Polyanhydride nanovaccine against H3N2 influenza A virus generates mucosal resident and systemic immunity promoting protection.

Influenza A virus (IAV) causes significant morbidity and mortality worldwide due to seasonal epidemics and periodic pandemics. The antigenic drift/shift of IAV continually gives rise to new strains and subtypes, aiding IAV in circumventing previously established immunity. As a result, there has been substantial interest in developing a broadly protective IAV vaccine that induces, durable immunity against multiple IAVs. Previously, a polyanhydride nanoparticle-based vaccine or nanovaccine (IAV-nanovax) encapsulating H1N1 IAV antigens was reported, which induced pulmonary B and T cell immunity and resulted in cross-strain protection against IAV. A key feature of IAV-nanovax is its ability to easily incorporate diverse proteins/payloads, potentially increasing its ability to provide broad protection against IAV and/or other pathogens. Due to human susceptibility to both H1N1 and H3N2 IAV, several H3N2 nanovaccines were formulated herein with multiple IAV antigens to examine the "plug-and-play" nature of the polyanhydride nanovaccine platform and determine their ability to induce humoral and cellular immunity and broad-based protection similar to IAV-nanovax. The H3N2-based IAV nanovaccine formulations induced systemic and mucosal B cell responses which were associated with antigen-specific antibodies. Additionally, systemic and lung-tissue resident CD4 and CD8 T cell responses were enhanced post-vaccination. These immune responses corresponded with protection against both homologous and heterosubtypic IAV infection. Overall, these results demonstrate the plug-and-play nature of the polyanhydride nanovaccine platform and its ability to generate immunity and protection against IAV utilizing diverse antigenic payloads.

HECT E3 Ubiquitin Ligase Nedd4 Is Required for Antifungal Innate Immunity.

Candida albicans is the most common cause of fungal infections in humans, and disseminated candidiasis has become one of the leading causes of hospital-acquired bloodstream infections with a high mortality rate. However, little is known about the host-pathogen interactions and the mechanisms of antifungal immunity. Here, we report that Nedd4 (neuronal precursor cell-expressed developmentally downregulated 4) is essential for signaling through Dectin-1 and Dectin-2/3. We showed that mice that lack Nedd4 globally or only in the myeloid compartment are highly susceptible to systemic C. albicans infection, which correlates with heightened organ fungal burden, defective inflammatory response, impaired leukocyte recruitment to the kidneys, and defective reactive oxygen species expression by granulocytes. At the molecular level, Nedd4 -/- macrophages displayed impaired activation of TGF-ß-activating kinase-1 and NF-κB, but normal activation of spleen tyrosine kinase and protein kinase C-δ on C. albicans yeast and hyphal infections. These data suggest that Nedd4 regulates signaling events downstream of protein kinase C-δ but upstream of or at TGF-ß-activating kinase-1.

Coactivation of NF-κB and Notch signaling is sufficient to induce B-cell transformation and enables B-myeloid conversion.

NF-κB and Notch signaling can be simultaneously activated in a variety of B-cell lymphomas. Patients with B-cell lymphoma occasionally develop clonally related myeloid tumors with poor prognosis. Whether concurrent activation of both pathways is sufficient to induce B-cell transformation and whether the signaling initiates B-myeloid conversion in a pathological context are largely unknown. Here, we provide genetic evidence that concurrent activation of NF-κB and Notch signaling in committed B cells is sufficient to induce B-cell lymphomatous transformation and primes common progenitor cells to convert to myeloid lineage through dedifferentiation, not transdifferentiation. Intriguingly, the converted myeloid cells can further transform, albeit at low frequency, into myeloid leukemia. Mechanistically, coactivation of NF-κB and Notch signaling endows committed B cells with the ability to self renew. Downregulation of BACH2, a lymphoma and myeloid gene suppressor, but not upregulation of CEBPα and/or downregulation of B-cell transcription factors, is an early event in both B-cell transformation and myeloid conversion. Interestingly, a DNA hypomethylating drug not only effectively eliminated the converted myeloid leukemia cells, but also restored the expression of green fluorescent protein, which had been lost in converted myeloid leukemia cells. Collectively, our results suggest that targeting NF-κB and Notch signaling will not only improve lymphoma treatment, but also prevent the lymphoma-to-myeloid tumor conversion. Importantly, DNA hypomethylating drugs might efficiently treat these converted myeloid neoplasms.

Polymicrobial Sepsis Chronic Immunoparalysis Is Defined by Diminished Ag-Specific T Cell-Dependent B Cell Responses.

Immunosuppression is one hallmark of sepsis, decreasing the host response to the primary septic pathogens and/or secondary nosocomial infections. CD4 T cells and B cells are among the array of immune cells that experience reductions in number and function during sepsis. "Help" from follicular helper (Tfh) CD4 T cells to B cells is needed for productive and protective humoral immunity, but there is a paucity of data defining the effect of sepsis on a primary CD4 T cell-dependent B cell response. Using the cecal ligation and puncture (CLP) mouse model of sepsis induction, we observed reduced antibody production in mice challenged with influenza A virus or TNP-KLH in alum early (2 days) and late (30 days) after CLP surgery compared to mice subjected to sham surgery. To better understand how these CD4 T cell-dependent B cell responses were altered by a septic event, we immunized mice with a Complete Freund's Adjuvant emulsion containing the MHC II-restricted peptide 2W1S56-68 coupled to the fluorochrome phycoerythrin (PE). Immunization with 2W1S-PE/CFA results in T cell-dependent B cell activation, giving us the ability to track defined populations of antigen-specific CD4 T cells and B cells responding to the same immunogen in the same mouse. Compared to sham mice, differentiation and class switching in PE-specific B cells were blunted in mice subjected to CLP surgery. Similarly, mice subjected to CLP had reduced expansion of 2W1S-specific T cells and Tfh differentiation after immunization. Our data suggest CLP-induced sepsis impacts humoral immunity by affecting the number and function of both antigen-specific B cells and CD4 Tfh cells, further defining the period of chronic immunoparalysis after sepsis induction.

Polyanhydride Nanovaccine Induces Robust Pulmonary B and T Cell Immunity and Confers Protection Against Homologous and Heterologous Influenza A Virus Infections.

Influenza A virus (IAV) is a major cause of respiratory illness. Given the disease severity, associated economic costs, and recent appearance of novel IAV strains, there is a renewed interest in developing novel and efficacious "universal" IAV vaccination strategies. Recent studies have highlighted that immunizations capable of generating local (i.e., nasal mucosa and lung) tissue-resident memory T and B cells in addition to systemic immunity offer the greatest protection against future IAV encounters. Current IAV vaccines are designed to largely stimulate IAV-specific antibodies, but do not generate the lung-resident memory T and B cells induced during IAV infections. Herein, we report on an intranasally administered biocompatible polyanhydride nanoparticle-based IAV vaccine (IAV-nanovax) capable of providing protection against subsequent homologous and heterologous IAV infections in both inbred and outbred populations. Our findings also demonstrate that vaccination with IAV-nanovax promotes the induction of germinal center B cells within the lungs, both systemic and lung local IAV-specific antibodies, and IAV-specific lung-resident memory CD4 and CD8 T cells. Altogether our findings show that an intranasally administered nanovaccine can induce immunity within the lungs, similar to what occurs during IAV infections, and thus could prove useful as a strategy for providing "universal" protection against IAV.

Polyanhydride Nanovaccines Induce Germinal Center B Cell Formation and Sustained Serum Antibody Responses.

Biodegradable polymeric nanoparticle-based subunit vaccines have shown promising characteristics by enhancing antigen presentation and inducing protective immune responses when compared with soluble protein. Specifically, polyanhydride nanoparticle-based vaccines (i.e., nanovaccines) have been shown to successfully encapsulate and release antigens, activate B and T cells, and induce both antibody- and cell-mediated immunity towards a variety of immunogens. One of the characteristics of strong thymus-dependent antibody responses is the formation of germinal centers (GC) and the generation of GC B cells, which is part of the T helper cell driven cellular response. In order to further understand the role of nanovaccines in the induction of antigen-specific immune responses, their ability to induce germinal center B cell formation and isotype switching and the effects thereof on serum antibody responses were investigated in these studies. Polyanhydride nanovaccines based on 1,6-bis(p-carboxyphenoxy)hexane and 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane were used to subcutaneously administer a viral antigen. GC B cell formation and serum antibody responses induced by the nanovaccines were compared to that induced by alum-based vaccine formulations. It was demonstrated that a single dose of polyanhydride nanovaccines resulted in the formation of robust GCs and serum antibody in comparison to that induced by the alum-based formulation. This was attributed to the sustained release of antigen provided by the nanovaccines. When administered in a multiple dose regimen, the highest post-immunization titer and GC B cell number was enhanced, and the immune response induced by the nanovaccines was further sustained. These studies provide foundational information on the mechanism of action of polyanhydride nanovaccines.

Regulatory IgDhi B Cells Suppress T Cell Function via IL-10 and PD-L1 during Progressive Visceral Leishmaniasis.

During visceral leishmaniasis (VL), Th1-based inflammation is induced to control intracellular parasites. Inflammation-based pathology was shown to be dampened by IL-10 and eventual programmed death 1-mediated T cell exhaustion. Cell type(s) responsible for the initiation of T cell-produced IL-10 during VL are unknown. CD19(+), CD5(-), CD1d(-), IgD(hi) regulatory B cells from healthy controls produced IL-10 in the absence of infection or stimulation, in contrast to IgD(lo/neg) B cells. IgD(hi) B cells may have a de novo versus induced regulatory program. The population of IgD(hi) B cells increased 3-fold as VL progressed. B cells from VL dogs were necessary and sufficient to suppress Th1 cell effector function. IgD(hi) B cells induced IL-10 production by T cells and IgD(lo) B cells. Blockage of B cell-specific PD-L1 restored Th1 responses. IgD(hi) regulatory B cells represent a novel regulatory B cell that may precipitate T cell exhaustion during VL.

Retinoic Acid Signaling in B Cells Is Required for the Generation of an Effective T-Independent Immune Response.

Retinoic acid (RA) plays an important role in the balance of inflammation and tolerance in T cells. Furthermore, it has been demonstrated that RA facilitates IgA isotype switching in B cells in vivo. However, it is unclear whether RA has a direct effect on T-independent B cell responses in vivo. To address this question, we generated a mouse model where RA signaling is specifically silenced in the B cell lineage. This was achieved through the overexpression of a dominant negative receptor α for RA (dnRARα) in the B cell lineage. In this model, we found a dramatic reduction in marginal zone (MZ) B cells and accumulation of transitional 2 B cells in the spleen. We also observed a reduction in B1 B cells in the peritoneum with a defect in the T-independent B cell response against 2,4,6-trinitrophenyl. This was not a result of inhibited development of B cells in the bone marrow, but likely the result of both defective expression of S1P1 in MZ B cells and a defect in the development of MZ and B1 B cells. This suggests that RARα expression in B cells is important for B cell frequency in the MZ and peritoneum, which is crucial for the generation of T-independent humoral responses.

Summary of the 2014 Alcohol and Immunology Research Interest Group (AIRIG) meeting.

On November 21, 2014 the 19th annual Alcohol and Immunology Research Interest Group (AIRIG) meeting was held at Loyola University Chicago Health Sciences Campus in Maywood, Illinois. The meeting focused broadly on inflammatory cell signaling responses in the context of alcohol and alcohol-use disorders, and was divided into four plenary sessions focusing on the gut and liver, lung infections, general systemic effects of alcohol, and neuro-inflammation. One common theme among many talks was the differential roles of macrophages following both chronic and acute alcohol intoxication. Macrophages were shown to play significant roles in regulating inflammation, oxidative stress, and viral infection following alcohol exposure in the liver, lungs, adipose tissue, and brain. Other work examined the role of alcohol on disease progression in a variety of pathologies including psoriasis, advanced stage lung disease, and cancer.

Alcohol and inflammatory responses: summary of the 2013 Alcohol and Immunology Research Interest Group (AIRIG) meeting.

Loyola University Chicago, Health Sciences Campus in Maywood, Illinois hosted the 18th annual Alcohol and Immunology Research Interest Group (AIRIG) meeting on November 22, 2013. This year's meeting emphasized alcohol's effect on inflammatory responses in diverse disease states and injury conditions. The meeting consisted of three plenary sessions demonstrating the adverse effects of alcohol, specifically, liver inflammation, adverse systemic effects, and alcohol's role in infection and immunology. Researchers also presented insight on modulation of microRNAs and stress proteins following alcohol consumption. Additionally, researchers revealed sex- and concentration-dependent differences in alcohol-mediated pathologies.

Characterization of a novel mouse model with genetic deletion of CD177.

Neutrophils play an essential role in the innate immune response to infection. Neutrophils migrate from the vasculature into the tissue in response to infection. Recently, a neutrophil cell surface receptor, CD177, was shown to help mediate neutrophil migration across the endothelium through interactions with PECAM1. We examined a publicly available gene array dataset of CD177 expression from human neutrophils following pulmonary endotoxin instillation. Among all 22,214 genes examined, CD177 mRNA was the most upregulated following endotoxin exposure. The high level of CD177 expression is also maintained in airspace neutrophils, suggesting a potential involvement of CD177 in neutrophil infiltration under infectious diseases. To determine the role of CD177 in neutrophils in vivo, we constructed a CD177-genetic knockout mouse model. The mice with homozygous deletion of CD177 have no discernible phenotype and no significant change in immune cells, other than decreased neutrophil counts in peripheral blood. We examined the role of CD177 in neutrophil accumulation using a skin infection model with Staphylococcus aureus. CD177 deletion reduced neutrophil counts in inflammatory skin caused by S. aureus. Mechanistically we found that CD177 deletion in mouse neutrophils has no significant impact in CXCL1/KC- or fMLP-induced migration, but led to significant cell death. Herein we established a novel genetic mouse model to study the role of CD177 and found that CD177 plays an important role in neutrophils.

Primary and long-term B-cell responses in the upper airway and lung after influenza A virus infection.

Influenza A virus (IAV) infection represents a significant global public health burden in addition to its potential as a pandemic killer. Accordingly, the immune response within the respiratory tract and associated lymphoid tissues has been a focus of study for decades. Murine model systems have led to a relatively clear understanding that while innate and T-cell responses are essential for clearance of an initial infection, high affinity neutralizing antibodies (Abs) generated by long-lived Ab forming cells and memory B cells are critical for protection from reinfection and are the goal of classic vaccination strategies. Indeed, the local and systemic IAV-specific Ab response after primary pulmonary infection has been well studied in mice. However, the highly organized microenvironments responsible for producing long-lived, high affinity responses, namely germinal center (GC) reactions, have been less well studied. Recently, work from our laboratory and others has provided new insights into the induction and character of IAV-specific GC responses in the secondary lymphoid organs and the lung. Of interest, these studies have demonstrated IAV reactive GCs to persist for extended periods in both draining lymph nodes and lung tissue. Herein, the primary adaptive response to IAV is reviewed with an emphasis on GC B-cell responses. In addition, data are shown demonstrating the persistence of GCs in the respiratory tract after IAV infection, and key factors that drive their maintenance.

Chronic ethanol feeding induces subset loss and hyporesponsiveness in skin T cells.

BACKGROUND: Chronic alcoholism is associated with increased incidence and severity of cutaneous infection. Skin-resident T cells orchestrate numerous immunological functions that are critically involved in both tissue homeostasis and cutaneous immunity. The impact of chronic ethanol (EtOH) exposure on skin T cells has not previously been examined; given their important role in maintaining the immune barrier function of the skin further study is warranted. METHODS: Mice were administered EtOH in the drinking water for 12 to 16 weeks. Flow cytometry was used to evaluate impact of EtOH feeding on skin T cell numbers, rates of proliferation, and apoptosis as well as activation marker expression and cytokine production after ex vivo stimulation. RESULTS: Chronic EtOH feeding caused a baseline reduction in dendritic epidermal T cell (DETC) numbers that corresponded with reduced expression of the activation marker JAML following phorbol 12-myristate 13-acetate (PMA)/ionomycin stimulation. Chronic EtOH feeding did not alter total numbers of dermal T cells, but specific subset loss was observed in Foxp3(+) regulatory T cells (Tregs) as well as CD3hi, Vγ3(+) and CD3int, Vγ3(-) dermal γδ T cells. EtOH-induced dysfunction in the latter population, which represents prototypical interleukin-17 (IL-17)-producing dermal γδT17s, was made evident by diminished IL-17 production following anti-CD3 stimulation. Additionally, the capacity of lymph node γδ T cells to produce IL-17 following anti-CD3 and PMA/ionomycin stimulation was impaired by chronic EtOH feeding. CONCLUSIONS: Chronic EtOH feeding induced defects in both numbers and function of multiple skin T cell subsets. The decreased density and poor responsiveness of DETCs and γδT17 cells in particular would be expected to compromise immune effector mechanisms necessary to maintain a protective barrier and restrict pathogen invasion. These findings demonstrate the sensitivity of skin T cells to EtOH and provide new mechanisms to help explain the propensity of alcoholics to suffer skin infection.

A gammaherpesvirus Bcl-2 ortholog blocks B cell receptor-mediated apoptosis and promotes the survival of developing B cells in vivo.

Gammaherpesviruses such as Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV, HHV-8) establish lifelong latency in their hosts and are associated with the development of several types of malignancies, including a subset of B cell lymphomas. These viruses are thought to co-opt the process of B cell differentiation to latently infect a fraction of circulating memory B cells, resulting in the establishment of a stable latency setpoint. However, little is known about how this infected memory B cell compartment is maintained throughout the life of the host. We have previously demonstrated that immature and transitional B cells are long-term latency reservoirs for murine gammaherpesvirus 68 (MHV68), suggesting that infection of developing B cells contributes to the maintenance of lifelong latency. During hematopoiesis, immature and transitional B cells are subject to B cell receptor (BCR)-mediated negative selection, which results in the clonal deletion of autoreactive B cells. Interestingly, numerous gammaherpesviruses encode homologs of the anti-apoptotic protein Bcl-2, suggesting that virus inhibition of apoptosis could subvert clonal deletion. To test this, we quantified latency establishment in mice inoculated with MHV68 vBcl-2 mutants. vBcl-2 mutant viruses displayed a marked decrease in the frequency of immature and transitional B cells harboring viral genome, but this attenuation could be rescued by increased host Bcl-2 expression. Conversely, vBcl-2 mutant virus latency in early B cells and mature B cells, which are not targets of negative selection, was remarkably similar to wild-type virus. Finally, in vivo depletion of developing B cells during chronic infection resulted in decreased mature B cell latency, demonstrating a key role for developing B cells in the maintenance of lifelong latency. Collectively, these findings support a model in which gammaherpesvirus latency in circulating mature B cells is sustained in part through the recurrent infection and vBcl-2-mediated survival of developing B cells.

Pulmonary infection with influenza A virus induces site-specific germinal center and T follicular helper cell responses.

Protection from influenza A virus (IAV) challenge requires switched, high affinity Abs derived from long-lived memory B cells and plasma cells. These B cell subsets are generated in germinal centers (GCs), hallmark structures of T helper cell-driven B cell immunity. A full understanding of the GC reaction after respiratory IAV infection is lacking, as is the characterization of T follicular helper (T(FH)) cells that support GCs. Here, GC B cell and T(FH) cell responses were studied in mice following pulmonary challenge with IAV. Marked GC reactions were induced in draining lymph nodes (dLNs), lung, spleen and nasal-associated lymphoid tissue (NALT), although the magnitude and kinetics of the response was site-specific. Examination of switching within GCs demonstrated IgG2(+) cells to compose the largest fraction in dLNs, lung and spleen. IgA(+) GC B cells were infrequent in these sites, but composed a significant subset of the switched GC population in NALT. Further experiments demonstrated splenectomized mice to withstand a lethal recall challenge, suggesting the spleen to be unnecessary for long-term protection in spite of strong GC responses in this organ. Final studies showed that T(FH) cell numbers were highest in dLNs and spleen, and peaked in all sites prior to the height of the GC reaction. T(FH) cells purified from dLNs generated IL-21 and IFNγ upon activation, although CD4(+)CXCR5(-) T effector cells produced higher levels of all cytokines. Collectively, these findings reveal respiratory IAV infection to induce strong T helper cell-driven B cell responses in various organs, with each site displaying unique attributes.

Alcohol and epigenetic changes: summary of the 2011 Alcohol and Immunology Research Interest Group (AIRIG) meeting.

On November 18, 2011, the 16th annual Alcohol and Immunology Research Interest Group (AIRIG) meeting was held at Loyola University Medical Center in Maywood, Illinois. The focus of this year's meeting was alcohol's effect on epigenetic changes and possible outcomes induced by these changes. Two sessions, which consisted of talks from invited speakers as well as presentations of selected abstracts, were held in addition to a poster session. Participants presented information on alcohol-induced alterations in histone modifications and gene expression along with immunologic responses to alcohol. Speakers shared new research specifically on histone deacetylase enzyme expression and modifications due to alcohol and the downstream effect of these modifications may have on gene expression and tissue damage. Additional studies suggested that alcohol exacerbates inflammation when combined with other insults such as infection, trauma, inhalation injury, and disease.

Promotion of a functional B cell germinal center response after Leishmania species co-infection is associated with lesion resolution.

Co-infection of C3HeB/FeJ (C3H) mice with both Leishmania major and Leishmania amazonensis leads to a healed footpad lesion, whereas co-infection of C57BL/6 (B6) mice leads to non-healing lesions. This inability to heal corresponds to a deficiency in B cell stimulation of the macrophage-mediated killing of L. amazonensis in vitro and a less robust antibody response. The mechanism that leads to healing of these lesions is not completely known, although our studies implicate the B cell response as having an important effector function in killing L. amazonensis. To understand more completely this disparate clinical outcome to the same infection, we analyzed the draining lymph node germinal center B cell response between co-infected C3H and B6 mice. There were more germinal center B cells, more antibody isotype-switched germinal center B cells, more memory B cells, and more antigen-specific antibody-producing cells in co-infected C3H mice compared to B6 mice as early as 2 weeks postinfection. Interleukin (IL)-21 production and IL-21 receptor expression in both mouse strains, however, were similar at 2 weeks, suggesting that the difference in the anti-Leishmania response in these mouse strains may be due to differences in T follicular cell commitment or intrinsic B cell differences. These data support the idea that functional B cells are important for healing L. amazonensis in this infectious disease model.

Therapeutic blockade of PD-L1 and LAG-3 rapidly clears established blood-stage Plasmodium infection.

Infection of erythrocytes with Plasmodium species induces clinical malaria. Parasite-specific CD4(+) T cells correlate with lower parasite burdens and severity of human malaria and are needed to control blood-stage infection in mice. However, the characteristics of CD4(+) T cells that determine protection or parasite persistence remain unknown. Here we show that infection of humans with Plasmodium falciparum resulted in higher expression of the inhibitory receptor PD-1 associated with T cell dysfunction. In vivo blockade of the PD-1 ligand PD-L1 and the inhibitory receptor LAG-3 restored CD4(+) T cell function, amplified the number of follicular helper T cells and germinal-center B cells and plasmablasts, enhanced protective antibodies and rapidly cleared blood-stage malaria in mice. Thus, chronic malaria drives specific T cell dysfunction, and proper function can be restored by inhibitory therapies to enhance parasite control.

T regulatory cells participate in the control of germinal centre reactions.

Germinal centre (GC) reactions are central features of T-cell-driven B-cell responses, and the site where antibody-producing cells and memory B cells are generated. Within GCs, a range of complex cellular and molecular events occur which are critical for the generation of high affinity antibodies. These processes require exquisite regulation not only to ensure the production of desired antibodies, but to minimize unwanted autoreactive or low affinity antibodies. To assess whether T regulatory (Treg) cells participate in the control of GC responses, immunized mice were treated with an anti-glucocorticoid-induced tumour necrosis factor receptor-related protein (GITR) monoclonal antibody (mAb) to disrupt Treg-cell activity. In anti-GITR-treated mice, the GC B-cell pool was significantly larger compared with control-treated animals, with switched GC B cells composing an abnormally high proportion of the response. Dysregulated GCs were also observed regardless of strain, T helper type 1 or 2 polarizing antigens, and were also seen after anti-CD25 mAb treatment. Within the spleens of immunized mice, CXCR5(+) and CCR7(-) Treg cells were documented by flow cytometry and Foxp3(+) cells were found within GCs using immunohistology. Final studies demonstrated administration of either anti-transforming growth factor-ß or anti-interleukin-10 receptor blocking mAb to likewise result in dysregulated GCs, suggesting that generation of inducible Treg cells is important in controlling the GC response. Taken together, these findings indicate that Treg cells contribute to the overall size and quality of the humoral response by controlling homeostasis within GCs.

Elevated mitochondrial superoxide disrupts normal T cell development, impairing adaptive immune responses to an influenza challenge.

Reactive oxygen species (ROS) are critical in a broad spectrum of cellular processes including signaling, tumor progression, and innate immunity. The essential nature of ROS signaling in the immune systems of Drosophila and zebrafish has been demonstrated; however, the role of ROS, if any, in mammalian adaptive immune system development and function remains unknown. This work provides the first clear demonstration that thymus-specific elevation of mitochondrial superoxide (O(2)(•-)) disrupts normal T cell development and impairs the function of the mammalian adaptive immune system. To assess the effect of elevated mitochondrial superoxide in the developing thymus, we used a T-cell-specific knockout of manganese superoxide dismutase (i.e., SOD2) and have thus established a murine model to examine the role of mitochondrial superoxide in T cell development. Conditional loss of SOD2 led to increased superoxide, apoptosis, and developmental defects in the T cell population, resulting in immunodeficiency and susceptibility to the influenza A virus H1N1. This phenotype was rescued with mitochondrially targeted superoxide-scavenging drugs. These findings demonstrate that loss of regulated levels of mitochondrial superoxide lead to aberrant T cell development and function, and further suggest that manipulations of mitochondrial superoxide levels may significantly alter clinical outcomes resulting from viral infection.