T4 Bacteriophage and E. coli Interaction in the Murine Intestine: A Prototypical Model for Studying Host-Bacteriophage Dynamics In Vivo

Bacteriophages (phages) are viruses that infect bacteria with species- and strain-level specificity and are the most abundant biological entities across all known ecosystems. Within bacterial communities, such as those found in the gut microbiota, phages are implicated in regulating microbiota population dynamics and driving bacterial evolution. There has been renewed interest in phage research in the last decade, in part due to the host-specific killing capabilities of lytic phages, which offer a promising tool to counter the increasing threat of antimicrobial resistant bacteria. Furthermore, recent studies demonstrating that phages adhere to intestinal mucus suggest they may have a protective role in preventing bacterial invasion into the underlying epithelium. Importantly, like bacterial microbiomes, disrupted phageomes have been associated with worsened outcomes in diseases such as inflammatory bowel disease. Previous studies have demonstrated that phages can modulate the microbiome of animals and humans through fecal filtrate transplants, benefiting the host's health. With this recent wave of research comes the necessity to establish and standardize protocols for studying phages in the context of the gut microbiome. This protocol provides a set of procedures to study isolated T4 phages and their bacterial host, Escherichia coli, in the context of the murine gastrointestinal tract. The methods described here outline how to start from a phage lysate, administer it to mice and assess effects on bacterial host and phage levels. This protocol can be modified and applied to other phage-bacterial pairs and provides a starting point for studying host-phage dynamics in vivo.

Virus induced dysbiosis promotes type 1 diabetes onset

Autoimmune disorders are complex diseases of unclear etiology, although evidence suggests that the convergence of genetic susceptibility and environmental factors are critical. In type 1 diabetes (T1D), enterovirus infection and disruption of the intestinal microbiota are two environmental factors that have been independently associated with T1D onset in both humans and animal models. However, the possible interaction between viral infection and the intestinal microbiota remains unknown. Here, we demonstrate that Coxsackievirus B4 (CVB4), an enterovirus that accelerates T1D onset in non-obese diabetic (NOD) mice, induced restructuring of the intestinal microbiome prior to T1D onset. Microbiome restructuring was associated with an eroded mucosal barrier, bacterial translocation to the pancreatic lymph node, and increased circulating and intestinal commensal-reactive antibodies. The CVB4-induced change in community composition was strikingly similar to that of uninfected NOD mice that spontaneously developed diabetes, implying a mutual "diabetogenic" microbiome. Notably, members of the Bifidobacteria and Akkermansia genera emerged as conspicuous members of this diabetogenic microbiome, implicating these taxa, among others, in diabetes onset. Further, fecal microbiome transfer (FMT) of the diabetogenic microbiota from CVB4-infected mice enhanced T1D susceptibility and led to diminished expression of the short chain fatty acid receptor GPR43 and fewer IL-10-expressing regulatory CD4⁺ T cells in the intestine of naïve NOD recipients. These findings support an overlap in known environmental risk factors of T1D, and suggest that microbiome disruption and impaired intestinal homeostasis contribute to CVB-enhanced autoreactivity and T1D.

Gammaherpesvirus infection drives age-associated B cells toward pathogenicity in EAE and MS

While age-associated B cells (ABCs) are known to expand and persist following viral infection and during autoimmunity, their interactions are yet to be studied together in these contexts. Here, we directly compared CD11c⁺T-bet⁺ ABCs using models of Epstein-Barr virus (EBV), gammaherpesvirus 68 (γHV68), multiple sclerosis (MS), and experimental autoimmune encephalomyelitis (EAE), and found that each drives the ABC population to opposing phenotypes. EBV infection has long been implicated in MS, and we have previously shown that latent γHV68 infection exacerbates EAE. Here, we demonstrate that ABCs are required for γHV68-enhanced disease. We then show that the circulating ABC population is expanded and phenotypically altered in people with relapsing MS. In this study, we show that viral infection and autoimmunity differentially affect the phenotype of ABCs in humans and mice, and we identify ABCs as functional mediators of viral-enhanced autoimmunity.

Inhibition of Th1 activation and differentiation by dietary guar gum ameliorates experimental autoimmune encephalomyelitis

Dietary fibers are potent modulators of immune responses that can restrain inflammation in multiple disease contexts. However, dietary fibers encompass a biochemically diverse family of carbohydrates, and it remains unknown how individual fiber sources influence immunity. In a direct comparison of four different high-fiber diets, we demonstrate a potent ability of guar gum to delay disease and neuroinflammation in experimental autoimmune encephalomyelitis, a T cell-mediated mouse model of multiple sclerosis. Guar gum-specific alterations to the microbiota are limited, and disease protection appears to be independent of fiber-induced increases in short-chain fatty acid levels or regulatory CD4⁺ T cells. Instead, CD4⁺ T cells of guar gum-supplemented mice are less encephalitogenic due to reduced activation, proliferation, Th1 differentiation, and altered migratory potential. These findings reveal specificity in the host response to fiber sources and define a pathway of fiber-induced immunomodulation that protects against pathologic neuroinflammation.

A gut-centric view of aging: Do intestinal epithelial cells contribute to age-associated microbiota changes, inflammaging, and immunosenescence?

Intestinal epithelial cells (IECs) serve as both a physical and an antimicrobial barrier against the microbiota, as well as a conduit for signaling between the microbiota and systemic host immunity. As individuals age, the balance between these systems undergoes a myriad of changes due to age-associated changes to the microbiota, IECs themselves, immunosenescence, and inflammaging. In this review, we discuss emerging data related to age-associated loss of intestinal barrier integrity and posit that IEC dysfunction may play a central role in propagating age-associated alterations in microbiota composition and immune homeostasis.

Eo, what are we doing here?

A plethora of studies have established the importance of eosinophils in protective immunity against infections and in allergy. In this issue of Immunity, Ignacio et al. (2022) define a vital for eosinophils in coordinating a microbiota-epithelial-immune axis that maintains intestinal homeostasis.

Age-dependent grey matter demyelination is associated with leptomeningeal neutrophil accumulation

People living with multiple sclerosis (MS) experience episodic CNS white matter lesions instigated by autoreactive T cells. With age, patients with MS show evidence of gray matter demyelination and experience devastating nonremitting symptomology. What drives progression is unclear and studying this has been hampered by the lack of suitable animal models. Here, we show that passive experimental autoimmune encephalomyelitis (EAE) induced by an adoptive transfer of young Th17 cells induced a nonremitting clinical phenotype that was associated with persistent leptomeningeal inflammation and cortical pathology in old, but not young, SJL/J mice. Although the quantity and quality of T cells did not differ in the brains of old versus young EAE mice, an increase in neutrophils and a decrease in B cells were observed in the brains of old mice. Neutrophils were also found in the leptomeninges of a subset of progressive MS patient brains that showed evidence of leptomeningeal inflammation and subpial cortical demyelination. Taken together, our data show that while Th17 cells initiate CNS inflammation, subsequent clinical symptoms and gray matter pathology are dictated by age and associated with other immune cells, such as neutrophils.

Age-related susceptibility to grey matter demyelination and neurodegeneration is associated with meningeal neutrophil accumulation in an animal model of MS

People living with multiple sclerosis (MS) experience episodic central nervous system (CNS) white matter lesions instigated by autoreactive T cells. With age, MS patients show evidence of grey matter demyelination and experience devastating non-remitting symptomology. What drives progression is unclear and has been hampered by the lack of suitable animal models. Here we show that passive experimental autoimmune encephalomyelitis (EAE) induced by an adoptive transfer of young Th17 cells induces a non-remitting clinical phenotype that is associated with persistent leptomeningeal inflammation and cortical pathology in old, but not young SJL/J mice. While the quantity and quality of T cells did not differ in the brains of old vs young EAE mice, an increase in neutrophils and a decrease in B cells was observed in the brains of old mice. Neutrophils were also found in the leptomeninges of a subset of progressive MS patient brains that showed evidence of leptomeningeal inflammation and subpial cortical demyelination. Taken together, our data show that while Th17 cells initiate CNS inflammation, subsequent clinical symptoms and grey matter pathology are dictated by age and associated with other immune cells such as neutrophils.

A dietary fiber limits autoimmune neuroinflammation by restricting Th1 activation, polarization, and migration

Dietary fibers and their breakdown products have been shown to limit inflammation in multiple disease contexts. However, the term “dietary fiber” encompasses a biochemically diverse family of carbohydrates, and it remains unknown how different fiber sources influence immune cell function. To address this question, we assessed the immunomodulatory capacity of different fiber types in a mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). C57BL/6 mice were fed a control diet (5% cellulose) or diets enriched (30%) with resistant starch, inulin, pectin, or guar gum for 2 weeks prior to EAE induction. A diet rich in guar gum uniquely ameliorated the clinical, pathological, and immunological features of EAE. Limited central nervous system (CNS) infiltration of IFNγ+CD4+ T cells (Th1s) in guar gum-fed mice could be attributed to T cell-intrinsic impairment Th1 activation and polarization. Nanostring nCounter transcriptional analyses revealed downregulation of migration-associated markers in CD4+ T cells isolated from guar gum/EAE mice, which was supported by reduced cell-surface expression of integrins involved in migration into the CNS. Functionally, this translated to limited migration of guar gum-derived encephalitogenic Th1s into the CNS upon adoptive transfer into control-fed recipients, which reduced incidence and severity of EAE. However, the 16S rRNA microbiome signature and short chain fatty acid profiles were not unique in comparison to other fiber-supplemented diets, indicating a novel mechanism of action from those previously ascribed in high fiber diet studies. These data confirm the individuality of dietary fibers and identify a novel immunomodulatory function of guar gum.

This project was supported by the endMS doctoral studentship program (Multiple Sclerosis Society of Canada) (NMF, JRA), the Canadian Institutes for Health Research (PJT-148909), and the Canada Research Chair program (LCO).

Restriction of viral replication, rather than T cell immunopathology, drives lethality in MNV CR6-infected STAT1-deficient mice

Recent evidence indicates that viral components of the microbiota can contribute to intestinal homeostasis and protection from local inflammatory or infectious insults. However, host-derived mechanisms that regulate the virome remain largely unknown. Here, we used colonization of C57BL6/J mice with the model commensal murine norovirus (MNV CR6) to interrogate host-directed mechanisms of viral regulation, and show that STAT1 is a central coordinator of both viral replication and antiviral T cell responses. In STAT1-sufficient mice MNV CR6 is asymptomatic and restricted to the colon, despite the persistence of high viral loads. However, in the absence of STAT1 viral replication is disseminated and observed in key innate and adaptive immune populations.

STAT1-deficient mice develop dysregulated inflammatory CD8+ and CD4+ T cell responses, which coincide with weight loss and severe necrosis of the spleen and liver. Despite these altered T cell responses which resemble those that mediate lethal immunopathology following other model viral infections of STAT1-deficient mice, depletion of adaptive immune cells and their associated effector functions had no effect on CR6-induced disease. In contrast, therapeutic administration of an antiviral compound limited viral replication, preventing viral-induced tissue damage and death despite ongoing inflammatory antiviral T cell responses. Collectively, our data show that STAT1 restricts MNV CR6 replication within the intestinal mucosa. Unlike other model viral infections, CR6 induces disease in STAT1-deficient mice via uncontrolled viral replication rather than the concomitant development of dysregulated antiviral T cell responses.

Research in the Osborne lab is supported by the Natural Sciences and Engineering Research Council of Canada, the Canadian Institutes of Health Research, the Canada Research Chair program and scholarships from the University of British Columbia.

Differential localization and kinetics of antiviral CD8 T cell responses to chronic and acute murine norovirus infections from initiation onwards

Recent global events have highlighted the need to better understand mucosal antiviral immunity. Murine Norovirus (MNV) is small non-enveloped positive sense RNA virus that can be used as a model of intestinal viral infection. In this work we use two highly related MNV strains with distinct biological behaviors; CR6 establishes chronic colonic infection, while CW3 establishes systemic infection initiated in the small intestine and is cleared by day 8, correlating with the peak of cell-mediated adaptive immunity. Using flow cytometry and quantitative immunofluorescent microscopy (QIM) of transgenic P14 CD8 T cells specific to recombinant CR6gp33 and CW3gp33, we characterized CD8 T cell responses to CR6 and CW3 from initiation to clearance of CW3. Our data indicate that initiation of CD8 T cell division in response to CR6 infection is delayed, less robust, and largely limited to the mesenteric lymph nodes (MLNs) with less splenic division compared to CW3 infection. Further, the biogeography of P14 T cell priming differs, as early T cell expansion was restricted to distinct nodes of the MLN complex. These early differences propagate out to the time of CW3 clearance. By day 8, there is differential localization of P14 cells in the GI tract to the site of highest viral load and a larger systemic population of P14 cells following CW3 infection. Infection of MLN-deficient mice revealed a critical role for MLN surveillance in targeting P14 T cells to the GI tract following CR6 infection while the spleen plays a compensatory role in response to CW3. These results show how distinct infectious locations of a continuous mucosal surface influence the responses of antiviral CD8 T cells without confounding effects of antigenicity.

This work is supported by the Canadian Institutes for Health Research (CIHR) and a UBC 4 Year Fellowship awarded to Blair K Hardman

Remote regulation of type 2 immunity by intestinal parasites

The intestinal tract is the target organ of most parasitic infections, including those by helminths and protozoa. These parasites elicit prototypical type 2 immune activation in the host's immune system with striking impact on the local tissue microenvironment. Despite local containment of these parasites within the intestinal tract, parasitic infections also mediate immune adaptation in peripheral organs. In this review, we summarize the current knowledge on how such gut-tissue axes influence important immune-mediated resistance and disease tolerance in the context of coinfections, and elaborate on the implications of parasite-regulated gut-lung and gut-brain axes on the development and severity of airway inflammation and central nervous system diseases.

Protecting your gut feelings: How intestinal infections keep things moving

Neurons of the enteric nervous system (ENS) have limited regenerative capacity, and damage to these cells can cause neuropathies. In a recent issue of Cell, Ahrends et al. (2021) demonstrate that muscularis macrophages integrate distinct signals from diverse intestinal infections to protect ENS neurons from subsequent pathogenic insult.

Vasoactive intestinal peptide promotes host defense against enteric pathogens by modulating the recruitment of group 3 innate lymphoid cells

Group 3 innate lymphoid cells (ILC3s) control the formation of intestinal lymphoid tissues and play key roles in intestinal defense. They express neuropeptide vasoactive intestinal peptide (VIP) receptor 2 (VPAC2), through which VIP modulates their function, but whether VIP exerts other effects on ILC3 remains unclear. We show that VIP promotes ILC3 recruitment to the intestine through VPAC1 independent of the microbiota or adaptive immunity. VIP is also required for postnatal formation of lymphoid tissues as well as the maintenance of local populations of retinoic acid (RA)-producing dendritic cells, with RA up-regulating gut-homing receptor CCR9 expression by ILC3s. Correspondingly, mice deficient in VIP or VPAC1 suffer a paucity of intestinal ILC3s along with impaired production of the cytokine IL-22, rendering them highly susceptible to the enteric pathogen Citrobacter rodentium This heightened susceptibility to C. rodentium infection was ameliorated by RA supplementation, adoptive transfer of ILC3s, or by recombinant IL-22. Thus, VIP regulates the recruitment of intestinal ILC3s and formation of postnatal intestinal lymphoid tissues, offering protection against enteric pathogens.

Direct and indirect effects of microbiota-derived metabolites on neuroinflammation in multiple sclerosis

Multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) are highly influenced by changes in the microbiota and of microbiota-derived metabolites, including short chain fatty acids, bile acids, and tryptophan derivatives. This review will discuss the effects of microbiota-derived metabolites on neuroinflammation driven by central nervous system-resident cells and peripheral immune cells, and their influence on outcomes of EAE and MS.

Differential phenotypes and localization of CD8 T cell responses to acute and chronic viral infections

Norovirus is the most common viral cause of gastroenteritis globally. Most infections are either acute, symptomatic, and rapidly cleared or persist asymptomatically. However, the mechanisms underlying these outcomes are unknown. MNV-CW3 and -CR6 are murine noroviruses which demonstrate immune correlates of acute and chronic infection respectively. This research interrogates the mechanisms underlying strain-specific differential antiviral CD8 T cell responses to acute or chronic MNV. At days 3, 4, 5 and 8 post-infection, the phenotype and quantity of adoptively transferred MNV specific CD8 T cells in the spleen, mesenteric lymph node (MLN), and intestines are analyzed by flow cytometry. Concurrently, fluorescent microscopy is used to determine the biogeographical distribution of antiviral CD8 T cells throughout the intestine. Flow cytometry shows activated MNV-specific CD8 T cells first accumulate in the MLN following oral infection with either virus suggesting this is the site of immune activation though CR6 infection results in a delayed, reduced CD8 T cell response as shown by CFSE dilution. Supporting the MLN as a primary initiation site of the antiviral CD8 T cell response, prevention of T cell egress from activation sites by FTY720 treatment enriches activated CD8 T cells in the MLN in CW3 infections with a concurrent decrease in the spleen. Furthermore, by day 8 post-infection CD8 T cell populations are skewed to memory precursors or short-lived effectors in CW3 and CR6, respectively. These data suggest these highly related viral strains may induce activation of distinct populations of, or pathways in, APC populations with long-lasting effects on CD8 T cell function and the outcome of infection.

Helminth-induced modulation of neuroinflammation in a mouse model of multiple sclerosis

Environmental factors play an important role in multiple sclerosis (MS) disease progression, but the exact cause remains unknown. The hygiene hypothesis suggests that a lack of exposure to microbes may alter disease susceptibility. Helminths in particular may play a role in preventing autoimmune disease due to the type 2 immune response they typically induce. Trichinella spiralis (Ts) first forms a transient intestinal infection followed by chronic infection where it exerts type 2 and regulatory immune responses, respectively. To evaluate the role of helminth infection in development and progression of MS, C57BL/6J mice were first chronically infected with Ts, then immunized with MOG35–55 to induce experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. Ts-infected EAE mice have an altered disease course compared to uninfected controls, demonstrating delayed onset, reduced incidence, and symptom remission. Despite an overall decrease in lymphocyte recruitment to the central nervous system (CNS) in Ts/EAE mice, elevated numbers of infiltrating Th2 cells are maintained through the EAE disease course. In contrast, regulatory T cell expansion is dependent on the presence or absence of EAE symptoms. Histological analysis of cellular infiltration and demyelination in the spinal cord indicate limited demyelination with reduced infiltration into the parenchyma of Ts/EAE mice compared to EAE controls. Further immunophenotyping in the CNS to evaluate the contributions of infiltrating macrophages will be performed, as well as analyses of the cytokine milieu in the CNS. These results suggest that chronic Ts infection limits neuroinflammation, as shown by reduced clinical, immunological, and pathologic signs of EAE.

Insights into the role of Epstein-Barr virus infection in multiple sclerosis using a novel humanized mouse model of disease

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system without a clear cause. Epstein-Barr virus (EBV) is proposed to contribute to the pathogenesis of MS through unknown mechanisms. Evidence for a role of EBV infection in MS comes from both epidemiological and experimental studies, however, due to its narrow host tropism, there are currently few suitable animal models of MS that incorporate EBV infection. Recent advancements in humanized mouse modelling has enabled direct infection for the study of EBV-associated malignancies. We therefore chose to evaluate the role of EBV infection in humanized mice with experimental autoimmune encephalomyelitis (EAE), a widely used model of MS. Immunocompromised mice were engrafted with peripheral blood mononuclear cells (PBMC) derived from individuals with relapsing MS (RRMS) or from matched healthy EBV seropositive or seronegative donors. We observed that HuPBMC mice induced with EAE developed ascending paralysis, weight loss and signs of discomfort consistent with classical EAE models. Further, HuPBMC EAE showed significant T cell infiltration of both the brain and spinal cord, notably of IFN gamma-expressing CD4 and CD8 T cells, resulting in spinal cord and cerebellar demyelination. HuPBMC EAE mice derived from EBV seropositive donors developed earlier disease onset with more severe clinical symptoms compared to EBV seronegative donor-derived mice. We also observed increase disease severity among mice derived from RRMS patients compared to healthy controls. With continued improvement and characterization of this novel humanized EAE model, additional environmental and genetic risk factors can be evaluated in a system with human immune-mediated pathology.

STAT1-dependent tolerance of intestinal viral infection

The diverse commensal ecosystem present in the mammalian intestine requires the host immune system to maintain a tolerogenic environment. The virome is an understudied component of the microbiota which promotes intestinal homeostasis and protection from injury, but the host mechanisms that regulate tolerance to viral commensals are poorly described. The antiviral signal transducer STAT1 has previously been shown to mediate tolerance to systemic viral pathogens by suppressing adaptive immune responses and protecting the host from immunopathology, but we sought to characterize its role in the context of a commensal intestinal viral infection.

We used a persistent strain of murine norovirus (MNV CR6) to interrogate host mechanisms of viral tolerance and commensalism, as CR6 has previously been shown to promote intestinal homeostasis. While CR6 infections of wildtype mice were asymptomatic and limited to the colon, STAT1-deficient mice exhibited virus-induced weight loss and mortality accompanied by systemic viral spread, colonic bacterial dysbiosis, CD4+ T cell dysfunction and hyperaccumulation of CD8+ T cells. However, clinical manifestation of virus-induced disease in STAT1-deficient mice was independent of T cells and the bacterial microbiota. Instead, therapeutic control of viral replication was sufficient to prevent virus-induced disease despite ongoing T cell dysregulation. Collectively, our data indicate that STAT1 maintains tolerance to a viral component of the intestinal microbiota by control of viral replication rather than immunopathology, suggesting that STAT1 uses distinct strategies to tolerate pathogenic and commensal viruses.

Virus-mediated dysbiosis alters immune populations to promote type 1 diabetes onset

In combination with genetic determinants, susceptibility to autoimmune diseases such as Type 1 Diabetes (T1D) is established by various environmental factors including infection, microbial dysbiosis, antibiotic use, and vitamin D deficiency. Studies have implicated infection with certain viruses such as coxsackievirus B (CVB) to be an important cofactor associated with diabetes development and pathogenesis. Infections may be an instigating factor to alter the microbiome and this microbial change may be sufficient to skew immune populations and promote autoimmunity. Mucosa-associated invariant T (MAIT) cell populations have been shown to be altered leading up to diabetes onset in patients and mice. These cells are activated by microbial products in the gut to promote intestinal integrity, but they can also take on a more inflammatory phenotype and participate in autoimmune responses in the pancreas. Ultimately, there exists a significant potential for cross-talk between CVB infection, the microbiome, and gut-resident immune cells impacting T1D susceptibility. We have found CVB infection not only promotes onset of T1D in non-obese diabetic (NOD) mice but also causes dysbiosis which resembles that of a spontaneously diabetic NOD mouse. Introducing this new infection-induced microbial composition into naïve mice through the use of fecal microbiome transfers (FMTs) can accelerate T1D onset and alter immune profiles in the gut as well as the pancreas. Furthermore, MAIT populations are altered by this “diabetogenic” microbiome and also respond directly to CVB infection. Together our data highlights the role of virus infection and its ability to affect the gut microbiome and immune homeostasis to contribute to T1D development.

Perspectives of People with Multiple Sclerosis About Helminth Immunotherapy

Background

Due to the chronic and incurable nature of the autoimmune disease multiple sclerosis (MS), some people with MS will seek out alternative therapeutic approaches. Helminth immunotherapy, the deliberate inoculation with helminthic parasites as an intervention to prevent, delay, or minimize progression of autoimmune disorders, is one such approach gaining traction in academic research and with the public. Herein, we explored the perspectives of people with MS regarding helminth immunotherapy and its use in disease management.

Methods

Interpretive description, a qualitative research approach, was applied to data extracted from online forums. Multiple investigators independently identified, extracted, and analyzed data to develop preliminary codes. Inductive thematic analysis and triangulation were then used to collaboratively establish themes.

Results

Four main themes were generated: experience of living with MS, influential factors in contemplating helminth immunotherapy, logistics of helminth immunotherapy, and concerns about helminth immunotherapy.

Conclusions

There was a general consensus in publicly available online forums that conventional therapies do not provide meaningful improvement for some people with MS. These people may seek alternative therapies such as helminth immunotherapy. Information on helminth immunotherapy from internet resources (eg, blogs and social media forums) can contain biased and scientifically unsupported opinions. Messages of efficacy and improved quality of life are readily available and may influence people with MS considering helminth immunotherapy as an alternative therapy. Although some people with MS are seeking helminth immunotherapy, clinical trial data do not currently support its use for people with MS.

A262 DIFFERENTIAL PHENOTYPES AND LOCALIZATION OF CD8+ T CELL RESPONSES TO ACUTE AND CHRONIC ENTERIC VIRAL INFECTION

Background

Human Norovirus infection is the most common viral cause of gastroenteritis globally and the second most reported viral infection in Canada after the common cold. Most infections are acute, symptomatic, and rapidly cleared but some cases persist asymptomatically or induce post-infectious irritable bowel syndrome. Despite the global burden of these infections, no vaccine to prevent disease exists nor is the mechanism for persistence understood. MNV-CW3 and MNV-CR6 are murine noroviruses which demonstrate distinct biological behaviors that correlate with differential quantity and quality of antiviral CD8+ T cell responses. MNV-CW3 causes acute systemic infections initiated in the small intestine and cleared by day 8 due to a robust antiviral CD8+ T cell response. In contrast, MNV-CR6 causes chronic infections localized to the colonic intestinal epithelium and induces fewer antiviral CD8+ T cells with reduced effector molecule expression.

Aims

This research interrogates the mechanisms underlying strain-specific differential antiviral CD8+ T cell responses.

Methods

At days 3, 4, 5 and 8 post-infection, the phenotype and quantity of adoptively transferred MNV specific CD8+ T cells in the spleen, mesenteric lymph node (MLN), and the small and large intestine are analyzed by flow cytometry. Concurrently, immunofluorescent microscopy is used to determine whether CD8+ T cells are broadly disseminated throughout the intestines or localize in acute clusters of antiviral response. Combining these complementary techniques provides novel insight into mechanisms governing intestinal antiviral T cell responses.

Results

Activated MNV-specific CD8 T cells first accumulate in the MLN following oral infection with both MNV-CW3 and CR6, suggesting this is the site of immune activation. Supporting this hypothesis, preliminary data indicates that preventing T cell egress from activation sites by treatment with the S1PR1 agonist FTY720 leads to an enrichment of activated CD8+ T cells in the MLN following CW3 infection. Notably, the earliest stages of CD8+ T cell activation to CR6 infection is delayed compared to that elicited by CW3. Furthermore, at the peak of CD8+ T cell expansion (day 8 post-infection), CR6-elicited CD8+ T cells preferentially develop into short-lived effector populations rather than memory precursor populations.

Conclusions

These data reveal previously unknown differences in early events in CD8+ T cell activation following infection with two highly related viral strains that correlate with long-lasting effects on T cell differentiation and function. We are currently investigating the hypothesis that MNV-CW3 and CR6 may induce activation of distinct populations of, or pathways in, APC populations that would drive these differences. These results may have broad impacts on our understanding of how non-latent, chronic viral infections persist within a host.

Funding Agencies

CIHR

A critical analysis of helminth immunotherapy in multiple sclerosis

Helminthic worms are ancestral members of the intestinal ecosystem that have been largely eradicated from the general population in industrialized countries. Immunomodulatory mechanisms induced by some helminths mediate a “truce” between the mammalian host and the colonizing worm, thus allowing for long-term persistence in the absence of immune-mediated collateral tissue damage. This concept and the geographic discrepancy between global burdens of chronic inflammatory diseases and helminth infection have sparked interest in the potential of using helminthic worms as a therapeutic intervention to limit the progression of autoimmune diseases such as multiple sclerosis (MS). Here, we present and evaluate the evidence for this hypothesis in the pre-clinical animal model of MS, experimental autoimmune encephalitis, in helminth-infected MS patients and in clinical trials of administered helminth immunotherapy (HIT).

Recirculating Intestinal IgA-Producing Cells Regulate Neuroinflammation via IL-10

Plasma cells (PC) are found in the CNS of multiple sclerosis (MS) patients, yet their source and role in MS remains unclear. We find that some PC in the CNS of mice with experimental autoimmune encephalomyelitis (EAE) originate in the gut and produce immunoglobulin A (IgA). Moreover, we show that IgA⁺ PC are dramatically reduced in the gut during EAE, and likewise, a reduction in IgA-bound fecal bacteria is seen in MS patients during disease relapse. Removal of plasmablast (PB) plus PC resulted in exacerbated EAE that was normalized by the introduction of gut-derived IgA⁺ PC. Furthermore, mice with an over-abundance of IgA⁺ PB and/or PC were specifically resistant to the effector stage of EAE, and expression of interleukin (IL)-10 by PB plus PC was necessary and sufficient to confer resistance. Our data show that IgA⁺ PB and/or PC mobilized from the gut play an unexpected role in suppressing neuroinflammation.

The Multibiome: The Intestinal Ecosystem's Influence on Immune Homeostasis, Health, and Disease

Mammalian evolution has occurred in the presence of mutualistic, commensal, and pathogenic micro- and macro-organisms for millennia. The presence of these organisms during mammalian evolution has allowed for intimate crosstalk between these colonizing species and the host immune system. In this review, we introduce the concept of the ‘multibiome’ to holistically refer to the biodiverse collection of bacteria, viruses, fungi and multicellular helminthic worms colonizing the mammalian intestine. Furthermore, we discuss new insights into multibiome-host interactions in the context of host-protective immunity and immune-mediated diseases, including inflammatory bowel disease and multiple sclerosis. Finally, we provide reasons to account for the multibiome in experimental design, analysis and in therapeutic applications.

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The intestinal multibiome is composed of bacteria, viruses, fungi, and eukaryotes.

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Mammals evolved alongside a complex and biodiverse multibiome.

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Cross-talk between the multibiome and the host regulates immunity and inflammation.

Type I Interferon Receptor Deficiency in Dendritic Cells Facilitates Systemic Murine Norovirus Persistence Despite Enhanced Adaptive Immunity

In order for a virus to persist, there must be a balance between viral replication and immune clearance. It is commonly believed that adaptive immunity drives clearance of viral infections and, thus, dysfunction or viral evasion of adaptive immunity is required for a virus to persist. Type I interferons (IFNs) play pleiotropic roles in the antiviral response, including through innate control of viral replication. Murine norovirus (MNoV) replicates in dendritic cells (DCs) and type I IFN signaling in DCs is important for early control of MNoV replication. We show here that the non-persistent MNoV strain CW3 persists systemically when CD11c positive DCs are unable to respond to type I IFN. Persistence in this setting is associated with increased early viral titers, maintenance of DC numbers, increased expression of DC activation markers and an increase in CD8 T cell and antibody responses. Furthermore, CD8 T cell function is maintained during the persistent phase of infection and adaptive immune cells from persistently infected mice are functional when transferred to Rag1-/- recipients. Finally, increased early replication and persistence are also observed in mixed bone marrow chimeras where only half of the CD11c positive DCs are unable to respond to type I IFN. These findings demonstrate that increased early viral replication due to a cell-intrinsic innate immune deficiency is sufficient for persistence and a functional adaptive immune response is not sufficient for viral clearance.

Tuft cells, taste-chemosensory cells, orchestrate parasite type 2 immunity in the gut

The intestinal epithelium forms an essential barrier between a host and its microbiota. Protozoa and helminths are members of the gut microbiota of mammals, including humans, yet the many ways that gut epithelial cells orchestrate responses to these eukaryotes remain unclear. Here we show that tuft cells, which are taste-chemosensory epithelial cells, accumulate during parasite colonization and infection. Disruption of chemosensory signaling through the loss of TRMP5 abrogates the expansion of tuft cells, goblet cells, eosinophils, and type 2 innate lymphoid cells during parasite colonization. Tuft cells are the primary source of the parasite-induced cytokine interleukin-25, which indirectly induces tuft cell expansion by promoting interleukin-13 production by innate lymphoid cells. Our results identify intestinal tuft cells as critical sentinels in the gut epithelium that promote type 2 immunity in response to intestinal parasites.

TLR-7 activation enhances IL-22-mediated colonization resistance against vancomycin-resistant enterococcus

Antibiotic administration can disrupt the intestinal microbiota and down-regulate innate immune defenses, compromising colonization resistance against orally acquired bacterial pathogens. Vancomycin-resistant Enterococcus faecium (VRE), a major cause of antibiotic-resistant infections in hospitalized patients, thrives in the intestine when colonization resistance is compromised, achieving extremely high densities that can lead to bloodstream invasion and sepsis. Viral infections, by mechanisms that remain incompletely defined, can stimulate resistance against invading bacterial pathogens. We report that murine norovirus infection correlates with reduced density of VRE in the intestinal tract of mice with antibiotic-induced loss of colonization resistance. Resiquimod (R848), a synthetic ligand for Toll-like receptor 7 (TLR-7) that stimulates antiviral innate immune defenses, restores expression of the antimicrobial peptide Reg3γ and reestablishes colonization resistance against VRE in antibiotic-treated mice. Orally administered R848 triggers TLR-7 on CD11c(+) dendritic cells, inducing interleukin-23 (IL-23) expression followed by a burst of IL-22 secretion by innate lymphoid cells, leading to Reg3γ expression and restoration of colonization resistance against VRE. Our findings reveal that an orally bioavailable TLR-7 ligand that stimulates innate antiviral immune pathways in the intestine restores colonization resistance against a highly antibiotic-resistant bacterial pathogen.

The prostaglandin D₂ receptor CRTH2 regulates accumulation of group 2 innate lymphoid cells in the inflamed lung

Group 2 innate lymphoid cells (ILC2s) promote type 2 cytokine-dependent immunity, inflammation, and tissue repair. Although epithelial cell-derived cytokines regulate ILC2 effector functions, the pathways that control the in vivo migration of ILC2s into inflamed tissues remain poorly understood. Here, we provide the first demonstration that expression of the prostaglandin D2 (PGD2) receptor CRTH2 (chemoattractant receptor-homologous molecule expressed on Th2 cells) regulates the in vivo accumulation of ILC2s in the lung. Although a significant proportion of ILC2s isolated from healthy human peripheral blood expressed CRTH2, a smaller proportion of ILC2s isolated from nondiseased human lung expressed CRTH2, suggesting that dynamic regulation of CRTH2 expression might be associated with the migration of ILC2s into tissues. Consistent with this, murine ILC2s expressed CRTH2, migrated toward PGD2 in vitro, and accumulated in the lung in response to PGD2 in vivo. Furthermore, mice deficient in CRTH2 exhibited reduced ILC2 responses and inflammation in a murine model of helminth-induced pulmonary type 2 inflammation. Critically, adoptive transfer of CRTH2-sufficient ILC2s restored pulmonary inflammation in CRTH2-deficient mice. Together, these data identify a role for the PGD2-CRTH2 pathway in regulating the in vivo accumulation of ILC2s and the development of type 2 inflammation in the lung.

Epithelial-intrinsic IKKα expression regulates group 3 innate lymphoid cell responses and antibacterial immunity

Innate lymphoid cells (ILCs) are critical for maintaining epithelial barrier integrity at mucosal surfaces; however, the tissue-specific factors that regulate ILC responses remain poorly characterized. Using mice with intestinal epithelial cell (IEC)-specific deletions in either inhibitor of κB kinase (IKK)α or IKKβ, two critical regulators of NFκB activation, we demonstrate that IEC-intrinsic IKKα expression selectively regulates group 3 ILC (ILC3)-dependent antibacterial immunity in the intestine. Although IKKβ(ΔIEC) mice efficiently controlled Citrobacter rodentium infection, IKKα(ΔIEC) mice exhibited severe intestinal inflammation, increased bacterial dissemination to peripheral organs, and increased host mortality. Consistent with weakened innate immunity to C. rodentium, IKKα(ΔIEC) mice displayed impaired IL-22 production by RORγt(+) ILC3s, and therapeutic delivery of rIL-22 or transfer of sort-purified IL-22-competent ILCs from control mice could protect IKKα(ΔIEC) mice from C. rodentium-induced morbidity. Defective ILC3 responses in IKKα(ΔIEC) mice were associated with overproduction of thymic stromal lymphopoietin (TSLP) by IECs, which negatively regulated IL-22 production by ILC3s and impaired innate immunity to C. rodentium. IEC-intrinsic IKKα expression was similarly critical for regulation of intestinal inflammation after chemically induced intestinal damage and colitis. Collectively, these data identify a previously unrecognized role for epithelial cell-intrinsic IKKα expression and TSLP in regulating ILC3 responses required to maintain intestinal barrier immunity.

Emerging functions of amphiregulin in orchestrating immunity, inflammation, and tissue repair

Type 2 inflammatory responses can be elicited by diverse stimuli, including toxins, venoms, allergens, and infectious agents, and play critical roles in resistance and tolerance associated with infection, wound healing, tissue repair, and tumor development. Emerging data suggest that in addition to characteristic type 2-associated cytokines, the epidermal growth factor (EGF)-like molecule Amphiregulin (AREG) might be a critical component of type 2-mediated resistance and tolerance. Notably, numerous studies demonstrate that in addition to the established role of epithelial- and mesenchymal-derived AREG, multiple leukocyte populations including mast cells, basophils, group 2 innate lymphoid cells (ILC2s), and a subset of tissue-resident regulatory CD4(+) T cells can express AREG. In this review, we discuss recent advances in our understanding of the AREG-EGF receptor pathway and its involvement in infection and inflammation and propose a model for the function of this pathway in the context of resistance and tissue tolerance.

Constant replenishment from circulating monocytes maintains the macrophage pool in the intestine of adult mice

The paradigm that macrophages that reside in steady-state tissues are derived from embryonic precursors has never been investigated in the intestine, which contains the largest pool of macrophages. Using fate-mapping models and monocytopenic mice, together with bone marrow chimera and parabiotic models, we found that embryonic precursor cells seeded the intestinal mucosa and demonstrated extensive in situ proliferation during the neonatal period. However, these cells did not persist in the intestine of adult mice. Instead, they were replaced around the time of weaning by the chemokine receptor CCR2-dependent influx of Ly6C(hi) monocytes that differentiated locally into mature, anti-inflammatory macrophages. This process was driven largely by the microbiota and had to be continued throughout adult life to maintain a normal intestinal macrophage pool.

Oral-resident natural Th17 cells and γδ T cells control opportunistic Candida albicans infections

Conti et al. show that IL-17 is produced by tongue-resident populations of γδ T cells and nTh17 cells in response to oropharyngeal candidiasis in mice.

Oropharyngeal candidiasis (OPC) is an opportunistic fungal infection caused by Candida albicans. OPC is frequent in HIV/AIDS, implicating adaptive immunity. Mice are naive to Candida, yet IL-17 is induced within 24 h of infection, and susceptibility is strongly dependent on IL-17R signaling. We sought to identify the source of IL-17 during the early innate response to candidiasis. We show that innate responses to Candida require an intact TCR, as SCID, IL-7Rα^−/−, and Rag1^−/− mice were susceptible to OPC, and blockade of TCR signaling by cyclosporine induced susceptibility. Using fate-tracking IL-17 reporter mice, we found that IL-17 is produced within 1–2 d by tongue-resident populations of γδ T cells and CD3⁺CD4⁺CD44^hiTCRβ⁺CCR6⁺ natural Th17 (nTh17) cells, but not by TCR-deficient innate lymphoid cells (ILCs) or NK cells. These cells function redundantly, as TCR-β^−/− and TCR-δ^−/− mice were both resistant to OPC. Whereas γδ T cells were previously shown to produce IL-17 during dermal candidiasis and are known to mediate host defense at mucosal surfaces, nTh17 cells are poorly understood. The oral nTh17 population expanded rapidly after OPC, exhibited high TCR-β clonal diversity, and was absent in Rag1^−/−, IL-7Rα^−/−, and germ-free mice. These findings indicate that nTh17 and γδ T cells, but not ILCs, are key mucosal sentinels that control oral pathogens.

Coinfection. Virus-helminth coinfection reveals a microbiota-independent mechanism of immunomodulation

The mammalian intestine is colonized by beneficial commensal bacteria and is a site of infection by pathogens, including helminth parasites. Helminths induce potent immunomodulatory effects, but whether these effects are mediated by direct regulation of host immunity or indirectly through eliciting changes in the microbiota is unknown. We tested this in the context of virus-helminth coinfection. Helminth coinfection resulted in impaired antiviral immunity and was associated with changes in the microbiota and STAT6-dependent helminth-induced alternative activation of macrophages. Notably, helminth-induced impairment of antiviral immunity was evident in germ-free mice, but neutralization of Ym1, a chitinase-like molecule that is associated with alternatively activated macrophages, could partially restore antiviral immunity. These data indicate that helminth-induced immunomodulation occurs independently of changes in the microbiota but is dependent on Ym1.

Pneumolysin expression by streptococcus pneumoniae protects colonized mice from influenza virus-induced disease

The response to influenza virus (IAV) infection and severity of disease is highly variable in humans. We hypothesized that one factor contributing to this variability is the presence of specific respiratory tract (RT) microbes. One such microbe is Streptococcus pneumoniae (Sp) that is carried asymptomatically in the RT of many humans. In a mouse co-infection model we found that in contrast to secondary bacterial infection that exacerbates disease, Sp colonization 10 days prior to IAV protects from virus-induced morbidity and lung pathology. Using mutant Sp strains, we identified a critical role for the bacterial virulence factor pneumolysin (PLY) in mediating this protection. Colonization with the PLY-sufficient Sp strain induces expression of the immune-suppressive enzyme arginase 1 in alveolar macrophages (aMø) and correlates with attenuated recruitment and function of pulmonary inflammatory cells. Our study demonstrates a novel role for PLY in Sp-mediated protection by maintaining aMø as "gatekeepers" against virus-induced immunopathology.

Polarizing the T helper 17 response in Citrobacter rodentium infection via expression of resistin-like molecule α

Citrobacter rodentium infection is a murine model of pathogenic Escherichia coli infection that allows investigation of the cellular and molecular mechanisms involved in host-protective immunity and bacterial-induced intestinal inflammation. We recently demonstrated that following C. rodentium infection, the absence of Resistin-Like Molecule (RELM) α resulted in attenuated Th17 cell responses and reduced intestinal inflammation with minimal effects on bacterial clearance. In this addendum, we investigated the cytokine modulatory effects of RELMα and RELMα expression in the intestinal mucosa following C. rodentium infection. We show that in addition to promoting Th17 cytokine responses, RELMα inhibits Th2 cytokine expression and Th2-cytokine effector macrophage responses in the C. rodentium-infected colons. Second, utilizing reporter C. rodentium, we examined RELMα expression and macrophage recruitment at the host pathogen interface. We observed infection-induced macrophage infiltration and RELMα expression by intestinal epithelial cells. The influence of infection-induced RELMα on macrophage recruitment in the intestine is discussed.

Thymic stromal lymphopoietin-mediated extramedullary hematopoiesis promotes allergic inflammation

Extramedullary hematopoiesis (EMH) refers to the differentiation of hematopoietic stem cells (HSCs) into effector cells that occurs in compartments outside of the bone marrow. Previous studies linked pattern-recognition receptor (PRR)-expressing HSCs, EMH, and immune responses to microbial stimuli. However, whether EMH operates in broader immune contexts remains unknown. Here, we demonstrate a previously unrecognized role for thymic stromal lymphopoietin (TSLP) in promoting the population expansion of progenitor cells in the periphery and identify that TSLP-elicited progenitors differentiated into effector cells including macrophages, dendritic cells, and granulocytes and that these cells contributed to type 2 cytokine responses. The frequency of circulating progenitor cells was also increased in allergic patients with a gain-of-function polymorphism in TSLP, suggesting the TSLP-EMH pathway might operate in human disease. These data identify that TSLP-induced EMH contributes to the development of allergic inflammation and indicate that EMH is a conserved mechanism of innate immunity.

The development and survival but not function of follicular B cells is dependent on IL-7Rα Tyr449 signaling

IL-7 is a critical cytokine for lymphocyte development. Recent work has highlighted critical roles for IL-7 signaling in mature T cell homeostasis and function, but its role in B cells is less well characterized. Using a knock-in mouse possessing a Tyr to Phe mutation at position 449 (IL-7Rα(449F/449F) mice) within the cytoplasmic SH2-binding motif of IL-7Rα, we evaluated the role of IL-7Rα Y449 motif in spleen B cells. IL-7Rα(449F/449F) mice had reduced numbers and increased death of follicular B cells compared to WT, but had significantly more follicular cells than IL-7Rα(-/-). The death of IL-7Rα(449F/449F) follicular cells was not due to a failure to respond to BAFF or lower levels of BAFF, a critical B cell survival factor. Marginal zone B cells were unaffected by the IL-7Rα(449F/449F) mutation. Any role for TSLP was ruled out, as TSLPR(-/-) mice had an identical B cell phenotype to wild-type mice. Bone marrow chimeras and the absence of IL-7Rα on B cells suggested that IL-7 did not directly regulate mature B cells, but that an IL-7-responsive cell was influencing B cells. IL-7 was also critical at the checkpoint between the T1 and T2 stages in the spleen. IL-7Rα(-/-) mice fail to develop T2 cells, but IL-7Rα(449F/449F) show a reduction compared to WT but not complete absence of T2 cells. We also tested the functional responses of IL-7Rα(449F/449F) to antigens and infection and found no difference in antibody responses to T-dependent or T-independent antigens, or to Influenza/A. IL-7 was important for generation of antibody responses to the intestinal worm H. polygyrus and for naive levels of IgA. Taken together, this suggests that IL-7 regulates follicular B cell numbers and survival in a cell-extrinsic manner, via a bone-marrow derived cell, but is not critical for antibody production outside the gut.

Resistin-like molecule α promotes pathogenic Th17 cell responses and bacterial-induced intestinal inflammation

Resistin-like molecule (RELM)α belongs to a family of secreted mammalian proteins that have putative immunomodulatory functions. Recent studies have identified a pathogenic role for RELMα in chemically induced colitis through effects on innate cell populations. However, whether RELMα regulates intestinal adaptive immunity to enteric pathogens is unknown. In this study, we employed Citrobacter rodentium as a physiologic model of pathogenic Escherichia coli-induced diarrheal disease, colitis, and Th17 cell responses. In response to Citrobacter, RELMα expression was induced in intestinal epithelial cells, infiltrating macrophages, and eosinophils of the infected colons. Citrobacter-infected RELMα(-/-) mice exhibited reduced infection-induced intestinal inflammation, characterized by decreased leukocyte recruitment to the colons and reduced immune cell activation compared with wild-type (WT) mice. Interestingly, Citrobacter colonization and clearance were unaffected in RELMα(-/-) mice, suggesting that the immune stimulatory effects of RELMα following Citrobacter infection were pathologic rather than host-protective. Furthermore, infected RELMα(-/-) mice exhibited decreased CD4(+) T cell expression of the proinflammatory cytokine IL-17A. To directly test whether RELMα promoted Citrobacter-induced intestinal inflammation via IL-17A, infected WT and IL-17A(-/-) mice were treated with rRELMα. RELMα treatment of Citrobacter-infected WT mice exacerbated intestinal inflammation and IL-17A expression whereas IL-17A(-/-) mice were protected from RELMα-induced intestinal inflammation. Finally, infected RELMα(-/-) mice exhibited reduced levels of serum IL-23p19 compared with WT mice, and RELMα(-/-) peritoneal macrophages showed deficient IL-23p19 induction. Taken together, these data identify a proinflammatory role for RELMα in bacterial-induced colitis and suggest that the IL-23/Th17 axis is a critical mediator of RELMα-induced inflammation.

Commensal bacteria calibrate the activation threshold of innate antiviral immunity

Signals from commensal bacteria can influence immune cell development and susceptibility to infectious or inflammatory diseases. However, the mechanisms by which commensal bacteria regulate protective immunity after exposure to systemic pathogens remain poorly understood. Here, we demonstrate that antibiotic-treated (ABX) mice exhibit impaired innate and adaptive antiviral immune responses and substantially delayed viral clearance after exposure to systemic LCMV or mucosal influenza virus. Furthermore, ABX mice exhibited severe bronchiole epithelial degeneration and increased host mortality after influenza virus infection. Genome-wide transcriptional profiling of macrophages isolated from ABX mice revealed decreased expression of genes associated with antiviral immunity. Moreover, macrophages from ABX mice exhibited defective responses to type I and type II IFNs and impaired capacity to limit viral replication. Collectively, these data indicate that commensal-derived signals provide tonic immune stimulation that establishes the activation threshold of the innate immune system required for optimal antiviral immunity.

Proteomics Analysis of Interleukin (IL)-7-induced Signaling Effectors Shows Selective Changes in IL-7Rα449F Knock-in T Cell Progenitors

Interleukin (IL)-7 is a cytokine that plays a central role in the development, survival, and proliferation of T and B cell lymphocytes. Overexpression of IL-7 in mice (transgenic (Tg) IL-7) leads to both increased proliferation of early T and B cell progenitors and T and B cell lymphomas. Genetic evidence indicates that known IL-7 receptor (IL-7R)-dependent proteins, including prosurvival protein BCL-2, may not be solely responsible for the effects of IL-7. Other studies indicate that known IL-7-induced signaling proteins dock to a specific tyrosine (Tyr(449)) residue on the alpha-subunit of the IL-7R. We have previously shown in an IL-7Ralpha(449F) knock-in model that IL-7-induced lymphomas require Tyr(449) phosphorylation and that loss of this phosphorylation confers protection from disease. However, the mechanism by which this lymphoma protection occurs remains unclear. Using this genetic model, we aimed to identify novel prosurvival factors important for IL-7-mediated lymphocyte development and lymphomagenesis. An iTRAQ (isobaric tags for relative and absolute quantitation) proteomics analysis was performed comparing CD4(-)CD8(-) double negative T cell progenitors from mice overexpressing IL-7 (Tg IL-7) (lymphoma-prone) with Tg IL-7 mice with a mutated IL-7 receptor (Tg IL-7/IL-7Ralpha(449F)) (lymphoma-protected). Several proteins involved in survival, proliferation, and apoptosis were found to be differentially expressed between the two samples, and three proteins of particular interest, GIMAP4, BIT1, and FKBP51, were validated by immunoblot analysis.

Impaired T cell function and CD8 memory maintenance in a novel IL-7Rα knock-in mouse (B30)

Interleukin (IL)-7 is an essential growth factor for thymocyte development and survival of peripheral T cells, specifically CD8+ memory T cells. Current models such as IL-7 or IL-7 receptor alpha (IL-7Rα) knock-out mice have demonstrated the necessity of IL-7 signaling in these processes, but are unable to delineate the involvement of downstream pathways. To more precisely identify signals governing IL-7 function in vivo, we have disrupted the IL-7Rα Y449XXM motif in mice by knock-in mutagenesis (IL-7Rα449F). Thymocytes from these mice overcome a double negative (DN) stage developmental block that allows subsequent T cell maturation and peripheral migration. This is in stark contrast to the severe cytopenia seen in IL-7Rα−/− mice. These findings highlight the importance of IL-7Rα Y449-mediated signals during thymopoiesis, but also indicate a requirement for Y449-independent signals. Infection of IL-7Rα449F mice with the intracellular pathogen Listeria monocytogenes revealed that CD4 and CD8 T cells had different requirements for IL-7Rα signals. Strikingly, CD4 T cells failed to mount a detectable primary response to Listeria. Despite normal CD8 primary responses, maintenance of Listeria-specific CD8 memory was impaired in IL-7Rα449F mice. Furthermore, we show that Bcl-2 is IL-7Rα Y449-independent and insufficient for IL-7-mediated maintenance of CD8 memory.

Research funded by the Canadian Institutes of Health Research and the Michael Smith Foundation for Health Research

Impaired CD8 T cell memory and CD4 T cell primary responses in IL-7R alpha mutant mice

Loss of interleukin (IL)-7 or the IL-7 receptor alpha (IL-7Ralpha, CD127) results in severe immunodeficiencies in mice and humans. To more precisely identify signals governing IL-7 function in vivo, we have disrupted the IL-7Ralpha Y449XXM motif in mice by knock-in mutagenesis (IL-7Ralpha(449F)). Thymic precursors were reduced in number in IL-7Ralpha(449F) mice, but in marked contrast to IL-7Ralpha(-/-) knockout mice, thymocytes and peripheral T cells developed normally. Strikingly, Listeria infection revealed that CD4 and CD8 T cells had different requirements for IL-7Ralpha signals. CD4 T cells failed to mount a primary response, but despite normal CD8 primary responses, maintenance of CD8 memory was impaired in IL-7Ralpha(449F) mice. Furthermore, we show that Bcl-2 is IL-7Ralpha Y449 independent and insufficient for IL-7-mediated maintenance of CD8 memory.

HLA-A/B haplotye frequencies among U.S. Hispanic and African-American populations

HLA-A/B haplotype frequency tables were developed for U.S. Hispanic and African-American populations from data collected from paternity cases. Two Hispanic tables were developed; one was based on data from Hispanics in the northeast U.S. and Florida and designated the Caribbean table whilte all other Hispanics were included in a table designated the Mexican table. The total number of individuals whose haplotypes were included in the Caribbean, Mexican, African-American tables was 1635, 2230, and 3134, respectively. Statistical comparisons were made of haplotype frequencies among these tables and tables previously reported.

Effects of a strong and a weak carcinogen on murine alpha/beta interferon production in vivo

A study was designed to determine whether oral doses of carcinogens would reduce an animal's ability to produce interferon. Female BCF1 mice were tested with various doses of benzo[alpha]pyrene (BP) or ethyl methanesulfonate (EMS) po (four to six mice per treatment) and challenged an hour later with the chemical interferon inducer tilorone. After 16-18 hr, mice were sacrificed and bled from the heart. Serum obtained from the blood was assayed for interferon. We found that mice treated with as little as 50 mg/kg BP or EMS had a statistically significant reduction in serum interferon titers compared with control-treated mice. Reductions in interferon titers were also noted at lower doses of the carcinogens, but due to the variability within the small sample size used, the reduction were not statistically significant. On a molar basis, BP was only two to three times more effective at reducing interferon titers than EMS. It was estimated from the data that slightly less than 10 mg/kg BP or 29 mg/kg EMS would be the doses corresponding to 50% reduction in control interferon titers. These doses are well below the reported mutations doses for these chemicals. The effect of carcinogens on in vivo interferon production reported here may be the most sensitive biologic system known for these chemicals.

Reduction in antiviral activity of human beta interferon by gallic acid

Gallic acid (GA) is a common part of the human diet, both in the free form and as a metabolite of tannic acid and propyl gallate. Cell cultures were incubated with mixtures of either GA and beta interferon (IFN-beta) (formerly fibroblast IFN) or medium and IFN-beta. The cells were subsequently challenged with virus. The virus plaque yields were greater in cells incubated with IFN-beta and GA than in cells incubated with IFN-beta and medium, indicating that in the former mixture, IFN-beta had lost antiviral activity. The magnitude of the loss was dependent upon the GA concentration. IFN-alpha and IFN-gamma (formerly leukocyte IFN and immune IFN, respectively) were not similarly affected. The effect of GA on IFN-beta could be reversed with 2-mercaptoethanol, suggesting a possible sulfhydryl involvement. Extensive dialysis of IFN-beta-GA mixtures to remove the GA failed to reverse the reduction in antiviral activity. This suggests that a direct and irreversible interaction between IFN-beta and GA took place, reducing the activity of IFN-beta. The significance of this finding with regard to virus infections of the intestine is discussed.