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Lymphoadenopathy during lyme borreliosis is caused by spirochete migration-induced specific B cell activation.

Tunev SS, Hastey CJ, Hodzic E, Feng S, Barthold SW, Baumgarth N - PLoS Pathog. (2011)

Bottom Line: The induced B cell response does appear, however, to be largely antigen-specific.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.

View Article: PubMed Central - PubMed

Affiliation: Center for Comparative Medicine, University of California Davis, Davis, California, United States of America.

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.

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Lymphadenopathy and lymph node B cell activation are independent of MyD88-signaling.Control C57BL/6 (wildtype) and congenic MyD88−/− mice (n = 6 per group) were infected with host-adapted B. burgdorferi for 10 days. Lymph nodes were harvested and compared for (A) total cellularity and (B) numbers of CD4, CD8 and CD19 as assessed by flow cytometry. ELISPOT analysis was conducted to determine numbers of (C) borrelia-specific IgM or (D) all Ig-isotype secreting borrelia-specific cells. For scatter plots, each symbol represents the result from an individual animal. Lines indicate mean of the group. Bar chart shows the mean values ± SD. Results are pooled from two independent experiments. Statistical analysis for (A) (C) (D) was conducted by Student's t test and (B) by two-way ANOVA. None of the data showed significant differences between control and MyD88−/− mice.
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ppat-1002066-g007: Lymphadenopathy and lymph node B cell activation are independent of MyD88-signaling.Control C57BL/6 (wildtype) and congenic MyD88−/− mice (n = 6 per group) were infected with host-adapted B. burgdorferi for 10 days. Lymph nodes were harvested and compared for (A) total cellularity and (B) numbers of CD4, CD8 and CD19 as assessed by flow cytometry. ELISPOT analysis was conducted to determine numbers of (C) borrelia-specific IgM or (D) all Ig-isotype secreting borrelia-specific cells. For scatter plots, each symbol represents the result from an individual animal. Lines indicate mean of the group. Bar chart shows the mean values ± SD. Results are pooled from two independent experiments. Statistical analysis for (A) (C) (D) was conducted by Student's t test and (B) by two-way ANOVA. None of the data showed significant differences between control and MyD88−/− mice.

Mentions: Non-specific mitogenic stimulation of B cells with Borrelia lipoproteins in vitro has been reported previously [9]–[16]. OspA, a surface lipoprotein that is strongly expressed by Borrelia in culture, but down-regulated upon infection of a mammalian host, was shown to be responsible for at least some of the mitogenic activity [11], [14]. While host-adapted spirochetes are not expected to express significant amounts of OspA, other proteins or lipids may provide mitogenic signals to B cells in vivo. Therefore, we determined the role of the adaptor protein MyD88, important in TLR and IL-1-mediated innate signaling, in regulation of initial B cell activation and/or the lymph node enlargement. A previous study found impaired pathogen-clearance and alterations in the antibody-isotype profile of serum antibodies in mice lacking MyD88 [42]. MyD88−/− mice and congenic control mice were infected with host-adapted spirochetes for ten days. The analysis revealed no role for MyD88 in the quality or magnitude of the lymphadenopathy. Regional lymph nodes from MyD88−/− mice had similar cell numbers on day 10 of infection (Figure 7A), with similar predominance of CD19+ B cells compared to control mice (Figure 7B). Furthermore, there was no difference in the number of Borrelia-specific IgM or total Ig secreting cells in the lymph nodes (Figures 7C, 7D). Thus, MyD88-dependent innate signaling is not driving the induction of lymphadenopathy, nor the massive activation of B cell responses associated with Lyme borreliosis. Together with the strong antigen-specific B cell responses measured by hybridoma generation, the results suggest that Borrelia-infection induces a specific, albeit largely extrafollicular B cell response as a result of the accumulation of live B. burgdorferi in lymph nodes.


Lymphoadenopathy during lyme borreliosis is caused by spirochete migration-induced specific B cell activation.

Tunev SS, Hastey CJ, Hodzic E, Feng S, Barthold SW, Baumgarth N - PLoS Pathog. (2011)

Lymphadenopathy and lymph node B cell activation are independent of MyD88-signaling.Control C57BL/6 (wildtype) and congenic MyD88−/− mice (n = 6 per group) were infected with host-adapted B. burgdorferi for 10 days. Lymph nodes were harvested and compared for (A) total cellularity and (B) numbers of CD4, CD8 and CD19 as assessed by flow cytometry. ELISPOT analysis was conducted to determine numbers of (C) borrelia-specific IgM or (D) all Ig-isotype secreting borrelia-specific cells. For scatter plots, each symbol represents the result from an individual animal. Lines indicate mean of the group. Bar chart shows the mean values ± SD. Results are pooled from two independent experiments. Statistical analysis for (A) (C) (D) was conducted by Student's t test and (B) by two-way ANOVA. None of the data showed significant differences between control and MyD88−/− mice.
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Related In: Results  -  Collection

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ppat-1002066-g007: Lymphadenopathy and lymph node B cell activation are independent of MyD88-signaling.Control C57BL/6 (wildtype) and congenic MyD88−/− mice (n = 6 per group) were infected with host-adapted B. burgdorferi for 10 days. Lymph nodes were harvested and compared for (A) total cellularity and (B) numbers of CD4, CD8 and CD19 as assessed by flow cytometry. ELISPOT analysis was conducted to determine numbers of (C) borrelia-specific IgM or (D) all Ig-isotype secreting borrelia-specific cells. For scatter plots, each symbol represents the result from an individual animal. Lines indicate mean of the group. Bar chart shows the mean values ± SD. Results are pooled from two independent experiments. Statistical analysis for (A) (C) (D) was conducted by Student's t test and (B) by two-way ANOVA. None of the data showed significant differences between control and MyD88−/− mice.
Mentions: Non-specific mitogenic stimulation of B cells with Borrelia lipoproteins in vitro has been reported previously [9]–[16]. OspA, a surface lipoprotein that is strongly expressed by Borrelia in culture, but down-regulated upon infection of a mammalian host, was shown to be responsible for at least some of the mitogenic activity [11], [14]. While host-adapted spirochetes are not expected to express significant amounts of OspA, other proteins or lipids may provide mitogenic signals to B cells in vivo. Therefore, we determined the role of the adaptor protein MyD88, important in TLR and IL-1-mediated innate signaling, in regulation of initial B cell activation and/or the lymph node enlargement. A previous study found impaired pathogen-clearance and alterations in the antibody-isotype profile of serum antibodies in mice lacking MyD88 [42]. MyD88−/− mice and congenic control mice were infected with host-adapted spirochetes for ten days. The analysis revealed no role for MyD88 in the quality or magnitude of the lymphadenopathy. Regional lymph nodes from MyD88−/− mice had similar cell numbers on day 10 of infection (Figure 7A), with similar predominance of CD19+ B cells compared to control mice (Figure 7B). Furthermore, there was no difference in the number of Borrelia-specific IgM or total Ig secreting cells in the lymph nodes (Figures 7C, 7D). Thus, MyD88-dependent innate signaling is not driving the induction of lymphadenopathy, nor the massive activation of B cell responses associated with Lyme borreliosis. Together with the strong antigen-specific B cell responses measured by hybridoma generation, the results suggest that Borrelia-infection induces a specific, albeit largely extrafollicular B cell response as a result of the accumulation of live B. burgdorferi in lymph nodes.

Bottom Line: The induced B cell response does appear, however, to be largely antigen-specific.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.

View Article: PubMed Central - PubMed

Affiliation: Center for Comparative Medicine, University of California Davis, Davis, California, United States of America.

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.

Show MeSH
Related in: MedlinePlus