Identification of LFA-1 as a candidate autoantigen in treatment-resistant Lyme arthritis

An open-label, nonrandomized, single-center, prospective extension, clinical trial of booster dose schedules to assess the safety profile and immunogenicity of recombinant outer-surface protein A (OspA) Lyme disease vaccine

BACKGROUND

An efficacy trial of an outer-surface protein A (OspA) Lyme disease vaccine demonstrated tolerability and efficacy against laboratory-confirmed Lyme disease after a primary series of 3 doses at 0, 1, and 12 months.

OBJECTIVES

This extension of the efficacy study assessed the immunogenicity and tolerability of booster vaccinations administered at 24 and/or 36 months after the first vaccination.

METHODS

This open-label, nonrandomized, single-center, prospective extension, clinical trial was conducted in the general community in New Haven, Connecticut, where Lyme disease is endemic. Blood samples (to determine anti-OspA titer) were collected before administration of the booster doses at months 24 and 36, and at 1 and 12 months after each booster dose was administered. Immune response was assessed via total immunoglobulin G (IgG) anti-OspA antibody titers and the proportion of subjects with titers >or=1400 EL.U/mL. Adverse events (AEs) were recorded by the study volunteers on diary cards.

RESULTS

A total of 318 volunteers (173 women and 145 men) received at least 1 booster dose of Lyme disease vaccine, administered at 12 or 24 months after the third vaccination of the primary series (months 24 and 36, in relation to the primary series). Eighty-eight subjects of those who received a month-24 booster received a second booster dose at month 36 (12 months after the first booster). Overall, the mean age of the volunteers was 55 years (range, 19 to 73 years). The demographic characteristics of the groups were similar. Most AEs were limited induration and were rated by investigators and subjects as mild to moderate in severity. Administration of I or 2 booster doses did not elicit any patterns of AEs different from those reported in the efficacy trial. After the first booster dose, all volunteers had an anamnestic response and positive test results for total IgG antibody. Geometric mean titers increased at least 12-fold 1 month after the first booster dose at month 24 or 36. More than 96% of volunteers had titers>1400 EL.U/mL and 100% had titers >400 EL.U/mL (minimum seroprotective level) 1 month after the booster dose at month 24 or 36.

CONCLUSIONS

All booster doses were well tolerated, and the incidence of AEs did not increase after the second booster dose. The immune response generated after the 3-dose primary series waned; booster doses administered at 12 and/or 24 months after the primary series increased antibody levels above seroprotective levels.

Destructive arthritis in vaccinated interferon gamma-deficient mice challenged with Borrelia burgdorferi: modulation by tumor necrosis factor alpha

We found that Borrelia burgdorferi-vaccinated gamma interferon-deficient (IFN-gamma(0)) mice challenged with B. burgdorferi developed prominent chronic destructive osteoarthropathy. When these mice were treated with anti-tumor necrosis factor alpha (TNF-alpha) antibody, the severity of the destructive osteoarthritis was enhanced and affected the mobility of the animals. In addition, extensive swelling of the hind paws occurred. In contrast, treatment of B. burgdorferi-vaccinated, challenged IFN-gamma(0) mice with recombinant TNF-alpha (rTNF-alpha) inhibited the development of arthritis, including swelling of the hind paws. Moreover, treatment of vaccinated, challenged IFN-gamma(0) mice with anti-TNF-alpha inhibited fourfold the production of an antibody that kills B. burgdorferi, while treatment of vaccinated, challenged IFN-gamma(0) mice with rTNF-alpha slightly elevated the level of the borreliacidal antibody. These results suggest that the level of TNF-alpha directly or indirectly regulates the production of borreliacidal antibody and the development of vaccine-induced destructive Lyme osteoarthritis. Studies are in progress to determine the mechanism by which TNF-alpha-dependent cytokines generate the destructive arthritis.

Cutting edge: inflammatory signals drive organ-specific autoimmunity to normally cross-tolerizing endogenous antigen

Links have been observed between infections and the development of autoimmunity. Proposed explanations include activation of self-Ag-bearing APC. Using a model system in which transgenic OVA is expressed in enterocytes, we showed that CD8 T cell recognition of cross-presented Ag in gut-associated lymph nodes was tolerogenic. However, concomitant infection with vesicular stomatitis virus encoding OVA abrogated tolerance and induced disease. We now show that following transfer of naive OT-I T cells, the addition of wild-type vesicular stomatitis virus, oral cholera toxin, or CD40 triggering can induce intestinal disease in transgenic mice. Tissue damage accompanied dramatic increases in cytokine release by activated OT-I cells in the intestine. The data indicated that products of antigenically unrelated infections can combine with cross-presented self-Ags on APC to prime autoaggressiveness, independent of additional Ag release. These results help explain how diverse pathogens, lacking any homology to self-proteins, could be causative agents in induction of organ-specific autoimmunity.

Cyclooxygenase 2 activity modulates the severity of murine Lyme arthritis

Cyclooxygenase (Cox) is a key enzyme in the biosynthetic metabolism of prostaglandins. The inducible isoform of Cox-2 has been implicated in inflammation and its specific inhibition can be used to treat noninfectious inflammatory diseases, such as rheumatoid arthritis. Borrelia burgdorferi, the agent of Lyme disease, can induce joint inflammation. Here we show that B. burgdorferi induced the upregulation of cox-2 gene expression in murine joints at the onset of arthritis in infected mice. The level of mRNA expression correlated with the degree of inflammation. The specific inhibition of Cox-2 diminished the degree of joint inflammation, without affecting B. burgdorferi-specific antibody or cytokine responses. Cox-2 activity is therefore associated with the genesis of infectious arthritis caused by B. burgdorferi.

T cells primed by Leishmania major infection cross-react with alloantigens and alter the course of allograft rejection

Alloreactive T lymphocytes can be primed through direct presentation of donor MHC:peptide complexes on graft cells and through indirect presentation of donor-derived determinants expressed by recipient APCs. The large numbers of determinants on an allograft and the high frequency of the alloreactive repertoire has further led to speculation that exposure to environmental Ags may prime T cells that cross-react with alloantigens. We sought to develop a model in which to test this hypothesis. We found that CD4(+) T cells obtained from C57BL/6 (B6) mice that clinically resolved Leishmania major infection exhibited statistically significant cross-reactivity toward P/J (H-2(p)) Ags compared with the response to other haplotypes. B6 animals that were previously infected with L. major specifically rejected P/J skin grafts with second set kinetics compared with naive animals. Although donor-specific transfusion combined with costimulatory blockade (anti-CD40 ligand Ab) induced prolonged graft survival in naive animals, the same treatment was ineffective in mice previously infected with L. major. The studies demonstrate that cross-reactive priming of alloreactive T cells can occur and provide direct evidence that such T cells can have a significant impact on the outcome of an allograft. The results have important implications for human transplant recipients whose immune repertoires may contain cross-reactively primed allospecific T cells.

Effector CD4 cells are tolerized upon exposure to parenchymal self-antigen

It has long been established that exposure of naive T cells to specific Ag in the absence of adjuvant leads to tolerization. Nonetheless, the potential of effector CD4 cells to be tolerized has been less well characterized. To address this issue, we have used an adoptive transfer system in which naive TCR transgenic hemagglutinin (HA)-specific CD4(+) T cells are initially primed to express effector function upon exposure to an immunogenic recombinant vaccinia virus expressing HA, and then exposed to forms of HA that are tolerogenic for naive CD4 cells. HA-specific effector CD4 cells residing in both the spleen as well as in two separate nonlymphoid tissues were tolerized upon exposure to high doses of exogenous soluble HA peptide. Additionally, tolerance could also be induced by bone marrow-derived APCs that cross-present parenchymally derived self-HA. Thus, effector CD4 cells are susceptible to similar tolerogenic stimuli as are naive CD4 cells.

IFNgamma production in peripheral blood of early Lyme disease patients to hLFAalphaL (aa326-345)

BACKGROUND

It has been proposed that outer surface protein A (OspA) of Borrelia burgdorferi sensu stricto contains a T helper 1 (Th1) cell epitope that could play a role in an autoimmune response to hLFA1.

METHODS

We used two peptides, hLFAalphaL (aa326-345) and Borrelia burgdorferi OspAB31 (aa164-183), as stimulating antigens to measure Th1 proinflammatory IFNgamma cytokine production in peripheral blood of Lyme disease patients presenting with EM without history of arthritis, as well as in peripheral blood of healthy individuals.

RESULTS

IFNgamma responses to hLFA1 peptide were observed in 11 of 19 Lyme disease patients and in 3 of 15 healthy controls. In contrast, only 2 of 19 of the Lyme disease patients and none of the controls responded to the homologous OspAB31 peptide.

CONCLUSIONS

IFNgamma was produced in response to stimulation with peptide hLFAalphaL (aa326-345) in peripheral blood of 58% of patients with early Lyme disease without signs of arthritis, as well as in peripheral blood of 20% of healthy individuals, but not in response to stimulation with the homologous OspAB31 (aa164-183) peptide (p < 0.05). Our results suggest that reactivity to the hLFA1 peptide in peripheral blood may be the result of T cell degeneracy.

Enhancing antitumor immune responses: intracellular peptide delivery and identification of MHC class II-restricted tumor antigens

The importance of T-cell-mediated antitumor immunity has been demonstrated in both animal models and human cancer therapy. The identification of major histocompatibility complex (MHC) class I-restricted tumor antigens has generated a resurgence of interest in immunotherapy for cancer. However, recent studies suggest that therapeutic strategies that have mainly focused on the use of CD8+ T cells (and MHC class I-restricted tumor antigens) may not be effective in eliminating cancer cells in patients. Novel strategies have been developed for enhancing T-cell responses against cancer by prolonging antigen presentation of dendritic cells to T cells and the inclusion of MHC class II-restricted tumor antigens. identification of MHC class II-restricted tumor antigens, which are capable of stimulating CD4+ T cells, not only aids our understanding of the host immune responses against cancer antigens, but also provides opportunities for developing effective cancer vaccines.

Disease severity in a murine model of lyme borreliosis is associated with the genotype of the infecting Borrelia burgdorferi sensu stricto strain

The pathogenicity of Borrelia burgdorferi sensu stricto clinical isolates representing 2 distinct ribosomal DNA spacer restriction fragment-length polymorphism genotypes (RSTs) was assessed in a murine model of Lyme disease. B. burgdorferi was recovered from 71.5% and 26.6% of specimens from mice infected with RST1 and RST3 isolates, respectively (P<.0001). The average ankle diameter and histologic scores for carditis and arthritis were significantly higher after 2 weeks of infection among mice infected with RST1 isolates than among those infected with RST3 isolates (P<.001). These clinical manifestations were associated with larger numbers of spirochetes in target tissues but not with the serum sensitivity of the individual isolates. Thus, the development and severity of disease in genetically identical susceptible hosts is determined mainly by the pathogenic properties of the infecting B. burgdorferi isolate. The RST1 genotype is genetically homogeneous and thus may represent a recently evolved clonal lineage that is highly pathogenic in humans and animals.

Functional activation of myelin-specific T cells by virus-induced molecular mimicry

Molecular mimicry is the process by which T cells activated in response to determinants on an infecting microorganism cross-react with self epitopes, leading to an autoimmune disease. Normally, infection of SJL/J mice with the BeAn strain of Theiler's murine encephalomyelitis virus (TMEV) results in a persistent CNS infection, leading to a chronic progressive, CD4(+) T cell-mediated demyelinating disease. Myelin damage is initiated by T cell responses to virus persisting in CNS APCs, and progressive demyelinating disease (50 days postinfection) is perpetuated by myelin epitope-specific CD4(+) T cells activated by epitope spreading. We developed an infectious model of molecular mimicry by inserting a sequence encompassing the immunodominant myelin epitope, proteolipid protein (PLP) 139-151, into the coding region of a nonpathogenic TMEV variant. PLP139-TMEV-infected mice developed a rapid onset paralytic inflammatory, demyelinating disease paralleled by the activation of PLP139-151-specific CD4(+) Th1 responses within 10-14 days postinfection. The current studies demonstrate that the early onset demyelinating disease induced by PLP139-TMEV is the direct result of autoreactive PLP139-151-specific CD4(+) T cell responses. PLP139-151-specific CD4(+) T cells from PLP139-TMEV-infected mice transferred demyelinating disease to naive recipients and PLP139-151-specific tolerance before infection prevented clinical disease. Finally, infection with the mimic virus at sites peripheral to the CNS induced early demyelinating disease, suggesting that the PLP139-151-specific CD4(+) T cells could be activated in the periphery and traffic to the CNS. Collectively, infection with PLP139-151 mimic encoding TMEV serves as an excellent model for molecular mimicry by inducing pathologic myelin-specific CD4(+) T cells via a natural virus infection.

Pathogenesis of autoimmune hepatitis

Autoimmune hepatitis is initiated by CD4 T cells that recognize self-antigen. The effector cells differentiate into functional phenotypes according to cytokines in the microenvironment and the nature of the triggering antigen. Hepatocytes can express class II molecules and present antigenic peptides through a bystander mechanism. NKT cells reside in the normal liver but may be involved in liver cell damage possibly through the expression of Fas ligand. Autoantibodies may also participate in the process by complexing with antigen on the hepatocyte membrane surface and by interacting with mononuclear cells with Fc receptors. Molecular mimicry generates cross-reactivities that predispose the immune system to cross-react with self-antigens. Multiple exposures to pathogens with antigenic similarities may prime a cross-reactive subset of T cells in the genetically predisposed host. Autoimmunity against one self-antigen may then spread through molecular mimicry to other homologous self-antigens and may lead to overt autoimmune disease. Anatomically distant tissues may also become involved as autoreactive T cells that had been activated in one organ expand and infiltrate other organs that express similar epitopes.

Host-pathogen interactions and the pathogenesis of murine Lyme disease

Lyme disease results from persistent infection with the spirochete Borrelia burgdorferi. A combination of bacterial factors and host factors contributes to the development of inflammatory disease. Studies from the past year have provided insight into both sides of this host-pathogen interplay. We now have a better appreciation of the bacterial genes and products that are involved in pathology and the components of the host response that participate in disease development.

Reactive arthritis or chronic infectious arthritis?

Microbes reach the synovial cavity either directly during bacteraemia or by transport within lymphoid cells or monocytes. This may stimulate the immune system excessively, triggering arthritis. Some forms of ReA correspond to slow infectious arthritis due to the persistence of microbes and some to an infection triggered arthritis linked to an extra-articular site of infection.

Development of autoimmunity in Lyme arthritis

Treatment-resistant Lyme arthritis (TRLA) develops in 10% of Lyme arthritis patients and is characterized by continuous joint inflammation that does not resolve with antibiotic therapy. TRLA is associated with HLA-DRB1*0401 and related alleles, as well as with an immune response to the Borrelia burgdorferi (Bb) outer surface protein A (OspA). The immunodominant epitope of OspA in the context of HLA-DRB1*0401 corresponds to amino acids 165-173 (OspA165-173). The human Lymphocyte Function Antigen-1 (hLFA1alpha) contains a peptide with homology to OspA165-173. Treatment-resistant Lyme arthritis patients' T cells, cloned based on their ability to bind OspA165-173-loaded HLA-DRB1*0401 tetramers, respond to OspA and hLFA1alpha with a different cytokine profile, suggesting that hLFA1alpha acts as a partial agonist with a potential role in the perpetuation of joint inflammation.

Cost-effectiveness analysis of the Lyme disease vaccine

OBJECTIVE

A vaccine for Lyme disease was approved in 1998 for use in the US. Given the high cost of the vaccine, the low risk of Lyme disease in many areas, and the largely curable nature of the disease, the cost-effectiveness of the vaccine in various risk groups is uncertain. This study was undertaken to examine the cost-effectiveness of the Lyme disease vaccine and the factors that influence its cost-effectiveness.

METHODS

We constructed a Markov decision-analysis model to evaluate the clinical effectiveness and cost-effectiveness of the Lyme disease vaccine in populations at various levels of risk for the disease. The probabilities of clinical events and costs were estimated from reports in the literature. Sensitivity analyses assessed the impact of potential variations of parameters on model results.

RESULTS

At the average national incidence of Lyme disease (0.0067%), the incremental cost-effectiveness of vaccination was approximately $1,600,000 per case averted when a yearly booster was given for 10 years after the standard initial vaccination regimen of 3 inoculations at 0, 1, and 12 months. For populations with an annual Lyme disease incidence of 1% (the incidence in several well-defined geographical areas of the US), the incremental cost-effectiveness was approximately $9,900 per case averted. Disease incidence had to exceed 10% before vaccination with yearly boosters became both more effective and more cost saving than no vaccination.

CONCLUSION

The Lyme disease vaccine is cost-effective only for individuals who live in areas where Lyme disease is endemic and who are frequently exposed to ticks.

[Lyme disease--new findings on its physiopathology, diagnosis, therapy and prevention]

INTRODUCTION

Lyme disease is a tick-borne disease caused by a spirochete Borrelia burgdorferi, which manifests as a multisystem disease of the skin, nervous system, heart and joints. Recently it is the most common vector-borne disease in Yugoslavia.

NEW EPIDEMIOLOGICAL STUDIES

New epidemiological studies revealed that ticks can occasionally be infected not only by Borrelia burgdorferi, but also by some other microbes that can cause diseases in humans. Recently discovered the variable major protein-like sequence, antigenic variation of B. burgdorferi B 31 partly explains the ability of this organism to evade an active immune response. A key role in development of clinical symptoms associated with lyme disease belongs to the connection with ability of B. burgdorferi to induce and activate metallopeptidases and fibrinolytic enzymes, leading to extracellular matrix destruction.

DIAGNOSIS AND TREATMENT

Diagnosis of Lyme borreliosis is made on the basis of clinical picture, exposure to ticks in endemic areas and serologic confirmation. It seems that polymerase chain reaction has little role in detection of B. burgdorferi in urine, blood, and spinal fluid samples, but it is most useful in evaluating the effectiveness of antibiotic therapy of Lyme arthritis. Infectious Diseases Society of America had prepared new guidelines for selective treatment of Lyme disease. Vaccination is still the best way of prevention for people living in high-risk areas.

Genomics approaches to drug discovery

New approaches to drug discovery have come about in recent years as a result of important advances in genomics and bioinformatics. The availability of genome-scale sequence data, the development of new tools for high-throughput gene expression monitoring, and improvements in the ability to analyze large data sets have revolutionized the field. In this article, we discuss three applications of genomics data in the drug discovery process: target discovery, prodrug strategies, and vaccine development.

[Rheumatologic manifestations of Lyme borreliosis]

PURPOSE

Lyme borreliosis is a multisystemic infection caused by the spirochaete Borrelia burgdorferi. In European endemic areas like northeast France, articular manifestations are, after neuroborreliosis, the most frequent extra-cutaneous features observed. Among the pathogenic species of Borrelia, Borrelia burgdorferi sensu stricto is the most frequently identified during Lyme arthritis, but others species also seem to be involved.

CURRENT KNOWLEDGE AND KEY POINTS

The diagnosis of Lyme arthritis is usually based on combined clinical data and serological laboratory tests. In atypical forms, detection of bacterial DNA could be useful. While mechanisms involved in acute Lyme arthritis are beginning to be better understood, the pathogenesis of chronic arthritis, which concerns about 10% of the patients, remains unknown. Two hypotheses are proposed to explain the prolonged evolution of the articular disease: a chronic persistence of Borrelia burgdorferi, which evades the host immune system within the joint and/or an autoimmune mechanism by molecular mimicry. The antibiotic therapy is codified in acute arthritis, but is not really adapted in chronic Lyme arthritis or post-Lyme syndrome.

FUTURE PROSPECTS AND PROJECTS

To prevent the disease, the vaccine available in the United States does not offer complete protection and is not useful in Europe since the species heterogeneity is important for the outer surface protein A. A better understanding of Lyme disease pathogenesis can subsequently lead to new therapeutic or preventive approaches.

Late and chronic Lyme disease

This article reviews the late and chronic manifestations of Lyme disease. Special attention is given to the chronic manifestations of the disease, detailing its pathogenesis, clinical spectrum, and laboratory criteria for the diagnosis. Based on experimental evidence and experience, approaches to the successful treatment of the late and chronic disease are outlined. Much additional work is needed to improve the understanding of the underlying pathophysiology of the disease, its diagnosis and treatment.

Neurologic aspects of Lyme disease

Lyme disease has emerged as a major infection with frequent neurologic manifestations. These manifestations probably reflect several predominantly indirect pathogenetic mechanisms and involve host, vector, and organism factors. With early diagnosis and appropriate antibiotic treatment, patients do well. Because culture is not reliable, diagnosis has relied on positive serology to document exposure. Serology should improve as second-generation assays become available. Although there is a preventive vaccine based on the lipoprotein OspA, newer vaccines in development may prove more desirable. Lyme disease provides a valuable model to study how infectious pathogens cause neurologic disease.

T cell epitopes of human myelin oligodendrocyte glycoprotein identified in HLA-DR4 (DRB1*0401) transgenic mice are encephalitogenic and are presented by human B cells

Myelin oligodendrocyte glycoprotein (MOG) is an Ag present in the myelin sheath of the CNS thought to be targeted by the autoimmune T cell response in multiple sclerosis (MS). In this study, we have for the first time characterized the T cell epitopes of human MOG restricted by HLA-DR4 (DRB1*0401), an MHC class II allele associated with MS in a subpopulation of patients. Using MHC binding algorithms, we have predicted MOG peptide binding to HLA-DR4 (DRB1*0401) and subsequently defined the in vivo T cell reactivity to overlapping MOG peptides by testing HLA-DR4 (DRB1*0401) transgenic mice immunized with recombinant human (rh)MOG. The data indicated that MOG peptide 97-108 (core 99-107, FFRDHSYQE) was the immunodominant HLA-DR4-restricted T cell epitope in vivo. This peptide has a high in vitro binding affinity for HLA-DR4 (DRB1*0401) and upon immunization induced severe experimental autoimmune encephalomyelitis in the HLA-DR4 transgenic mice. Interestingly, the same peptide was presented by human B cells expressing HLA-DR4 (DRB1*0401), suggesting a role for the identified MOG epitopes in the pathogenesis of human MS.

Cellular and humoral immune responses to Borrelia burgdorferi antigens in patients with culture-positive early Lyme disease

We determined cellular and humoral immune responses to Borrelia burgdorferi lysate and to recombinant flagellin (FlaB), OspC, and OspA in acute- and convalescent-phase samples from 39 culture-positive patients with erythema migrans and in 20 healthy control subjects. During the acute illness, a median of 4 days after the onset of erythema migrans, 51% of the patients had proliferative cellular responses and 72% had antibody responses to at least one of the borrelial antigens tested. During convalescence, at the conclusion of antibiotic therapy, 64% of the patients had proliferative cellular reactivity and 95% had antibody reactivity with at least one of the spirochetal antigens tested. In both acute- and convalescent-phase samples, cellular immune responses were found as frequently to OspA as to OspC and FlaB. Although antibody responses were also frequently seen to OspC and FlaB, only a few patients had marginal antibody reactivity with OspA. The percentage of patients with proliferative responses was similar in those with clinical evidence of localized or disseminated infection, whereas humoral reactivity was found more often in those with disseminated disease. We conclude that cellular and humoral responses to B. burgdorferi antigens are often found among patients with early Lyme disease. In contrast with the other antigens tested, cellular but not humoral reactivity was often found with OspA.

The autoimmune pathogenesis of rheumatoid arthritis: role of autoreactive T cells and new immunotherapies

OBJECTIVES

To review the role of T lymphocytes in the pathogenesis of rheumatoid arthritis (RA) and discuss the relevance of the components of the trimolecular complex (synovial T cells, autoantigens, and antigen presenting cells) in the pathogenic autoimmune response in RA.

METHODS

Currently available experimental data are combined into a hypothetical pathway that may explain some of the events in the RA process. The literature regarding the potential therapeutic strategies that interfere with specific components of the trimolecular complex and other mediators are discussed briefly.

RESULTS

T cells are activated in the peripheral blood, cross the endothelial cell wall, and migrate into the joints. Once in the synovial joints, T cells are reactivated by cross-reactive antigens and clonally expand. Clonally expanded T cells accumulate in the diseased joint and secrete proinflammatory cytokines that attract and activate other cells, such as monocytes and macrophages. Treatment with anti-CD4 monoclonal antibodies or anticytokine agents that prevents antigen presentation and/or T-cell activation were effective in RA. Other therapies, such as T-cell vaccination and T-cell receptor peptide vaccination targeting autoreactive T cells, showed clinical improvement, suggesting a pathogenic role of these lymphocytes in disease progression.

CONCLUSION

T cells appear to be actively involved in the pathogenesis of RA, but several parts of the pathway are hypothetical and further research is needed.

Future vaccines: recent advances and future prospects

The 20th century has witnessed the introduction of over 20 vaccines that prevent or even conquer diseases such as smallpox, polio, and measles. The continued threat of infectious diseases demands the creation of many more vaccines, especially against common respiratory and gastrointestinal pathogens. Thanks to recent advances in molecular biology, immunology, and adjuvant technology, the next decade likely will bring a vaccine for HIV/AIDS also. We enter the 21st century with a tempered optimism, proud of past achievements, but mindful of the challenges that lie ahead.

Genetic control of susceptibility to experimental Lyme arthritis is polygenic and exhibits consistent linkage to multiple loci on chromosome 5 in four independent mouse crosses

C3H/He mice infected with Borrelia burgdorferi develop severe arthritis and are high antibody responders, while infected C57BL/6 and BALB/c mice develop mild arthritis and less robust humoral responses. Genetic analysis using composite interval mapping (CIM) on reciprocal backcross populations derived from C3H/HeN and C57BL/6N or C3H/HeJ and BALB/cAnN mice identified 12 new quantitative trait loci (QTL) linked to 10 murine Lyme disease phenotypes. These QTL reside on chromosomes 1, 2, 4, 6, 7, 9, 10, 12, 14, 15, 16, and 17. A reanalysis of an F(2) intercross between C57BL/6N and C3H/HeN mice using CIM identified two new QTL on chromosomes 4 and 15 and confirmed the location of seven previously identified loci. Two or more experimental crosses independently verified six QTL controlling phenotypes after B. burgdorferi infection. Additionally, Bb2 on chromosome 5 was reproduced in four experimental populations and was linked to the candidate locus Cora1. Evidence of four distinct QTL residing within the 30-cM region of chromosome 5 encompassing the previously mapped Bb2 and Bb3 loci was shown by CIM. Interestingly, some alleles contributing to susceptibility to Lyme arthritis were derived from C57BL/6N and BALB/cAnN mice, showing that disease-resistant strains harbor susceptibility alleles.

Lyme disease: an update

Lyme disease is a multisystem illness caused by the spirochete Borrelia burgdorferi, and it is the most common vector-borne illness in the United States. Lyme disease is also endemic in Europe and Asia. There have been major advances in the field since the disease was first described, including the sequencing of the B. burgdorferi genome; an increase in understanding of the interactions among the spirochete, the tick, and the mammalian host; new and improved laboratory tests; and a vaccine for prevention of the disease. Still, the diagnosis of Lyme disease remains based on history and clinical findings, supplemented by careful use of laboratory tests, and requires that the physician be familiar with the disease's clinical manifestations and the shortcomings of the available diagnostic tests.

Recent advances in the diagnosis of Lyme disease

Diagnosis of human Lyme borreliosis is usually based on serology, which has a number of pitfalls. In the early phase of the disease serology can still be negative, whereas false-positive results are also common. The interpretation of confirmatory Western blot tests is not always easy. Furthermore, routine serology cannot discriminate between active and past infection. In addition, recombinant antigens are being introduced to improve serologic tests. New developments in the diagnosis of Lyme disease are the development of PCR tests. This review gives an overview of the molecular diagnostic possibilities of Lyme borreliosis, mainly by PCR, and describes some interesting possibilities for future serology.

Active immunization in the United States: developments over the past decade

The Centers for Disease Control and Prevention has identified immunization as the most important public health advance of the 20th century. The purpose of this article is to review the changes that have taken place in active immunization in the United States over the past decade. Since 1990, new vaccines have become available to prevent five infectious diseases: varicella, rotavirus, hepatitis A, Lyme disease, and Japanese encephalitis virus infection. Improved vaccines have been developed to prevent Haemophilus influenzae type b, pneumococcus, pertussis, rabies, and typhoid infections. Immunization strategies for the prevention of hepatitis B, measles, meningococcal infections, and poliomyelitis have changed as a result of the changing epidemiology of these diseases. Combination vaccines are being developed to facilitate the delivery of multiple antigens, and improved vaccines are under development for cholera, influenza, and meningococcal disease. Major advances in molecular biology have enabled scientists to devise new approaches to the development of vaccines against diseases ranging from respiratory viral to enteric bacterial infections that continue to plague the world's population.

Lyme disease and current aspects of immunization

Lyme disease is a tick-borne multisystem disease that affects primarily the skin, nervous system, heart and joints. At least three species of Borrelia burgdorferi sensu lato, namely Borrelia burgdorferi sensu stricto, Borrelia garinii, and Borrelia afzelii, can cause the disease. This review will focus mainly on the pathophysiology of Lyme arthritis, the long-term outcome of Lyme disease, and the recently licensed vaccine against Lyme disease.

Autoimmunity provoked by infection: how good is the case for T cell epitope mimicry?

Autoimmune diseases remain one of the mysteries that perplex immunologists. What makes the immune system, which has evolved to protect an organism from foreign invaders, turn on the organism itself? A popular answer to this question involves the lymphoid network's primordial function: autoimmunity is a by-product of the immune response to microbial infection. For decades there have been tantalizing associations between infectious agents and autoimmunity: beta-hemolytic streptococci and rheumatic fever; B3 Coxsackieviruses and myocarditis; Trypanosoma cruzi and Chagas' disease; diverse viruses and multiple sclerosis; Borrelia burgdorfii and Lyme arthritis; and B4 Coxsackievirus, cytomegalovirus or rubella and type 1 diabetes, to name the most frequently cited examples. In addition, animal models have provided direct evidence that infection with a particular microbe can incite a particular autoimmune disease. Nonetheless, many of the associations appear less than convincing and, even for those that seem to be on solid footing, there is no real understanding of the underlying mechanism(s).

Autoimmune disease: why and where it occurs

Autoimmune disease is controlled by genetic and environmental factors. Both of these affect susceptibility to autoimmunity at three levels: the overall reactivity of the immune system, the specific antigen and its presentation, and the target issue.

Update on Lyme Disease Vaccine: Focus on Dosing and Adverse Events

With the rapid pace of immunologic research, it is more important than ever for readers to understand rational immunodiagnosis, immuno-prophylaxis, and immunotherapy. This column is intended to help you ensure proper immunologic drug use in your practice.

Molecular mimicry and autoimmune liver disease: virtuous intentions, malign consequences

The pathogenesis of autoimmune liver disease and autoimmunity associated with chronic viral hepatitis remains poorly understood. One of the major hurdles to a deeper understanding of these pathological processes is the absence of clearly defined inductive mechanisms, which, if identified and characterised, could guide clinical strategies for their prevention or allow therapeutic intervention. Molecular mimicry leading to crossreactive autoimmune responses has gained strong experimental support in the past decade. A fundamental premise of this hypothesis is the involvement of a mimicking environmental trigger. In view of the numerous viral and bacterial agents epidemiologically linked to autoimmune liver diseases, we and others have proposed molecular mimicry to be an important mechanism in these diseases. We also propose similar crossreactive mechanisms to operate in the generation of autoimmunity in viral hepatitis. This review focuses on molecular mimicry at the level of the B-cell, as few data on T-cell crossreactivity in liver disease are thus far available.

A virus-induced molecular mimicry model of multiple sclerosis

Molecular mimicry is the process by which virus infection activates T cells that are cross-reactive with self antigens. Infection of SJL/J mice with the neurotropic picornavirus Theiler's murine encephalomyelitis virus (TMEV) leads to a progressive CD4(+) T cell-mediated demyelinating disease similar to multiple sclerosis. To study the potential of virus-induced molecular mimicry to initiate autoimmune demyelination, a nonpathogenic TMEV variant was engineered to encode a 30-mer peptide encompassing the immunodominant encephalitogenic myelin proteolipid protein (PLP139-151) epitope. Infection with the PLP139-151-encoding TMEV led within 10-14 days to a rapid-onset paralytic demyelinating disease characterized by PLP139-151-specific CD4(+) Th1 responses; insertion of a non-self ovalbumin sequence led to restoration of the normal late-onset disease. Early-onset disease was also observed in mice infected with a TMEV encoding PLP139-151 with an amino acid substitution at the secondary T cell receptor (TCR) contact residue (H147A), but not in mice infected with TMEV encoding a PLP139-151 substitution at the primary TCR contact (W144A). Most significantly, mice infected with TMEV encoding a Haemophilus influenzae mimic peptide, sharing only 6 of 13 amino acids with PLP139-151, displayed rapid-onset disease and developed cross-reactive PLP139-151-specific CD4(+) Th1 responses. To our knowledge, this is the first study showing that a naturally infectious virus encoding a myelin epitope mimic can directly initiate organ-specific T cell-mediated autoimmunity.

Bacteria-Triggered reactive arthritis: implications for antibacterial treatment

Reactive arthritis (ReA) is definitely caused by an infection. Several observations suggest that the triggering microbe may persist in the tissues of the patient for a prolonged time. The obvious conclusion is to consider antibacterial treatment. In two instances antibacterial agents are of definite value: in the primary and secondary prevention of rheumatic fever and for early eradication of Borrelia burgdorferi in order to prevent development of the arthritis associated with Lyme disease. Altogether, clinical and experimental data exist to indicate that if antibacterial treatment of ReA can be started very early during the pathogenetic process, the disease can be prevented or the prognosis improved. In fully developed ReA, the value of antibacterial agents is less certain. All available evidence indicates that short term antibacterial treatment has no effect on the prognosis and final outcome of ReA, and the results with long term administration of antibacterials are also overall poor. In some instances sulfasalazine appears useful, rather as a result of its antirheumatic effect or influence on an underlying inflammatory bowel disease than its action as an antibacterial agent. Tetracyclines have also been found to have an effect on ReA, but again, this is probably due to their anti-inflammatory action rather than any antibacterial effect.

Analysis of the relationship between viral infection and autoimmune disease

The clinical association between viral infection and onset or exacerbation of autoimmune disorders remains poorly understood. Here, we examine the relative roles of molecular mimicry and nonspecific inflammatory stimuli in progression from infection to autoimmune disease. Murine herpes virus 1 (HSV-1 KOS) infection triggers T cell-dependent autoimmune reactions to corneal tissue. We generated an HSV-1 KOS point mutant containing a single amino acid exchange within the putative mimicry epitope as well as mice expressing a TCR transgene specific for the self-peptide mimic to allow dissection of two pathogenic mechanisms in disease induction. These experiments indicate that viral mimicry is essential for disease induction after low-level viral infection of animals containing limited numbers of autoreactive T cells, while innate immune mechanisms become sufficient to provoke disease in animals containing relatively high numbers of autoreactive T cells.

Prevention of Lyme disease: a review of the evidence

The Healthy People 2010 public health goals targeted a 44% decrease in the incidence of Lyme disease, the most commonly reported tick-borne illness in the United States. To review Lyme disease prevention, clinical trials, epidemiological and experimental studies, and predictive models were evaluated. Geographic distribution of ixodid vectors and local landscape predict Lyme disease risk. Density of infected ticks correlates with incidence and prevalence of Lyme disease, but risk quantitation is made uncertain by tick aggregation and inability to predict tick-human interactions. Outdoor activities are inconsistently or weakly associated with risk, and most infections likely occur in residential areas during routine activities. Tick control (burning or removing vegetation, acaricide use, and deer elimination) reduces Ixodes scapularis populations by up to 94%, and acaricide application to wildlife decreases nymphal I scapularis populations by up to 83%. The effect of these strategies on incidence of Lyme disease in humans is unknown. Studies show that only 40% to 50% of adults take precautions against tick bites even when they are aware of Lyme disease. Effective protection afforded by personal precautions (wearing protective clothing, avoiding ticks, and using insect repellant) has not been shown prospectively. Antimicrobial prophylaxis of tick bites is not warranted. Clinical trials showed vaccines containing recombinant OspA of Borrelia burgdorferi to be efficacious and well tolerated. Currently, vaccination is the only empirically demonstrated method to prevent Lyme disease. The best evidence supports prevention efforts focused on practices that encourage immunization, Lyme disease awareness, and possibly treatment of deer.

Safety and immunogenicity of a recombinant Borrelia burgdorferi outer surface protein A vaccine against lyme disease in healthy children and adolescents: a randomized controlled trial

OBJECTIVE

A recombinant lipoprotein outer surface protein A (OspA) Lyme disease (LD) vaccine (LYMErix) has been shown to be safe and effective in preventing LD in adults and in adolescents 15 years of age and older. Children are at risk for developing LD. This clinical study was conducted to address the safety and immunogenicity of LD vaccine in children 4 to 18 years of age.

METHODS

A randomized, placebo-controlled clinical trial was conducted at 17 investigational sites in Lyme-endemic areas in the United States. Immunogenicity data from this study also were compared with data obtained from the adult efficacy study. A total of 4090 healthy children and adolescents (age range: 4-18; mean age: 10.4 years) were randomized; 4087 were vaccinated, and a subset of 301 children participated in the immunogenicity analysis. Children were randomized to receive either 30 microgram of LD vaccine (N = 3063) or placebo (N = 1024) on a 0, 1, 12-month schedule. Safety assessments evaluated both solicited (local: redness, swelling, and pain; general: fever, headache, fatigue, arthralgia, and rash) and unsolicited adverse events. Serum specimens were collected at month 0 or month 2, and months 6, 12, and 13.

RESULTS

Solicited reactogenicity data revealed a higher incidence of local injection site reactions and general symptoms (fever, headache, fatigue, and arthralgia) in vaccine than placebo recipients. The majority of events were limited in duration (mean: 2-3 days) and were mild to moderate in severity. The total IgG anti-OspA geometric mean titer (GMT) in the pediatric vaccine recipients at month 13 was as good as and statistically higher than the GMT in the adult cohort at month 13 (27 485 enzyme-linked immunosorbent assay units [EL.U]/mL vs 8216 EL.U /mL). All of the pediatric vaccine recipients attained a level of antibody concentration >/=1400 EL.U/mL (proposed seroprotective level) compared with 90% of adults attaining levels >/=1400 EL.U/mL in the efficacy trial.

CONCLUSIONS

LD vaccine administered on a 0, 1, 12-month schedule generally is well tolerated and immunogenic in children 4 to 18 years of age. The safety profile consists of mild to moderate local injection site reactions and flu-like symptoms of limited duration and did not worsen with subsequent injections. IgG GMT at month 13 was threefold higher than the month 13 GMT obtained in the adult efficacy study. This higher immune response in children should provide protection against LD.

Impact of genotypic variation of Borrelia burgdorferi sensu stricto on kinetics of dissemination and severity of disease in C3H/HeJ mice

Various genotypes of Borrelia burgdorferi sensu stricto have been previously identified among a large collection of isolates cultured from patients with Lyme disease in the United States. Furthermore, association of specific genotypes with hematogenous dissemination early in the disease course has been observed. The present study assessed kinetics of spirochete dissemination and disease severity in C3H/HeJ mice infected with two different genotypes of B. burgdorferi. Spirochete load in plasma and ear and other tissue samples of infected mice was measured by quantitative PCR, and these data were compared to those obtained by culture and histopathologic analysis. In mice infected with isolate BL206 (a type 1 strain), the peak number of spirochetes was observed in plasma between day 4 and 7, in heart and ear tissue on day 14, and in joints on day 28 postinoculation. There was a correlation between the peak number of spirochetes in plasma on day 4 or 7 and that in ear biopsy and joint specimens on day 14. By contrast, spirochete burdens in plasma of mice infected with isolate B356 (a type 3 strain) were 16- and 5-fold lower than those of BL206-infected mice on days 7 and 14 of infection, respectively. Similarly, approximately 6- and 13-fold fewer spirochetes were detected in the heart tissues of B356-infected mice compared to BL206-infected mice. Histopathologically, severe arthritis and aortitis were noted only in mice infected with isolate BL206. Spirochete dissemination and disease severity vary significantly in mice infected with distinct genotypes of B. burgdorferi, suggesting that genotypic differences in the infecting spirochetes play a key role in the pathogenesis and development of clinical disease.

Gamma interferon is not required for arthritis resistance in the murine Lyme disease model

Lyme arthritis is the most common complication following infection of human individuals with Borrelia burgdorferi sensu stricto. In mice, B. burgdorferi infection leads to arthritis of the tibiotarsal joints. Arthritis severity in mice is under host genetic control, as BALB/c mice developed mild arthritis but C3H/He mice developed severe disease following B. burgdorferi infection. To study the role of gamma interferon (IFN-gamma) in arthritogenesis, targeted mutant mice lacking the IFN-gamma receptor (IFN-gammaR) were infected by inoculation with B. burgdorferi. IFN-gammaR(-/-) and parental 129/SvEv mice developed mild arthritis of similar severity, as determined both by weekly tibiotarsal joint measurements and histopathology at 2 and 5 weeks postinfection. Both strains of mice had the same spirochetal burden in the joints, suggesting that the IFN-gammaR(-/-) mice were not impaired in controlling spirochetal expansion in vivo. The wild-type mice mounted a Th1 response, with a predominance of CD4(+) IFN-gamma(+) T cells observed by flow cytometry. In contrast, the IFN-gammaR(-/-) mice mounted a Th2 response, with a predominance of CD4(+) IL-4(+) T cells. As expected given their cytokine profile, the IFN-gammaR(-/-) mice produced fewer CD8(+) IFN-gamma(+) and MAC-1(+) IL-12(+) cells and less immunoglobulin G2a (IgG2a) than their wild-type counterparts. These results strongly suggest that IFN-gamma is not required for arthritis resistance or as part of an effective immune response against B. burgdorferi.

Host-pathogen interactions promoting inflammatory Lyme arthritis: use of mouse models for dissection of disease processes

Recent studies have confirmed the infectious and inflammatory nature of arthritis induced by Borrelia burgdorferi, or Lyme arthritis. This arthritis is directed by the presence of the bacteria in joint tissue, and is mediated through activation of the Toll-like receptor 2 (TLR2) signaling pathways by borrelial lipoproteins. Several host genes regulate the severity of arthritis, possibly by regulating the balance of pro- and anti-inflammatory responses.

Autoimmune mechanisms in antibiotic treatment-resistant lyme arthritis

In about 10% of patients with Lyme arthritis in the United States, joint inflammation persists for months or even several years after the apparent eradication of the spirochete, Borrelia burgdorferi, from the joint with antibiotic treatment. We propose a model of molecular mimicry affecting genetically susceptible individuals to explain this treatment-resistant course. The majority of patients with treatment-resistant Lyme arthritis have HLA-DRB1*0401 or related alleles, and the severity and duration of their arthritis correlate with cellular and humoral immune responses to outer-surface protein A OspA) of the spirochete. Using an algorithm, the immunodominant epitope of OspA presented by the DRB1*0401 molecule was predicted to be located at aa 165-173. In a search of the Genetics Computer Group gene bank, only one human protein was identified, lymphocyte function associated antigen-1 (hLFA-1), that had sequence homology with OspA(165-173)and predicted binding in the DRB1*0401 molecule. Synovial fluid T cells from most patients with treatment-resistant arthritis responded to both OspA and hLFA-1, whereas those from patients with other forms of chronic inflammatory arthritis did not. Molecular mimicry between a dominant T cell epitope of OspA and hLFA-1 may be an important factor in the persistence of joint inflammation in genetically susceptible patients with treatment-resistant Lyme arthritis.

Epidemiology of autoimmune reactions induced by vaccination

In order for vaccinations to 'work', the immune system must be stimulated. The concern that immunizations may lead to the development of autoimmune disease (AID) has been questioned. Since AID occur in the absence of immunizations, it is unlikely that immunizations are a major cause of AID. Epidemiological studies are needed, however, to assess whether immunizations may increase the risk in some susceptible individuals. This paper discusses the evidence for and against vaccination as a risk factor for AID. Evidence for immunizations leading to AID come from several sources including animal studies, single and multiple case reports, and ecologic association. However more rigorous investigation has failed to confirm most of the allegations. Unfortunately the question remains difficult to address because for most AIDs, there is limited knowledge of the etiology, background incidence and other risk factors for their development. This information is necessary, in the absence of experimental evidence derived from controlled studies, for any sort of adequate causality assessment using the limited data that are available. Several illustrative examples are discussed to highlight what is known and what remains to be explored, and the type of epidemiological evidence that would be required to better address the issues. Examples include the possible association of immunization and multiple sclerosis (and other demyelinating diseases), type 1 diabetes mellitus, Guillain-Barre Syndrome, idiopathic thrombocytopenic purpura, and rheumatoid arthritis.

Multiple pathways to induction of virus-induced autoimmune demyelination: lessons from Theiler's virus infection

Infection of SJL mice with wild-type BeAn strain of Theiler's murine encephalomyelitis virus (TMEV) leads to CD4(+)T cell-mediated CNS demyelination characterized by the development of anti-myelin epitope autoimmune responses via epitope spreading during the chronic stage of disease. To exmine the feasibility of virus-encoded mimic epitopes to initiate CNS autoimmunity, we recently developed a molecular mimicry model of virus-induced demyelinating disease wherein a non-pathogenic variant strain of TMEV was engineered to encode a 30-mer peptide encompassing the immunodominant myelin proteolipid protein, PLP139-151, epitope. SJL mice infected intracerebrally with TMEV encoding either the native PLP139-151 determinant or various peptide mimics of the epitope develop an early onset demyelinating disease mediated by activated PLP139-151-specific Th1 cells. The autoimmune nature of this early-onset demyelinating disease is shown by the fact that induction of tolerance to the PLP139-151 peptide prevents clinical disease and associated PLP139-151-specific T cell responses without affecting T cell reactivity to virus epitopes. Most significantly, TMEV encoding a molecular mimic peptide derived from the Haemophilus influenzae bacteria, homologous at only six out of thirteen of the core amino acids, led to CNS disease. These studies provide conclusive evidence that virus-induced myelin-specific autoreactive T cells can be induced by molecular mimicry and provide a useful model to study the disease inducing ability of viruses encoding human-disease-related mimicry peptides.