Differential recruitment of B and T cells in coxsackievirus B4-induced pancreatitis is influenced by a capsid protein

Pancreatitis-associated Myocarditis: Systematic Review and Meta-analysis of a Deadly Duo

Myocardial injury is a recognized complication of acute pancreatitis, whereas myocarditis has only been occasionally reported and has not been systematically evaluated. We systematically reviewed PubMed literature published up to January 2024 for studies including both “myocarditis” and “pancreatitis” as keywords. Relevant data regarding patient characteristics and outcomes were collected and analyzed. A total of 31 patients from 31 independent studies were included. The etiology of pancreatitis was viral in 52%, bacterial in 20%, toxic in 16%, autoimmune in 9%, and idiopathic in 3%. 23% of patients were immunocompromised. Median high sensitivity-cardiac troponin T was 342 (IQR 73-890) ng/L and N-terminus-pro-brain natriuretic peptide was 11053 (IQR 1397-26150) pg/mL. The average left ventricular ejection fraction was 33±13%. Fulminant myocarditis, presenting with cardiogenic shock and/or malignant ventricular arrhythmias occurred in 48% of patients, more frequently in men than in women (P=0.026). Severe myocarditis occurred in 42% of edematous and 60% of necrotizing pancreatitis (P=0.56). No association was found between the severity of myocarditis and plasma levels of amylase (P=0.98) and lipase (P=0.83). The relative frequency of severe myocarditis was 80% in pancreatitis due to Leptospirosis, and 40% in pancreatitis due to viral infections. The mortality rate was 22%: 13% died during hospitalization and 9% after. Myocarditis is a potentially lethal complication of pancreatitis and is more frequently associated with viral etiology in immunocompromised individuals. Based on such findings, cardiac troponin measurements and an electrocardiogram are advisable to exclude myocardial involvement in selected patients. Confirmatory diagnosis and prognostic assessments should be based on cardiac magnetic resonance imaging.

The Role of Pancreatic Infiltrating Innate Immune Cells in Acute Pancreatitis

Acute pancreatitis (AP) is a leading cause of gastrointestinal-related hospital admissions with significant morbidity and mortality. Although the underlying pathophysiology of AP is rather complex, which greatly limits the treatment options, more and more studies have revealed that infiltrating immune cells play a critical role in the pathogenesis of AP and determine disease severity. Thus, immunomodulatory therapy targeting immune cells and related inflammatory mediators is expected to be a novel treatment modality for AP which may improve the prognosis of patients. Cells of the innate immune system, including macrophages, neutrophils, dendritic cells, and mast cells, represent the majority of infiltrating cells during AP. In this review, an overview of different populations of innate immune cells and their role during AP will be discussed, with a special focus on neutrophils and macrophages.

Review of Infectious Etiology of Acute Pancreatitis

While gallstones and alcoholism are widely known to be the most common causative agents of acute pancreatitis, about 10% of cases are thought to be caused by infectious microorganisms. These microorganisms include viruses (e.g. mumps, Coxsackie B, and hepatitis), bacteria (e.g. Mycoplasma pneumoniae and leptospirosis), and parasites (e.g. Ascaris lumbricoides, Fasciola hepatica, and hydatid disease). Each organism causes acute pancreatitis through diverse mechanisms. The review is primarily conducted in an attempt to provide a better understanding of the possibility of acute pancreatitis presenting as a complication relating to these organisms, and the aim is to guide future diagnoses, management, and predictions of complications.

A single amino acid substitution in viral VP1 protein alters the lytic potential of clone-derived variants of echovirus 9 DM strain in human pancreatic islets

In vitro studies with primary human pancreatic islets suggest that several enterovirus serotypes are able to infect and replicate in beta cells. Some enterovirus strains are highly cytolytic in vitro whereas others show virus replication with no apparent islet destruction. The capability to induce islet destruction is determined only partially by the virus serotype, since strain specific differences have been detected within some serotypes including echovirus 9 (E-9). In this study, the viral genetic factors determining the outcome of islet infection (i.e., destructive vs. benign) were investigated by constructing parallel infectious clones of lytic E-9-DM strain that was isolated from a small child at the clinical onset of type 1 diabetes. The capabilities of these clone-derived viruses to induce islet destruction were monitored and the lytic potential of clones was modified by site-directed mutagenesis. The lytic capabilities of these clone-derived viruses in human pancreatic islets were modified by a single amino acid substitution (T81A) in the capsid protein VP1. The data presented outline the importance of amino acid point mutations in the pathogenetic process leading to islet necrosis. However, although the amino acid substitution (T81A) modifies the lytic capabilities of E-9-DM strain-derived microvariant strains, it is likely that additional viral genetic determinants of pancreatic islet pathogenicity exist in other E-9 strains.

Dynamics of molecular responses to coxsackievirus B4 infection differentiate between resolution and progression of acute pancreatitis

A coxsackievirus B4 induces acute pancreatitis with different outcomes. The study utilized a systems biology approach to identify molecular immune responses that differentiate between disease resolution and disease progression. The data establish a temporal pattern of host responses that differentiate the resolution of acute pancreatitis from the progression to chronic pancreatitis. A group of twenty-five genes exhibited characteristic expression profiles that were observed during the development of chronic pancreatitis but not during the resolution of disease. We postulate that the temporal dynamics of the twenty-five genes influence the development of pathogenic immune responses associated with chronic pancreatitis. Furthermore, a subset of eleven genes exhibited increased expression as viral titers waned. Of the eleven gene products, five are secreted molecules, TNF-α, IFN-γ, CXCL10, IL-10, and IL-22b, and represent novel potential therapeutic targets since they can be readily modulated with antibodies against the specific cytokine/chemokine or with antibodies against the corresponding receptors.

Evolution of newly described enteroviruses

Several new enterovirus serotypes and a new human rhinovirus species have been characterized in the Enterovirus genus recently, raising a question about the origin of the new viruses. In this article we attempt to outline the general patterns of enterovirus evolution, ultimately leading to the emergence of new serotypes or species. Different evolutionary and epidemiological patterns can be deduced between different enterovirus species, between entero- and rhino-viruses and between different serotypes within a species. This article presents a hypothesis that the divergent evolution leading to a new serotype is likely to involve adaptation to a new ecological niche either within a single host species or due to interspecies transmission. By contrast, evolution within a serotype appears to occur primarily by genetic drift.

Oral immunization with a live coxsackievirus/HIV recombinant induces gag p24-specific T cell responses

Background

The development of an HIV/AIDS vaccine has proven to be elusive. Because human vaccine trials have not yet demonstrated efficacy, new vaccine strategies are needed for the HIV vaccine pipeline. We have been developing a new HIV vaccine platform using a live enterovirus, coxsackievirus B4 (CVB4) vector. Enteroviruses are ideal candidates for development as a vaccine vector for oral delivery, because these viruses normally enter the body via the oral route and survive the acidic environment of the stomach.

Methodology/Principal Findings

We constructed a live coxsackievirus B4 recombinant, CVB4/p24(73₃), that expresses seventy-three amino acids of the gag p24 sequence (HXB2) and assessed T cell responses after immunization of mice. The CVB4 recombinant was physically stable, replication-competent, and genetically stable. Oral or intraperitoneal immunization with the recombinant resulted in strong systemic gag p24-specific T cell responses as determined by the IFN-γ ELISPOT assay and by multiparameter flow cytometry. Oral immunization with CVB4/p24(73₃) resulted in a short-lived, localized infection of the gut without systemic spread. Because coxsackieviruses are ubiquitous in the human population, we also evaluated whether the recombinant was able to induce gag p24-specific T cell responses in mice pre-immunized with the CVB4 vector. We showed that oral immunization with CVB4/p24(73₃) induced gag p24-specific immune responses in vector-immune mice.

Conclusions/Significance

The CVB4/p24(73₃) recombinant retained the physical and biological characteristics of the parental CVB4 vector. Oral immunization with the CVB4 recombinant was safe and resulted in the induction of systemic HIV-specific T cell responses. Furthermore, pre-existing vector immunity did not preclude the development of gag p24-specific T cell responses. As the search continues for new vaccine strategies, the present study suggests that live CVB4/HIV recombinants are potential new vaccine candidates for HIV.

IL-10 is pathogenic during the development of coxsackievirus B4-induced chronic pancreatitis

Using a mouse model of coxsackievirus B4 (CVB4-V)-induced chronic pancreatitis, we investigated whether cytokines are involved in the progression of acute disease to chronic inflammatory disease. We show that IL-10 contributed to the development of chronic pancreatitis since acute disease resolved when IL-10 was absent or when IL-10 signaling was disrupted. We explored the underlying mechanisms by which IL-10 affected disease progression, using a novel approach to assess immunological events occurring in situ. Multiple markers that define functional innate immune responses and functional T cell responses were monitored over the course of CVB4-V infection of wild-type and IL-10 knockout mice, using a multiplex transcriptional profiling approach. We show that high levels of IL-10 early during infection were associated with delayed innate and T cell responses. Furthermore, high IL-10 production correlated with altered kinetics of T regulatory responses indicating a disruption in the balance between effector and regulatory T cell responses.

Amino acids of Coxsackie B5 virus are critical for infection of the murine insulinoma cell line, MIN-6

It was shown recently that 15 successive passages of a laboratory strain of the Coxsackie B virus 5 in a mouse pancreas (CBV-5-MPP) resulted in apparent changes in the virus phenotype, which led to the capacity to induce a diabetes-like syndrome in mice. For further characterization of islet cell interactions with a passaged virus strain, a murine insulinoma cell line, MIN-6, was selected as an experimental model. The CBV-5-MPP virus strain was not able to replicate in MIN-6 cells in vitro but required adaptation over a few days for progeny production and the generation of cytopathic effects. In order to determine the genetic characteristics required for virus growth in MIN-6 cells, the whole genome of the MIN-6-adapted virus variant was sequenced, and critical amino acids were identified by comparing the sequence with that of a virus strain passaged repeatedly in the mouse pancreas. The results of site-directed mutagenesis demonstrated that only one residue, amino acid 94 of VP1, is a major determinant for virus adaptation to MIN-6 cells.

Enumeration and functional evaluation of virus-specific CD4+ and CD8+ T cells in lymphoid and peripheral sites of coxsackievirus B3 infection

Previous studies have suggested that coxsackievirus B (CVB) activates CD8(+) T cells in vivo, but the extent of this activation and the antigen specificity of the CD8(+) T cells remain uncertain. Furthermore, CVB-induced CD4(+) T-cell responses have not been carefully investigated. Herein, we evaluate CD8(+) and CD4(+) T-cell responses both in a secondary lymphoid organ (spleen) and in peripheral tissues (heart and pancreas), using a recombinant CVB3 (rCVB3.6) that encodes well-characterized CD8(+) and CD4(+) T-cell epitopes. Despite reaching high levels in vivo, rCVB3.6 failed to trigger a marked expansion of CD8(+) or CD4(+) T cells, and T-cell activation was surprisingly limited. Furthermore, epitope-specific effector functions could not be detected using highly sensitive in vivo and ex vivo assays. Moreover, major histocompatibility complex (MHC) class I tetramer analysis indicated that our inability to detect CVB3-specific CD8(+) T-cell responses could not be explained by the cells being dysfunctional. In contrast to naïve T cells, epitope-specific memory CD8(+) and CD4(+) T cells proliferated markedly, indicating that both of the rCVB3.6-encoded epitopes were presented by their respective MHC molecules in vivo. These data are consistent with the observation that several CVB3 proteins can limit the presentation of viral epitopes on the surface of infected cells and suggest that the level of MHC/peptide complex is sufficient to trigger memory but not naïve T cells. Finally, our findings have implications for the biological significance of cross-priming, a process thought by some to be important for the induction of antiviral CD8(+) T-cell responses.

Quantitative Analysis of Viral RNA in the Murine Heart and Pancreas with Different Concentration of Coxsackievirus B3

OBJECTIVES

We investigated the clinical features, pathologic changes, and viral RNA kinetics in the course of acute and subacute experimental coxsackievirus B3 (CVB3) infection in a murine model.

METHODS

Five-week-old A/J inbred male mice were divided into 5 groups. Four of those groups were inoculated intraperitoneally with 5 x 10(4) (group 1), 1 x 10(5) (group 2), 5 x 10(5) (group 3), or 1 x 10(6) (group 4) PFU of CVB3. Control mice were inoculated with uninfected Vero cell lysate in DMEM. Mice from each group were sacrificed on days 7 or 14 after inoculation.

RESULTS

Bloody diarrhea, earlier weight loss, perianal swelling, and death were correlated with higher viral load. One of ten mice in group 3 and 5 of 10 mice in group 4 died spontaneously between days 4 and 12 after inoculation. All of the remaining 34 mice of infected groups demonstrated extensive pancreatic inflammation. Focal myocarditis developed in only 4 (11.8%) of those 34 subjects. Amylase and creatine kinase activities in the serum were increased in the mice of infected groups. CVB3 RNA was detected in the heart and pancreatic tissue in all subjects. The CVB3 RNA copy number in pancreatic tissue was not correlated with the severity of inflammation.

CONCLUSIONS

In the murine model, viral loading dose determines the clinical features of CVB3-induced infection, and the severity of pancreatitis is not correlated with the viral loading dose or tissue level of viral RNA. .

Lethal enterovirus-induced myocarditis and pancreatitis in a 4-month-old boy

After inconspicuous pregnancy and birth, a 16-year-old mother presented her male baby 5 days later with severe diarrhoea and vomiting. During the following weeks, the child temporarily showed hypotension, hypothermia and increased body temperature, bradyarrythmia with apnoea, continuing diarrhoea, sometimes vomiting and developed signs of pancreatic insufficiency. Due to increasing loss of weight and obviously severe dystrophia, parenteral nutrition had to be initiated. All clinical investigations revealed no underlying disease. Numerous biopsies, mainly from the gastrointestinal tract were taken, but no relevant pathological findings were disclosed. The baby was found lifeless by his mother, 4 months after birth. According to the death certificate, the physicians regarded the lethal outcome as a case of sudden infant death syndrome (SIDS). Histological and immunohistochemical investigations of organ samples revealed signs of myocarditis, pancreatitis and focal pneumonia. Molecularpathological techniques were used to detect enterovirus RNA from tissue samples from the myocardium, liver and pancreas. Enteroviral myocarditis with concomitant pancreatitis was determined as cause of death.

Diabetes acceleration or prevention by a coxsackievirus B4 infection: critical requirements for both interleukin-4 and gamma interferon

Type 1 diabetes acceleration in nonobese diabetic (NOD) mice through coxsackievirus B4 (CVB4) infection requires a preexisting critical mass of autoreactive T cells in pancreatic islets, and in the absence of this insulitic threshold, CVB4 infection leads to long-term disease protection. To understand this acceleration and protection process, we challenged 8- and 12-week-old NOD mice containing a disruption in interleukin-4 (IL-4) or gamma interferon (IFN-gamma) genes (NOD IL-4-/- and NOD IFN-gamma-/-, respectively) with a diabetogenic, pancreatropic Edwards strain of CVB4. The elimination of IL-4 did not alter the rate of insulitis or diabetes development in NOD mice, while the elimination of IFN-gamma delayed these events several weeks. CVB4 infection in 8-week-old mice only significantly accelerated the onset of diabetes in a subset of standard, but not IL-4- or IFN-gamma-deficient, NOD mice. Long-term diabetes protection was established in standard NOD mice as well as in the NOD IFN-gamma-/- mice that did not rapidly develop disease following CVB4 infection at 8 weeks of age. When mice were infected at 12 weeks of age, the onset of diabetes was accelerated in NOD IL-4-/- mice, while neither acceleration nor long-term protection was elicited in NOD IFN-gamma-/- mice. No differences were observed in the kinetics of CVB4 clearance in pancreases from NOD, NOD IL-4-/-, and NOD IFN-gamma-/- mice. Collectively, these results suggest that at the insulitis threshold at which CVB4 infection can first accelerate the onset of diabetes in NOD mice, IL-4 as well as IFN-gamma contributes to this pathogenic process. The protective mechanism against diabetes elicited in NOD mice infected with CVB4 prior to the development of a critical threshold level of insulitis requires neither IL-4 nor IFN-gamma.

Coxsackievirus-induced pancreatitis

In humans, infections with the group B coxsackieviruses (CVBs) range from asymptomatic infections to chronic, debilitating diseases. The CVBs are associated with chronic inflammatory diseases of the pancreas, heart, and central nervous system. A major focus in CVB pathogenesis is to understand the mechanisms by which these viruses cause acute diseases that resolve or acute diseases that progress to chronic diseases. The present review explores CVB infections in the development of acute and chronic pancreatitis. Mouse models of CVB-induced pancreatitis share many features with the human diseases and are providing insight into the multi-faceted processes of pancreatic tissue repair and irreversible tissue destruction. The development and progression of CVB-induced pancreatic inflammatory disease is an extremely complex process, involving both viral and host factors. The review examines the roles of the virus and host in contributing to the disease process. Recent studies of global gene expression during CVB-induced pancreatitis have increased our understanding of host factors that influence the outcome of infection and have highlighted interrelationships among complex biological programs. As we unravel the complexity of the disease process, the information gained will lead to the design of therapeutics that not only prevent the progression of chronic inflammatory disease, but that also restore functionality of affected tissues and organs.

Progression or resolution of coxsackievirus B4-induced pancreatitis: a genomic analysis

Group B coxsackieviruses are associated with chronic inflammatory diseases of the pancreas, heart, and central nervous system. Chronic pancreatitis, which can develop from acute pancreatitis, is considered a premalignant disorder because it is a major risk factor for pancreatic cancer. To explore the genetic events underlying the progression of acute to chronic disease, a comparative analysis of global gene expression during coxsackievirus B4-induced acute and chronic pancreatitis was undertaken. A key feature of acute pancreatitis that resolved was tissue regeneration, which was accompanied by increased expression of genes involved in cell growth, inhibition of apoptosis, and embryogenesis and by increased division of acinar cells. Acute pancreatitis that progressed to chronic pancreatitis was characterized by lack of tissue repair, and the expression map highlighted genes involved in apoptosis, acinoductular metaplasia, remodeling of the extracellular matrix, and fibrosis. Furthermore, immune responses appeared skewed toward development of alternatively activated (M2) macrophages and T helper 2 (Th2) cells during disease that resolved and toward classically activated (M1) macrophages and Th1 cells during disease that progressed. Our hypothesis is that growth and differentiation signals coupled with the M2/Th2 milieu favor acinar cell proliferation, while diminished growth signals and the M1/Th1 milieu favor apoptosis of acinar cells and remodeling/proliferation of the extracellular matrix, resulting in fibrosis.

Multiple viral determinants mediate myopathogenicity in coxsackievirus B1-induced chronic inflammatory myopathy

Mice infected with myopathic coxsackievirus B1 Tucson (CVB1(T)) develop chronic inflammatory myopathy (CIM) consisting of hind limb weakness and inflammation. Amyopathic virus variants are infectious but attenuated for CIM. In this report, viral clones, chimeras, and sequencing were used to identify viral determinants of CIM. Chimeras identified several regions involved in CIM and localized a weakness determinant to nucleotides 2493 to 3200 of VP1. Sequencing of multiple clones and viruses identified five candidate determinants that were strictly conserved in myopathic viruses with one located in the 5' untranslated region (UTR), three in the VP1 capsid, and one in the 3C protease. Taken together, these studies implicate Tyr-87 and/or Val-136 as candidate determinants of weakness. They also indicate that there are at least two determinants of inflammation and one additional determinant of weakness encoded by myopathic CVB1(T).

Lack of islet neogenesis plays a key role in beta-cell depletion in mice infected with a diabetogenic variant of coxsackievirus B4

Group B coxsackieviruses (CVBs) have a well-established association with type 1 diabetes but the mechanism of depletion of beta-cell mass following infection has not yet been defined. In this report we show that the major difference in pathogenesis between the E2 diabetogenic strain of CVB4 and the prototypic JVB strain in SJL mice is not in tropism for islet cells but in the degree of damage inflicted on the exocrine pancreas and the resulting capacity for regeneration of both acinar and islet tissue by the host. Both strains replicated to a high titre in acinar tissue up to day 3 post-infection (p.i.), while the islets of Langerhans were largely spared. However, the pancreas in the JVB-infected animals then regenerated and many small islets were seen throughout the tissue by day 10 p.i. In contrast, the acinar tissue in E2-infected mice became increasingly necrotic until all that remained by day 21 p.i. were large islets containing varying numbers of dead cells, caught up in strands of connective tissue. Surviving beta cells were found to synthesize little insulin, although islet amyloid polypeptide was detected and glucagon synthesis in alpha cells appeared normal or enhanced. Our results suggest that the key to CVB-E2-induced damage lies in the exocrine tissue and prevention of islet neogenesis rather than from direct effects on existing islets.

Enteroviruses and type 1 diabetes

The development of type 1 diabetes mellitus (T1DM) has been linked to exposure to environmental triggers, with Enteroviruses (EV) historically considered the prime suspects. Early serological studies suggested a link between EV infections and the development of T1DM and, though controversial, have been bolstered by more recent studies using more sensitive techniques such as direct detection of the EV genome by RT-PCR in peripheral blood. In this review, we consider the weight of evidence that EV can be considered a candidate trigger of T1DM, using three major criteria: (1) is EV infection associated with clinical T1DM, (2) can EV trigger the development of autoimmunity and (3) what would explain the putative association?

Animal model of alcoholic pancreatitis: role of viral infections

Pancreatitis is clearly associated with alcohol abuse, but only a relatively small percentage of people who abuse alcohol develops obvious pancreatitis. These observations have led to the concept that the development of alcoholic pancreatitis requires cofactors. Although diet and smoking have been studied, a clear cofactor has not been identified. The study results presented in this paper were obtained to determine whether viral infection of the pancreas would be a cofactor for alcoholic pancreatitis similar to the role of hepatitis virus infections in the development of alcoholic liver disease. To test this hypothesis, mice were fed ethanol with a liquid diet protocol and infected with coxsackievirus B3 (CVB3). It was found that consumption of alcohol alone did not result in pancreatitis as determined by serum levels of amylase or histologic changes in the pancreas. Two strains of CVB3 that are tropic for the pancreas were used; a virulent and an avirulent strain. Infection of alcohol-fed animals with the virulent CVB3 strain 28 resulted in a more severe pancreatitis than the pancreatitis noted in control animals. Alcohol-fed mice infected with the avirulent strain (GA) showed severe pancreatitis, whereas the infection of control mice did not result in obvious pathologic effects in the pancreas. This model allows mechanistic studies to define the role of viral infection as a cofactor for alcoholic pancreatitis.

The apoptotic capability of coxsackievirus B3 is influenced by the efficient interaction between the capsid protein VP2 and the proapoptotic host protein Siva

Infections with coxsackievirus B3 (CVB3) are common causes of myocarditis in humans. One detail of CVB3-induced pathogenesis is apoptosis. The interaction between the capsid protein VP2 of the myocardial virus variant CVB3H3 and the proapoptotic host cell protein Siva has recently been observed. In order to characterize the interaction between both proteins more precisely, the binding activity of the CVB3H3 VP2 to Siva was compared to that of the mutant virus CVB3H310A1 VP2. We found that the asparagine at position 165 in VP2 is essential for a stable interaction with Siva influencing also the induction of apoptosis, viral spread, and inflammatory responses in vivo. Furthermore, the specific binding site of Siva to VP2 is located at amino acid positions 118-136. Together, these results show that the interaction between VP2 of CVB3H3 and Siva is a highly specific process involving distinct amino acids on both proteins that most likely influence the outcome of CVB3-caused disease.

Immunogenicity of a foreign peptide expressed within a capsid protein of an attenuated coxsackievirus

The immunogenicity of soluble peptides can be improved by expression within recombinant microorganisms. The immunogenicity of a peptide expressed within a capsid protein of an attenuated coxsackievirus B4 was evaluated. The insertion site was chosen based on its antigenic structure. A foreign peptide was inserted into a region of the VP1 capsid protein that was identified as a T helper cell epitope. A recombinant virus containing ten amino acids of ovalbumin sequence was genetically stable and retained the biological and physical characteristics of the parental virus. The recombinant was able to elicit a T helper cell response against ovalbumin sequences. This study shows, for the first time, that coxsackievirus can be used as an expression vector and that insertion of heterologous peptides into an immunogenic region is a viable strategy for inducing T helper cell responses against foreign sequences. The implications of this work are that the attenuated coxsackievirus variant may be useful as a vaccine vector for expressing T helper cell epitopes that are important in inducing protective immunity.

A therapeutic HIV vaccine using coxsackie-HIV recombinants: a possible new strategy

The ultimate goal in the treatment of HIV-infected persons is to prevent disease progression. A strategy to accomplish this goal is to use chemotherapy to reduce viral load followed by immunotherapy to stimulate HIV-specific immune responses that are observed in long-term asymptomatic individuals. An effective, live, recombinant virus, expressing HIV sequences, would be capable of inducing both CTL and CD4(+) helper T cell responses. To accomplish these goals, the viral vector must be immunogenic yet retain its avirulent phenotype in a T cell-deficient host. We have identified a coxsackievirus variant, CB4-P, that can induce protective immunity against a virulent variant. In addition, the CB4-P variant remains avirulent in mice lacking CD4(+) helper T cells, suggesting that CB4-P may be uniquely suited as a viral vector for a therapeutic HIV vaccine. Two strategies designed to elicit CTL and CD4(+) helper T cell responses were used to construct CB4-P/HIV recombinants. Recombinant viruses were viable, genetically stable, and retained the avirulent phenotype of the parental virus. In designing a viral vector for vaccine development, an issue that must be addressed is whether preexisting immunity to the vector would affect subsequent administration of the recombinant virus. Using a test recombinant, we showed that prior exposure to the parental CB4-P virus did not affect the ability of the recombinant to induce a CD4(+) T cell response against the foreign sequence. The results suggest that a "cocktail" of coxsackie/HIV recombinants may be useful as a therapeutic HIV vaccine.

Coxsackievirus infection of the pancreas: evaluation of receptor expression, pathogenesis, and immunopathology

Coxsackievirus type B (CVB) infection of the pancreas induces a massive cellular infiltrate composed of natural killer cells, T cells, and macrophages and leads to the destruction of exocrine tissue. The physiological manifestations of pancreatic CVB infection are correlated with viral tropism; the virus infects acinar cells but spares the islets of Langerhans. Here we evaluate the mechanisms underlying pancreatic inflammation and destruction and identify the determinants of viral tropism. T-cell-mediated immunopathology has been invoked, along with direct virus-mediated cytopathicity, to explain certain aspects of CVB-induced pancreatic disease. However, we show here that in the pancreas, the extent of inflammation and tissue destruction appears unaltered in the absence of the cytolytic protein perforin; these findings exclude any requirement for perforin-mediated lysis by natural killer cells or cytotoxic T cells in CVB3-induced pancreatic damage. Furthermore, perforin-mediated cytotoxic T-cell activity does not contribute to the control of CVB infection in this organ. In addition, we demonstrate that the recently identified coxsackie-adenovirus receptor is expressed at high levels in acinar cells but is barely detectable in islets, which is consistent with its being a major determinant of virus tropism and, therefore, of disease. However, further studies using various cell lines of pancreatic origin reveal secondary determinants of virus tropism.

A point mutation in VP1 of coxsackievirus B4 alters antigenicity

While coxsackievirus infections have been linked to several autoimmune diseases, very little is known about the immunogenicity of the coxsackieviruses. Using two genetically related variants of coxsackievirus B4, CB4-P and CB4-V, the relationship between virulence and antigenicity was examined. The virulent variant, CB4-V, was shown to be more antigenic than the avirulent CB4-P variant. The increased antigenicity of CB4-V was due to a single amino acid substitution in the VP1 capsid protein (a threonine residue at amino acid position 129), a site that had been previously identified as a major determinant of viral virulence. Thr-129 of VP1 is predicted to lie within a conformational B cell epitope. In addition, a nearby linear B cell epitope spanning residues 68 to 82 of VP1 was identified as a potential serotype-specific, neutralization antigenic site. The linear and conformational B cell epitopes of coxsackievirus B4 may be analogous to antigenic sites 1 and 1B of poliovirus. To address whether the increased antigenicity of CB4-V influenced the severity of disease, mouse strains that differ in their outcome to viral infection were analyzed. Mice that developed the most severe disease and succumbed to infection were more immunoresponsive than mice that survived infection with CB4-V. The data suggest that immune-mediated mechanisms play a role in the severity of CB4-V induced disease.

Inducible Nitric Oxide Synthase Protection Against Coxsackievirus Pancreatitis

Coxsackievirus infection causes myocarditis and pancreatitis in humans. In certain strains of mice, Coxsackievirus causes a severe pancreatitis. We explored the role of NO in the host immune response to viral pancreatitis. Coxsackievirus replicates to higher titers in mice lacking NO synthase 2 (NOS2) than in wild-type mice, with particularly high viral titers and viral RNA levels in the pancreas. Mice lacking NOS have a severe, necrotizing pancreatitis, with elevated pancreatic enzymes in the blood and necrotic acinar cells. Lack of NOS2 leads to a rapid increase in the mortality of infected mice. Thus, NOS2 is a critical component in the immune response to Coxsackievirus infection.

T cells contribute to disease severity during coxsackievirus B4 infection

By using a model of coxsackievirus B4-induced disease, the question of whether tissue damage is due to the virus or to immune-mediated mechanisms was addressed. Both viral replication and T-cell function were implicated in contributing to the severity of disease. Three stages (I to III) of disease, which correspond to periods of high viral titers, low viral titers, and no infectious virus, have been identified. Stage I disease is considered to be primarily the result of viral replication. Immunopathological mechanisms appear to contribute to the severity of stage II and III disease. To investigate the role of T cells in contributing to the severity of disease, viral infection in CD8 knockout (ko) mice and CD4 ko mice was analyzed. CD8 T-cell responses appear to be beneficial during early, viral disease but detrimental in later disease when viral titers are diminishing. CD4 ko mice, unlike the parental strain, survived infection. Viral replication was lower in the CD4 ko mice. Was survival due to decreased viral replication or to the lack of T-helper-cell function? To investigate further the role of T helper cells in contributing to tissue damage, viral infection in two additional ko strains (interleukin-4 [IL-4] ko and gamma interferon ko strains) was examined. A clear correlation between viral replication and the outcome of infection was not observed. The absence of IL-4, which may influence T-helper-cell subset development, was advantageous during early viral disease but deleterious in later disease. The results suggest that T-cell-mediated immunity is both beneficial and detrimental during coxsackievirus B4 infection.

Protection from lethal coxsackievirus-induced pancreatitis by expression of gamma interferon

Coxsackievirus infection causes severe pancreatitis and myocarditis in humans, often leading to death in young or immunocompromised individuals. In susceptible strains of mice, coxsackievirus strain CB4 causes lethal hypoglycemia. To investigate the potential of gamma interferon (IFN-gamma) in protection and clearance of the viral infection, IFN-gamma knockout mice and transgenic (Tg) mice specifically expressing IFN-gamma in their pancreatic beta cells were infected with CB4. Lack of IFN-gamma in mice normally resistant to CB4-mediated disease resulted in hypoglycemia and rapid death. However, expression of IFN-gamma in the beta cells of Tg mice otherwise susceptible to lethal infection allowed for survival and protected them from developing the accompanying hypoglycemia. While all the mice had high levels of viral replication in their pancreata and comparable tissue pathology following viral infection, the Tg mice had significantly lower levels of virus at the peak of infection, significantly higher numbers of activated macrophages before and after infection, and less damage to their acinar tissue. Additionally, despite having increased levels of inducible nitric oxide synthetase (iNOS) expression, treatment of Tg mice with the iNOS inhibitor aminoguanidine did not alter the level of protection afforded by IFN-gamma expression. In conclusion, IFN-gamma protects from lethal coxsackievirus infection by activating macrophages in an iNOS-independent manner.

Construction of pathogenic molecular clones of Aleutian mink disease parvovirus that replicate both in vivo and in vitro

The ADV-G isolate of Aleutian mink disease parvovirus (ADV) replicates permissively in Crandell feline kidney (CRFK) cells but is nonpathogenic for mink, whereas the highly pathogenic ADV-Utah isolate is nonviable in CRFK cells. To assign control of host range in CRFK cells and pathogenicity to specific regions of the ADV genome, we constructed a full-length molecular clone chimeric between ADV-G and ADV-Utah. If either the map unit (MU) 54-65 (clone G/U-5) or MU 65-88 (clone G/U-7) sections were ADV-Utah, viability in CRFK cells was abolished, thus indicating that in vitro host range was controlled by two independent determinants: A in the MU 54-65 segment and B in the MU 65-88 segment. Determinant B could be divided into two subregions, B1 (MU 65-69) and B2 (MU 73-88), neither of which alone could inhibit replication in CRFK cells, an observation suggesting that expression of the B determinant required interaction between noncontiguous sequences. Adult mink of Aleutian genotype inoculated with G/U-8 or G/U-10 developed viremia, antiviral antibody, and histopathological changes characteristic of progressive Aleutian disease. The capsid sequences of G/U-8 and G/U-10 differed from ADV-G at five and four amino acid residues, respectively. Our results suggested that the host range and pathogenicity of ADV are regulated by sequences in the capsid protein gene.