T cells expressing the Vgamma1 T-cell receptor enhance virus-neutralizing antibody response during coxsackievirus B3 infection of BALB/c mice: differences in male and female mice

Mechanisms and consequences of sex differences in immune responses

Biological sex differences refer to differences between males and females caused by the sex chromosome complement (that is, XY or XX), reproductive tissues (that is, the presence of testes or ovaries), and concentrations of sex steroids (that is, testosterone or oestrogens and progesterone). Although these sex differences are binary for most human individuals and mice, transgender individuals receiving hormone therapy, individuals with genetic syndromes (for example, Klinefelter and Turner syndromes) and people with disorders of sexual development reflect the diversity in sex-based biology. The broad distribution of sex steroid hormone receptors across diverse cell types and the differential expression of X-linked and autosomal genes means that sex is a biological variable that can affect the function of all physiological systems, including the immune system. Sex differences in immune cell function and immune responses to foreign and self antigens affect the development and outcome of diverse diseases and immune responses.

Sex and gender differences in myocarditis and dilated cardiomyopathy: An update

In the past decade there has been a growing interest in understanding sex and gender differences in myocarditis and dilated cardiomyopathy (DCM), and the purpose of this review is to provide an update on this topic including epidemiology, pathogenesis and clinical presentation, diagnosis and management. Recently, many clinical studies have been conducted examining sex differences in myocarditis. Studies consistently report that myocarditis occurs more often in men than women with a sex ratio ranging from 1:2-4 female to male. Studies reveal that DCM also has a sex ratio of around 1:3 women to men and this is also true for familial/genetic forms of DCM. Animal models have demonstrated that DCM develops after myocarditis in susceptible mouse strains and evidence exists for this progress clinically as well. A consistent finding is that myocarditis occurs primarily in men under 50 years of age, but in women after age 50 or post-menopause. In contrast, DCM typically occurs after age 50, although the age that post-myocarditis DCM occurs has not been investigated. In a small study, more men with myocarditis presented with symptoms of chest pain while women presented with dyspnea. Men with myocarditis have been found to have higher levels of heart failure biomarkers soluble ST2, creatine kinase, myoglobin and T helper 17-associated cytokines while women develop a better regulatory immune response. Studies of the pathogenesis of disease have found that Toll-like receptor (TLR)2 and TLR4 signaling pathways play a central role in increasing inflammation during myocarditis and in promoting remodeling and fibrosis that leads to DCM, and all of these pathways are elevated in males. Management of myocarditis follows heart failure guidelines and there are currently no disease-specific therapies. Research on standard heart failure medications reveal important sex differences. Overall, many advances in our understanding of the effect of biologic sex on myocarditis and DCM have occurred over the past decade, but many gaps in our understanding remain. A better understanding of sex and gender effects are needed to develop disease-targeted and individualized medicine approaches in the future.

The function of γδ T cells in humoral immune responses

PURPOSE

The purpose of this review is to discuss the role of γδ T cells played in humoral immune responses.

BACKGROUND

The γδ T cell receptor (γδ TCR) recognizes antigens, including haptens and proteins, in an MHC-independent manner. The recognition of these antigens by γδ TCRs crosses antigen recognition by the B cell receptors (BCRs), suggesting that γδ T cells may be involved in the process of antigen recognition and activation of B cells. However, the role of γδ T cells in humoral immune responses is still less clear.

METHODS

The kinds of literature about the γδ T cell-B cell interaction were searched on PubMed with search terms, such as γδ T cells, antibody, B cell responses, antigen recognition, and infection.

RESULTS

Accumulating evidence indicates that γδ T cells, independent of αβ T cells, participate in multiple steps of humoral immunity, including B cell maturation, activation and differentiation, antibody production and class switching. Mechanically, γδ T cells affect B cell function by directly interacting with B cells, secreting cytokines, or modulating αβ T cells.

CONCLUSION

In this review, we summarize current knowledge on how γδ T cells take part in the humoral immune response, which may assist future vaccine design.

The Role of Non-coding RNAs in Viral Myocarditis

Viral myocarditis (VMC) is a disease characterized as myocardial parenchyma or interstitium inflammation caused by virus infection, especially Coxsackievirus B3 (CVB3) infection, which has no accurate non-invasive examination for diagnosis and specific drugs for treatment. The mechanism of CVB3-induced VMC may be related to direct myocardial damage of virus infection and extensive damage of abnormal immune response after infection. Non-coding RNA (ncRNA) refers to RNA that is not translated into protein and plays a vital role in many biological processes. There is expanding evidence to reveal that ncRNAs regulate the occurrence and development of VMC, which may provide new treatment or diagnosis targets. In this review, we mainly demonstrate an overview of the potential role of ncRNAs in the pathogenesis, diagnosis and treatment of CVB3-induced VMC.

γδT cells contribute to type 2 inflammatory profiles in eosinophilic chronic rhinosinusitis with nasal polyps

Eosinophilic chronic rhinosinusitis with nasal polyps (ECRS) is a condition linked with type 2 inflammation, poor treatment outcomes, and high recurrence tendency. Although γδT cells have been reported to induce type 2 immune responses and eosinophilic infiltration in several diseases, their role in ECRS has not been fully explored. We aimed to evaluate the association of γδT cells with the type 2 inflammatory profiles in ECRS. Nasal tissue samples obtained from patients with chronic rhinosinusitis with nasal polyps (CRSwNP) (51 eosinophilic and 48 non-eosinophilic), 50 patients with chronic rhinosinusitis without nasal polyps (CRSsNP), and 58 control subjects were examined for γδT cells, inflammatory markers and eosinophils using HE, RT-qPCR, ELISA, immunofluorescence, and flow cytometry. In parallel, studies were also conducted in an ECRS murine model induced by anti-γδT cells neutralizing antibody administration. γδT cells expression was significantly increased in tissues from patients with ECRS compared with non-ECRS, CRSsNP and control subjects. Moreover, inflammatory markers including type 2 proinflammatory cytokines (IL-4, IL-5, IL-13), GATA3, eosinophil cationic protein (ECP), and eotaxin levels were also increased in nasal tissues of patients with ECRS, and Vγ1+ γδT cells mRNA expression was positively correlated with type 2 cytokines, GATA3, and ECP. In the ECRS murine model, anti-Vγ1+ γδT antibody treatment reduced the infiltration of eosinophils and expression of type 2 cytokines, GATA3, and ECP in nasal mucosae. In conclusion, the results of the present study suggest that γδT cells play a crucial role in the type 2 inflammatory profiles and nasal tissue eosinophilic infiltration in patients with ECRS.

Long non-coding RNA AK085865 ablation confers susceptibility to viral myocarditis by regulating macrophage polarization

Accumulating evidence indicates that regulators of macrophage polarization may exert pivotal functions in the development of coxsackievirus B3 (CVB3)-induced viral myocarditis (VM). However, the mechanisms underlying macrophage polarization remain to be explored. Here, we sought to identify novel and functionally important long non-coding RNAs (lncRNAs) during macrophage polarization and to investigate their function and contribution to VM. In this study, we identified the lncRNA AK085865 as an important regulator of macrophage polarization. Knock-down of AK085865 diminished phenotypical expression of M2 macrophages while promoting polarization to the M1 phenotype. Moreover, AK085865^-/- mice had increased susceptibility to CVB3-induced VM. We observed striking bias towards M1 macrophages, whereas the M2 population was decreased in AK085865^-/- VM mice. Collectively, our findings uncover a critical role of AK085865 in the regulation of macrophage polarization in vitro and in vivo, identifying a new player in the development of VM and providing a potential clinically significant therapeutic target.

Expansion of CD11b+Ly-6C+ myeloid-derived suppressor cells (MDSCs) driven by galectin-9 attenuates CVB3-induced myocarditis

Galectin-9 is known to play a role in the modulation of innate and adaptive immunity to ameliorate CVB3-induced myocarditis. In the present study, we found that galectin-9 induced the expansion of CD11b⁺Ly-6C⁺ myeloid-derived suppressor cells (MDSCs) in the heart from CVB3-infected mice. Adoptive transfer of CD11b⁺Ly-6C⁺ MDSCs significantly alleviated myocarditis accompanied by increased Th2 and Treg frequency and anti-inflammatory cytokines expression in the heart tissue. Moreover, Ly6C⁺ MDSCs, but not Ly6G⁺ cells, expressed Arg-1 and NOS2, and suppressed CD4⁺ T cell proliferation in vitro in an Arg-1-dependent mechanism; an event that was reversed with treatment of either an Arg-1 inhibitor or addition of excess l-arginine. Furthermore, Ly6C⁺ MDSCs co-expressed higher levels of F4/80, Tim-3, and IL-4Rα, and had the plasticity to up-regulate NOS2 or Arg-1 in response to IFN-γ or IL-4 treatment. The present results indicate that galectin-9 expands CD11b⁺Ly-6C⁺ MDSCs to ameliorate CVB3-induced myocarditis.

Silencing MicroRNA-155 Attenuates Cardiac Injury and Dysfunction in Viral Myocarditis via Promotion of M2 Phenotype Polarization of Macrophages

Macrophage infiltration is a hallmark feature of viral myocarditis. As studies have shown that microRNA-155 regulates the differentiation of macrophages, we aimed to investigate the role of microRNA-155 in VM. We report that silencing microRNA-155 protects mice from coxsackievirus B3 induced myocarditis. We found that microRNA-155 expression was upregulated and localized primarily in heart-infiltrating macrophages and CD4⁺ T lymphocytes during acute myocarditis. In contrast with wildtype (WT) mice, microRNA-155^−/− mice developed attenuated viral myocarditis, which was characterized by decreased cardiac inflammation and decreased intracardiac CD45⁺ leukocytes. Hearts of microRNA-155^−/− mice expressed decreased levels of the IFN-γ and increased levels of the cytokines IL-4 and IL-13. Although total CD4⁺ and regulatory T cells were unchanged in miR-155^−/− spleen proportionally, the activation of T cells and CD4⁺ T cell proliferation in miR-155^−/− mice were significantly decreased. Beyond the acute phase, microRNA-15^5−/− mice had reduced mortality and improved cardiac function during 5 weeks of follow-up. Moreover, silencing microRNA-155 led to increased levels of alternatively-activated macrophages (M2) and decreased levels of classically-activated macrophages (M1) in the heart. Combined, our studies suggest that microRNA-155 confers susceptibility to viral myocarditis by affecting macrophage polarization, and thus may be a potential therapeutic target for viral myocarditis.

Sex-based differences in immune function and responses to vaccination

Females typically develop higher antibody responses and experience more adverse reactions following vaccination than males. These differences are observed in response to diverse vaccines, including the bacillus Calmette-Guerin vaccine, the measles, mumps and rubella vaccine, the yellow fever virus vaccine and influenza vaccines. Sex differences in the responses to vaccines are observed across diverse age groups, ranging from infants to aged individuals. Biological as well as behavioral differences between the sexes are likely to contribute to differences in the outcome of vaccination between the sexes. Immunological, hormonal, genetic and microbiota differences between males and females may also affect the outcome of vaccination. Identifying ways to reduce adverse reactions in females and increase immune responses in males will be necessary to adequately protect both sexes against infectious diseases.

Intricacies of cardiac damage in coxsackievirus B3 infection: implications for therapy

Heart disease is the leading cause of death in humans, and myocarditis is one predominant cause of heart failure in young adults. Patients affected with myocarditis can develop dilated cardiomyopathy (DCM), a common reason for heart transplantation, which to date is the only viable option for combatting DCM. Myocarditis/DCM patients show antibodies to coxsackievirus B (CVB)3 and cardiac antigens, suggesting a role for CVB-mediated autoimmunity in the disease pathogenesis; however, a direct causal link remains to be determined clinically. Experimentally, myocarditis can be induced in susceptible strains of mice using the human isolates of CVB3, and the disease pathogenesis of postinfectious myocarditis resembles that of human disease, making the observations made in animals relevant to humans. In this review, we discuss the complex nature of CVB3-induced myocarditis as it relates to the damage caused by both the virus and the host's response to infection. Based on recent data we obtained in the mouse model of CVB3 infection, we provide evidence to suggest that CVB3 infection accompanies the generation of cardiac myosin-specific CD4 T cells that can transfer the disease to naïve recipients. The therapeutic implications of these observations are also discussed.

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.

Cross-regulation of T regulatory-cell response after coxsackievirus B3 infection by NKT and γδ T cells in the mouse

Coxsackievirus B3 (CVB3) variants H3 and H310A1 differ by a single nonconserved amino acid in the VP2 capsid region. C57Bl/6 mice infected with the H3 virus develop myocarditis correlating with activation of T cells expressing the Vγ4 T cell receptor chain. Infecting mice with H310A1 activates natural killer T (NKT; mCD1d-tetramer(+) TCRβ(+)) cells, but not Vγ4 T cells, and fails to induce myocarditis. H310A1 infection preferentially activates M2 alternatively activated macrophage and CD4(+)FoxP3 (T regulatory) cells, whereas CD4(+)Th1 (IFN-γ(+)) cells are suppressed. By contrast, H3 virus infection activates M1 proinflammatory and CD4(+)Th1 cells, but not T regulatory cells. The M1 macrophage show significantly increased CD1d expression compared to M2 macrophage. The ability of NKT cells to suppress myocarditis was shown by adoptive transfer of purified NKT cells into H3-infected NKT knockout (Jα18 knockout) mice, which inhibited cardiac inflammation and increased T regulatory cell response. Cardiac virus titers were equivalent in all mouse strains indicating that neither Vγ4 nor NKT cells participate in control of virus infection. These data show that NKT and Vγ4 cells cross-regulate T regulatory cell responses during CVB3 infections and are the primary factor determining viral pathogenesis in this mouse model.

Autoimmune myocarditis, valvulitis, and cardiomyopathy

Myocarditis and valvulitis are inflammatory diseases affecting myocardium and valve. Myocarditis, a viral-induced disease of myocardium, may lead to dilated cardiomyopathy and loss of heart function. Valvulitis leads to deformed heart valves and altered blood flow in rheumatic heart disease. Animal models recapitulating these diseases are important in understanding the human condition. Cardiac myosin is a major autoantigen in heart, and antibodies and T cells to cardiac myosin are evident in inflammatory heart diseases. This unit is a practical guide to induction and evaluation of experimental autoimmune myocarditis (EAM) in several mouse strains and the Lewis rat. Purification protocols for cardiac myosin and protocols for induction of EAM by cardiac myosin and its myocarditis-producing peptides, and coxsackievirus CVB3, are defined. Protocols for assessment of myocarditis and valvulitis in humans and animal models provide methods to define functional autoantibodies targeting cardiac myosin, β-adrenergic, and muscarinic receptors, and their deposition in tissues.

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.

Regulatory role of Vγ1 γδ T cells in tumor immunity through IL-4 production

It has been demonstrated that the two main subsets of peripheral γδ T cells, Vγ1 and Vγ4, have divergent functions in many diseases models. Recently, we reported that Vγ4 γδ T cells played a protective role in tumor immunity through eomesodermin-controlled mechanisms. However, the precise roles of Vγ1 γδ T cells in tumor immunity, especially whether Vγ1 γδ T cells have any interaction with Vγ4 γδ T cells, remain unknown. We demonstrated in this paper that Vγ1 γδ T cells suppressed Vγ4 γδ T cell-mediated antitumor function both in vitro and in vivo, and this suppression was cell contact independent. Using neutralizing anti-IL-4 Ab or IL-4(-/-) mice, we determined the suppressive factor derived from Vγ1 γδ T cells was IL-4. Indeed, treatment of Vγ4 γδ T cells with rIL-4 significantly reduced expression levels of NKG2D, perforin, and IFN-γ. Finally, Vγ1 γδ T cells produced more IL-4 and expressed significantly higher level of GATA-3 upon Th2 priming in comparison with Vγ4 γδ T cells. Therefore, to our knowledge, our results established for the first time a negative regulatory role of Vγ1 γδ T cells in Vγ4 γδ T cell-mediated antitumor immunity through cell contact-independent and IL-4-mediated mechanisms. Selective depletion of this suppressive subset of γδ T cells may be beneficial for tumor immune therapy.

Type B coxsackieviruses and their interactions with the innate and adaptive immune systems

Coxsackieviruses are important human pathogens, and their interactions with the innate and adaptive immune systems are of particular interest. Many viruses evade some aspects of the innate response, but coxsackieviruses go a step further by actively inducing, and then exploiting, some features of the host cell response. Furthermore, while most viruses encode proteins that hinder the effector functions of adaptive immunity, coxsackieviruses and their cousins demonstrate a unique capacity to almost completely evade the attention of naive CD8(+) T cells. In this artcle, we discuss the above phenomena, describe the current status of research in the field, and present several testable hypotheses regarding possible links between virus infection, innate immune sensing and disease.

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.

Depletion of gammadelta+ T cells increases CD4+ FoxP3 (T regulatory) cell response in coxsackievirus B3-induced myocarditis

Coxsackievirus B3 (CVB3) causes severe myocarditis in BALB/c mice which depends upon CD4(+) T helper type 1 [Th1; i.e. interferon-gamma(+) (IFN-gamma(+))] and gammadelta(+) cells. Depleting gammadelta(+) cells using anti-gammadelta antibody suppresses myocarditis and CD4(+) IFN-gamma(+) cell numbers in the spleen and heart of infected mice while increasing CD4(+) FoxP3(+) cells. Mice deficient in gammadelta(+) cells have increased numbers of naïve (CD44(lo) CD62L(hi)) and fewer effector (CD44(hi) CD62(lo)) memory CD4(+) cells than infected gammadelta(+)-cell-sufficient mice. Virus neutralizing antibody titres are not significantly different between gammadelta(+) T-cell-sufficient and -deficient animals. To confirm that the memory cell response differs in acutely infected mice lacking gammadelta(+) cells, CD4(+) cells were purified and adoptively transferred into naïve recipients, which were rested for 4 weeks then infected with CVB3. Recipients given either 0.5 x 10(6) or 1.0 x 10(6) CD4(+) from infected donors developed over twice the severity myocarditis and 10-fold less cardiac virus titre compared with recipients given equivalent numbers of CD4(+) cells from infected and gammadelta(+)-cell-depleted donor animals. Additionally, to show that more functionally active T regulatory cells are present in gammadelta(+) T-cell-depleted mice, CD4(+) CD25(+) and CD4(+) CD25(-) cells were isolated and adoptively transferred into infected recipients. Mice receiving CD4(+) CD25(+) cells from gammadelta(+) T-cell-depleted donors developed significantly less myocarditis and CD4(+) Th1 cell responses compared with mice receiving equal numbers of CD4(+) CD25(+) cells from infected gammadelta(+) T-cell-sufficient animals. This study shows that gammadelta(+) cells promote CD4(+) IFN-gamma(+) acute and memory responses by limiting FoxP3(+) T regulatory cell activation.

Differential macrophage polarization in male and female BALB/c mice infected with coxsackievirus B3 defines susceptibility to viral myocarditis

RATIONALE

Myocardial infiltrating macrophages play an important role in the pathogenesis of viral myocarditis in male BALB/c mice following coxsackievirus B3 (CVB3) infection. Interestingly, comparable macrophage numbers were observed in the myocardium of female mice during acute myocarditis.

OBJECTIVE

Given CVB3 infection causes severe myocarditis in male but not female mice, we postulated that macrophages infiltrating the myocardium of female mice may display distinct functional properties that contribute to differential susceptibility to CVB3 myocarditis.

METHODS AND RESULTS

Here, we found that myocardial infiltrating macrophages from CVB3-infected male mice expressed high levels of classically activated macrophages (M1) markers, including inducible nitric oxide synthase, interleukin-12, tumor necrosis factor-alpha, and CD16/32, whereas those of females showed enhanced expression of arginase 1, interleukin-10, macrophage mannose receptor (MMR) and macrophage galactose type C-type lectin (MGL) that were associated with alternatively activated macrophage (M2) phenotype. Moreover, distinct myocardial-derived cytokines were found to play a critical role in differential macrophage polarization between sexes after CVB3 infection. Adoptive transfer of ex vivo programmed M1 macrophages, as expectedly, significantly increased myocarditis in both male and female mice. Strikingly, transfer of M2 macrophages into susceptible male mice remarkably alleviated myocardial inflammation by modulating local cytokine profile and promoting peripheral regulatory T cell (Treg) differentiation.

CONCLUSIONS

Taken together, this study may facilitate the understanding of the mechanism underlying gender bias in susceptibility to CVB3 myocarditis and the development of therapeutic strategies based on macrophage polarization for inflammatory heart disease.