RESEARCHFRAUD.COM

Abstract:
     Natural killer (NK) cells are a heterogenous subpopulation of peripheral blood lymphocytes (PBL) that have the ability to kill various tumors and tumor cell lines in the absence of prior sensitization. These cells have generated considerable interest and have been implicated in natural resistance to tumors,^1-5 resistance to viral infection:^5-7 transplantation rejection,^5,8 and immunoregulation of both T and B cells.^9-11 Recently, there has been evidence that NK cells or large granular lymphocytes (LGLs) are also involved in host resistance against bacterial infections. This has been demonstrated by the bactericidal activity of NK-like cells against certain bacteria such as Shigella and Salmonella.^12-14 In addition to these interactions, there are several reports that demonstrate bacterial activation and/or recruitment of NK and NK-like cells presumably through the production or action of interferon, interleukin-2, and/or lipopolysaccharide (LPS).^12,16-18 Under certain conditions this augmentation may be inhibited by LPS,¹⁷ which attests to the complex nature of the microorganism-host interactions. Furthermore, the NK cell killing of infected host cellsI5 or local inflammation secondary to the killing of extracellular microorganisms may be responsible for the tissue destruction seen in various bacterial infections.

     The humoral and cellular responses in Lyme borreliosis have recently been under active investigation. While the humoral antibody response to Borrelia burgdorferi is well characterized, the cellular immune response is not well defined. However, it is known that a strong specific T cell response to B. burgdorferi occurs early in the course of the disease. This response may even precede the development of a measurable antibody response in some cases.¹⁹ Once established, this response is long lasting.

     In this report, the cellular immune response to B. burgdorferi is further investigated. Specifically, the modulation of NK cells and NK cell activity by B. burgdorferi both in vivo and in vitro is characterized and discussed.

Author: Chiao JW, Pavia C, Riley M, Altmann-Lasekan W, Abolhassani M, Liegner K, Mittelman A.
Journal: FEMS Immunol Med Microbiol; 1994 Feb; 8(2):151-5.
PubMed ID:8173554.

Abstract:
Modulation of cellular immune responses by the spirochaete Borrelia burgdorferi, the bacteria that causes Lyme disease, was demonstrated. When cultured in the presence of sonicated Borrelia preparation (Bb), the mitogen- or antigen-stimulated proliferative responses of normal lymphocytes were consistently lowered. Bb caused the greatest reduction in concanavalin A (ConA) or antigen-stimulated proliferation, where almost 100% reduction in proliferation could be achieved. Bb also reduced phytohemagglutinin-M (PHA) or pokeweed mitogen (PWM)-stimulated peripheral blood lymphocyte (PBL) proliferation, with the PWM proliferation being the least affected. This regulatory activity was not due to toxicity and was determined to be caused by Bb protein antigens. The degree of the proliferation reduction was directly proportional to both Bb quantity and length of exposure to lymphocytes. IL-2 production was significantly reduced from Bb-exposed lymphocytes. The entry of lymphocytes into the proliferating phases of the cell cycle was also shown to be blocked. These results have demonstrated an immune suppressive mechanism of B. burgdorferi. The magnitude of host immune responses may be dependent on the degree of suppression which is related to the spirochaete quantity and their length of presence in the host

Author: Aberer E, Koszik F, Silberer M.
Journal: Clin Infect Dis; 1997 Jul; 25 Suppl 1():S64-70
PubMed ID:9233667.

Abstract:
Chronic Lyme borreliosis (CLB) can present not only in different organs but also in different patterns. Although many theories exist about the mechanisms leading to CLB, it is known that viable Borrelia burgdorferi can persist for decades and cause late skin manifestations of acrodermatitis chronica atrophicans (ACA). Thus, the immunopathogenetic findings in ACA can serve as a model for studying the chronic course of Lyme borreliosis. Recent findings indicate that the most important cell for antigen presentation, the epidermal Langerhans cell (LC), is invaded by B. burgdorferi in early Lyme borreliosis. Therefore, LCs were stained immunohistochemically with different markers to investigate their functional activity. Numbers of CD1a+ LCs were reduced in erythema migrans but normal or slightly elevated in ACA. In both diseases there was also a marked downregulation of major histocompatibility complex class II molecules on LCs, as measured by staining of human leukocyte antigen DR. This phenomenon might be a mechanism that protects against the presentation of autoantigens and may be the cause of the impaired capacity of LCs to eliminate B. burgdorferi antigens, thus explaining why CLB is chronic.

Author: Chiao JW, Villalon P, Schwartz I, Wormser GP.
Journal: FEMS Immunol Med Microbiol; 2000 Jul; 28(3):193-6.
PubMed ID: 10865170.

Abstract:
     The modulation of human lymphocyte proliferative responses was demonstrated with a recombinant outer surface protein A (OspA) vaccine preparation for the prevention of Borrelia burgdorferi infection. After exposure to either the unaltered vaccine preparation or OspA prepared in saline, normal lymphocyte responses to the mitogens concanavalin A, phytohemagglutinin-M or pokeweed mitogen, or the antigen BCG were consistently reduced. Whole cell extracts of B. burgdorferi also modulated immune responses but required a much greater quantity of protein than needed for the OspA preparation. The magnitude of modulation was directly dependent on the quantity of OspA. OspA interferes with the response of lymphocytes to proliferative stimuli including a blocking of cell cycle phase progression. Future studies designed to delete the particular region or component of the OspA molecule responsible for this effect may lead to improved vaccine preparations.

Author: Diterich I, Rauter C, Kirschning CJ, Hartung T
Journal:  Infect Immun; 2003 Jul; 71(7):3979-87.
PubMed ID: 12819085.

Abstract:
     If left untreated, infection with Borrelia burgdorferi sensu lato may lead to chronic Lyme borreliosis. It is still unknown how this pathogen manages to persist in the host in the presence of competent immune cells. It was recently reported that Borrelia suppresses the host's immune response, thus perhaps preventing the elimination of the pathogen (I. Diterich, L. Härter, D. Hassler, A. Wendel, and T. Hartung, Infect. Immun. 69:687-694, 2001). Here, we further characterize Borrelia-induced immunomodulation in order to develop a model of this anergy. We observed that the different Borrelia preparations that we tested, i.e., live, heat-inactivated, and sonicated Borrelia, could desensitize human blood monocytes, as shown by attenuated cytokine release upon restimulation with any of the different preparations. Next, we investigated whether these Borrelia-specific stimuli render monocytes tolerant, i.e. hyporesponsive, towards another Toll-like receptor 2 (TLR2) agonist, such as lipoteichoic acid from gram-positive bacteria, or towards the TLR4 agonist lipopolysaccharide. Cross-tolerance towards all tested stimuli was induced. Furthermore, using primary bone marrow cells from TLR2-deficient mice and from mice with a nonfunctional TLR4 (strain C3H/HeJ), we demonstrated that the TLR2 was required for tolerance induction by Borrelia, and using neutralizing antibodies, we identified interleukin-10 as the key mediator involved. Although peripheral blood mononuclear cells tolerized by Borrelia exhibited reduced TLR2 and TLR4 mRNA levels, the expression of the respective proteins on monocytes was not decreased, ruling out the possibility that tolerance to Borrelia is attributed to a reduced TLR2 expression. In summary, we characterized tolerance induced by B. burgdorferi, describing a model of desensitization which might mirror the immunosuppression recently attributed to the persistence of Borrelia in immunocompetent hosts.

Author: Hulínská D1, Roubalová K, Schramlová J.
Journal: Folia Biol (Praha); 2003; 49(1):40-8.
PubMed ID: 12630667

Abstract:
     Since the possibility of interruption of latent EBV infection has been suggested by the induction of the lytic virus cycle with chemical substances, other viruses, and by immunosuppression, we hypothesized that the same effect might happen in B. burgdorferi sensu lato infection as happens in Lyme disease patients with positive serology for both agents. We have observed EBV replication in lymphoblastoid cells after superinfection with B. garinii and B. afzelii strains after 1 and 4 h of their interaction. We found that viral and borrelial antigens persisted in the lymphoblasts for 3 and 4 days. Morphological and functional transformation of both agents facilitate their transfer to daughter cells. Association with lymphoblasts and internalization of B. garinii by tube phagocytosis increased replication of viruses more successfully than B. afzelii and chemical inductors. Demonstration of such findings must be interpreted cautiously, but may prove a mixed borrelial and viral cause of severe neurological disease.

Author: Cabral ES, Gelderblom H, Hornung RL, Munson PJ, Martin R, Marques AR.
Journal:  J Infect Dis; 2006 Mar 15; 193(6):849-59.
PubMed ID: 16479520

Abstract:
     Toll-like receptors (TLRs) trigger innate immune responses via the recognition of conserved pathogen-associated molecular patterns. Lipoproteins from Borrelia burgdorferi, the agent of Lyme disease, activate inflammatory cells through TLR2 and TLR1. We show that stimulation of human monocytes with B. burgdorferi lysate, lipidated outer surface protein A, and triacylated lipopeptide Pam3CysSerLys4 results in the up-regulation of both TLR2 and TLR1 but the down-regulation of TLR5, the receptor for bacterial flagellin, and that this effect is mediated via TLR2. TLR4 stimulation had no effect on TLR2, TLR1, and TLR5 expression. Human monocytes stimulated with TLR5 ligands (including p37 or flaA, the minor protein from B. burgdorferi flagella) up-regulated TLR5. In addition, TLR2 stimulation rendered cells hyporesponsive to a TLR5 agonist. These results indicate that diverse stimuli can cause differential TLR expression, and we hypothesize that these changes may be useful for either the pathogen and/or the host.

Author: Cassiani-Ingoni R, Cabral ES, Lünemann JD, Garza Z, Magnus T, Gelderblom H, Munson PJ, Marques A, Martin R.
Journal: J Neuropathol Exp Neurol; 2006 Jun; 65(6):540-8.
PubMed ID: 16783164

Abstract:
     The spirochete Borrelia burgdorferi is the agent of Lyme disease, which causes central nervous system manifestations in up to 20% of patients. We investigated the response of human brain microglial cells, glial progenitors, neurons, astrocytes, as well as peripheral blood monocytes to stimulation with B. burgdorferi. We used oligoarrays to detect changes in the expression of genes important for shaping adaptive and innate immune responses. We found that stimulation with B. burgdorferi lysate increased the expression of Toll-like receptors (TLRs) 1 and 2 in all cell types except neurons. However, despite similarities in global gene profiles of monocytes and microglia, only microglial cells responded to the stimulation with a robust increase in HLA-DR, HLA-DQ, and also coexpressed CD11-c, a dendritic cell marker. In contrast, a large number of HLA-related molecules were repressed at both the RNA and the protein levels in stimulated monocytes, whereas secretion of IL-10 and TNF-alpha was strongly induced. These results show that signaling through TLR1/2 in response to B. burgdorferi can elicit opposite immunoregulatory effects in blood and in brain immune cells, which could play a role in the different susceptibility of these compartments to infection.

Author: Dennis VA, Jefferson A, Singh SR, Ganapamo F, Philipp MT.
Journal: Infect Immun; 2006 Oct; 74(10):5780-9.
PubMed ID: 16988256

Abstract:
     It has been established that interleukin-10 (IL-10) inhibits inflammatory cytokines produced by macrophages in response to Borrelia burgdorferi or its lipoproteins. The mechanism by which IL-10 exerts this anti-inflammatory effect is still unknown. Recent findings indicate that suppressors of cytokine signaling (SOCS) proteins are induced by cytokines and Toll-like receptor (TLR)-mediated stimuli, and in turn they can down-regulate cytokine and TLR signaling in macrophages. Because it is known that SOCS are induced by IL-10 and that B. burgdorferi and its lipoproteins most likely interact via TLR2 or the heterodimers TLR2/1 and/or TLR2/6, we hypothesized that SOCS are induced by IL-10 and B. burgdorferi and its lipoproteins in macrophages and that SOCS may mediate the inhibition by IL-10 of concomitantly elicited cytokines. We report here that mouse J774 macrophages incubated with IL-10 and added B. burgdorferi spirochetes (freeze-thawed, live, or sonicated) or lipidated outer surface protein A (L-OspA) augmented their SOCS1/SOCS3 mRNA and protein expression, with SOCS3 being more abundant. Pam(3)Cys, a synthetic lipopeptide, also induced SOCS1/SOCS3 expression under these conditions, but unlipidated OspA was ineffective. Neither endogenous IL-10 nor the translation inhibitor cycloheximide blocked SOCS1/SOCS3 induction by B. burgdorferi and its lipoproteins, indicating that the expression of other genes is not required. This temporally correlated with the IL-10-mediated inhibition of the inflammatory cytokines IL-1beta, IL-6, IL-12p40, IL-18, and tumor necrosis factor alpha. Our data are evidence to suggest that expression of SOCS is part of the mechanism of IL-10-mediated inhibition of inflammatory cytokines elicited by B. burgdorferi and its lipoproteins.

Author: Jarefors S, Janefjord CK, Forsberg P, Jenmalm MC, Ekerfelt C.
Journal: Clin Exp Immunol; 2007 Jan; 147(1):18-27
PubMed ID: 17177959

Abstract:
     Lyme borreliosis (LB) can, despite adequate antibiotic treatment, develop into a chronic condition with persisting symptoms such as musculoskeletal pain, subjective alteration of cognition and fatigue. The mechanism behind this is unclear, but it has been postulated that an aberrant immunological response might be the cause. In this study we investigated the expression of the T helper 1 (Th1) marker interleukin (IL)-12Rbeta2, the marker for T regulatory cells, forkhead box P3 (FoxP3) and the cytokine profile in patients with a history of chronic LB, subacute LB, previously Borrelia-exposed asymptomatic individuals and healthy controls. Fifty-four individuals (12 chronic LB, 14 subacute LB, 14 asymptomatic individuals and 14 healthy controls) were included in the study and provided a blood sample. Mononuclear cells were separated from the blood and stimulated with antigens. The IL-12Rbeta2 and FoxP3 mRNA expression was analysed with real-time reverse transcription-polymerase chain reaction (RT-PCR). The protein expression of IL-12Rbeta2 on CD3(+), CD4(+), CD8(+) and CD56(+) cells was assessed by flow cytometry. Furthermore, the secretion of interferon (IFN)-gamma, IL-4, IL-5, IL-10, IL-12p70 and IL-13 was analysed by enzyme-linked immunospot (ELISPOT) and/or enzyme-linked immunosorbent assay (ELISA). Chronic LB patients displayed a lower expression of Borrelia-specific IL-12Rbeta2 on CD8(+) cells and also a lower number of Borrelia-specific IFN-gamma-secreting cells compared to asymptomatic individuals. Furthermore, chronic LB patients had higher amounts of Borrelia-specific FoxP3 mRNA than healthy controls. We speculate that this may indicate that a strong Th1 response is of importance for a positive outcome of a Borrelia infection. In addition, regulatory T cells might also play a role, by immunosuppression, in the development of chronic LB.

Author: Aarti Gautam, Saurabh Dixit, Mario T. Philipp, Shree R. Singh, Lisa A. Morici, Deepak Kaushal, and Vida A. Dennis
Journal: Infect. Immun. March 2008 76:3 1153-1162;
PMC : PMC2258815

Abstract:
     Although it is capable of eliciting strong innate and adaptive immune responses, Borrelia burgdorferi often evades immune clearance through largely unknown mechanisms. Our previous studies determined that infected interlukin-10−/− (IL-10−/−) mice show significantly lower B. burgdorferi levels than wild-type (B6) mice and that IL-10 inhibits innate immune responses critical for controlling B. burgdorferi infection. To determine whether virulent B. burgdorferi preferentially enhances IL-10 production, we developed an in vitro coculture medium (RPMI.B) in which both B. burgdorferi and primary macrophages (Mφs) remain viable. B. burgdorferi grew at similar rates and was able to regulate expression of immunoreactive proteins with similar kinetics in RPMI.B and in traditional BSK medium; in contrast, B. burgdorferi cultured in conventional tissue culture medium (RPMI) rapidly lost viability. Coculture of viable B. burgdorferi in RPMI.B with Mφs resulted in more rapid and significant increases in IL-10 transcripts and secreted proteins than coculture with nonviable B. burgdorferi in RPMI, which corresponded with decreased production of proinflammatory cytokines. Addition of live B. burgdorferi to Mφs in RPMI.B also elicited substantially higher IL-10 levels than heat-killed bacteria elicited, confirming that increased IL-10 production was not inherent to coculture in RPMI.B. Transfer of supernatants from B. burgdorferi-stimulated Mφs into naïve Mφ cultures resulted in suppressed activation upon subsequent stimulation with different bacterial agonists, and this suppression was obviated by IL-10-specific antibody. in vivo analyses determined that murine skin samples exhibited substantial upregulation of IL-10 within 24 h of injection of B. burgdorferi. Together, these results suggest that viable B. burgdorferi can suppress early Mφ responses during infection by causing increased release of IL-10.

Infection of susceptible hosts with strains of Borrelia burgdorferi sensu lato causes Lyme disease, which accounts for the majority of vector-borne illness in the United States and most of the temperate regions of Europe and Asia (18, 41). Upon introduction into the host dermis by an infected tick, the spirochetal bacteria must quickly adapt to their vertebrate host, disseminate from the skin to various host tissues, and evade the developing immune responses. This evasion must continue until the bacteria receive appropriate signals that lead to reemergence from their immunoprivileged niche and subsequent migration to and infection of a feeding tick. Although this extended persistence within an immunocompetent host is essential for the existence of the bacteria, the mechanisms that they utilize to escape immune clearance are largely unknown.

Infection with B. burgdorferi triggers strong innate and adaptive immune responses that are largely directed against the ≥127 putative lipoproteins believed to be produced by this spirochete (8, 12, 37). All of these proteins possess a signal II peptidase sequence which can be used to predict their subsequent cleavage and the triacyl modification of the resultant N-terminal cysteine residue. The triacylated lipoproteins are highly immunogenic, as injection of prototypic lipoproteins elicits strong antibody responses and sera collected from infected individuals possess high levels of antibodies that are specific to varioous lipoproteins (31, 45). Additionally, these triacylated lipoproteins directly activate macrophages (Mφs) (30), dendritic cells (35, 42), neutrophils (28), endothelial cells (48, 49), mast cells (24), fibroblasts (11), and B lymphocytes (23) through signaling events mediated by Toll-like receptor 2 (TLR2) (16, 47, 50). Since B. burgdorferi either lacks many of the known bacterial agonists that have stimulatory activities (e.g., lipopolysaccharide [LPS] and lipoteichoic acid) or sequesters them so that they cannot be readily accessed by host immune mediators (e.g., endoflagella), it appears that borrelial lipoproteins are a major focus of both innate and adaptive immune responses to this spirochete. The importance of these interactions is reflected by the relative inability of Mφs derived from TLR2−/− mice to respond to B. burgdorferi and/or its lipoproteins, as well as the high levels of B. burgdorferi that persist in target tissues of infected TLR2−/− mice compared to wild-type mice (47). Interestingly, TLR2−/− mice produce a B. burgdorferi-specific antibody response that appears to be almost identical to that produced by wild-type mice (47, 52), and passive transfer of B. burgdorferi-elicited immune serum from TLR2−/− mice and passive transfer of B. burgdorferi-elicited immune serum from wild-type mice protect naïve mice from infection equally (52), suggesting that appropriate innate immune responses are the most critical responses for bacterial clearance.

The importance of the innate immune responses, particularly Mφs, for controlling B. burgdorferi infection is also reflected by the results of multiple studies assessing the immunosuppressive effects of interleukin-10 (IL-10) on the development of Lyme disease. IL-10 is a significant immunomodulatory cytokine, largely due to its broad but potent anti-inflammatory properties (27). Although IL-10 can be produced by and act upon many cell types, myeloid cells are reported to be the major source of IL-10 production (15). Many of the suppressive immune functions generally associated with IL-10 activities are also mediated through myeloid cells, either by direct downregulation of their production of proinflammatory mediators or by inhibition of their ability to mediate critical antigen-presenting functions to lymphocytes. Exposure of human and murine Mφs to B. burgdorferi elicits significant IL-10 production (7, 13, 14, 29), and addition of exogenous IL-10 to Mφs can suppress the production of proinflammatory mediators produced in response to B. burgdorferi (7). Infection studies have indicated that IL-10−/− mice are significantly better at clearing B. burgdorferi from target tissues than wild-type mice. Infected IL-10−/− mice produce higher levels of B. burgdorferi-specific antibodies than wild-type mice, but the differences are not directly responsible for the enhanced bacterial clearance that occurs (19). IL-10−/− mice also exhibit enhanced innate immune barriers to B. burgdorferi infection compared to wild-type mice, and IL-10−/− Mφs exposed to spirochetes in vitro produce higher levels of multiple proinflammatory mediators than wild-type Mφs (19). Based on these studies, evasion of early innate responses appears to be critical for efficient dissemination and persistence of B. burgdorferi, and suppression of these innate responses by IL-10 is detrimental to effective immune clearance.

Recently, several bacterial and viral pathogens have been shown to promote elevated IL-10 production, to suppress various host immune functions, and to subsequently evade immune clearance (26, 33), raising the possibility that virulent B. burgdorferi might also possess mechanisms that preferentially induce Mφs to upregulate IL-10 production. Because most in vitro analyses of mammalian immune cells are performed in tissue culture medium that does not permit the growth or survival of this fastidious spirochete, it is unlikely that B. burgdorferi could exhibit such a putative virulence mechanism using traditional mammal-based culture conditions. We therefore first developed an in vitro coculture medium that maintains the viability of this fastidious bacterium but does not inherently activate murine Mφs. Subsequent studies using this optimized coculture system indicated that viable B. burgdorferi does potently elicit rapid IL-10 induction by Mφs, and the IL-10 then acts in an autocrine loop to suppress appropriate inflammatory responses necessary to promote efficient immune clearance.

Author: Durovska J, Bazovska S, Ondrisova M, Pancak J.
Journal: Bratisl Lek Listy; 2010; 111(3):153-5.
PubMed ID: 20437826

Abstract:
     BACKGROUND: Lyme borreliosis is a multisystemic disease which affects several organs such as skin, nervous system, joints and the heart. The presented study focused on patients with persisting symptoms of the disease, which could be in correlation with Lyme disease but antiborrelial antibodies were not confirmed by screening tests. MATERIAL AND METHODS: 32 patients with anamnestic data and suspected clinical signs of lyme borreliosis were tested for the presence of antiborrelia antibodies by using ELISA and westernblot analysis and the state of cellular and humoral immunity. RESULTS: All patients had specific antiborrelial antibodies confirmed by using the westernblot in spite of negative ELISA. Immunological investigations revealed a deficiency of cellular immunity in all patients and in a part of them (15.6%) a deficiency of humoral immunity was also found. The presence of different types of autoantibodies was detected in 17 (53.1%) patients. CONCLUSION: In patients with persisting difficulties that could be associated with Lyme disease, it is necessary to use the westernblot test which could prove the presence of specific antibodies. It is probably due to the very low production of specific antibodies caused also by the status of immune deficiency detected in all our patients (Tab. 1, Ref. 11).

Author: Tunev SS, Hastey CJ, Hodzic E, Feng S, Barthold SW, Baumgarth N.
Journal: PLoS Pathog; 2011 May; 7(5):e1002066.
PMC : PMC3102705

Abstract:
     Lymphadenopathy is a hallmark of acute infection with Borrelia burgdorferi, a tick-borne spirochete and causative agent of Lyme borreliosis, but the underlying causes and the functional consequences of this lymph node enlargement have not been revealed. The present study demonstrates that extracellular, live spirochetes accumulate in the cortical areas of lymph nodes following infection of mice with either host-adapted, or tick-borne B. burgdorferi and that they, but not inactivated spirochetes, drive the lymphadenopathy. The ensuing lymph node response is characterized by strong, rapid extrafollicular B cell proliferation and differentiation to plasma cells, as assessed by immunohistochemistry, flow cytometry and ELISPOT analysis, while germinal center reactions were not consistently observed. The extrafollicular nature of this B cell response and its strongly IgM-skewed isotype profile bear the hallmarks of a T-independent response. The induced B cell response does appear, however, to be largely antigen-specific. Use of a cocktail of recombinant, in vivo-expressed B. burgdorferi-antigens revealed the robust induction of borrelia-specific antibody-secreting cells by ELISPOT. Furthermore, nearly a quarter of hybridomas generated from regional lymph nodes during acute infection showed reactivity against a small number of recombinant Borrelia-antigens. Finally, neither the quality nor the magnitude of the B cell responses was altered in mice lacking the Toll-like receptor adaptor molecule MyD88. Together, these findings suggest a novel evasion strategy for B. burgdorferi: subversion of the quality of a strongly induced, potentially protective borrelia-specific antibody response via B. burdorferi's accumulation in lymph nodes.

Author: Gautam A, Dixit S, Philipp MT, Singh SR, Morici LA, Kaushal D, Dennis VA.
Journal: Infect Immun; 2011 Dec; 79(12):4876-92.
PubMed ID: 21947773

Abstract:
     Interleukin-10 (IL-10) modulates inflammatory responses elicited in vitro and in vivo by Borrelia burgdorferi, the Lyme disease spirochete. How IL-10 modulates these inflammatory responses still remains elusive. We hypothesize that IL-10 inhibits effector functions of multiple genes induced by B. burgdorferi in macrophages to control concomitantly elicited inflammation. Because macrophages are essential in the initiation of inflammation, we used mouse J774 macrophages and live B. burgdorferi spirochetes as the model target cell and stimulant, respectively. First, we employed transcriptome profiling to identify genes that were induced by stimulation of cells with live spirochetes and that were perturbed by addition of IL-10 to spirochete cultures. Spirochetes significantly induced upregulation of 347 genes at both the 4-h and 24-h time points. IL-10 inhibited the expression levels, respectively, of 53 and 65 of the 4-h and 24-h genes, and potentiated, respectively, at 4 h and 24 h, 65 and 50 genes. Prominent among the novel identified IL-10-inhibited genes also validated by quantitative real-time PCR (qRT-PCR) were Toll-like receptor 1 (TLR1), TLR2, IRAK3, TRAF1, IRG1, PTGS2, MMP9, IFI44, IFIT1, and CD40. Proteome analysis using a multiplex enzyme-linked immunosorbent assay (ELISA) revealed the IL-10 modulation/and or potentiation of RANTES/CCL5, macrophage inflammatory protein 2 (MIP-2)/CXCL2, IP-10/CXCL10, MIP-1α/CCL3, granulocyte colony-stimulating factor (G-CSF)/CSF3, CXCL1, CXCL5, CCL2, CCL4, IL-6, tumor necrosis factor alpha (TNF-α), IL-1α, IL-1β, gamma interferon (IFN-γ), and IL-9. Similar results were obtained using sonicated spirochetes or lipoprotein as stimulants. Our data show that IL-10 alters effectors induced by B. burgdorferi in macrophages to control concomitantly elicited inflammatory responses. Moreover, for the first time, this study provides global insight into potential mechanisms used by IL-10 to control Lyme disease inflammation.

Author: Liu YC, Simmons DP, Li X, Abbott DW, Boom WH, Harding CV.
Journal:  J Immunol; 2012 Feb 1; 188(3):1019-26
PubMed ID: 22227568

Abstract:
    Pathogens may signal through multiple TLRs with synergistic or antagonistic effects on the induction of cytokines, including type I IFN (IFN-I). IFN-I is typically induced by TLR9, but not TLR2. Moreover, we previously reported that TLR2 signaling by Mycobacterium tuberculosis or other TLR2 agonists inhibited TLR9 induction of IFN-I and IFN-I-dependent MHC-I Ag cross processing. The current studies revealed that lipopeptide-induced TLR2 signaling inhibited induction of first-wave IFN-α and IFN-β mRNA by TLR9, whereas induction of second-wave IFN-I mRNA was not inhibited. TLR2 also inhibited induction of IFN-I by TLR7, another MyD88-dependent IFN-I-inducing receptor, but did not inhibit IFN-I induction by TLR3 or TLR4 (both Toll/IL-1R domain-containing adapter-inducing IFN-β dependent, MyD88 independent). The inhibitory effect of TLR2 was not dependent on new protein synthesis or intercellular signaling. IL-1R-associated kinase 1 (IRAK1) was depleted rapidly (within 10 min) by TLR2 agonist, but not until later (e.g., 2 h) by TLR9 agonist. Because IRAK1 is required for TLR7/9-induced IFN-I production, we propose that TLR2 signaling induces rapid depletion of IRAK1, which impairs IFN-I induction by TLR7/9. This novel mechanism, whereby TLR2 inhibits IFN-I induction by TLR7/9, may shape immune responses to microbes that express ligands for both TLR2 and TLR7/TLR9, or responses to bacteria/virus coinfection.

Author: Xiong Y, Pennini M, Vogel SN, Medvedev AE.
Journal: J Leukoc Biol; 2013 Aug; 94(2):291-300.
PubMed ID: 23695305

Abstract:
     Prior exposure to LPS induces "endotoxin tolerance" that reprograms TLR4 responses to subsequent LPS challenge by altering expression of inflammatory mediators. Endotoxin tolerance is thought to limit the excessive cytokine storm and prevent tissue damage during sepsis but renders the host immunocompromised and susceptible to secondary infections. Tolerance initiated via one TLR can affect cellular responses to challenge via the same TLR ("homotolerance") or through different TLRs ("heterotolerance"). IRAK4, an essential component of the MyD88-dependent pathway, functions as a kinase and an adapter, activating subsets of divergent signaling pathways. In this study, we addressed mechanistically the role of IRAK4 kinase activity in TLR4- and TLR2-induced tolerance using macrophages from WT versus IRAK4(KDKI) mice. Whereas IRAK4 kinase deficiency decreased LPS signaling, it did not prevent endotoxin tolerance, as endotoxin pretreatment of WT and IRAK4(KDKI) macrophages inhibited LPS-induced MAPK phosphorylation, degradation of IκB-α and recruitment of p65 to the TNF-α promoter, expression of proinflammatory cytokines, and increased levels of A20 and IRAK-M. Pretreatment of WT macrophages with Pam3Cys, a TLR2-TLR1 agonist, ablated p-p38 and p-JNK in response to challenge with Pam3Cys and LPS, whereas IRAK4(KDKI) macrophages exhibited attenuated TLR2-elicited homo- and heterotolerance at the level of MAPK activation. Thus, IRAK4 kinase activity is not required for the induction of endotoxin tolerance but contributes significantly to TLR2-elicited homo- and heterotolerance.

Author: Elsner RA, Hastey CJ, Baumgarth N.
Journal: Infect Immun; 2015 Jan; 83(1):48-56.
PubMed ID: 25312948

Abstract:
     CD4 T cells are crucial for enhancing B cell-mediated immunity, supporting the induction of high-affinity, class-switched antibody responses, long-lived plasma cells, and memory B cells. Previous studies showed that the immune response to Borrelia burgdorferi appears to lack robust T-dependent B cell responses, as neither long-lived plasma cells nor memory B cells form for months after infection, and nonswitched IgM antibodies are produced continuously during this chronic disease. These data prompted us to evaluate the induction and functionality of B. burgdorferi infection-induced CD4 T(FH) cells. We report that CD4 T cells were effectively primed and T(FH) cells induced after B. burgdorferi infection. These CD4 T cells contributed to the control of B. burgdorferi burden and supported the induction of B. burgdorferi-specific IgG responses. However, while affinity maturation of antibodies against a prototypic T-dependent B. burgdorferi protein, Arthritis-related protein (Arp), were initiated, these increases were reversed later, coinciding with the previously observed involution of germinal centers. The cessation of affinity maturation was not due to the appearance of inhibitory or exhausted CD4 T cells or a strong induction of regulatory T cells. In vitro T-B cocultures demonstrated that T cells isolated from B. burgdorferi-infected but not B. burgdorferi-immunized mice supported the rapid differentiation of B cells into antibody-secreting plasma cells rather than continued proliferation, mirroring the induction of rapid short-lived instead of long-lived T-dependent antibody responses in vivo. The data further suggest that B. burgdorferi infection drives the humoral response away from protective, high-affinity, and long-lived antibody responses and toward the rapid induction of strongly induced, short-lived antibodies of limited efficacy.

Author: Elsner RA, Hastey CJ, Olsen KJ, Baumgarth N.,
Journal: PLoS Pathog; 2015 Jul; 11(7):e1004976.
PMC: PMC4489802

Abstract:
     Lyme Disease caused by infection with Borrelia burgdorferi is an emerging infectious disease and already by far the most common vector-borne disease in the U.S. Similar to many other infections, infection with B. burgdorferi results in strong antibody response induction, which can be used clinically as a diagnostic measure of prior exposure. However, clinical studies have shown a sometimes-precipitous decline of such antibodies shortly following antibiotic treatment, revealing a potential deficit in the host’s ability to induce and/or maintain long-term protective antibodies. This is further supported by reports of frequent repeat infections with B. burgdorferi in endemic areas. The mechanisms underlying such a lack of long-term humoral immunity, however, remain unknown. We show here that B. burgdorferi infected mice show a similar rapid disappearance of Borrelia-specific antibodies after infection and subsequent antibiotic treatment. This failure was associated with development of only short-lived germinal centers, micro-anatomical locations from which long-lived immunity originates. These showed structural abnormalities and failed to induce memory B cells and long-lived plasma cells for months after the infection, rendering the mice susceptible to reinfection with the same strain of B. burgdorferi. The inability to induce long-lived immune responses was not due to the particular nature of the immunogenic antigens of B. burgdorferi, as antibodies to both T-dependent and T-independent Borrelia antigens lacked longevity and B cell memory induction. Furthermore, influenza immunization administered at the time of Borrelia infection also failed to induce robust antibody responses, dramatically reducing the protective antiviral capacity of the humoral response. Collectively, these studies show that B. burgdorferi-infection results in targeted and temporary immunosuppression of the host and bring new insight into the mechanisms underlying the failure to develop long-term immunity to this emerging disease threat.

Jul 5, 2015 | Health

Abstract:
     The bacteria that cause Lyme disease are able to trick an animal’s immune system into not launching a full-blown immune response or developing lasting immunity to the disease, report researchers at the University of California, Davis.
 
The discovery may explain why some human patients remain vulnerable to repeat infections by the same strain of bacteria, especially in regions where Lyme disease is prevalent. It also suggests that blood tests may not be an effective method for detecting previous exposure to Lyme disease, by far the most common vector-borne disease in the United States and Europe. ...