Famara Sane

Enteroviruses and type 1 diabetes: towards a better understanding of the relationship

Environmental factors, especially viruses, are involved in the initiation or the acceleration of type 1 diabetes (T1D) pathogenesis. Epidemiological data strongly suggest that enteroviruses, such as coxsackievirus B4 (CV‐B4), can be associated with T1D. It has been demonstrated that enterovirus infections were significantly more prevalent in at risk individuals, such as siblings of diabetic patients, when they developed anti‐β‐cell autoantibodies or T1D, and in recently diagnosed diabetic patients, compared with control subjects. The isolation of CV‐B4 from the pancreas of diabetic patients strengthened the hypothesis of a relationship between the virus and the disease. Studies performed in vitro and in vivo in animal models helped to discover mechanisms of the infection of pancreas and other tissues, potentially able to play a role in the pathogenesis of T1D. Interestingly, it cannot be excluded that enteroviruses behave as half‐devil half‐angel since experimental studies suggest that, in certain conditions, these agents would be able to protect individuals against the disease. All of the plausible mechanisms by which enterovirus may be related to T1D will be reviewed here. Copyright

Synergistic Effect between Colistin and Bacteriocins in Controlling Gram-Negative Pathogens and Their Potential To Reduce Antibiotic Toxicity in Mammalian Epithelial Cells

ABSTRACT Pathogens resistant to most conventional antibiotics are a harbinger of the need to discover novel antimicrobials and anti-infective agents and develop innovative strategies to combat them. The aim of this study was to assess the in vitro activity of colistin alone or in combination with two bacteriocins, nisin A and pediocin PA-1/AcH, against Salmonella choleraesuis ATCC 14028, Pseudomonas aeruginosa ATCC 27853, Yersinia enterocolitica ATCC 9610, and Escherichia coli ATCC 35150 (O157:H7). The strain most sensitive to colistin was enterohemorrhagic E. coli O157:H7, which was inhibited at a concentration of about 0.12 μg/ml. When nisin A (1.70 μg/ml) or pediocin PA-1/AcH (1.56 μg/ml) was combined with colistin, the concentrations required to inhibit E. coli O157:H7 were 0.01 and 0.03 μg/ml, respectively. The in vitro antigenotoxic effect of colistin was determined by using the comet assay method to measure the level of DNA damage in freshly isolated human peripheral blood leukocytes (PBLs) incubated with colistin for 1 h at 37°C. Changes in the tail extents of PBLs of about 69.29 ± 0.08 μm were observed at a final colistin concentration of about 550 ng/ml. Besides the synergistic effect, the combination of colistin (1 mg/ml) and nisin (2 mg/ml) permitted us to re-evaluate the toxic effect of colistin on Vero (monkey kidney epithelial) cells.

Coxsackievirus B4 and type 1 diabetes pathogenesis: contribution of animal models

The role of enteroviruses, in particular type B coxsackieviruses (CV‐B), in type 1 diabetes (T1D) pathogenesis is supported by epidemiological, clinical and experimental observations.

Immunology in the clinic review series; focus on type 1 diabetes and viruses: role of antibodies enhancing the infection with Coxsackievirus-B in the pathogenesis of type 1 diabetes

OTHER THEMES PUBLISHED IN THIS IMMUNOLOGY IN THE CLINIC REVIEW SERIES

Immunology in the clinic review series; focus on type 1 diabetes and viruses: enterovirus, thymus and type 1 diabetes pathogenesis

OTHER THEMES PUBLISHED IN THIS IMMUNOLOGY IN THE CLINIC REVIEW SERIES

Persistent Infection of Thymic Epithelial Cells with Coxsackievirus B4 Results in Decreased Expression of Type 2 Insulin-Like Growth Factor

ABSTRACT It has been hypothesized that a disturbance of central self-tolerance to islet β cells may play a role in the enteroviral pathogenesis of type 1 diabetes. Whether enteroviruses can induce an impaired expression of β-cell self-antigens in thymic epithelial cells has been investigated in a murine thymic epithelial (MTE) cell line. This cell line was permissive to the diabetogenic group B4 coxsackievirus (CV-B4) strain CV-B4 E2 and spontaneously expressed type 2 insulin-like growth factor (Igf2), the dominant self-antigen of the insulin family. In this model, a persistent replication of CV-B4 E2 was obtained, as attested to by the prolonged detection of intracellular positive- and negative-strand viral RNA by reverse transcription-PCR (RT-PCR) and capsid protein VP1 by immunofluorescent staining and by the release of infectious particles in culture supernatants. The chronic stage of the infection was characterized by a low proportion of VP1-positive cells (1 to 2%), whereas many cells harbored enteroviral RNA, as displayed by RT-PCR without extraction applied directly to a few cells. Igf2 mRNA and IGF-2 protein were dramatically decreased in CV-B4 E2-infected MTE cell cultures compared with mock-infected cultures, whereas housekeeping and interleukin-6 (Il6) gene expression was maintained and Igf1 mRNA was decreased, but to a lower extent. Inoculation of CV-B3, CV-B4 JVB, or echovirus 1 resulted in a low level of IGF-2 in culture supernatants as well, whereas herpes simplex virus 1 stimulated the production of the protein. Thus, a persistent infection of a thymic epithelial cell line with enteroviruses like CV-B4 E2 can result in a disturbed production of IGF-2, a protein involved in central self-tolerance toward islet β cells.

Group B coxsackieviruses and autoimmunity: focus on Type 1 diabetes

Group B coxsackieviruses (CVB) and/or their components have been found in the blood and pancreas of patients with Type 1 diabetes (T1D). CVB infections lead to the activation of the innate and adaptive immune systems, which can result in the induction or aggravation of autoimmune processes. Persistent and/or repeated infections of pancreas islet β cells with CVB and the resulting production of IFN-α and inflammatory mediators, combined with a predisposed genetic background, may induce bystander activation of autoimmune effector T cells and an autoreactive response to islet self-antigens through molecular mimicry. Moreover, the antibody-dependent enhancement of CVB infection of monocytes, as well as infection of the thymus can intervene in the pathogenesis of T1D. In contrast with the deleterious effect of CVB, it has been shown that these viruses can protect against the development of T1D under certain experimental conditions. The role of CVB in autoimmunity is complex, and therefore a better understanding of the inducer versus protective effects of these viruses in T1D will help to design new strategies to treat and prevent the disease.

Enteroviruses and type 1 diabetes.

Are clearly linked, but the mechanism is yet to be explained

Serum-Dependent Enhancement of Coxsackievirus B4-Induced Production of IFNα, IL-6 and TNFα by Peripheral Blood Mononuclear Cells

Only a few reports have been published on the interactions between Coxsackievirus B4 (CVB4) and human peripheral blood mononuclear cells (PBMC) but have not been extensively documented. Human serum containing non-neutralizing anti-CVB4 antibodies increased CVB4-induced synthesis of IFNα by PBMC. In this study, we determined if CVB4 and human serum have the ability to activate inflammatory cytokines in addition to IFNα in PBMC cultures. PBMC from healthy donors were inoculated with infectious, inactivated CVB4 or with CVB4 incubated with dilutions of human serum or polyvalent IgG with anti-CVB4 activity. Levels of IFNα, TNFα, IL-6, IL-12, IFNγ and IL-10 in the cell-free supernatants of PBMC cultures were measured using ELISA. Infection was assessed by real-time PCR. PBMC inoculated with CVB4 produced inflammatory cytokines but not IFNα. When CVB4 was incubated with serum or IgG, IFNα was detected in the culture supernatants, and high concentrations of TNFα and IL-6 were measured. The concentrations of TNFα and IL-6 were not reduced in cultures inoculated with inactivated CVB4, whereas the IgG-dependent enhancement of IFNα, IL-6 and TNFα production with inactivated virus was suppressed. The potentiation of IFNα production was associated with a high intracellular viral load. Infectious and non-infectious CVB4 can induce the production of inflammatory cytokines but not IFNα by PBMC. High levels of IFNα, in addition to TNFα and IL-6, in culture supernatants were obtained when infectious CVB4 was combined with immune serum or IgG, and they were associated with high amounts of intracellular viral RNA.

New Insights into the Understanding of Hepatitis C Virus Entry and Cell-to-Cell Transmission by Using the Ionophore Monensin A

ABSTRACT In our study, we characterized the effect of monensin, an ionophore that is known to raise the intracellular pH, on the hepatitis C virus (HCV) life cycle. We showed that monensin inhibits HCV entry in a pangenotypic and dose-dependent manner. Monensin induces an alkalization of intracellular organelles, leading to an inhibition of the fusion step between viral and cellular membranes. Interestingly, we demonstrated that HCV cell-to-cell transmission is dependent on the vesicular pH. Using the selective pressure of monensin, we selected a monensin-resistant virus which has evolved to use a new entry route that is partially pH and clathrin independent. Characterization of this mutant led to the identification of two mutations in envelope proteins, the Y297H mutation in E1 and the I399T mutation in hypervariable region 1 (HVR1) of E2, which confer resistance to monensin and thus allow HCV to use a pH-independent entry route. Interestingly, the I399T mutation introduces an N-glycosylation site within HVR1 and increases the density of virions and their sensitivity to neutralization with anti-apolipoprotein E (anti-ApoE) antibodies, suggesting that this mutation likely induces conformational changes in HVR1 that in turn modulate the association with ApoE. Strikingly, the I399T mutation dramatically reduces HCV cell-to-cell spread. In summary, we identified a mutation in HVR1 that overcomes the vesicular pH dependence, modifies the biophysical properties of particles, and drastically reduces cell-to-cell transmission, indicating that the regulation by HVR1 of particle association with ApoE might control the pH dependence of cell-free and cell-to-cell transmission. Thus, HVR1 and ApoE are critical regulators of HCV propagation. IMPORTANCE Although several cell surface proteins have been identified as entry factors for hepatitis C virus (HCV), the precise mechanisms regulating its transmission to hepatic cells are still unclear. In our study, we used monensin A, an ionophore that is known to raise the intracellular pH, and demonstrated that cell-free and cell-to-cell transmission pathways are both pH-dependent processes. We generated monensin-resistant viruses that displayed different entry routes and biophysical properties. Thanks to these mutants, we highlighted the importance of hypervariable region 1 (HVR1) of the E2 envelope protein for the association of particles with apolipoprotein E, which in turn might control the pH dependency of cell-free and cell-to-cell transmission.