Dual functions of murine gammadelta cells in inflammation and autoimmunity in coxsackievirus B3-induced myocarditis: role of Vgamma1+ and Vgamma4+ cells

The role of γδ T17 cells in cardiovascular disease

Due to the ability of γδ T cells to bridge adaptive and innate immunity, γδ T cells can respond to a variety of molecular cues and acquire the ability to induce a variety of cytokines such as IL-17 family, IFN-γ, IL-4, and IL-10. IL-17⁺ γδ T cells (γδ T17 cells) populations have recently received considerable interest as they are the major early source of IL-17A in many immune response models. However, the exact mechanism of γδ T17 cells is still poorly understood, especially in the context of cardiovascular disease (CVD). CVD is the leading cause of death in the world, and it tends to be younger. Here, we offer a review of the cardiovascular inflammatory and immune functions of γδ T17 cells in order to understand their role in CVD, which may be the key to developing new clinical applications.

Pathogenic Role of an IL-23/γδT17/Neutrophil Axis in Coxsackievirus B3-Induced Pancreatitis

Coxsackievirus B is a common cause of viral myocarditis and pancreatitis. IL-17A is intensively involved in the pathogenesis of viral myocarditis. Whether IL-17A plays a role in Coxsackievirus B-induced pancreatitis, characterized by acinar cell destruction and immune infiltration, remains largely unknown. We found a significant, but transient, increase of IL-17A expression and γδT influx in the pancreas of C57BL/6J mice within 3 d following CVB3 infection. The pancreatic IL-17A was mainly produced by Vγ4 γδ T cells, to a lesser extent by CD4⁺ Th17 cells. IL-17A^-/- and TCRδ^-/- mice both reduced their susceptibility to CVB3 infection and pancreatitis severity when compared with the wild-type mice, without altering viral load. mAb depletion of Vγ4γδ T cells significantly improved mice survival and pancreatic pathology via decreasing Th17 expansion and neutrophil influx into the pancreas compared with isotype-treated mice. Transfer of Vγ4γδ T cells from wild-type, but not IL-17^-/-, mice reconstituted TCRδ^-/- mice to produce IL-17 and develop pancreatitis to the level of wild-type mice during CVB3 infection, indicating γδ T IL-17A is required for the onset of viral pancreatitis. IL-23 was robustly induced in the pancreas within the first day of infection. Administration of exogenous rIL-23 to mice increased CVB3 pancreatitis through in vivo expansion of IL-17⁺γδT17 cells at 12 h postinfection. Our findings reveal a key pathogenic role for early-activated γδT17 cells in viral pancreatitis via promoting neutrophil infiltration and Th17 induction. This IL-23/γδT17/neutrophil axis is critically involved in the onset of CVB3 pancreatitis and represents a potential treating target for the disease.

Vγ4 T Cells Inhibit the Pro-healing Functions of Dendritic Epidermal T Cells to Delay Skin Wound Closure Through IL-17A

Dendritic epidermal T cells (DETCs) and dermal Vγ4 T cells engage in wound re-epithelialization and skin inflammation. However, it remains unknown whether a functional link between Vγ4 T cell pro-inflammation and DETC pro-healing exists to affect the outcome of skin wound closure. Here, we revealed that Vγ4 T cell-derived IL-17A inhibited IGF-1 production by DETCs to delay skin wound healing. Epidermal IL-1β and IL-23 were required for Vγ4 T cells to suppress IGF-1 production by DETCs after skin injury. Moreover, we clarified that IL-1β rather than IL-23 played a more important role in inhibiting IGF-1 production by DETCs in an NF-κB-dependent manner. Together, these findings suggested a mechanistic link between Vγ4 T cell-derived IL-17A, epidermal IL-1β/IL-23, DETC-derived IGF-1, and wound-healing responses in the skin.

Recruitment of Neutrophils Mediated by Vγ2 γδ T Cells Deteriorates Liver Fibrosis Induced by Schistosoma japonicum Infection in C57BL/6 Mice

Conventional adaptive T cell responses contribute to the pathogenesis of Schistosoma japonicum infection, leading to liver fibrosis. However, the role of gamma-delta (γδ) T cells in this disease is less clear. γδ T cells are known to secrete interleukin-17 (IL-17) in response to infection, exerting either protective or pathogenic functions. In the present study, mice infected with S. japonicum are used to characterize the role of γδ T cells. Combined with the infection of S. japonicum, an extremely significant increase in the percentage of neutrophils in the CD45⁺ cells was detected (from approximately 2.45% to 46.10% in blood and from 0.18% to 7.34% in spleen). Further analysis identified two different γδ T cell subsets that have different functions in the formation of granulomas in S. japonicum-infected mice. The Vγ1 T cells secrete gamma interferon (IFN-γ) only, while the Vγ2 T cells secrete both IL-17A and IFN-γ. Both subtypes lose the ability to secrete cytokine during the late stage of infection (12 weeks postinfection). When we depleted the Vγ2 T cells in infected mice, the percentage of neutrophils in blood and spleen decreased significantly, the liver fibrosis in the granulomas was reduced, and the level of IL-17A in the serum decreased (P < 0.05). These results suggest that during S. japonicum infection, Vγ2 T cells can recruit neutrophils and aggravate liver fibrosis by secreting IL-17A. This is the first report that a subset of γδ T cells plays a partial role in the pathological process of schistosome infection.

Vγ1+γδT, early cardiac infiltrated innate population dominantly producing IL-4, protect mice against CVB3 myocarditis by modulating IFNγ+ T response

Viral myocarditis (VMC) is an inflammation of the myocardium closely associated with Coxsackievirus B3 (CVB3) infection. Vγ1⁺γδT cells, one of early cardiac infiltrated innate population, were reported to protect CVB3 myocarditis while the precise mechanism not fully addressed. To explore cytokine profiles and kinetics of Vγ1⁺γδT and mechanism of protection against VMC, flow cytometry was conducted on cardiac Vγ1 cells in C57BL/6 mice following CVB3 infection. The level of cardiac inflammation, transthoracic echocardiography and viral replication were evaluated after monoclonal antibody depletion of Vγ1γδT. We found that Vγ1⁺γδT cells infiltration peaked in the heart at day3 post CVB3 infection and constituted a minor source of IFN-γ but major producers for early IL-4. Vγ1γδT cells were activated earlier holding a higher IL-4-producing efficiency than CD4⁺Th cells in the heart. Depletion of Vγ1⁺γδT resulted in a significantly exacerbated cardiac infiltration, increased T, macrophage and neutrophil population in heart homogenates and worse cardiomyopathy; which was accompanied by a significant expansion of peripheral IFNγ⁺CD4+ and CD8+T cells. Neutralization of IL-4 in mice resulted in an exacerbated acute myocarditis confirming the IL-4-mediated protective mechanism of Vγ1. Our findings identify a unique property of Vγ1⁺γδT cells as one dominant early producers of IL-4 upon CVB3 acute infection which is a key mediator to protect mice against acute myocarditis by modulating IFNγ-secreting T response.

Antiviral effect of emodin from Rheum palmatum against coxsakievirus B5 and human respiratory syncytial virus in vitro

Viral infections are the major causes of morbidity and mortality in elderly people and young children throughout the world. The most common pathogens include coxsackie virus (CV) and respiratory syncytial virus (RSV). However, no antiviral agents with low toxicity and drug resistance are currently available in clinic therapy. The present study aimed to examine the antiviral activities of emodin (an ingredient of Rheum palmatum) against CVB5 and RSV infections, in an attempt to discover new antiviral agents for virus infection. The monomer emodin was extracted and isolated from Rheum palmatum. The antiviral activities of emodin on HEp-2 cells were evaluated, including virus replication inhibition, virucidal and anti-absorption effects, by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tet-razolium bromide (MTT) assay and plaque reduction assay (PRA). The kinetics of virus inhibition by emodin in a period of 14 h was further determined by plaque assay and quantitative real time PCR (qPCR). Cytokine (IFN-γ, TNF-α) mRNA expressions after emodin treatment (7.5, 15, 30 μmol/L) were also assessed by qPCR post-infection. The results showed that emodin had potent inhibitory activities against CVB5 and RSV, with the 50% effective concentration (EC₅₀) ranging from 13.06 to 14.27 μmol/L and selectivity index (SI) being 5.38–6.41 μmol/L. However, emodin couldn’t directly inactivate the viruses or block their absorption to cells. It acted as a biological synthesis inhibitor against CVB₄ and RSV in a concentration- and time-dependent manner, especially during the first 0–4 h post-infection. Moreover, emodin could decrease the mRNA expression of IFN-α but enhance TNF-γ expression significantly compared to the viral controls in vitro. Our results provide a molecular basis for development of emodin as a novel and safe antiviral agent for human enterovirus and respiratory virus infection in the clinical therapy.

γδ T cells promote inflammation and insulin resistance during high fat diet-induced obesity in mice

γδ T cells are resident in AT and increase during diet-induced obesity. Their possible contribution to the inflammatory response that accompanies diet-induced obesity was investigated in mice after a 5 to 10 week milk HFD. The HFD resulted in significant increases in CD44(hi), CD62L(lo), and TNF-α(+) γδ T cells in eAT of WT mice. Mice deficient in all γδ T cells (TCRδ(-/-)) or only Vγ4 and Vγ6 subsets (Vγ4/6(-/-)) were compared with WT mice with regard to proinflammatory cytokine production and macrophage accumulation in eAT. Obesity among these mouse strains did not differ, but obese TCRδ(-/-) and Vγ4/6(-/-) mice had significantly reduced eAT expression of F4/80, a macrophage marker, and inflammatory mediators CCL2 and IL-6 compared with WT mice. Obese TCRδ(-/-) mice had significantly reduced CD11c(+) and TNF-α(+) macrophage accumulation in eAT after 5 and 10 weeks on the HFD, and obese Vγ4/6(-/-) mice had significantly increased CD206(+) macrophages in eAT after 5 weeks on the diet and significantly reduced macrophages after 10 weeks. Obese TCRδ(-/-) mice had significant reductions in systemic insulin resistance and inflammation in liver and skeletal muscle after longer-term HFD feeding (10 and 24 weeks). In vitro studies revealed that isolated γδ T cells directly stimulated RAW264.7 macrophage TNF-α expression but did not stimulate inflammatory mediator expression in 3T3-L1 adipocytes. These findings are consistent with a role for γδ T cells in the proinflammatory response that accompanies diet-induced obesity.

Mucosal co-immunization with AIM2 enhances protective SIgA response and increases prophylactic efficacy of chitosan-DNA vaccine against coxsackievirus B3-induced myocarditis

Coxsackievirus B3 (CVB3) infection is considered as the most common cause of viral myocarditis with no available vaccine. Considering that CVB3 mainly invades through the gastrointestinal mucosa, the development of CVB3-specific mucosal vaccine, which is the most efficient way to induce mucosal immune responses, gains more and more attention. In this study, we used absent in melanoma 2 (AIM2) as a mucosal adjuvant to enhance the immunogenicity and immunoprotection of CVB3-specific chitosan-pVP1 vaccine. Mice were intranasally co-immunized with 50 μg chitosan-pAIM2 and equal amount of chitosan-pVP1 vaccine 4 times at 2 week-intervals, and then challenged with CVB3 2 weeks after the last immunization. Compared with chitosan-pVP1 vaccine immunization alone, chitosan-pAIM2 co-immunization enhanced resistance to CVB3-induced myocarditis evidenced by significantly enhanced ejection fractions from 55.40 ± 9.35 to 80.31 ± 11.35, improved myocarditis scores from 1.50 ± 0.45 to 0.30 ± 0.15, reduced viral load from 3.33 ± 0.50 to 0.50 ± 0.65, and increased survival rate from 40.0% to 75.5%. This increased immunoprotection might be attributed to the augmented level of CVB3-specific fecal SIgA with high affinity and neutralizing ability. In addition, co-immunization with chitosan-pAIM2 remarkably facilitated dendritic cells (DCs) recruitment to mesenteric lymph nodes (MLN), and promoted the expression of IgA-inducing factors (BAFF, APRIL, iNOS, RALDH1, IL-6, TGF-β), which might account for its mucosal adjuvant effect. This strategy may represent a promising prophylactic vaccine against CVB3-induced myocarditis.

In vivo ablation of type I interferon receptor from cardiomyocytes delays coxsackieviral clearance and accelerates myocardial disease

Acute coxsackievirus B3 (CVB3) infection is one of the most prevalent causes of acute myocarditis, a disease that frequently is identified only after the sudden death of apparently healthy individuals. CVB3 infects cardiomyocytes, but the infection is highly focal, even in the absence of a strong adaptive immune response, suggesting that virus spread within the heart may be tightly constrained by the innate immune system. Type I interferons (T1IFNs) are an obvious candidate, and T1IFN receptor (T1IFNR) knockout mice are highly susceptible to CVB3 infection, succumbing within a few days of challenge. Here, we investigated the role of T1IFNs in the heart using a mouse model in which the T1IFNR gene can be ablated in vivo, specifically in cardiomyocytes. We found that T1IFN signaling into cardiomyocytes contributed substantially to the suppression of viral replication and infectious virus yield in the heart; in the absence of such signaling, virus titers were markedly elevated by day 3 postinfection (p.i.) and remained high at day 12 p.i., a time point at which virus was absent from genetically intact littermates, suggesting that the T1IFN-unresponsive cardiomyocytes may act as a safe haven for the virus. Nevertheless, in these mice the myocardial infection remained highly focal, despite the cardiomyocytes' inability to respond to T1IFN, indicating that other factors, as yet unidentified, are sufficient to prevent the more widespread dissemination of the infection throughout the heart. The absence of T1IFN signaling into cardiomyocytes also was accompanied by a profound acceleration and exacerbation of myocarditis and by a significant increase in mortality.

IMPORTANCE

Acute coxsackievirus B3 (CVB3) infection is one of the most common causes of acute myocarditis, a serious and sometimes fatal disease. To optimize treatment, it is vital that we identify the immune factors that limit virus spread in the heart and other organs. Type I interferons play a key role in controlling many virus infections, but it has been suggested that they may not directly impact CVB3 infection within the heart. Here, using a novel line of transgenic mice, we show that these cytokines signal directly into cardiomyocytes, limiting viral replication, myocarditis, and death.

Neutralizing activity induced by the attenuated coxsackievirus B3 Sabin3-like strain against CVB3 infection

Coxsackievirus B3 (CVB3) causes viral myocarditis, and can ultimately result in dilated cardiomyopathy. There is no vaccine available for clinical use. In the present work, we assessed whether the Sabin3-like mutant of CVB3 could induce a protective immunity against virulent CVB3 Nancy and CVB4 E2 strains in mice by both oral and intraperitoneal (IP) routes. Serum samples, taken from mice inoculated with Sabin3-like, were assayed in vitro for their anti-CVB3 neutralizing activity. CVB3 Sabin3-like was highly attenuated in vivo and was able to induce an anti-CVB3 activity of the serum. However, at 4 days post-CVB3 challenge, significant increased titers of CVB3 neutralizing antibodies were detectable in the sera of immunized mice over the next 6 days. Non-immunized mice challenged with CVB3 Nancy had no anti-CVB3 activity in their sera until 10 days post-infection. CVB3 Nancy induced higher viral titers than did the mutant strain. There was no variation of the neutralizing activity of serum taken from mice immunized with CVB3 Sabin3-like and challenged with CVB4 E2, compared to non-immunized mice. Despite the fact that CVB3 and CVB4 are closely related viruses, virus-neutralizing activity clearly distinguish between these viruses. A variable and limited amount of pancreatic inflammation was seen in some mice 10 days after Sabin3-like inoculation by IP route, whereas there was no evidence of pancreatic damage in mice inoculated by oral route. All immunized mice were protected from myocarditis and pancreatitis at 8 days post-challenge with CVB3 or CVB4 E2. These findings strongly suggest that the mutant strain could be considered a candidate for an attenuated CVB3 vaccine.

Relevance of molecular mimicry in the mediation of infectious myocarditis

Heart disease, the leading cause of death in humans, is estimated to affect one in four American adults in some form. One predominant cause of heart failure in young adults is myocarditis, which can lead to the development of dilated cardiomyopathy, a major indication for heart transplantation. Environmental microbes, including viruses, bacteria, and fungi that are otherwise innocuous, have the potential to induce inflammatory heart disease. As the list is growing, it is critical to determine the mechanisms by which microbes can trigger heart autoimmunity and, importantly, to identify their target antigens. This is especially true as microbes showing structural similarities with the cardiac antigens can predispose to heart autoimmunity by generating cross-reactive immune responses. In this review, we discuss the relevance of molecular mimicry in the mediation of infectious myocarditis.

Sex-specific signaling through Toll-Like Receptors 2 and 4 contributes to survival outcome of Coxsackievirus B3 infection in C57Bl/6 mice

Background

Coxsackievirus B3 (CVB3) induces myocarditis, an inflammatory heart disease, which affects men more than women. Toll-like receptor (TLR) signaling has been shown to determine the severity of CVB3-induced myocarditis. No direct role for signaling through TLR2 had been shown in myocarditis although published studies show that cardiac myosin is an endogenous TLR2 ligand and stimulates pro-inflammatory cytokine expression by dendritic cells in vitro. The goal of this study is to determine which TLRs show differential expression in CVB3 infected mice corresponding to male susceptibility and female resistance in this disease.

Methods

Male and female C57Bl/6 mice were infected with 10² PFU CVB3 and killed on day 3 or 6 post infection. Hearts were evaluated for virus titer, myocardial inflammation, and TLR mRNA expression by PCR array and microarray analysis. Splenic lymphocytes only were evaluated by flow cytometry for the number of TLR+/CD3+, TLR+/CD4+, TLR+F4/80+ and TLR+/CD11c+ subpopulations and the mean fluorescence intensity to assess upregulation of TLR expression on these cells. Mice were additionally treated with PAM3CSK4 (TLR2 agonist) or ultrapure LPS (TLR4 agonist) on the same day as CVB3 infection or 3 days post infection to confirm their role in myocarditis susceptibility.

Results

Despite equivalent viral titers, male C57Bl/6 mice develop more severe myocarditis than females by day 6 after infection. Microarray analysis shows a differential expression of TLR2 at day 3 with female mice having higher levels of TLR2 gene expression compared to males. Disease severity correlates to greater TLR4 protein expression on splenic lymphocytes in male mice 3 days after infection while resistance in females correlates to preferential TLR2 expression, especially in spleen lymphocytes. Treating male mice with PAM reduced mortality from 55% in control CVB3 infected animals to 10%. Treating female mice with LPS increased mortality from 0% in control infected animals to 60%.

Conclusion

CVB3 infection causes an up-regulation of TLR2 in female and of TLR4 in male mice and this differential expression between the sexes contributes to disease resistance of females and susceptibility of males. While previous reports demonstrated a pathogenic role for TLR4 this is the first report that TLR2 is preferentially up-regulated in CVB3 infected female mice or that signaling through this TLR directly causes myocarditis resistance.

Manipulating intestinal immunity and microflora: an alternative solution to viral myocarditis?

Viral myocarditis (VMC) is an important cause of heart failure and dilated cardiomyopathy with no effective clinical diagnosis and treatment, and has been commonly associated with Coxsackievirus B3 (CVB3) infection. Current evidence from CVB3 myocarditis in mice indicates that acute myocarditis is mainly mediated by the host immune responses, including Th1, Th17 and type I macrophages. Recently, innate immunity triggered by TLR3, TLR4, TLR8 and MDA5 has also been demonstrated to participate in the induction of inflammatory cytokines in response to CVB3. Apart from the heart tissue, the intestine, which is the assumed initial infection and important replication site for CVB3, needs to be investigated, where induction of innate immunity and interactions with microflora may shape the immune response involved in the pathogenesis of VMC. This review presents recent advances in research into innate and adaptive immunity to CVB3, and provides insights into developing new strategies for the future treatment for VMC.

Sex differences in TLR2 and TLR4 expression and their effect on coxsackievirus-induced autoimmune myocarditis

Coxsackievirus B3 (CVB3) infection of C57Bl/6 mice shows a sex bias with males developing more severe cardiac inflammation than females because males develop a Th1 inflammatory response, whereas females develop a Th2 response. Since their discovery, Toll-like receptors have been shown to play an important role in the development of the immune response against harmful pathogens. To assess the role of TLRs in coxsackievirus-induced myocarditis wild type and Toll-like receptor 2-/- male and female mice were infected and assessed for viral replication, myocarditis, helper T-cell generation, and regulatory T-cell generation. TLR2-/- mice show reduced Th1 expression compared to controls. Treatment of wild type mice with either Pam3CSK4 (TLR2) or LPS (TLR4) specific TLR agonists resulted in increased Th1 expression in male and female mice and a decrease in FoxP3+ regulatory T-cells in male mice. The suppression of T regulatory cells by TLR signaling in males but not females correlates with the increased myocarditis susceptibility of the males.

Type 1 diabetes is associated with enterovirus infection in gut mucosa

Enterovirus infections have been linked to type 1 diabetes in several studies. Enteroviruses also have tropism to pancreatic islets and can cause β-cell damage in experimental models. Viral persistence has been suspected to be an important pathogenetic factor. This study evaluates whether gut mucosa is a reservoir for enterovirus persistence in type 1 diabetic patients. Small-bowel mucosal biopsy samples from 39 type 1 diabetic patients, 41 control subjects, and 40 celiac disease patients were analyzed for the presence of enterovirus using in situ hybridization (ISH), RT-PCR, and immunohistochemistry. The presence of virus was compared with inflammatory markers such as infiltrating T cells, HLA-DR expression, and transglutaminase 2-targeted IgA deposits. Enterovirus RNA was found in diabetic patients more frequently than in control subjects and was associated with a clear inflammation response in the gut mucosa. Viral RNA was often detected in the absence of viral protein, suggesting defective replication of the virus. Patients remained virus positive in follow-up samples taken after 12 months' observation. The results suggest that a large proportion of type 1 diabetic patients have prolonged/persistent enterovirus infection associated with an inflammation process in gut mucosa. This finding opens new opportunities for studying the viral etiology of type 1 diabetes.

Regulation and function of IL-17A- and IL-22-producing γδ T cells

The regulation of IL-17A and IL-22 production differs between human and murine γδ T cells. We find that human γδ T cells expressing Vγ2Vδ2 T cell receptors are peripherally polarized to produce IL-17A or IL-22, much like CD4 αβ Th17 T cells. This requires IL-6, IL-1β, and TGF-β, whereas expansion and maintenance requires IL-23, IL-1β, and TGF-β. In contrast, IL-17A and IL-22 production by murine γδ T cells is innately programmed during thymic ontogeny but requires IL-23 and IL-1β for maintenance. Murine γδ cells producing IL-17A and IL-22 play important roles in microbial, autoimmune, and inflammatory responses. However, the roles played by human IL-17A- and IL-22-producing γδ T cells are less clear but are also likely to be important. These observations highlight differences between humans and murine γδ T cells and underscore the importance of IL-17A- and IL-22-producing γδ T cells.

Characterization of avian γδ T-cell subsets after Salmonella enterica serovar Typhimurium infection of chicks

Avian γδ T lymphocytes are frequently found in blood and organs and are assumed to be crucial to the immune defense against Salmonella infections of chicks. To elucidate the so-far-unknown immunological features of subpopulations of avian γδ T cells in the course of infection, day-old chicks were infected orally with Salmonella enterica serovar Typhimurium. Until 11 days after infection, the occurrence as well as transcription of the CD8 antigen and immunologically relevant protein genes of CD8α(-) and CD8α(+high) (CD8αα(+) CD8αβ(+)) γδ cells were analyzed using flow cytometry and quantitative real-time reverse transcription-PCR (RT-PCR) with blood, spleen, thymus, and cecum samples. After infection, an increased percentage of CD8α(+high) γδ T lymphocytes was found in blood, in spleen, and, with the highest values and most rapidly, in cecum. Within the CD8α(+high) subset, a significant rise in the number of CD8αα(+) cells was accompanied by enhanced CD8α antigen expression and reduced gene transcription of the CD8β chain. CD8αα(+) and CD8αβ(+) cells showed elevated transcription for Fas, Fas ligand (FasL), interleukin-2 receptor α (IL-2Rα), and gamma interferon (IFN-γ). While the highest fold changes in mRNA levels were observed in CD8αβ(+) cells, the mRNA expression rates of CD8αβ(+) cells never significantly exceeded those of the CD8αα(+) cells. In conclusion, both CD8α(+high) γδ T-cell subpopulations (CD8αα(+) and CD8αβ(+)) might be a potential source of IFN-γ in Salmonella-infected chicks. However, due to their prominent frequency in blood and organs after infection, the avian CD8αα(+) γδ T-cell subset seems to be unique and of importance in the course of Salmonella Typhimurium infection of very young chicks.

Tolerizing allergic responses in the lung

The absolute requirement of the pulmonary immune system is to limit the inflammatory consequences of inhaled infectious agents while maintaining tolerance to harmless aeroallergens. This tolerance is maintained by a complex network of cells and molecules interacting with lung stromal cells. However, in some individuals there is a breakdown in tolerance to particles such as pollens, animal dander, or dust, resulting in the development of allergic pathology. Emerging evidence suggests that this breakdown in tolerance is influenced by the genetic background of individuals as well as environmental considerations such as early exposure to respiratory pathogens. Further understanding of the mechanisms used by the pulmonary immune system to maintain tolerance might result in exploitation of novel avenues for therapy to treat the growing number of chronic asthmatic patients.

Naturally activated V gamma 4 gamma delta T cells play a protective role in tumor immunity through expression of eomesodermin

We previously demonstrated that gammadelta T cells played an important role in tumor immune surveillance by providing an early source of IFN-gamma. The precise role of different subsets of gammadelta T cells in the antitumor immune response, however, is unknown. Vgamma1 and Vgamma4 gammadelta T cells are the principal subsets of peripheral lymphoid gammadelta T cells and they might play distinct roles in tumor immunity. In support of this, we observed that reconstitution of TCRdelta(-/-) mice with Vgamma4, but not Vgamma1, gammadelta T cells restored the antitumor response. We also found that these effects were exerted by the activated (CD44(high)) portion of Vgamma4 gammadelta T cells. We further determined that IFN-gamma and perforin are critical elements in the Vgamma4-mediated antitumor immune response. Indeed, CD44(high) Vgamma4 gammadelta T cells produced significantly more IFN-gamma and perforin on activation, and showed greater cytolytic activity than did CD44(high) Vgamma1 gammadelta T cells, apparently due to the high level of eomesodermin (Eomes) in these activated Vgamma4 gammadelta T cells. Consistently, transfection of dominant-negative Eomes in Vgamma4 gammadelta T cells diminished the level of IFN-gamma secretion, indicating a critical role of Eomes in the effector function of these gammadelta T cells. Our results thus reveal distinct functions of Vgamma4 and Vgamma1 gammadelta T cells in antitumor immune response, and identify a protective role of activated Vgamma4 gammadelta T cells, with possible implications for tumor immune therapy.

Tumor necrosis factor-alpha promotes myocarditis in female mice infected with coxsackievirus B3 through upregulation of CD1d on hematopoietic cells

Coxsackievirus B3 (CVB3) induces cardiac inflammation (myocarditis) in male but not female C57BL/6 mice. Protection of females correlates with reduced expression of TNF-alpha and IL-1beta at both the mRNA and protein levels in the heart. Treatment of females with 300 ng/mouse of recombinant TNF-alpha on days +1 and +3 relative to infection restores myocarditis susceptibility to levels approximating those of infected male mice, showing that TNF-alpha deficiency is central to disease resistance. Female mice express little CD1d on spleen lymphocytes or cardiac myocytes, while females treated with TNF-alpha show increased CD1d expression in both cell populations. TNF-alpha treatment of male or female CD1d knockout (CD1dKO) mice failed to restore myocarditis susceptibility, demonstrating that of the multiple potential TNF-alpha activities, its ability to upregulate this non-classical major histocompatibility complex antigen is its dominant function in myocarditis susceptibility. Bone marrow chimeric mice were produced between female C57BL/6 and C57BL/6 CD1dKO mice so that either hematopoietic or non-hematopoietic cells were CD1d deficient. TNF-alpha treatment of chimeric mice having wild-type (CD1d+) hematopoietic cells restored myocarditis susceptibility, while TNF-alpha treatment of chimeric mice having CD1dKO hematopoietic cells, but CD1d+ myocytes, failed to develop myocarditis, showing that CD1d expression in lymphoid cells controls disease susceptibility.

Is the Fas/Fas-L pathway a promising target for treating inflammatory heart disease?

The elucidation of the intricate molecular network of costimulus and regulatory pathways of the immune system led to the design of molecular therapies that specifically inactivate some cellular responses and ameliorate some autoimmune and inflammatory diseases. This innovative concept opens a new class of therapies, and one of the central components that could be targeted in future molecular therapies is the Fas-based pathway. Both soluble and membrane-bound Fas and Fas-L molecules exert a wide range of proinflammatory functions through the secretion of cytokines and chemokines, cellular chemotaxis, transcriptional regulation, cellular death, and others. Accordingly, many chronic inflammatory diseases, including myocarditis, are attenuated in mice lacking either molecule. Although it is tempting to speculate that the Fas/Fas-L pathway could be targeted for in vivo myocarditis therapy, the plurality of Fas/Fas-L functions can be an obstacle, leading to important side effects. In this review, we suggest that the injection of nonagonistic antibodies raised against the Fas molecule or the inactivation of downstream Fas-1,4,5-inositol triphosphate cascade are possible targets for myocarditis treatment.

The in vitro and in vivo antiviral effects of salidroside from Rhodiola rosea L. against coxsackievirus B3

The aim of this study was to investigate the antiviral effects of salidroside, a major component of Rhodiola rosea L. First, the antiviral effects of salidroside against coxsackievirus B3 (CVB3) were determined in vitro and in vivo. Then, the effect of salidroside on the mRNA expression of some important cytokines was measured in hearts of infected BALB/c mice by RT-PCR. Salidroside exhibited obvious antiviral effects both in in vitro and in vivo experiments. Salidroside was found to modulate the mRNA expression of interferon-gamma (IFN-gamma), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-alpha), and interleukin-2 (IL-2). In conclusion, salidroside possesses antiviral activities against CVB3 and it may represent a potential therapeutic agent for viral myocarditis.

Enhanced resistance to coxsackievirus B3-induced myocarditis by intranasal co-immunization of lymphotactin gene encapsulated in chitosan particle

Coxsackievirus B3 (CVB3) is a gastrointestinal virus causing myocarditis in human and mice. An ideal vaccine for CVB3-myocarditis requires both humoral and cellular immunity at systemic and mucosal compartments. We described here an enhancing strategy for chitosan-pVP1 vaccine by co-immunizing with lymphotactin (LTN) gene, a T cell-attractive-chemokine, encapsulated in chitosan particle to provide more protection against CVB3. Mice were intranasally co-immunized with 4 doses of chitosan-DNA vaccines separately encapsulating VP1 and LTN plasmids by 2 week-intervals and challenged with CVB3 4 weeks after the last immunization. Compared with chitosan-pVP1 alone, co-immunization with chitosan-pLTN significantly increased high-avidity-neutralizing antibody levels in serum and in intestinal mucosa, and promoted systemic and mucosal Th1 and CD8(+)CTL immune responses. Accordingly, enhanced resistance to CVB3-myocarditis was evidenced by reduced myocardial viral load, profound subsidence of myocarditis and increased survival rate. This strategy represents a promising platform for Th1 polarization and protection against mucosal infectious pathogens.

Response of gammadelta T Cells to plant-derived tannins

Many pharmaceutical drugs arc isolated from plants used in traditional medicines, and new plant-derived pharmaceutical drugs continue to be identified. Relevant to this review, different plant-derived agonists for gammadelta T cells are described that impart effector functions upon distinct subsets of these cells. Recently, plant tannins have been defined as one class of gammadelta T cell agonist and appear to preferentially activate the mucosal population. Mucosal gammadelta T cells function to modulate tissue immune responses and induce epithelium repair. Select tannins, isolated from apple peel, rapidly induce immune gene transcription in gammadelta T cells, leading to cytokinc production and increased responsiveness to secondary signals. Activity of these tannin preparations tracks to the procyanidin fraction, with the procyanidin trimer (C1) having the most robust activity defined to date. The response to the procyanidins is evolutionarily conserved in that responses are seen with human, bovine, and murine gammadelta T cells, although human cells show less selectivity. Procyanidin-induced responses described in this review likely account for the expansion of mucosal gammadelta T cells seen in mice and rats fed soluble extracts of tannins. Use of procyanidins to activate gammadelta T cells may represent a novel approach for the treatment of tissue damage and autoimmune diseases.

Apoptosis in animal models of virus-induced disease

Apoptosis is associated with virus-induced human diseases of the central nervous system, heart and liver, and causes substantial morbidity and mortality. Although virus-induced apoptosis is well characterized in individual cells in cell culture, virus-induced apoptosis in vivo and the role of apoptosis in virus-induced disease is not well established. This review focuses on animal models of virus-induced diseases of the central nervous system, heart and liver that provide insights into the role of apoptosis in pathogenesis, the pathways involved and the potential therapeutic implications.

Coxsackievirus B3-induced myocarditis: infection of females during the estrus phase of the ovarian cycle leads to activation of T regulatory cells

Transgenic female mice expressing the TNFalpha gene under the cardiac myosin promoter (TNF1.6) develop substantially increased myocarditis and increased numbers of CD4+Th1 (interferon gamma+) cells when infected with coxsackievirus B3 (CVB3) during the diestrus and proestrus phases of the estrus cycle compared to females infected during the estrus and metestrus phases. Cardiac virus titers were increased in females infected in estrus compared to females infected during the other phases. T regulatory cells (CD4+CD25+FoxP3+) were increased in both peripheral blood and inflammatory cells in the heart in females infected during estrus. Exogenous administration of 200 ng/mouse 17-beta-estradiol to females protected against CVB3 induced myocarditis and increased CD4+CD25+FoxP3+ cells. These results demonstrate that hormonal fluctuations occurring in normally cycling females can determine T regulatory cell response and control virus-induced pathogenesis.

Fas ligand-dependent inflammatory regulation in acute myocarditis induced by Trypanosoma cruzi infection

Fas/Fas ligand (Fas-L) engagement, a potent inducer of apoptosis, is also important for cellular activation, regulation of effector and chemotactic activity, and secretion of chemokines and cytokines. We evaluated the relevance of Fas/Fas-L in the regulation of myocarditis induced by Trypanosoma cruzi infection and observed that in Fas-L(-/-) mice (gld/gld), cardiac infiltration was significantly reduced, accordingly showing less cardiomyocyte destruction. Fluorescence-activated cell sorting analysis of cardiac inflammatory cells showed higher numbers of CD8(+) T cells in BALB/c compared with gld/gld mice but similar levels of lymphocyte function-associated antigen-1, intercellular adhesion molecule, CD2, and CD69 expression; MAC-1(+) myeloid cells and mast cells were increased in BALB/c mice, whereas gld/gld mice exhibited an enrichment of CD4(+/low) T cells. Intracellular labeling of cytokines revealed no clear cardiac skewing of Th1 or Th2 responses, but we found a higher number of interleukin-10(+) cells in gld/gld mice and a deficient expression of vascular cell adhesion molecule-1 on cardiac endothelial cells in gld/gld mice. Finally, we found a population of CD3(+) but CD4/CD8 double negative cardiac T cells in both groups of infected mice, but down-regulation of some adhesion molecules and surface receptors was only observed in gld/gld mice, indicating a targeted T-cell population mostly affected by the lack of Fas-L engagement. These results point to a role for myocarditis regulation by Fas/Fas-L beyond its possible direct relevance in cellular death.

Neutralizing anti-4-1BBL treatment improves cardiac function in viral myocarditis

Coxsackievirus B3 (CVB3) is the most common causative agent of infectious myocarditis. Chronic inflammation, loss of contractile tissue, and maladaptive remodeling all contribute to dilated cardiomyopathy and heart failure. The 4-1BB receptor is a costimulatory molecule expressed by T cells and cardiomyocytes. We infected mice with CVB3 to examine if virus infection triggers 4-1BB activation and whether inhibition of this pathway will reduce inflammation and improve heart function. Echocardiography was performed on days 3, 9, 30 and at 10 weeks post-infection (pi) and ejection fraction (EF), left ventricular (LV) wall thickness, contractility, and internal cardiac dimensions were measured. At day 9, reduced rate of wall thickening (30+/-17 vs 70+/-19%), increased LV wall thickness (0.15+/-0.04 vs 0.09+/-0.01 cm in diastole and 0.19+/-0.04 vs 0.15+/-0.02 cm in systole), and reduced cardiac volume (0.013+/-0.004 vs 0.023+/-0.003 ml in diastole and 0.004+/-0.002 ml vs 0.007+/-0.001 ml in systole) were observed in infected hearts as compared with shams. At 14 days pi, CVB3-infected mice were randomly assigned to receive either anti-4-1BBL neutralizing (M522) or control antibodies (Ab) for 8 weeks. Cardiac damage, fibrosis, and inflammation were assessed by histological stains and immunohistochemistry. Polymerase chain reaction (PCR) was utilized to detect matrix metalloproteinase (MMP)-2, MMP-9, and MMP-12 expressions. At 10 weeks pi, M522 treatment improved LV wall thickening rate (-10+/-13 vs -49+/-16%, expressed as percentage change from baseline) and reduced diastolic LV posterior wall thickness (17+/-10 vs 57+/-47%, expressed as percentage change from baseline), cardiac damage as assessed by histological scores (0 vs 1.3+/-1.5), fibrosis by collagen volume fraction (3.2+/-0.6 vs 4.9+/-2.2%), overall inflammation (5.9+/-1.3 vs 8.5+/-4.1%), and T-cell infiltration (1.3+/-0.9 vs 4.3+/-3.8%) as compared to control. MMP-12 was highly increased during acute and chronic myocarditis, but was significantly decreased by M522 treatment. Thus, long-term inhibition of the 4-1BB pathway reduces cardiac damage, remodeling, and inflammation during viral myocarditis.

gammadelta T-cell receptors: functional correlations

The gammadelta T-cell receptors (TCRs) are limited in their diversity, suggesting that their natural ligands may be few in number. Ligands for gammadeltaTCRs that have thus far been determined are predominantly of host rather than foreign origin. Correlations have been noted between the Vgamma and/or Vdelta genes a gammadelta T cell expresses and its functional role. The reason for these correlations is not yet known, but several different mechanisms are conceivable. One possibility is that interactions between particular TCR-V domains and ligands determine function or functional development. However, a recent study showed that at least for one ligand, receptor specificity is determined by the complementarity-determining region 3 (CDR3) component of the TCR-delta chain, regardless of the Vgamma and/or Vdelta. To determine what is required in the TCR for other specificities and to test whether recognition of certain ligands is connected to cell function, more gammadeltaTCR ligands must be defined. The use of recombinant soluble versions of gammadeltaTCRs appears to be a promising approach to finding new ligands, and recent results using this method are reviewed.

Genetic determinants of virulence in the group B coxsackieviruses

The group B coxsackieviruses (CVB) are well-studied human enteroviruses that are established causes of numerous serious human diseases. Characterized differences in CVB genomes of different strains affect the ability with which specific strains induce disease in the mouse host and, by inference, in humans as well. The first hurdle is to define specific examples of CVB genetic changes that are associated with pathogenic phenotypes. Such differences have been mapped both to coding and noncoding genomic regions. Many studies have used laboratory-derived strains to identify genetic differences that are essential to phenotype expression, work that is valuable but requires confirmation from studies of wild-type isolates. Rapid viral replication is closely associated with acute disease, indicating a key role for viral damage to the host, while host-mediated responses to the viral infection and viral persistence over a longer period of time indicate other roles for the virus in pathogenesis.

Immunosurveillance and immunoregulation by gammadelta T cells

Whereas the vast majority of T cells express a T-cell receptor (TCR) composed of alphabeta heterodimers, a smaller population expresses a gammadelta TCR. In contrast to alphabeta T cells, gammadelta T cells show less TCR diversity, are particularly enriched at epithelial surfaces and appear to respond to self-molecules that signal potential danger or cellular stress. In addition, various subsets of gammadelta T cells have shown antitumor and immunoregulatory activities. This review considers what has been discovered about the important cutaneous functions of gammadelta T cells through the study of mutant mice and offers perspectives on the roles of gammadelta T cells in human disease.

Antiviral effects of sophoridine against coxsackievirus B3 and its pharmacokinetics in rats

Coxsackievirus B3 (CVB3) is a major pathogen for acute and chronic viral myocarditis. The aim of this study was to investigate the antiviral effects of sophoridine, an alkaloid extracted from Chinese medicinal herb, Sophora flavescens, against CVB3, and the underlying pharmacokinetics. First, we determined the antiviral effects of sophoridine against CVB3 in in vitro (primarily cultured myocardial cells), in vivo (BALB/c mice) and serum pharmacological experiments. Then, we determined the pharmacokinetic behavior in serum samples of SD rats after oral administration by HPLC. Finally, we determined the effects of sophoridine on the production of cytokines in a murine viral myocarditis model by measuring mRNA expression of some important cytokines in hearts of infected BALB/c mice by RT-PCR. We found that sophoridine exhibited obvious antiviral effects both in vitro and in vivo, and serum samples obtained from rats with oral administration of sophoridine reduced the virus titers in infected myocardial cells. The serum concentration profile correlated closely with antiviral activity profile. Moreover, sophoridine significantly enhanced mRNA expression of IL-10 and IFN-gamma, but decreased TNF-alpha mRNA expression. In conclusion, sophoridine possesses antiviral activities against CVB3, by regulating cytokine expression, and it is likely that sophoridine itself, not its metabolites, is mainly responsible for the antiviral activities. Therefore, sophoridine may represent a potential therapeutic agent for viral myocarditis.