LYME DISEASE

Environmental toxins and Alzheimer's disease progression

Alzheimer's disease (AD) is the most common form of dementia, which causes progressive memory loss and cognitive decline. Effective strategies to treat or prevent remains one of the most challenging undertakings in the medical field. AD is a complex and multifactorial disease that involves several risk factors. Aging and genetic factors both play important roles in the onset of the AD, however; certain environmental factors have been reported to increase the risk of AD. Chronic exposure to toxins has been seen as an environmental factor that may increase the risk of developing a neurodegenerative disease such as AD. Exposure to metals and biotoxins produced by bacteria, molds, and viruses may contribute to the cognitive decline and pathophysiology associated with AD. Toxins may contribute to the pathology of the disease through various mechanisms such as deposition of amyloid-beta (Aβ) plaques and tangles in the brain, induction of apoptosis, inflammation, or oxidative damage. Here, we will review how toxins affect brain physiology with a focus on mechanisms by which toxins may contribute to the development and progression of AD. A better understanding of these mechanisms may help contribute towards the development of an effective strategy to slow the progression of AD.

Anaplasma phagocytophilum-infected neutrophils enhance transmigration of Borrelia burgdorferi across the human blood brain barrier in vitro

The manifestations of Lyme disease, caused by Ixodes spp. tick-transmitted Borrelia burgdorferi, range from skin infection to bloodstream invasion into the heart, joints and nervous system. The febrile infection human granulocytic anaplasmosis is caused by a neutrophilic rickettsia called Anaplasma phagocytophilum, also transmitted by Ixodes ticks. Previous studies suggest that co-infection with A. phagocytophilum contributes to increased spirochetal loads and severity of Lyme disease. However, a common link between these tick-transmitted pathogens is dissemination into blood or tissues through blood vessels. Preliminary studies show that B. burgdorferi binds and passes through endothelial barriers in part mediated by host matrix metalloproteases. Since neutrophils infected by A. phagocytophilum are activated to release bioactive metalloproteases and chemokines, we examined the enhanced B. burgdorferi transmigration through vascular barriers with co-infection in vitro. To test whether endothelial transmigration is enhanced with co-infection, B. burgdorferi and A. phagocytophilum-infected neutrophils were co-incubated with EA.hy926 cells (HUVEC-derived) and human brain microvascular endothelial cells in Transwell cultures. Transmigration of B. burgdorferi through endothelial cell barriers was determined and endothelial barrier integrity was measured by transendothelial electrical resistivity. More B. burgdorferi crossed both human BMEC and EA.hy926 cells in the presence of A. phagocytophilum-infected neutrophils than with uninfected neutrophils without affecting endothelial cell integrity. Such a mechanism may contribute to increased blood and tissue spirochete loads.

Borrelia burgdorferi, host-derived proteases, and the blood-brain barrier

Neurological manifestations of Lyme disease in humans are attributed in part to penetration of the blood-brain barrier (BBB) and invasion of the central nervous system (CNS) by Borrelia burgdorferi. However, how the spirochetes cross the BBB remains an unresolved issue. We examined the traversal of B. burgdorferi across the human BBB and systemic endothelial cell barriers using in vitro model systems constructed of human brain microvascular endothelial cells (BMEC) and EA.hy 926, a human umbilical vein endothelial cell (HUVEC) line grown on Costar Transwell inserts. These studies showed that B. burgdorferi differentially crosses human BMEC and HUVEC and that the human BMEC form a barrier to traversal. During the transmigration by the spirochetes, it was found that the integrity of the endothelial cell monolayers was maintained, as assessed by transendothelial electrical resistance measurements at the end of the experimental period, and that B. burgdorferi appeared to bind human BMEC by their tips near or at cell borders, suggesting a paracellular route of transmigration. Importantly, traversal of B. burgdorferi across human BMEC induces the expression of plasminogen activators, plasminogen activator receptors, and matrix metalloproteinases. Thus, the fibrinolytic system linked by an activation cascade may lead to focal and transient degradation of tight junction proteins that allows B. burgdorferi to invade the CNS.

Lyme borreliosis

Despite more than 25 years' experience with Lyme borreliosis, much remains to be learned about this complex zoonosis. Practicing veterinarians, particularly those in the northeastern and upper midwestern states, where Lyme borreliosis is highly endemic, should be familiar with the ecologic features and typical clinical signs of Lyme borreliosis. Interpretation of signs and serologic test results should be made with consideration of the regional prevalence of Lyme borreliosis and the animal's opportunity for exposure to infected Ixodes spp. The availability of recently marketed topical acaracides is a valuable adjunctive measure in prevention of Lyme borreliosis. A maximally effective prevention strategy should include consideration of environmental modification, activity restrictions, routine examinations for ticks, prompt removal of attached ticks, and vaccination. Technologic advances, such as the C6 EIA and the Osp A recombinant vaccine, offer the promise of additional tools for the clinical management and prevention of this tick-borne zoonosis.

Cutting edge: T cell-mediated pathology in murine Lyme borreliosis

Even in the absence of an appropriate model or direct evidence, T cells have been hypothesized to exacerbate the manifestations of Lyme disease. To define definitely the role of T cells in Lyme disease, the course of disease in immunocompetent and B cell-deficient mice was compared. By 8 wk postinoculation, immunocompetent mice resolved both carditis and arthritis, whereas foci of myocarditis and severe destructive arthritis characterized disease of B cell-deficient mice. Cell transfer experiments using infected B6-Rag1 knock out mice demonstrated that: 1) innate immunity mediated the initial sequelae of infection, 2) transferring both naive T cells and B cells induced resolution of carditis and arthritis, 3) infected mice reconstituted with T cells developed myocarditis and severe destructive arthritis, and 4) CD4+ T cells were responsible for the observed immune-mediated pathology. These data demonstrate directly the deleterious effect of T cells in Lyme disease.

Structural requirements for glycosaminoglycan recognition by the Lyme disease spirochete, Borrelia burgdorferi

Borrelia burgdorferi, the Lyme disease agent, binds glycosaminoglycans (GAGs) such as heparin, heparan sulfate, and dermatan sulfate. Heparin or heparan sulfate fractions separated by size or charge were tested for their ability to inhibit attachment of B. burgdorferi to Vero cells. GAG chains of increasing length and/or charge showed increasing inhibitory potency, and detectable heparin inhibition of bacterial binding required a minimum of 16 residues. The ability of a given heparin fraction to inhibit binding to Vero cells was strongly predictive of its ability to inhibit hemagglutination, suggesting that hemagglutination reflects the capacity of B. burgdorferi to bind to GAGs.

A distinctive cutaneous reaction pattern indicative of infection by reactive arthropathy-associated microbial pathogens: the superantigen ID reaction

The two major cutaneous expressions of infective states are infections of the skin by viable organisms and immunological responses to nonviable microbial antigens or, in the case of molecular mimickry, their human analogues. These immunological responses are designated as cutaneous id reactions, and manifest a histomorphology similar to that seen at the primary infective site. This study presents the clinical and histological findings in 16 patients who developed skin eruptions associated with extracutaneous or systemic infections. There was a striking female predominance; patients ranged in age from 10 to 78 years. The majority of cases manifested skin lesions which clinically resembled Sweet's syndrome, erythema multiforme and/or erythema nodosum. Fever, arthralgia, oligoarthritis, mucosal ulcers of the mouth and/ or genital tract and uveitis were additional features in some cases. Isolated clinical presentations included a petechial rash in a stocking and glove distribution, papular dermatitis, a morbilliform eruption and annular erythema. Among the medical and family histories were atopy and stigmata associated with connective tissue disease (CTD). Two patients were ingesting drugs with known immune dysregulating properties. Skin biopsies showed focal lymphocytic interface dermatitis, a diffuse interstitial histiocytic infiltrate, and a mononuclear cell predominant vascular reaction which in some cases represented vasculitis by virtue of manifesting concomitant luminal or mural fibrin deposition. Eosinophils, eczematous alterations, and papillary dermal edema were identified in a minority of cases. All patients had evidence of a prior or concurrent infection, based on either positive IgM serology for specific microbes or cultures. Among the implicated pathogens were cytomegalovirus, parvovirus B19, streptococcus, mycoplasma, klebsiella, and Borrelia burgdorferi. All of these organisms are among those associated with reactive arthritis, a phenomenon that was seen in some cases. The histology suggested florid cell mediated immunity (CMI), which the authors attributed to the superantigen properties held by the aforesaid pathogens. Skin lesions and constitutional symptoms resolved quickly with antimicrobial therapy in 7 of 9 cases causally linked to bacteria. Spontaneous resolution occurred in 5 of 6 virally mediated eruptions. The other 4 patients were given topical steroids or prednisone; these included 1 patient with Borrelia burgdorferi infection and 1 patient with radiographic evidence of pneumonia who was never cultured, 1 patient with parvovirus B19 infection, and 1 patient with pneumococcal pneumonia and concomitant sarcoidosis. It is the authors' belief that the eruptions seen in these patients may in part reflect a genetic or iatrogenic predisposition to respond excessively to certain infectious triggers.

Integrins alpha(v)beta3 and alpha5beta1 mediate attachment of lyme disease spirochetes to human cells

Borrelia burgdorferi (sensu lato), the agent of Lyme disease, is able to cause chronic, multisystemic infections in human and animal hosts. Attachment of the spirochete to host cells is likely to be important for the colonization of diverse tissues. The platelet-specific integrin alpha(IIb)beta3 was previously identified as a receptor for all three species of Lyme disease spirochetes (B. burgdorferi sensu stricto, B. garinii, and B. afzelii). Here we show that B. burgdorferi also recognizes the widely expressed integrins alpha(v)beta3 and alpha5beta1, known as the vitronectin and fibronectin receptors, respectively. Three representatives of each species of Lyme disease spirochete were tested for the ability to bind to purified alpha(v)beta3 and alpha5beta1. All of the strains tested bound to at least one integrin. Binding to one integrin was not always predictive of binding to other integrins, and several different integrin preference profiles were identified. Attachment of the infectious B. burgdorferi strain N40 to purified alpha(v)beta3 and alpha5beta1 was inhibited by RGD peptides and the appropriate receptor-specific antibodies. Binding to alpha(v)beta3 was also shown by using a transfected cell line that expresses this receptor but not alpha(IIb)beta3. Attachment of B. burgdorferi N40 to human erythroleukemia cells and to human saphenous vein endothelial cells was mediated by both alpha5beta1 and alpha(v)beta3. Our results show that multiple integrins mediate attachment of Lyme disease spirochetes to host cells.

Different classes of proteoglycans contribute to the attachment of Borrelia burgdorferi to cultured endothelial and brain cells

The Lyme disease spirochete, Borrelia burgdorferi, infects multiple tissues, such as the heart, joint, skin, and nervous system and has been shown to recognize heparan sulfate and dermatan sulfate proteoglycans. In this study, we examined the contribution of different classes of proteoglycans to the attachment of the infectious B. burgdorferi strain N40 to several immortalized cell lines and primary cultured cells, including endothelial cells and brain cells. Bacterial attachment was inhibited by exogenous proteoglycans or by treatment of host cells with inhibitors of proteoglycan synthesis or sulfation, indicating that proteoglycans play a critical role in bacterial binding to diverse cell types. Binding to primary bovine capillary endothelial cells or a human endothelial cell line was also inhibited by digestion with heparinase or heparitinase but not with chondroitinase ABC. In contrast, binding to glial cell-enriched brain cell cultures or to a neuronal cell line was inhibited by all three lyases. Binding of strain N40 to immobilized heparin could be completely inhibited by dermatan sulfate, and conversely, binding to dermatan sulfate could be completely blocked by heparin. As measured by 50% inhibitory dose, heparin was a better inhibitor of binding than dermatan sulfate, regardless of whether the substrate was heparin or dermatan sulfate. These results are consistent with the hypotheses that the species of proteoglycans recognized by B. burgdorferi vary with cell type and that bacterial recognition of different proteoglycans is mediated by the same bacterial molecule(s).

Predisposing factors for individuals' Lyme disease prevention practices: Connecticut, Maine, and Montana

OBJECTIVES

This study examined factors that predispose individuals to protect against Lyme disease.

METHODS

Knowledge, attitude, and practice questions concerning Lyme disease prevention were included in the Behavioral Risk Factor Surveillance surveys in Connecticut, Maine, and Montana. A total of 4246 persons were interviewed.

RESULTS

Perceived risk of acquiring Lyme disease, knowing anyone with Lyme disease, knowledge about Lyme disease, and believing Lyme disease to be a common problem were significantly associated with prevention practices.

CONCLUSIONS

Predisposing factors differ substantially between states and appear related to disease incidence. Personal risk, knowing someone with Lyme disease, and cognizance about Lyme disease and acting on this information are consistent with social learning theories.

Borrelia burgdorferi induces chemokines in human monocytes

Lyme disease is clinically and histologically characterized by strong inflammatory reactions that contrast the paucity of spirochetes at lesional sites, indicating that borreliae induce mechanisms that amplify the inflammatory response. To reveal the underlying mechanisms of chemoattraction and activation of responding leukocytes, we investigated the induction of chemokines in human monocytes exposed to Borrelia burgdorferi by a dose-response and kinetic analysis. Lipopolysaccharide (LPS) derived from Escherichia coli was used as a positive control stimulus. The release of the CXC chemokines interleukin-8 (IL-8) and GRO-alpha and the CC chemokines MIP-1alpha, MCP-1, and RANTES was determined by specific enzyme-linked immunosorbent assays, and the corresponding gene expression patterns were determined by Northern blot analysis. The results showed a rapid and strong borrelia-inducible gene expression which was followed by the release of chemokines with peak levels after 12 to 16 h. Spirochetes and LPS were comparably effective in stimulating IL-8, GRO-alpha, MCP-1, and RANTES expression, whereas MIP-1alpha production preceded and exceeded chemokine levels induced by LPS. Unlike other bacteria, the spirochetes themselves did not bear or release factors with intrinsic chemotactic activity for monocytes or neutrophils. Thus, B. burgdorferi appears to be a strong inducer of chemokines which may, by the attraction and activation of phagocytic leukocytes, significantly contribute to inflammation and tissue damage observed in Lyme disease.

An optimized PCR leads to rapid and highly sensitive detection of Borrelia burgdorferi in patients with Lyme borreliosis

The present study aimed at developing an optimized PCR protocol fro the sensitive and specific detection of all three Borrelia burgdorferi genospecies pathogenic to humans in Lyme borreliosis patients. A rapid DNA extraction method using alkaline lysis was introduced and was found to be superior to other DNA extraction methods. Nested PCR was performed with primer sets targeting the plasmid-located ospA gene and a chromosomal gene segment encoding a 66-kDa protein (p66). In spiked synovial fluid (SF) fewer than three borreliae/sample were detected. The specificities of the amplicons were confirmed by Southern blot analysis with PCR-derived probes. Urine, cerebrospinal fluid (CSF), and SF specimens from 57 patients with Lyme borreliosis and from 58 controls were examined. In clinical samples the diagnostic sensitivity of PCR was 85% with SF samples, 79% with urine samples, and 91% with paired SF-urine samples from patients with Lyme arthritis and was 79% with CSF samples, 45% with urine samples, and 87% with paired CSF-urine specimens from neuroborreliosis patients. One patient each with neuroborreliosis and with Lyme arthritis had PCR-positive urine samples only. In 17% of all cases both primer sets yielded positive results, while the other patients were positive with only one primer set. Among these, more positive results were obtained with the p66 gene primer than with the ospA primer. The specificity exceeded 99%. We conclude that DNA from B. burgdorferi sensu lato species can sensitively and specifically be detected with the optimized PCR method described. At least two different primer sets should be used, and whenever possible, urine and CSF or SF should be analyzed in parallel to achieve maximum sensitivity of the test. This protocol, therefore, considerably enhances the diagnostic power of PCR in patients with B. burgdorferi infection.

A "minority" opinion about the diagnosis and treatment of Lyme arthritis

Historically, arthritis was the main symptom which led to the description of the disease called Lyme borreliosis. However, a relatively high awareness of doctors and patients of tick-borne diseases seems to cause a trend to frequently diagnose this antibiotic-sensitive disease. A case can be defined as borreliosis only if either the typical erythema migrans is reliably identified by a physician or if a characteristic late manifestation of Lyme disease is accompanied by unequivocal serological and/or bacteriological evidence of Borrelia infection. Within the musculoskeletal system, the only reliably characteristic symptom is true synovitis, as defined by the palpable swelling of a joint. Mere joint pain or the subjective pain syndrome of fibromyalgia do not constitute a defining symptom for borreliosis. An evaluation of the frequency of Borrelia-associated arthritis in our Viennese rheumatology outpatient clinic revealed only six well-defined cases among 1,673 subsequent referrals. Based on "serological" suspicion, the question had been asked about possible borreliosis in 87 of these patients. In order to avoid unnecessary anxiety about possible long-term complications of Lyme disease among (actually misdiagnosed) patients, the diagnosis of Lyme arthritis should only be made according to the stringent criteria mentioned above. The antibiotic treatment, which is given to many questionable cases of borreliosis ex iuvantibus, although possibly of benefit to a few cases of otherwise undiagnosed reactive arthritis due to infections with microbes other than Borrelia burgdorferi, has to be termed irrational.

Hemagglutination and proteoglycan binding by the Lyme disease spirochete, Borrelia burgdorferi

The ability of the Lyme disease spirochete to attach to host components may contribute to its ability to infect diverse tissues. We present evidence that the Lyme disease spirochete expresses a lectin activity that promotes agglutination of erythrocytes and bacterial attachment to glycosaminoglycans. Among a diverse collection of 21 strains of Lyme disease spirochete, hemagglutinating activity was easily detected in all but 3 strains, and these three strains were noninfectious. The ability to agglutinate erythrocytes was associated with the ability of the spirochete to bind to the sulfated polysaccharide dextran sulfate and to mammalian cells. Soluble dextran sulfate was a potent inhibitor of both hemagglutination and attachment to mammalian cells, while dextran had no effect on either activity, suggesting that dextran sulfate may inhibit attachment by mimicking host cell glycosaminoglycans. Consistent with this, the spirochete bound to immobilized heparin, and soluble heparin inhibited bacterial adhesion to mammalian cells. The bacterium did not bind efficiently to Vero cells treated with heparinase or heparitinase or to mutant CHO cell lines that are deficient in proteoglycan synthesis. Sulfation of glycosaminoglycans was critical for efficient bacterial recognition, as Vero cells treated with an inhibitor of sulfation, or a mutant CHO cell line that produces undersulfated heparan sulfate, did not mediate maximal spirochetal binding. Binding of the spirochete to extracellular matrix also appeared to be dependent upon this attachment pathway. These findings suggest that a glycosaminoglycan-binding activity which can be detected by hemagglutination contributes to the attachment of the Lyme disease spirochete to host cells and matrix.

Treatment of late Lyme borreliosis

The aim of this study was to develop a treatment for late Lyme borreliosis and to compare the clinical results with serological findings before and after treatment. It was done in the Aland Islands (population 25,000), a region endemic for Lyme borreliosis. The patients were the first consecutive 100 patients from the Aland Islands with late Lyme borreliosis. They were followed for at least 1 year after treatment. The clinical results of treatment were compared with results of analyses of flagellar IgG antibodies to Borrelia burgdorferi done at the time of diagnosis before treatment and up to 12 months afterwards. Short periods of treatment were not generally effective. The outcome was successful in four of 13 treatments with 14 days of intravenous ceftriaxone alone, in 50 of 56 assessable treatments with ceftriaxone followed by 100 days of amoxycillin plus probenecid, and in 19 of 23 completed treatments with ceftriaxone followed by 100 days of cephadroxil. Titres of IgG antibodies to B. burgdorferi flagella declined significantly after 6 and 12 months in the patients who had successful treatments. All patients whose final titres were less than 30% of the initial titre were in the successful group. Their titres usually remained above the upper limit of normal for a long time but a decline to a value of less than 30% of that before treatment was always a sign of cure.