Alterations in major histocompatibility complex association of myocarditis induced by coxsackievirus B3 mutants selected with monoclonal antibodies to group A streptococci

T-Cell Receptor Sequences Identify Combined Coxsackievirus-Streptococci Infections as Triggers for Autoimmune Myocarditis and Coxsackievirus-Clostridia Infections for Type 1 Diabetes

Recent research suggests that T-cell receptor (TCR) sequences expanded during human immunodeficiency virus and SARS-CoV-2 infections unexpectedly mimic these viruses. The hypothesis tested here is that TCR sequences expanded in patients with type 1 diabetes mellitus (T1DM) and autoimmune myocarditis (AM) mimic the infectious triggers of these diseases. Indeed, TCR sequences mimicking coxsackieviruses, which are implicated as triggers of both diseases, are statistically significantly increased in both T1DM and AM patients. However, TCRs mimicking Clostridia antigens are significantly expanded in T1DM, whereas TCRs mimicking Streptococcal antigens are expanded in AM. Notably, Clostridia antigens mimic T1DM autoantigens, such as insulin and glutamic acid decarboxylase, whereas Streptococcal antigens mimic cardiac autoantigens, such as myosin and laminins. Thus, T1DM may be triggered by combined infections of coxsackieviruses with Clostridia bacteria, while AM may be triggered by coxsackieviruses with Streptococci. These TCR results are consistent with both epidemiological and clinical data and recent experimental studies of cross-reactivities of coxsackievirus, Clostridial, and Streptococcal antibodies with T1DM and AM antigens. These data provide the basis for developing novel animal models of AM and T1DM and may provide a generalizable method for revealing the etiologies of other autoimmune diseases. Theories to explain these results are explored.

Bioinformatics and immunoinformatics approach to develop potent multi-peptide vaccine for coxsackievirus B3 capable of eliciting cellular and humoral immune response

Coxsackievirus B3 (CVB3) is a viral pathogen of various human disorders with no effective preventative interventions. Herein, we aimed to design a chimeric vaccine construct for CVB3 using reverse vaccinology and immunoinformatics approaches by screening the whole viral polyprotein sequence. Firstly, screening and mapping of viral polyprotein to predict 21 immunodominant epitopes (B-cell, CD8+ and CD4+ T-cell epitopes), fused with an adjuvant (Resuscitation-promoting factor), appropriate linkers, HIV-TAT peptide, Pan DR epitope, and 6His-tag to assemble a multi-epitope vaccine construct. The chimeric construct is predicted as probable antigen, non-allergen, stable, possess encouraging physicochemical features, and indicates a broader population coverage (98 %). The tertiary structure of the constructed vaccine was predicted and refined, and its interaction with the Toll-like receptor 4 (TLR4) was investigated through molecular docking and dynamics simulation. Computational cloning of the construct was carried out in pET28a (+) plasmid to guarantee the higher expression of the vaccine protein. Lastly, in silico immune simulation foreseen that humoral and cellular immune responses would be elicited in response to the administration of such a potent chimeric construct. Thus, the design constructed could vaccinate against CVB3 infection and various CVB serotypes. However, further in vitro/in vivo research must assess its safety and effectiveness.

Designing a multi-epitope vaccine against coxsackievirus B based on immunoinformatics approaches

Coxsackievirus B (CVB) is one of the major viral pathogens of human myocarditis and cardiomyopathy without any effective preventive measures; therefore, it is necessary to develop a safe and efficacious vaccine against CVB. Immunoinformatics methods are both economical and convenient as in-silico simulations can shorten the development time. Herein, we design a novel multi-epitope vaccine for the prevention of CVB by using immunoinformatics methods. With the help of advanced immunoinformatics approaches, we predicted different B-cell, cytotoxic T lymphocyte (CTL), and helper T lymphocyte (HTL) epitopes, respectively. Subsequently, we constructed the multi-epitope vaccine by fusing all conserved epitopes with appropriate linkers and adjuvants. The final vaccine was found to be antigenic, non-allergenic, and stable. The 3D structure of the vaccine was then predicted, refined, and evaluated. Molecular docking and dynamics simulation were performed to reveal the interactions between the vaccine with the immune receptors MHC-I, MHC-II, TLR3, and TLR4. Finally, to ensure the complete expression of the vaccine protein, the sequence of the designed vaccine was optimized and further performed in-silico cloning. In conclusion, the molecule designed in this study could be considered a potential vaccine against CVB infection and needed further experiments to evaluate its safety and efficacy.

Immune checkpoint inhibitor-associated myocarditis: manifestations and mechanisms

Immune checkpoint inhibitors (ICIs) have transformed the treatment of various cancers, including malignancies once considered untreatable. These agents, however, are associated with inflammation and tissue damage in multiple organs. Myocarditis has emerged as a serious ICI-associated toxicity, because, while seemingly infrequent, it is often fulminant and lethal. The underlying basis of ICI-associated myocarditis is not completely understood. While the importance of T cells is clear, the inciting antigens, why they are recognized, and the mechanisms leading to cardiac cell injury remain poorly characterized. These issues underscore the need for basic and clinical studies to define pathogenesis, identify predictive biomarkers, improve diagnostic strategies, and develop effective treatments. An improved understanding of ICI-associated myocarditis will provide insights into the equilibrium between the immune and cardiovascular systems.

Triggers of Inflammatory Heart Disease

Inflammatory heart disease (IHD) is a group of diseases that includes pericarditis, myocarditis, and endocarditis. Although males appear to be more commonly affected than females, IHD can be seen in any age group. While the disease can be self-limiting leading to full recovery, affected individuals can develop chronic disease, suggesting that identification of primary triggers is critical for successful therapies. Adding to this complexity, however, is the fact that IHD can be triggered by a variety of infectious and non-infectious causes that can also occur as secondary events to primary insults. In this review, we discuss the immunological insights into the development of IHD as well as a mechanistic understanding of the disease process in animal models.

Molecular Mimicry, Autoimmunity, and Infection: The Cross-Reactive Antigens of Group A Streptococci and their Sequelae

The group A streptococci are associated with a group of diseases affecting the heart, brain, and joints that are collectively referred to as acute rheumatic fever. The streptococcal immune-mediated sequelae, including acute rheumatic fever, are due to antibody and cellular immune responses that target antigens in the heart and brain as well as the group A streptococcal cross-reactive antigens as reviewed in this article. The pathogenesis of acute rheumatic fever, rheumatic heart disease, Sydenham chorea, and other autoimmune sequelae is related to autoantibodies that are characteristic of autoimmune diseases and result from the immune responses against group A streptococcal infection by the host. The sharing of host and streptococcal epitopes leads to molecular mimicry between the streptococcal and host antigens that are recognized by the autoantibodies during the host response. This article elaborates on the discoveries that led to a better understanding of the pathogenesis of disease and provides an overview of the history and the most current thought about the immune responses against the host and streptococcal cross-reactive antigens in group A streptococcal sequelae.

miPepBase: A Database of Experimentally Verified Peptides Involved in Molecular Mimicry

Autoimmune diseases emerge due to several reasons, of which molecular mimicry i.e., similarity between the host's and pathogen's interacting peptides is an important reason. In the present study we have reported a database of only experimentally verified peptide sequences, which exhibit molecular mimicry. The database is named as miPepBase (Mimicry Peptide Database) and contains comprehensive information about mimicry proteins and peptides of both host (and model organism) and pathogen. It also provides information about physicochemical properties of protein and mimicry peptides, which might be helpful in predicting the nature of protein and optimization of protein expression. The miPepBase can be searched using a keyword or, by autoimmune disease(s) or by a combination of host and pathogen taxonomic group or their name. To facilitate the search of proteins and/or epitope in miPepBase, which is similar to the user's interest, BLAST search tool is also incorporated. miPepBase is an open access database and available at http://proteininformatics.org/mkumar/mipepbase.

Autoimmune disease triggered by infection with alphaproteobacteria

Despite having long been postulated, compelling evidence for the theory that microbial triggers drive autoimmunity has only recently been reported. A specific association between Novosphingobium aromaticivorans, an ubiquitous alphaproteobacterium, and primary biliary cirrhosis (PBC) has been uncovered in patients with PBC. Notably, the association between Novosphingobium infection and PBC has been confirmed in a mouse model in which infection leads to the development of liver lesions resembling PBC concomitant with the production of anti-PDC-E2 antibodies that cross-react with conserved PDC-E2 epitopes shared by Novosphingobium. The discovery of infectious triggers of autoimmunity is likely to change our current concepts about the etiology of various autoimmune syndromes and may suggest new and simpler ways to diagnose and treat these debilitating diseases.

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.

The nonideal coiled coil of M protein and its multifarious functions in pathogenesis

The M protein is a major virulence factor of Streptococcus pyogenes (group A Streptococcus, GAS). This gram-positive bacterial pathogen is responsible for mild infections, such as pharyngitis, and severe invasive disease, like streptococcal toxic shock syndrome. M protein contributes to GAS virulence in multifarious ways, including blocking deposition of antibodies and complement, helping formation of microcolonies, neutralizing antimicrobial peptides, and triggering a proinflammatory and procoagulatory state. These functions are specified by interactions between M protein and many host components, especially C4BP and fibrinogen. The former interaction is conserved among many antigenically variant M protein types but occurs in a strikingly sequence-independent manner, and the latter is associated in the M1 protein type with severe invasive disease. Remarkably for a protein of such diverse interactions, the M protein has a relatively simple but nonideal α-helical coiled coil sequence. This sequence nonideality is a crucial feature of M protein. Nonideal residues give rise to specific irregularities in its coiled-coil structure, which are essential for interactions with fibrinogen and establishment of a proinflammatory state. In addition, these structural irregularities are reminiscent of those in myosin and tropomyosin, which are targets for crossreactive antibodies in patients suffering from autoimmune sequelae of GAS infection.

The role of infections in autoimmune disease

Autoimmunity occurs when the immune system recognizes and attacks host tissue. In addition to genetic factors, environmental triggers (in particular viruses, bacteria and other infectious pathogens) are thought to play a major role in the development of autoimmune diseases. In this review, we (i) describe the ways in which an infectious agent can initiate or exacerbate autoimmunity; (ii) discuss the evidence linking certain infectious agents to autoimmune diseases in humans; and (iii) describe the animal models used to study the link between infection and autoimmunity.

Autoimmunity in coxsackievirus B3 induced myocarditis

Virus infections are implicated in several autoimmune diseases. Multiple mechanisms of autoimmunity induction have been proposed including antigenic mimicry, production of cryptic epitopes and infection acting as both adjuvant for self-antigens and the mechanism of releasing these cell antigens. Evidence for these mechanisms in coxsackievirus B3 induced myocarditis is discussed.

Evidence of Borrelia autoimmunity-induced component of Lyme carditis and arthritis

We investigated the possibility that manifestations of Lyme disease in certain hosts, such as arthritis and carditis, may be autoimmunity mediated due to molecular mimicry between the bacterium Borrelia burgdorferi and self-components. We first compared amino acid sequences of Streptococcus pyogenes M protein, a known inducer of antibodies that are cross-reactive with myosin, and B. burgdorferi and found significant homologies with OspA protein. We found that S. pyogenes M5-specific antibodies and sera from B. burgdorferi-infected mice reacted with both myosin and B. burgdorferi proteins by Western blots and enzyme-linked immunosorbent assay. To investigate the relationship between self-reactivity and the response to B. burgdorferi, NZB mice, models of autoimmunity, were infected. NZB mice infected with B. burgdorferi developed higher degrees of joint swelling and higher anti-B. burgdorferi immunoglobulin M cross-reactive responses than other strains with identical major histocompatibility complex (DBA/2 and BALB/c). These studies reveal immunological cross-reactivity and suggest that B. burgdorferi may share common epitopes which mimic self-proteins. These implications could be important for certain autoimmunity-susceptible individuals or animals who become infected with B. burgdorferi.

Molecular mimicry may contribute to pathogenesis of ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease with mucosal inflammation and ulceration of the colon. There seems to be no single etiological factor responsible for the onset of the disease. Autoimmunity has been emphasized in the pathogenesis of UC. Perinuclear anti-neutrophil cytoplasmic antibodies (pANCA) are common in UC, and recently two major species of proteins immunoreactive to pANCA were detected in bacteria from the anaerobic libraries. This implicates colonic bacterial protein as a possible trigger for the disease-associated immune response. Autoantibodies and T-cell response against human tropomyosin isoform 5 (hTM5), an isoform predominantly expressed in colon epithelial cells, were demonstrated in patients with UC but not in Crohn's colitis. We identified two bacterial protein sequences in NCBI database that have regions of significant sequence homology with hTM5. Our hypothesis is that molecular mimicry may be responsible for the pathogenesis of UC.

Roles of tumor necrosis factor alpha (TNF-alpha) and the p55 TNF receptor in CD1d induction and coxsackievirus B3-induced myocarditis

Giving C57BL/6 mice 10(4) PFU of coxsackievirus B3 (H3 variant) fails to induce myocarditis, but increasing the initial virus inoculum to 10(5) or 10(6) PFU causes significant cardiac disease. Virus titers in the heart were equivalent at days 3 and 7 in mice given all three virus doses, but day 3 titers in the pancreases of mice inoculated with 10(4) PFU were reduced. Tumor necrosis factor alpha (TNF-alpha) concentrations in the heart were increased in all infected mice, but cytokine levels were highest in mice given the larger virus inocula. TNF-alpha(-/-) and p55 TNF receptor-negative (TNFR(-/-)) mice developed minimal myocarditis compared to B6;129 or C57BL/6 control mice. p75 TNFR(-/-) mice were as disease susceptible as C57BL/6 animals. No significant differences in virus titers in heart or pancreas were observed between the groups, but C57BL/6 and p75 TNFR(-/-) animals showed 10-fold more inflammatory cells in the heart than p55 TNFR(-/-) mice, and the cell population was comprised of high concentrations of CD4(+) gamma interferon-positive and Vgamma4(+) cells. Cardiac endothelial cells isolated from C57BL/6 and p75 TNFR(-/-) mice upregulate CD1d, the molecule recognized by Vgamma4(+) cells, but infection of TNF(-/-) or p55 TNFR(-/-) endothelial cells failed to upregulate CD1d. Infection of C57BL/6 endothelial cells with a nonmyocarditic coxsackievirus B3 variant, H310A1, which is a poor inducer of TNF-alpha, failed to elicit CD1d expression, but TNF-alpha treatment of H310A1-infected endothelial cells increased CD1d levels to those seen in H3-infected cells. TNF-alpha treatment of uninfected endothelial cells had only a modest effect on CD1d expression, suggesting that optimal CD1d upregulation requires both infection and TNF-alpha signaling.

Role of CD1d in coxsackievirus B3-induced myocarditis

The myocarditic (H3) variant of Coxsackievirus B3 (CVB3) causes severe myocarditis in BALB/c mice and BALB/c mice lacking the invariant J alpha 281 gene, but minimal disease in BALB/c CD1d(-/-) animals. This indicates that CD1d expression is important in this disease but does not involve the invariant NKT cell often associated with CD1d-restricted immunity. The H3 variant of the virus increases CD1d expression in vitro in neonatal cardiac myocytes whereas a nonmyocarditic (H310A1) variant does not. V gamma 4(+) T cells show increased activation in both H3-infected BALB/c and J alpha 281(-/-) mice compared with CD1d(-/-) animals. The activated BALB/c V gamma 4(+) T cells from H3-infected mice kill H3-infected BALB/c myocytes and cytotoxicity is blocked with anti-CD1d but not with anti-MHC class I (K(d)/D(d)) or class II (IA/IE) mAbs. In contrast, H3 virus-infected CD1d(-/-) myocytes are not killed. These studies demonstrate that CD1d expression is essential for pathogenicity of CVB3-induced myocarditis, that CD1d expression is increased early after infection in vivo in CD1d(+) mice infected with the myocarditic but not with the nonmyocarditic CVB3 variant, and that V gamma 4(+) T cells, which are known to promote myocarditis susceptibility, appear to recognize CD1d expressed by CVB3-infected myocytes.

Induction of myocarditis and valvulitis in lewis rats by different epitopes of cardiac myosin and its implications in rheumatic carditis

Immune responses against cardiac myosin and group A streptococcal M protein have been implicated in the pathogenesis of rheumatic heart disease. Although cardiac myosin is known to produce myocarditis in susceptible animals, it has never been investigated for its role in production of valvular heart disease, the most serious sequelae of group A streptococcal infection in acute rheumatic fever. In our study, cardiac myosin induced valvulitis in the Lewis rat, and epitopes responsible for production of valvulitis were located in the rod region. Human and rat cardiac myosins induced severe myocarditis in the Lewis rats as expected. A purified S2 fragment (amino acid sequences 842 to 1295) produced the most severe myocarditis as well as valvulitis. Different regions of light meromyosin produced valvulitis (residues 1685 to 1936) or myocarditis (residues 1529 to 1611). Because streptococcal M proteins produced valvular heart disease in Lewis rats and have been linked to anti-cardiac myosin responses, we reacted myosin-sensitized lymphocytes isolated from the hearts of Lewis rats with peptides of streptococcal M5 protein in tritiated thymidine assays. Infiltrating lymphocytes responded most strongly to peptides within the B repeat region of streptococcal M protein. These data show direct evidence that immune responses against cardiac myosin lead to valvular heart disease and the infiltration of the heart by streptococcal M protein reactive T lymphocytes.

Molecular mimicry and immune-mediated diseases

Molecular mimicry has been proposed as a pathogenetic mechanism for autoimmune disease, as well as a probe useful in uncovering its etiologic agents. The hypothesis is based in part on the abundant epidemiological, clinical, and experimental evidence of an association of infectious agents with autoimmune disease and observed cross-reactivity of immune reagents with host 'self' antigens and microbial determinants. For our purpose, molecular mimicry is defined as similar structures shared by molecules from dissimilar genes or by their protein products. Either the molecules' linear amino acid sequences or their conformational fits may be shared, even though their origins are as separate as, for example, a virus and a normal host self determinant. An immune response against the determinant shared by the host and virus can evoke a tissue-specific immune response that is presumably capable of eliciting cell and tissue destruction. The probable mechanism is generation of cytotoxic cross-reactive effector lymphocytes or antibodies that recognize specific determinants on target cells. The induction of cross-reactivity does not require a replicating agent, and immune-mediated injury can occur after the immunogen has been removed a hit-and-run event. Hence, the viral or microbial infection that initiates the autoimmune phenomenon may not be present by the time overt disease develops. By a complementary mechanism, the microbe can induce cellular injury and release self antigens, which generate immune responses that cross-react with additional but genetically distinct self antigens. In both scenarios, analysis of the T cells or antibodies specifically engaged in the autoimmune response and disease provides a fingerprint for uncovering the initiating infectious agent.

Molecular Analysis of Polyreactive Monoclonal Antibodies from Rheumatic Carditis: Human Anti-N-Acetylglucosamine/Anti-Myosin Antibody V Region Genes

Anti-myosin Abs are associated with inflammatory heart diseases such as rheumatic carditis and myocarditis. In this study, human cross-reactive anti-streptococcal/anti-myosin mAbs 1.C8, 1.H9, 5.G3, and 3.B6, produced from peripheral blood lymphocytes of patients with rheumatic carditis, and mAb 10.2.5, produced from a tonsil, were characterized, and the nucleotide sequences of their VH and VL genes were analyzed. Human mAbs 1.C8, 1.H9, 10.2.5, and 3.B6 reacted with human cardiac myosin while mAb 5.G3 did not. The mAbs were strongly reactive with N-acetyl-β-d-glucosamine, the dominant epitope of the group A streptococcal carbohydrate. mAb 1.H9 was moderately cytotoxic to rat heart cells in vitro in the presence of complement. The anti-myosin mAbs from rheumatic carditis were found to react with specific peptides from the light meromyosin region of the human cardiac myosin molecule. Anti-streptococcal/anti-myosin mAbs from normal individuals reacted with distinctly different light meromyosin peptides. The mAbs were encoded by VH3 gene segments V3-8, V3-23, and V3-30 and by the VH4 gene segment V4-59. The variable region genes encoding the anti-streptococcal/anti-myosin repertoire were heterogeneous and exhibited little evidence of Ag-driven somatic mutation.

A short history and introductory background on the coxsackieviruses of group B

The past 50 years have revealed an array of significant developments in our documentation and understanding of viruses and their associated diseases. The CVB, as enteroviruses, were discovered in the search for poliomyelitis-related viruses by the inoculation of newborn mice. Future strategies for the discovery of additional viruses will undoubtedly come through the application of differentiating cell culture systems with increased susceptibility to infection by specific viruses. Developments in regulation of the cell cycle also will contribute to the better definition of events controlling persistent infections caused by the CVB. Methods utilizing molecular biological probes in situ will prove to be major aids in identifying the molecular events in CVB pathogenesis. Virology of the CVB continues to be an exciting area for research and application of preventive measures to lesson human suffering. The chapters in this book which follow will amplify most of the themes briefly presented here.

Generation of an infectious cDNA of a highly cardiovirulent coxsackievirus B3(CVB3m) and comparison to other infectious CVB3 cDNAs

An infectious cDNA of a highly myocarditic coxsackievirus B3 (CVB3m; Nancy strain) was cloned. Sequence data revealed 43 extra non-viral nucleotides upstream of the initial 5' sequence. However, the authentic 5' end sequence was maintained during replication of viral RNA transfected into HeLa cells, suggesting the RNA synthesizing complex edits the picornaviral 5' terminus sequence. Nucleotide sequences of the 5' nontranslated region and the capsid protein gene sequence of CVB3m were compared with the published sequences of five other CVB3 Nancy strains and two main lineages were found. In comparative assays for cardiovirulence, three of four CVB3 tested were cardiovirulent in adolescent male CD-1 mice. Only one of the three available CVB3 strains was neutralized with several anti-CVB3m monoclonal antibodies, suggesting that mutations in the surface epitopes of the capsid polypeptides contribute to antigenic drift within the serotype, perhaps in part through immunoselective pressures. Thus, phenotypic diversity of CVB3 within the prototype Nancy strain is an example of RNA viruses adapting to changing environments (cells, mice and humans) through mutations and selective pressure.

Autoimmunity in myocarditis: relevance of animal models

Infections (viruses, bacteria, protozoa, fungi) are major etiological factors causing clinical myocarditis and dilated cardiomyopathy. In many patients and symptom-free relatives antibodies and T cells reactive to heart antigens are detected, which implies that autoimmunity is probably a major pathogenic mechanism of cardiac injury. Animal models have been established to elucidate how infections initiate autoimmunity and how autoimmune mediators cause death or transient dysfunction of myocytes. Two major types of experimental models are discussed: adjuvant-induced myocarditis, in which animals are given multiple immunizations of heart proteins (myosin, adenine nucleotide translocator); and virus-induced myocarditis, in which animals are infected with the viruses predominantly associated with the human disease.

A mutation in the puff region of VP2 attenuates the myocarditic phenotype of an infectious cDNA of the Woodruff variant of coxsackievirus B3

Coxsackievirus B3 (CVB3) infections induce myocarditis in humans and mice. Little is known about the molecular characteristics of CVB3 that activate the cellular immunity responsible for cardiac inflammation. Previous experiments have identified an antibody escape mutant (H310A1) of a myocarditic variant of CVB3 (H3) that attenuates the myocarditic potential of the virus in mice in spite of ongoing viral replication in the heart. We have cloned full-length infectious cDNA copies of the viral genome of both the wild-type myocarditic H3 variant of CVB3 and the antibody escape mutant H310A1. Progeny viruses maintained the myocarditic and attenuated myocarditic potential of the parent viruses, H3 and H310A1. The full sequence of the H3 viral cDNA is reported and compared with those of previously published CVB3 variants. Comparison of the full sequences of H3 and H310A1 viruses identified a single nonconserved mutation (A to G) in the P1 polyprotein region at nucleotide 1442 resulting in an asparagine-to-aspartate mutation in amino acid 165 of VP2. This mutation is in a region that corresponds to the puff region of VP2. Nucleotide 1442 of the H3 and H310A1 cDNA copies of the viral genome was mutated to change amino acid 165 of VP2 to aspartate and asparagine, respectively. The presence of asparagine at amino acid 165 of VP2 is associated with the myocarditic phenotype, while an aspartate at the same site reduces the myocarditic potential of the virus. In addition, high-level production of tumor necrosis factor alpha by infected BALB/c monocytes is associated with asparagine at amino acid 165 of VP2 as has been previously demonstrated for the H3 virus. These findings identify potentially important differences between the H3 variant of CVB3 and other previously published CVB3 variants. In addition, the data demonstrate that a point mutation in the puff region of VP2 can markedly alter the ability of CVB3 to induce myocarditis in mice and tumor necrosis factor alpha secretion from infected BALB/c monocytes.

Modulation of cytokine expression by CD4+ T cells during coxsackievirus B3 infections of BALB/c mice initiated by cells expressing the gamma delta + T-cell receptor

Two variants of coxsackievirus B3 have been used to investigate the pathogenesis of myocarditis in BALB/c mice. H3 virus induces moderate myocarditis and H310A1 virus induces minimal myocarditis, although both viruses infect and replicate in the heart. Cells expressing the gamma delta+ T-cell receptor composed 5 to 13% of the lymphocytes infiltrating the hearts of H3 virus-infected mice and belonged to either the CD4- CD8+ gamma delta+- or CD4- CD8- gamma delta+-cell population. Giving 5,000 gamma delta+ cells isolated from the hearts of H3 virus-infected mice to H310A1 virus-infected recipients restored myocarditis susceptibility in the recipient animals and shifted the pattern of cytokine production in the virus-immune CD4+-cell population from being predominantly interleukin-4 producing to being predominantly gamma interferon producing in the H310A1 virus-infected mice. Apoptosis was evident in the infiltrating lymphocyte population in the myocardia of H3 virus-infected mice by the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling assay and in splenic lymphocytes by DNA fragmentation in agarose gel electrophoresis and was confined to the CD4+ population. No apoptosis was observed in H310A1 virus-infected mice, but apoptosis was induced subsequent to gamma delta +-T-cell transfer. These results are consistent with the hypothesis that gamma delta+ T cells may help modulate cytokine responses during virus infections in vivo and that apoptosis might be involved in this modulation.

Immunological mimicry between retinal S-antigen and group A streptococcal M proteins

Immunological mimicry between host and microbial proteins has been suggested as a potential mechanism in the development of uveitis in humans. In this study immunological crossreactivity between anti-streptococcal monoclonal antibodies (MAbs) and the human eye was investigated. In indirect immunofluorescence, we demonstrated novel immunological crossreactivity of two anti-streptococcal MAbs (27 and 112) with the rod outer (and inner) segments of the retina of the human eye. In further studies, retinal S-Ag, a uveitogenic protein in the rod outer (and inner) segments, was found to react with the anti-streptococcal MAbs. In addition, several uveitogenic peptides of S-Ag were recognized by the anti-streptococcal MAbs. In the ELISA and Western immunoblot, anti-S-Ag MAbs crossreacted with group A streptococci and the streptococcal M protein further demonstrating sites of antigenic similarity. Homology between the retinal S-Ag and streptococcal M protein was observed in amino acid sequences repeated in the B repeat region of the streptococcal M5 protein. These data show that retinal S-antigen has immunological similarities with streptococcal M protein, a major virulence determinant and strong bacterial cell surface antigen.