Induction of interleukin-1 release by high- and low-passage isolates of Borrelia burgdorferi

The antibiotics doxycycline and minocycline inhibit the inflammatory responses to the Lyme disease spirochete Borrelia burgdorferi

Tetracyclines moderate inflammatory responses of various etiologies. We hypothesized that tetracyclines, in addition to their antimicrobial function, could exert control over the inflammation elicited by Borrelia burgdorferi. To model systemic effects, we used the human monocytic cell line THP-1; to model effects in the central nervous system, we used rhesus monkey brain astrocytes and microglia. Cells were stimulated with live or sonicated B. burgdorferi or with the lipoprotein outer surface protein A in the presence of increasing concentrations of doxycycline or minocycline. Both antibiotics significantly reduced the production of tumor necrosis factor-alpha, interleukin (IL)-6, and IL-8 in a dose-dependent manner in all cell types. Microarray analyses of the effect of doxycycline on gene transcription in spirochete-stimulated monocytes revealed that the NFKB and CHUK (alias, IKKA) genes were down-regulated. Functionally, phosphorylation of IkappaBalpha and binding of NF-kappaB to target DNA were both reduced in these cells. Our results suggest that tetracyclines may have a dual therapeutic effect in Lyme disease.

Role of IL-17, transforming growth factor-beta, and IL-6 in the development of arthritis and production of anti-outer surface protein A borreliacidal antibodies in Borrelia-vaccinated and -challenged mice

We showed recently that the adaptive immune events leading to the development of arthritis in Borrelia burgdorferi isolate 297-vaccinated and Borrelia bissettii-challenged mice involve IL-17. Here, we show in Borrelia-vaccinated and -challenged mice that two cytokines known to induce the production of IL-17, IL-6 and transforming growth factor (TGF)-beta, are also involved in the development of arthritis. Vaccinated and challenged mice administered either anti-TGF-beta or anti-IL-6 antibodies developed histopathologic changes of the hind paws similar to or greater than untreated control mice. By contrast, simultaneous blockage of these cytokines reduced the severity of arthritis in Borrelia-vaccinated and -challenged mice. Moreover, administration of anti-IL-17 antibodies to these dual-antibody-treated mice completely prevented the development of histopathologic changes of the ankle joints, significantly reduced edema of the hind paws, and prevented the production of anti-outer surface protein A borreliacidal antibodies. These findings demonstrate a role for the combined effects of IL-17, IL-6, and TGF-beta in the adaptive immune events leading to the development of Borrelia-induced arthritis.

Borrelia burgdorferi and the macrophage: routine annihilation but occasional haven?

Borrelia burgdorferi, the agent for Lyme disease, has a typical pattern of bacterial interaction with phagocytes: attachment, stimulation o f release o f inflammatory mediators and, in most cases, ingestion and killing. Spirochetes are killed extracellulorly by antibody plus complement via the classical pathway, as well as by phagocytes through apparently nonoxidative means. Yet rare persistent spirochetes (mutants?) have been identified both in patients' tissues and in cells grown in vitro. Ruth Montgomery and Stephen Malawista here ask: are some Borrelia wolves in sheeps' clothing, evading macrophage anti-microbial action?

A role for peripheral blood fibrocytes in Lyme disease?

It is proposed that peripheral blood fibrocytes will be a new and important player in the pathogenesis of Lyme disease. Peripheral blood fibrocytes are a circulating leukocyte subpopulation that: (a) express collagen; (b) are an abundant source of cytokines, chemoattractants and growth factors; and (c) are able to recruit and activate naive T-cells and memory T-cells. We predict that peripheral blood fibrocytes will represent a new and important antigen-presenting cell which will play an important role in directing the immune response from the pathogenic Th1 to the protective Th2 response cell in Borrelia infections.

Borrelia burgdorferi-induced inflammation facilitates spirochete adaptation and variable major protein-like sequence locus recombination

Spirochete adaptation in vivo is associated with preferential Borrelia burgdorferi gene expression. In this paper, we show that the administration of B. burgdorferi-immune sera to IFN-gammaR-deficient mice that have been infected with B. burgdorferi N40 for 4 days causes spirochete clearance. In contrast, immune sera-mediated clearance of B. burgdorferi N40 is not apparent in immunocompetent mice, suggesting a role for IFN-gamma-mediated responses in B. burgdorferi N40 host adaptation. B. burgdorferi-immune sera also induces clearance of B. burgdorferi N40 that have been passaged in vitro 75 times (B. burgdorferi N40-75), a derivative of B. burgdorferi N40 that does not rapidly adapt in vivo in immunocompetent mice. B. burgdorferi N40-75 produce lower levels of IFN-gamma and IL-12 in mice than does B. burgdorferi N40, and the administration of these cytokines to B. burgdorferi N40-75-infected mice results in an increased spirochetal burden, further indicating that IFN-gamma-mediated events promote B. burgdorferi survival. Differential immunoscreening and RT-PCR demonstrate that IFN-gamma-mediated signals facilitate spirochete recombination at the variable major protein like sequence locus, a site for early antigenic variation in vivo, and that recombination rates by B. burgdorferi N40 are lower in IFN-gammaR-deficient mice than in control animals. These results suggest that the murine immune response can promote the in vivo adaptation of B. burgdorferi.

Interleukin-10 modulates proinflammatory cytokines in the human monocytic cell line THP-1 stimulated with Borrelia burgdorferi lipoproteins

We determined previously that lipoproteins of Borrelia burgdorferi stimulate inflammatory and anti-inflammatory cytokines (interleukin-10 [IL-10]) in monocytes. IL-10 could have an effect on innate and acquired immune responses to B. burgdorferi and influence the magnitude of the infectious inoculum and disease outcome. To understand the mechanism(s) of IL-10 action during early infection, when innate immunity expressed chiefly by skin macrophages is key, we investigated the effect of exogenous and endogenous IL-10 on the production of the macrophage-derived cytokines IL-6, IL-1beta, IL-12, and tumor necrosis factor alpha (TNF-alpha). We used the THP-1 human monocytic cell line and recombinant lipidated OspA (L-OspA) as the model target cell and stimulant, respectively. To determine the kinetics of cytokine production by THP-1 cells, we stimulated them with L-OspA and also with heat-killed B. burgdorferi cells (HBb) and lipopolysaccharide (LPS). Exogenous IL-10 dampened production of inflammatory cytokines, as elicited by lipoproteins. The inhibition of endogenous IL-10 function by anti-IL-10 antibody reduced the production of IL-12 and IL-6 but not that of IL-1beta and TNF-alpha. An inspection of the kinetics of cytokine production clarified this finding. TNF-alpha was produced prior to, and IL-beta was produced at the same time as, IL-10, whereas IL-6 and IL-12 were produced later. HBb, LPS, and L-OspA yielded similar kinetics of cytokine production. This result reinforces the notion that lipoproteins are the functional molecules in HBb and perhaps in vivo. It indicates also that signaling pathways utilized by LPS and lipoproteins may be extensively shared. The results are consistent with a major role played by IL-10 in controlling the initial phase of infection with this spirochete.

Borrelia burgdorferi gene expression in vivo and spirochete pathogenicity

Borrelia burgdorferi spirochetes that do not cause arthritis or carditis were developed and used to investigate Lyme disease pathogenesis. A clonal isolate of B. burgdorferi N40 (cN40), which induces disease in C3H/HeN (C3H) mice, was repeatedly passaged in vitro to generate nonpathogenic spirochetes. The passage 75 isolate (N40-75) was infectious for C3H mice but did not cause arthritis or carditis, and spirochetes were at low levels or absent in the joints or hearts, respectively. N40-75 could, however, cause disease in severe combined immunodeficient (SCID) mice, suggesting that the response in immunocompetent mice prevented effective spirochete dissemination and the subsequent development of arthritis and carditis. Administration of immune sera at 4 days after spirochete challenge aborted N40-75, but not cN40, infection in SCID mice. A B. burgdorferi genomic expression library was differentially probed with sera from cN40- and N40-75-infected mice, to identify genes that may not be effectively expressed by N40-75 in vivo. N40-75 was defective in the up-regulation of several genes that are preferentially expressed during mammalian infection, including dbpAB, bba64, and genes that map to the cp32 family of plasmids. These data suggest that adaptation and gene expression may be required for B. burgdorferi to effectively colonize the host, evade humoral responses, and cause disease.

Induction of pro- and anti-inflammatory cytokines by Borrelia burgdorferi lipoproteins in monocytes is mediated by CD14

We previously showed that heat-killed Borrelia burgdorferi spirochetes and lipidated outer surface protein A (L-OspA) stimulated the in vitro production of interleukin-10 (IL-10) in peripheral blood mononuclear cells (PBMC) from uninfected humans and rhesus monkeys (G. Giambartolomei et al., Infect. Immun. 66:2691-2697, 1998). Here we demonstrate that uninfected human peripheral blood monocytes, but not B or T cells, are the cells that transcribe the IL-10 cytokine gene in response to heat-killed B. burgdorferi. B. burgdorferi similarly induced an upregulation of the IL-1beta and IL-6 cytokine genes in monocytes and the production of IL-10 and IL-6 in culture supernatants of the human monocytic cell line THP-1. Purified L-OspA (but not unlipidated OspA [U-OspA] or U-OspC) also stimulated the production of both cytokines in THP-1 cells in a dose-dependent fashion, suggesting that acylation of the OspA protein molecule is required for the production of both anti- and pro-inflammatory cytokines in naive monocytes. A lipohexapeptide that contained the tripalmitoyl-modified cysteine motif (Pam3Cys-Hex) of B. burgdorferi lipoproteins but with an arbitrary peptide sequence had the same effect. Monoclonal antibodies (MAbs) MY4 and 60bca, both of which bind to CD14 and are known to block lipopolysaccharide (LPS)-mediated cytokine production, were able to block L-OspA-mediated IL-10 and IL-6 cytokine production. In contrast, MAb 26ic, which also binds to CD14 but does not block LPS function, failed to inhibit L-OspA-mediated cytokine production. These data suggest that activation of monocytes and production of both anti- and pro-inflammatory cytokines induced by lipoproteins proceeds via the CD14 receptor. LPS binding protein was not required for OspA-induced cytokine production. Our results demonstrate that pro- and anti-inflammatory cytokines induced by B. burgdorferi lipoproteins in PBMC are produced by monocytes and that lipoprotein and LPS signaling pathways share at least the initial signaling event that involves the CD14 receptor.

Borrelia burgdorferi stimulates the production of interleukin-10 in peripheral blood mononuclear cells from uninfected humans and rhesus monkeys

Heat-killed Borrelia burgdorferi spirochetes stimulate in vitro production of interleukin-10 (IL-10) at both mRNA and protein levels in peripheral blood mononuclear cells (PBMC) of uninfected rhesus monkeys. A concomitant down-modulation of IL-2 gene transcription was observed. Neither IL-4 nor gamma interferon gene expression was ostensibly affected by B. burgdorferi spirochetes. These phenomena were observed regardless of whether the stimulating spirochetes belonged to the B. burgdorferi sensu stricto, Borrelia afzelii, or Borrelia garinii genospecies, the three main species that cause Lyme disease. B. burgdorferi also induced production of IL-10 in uninfected human PBMC, indicating that this effect might play a role in human Lyme disease. Purified lipidated outer surface protein A (OspA), but not its unlipidated form, induced the production of high levels of IL-10 in uninfected human PBMC. Thus, the lipid moiety is essential in the induction of IL-10 in these PBMC. B. burgdorferi M297, a mutant strain that lacks the plasmid that encodes OspA and OspB, also induced IL-10 gene transcription in PBMC, indicating that this phenomenon is not causally linked exclusively to OspA and its lipid moiety. These results demonstrate that B. burgdorferi can stimulate the production of an antiinflammatory, immunosuppressive cytokine in naive cells and suggest that IL-10 may play a role both in avoidance by the spirochete of deleterious immune responses and in limiting the inflammation that the spirochete is able to induce.

Clearance of Borrelia burgdorferi may not be required for resistance to experimental lyme arthritis

Infection of inbred mouse strains with Borrelia burgdorferi results in the development of experimental Lyme arthritis. The degree of arthritic pathology has been suggested to correlate with the level of spirochete burden within tissues. To investigate this further, we infected resistant DBA/2 (DBA) and susceptible C3H/HeJ (C3H) mice in the hind footpads and monitored arthritis development for 21 days. To quantitate levels of spirochetes within tissues, we created a competitive PCR molecule containing modified ospA and fla gene segments. C3H mice developed severe arthritis of the tibiotarsal joints, while DBA mice developed only mild inflammation throughout the experimental period. At day 21, when the gross size and histologic composition of ankles revealed significant differences in arthritis between the strains, there was little difference in levels of spirochete DNA as determined by competitive PCR. Cultures of ankle tissue at day 21 were also uniformly positive in both C3H and DBA animals and contained relatively similar levels of spirochetes. These results indicate that the presence of spirochetes in the ankles of experimental animals is not sufficient for arthritis development. Since arthritic and nonarthritic animals can harbor relatively equal spirochete burdens yet retain their distinct phenotypic outcomes, an aberrant or overly exuberant immune response may be an additional requirement for pathology in arthritis-prone mice.

Borrelia burgdorferi induces the production and release of proinflammatory cytokines in canine synovial explant cultures

Canine synovial membrane explants were exposed to high- or low-passage Borrelia burgdorferi for 3, 6, 12, and 24 h. Spirochetes received no treatment, were UV light irradiated for 16 h, or were sonicated prior to addition to synovial explant cultures. In explant tissues, mRNA levels for the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1alpha (IL-1alpha), IL-1beta, and IL-8 were surveyed semiquantitatively by reverse transcription-PCR. Culture supernatants were examined for numbers of total and motile (i.e., viable) spirochetes, TNF-like and IL-1-like activities, polymorphonuclear neutrophil (PMN) chemotaxis-inducing activities, and IL-8. During exposure to synovial explant tissues, the total number of spirochetes in the supernatants decreased gradually by approximately 30%, and the viability also declined. mRNAs for TNF-alpha, IL-1alpha, IL-1beta, and IL-8 were up-regulated in synovial explant tissues within 3 h after infection with untreated or UV light-irradiated B. burgdorferi, and mRNA levels corresponded to the results obtained with bioassays. During 24 h of coincubation, cultures challenged with untreated or UV light-irradiated spirochetes produced similar levels of TNF-like and IL-1-like activities. In contrast, explant tissues exposed to untreated B. burgdorferi generated significantly higher levels of chemotactic factors after 24 h of incubation than did explant tissues exposed to UV light-treated spirochetes. In identical samples, a specific signal for IL-8 was identified by Western blot analysis. High- and low-passage borreliae did not differ in their abilities to induce proinflammatory cytokines. No difference in cytokine induction between untreated and sonicated high-passage spirochetes was observed, suggesting that fractions of the organism can trigger the production and release of inflammatory mediators. The titration of spirochetes revealed a dose-independent cytokine response, where 10(3) to 10(7) B. burgdorferi organisms induced similar TNF-like activities but only 10(7) spirochetes induced measurable IL-1-like activities. The release of chemotactic factors was dose dependent and was initiated when tissues were infected with at least 10(5) organisms. We conclude that intact B. burgdorferi or fractions of the bacterium can induce the local up-regulation of TNF-alpha, IL-1alpha, and IL-1beta in the synovium but that the interaction of viable spirochetes with synovial cells leads to the release of IL-8, which probably is a prime initiator of PMN migration during acute Lyme arthritis.

Borrelia burgdorferi migrates into joint capsules and causes an up-regulation of interleukin-8 in synovial membranes of dogs experimentally infected with ticks

Twenty 6-week-old specific-pathogen-free beagles were infected with Borrelia burgdorferi by tick challenge, and five uninfected dogs served as controls. During the study, all dogs were monitored for infection, clinical signs, and antibody response against B. burgdorferi. During episodes of lameness or postmortem, synovial fluids from each dog were examined for volume, cell number, polymorphonuclear leukocyte (PMN) content, cell viability, and chemotactic activity. Twenty-five tissues collected postmortem from each dog were tested for interleukin-8 (IL-8) mRNA, tumor necrosis factor alpha (TNF-alpha) mRNA, presence of live spirochetes, and histopathological changes. Thirteen infected dogs (group A), which seroconverted rapidly (maximum titers within 50 to 90 days), developed acute and severe mono- or oligoarthritis almost exclusively in the limb closest to the tick bite (median incubation period, 66 days). Synovial fluids of the arthritic joints collected during episodes of lameness had significantly elevated volume, cell count, PMN proportion, cell viability, and chemotactic activity for PMNs. The remaining joints of the same animals contained synovial fluids with elevated chemotactic activity and cell viability. Twelve dogs tested positive for IL-8 mRNA in multiple tissues (synovia, pericardium, and peritoneum), and 10 dogs expressed TNF-alpha mRNA, but only in the tributary lymph nodes of the inflamed joints. Histological examinations revealed severe poly- or oligoarthritis and moderate to severe cortical hyperplasia in draining lymph nodes of the inflamed joints in all 13 dogs. Seven infected dogs with mild or no clinical signs (group B) seroconverted slowly (peak titers after 90 days), and only some joint fluids showed chemotactic activity, which on average was lower than that in inflamed and noninflamed joints from dogs in group A. Four dogs expressed IL-8 mRNA (in the synovia and pericardium), and three dogs had TNF-alpha mRNA in tributary lymph nodes. Histologically, nonsuppurative arthritis was found in multiple joints, and mild to moderate cortical hyperplasia was found in draining lymph nodes. Five uninfected dogs without lameness (group C) had normal synovial fluids and tissues. In all infected dogs, live spirochetes were demonstrated more frequently in tissues of the somatic quadrant closest to the tick bite than in tissues further from the site of infection, suggesting that dissemination of B. burgdorferi occurs more by migration than by blood-borne spread. From these studies employing a canine model of B. burgdorferi infection, we conclude that IL-8 is involved in the pathogenesis of acute Lyme arthritis.

Lyme disease: a review of aspects of its immunology and immunopathogenesis

Lyme disease, caused by Borrelia burgdorferi, causes a multisystem inflammatory ailment, although the precise means of tissue damage are not well understood. It is clear that the organism is present at the site of inflammation in many organs and that many of the features of the illness are relieved by antibiotic therapy. A complex interaction between spirochete and immune systems of a number of mammalian hosts, in human disease and animal models, has been described. It is clear that T cells and macrophages are intimately associated with the pathogenesis of arthritis and that immune mechanisms are involved in other aspects of disease. Inflammation directed at persistence of Borrelial antigens is a plausible explanation for persisting arthritis. Autoimmunity based on molecular mimicry may play a role in the pathogenesis of Lyme disease. Humoral immunity plays a protective role, prompting interest in vaccine development. Significant variation in certain of the outer surface proteins suggests that multiple proteins, peptides, or chimeric vaccines may be needed to provide a sufficiently broad humoral protective response.

Ultrastructural demonstration of spirochetal antigens in synovial fluid and synovial membrane in chronic Lyme disease: possible factors contributing to persistence of organisms

To perform the first systematic electronmicroscopic (EM) and immunoelectron microscopy (IEM) study of the pathological changes and the evidence of spirochete presence in synovial membranes and synovial fluid (SF) cells of patients with chronic Lyme arthritis. EM examination was performed on four synovial membrane and eight SF cell samples from eight patients with chronic Lyme disease. Spirochetal antigens in the samples were sought by IEM using monoclonal antibody to Borrelia burgdorferi outer surface protein A (OspA) as the immunoprobe. Prominent ultrastructural findings were surface fibrin-like material, thickened synovial lining cell layer and signs of vascular injury. Borrelia-like structures were identified in all four synovial membranes and in two of eight SF cell samples. The presence of spirochetal antigens was confirmed by IEM in all four samples studied (one synovial membrane and three SF cell samples). OspA labelling was in perivascular areas, deep synovial stroma among collagen bundles, and in vacuoles of fibroblasts in synovial membranes; and in cytophagosomes of mononuclear cells in SF cell samples. Electron microscopy adds further evidence for persistence of spirochetal antigens in the joint in chronic Lyme disease. Locations of spirochetes or spirochetal antigens both intracellulary and extracellulary in deep synovial connective tissue as reported here suggest sites at which spirochaetes may elude host immune response and antibiotic treatment.

Immunity to Lyme disease: protection, pathology and persistence

Persistence of the Lyme disease spirochete, Borrelia burgdorferi, in the presence of an active immune response has been well documented. Evidence from the past year indicates that modulation of surface antigens by the spirochete may be a major mechanism for evading the immune response.

Macrophages exposed to Borrelia burgdorferi induce Lyme arthritis in hamsters

The mechanism(s) by which Lyme arthritis is induced has not been elucidated. In this study, we showed that macrophages have a direct, effector role in the pathogenesis of Lyme arthritis. Severe destructive arthritis was induced in recipients of macrophages obtained from Borrelia burgdorferi-vaccinated and nonvaccinated hamsters exposed to Formalin-inactivated B. burgdorferi in vitro and then challenged with the Lyme spirochete. Swelling of the hind paws was detected within 8 h of infection, increased rapidly, and peaked at 21 h. This initial swelling decreased, and by day 4 only slight swelling was detected. Severe swelling of the hind paws was detected 8 days after infection and increased rapidly, with peak swelling occurring on day 11. Histopathologic examination affirmed that macrophages exposed to Formalin-inactivated spirochetes induced a severe destructive Lyme arthritis. The onset and severity of the severe destructive arthritis were dependent on the number of macrophages transferred. By contrast, macrophages not exposed to Formalin-inactivated B. burgdorferi failed to induce severe destructive arthritis in recipients after challenge with B. burgdorferi. Similarly, severe destructive arthritis was not detected in recipients of macrophages injected with spirochetal growth medium. Our results also showed that transferred macrophages could not protect hamsters from infection with B. burgdorferi, as spirochetes were readily recovered from their tissues when cultured. These findings demonstrate that macrophages exposed to B. burgdorferi are directly involved in the induction of Lyme arthritis.

Nitric oxide production during murine Lyme disease: lack of involvement in host resistance or pathology

The murine model of Lyme disease was used to determine the role of inflammatory induced nitric oxide (NO) during infection by the spirochete Borrelia burgdorferi. The outer surface lipoproteins of B. burgdorferi are potent stimulators of inflammatory cytokines and NO production by cultured macrophages in vitro. The addition of NO to cultures of B. burgdorferi prevents growth, suggesting a protective role of NO for the infected host. NO is also a crucial effector in some models of arthritis. Therefore, the involvement of NO in controlling B. burgdorferi infection and its participation in pathological development of arthritis were investigated. Both mildly arthritic (BALB/c) and severely arthritic (C3H/HeJ) strains of mice systemically produced high levels of NO 1 week after infection with B. burgdorferi, as determined by urinary nitrate. NO production remained high throughout the infection in BALB/c mice, while in C3H/HeJ mice NO production returned rapidly to uninfected levels. The in vivo inhibitor of the NO synthase enzyme NG-L-monomethyl arginine (LMMA) was given to mice to investigate whether decreasing NO production would alter the course of disease. LMMA effectively blocked NO production in infected mice; however, there was no significant difference in arthritis development, spirochete infection of tissues, or production of specific antibody in LMMA-treated mice. These results indicate that B. burgdorferi is able to persist in the host even in the presence of high levels of NO. Furthermore, NO is not involved in the control of spirochete infection of tissues, nor is it involved in the development of arthritis. The potent activity of NO against intracellular pathogens and the in vivo resistance of B. burgdorferi to NO suggest that this organism is not located in an intracellular compartment during an essential portion of its infection of the mammalian host.

Borrelia burgdorferi-specific T lymphocytes induce severe destructive Lyme arthritis

This is the first documentation that Borrelia burgdorferi-specific T lymphocytes are involved in the pathogenesis of Lyme arthritis. We present direct evidence that T lymphocytes obtained from inbred LSH hamsters vaccinated with a whole-cell preparation of Formalin-inactivated B. burgdorferi sensu stricto isolate C-1-11 in adjuvant conferred on naive recipient hamsters the ability to develop severe destructive arthritis when challenged with B. burgdorferi sensu stricto isolates C-1-11 and 297. By contrast, recipients infused with normal T lymphocytes and challenged with B. burgdorferi sensu stricto isolates C-1-11 and 297 failed to develop severe destructive arthritis. The T lymphocytes transferred were obtained from the lymph nodes of vaccinated and nonvaccinated hamsters by depleting B lymphocytes by using monoclonal antibody 14-4-4s (< 1% B lymphocytes by flow cytometric analysis). The enriched T lymphocytes showed enhanced proliferation to stimulation with concanavalin A and failed to respond to lipopolysaccharide. Moreover, only the enriched T lymphocytes from vaccinated hamsters proliferated on exposure to a whole-cell preparation of B. burgdorferi sensu stricto isolate C-1-11 in the presence of mitomycin-treated syngeneic antigen-presenting cells. These results demonstrate that B. burgdorferi-specific T lymphocytes primed by vaccination with a whole-cell preparation of inactivated B. burgdorferi sensu stricto isolate C-1-11 in adjuvant are involved in the development of severe destructive arthritis. Additional experiments are needed to define the precise mechanism(s) responsible for the development of Lyme arthritis.

Expression of endothelial cell adhesion molecules in joints and heart during Borrelia burgdorferi infection of mice

The expression of adhesion molecules on endothelia was examined during chronic arthritis and carditis in SCID and immunocompetent susceptible AKR/N mice infected with Borrelia burgdorferi (B. burgdorferi). All stages of disease were associated with the upregulation or new expression of ICAM-1 and P-selectin and of VCAM-1 and E-selectin, respectively, on blood vessels of affected joint tissues of SCID and AKR/N mice as well as on heart tissue of SCID mice but not in other tissues. Moreover, ICAM-1 was also found on infiltrating mononuclear cells. The overall staining intensity for each of the four adhesion molecules on individual tissue sections of joint and heart increased with time of infection and was associated with the presence of spirochetes in the tissue. In addition it is shown that in both mouse strains inflammation of joints but not heart is accompanied by vascular proliferation. Synovial but not heart tissues of infected SCID mice were found to express both peripheral- (PNAd) and mucosal (MAdCAM-1) lymph node high endothelia venule associated vascular addressins as detected by mAb Meca-79 and Meca-367, respectively, but only at later stages of the disease and only on newly generated small venules. However, neither of the two addressins were evident in synovial lesions of AKR/N mice. Together the data suggest that the concomittant induction of ICAM-1, VCAM-1, E-selectin and P-selectin in lesions of infected mice provide a means for enhanced cellular infiltration into affected organs and that the regulation of these structures is conserved in the absence of a functional immune system. Furthermore, the differential induction of vascular proliferation in joint and heart tissues as well as the restricted expression patterns of vascular addressins indicate that the pathogenetic processes induced by B. burgdorferi are distinct for joint and heart.

Retention of B. burgdorferi pathogenicity and infectivity after multiple passages in a co-culture system

In vitro cultivation of B. burgdorferi in BSK medium results in the loss of infectivity and pathogenicity after repeated passages. To prevent this loss, a feeder layer of tibio-tarsal joint tissue derived from newborn LEW/N rats was grown on Cytodex 3 microcarriers in ESG (formerly BSKE), a novel medium developed to support the growth of both the feeder layer and B. burgdorferi. A new pathogenic isolate (FNJ) and a high passage, non-pathogenic strain (TNJ) grew well in this co-culture system with high yields of viable organism. FNJ caused no growth inhibition or visible damage to the cells in the feeder layer. FNJ remained arthritogenic for newborn LEW/N rats after 22 passages in the co-culture system, but lost its arthritogenicity after 7 passages when cultured in BSK medium. This borrelia-mammalian tissue co-culture technique presents an experimental system to study the long term interactions of B. burgdorferi with the infected host tissues in vitro, as well as facilitate diagnostic tests and vaccine development.