Virus-induced diabetes mellitus: infection of mice with variants of encephalomyocarditis virus, coxsackievirus B4, and reovirus type 3

Effects of Intestinal Fungi and Viruses on Immune Responses and Inflammatory Bowel Diseases

The intestinal microbiota comprises diverse fungal and viral components, in addition to bacteria. These microbes interact with the immune system and affect human physiology. Advances in metagenomics have associated inflammatory and autoimmune diseases with alterations in fungal and viral species in the gut. Studies of animal models have found that commensal fungi and viruses can activate host-protective immune pathways related to epithelial barrier integrity, but can also induce reactions that contribute to events associated with inflammatory bowel disease. Changes in our environment associated with modernization and the COVID-19 pandemic have exposed humans to new fungi and viruses, with unknown consequences. We review the lessons learned from studies of animal viruses and fungi commonly detected in the human gut and how these might affect health and intestinal disease.

Identification of a conserved virion-stabilizing network inside the interprotomer pocket of enteroviruses

Enteroviruses pose a persistent and widespread threat to human physical health, with no specific treatments available. Small molecule capsid binders have the potential to be developed as antivirals that prevent virus attachment and entry into host cells. To aid with broad-range drug development, we report here structures of coxsackieviruses B3 and B4 bound to different interprotomer-targeting capsid binders using single-particle cryo-EM. The EM density maps are beyond 3 Å resolution, providing detailed information about interactions in the ligand-binding pocket. Comparative analysis revealed the residues that form a conserved virion-stabilizing network at the interprotomer site, and showed the small molecule properties that allow anchoring in the pocket to inhibit virus disassembly.

The virome in host health and disease

The mammalian virome includes diverse commensal and pathogenic viruses that evoke a broad range of immune responses from the host. Sustained viral immunomodulation is implicated in a variety of inflammatory diseases, but also confers unexpected benefits to the host. These outcomes of viral infections are often dependent on host genotype. Moreover, it is becoming clear that the virome is part of a dynamic network of microorganisms that inhabit the body. Therefore, viruses can be viewed as a component of the microbiome, and interactions with commensal bacteria and other microbial agents influence their behavior. This piece is a review of our current understanding of how the virome, together with other components of the microbiome, affects the function of the host immune system to regulate health and disease.

Molecular anatomy and number of antigen specific CD8 T cells required to cause type 1 diabetes

We quantified CD8 T cells needed to cause type 1 diabetes and studied the anatomy of the CD8 T cell/beta (β) cell interaction at the immunologic synapse. We used a transgenic model, in situ tetramer staining to distinguish antigen specific CD8 T cells from total T cells infiltrating islets and a variety of viral mutants selected for functional deletion(s) of various CD8 T cell epitopes. Twenty percent of CD8 T cells in the spleen were specific for all immunodominant and subdominant viral glycoprotein (GP) epitopes. CTLs to the immunodominant LCMV GP33-41 epitope accounted for 63% of the total (12.5% of tetramers). In situ hybridization analysis demonstrated only 1 to 2% of total infiltrating CD8 T cells were specific for GP33 CD8 T cell epitope, yet diabetes occurred in 94% of mice. The immunologic synapse between GP33 CD8 CTL and β cell contained LFA-1 and perforin. Silencing both immunodominant epitopes (GP33, GP276–286) in the infecting virus led to a four-fold reduction in viral specific CD8 CTL responses, negligible lymphocyte infiltration into islets and absence of diabetes.

Insulin-dependent type 1 diabetes (T1D) is characterized by elevated blood sugar, lymphocytic infiltration into the islets of Langerhans and T cell destruction of beta (β) cells. β cells produce insulin whose function is to maintain and regulate glucose hemostasis. However, in vivo, the numbers of antigen specific T cells that migrate to the islets to cause T1D, the engagement of such T cells with β cells at the immunologic synapse and the molecules expressed at the synapse are not clear. Using a transgenic model of virus induced T1D, a panel of viruses with CD8 T cell epitope mutations and in situ tetramer hybridization, we note of the total CD8 T cells infiltrating the islets, only 1–2% are antigen specific recognizing the immunodominant virus CD8 T cell epitope expressed on β cells. Immunohistochemical analysis of the synapse found between antigen specific CD8 T cells and β cells displays attachment by LFA-1 and presence of perforin, the molecule indicative of lytic activity.

Can infections protect against autoimmunity?

PURPOSE OF REVIEW

It has often been suggested that autoimmune diseases are initiated by certain infectious agents that mimic self-antigens or polyclonally activated autoreactive lymphocytes. An alternative, and not necessarily mutually exclusive, hypothesis that some infections might inhibit the onset of some autoimmune conditions has more recently been explored. In this review, the evidence suggesting that the current rise in the incidence of some autoimmune diseases is attributable to a decrease in the incidence of exposure to certain infections will be discussed.

RECENT FINDINGS

Studies using animal models have shown that some infectious agents or products derived from them have the potential to inhibit the onset of autoimmunity. These studies have led to the suggestion that human autoimmune or allergic diseases might be alleviated by the use of microbial products. There are some data that would support such an observation.

SUMMARY

The incidence of some autoimmune diseases has increased dramatically in recent years in the developed world. Many autoimmune diseases are governed by both genetic and environmental factors. Our immune system has coevolved with infectious agents. There have been marked changes in the exposure to certain infectious agents over the last 70 years. It has been proposed that certain infections of historical importance might inhibit the development of autoimmune disorder. This review highlights studies addressing the ways in which infectious agents might inhibit onset of autoimmunity, and how this might lead to the development of novel therapeutic approaches.

Modification of encephalomyocarditis virus-induced diabetes in mice by antiviral agents

The current study used a murine model of diabetes induced by the D variant of encephalomyocarditis virus (DEMC) to determine the protective effect of exogenous antiviral agents. Antivirals, which were found to inhibit the development of DEMC virus cytopathic effect in L-929 cell monolayers, were administered intraperitoneally beginning 12 h prior to DEMC virus challenge. Arildone (500 mg/kg per day) or murine interferon (3.2 X 10(6) IU/kg per day) significantly reduced the incidence of hyperglycemia at 4 days after virus challenge. The incidences of hyperglycemia were 96% in untreated, 62% in arildone, and 0% in interferon treated mice. In other experiments we found that interferon (1.6 X 10(6) IU/kg per 12 h X 3) significantly protected mice against diabetes when administered at the time of virus infection or beginning 12 h afterwards. This effect was associated with reductions in average viral titers in the heart and pancreas of infected animals relative to untreated, infected mice. The results of these studies suggest that picornavirus induced diabetes may be prevented or ameliorated by the use of antiviral agents.