Noora Nurminen

Bacteroides dorei dominates gut microbiome prior to autoimmunity in Finnish children at high risk for type 1 diabetes

The incidence of the autoimmune disease, type 1 diabetes (T1D), has increased dramatically over the last half century in many developed countries and is particularly high in Finland and other Nordic countries. Along with genetic predisposition, environmental factors are thought to play a critical role in this increase. As with other autoimmune diseases, the gut microbiome is thought to play a potential role in controlling progression to T1D in children with high genetic risk, but we know little about how the gut microbiome develops in children with high genetic risk for T1D. In this study, the early development of the gut microbiomes of 76 children at high genetic risk for T1D was determined using high-throughput 16S rRNA gene sequencing. Stool samples from children born in the same hospital in Turku, Finland were collected at monthly intervals beginning at 4–6 months after birth until 2.2 years of age. Of those 76 children, 29 seroconverted to T1D-related autoimmunity (cases) including 22 who later developed T1D, the remaining 47 subjects remained healthy (controls). While several significant compositional differences in low abundant species prior to seroconversion were found, one highly abundant group composed of two closely related species, Bacteroides dorei and Bacteroides vulgatus, was significantly higher in cases compared to controls prior to seroconversion. Metagenomic sequencing of samples high in the abundance of the B. dorei/vulgatus group before seroconversion, as well as longer 16S rRNA sequencing identified this group as Bacteroides dorei. The abundance of B. dorei peaked at 7.6 months in cases, over 8 months prior to the appearance of the first islet autoantibody, suggesting that early changes in the microbiome may be useful for predicting T1D autoimmunity in genetically susceptible infants. The cause of increased B. dorei abundance in cases is not known but its timing appears to coincide with the introduction of solid food.

Human parechovirus seroprevalence in Finland and the Netherlands

BACKGROUND Human parechoviruses (HPeVs) are RNA viruses associated with mild gastrointestinal and respiratory infections in children, but may also cause neonatal sepsis and CNS infections in infants. While the prevalence of HPeVs is known mostly among hospitalized populations, the knowledge of HPeV seroprevalence in the general population is poor. OBJECTIVES The aim of this study was to identify and compare the HPeV1-6 seroprevalence in Finnish and Dutch populations. STUDY DESIGN A type specific microneutralization assay was set up for detecting neutralizing antibodies (nABs) against HPeV types 1-6. Altogether 616 serum samples from Finnish and Dutch population were analyzed for antibodies against HPeVs. The samples were collected from Finnish children aged 1, 5 or 10 years, Finnish adults, 0- to 5-year-old Dutch children, Dutch women of childbearing age and Dutch HIV-positive men. RESULTS In both adult populations, seropositivity was high against HPeV1 (99% in Finnish and 92% in Dutch samples) and HPeV2 (86% and 95%). Against HPeV4, the seropositivity was similar (62% and 60%). In Dutch adults, nABs against HPeV5 and 6 (75% and 74%) were detected more often than in Finnish adults (35% and 57%, respectively). In contrast, seropositivity against HPeV3 was as low as 13% in the Finnish and 10% in the Dutch adults. The seroprevalence of all HPeV types increased with age. CONCLUSIONS The seroprevalence of HPeVs is high in Finnish and Dutch populations and HPeV type 2 and types 4-6 are significantly more prevalent compared to earlier reports. The seroprevalence of antibodies observed against HPeV3 was low.

Circulating CXCR5+PD-1+ICOS+ Follicular T Helper Cells Are Increased Close to the Diagnosis of Type 1 Diabetes in Children With Multiple Autoantibodies

Although type 1 diabetes (T1D) is primarily perceived as a T cell–driven autoimmune disease, islet autoantibodies are the best currently available biomarker for autoimmunity and disease risk. These antibodies are produced by autoreactive B cells, the activation of which is largely dependent on the function of CD4+CXCR5+ follicular T helper cells (Tfh). In this study, we have comprehensively characterized the Tfh- as well as B-cell compartments in a large cohort of children with newly diagnosed T1D or at different stages of preclinical T1D. We demonstrate that the frequency of CXCR5+PD-1+ICOS+–activated circulating Tfh cells is increased both in children with newly diagnosed T1D and in autoantibody-positive at-risk children with impaired glucose tolerance. Interestingly, this increase was only evident in children positive for two or more biochemical autoantibodies. No alterations in the circulating B-cell compartment were observed in children with either prediabetes or diabetes. Our results demonstrate that Tfh activation is detectable in the peripheral blood close to the presentation of clinical T1D but only in a subgroup of children identifiable by positivity for multiple autoantibodies. These findings suggest a role for Tfh cells in the pathogenesis of human T1D and carry important implications for targeting Tfh cells and/or B cells therapeutically.

Coxsackievirus B1 reveals strain specific differences in plasmacytoid dendritic cell mediated immunogenicity.

Enterovirus infections are usually mild but can also cause severe illnesses and play a role in chronic diseases, such as cardiomyopathies and type 1 diabetes. Host response to the invading virus can markedly modulate the course of the infection, and this response varies between individuals due to the polymorphism of immune response genes. However, it is currently not known if virus strains also differ in their ability to stimulate the host immune system. Coxsackievirus B1 (CBV1) causes severe epidemics in young infants and it has recently been connected with type 1 diabetes in seroepidemiological studies. This study evaluated the ability of different field isolates of CBV1 to induce innate immune responses in PBMCs. CBV1 strains differed markedly in their capacity to induce innate immune responses. Out of the 18 tested CBV1 strains two induced exceptionally strong alpha interferon (IFN‐α) response in PBMC cultures. The responding cell type was found to be the plasmacytoid dendritic cell. Such a strong innate immune response was accompanied by an up‐regulation of several other immune response genes and secretion of cytokines, which modulate inflammation, and adaptive immune responses. These results suggest that enterovirus‐induced immune activation depends on the virus strain. It is possible that the immunotype of the virus modulates the course of the infection and plays a role in the pathogenesis of chronic immune‐mediated enterovirus diseases. J. Med. Virol. 86:1412–1420, 2014.

Virus infections as potential targets of preventive treatments for type 1 diabetes.

Environmental factors play an important role in the pathogenesis of type 1 diabetes, and are attractive targets for preventive interventions. Several studies have shown that viruses can cause diabetes in animals, indicating their potential as candidates for environmental triggering agents. However, human studies have been hampered by the complex nature of the disease pathogenesis, leaving the question of viral etiology unanswered. Significant progress has recently been made in this field by searching for viruses within pancreatic tissue samples, and by carrying out prospective studies. Consequently, there is increasing evidence for a group of enteroviruses acting as possible environmental key triggers. In past studies, these viruses have been linked to type 1 diabetes. Recent studies have shown that they exert tropism to pancreatic islets, and that they are associated with the start of the beta-cell damaging process. Also, polymorphisms of the gene coding for the innate immune system sensor for enteroviruses (IFIH1) were found to modulate the risk of diabetes. Based on these findings, interest in the possible development of vaccines against these viruses has increased. However, even if enterovirus vaccines (polio vaccines) are effective and safe, we currently lack necessary information for the development of a vaccine against diabetogenic enteroviruses, e.g. regarding the identification of their specific serotypes and the causal relationship between these viruses and diabetes initiation. Ongoing research projects are currently addressing these questions, and will hopefully increase the consensus in this field. Also, new sequencing technologies will provide additional information about the whole virome, which could enable the discovery of new candidate viruses.

Influenza A virus antibodies show no association with pancreatic islet autoantibodies in children genetically predisposed to type 1 diabetes

Aims/hypothesisViral infections have long been considered potential triggers of beta cell autoimmunity and type 1 diabetes. Recent studies have suggested that influenza A virus might increase the risk of type 1 diabetes. The present study evaluates this risk association in prospectively observed children at the time when islet autoimmunity starts and autoantibodies are first detected.MethodsIgG class antibodies to influenza A virus were analysed in 95 case children whose antibody screening test turned permanently positive for two or more islet autoantibodies and from 186 autoantibody-negative and non-diabetic control children who were matched for time of birth, sex, date of sampling and HLA-conferred risk of diabetes in the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) study. Virus antibodies were measured from the first autoantibody-positive sample using an enzyme immunoassay. None of the children had been vaccinated against influenza A.ResultsThe prevalence of influenza A virus antibodies did not differ between the case and control children (42% vs 38%; p = 0.392) and the median antibody levels were also comparable in the two groups (3.0 vs 3.8 enzyme immunoassay units). A similar result was obtained when case and control children were compared separately in subgroups according to different sex, age and HLA-DQ genotype. However, girls had higher antibody levels than boys among both case and control children (median antibody levels 9.0 vs 2.3 enzyme immunoassay units; p = 0.01).Conclusions/interpretationOur results suggest that influenza A infections are not associated with the development of islet autoimmunity in young children with increased genetic susceptibility to type 1 diabetes.

Urbanization Reduces Transfer of Diverse Environmental Microbiota Indoors

Expanding urbanization is a major factor behind rapidly declining biodiversity. It has been proposed that in urbanized societies, the rarity of contact with diverse environmental microbiota negatively impacts immune function and ultimately increases the risk for allergies and other immune-mediated disorders. Surprisingly, the basic assumption that urbanization reduces exposure to environmental microbiota and its transfer indoors has rarely been examined. We investigated if the land use type around Finnish homes affects the diversity, richness, and abundance of bacterial communities indoors. Debris deposited on standardized doormats was collected in 30 rural and 26 urban households in and near the city of Lahti, Finland, in August 2015. Debris was weighed, bacterial community composition determined by high throughput sequencing of bacterial 16S ribosomal RNA (rRNA) gene on the Illumina MiSeq platform, and the percentage of four different land use types (i.e., built area, forest, transitional, and open area) within 200 m and 2000 m radiuses from each household was characterized. The quantity of doormat debris was inversely correlated with coverage of built area. The diversity of total bacterial, Proteobacterial, Actinobacterial, Bacteroidetes, and Firmicutes communities decreased as the percentage of built area increased. Their richness followed the same pattern except for Firmicutes for which no association was observed. The relative abundance of Proteobacteria and particularly Gammaproteobacteria increased, whereas that of Actinobacteria decreased with increasing built area. Neither Phylum Firmicutes nor Bacteroidetes varied with coverage of built area. Additionally, the relative abundance of potentially pathogenic bacterial families and genera increased as the percentage of built area increased. Interestingly, having domestic animals (including pets) only altered the association between the richness of Gammaproteobacteria and diversity of Firmicutes with the built area coverage suggesting that animal ownership minimally affects transfer of environmental microbiota indoors from the living environment. These results support the hypothesis that people living in densely built areas are less exposed to diverse environmental microbiota than people living in more sparsely built areas.

Human parechovirus as a minor cause of acute otitis media in children

Human parechoviruses (HPeVs) cause mild upper respiratory infections, gastrointestinal symptoms, central nervous system infections and some studies have linked them with acute otitis media (AOM). The aim of the present study was to study further the role of HPeV infections in AOM by detecting these viruses directly from middle ear fluid (MEF), respiratory and stool samples collected from children during AOM episodes. A total of 91 MEF samples, 98 nasal swab (NS) samples and 92 stool samples were collected during 100 AOM episodes in a total of 87 children aged between five to 42 months. All specimens were analyzed by real time RT-PCR for the presence of HPeV RNA. HPeV infection was diagnosed in 12 (14%) patients. HPeV RNA was detected in altogether 13 samples, including four MEF samples, three NS samples and six stool samples. One patient was positive in both stool and MEF samples. The results suggest that HPeV may play a role in some AOM cases, but it is not a major cause of AOM in children.

High-throughput multiplex quantitative polymerase chain reaction method for Giardia lamblia and Cryptosporidium species detection in stool samples.

Giardia lamblia and Cryptosporidium species belong to a complex group of pathogens that cause diseases hampering development and socioeconomic improvements in the developing countries. Both pathogens are recognized as significant causes of diarrhea and nutritional disorders. However, further studies are needed to clarify the role of parasitic infections, especially asymptomatic infections in malnutrition and stunting. We developed a high-throughput multiplex quantitative polymerase chain reaction (qPCR) method for G. lamblia and Cryptosporidium spp. detection in stool samples. The sensitivity and specificity of the method were ensured by analyzing confirmed positive samples acquired from diagnostics laboratories and participating in an external quality control round. Its capability to detect asymptomatic G. lamblia and Cryptosporidium spp. infections was confirmed by analyzing stool samples collected from 44 asymptomatic 6-month-old infants living in an endemic region in Malawi. Of these, five samples were found to be positive for G. lamblia and two for Cryptosporidium spp. In conclusion, the developed method is suitable for large-scale studies evaluating the occurrence of G. lamblia and Cryptosporidium spp. in endemic regions and for clinical diagnostics of these infections.

Coxsackievirus B1 infections are associated with the initiation of insulin-driven autoimmunity that progresses to type 1 diabetes

Aims/hypothesisIslet autoimmunity usually starts with the appearance of autoantibodies against either insulin (IAA) or GAD65 (GADA). This categorises children with preclinical type 1 diabetes into two immune phenotypes, which differ in their genetic background and may have different aetiology. The aim was to study whether Coxsackievirus group B (CVB) infections, which have been linked to the initiation of islet autoimmunity, are associated with either of these two phenotypes in children with HLA-conferred susceptibility to type 1 diabetes.MethodsAll samples were from children in the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) study. Individuals are recruited to the DIPP study from the general population of new-born infants who carry defined HLA genotypes associated with susceptibility to type 1 diabetes. Our study cohort included 91 children who developed IAA and 78 children who developed GADA as their first appearing single autoantibody and remained persistently seropositive for islet autoantibodies, along with 181 and 151 individually matched autoantibody negative control children, respectively. Seroconversion to positivity for neutralising antibodies was detected as the surrogate marker of CVB infections in serial follow-up serum samples collected before and at the appearance of islet autoantibodies in each individual.ResultsCVB1 infections were associated with the appearance of IAA as the first autoantibody (OR 2.4 [95% CI 1.4, 4.2], corrected p = 0.018). CVB5 infection also tended to be associated with the appearance of IAA, however, this did not reach statistical significance (OR 2.3, [0.7, 7.5], p = 0.163); no other CVB types were associated with increased risk of IAA. Children who had signs of a CVB1 infection either alone or prior to infections by other CVBs were at the highest risk for developing IAA (OR 5.3 [95% CI 2.4, 11.7], p < 0.001). None of the CVBs were associated with the appearance of GADA.Conclusions/interpretationCVB1 infections may contribute to the initiation of islet autoimmunity being particularly important in the insulin-driven autoimmune process.