotavirus is a leading cause of severe dehydrating diarrhoea in infants and young children. Following rotavirus infection in the intestine an innate immune response is rapidly triggered. This response leads to the induction of type I and type III interferons (IFNs) and other cytokines, resulting in a reduction in viral replication. Here we review the current literature describing the detection of rotavirus infection by pattern recognition receptors within host cells, the subsequent molecular mechanisms leading to IFN and cytokine production, and the processes leading to reduced rotavirus replication and the development of protective immunity. Rotavirus countermeasures against innate responses, and their roles in modulating rotavirus replication in mice, also are discussed. By linking these different aspects of innate immunity, we provide a comprehensive overview of the host’s first line of defence against rotavirus infection. Understanding these processes is expected to be of benefit in improving strategies to combat rotavirus disease.

Alteration of the thymic T cell repertoire by rotavirus infection is associated with delayed type 1 diabetes development in non-obese diabetic mice

Rotaviruses are implicated as a viral trigger for the acceleration of type 1 diabetes in children. Infection of adult non-obese diabetic (NOD) mice with rotavirus strain RRV accelerates diabetes development, whereas RRV infection in infant NOD mice delays diabetes onset. In this study of infant mice, RRV titers and lymphocyte populations in the intestine, mesenteric lymph nodes (MLN) and thymus of NOD mice were compared with those in diabetes-resistant BALB/c and C57BL/6 mice. Enhanced intestinal RRV infection occurred in NOD mice compared with the other mouse strains. This was associated with increases in the frequency of CD8αβ TCRαβ intraepithelial lymphocytes, and their PD-L1 expression. Virus spread to the MLN and T cell numbers there also were greatest in NOD mice. Thymic RRV infection is shown here in all mouse strains, often in combination with alterations in T cell ontogeny. Infection lowered thymocyte numbers in infant NOD and C57BL/6 mice, whereas thymocyte production was unaltered overall in infant BALB/c mice. In the NOD mouse thymus, effector CD4⁺ T cell numbers were reduced by infection, whereas regulatory T cell numbers were maintained. It is proposed that maintenance of thymic regulatory T cell numbers may contribute to the increased suppression of inflammatory T cells in response to a strong stimulus observed in pancreatic lymph nodes of adult mice infected as infants. These findings show that rotavirus replication is enhanced in diabetes-prone mice, and provide evidence that thymic T cell alterations may contribute to the delayed diabetes onset following RRV infection.

Rotavirus acceleration of murine type 1 diabetes is associated with a T helper 1-dependent specific serum antibody response and virus effects in regional lymph nodes

AIMS/HYPOTHESIS

Rotavirus infection in at-risk children correlates with production of serum autoantibodies indicative of type 1 diabetes progression. Oral infection with rhesus monkey rotavirus (RRV) accelerates diabetes onset in mice. This relates to their rotavirus-specific serum antibody titre and local pro-inflammatory cytokine induction without pancreatic infection. Our aim was to further investigate the roles of serum antibodies and viral extra-intestinal spread in diabetes acceleration by rotavirus.

METHODS

Rotavirus-specific serum antibody production was detected by ELISA in diabetes-prone mice given either inactivated or low-dose RRV, in relation to their diabetes development. Serum anti-rotavirus antibody titres and infectious virus in lymph nodes were measured in mice given RRV or porcine rotavirus CRW-8. In lymph node cells, rotavirus antigen presence and immune activation were determined by flow cytometry, in conjunction with cytokine mRNA levels.

RESULTS

Acceleration of diabetes by RRV required virus replication, which correlated with antibody presence. CRW-8 induced similar specific total immunoglobulin and IgA titres to those induced by RRV, but did not accelerate diabetes. RRV alone elicited specific serum IgG antibodies with a T helper (Th)1 bias, spread to regional lymph nodes and activated antigen-presenting cells at these sites. RRV increased Th1-specific cytokine expression in pancreatic lymph nodes. Diabetes onset was more rapid in the RRV-infected mice with the greater Th1 bias.

CONCLUSIONS/INTERPRETATION

Acceleration of murine diabetes by rotavirus is virus strain-specific and associated with virus spread to regional lymph nodes, activation of antigen-presenting cells at these sites and induction of a Th1-dominated antibody and cytokine response.

Helminth mediated modulation of Type 1 diabetes (T1D)

Type 1 diabetes is increasing dramatically in incidence in the developed world. While there may be several reasons for this, improved sanitation and public health measures have altered our interactions with certain infectious agents such as helminths. There is increasing interest in the use of helminths or their products to alleviate inflammatory or allergic conditions. Using rodent models of diabetes, it has been possible to explore the therapeutic potential of both live infections as well as helminth-derived products on the development of autoimmunity. This review provides an overview of the findings from animal models and additionally explores the potential for translation to the clinic.

Prevention or acceleration of type 1 diabetes by viruses

Type 1 diabetes is an autoimmune disease characterized by the destruction of insulin-producing pancreatic β-cells. Even though extensive scientific research has yielded important insights into the immune mechanisms involved in pancreatic β-cell destruction, little is known about the events that trigger the autoimmune process. Recent epidemiological and experimental data suggest that environmental factors are involved in this process. In this review, we discuss the role of viruses as an environmental factor on the development of type 1 diabetes, and the immune mechanisms by which they can trigger or protect against this pathology.

Viral infections and diabetes

Type 1 diabetes mellitus (T1DM) is a multi-factorial autoimmune disease determined by the interaction of genetic, environmental and immunologic factors. One of the environmental risk factors identified by a series of independent studies is represented by viral infection, with strong evidence showing that viruses can indeed infect pancreatic beta cells with consequent effects ranging from functional damage to cell death. In this chapter we review the data obtained both in man and in experimental animal models in support of the potential participation of viral infections to Type 1 diabetes pathogenesis, with a particular emphasis on virus-triggered islet inflammation, beta-cell dysfunction and autoimmunity.

Helminth infection and type 1 diabetes

The increasing incidence of type 1 diabetes (T1D) and autoimmune diseases in industrialized countries cannot be exclusively explained by genetic factors. Human epidemiological studies and animal experimental data provide accumulating evidence for the role of environmental factors, such as infections, in the regulation of allergy and autoimmune diseases. The hygiene hypothesis has formally provided a rationale for these observations, suggesting that our co-evolution with pathogens has contributed to the shaping of the present-day human immune system. Therefore, improved sanitation, together with infection control, has removed immunoregulatory mechanisms on which our immune system may depend. Helminths are multicellular organisms that have developed a wide range of strategies to manipulate the host immune system to survive and complete their reproductive cycles successfully. Immunity to helminths involves profound changes in both the innate and adaptive immune compartments, which can have a protective effect in inflammation and autoimmunity. Recently, helminth-derived antigens and molecules have been tested in vitro and in vivo to explore possible applications in the treatment of inflammatory and autoimmune diseases, including T1D. This exciting approach presents numerous challenges that will need to be addressed before it can reach safe clinical application. This review outlines basic insight into the ability of helminths to modulate the onset and progression of T1D, and frames some of the challenges that helminth-derived therapies may face in the context of clinical translation.

Early childhood infections and the risk of islet autoimmunity: the Diabetes Autoimmunity Study in the Young (DAISY)

OBJECTIVE

Type 1 diabetes is a common chronic childhood disease, and the incidence is increasing globally. Childhood infections are considered a potential environmental trigger of type 1 diabetes. Alternatively, improved hygiene and reduced childhood infections could explain the increase in type 1 diabetes in developed countries. The association of reported illnesses during infancy and later development of islet autoimmunity (IA) were examined in the Diabetes Autoimmunity Study in the Young.

RESEARCH DESIGN AND METHODS

Complete illness interviews through 9 months of age were collected for 1,729 children-1,174 without a family history of type 1 diabetes and 555 with a first-degree relative with type 1 diabetes. Persistent IA was defined as positive antibodies to insulin, glutamic acid decarboxylase, or tyrosine phosphatase on at least two consecutive study visits.

RESULTS

There were 109 children with persistent IA among the 1,729 children with illness records. A greater number of gastrointestinal illnesses were associated with an increased risk of IA, but only among children who were exposed to gluten-containing grains (wheat or barley) either <4 months of age (hazard ratio 1.37 [95% CI 1.22-1.55]; P < 0.0001) or ≥7 months of age (1.12 [1.05-1.19]; P = 0.0005) compared with 4-6 months of age (P for interaction = 0.02). There were no associations of upper respiratory symptoms, respiratory illnesses, or fevers with IA.

CONCLUSIONS

Specific pathogens such as enteroviruses or rotavirus may increase the risk of IA in the presence of existing inflammation induced by diet.

Immune cell crosstalk in type 1 diabetes

The development of type 1 diabetes involves a complex interaction between pancreatic beta-cells and cells of both the innate and adaptive immune systems. Analyses of the interactions between natural killer (NK) cells, NKT cells, different dendritic cell populations and T cells have highlighted how these different cell populations can influence the onset of autoimmunity. There is evidence that infection can have either a potentiating or inhibitory role in the development of type 1 diabetes. Interactions between pathogens and cells of the innate immune system, and how this can influence whether T cell activation or tolerance occurs, have been under close scrutiny in recent years. This Review focuses on the nature of this crosstalk between the innate and the adaptive immune responses and how pathogens influence the process.

Interferon induced with helicase C domain 1 (IFIH1) and virus-induced autoimmunity: a review

In addition to genetic factors, environmental triggers, including viruses and other pathogens, are thought to play a major role in the development of autoimmune disease. Recent findings have shown that viral-induced autoimmunity is likely to be genetically determined. In large-scale genetic analyses, an association of interferon induced with helicase C domain 1 (IFIH1) gene variants encoding a viral RNA-sensing helicase with susceptibility to several autoimmune diseases was found. To date, the precise role of IFIH1 in pathogenic mechanisms of viral-induced autoimmunity has yet to be fully elucidated. However, recent reports suggest that IFIH1 may play a role in the etiology of type 1 diabetes. Rare IFIH1 alleles have been shown to be protective against diabetes, and their carriage correlates with lower production of this helicase and its functional disruption. In contrast, upregulation of IFIH1 expression by viruses is associated with more severe disease, and could exacerbate the autoimmune process in susceptible individuals.

Infection and type 1 diabetes mellitus - a two edged sword?

Infection by various viral and bacterial pathogens has long been proposed as one of the etiologies of autoimmune diabetes. Many theories, ranging from direct cytolysis of pancreatic islet cells to immunological processes such as antigen mimicry and polyclonal lymphocyte activation, tried to explain the epidemiological correlation between infections and diabetes, supported by information from human and animal studies. However, a direct correlation and exact mechanism continue to elude investigators due to scarce and conflicting data. Interestingly, there is also data to support an opposite role for infection in the development of type 1 diabetes, as several pathogens demonstrated a protective effect from this disease. This article reviews the current data available from clinical studies and animal models, while trying to explain the different mechanisms underlying these findings.

Kinetics of transmission, infectivity, and genome stability of two novel mouse norovirus isolates in breeding mice

Murine noroviruses are a recently discovered group of viruses found within mouse research colonies in many animal facilities worldwide. In this study, we used 2 novel mouse norovirus (MNV) wildtype isolates to examine the kinetics of transmission and tissue distribution in breeding units of NOD.CB17-Prkdc(scid)/J and backcrossed NOD.CB17-Prkdc(scid)/J x NOD/ShiLtJ (N1) mice. Viral shedding in feces and dissemination to tissues of infected offspring mice were monitored by RT-PCR over a 6-wk period postpartum. Histologic sections of tissues from mice exposed to MNV were examined for lesions and their sera monitored for the presence of antibodies to MNV. Viruses shed in feces of parental and offspring mice were compared for sequence homology of the Orf2 gene. Studies showed that the wildtype viruses MNV5 and MNV6 behaved differently in terms of the kinetics of transmission and distribution to tissues of offspring mice. For MNV5, virus transmission from parents to offspring was not seen before 3 wk after birth, and neither isolate was transmitted between cages of infected and control mice. Susceptibility to infection was statistically different between the 2 mouse strains used in the study. Both immunodeficient NOD.CB17-Prkdc(scid)/J mice and NOD. CB17-Prkdc(scid)/J x NOD/ShiLtJ offspring capable of mounting an immune response shed virus in their feces throughout the 6-wk study period, but no gross or histologic lesions were present in infected tissues. Progeny viruses isolated from the feces of infected offspring showed numerous mutations in the Orf2 gene for MNV5 but not MNV6. These results confirm previous studies demonstrating that the biology of MNV in mice varies substantially with each virus isolate and mouse strain infected.

Rotavirus infection accelerates type 1 diabetes in mice with established insulitis

Infection modulates type 1 diabetes, a common autoimmune disease characterized by the destruction of insulin-producing islet beta cells in the pancreas. Childhood rotavirus infections have been associated with exacerbations in islet autoimmunity. Nonobese diabetic (NOD) mice develop lymphocytic islet infiltration (insulitis) and then clinical diabetes, whereas NOD8.3 TCR mice, transgenic for a T-cell receptor (TCR) specific for an important islet autoantigen, show more rapid diabetes onset. Oral infection of infant NOD mice with the monkey rotavirus strain RRV delays diabetes development. Here, the effect of RRV infection on diabetes development once insulitis is established was determined. NOD and NOD8.3 TCR mice were inoculated with RRV aged > or = 12 and 5 weeks, respectively. Diabetes onset was significantly accelerated in both models (P < 0.024), although RRV infection was asymptomatic and confined to the intestine. The degree of diabetes acceleration was related to the serum antibody titer to RRV. RRV-infected NOD mice showed a possible trend toward increased insulitis development. Infected males showed increased CD8(+) T-cell proportions in islets. Levels of beta-cell major histocompatibility complex class I expression and islet tumor necrosis factor alpha mRNA were elevated in at least one model. NOD mouse exposure to mouse rotavirus in a natural experiment also accelerated diabetes. Thus, rotavirus infection after beta-cell autoimmunity is established affects insulitis and exacerbates diabetes. A possible mechanism involves increased exposure of beta cells to immune recognition and activation of autoreactive T cells by proinflammatory cytokines. The timing of infection relative to mouse age and degree of insulitis determines whether diabetes onset is delayed, unaltered, or accelerated.

The curiously suspicious: infectious disease may ameliorate an ongoing autoimmune destruction in systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease, which can arise from a combination of genetic and environmental factors. In the past, infections (Epstein Barr virus, parvovirus B-19) have been indicated to play a causative role in the development of autoimmune diseases, such as SLE. On the other hand, with the emergence of the "hygiene hypothesis" infections have also shown to play a protective role in autoimmune diseases. Two case studies are presented which provide clinical evidence of SLE patients with severe, long-term disease, despite immunosuppresive therapy. The course of both diseases changed remarkably after they experienced infections with multiple microbes (bacterial, viral and fungal). Surprisingly, their clinical and laboratory signs of SLE normalized and they are now symptom-free after 5 and 3year follow-ups. The second patient has even had a normal pregnancy, which was a trigger factor for disease flare in the past. The infections presumably changed the host immune systems and the mechanisms of their protective effects are most likely multifactorial. Our cases illustrate that infections could be beneficial in SLE patients and re-directing research toward novel innate-based SLE therapy should be explored.

Rotavirus vaccines: recent developments and future considerations

Two new vaccines have recently been shown to be safe and effective in protecting young children against severe rotavirus gastroenteritis. Although both vaccines are now marketed worldwide, it is likely that improvements to these vaccines and/or the development of future generations of rotavirus vaccines will be desirable. This Review addresses recent advances in our knowledge of rotavirus, the host immune response to rotavirus infection and the efficacy and safety of the new vaccines that will be helpful for improving the existing rotavirus vaccines, or developing new rotavirus vaccines in the future.