Short-Chain Fatty Acids Alter Metabolic and Virulence Attributes of Borrelia burgdorferi.

Borrelia burgdorferi responds to a variety of host-derived factors and appropriately alters its gene expression for adaptation under different host-specific conditions. We previously showed that various levels of acetate, a short-chain fatty acid (SCFA), altered the protein profile of B. burgdorferi In this study, we determined the effects of other physiologically relevant SCFAs in the regulation of metabolic/virulence-associated proteins using mutant borrelial strains. No apparent increase in the synthesis of outer surface protein C (OspC) was noted when a carbon storage regulator A (csrA of B. burgdorferi, or csrABb ) mutant (mt) was propagated within dialysis membrane chambers implanted within rat peritoneal cavity, while the parental wild type (wt; B31-A3 strain) and csrABb cis-complemented strain (ct) had increased OspC with a reciprocal reduction in OspA levels. Growth rates of wt, mt, ct, 7D (csrABb mutant lacking 7 amino acids at the C terminus), and 8S (csrABb with site-specific changes altering its RNA-binding properties) borrelial strains were similar in the presence of acetate. Increased levels of propionate and butyrate reduced the growth rates of all strains tested, with mt and 8S exhibiting profound growth deficits at higher concentrations of propionate. Transcriptional levels of rpoS and ospC were elevated on supplementation of SCFAs compared to those of untreated spirochetes. Immunoblot analysis revealed elevated levels of RpoS, OspC, and DbpA with increased levels of SCFAs. Physiological levels of SCFAs prevalent in select human and rodent fluids were synergistic with mammalian host temperature and pH to increase the levels of aforementioned proteins, which could impact the colonization of B. burgdorferi during the mammalian phase of infection.

Ensayo de infección artificial de garrapatas cubanas con Borrelia burgdorferi sensu stricto / Artificial infection assay of Cuban ticks with Borrelia burgdorferi sensu stricto

Como es conocido, Borrelia spp. constituye un grupo importante de patógenos bacterianos transmitidos por garrapatas, a excepción de Borrelia recurrentis que es transmitida por piojos del cuerpo. Estos microorganismos son los causantes de borreliosis o enfermedad de Lyme y fiebre recurrente.1El complejo B. burgdorferi sensu lato es causante de la enfermedad de Lyme, y el principal vector descrito lo constituyen las garrapatas duras del género Ixodes.2 Recientemente se ha reportado en México y Brasil la presencia de ADN de B. burgdorferi sensu stricto,3,4 una de las 19 genomaespecies del complejo, en garrapatas Amblyomma cajennense, pero se desconoce si esta especie es capaz de transmitir las borrelias a un nuevo hospedero. En Cuba, a partir de evidencias serológicas específicas de la infección por este agente y teniendo en cuenta las especies de ixódidos que prevalecen, así como sus características ecológicas y antropofílicas, las garrapatas A. cajennense y Rhipicephalus sanguineus se consideran vectores potenciales de las borrelias.5Sobre la base de los hallazgos e hipótesis anteriormente mencionados se hace necesario iniciar investigaciones para comprobar si otras especies diferentes de Ixodes spp. son capaces de transmitir las borrelias. Ello requiere contar con un método sencillo y eficaz que permita la infección artificial de ixódidos. Se han reportado disímiles estrategias con estos fines, entre las que se incluyen el empleo de cámaras de alimentación con membranas naturales o artificiales, la infusión por enema, la inoculación hemocélica y la alimentación por capilares...

Ensayo de infección artificial de garrapatas cubanas con Borrelia burgdorferi sensu stricto / Artificial infection assay of Cuban ticks with Borrelia burgdorferi sensu stricto

Como es conocido, Borrelia spp. constituye un grupo importante de patógenos bacterianos transmitidos por garrapatas, a excepción de Borrelia recurrentis que es transmitida por piojos del cuerpo. Estos microorganismos son los causantes de borreliosis o enfermedad de Lyme y fiebre recurrente.1El complejo B. burgdorferi sensu lato es causante de la enfermedad de Lyme, y el principal vector descrito lo constituyen las garrapatas duras del género Ixodes.2 Recientemente se ha reportado en México y Brasil la presencia de ADN de B. burgdorferi sensu stricto,3,4 una de las 19 genomaespecies del complejo, en garrapatas Amblyomma cajennense, pero se desconoce si esta especie es capaz de transmitir las borrelias a un nuevo hospedero. En Cuba, a partir de evidencias serológicas específicas de la infección por este agente y teniendo en cuenta las especies de ixódidos que prevalecen, así como sus características ecológicas y antropofílicas, las garrapatas A. cajennense y Rhipicephalus sanguineus se consideran vectores potenciales de las borrelias.5Sobre la base de los hallazgos e hipótesis anteriormente mencionados se hace necesario iniciar investigaciones para comprobar si otras especies diferentes de Ixodes spp. son capaces de transmitir las borrelias. Ello requiere contar con un método sencillo y eficaz que permita la infección artificial de ixódidos. Se han reportado disímiles estrategias con estos fines, entre las que se incluyen el empleo de cámaras de alimentación con membranas naturales o artificiales, la infusión por enema, la inoculación hemocélica y la alimentación por capilares...(AU)

Borrelia burgdorferi vlsE antigenic variation is not mediated by RecA.

RecA is a key protein linking genetic recombination to DNA replication and repair in bacteria. Previous functional characterization of Borrelia burgdorferi RecA indicated that the protein is mainly involved in genetic recombination rather than DNA repair. Genetic recombination may play a role in B. burgdorferi persistence by generation of antigenic variation. We report here the isolation of a recA null mutant in an infectious B. burgdorferi strain. Comparison of the in vitro growth characteristics of the mutant with those of the wild-type strain under various conditions showed no significant differences. While the RecA mutant was moderately more sensitive to UV irradiation and mitomycin C than the wild-type strain, the lack of RecA abolished allelic exchange in the mutant. Absence of RecA did not affect the ability of the mutant to infect mice. However, the RecA mutant was attenuated for joint infection in competitive-infection assays with the wild-type strain. vlsE sequence variation in mice was observed in both wild-type and RecA mutant spirochetes, indicating that the mechanism of antigenic variation is not homologous genetic recombination.

Expression of ICAM-1, ICAM-2, NCAM-1 and VCAM-1 by human synovial cells exposed to Borrelia burgdorferi in vitro.

The interaction of resident tissue cells with migratory inflammatory cells is essential for the recruitment of immune effector cells to inflammatory sites. The sustained expression of adhesion molecules in the synovium of patients with chronic Lyme arthritis seems to contribute to this chronic inflammation. Whether cell adhesion molecules influence the early steps of Borreliosis is unclear. Therefore, we examined the expression of ICAM-1, ICAM-2, VCAM-1 and NCAM-1 in synovial cells exposed to two different Borrelia burgdorferi sensu stricto strains Geho and B31. The mRNA expression of ICAM-1, ICAM-2, VCAM-1 and NCAM-1 was not changed in synovial cells exposed to B31. Whereas ICAM-2 and VCAM-1 was upregulated, NCAM-1 mRNA was downregulated and ICAM-1 mRNA was unchanged by strain Geho. The ICAM-1 protein expression on the synovial cell surface was downregulated by both strains. Differential regulation of adhesion molecule mRNA, and subsequent high turnover or elevated shedding from the cell membrane may contribute to early pathogenesis in Lyme arthritis.

Myeloid differentiation antigen 88 deficiency impairs pathogen clearance but does not alter inflammation in Borrelia burgdorferi-infected mice.

The spirochete Borrelia burgdorferi causes acute inflammation in mice that resolves with the development of pathogen-specific adaptive immunity. B. burgdorferi lipoproteins activate innate immune cells via Toll-like receptor 2 (TLR2), but TLR2-deficient mice are not resistant to B. burgdorferi-induced disease, suggesting the involvement of other TLRs or non-TLR mechanisms in the induction of acute inflammation. For this study, we used mice that were deficient in the intracellular adapter molecule myeloid differentiation antigen 88 (MyD88), which is required for all TLR-induced inflammatory responses, to determine whether the interruption of this pathway would alter B. burgdorferi-induced disease. Infected MyD88(-/-) mice developed carditis and arthritis, similar to the disease in wild-type (WT) mice analyzed at its peak (days 14 and 28) and during regression (day 45). MyD88(-/-) macrophages produced tumor necrosis factor alpha only when spirochetes were opsonized, suggesting a role for B. burgdorferi-specific antibody in disease expression. MyD88(-/-) mice produced stronger pathogen-specific Th2-dependent immunoglobulin G1 (IgG1) responses than did WT mice, and their IgM titers remained significantly elevated through 90 days of infection. Despite specific antibodies, the pathogen burden was 250-fold higher in MyD88(-/-) mice than in WT mice 45 days after infection; by 90 days of infection, the pathogen burden had diminished substantially in MyD88(-/-) mice, but it was still elevated compared to that in WT mice. The elevated pathogen burden may be explained in part by the finding that MyD88(-/-) peritoneal macrophages could ingest spirochetes but degraded them more slowly than WT macrophages. Our results show that MyD88-dependent signaling pathways are not required for B. burgdorferi-induced inflammation but are necessary for the efficient control of the pathogen burden by phagocytes.

Cyclooxygenase 2 activity modulates the severity of murine Lyme arthritis.

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