Toll-like receptors 1 and 2 heterodimers alter Borrelia burgdorferi gene expression in mice and ticks.

Borrelia burgdorferi, the agent of Lyme disease, is recognized by Toll-like receptor (TLR) 1 and 2 heterodimers. Microarray analysis of in vivo B. burgdorferi gene expression in murine skin showed that several genes were altered in TLR1/2-deficient animals compared with wild-type mice. For example, expression of bbe21 (a gene involved in B. burgdorferi lp25 plasmid maintenance) and bb0665 (a gene encoding a glycosyl transferase) were higher in TLR1/2-deficient mice than in control animals. In contrast, messenger RNA levels for bb0731 (a spoJ-like gene) and bba74 (a gene encoding a periplasmic protein) were lower in TLR1/2-deficient mice than in wild-type animals. The expression profiles of some of these genes were altered similarly in B. burgdorferi-infected ticks fed on control or TLR1/2-deficient mice. Quantitative reverse-transcription polymerase chain reaction analysis supported the microarray analysis and suggested that spirochete gene expression is altered by the milieu created by specific host TLRs, both in the murine host and in the arthropod vector.

Inactivation of JNK1 enhances innate IL-10 production and dampens autoimmune inflammation in the brain.

Environmental insults such as microbial pathogens can contribute to the activation of autoreactive T cells, leading to inflammation of target organs and, ultimately, autoimmune disease. Various infections have been linked to multiple sclerosis and its animal counterpart, autoimmune encephalomyelitis. The molecular process by which innate immunity triggers autoreactivity is not currently understood. By using a mouse model of multiple sclerosis, we found that the genetic loss of the MAPK, c-Jun N-terminal kinase 1 (JNK1), enhances IL-10 production, rendering innate myeloid cells unresponsive to certain microbes and less capable of generating IL-17-producing, encephalitogenic T cells. Moreover, JNK1-deficient central nervous system myeloid cells are unable to respond to effector T cell inflammatory cytokines, preventing further progression to neuroinflammation. Thus, we have identified the JNK1 signal transduction pathway in myeloid cells to be a critical component of a regulatory circuit mediating inflammatory responses in autoimmune disease. Our findings provide further insights into the pivotal MAPK-regulated network of innate and adaptive cytokines in the progression to autoimmunity.

Preferential presence of decorin-binding protein B (BBA25) and BBA50 antibodies in cerebrospinal fluid of patients with neurologic Lyme disease.

Borrelia burgdorferi antibodies preferentially present in cerebrospinal fluid (CSF) were examined by differentially probing a B. burgdorferi expression library with CSF and sera from patients with neurologic Lyme disease. Several phage clones selectively reacted with CSF, and these genes were then expressed in recombinant form and used to detect specific antibody in an enzyme-linked immunosorbent assay. Decorin-binding protein B (BBA25) and BBA50 (hypothetical protein) elicited immunoglobulin G (IgG) or IgM detectable in CSF-but not sera-of patients, demonstrating preferential antibody production during neuroborreliosis.

OspB antibody prevents Borrelia burgdorferi colonization of Ixodes scapularis.

Borrelia burgdorferi outer surface protein OspB is expressed by spirochetes in the Ixodes scapularis gut. ospB is transcribed from a bicistronic operon with ospA, a known spirochete adhesion gene in the tick gut. Here we examine whether OspB also has a specific function in ticks. OspB specifically binds to a protein or protein complex within the tick gut. We also assessed whether selected nonborreliacidal OspB antibodies or F(ab)(2) fragments interfere with B. burgdorferi-tick attachment in vivo. We examined engorged ticks that fed on B. burgdorferi N40-infected scid mice that had been treated with OspB F(ab)(2) fragments. Control F(ab)(2) fragments did not interfere with B. burgdorferi colonization of the tick gut, whereas OspB F(ab)(2) fragments significantly inhibited the attachment of spirochetes to the tick gut. These studies show that nonbactericidal OspB antibodies interfere with B. burgdorferi colonization of I. scapularis, highlighting a specific role for OspB in spirochete- arthropod interactions and suggesting new antibody-mediated strategies for interfering with B. burgdorferi transmission.

OspC facilitates Borrelia burgdorferi invasion of Ixodes scapularis salivary glands.

Outer surface protein C (OspC) is a differentially expressed major surface lipoprotein of Borrelia burgdorferi. ospC is swiftly upregulated when spirochetes leave the Ixodes scapularis tick gut, migrate to the salivary gland, and exit the arthropod vector. Here we show that OspC strongly binds to the tick salivary gland, suggesting a role for OspC in spirochete adherence to this tissue. In vivo studies using a murine model of Lyme borreliosis showed that while OspC F(ab)(2) fragments did not influence either the viability of spirochetes or ospC gene expression, they did interfere with B. burgdorferi invasion of tick salivary glands. We then generated ospC knockout spirochetes in an infectious clone of B. burgdorferi and examined them within the vector. OspC-deficient or wild-type spirochetes persisted equally within the gut of unfed ticks and multiplied during the tick engorgement; however, unlike wild-type B. burgdorferi, the mutants were unable to invade salivary glands. Salivary gland colonization of OspC-deficient spirochetes was completely restored when this mutant was complemented in trans with a plasmid harboring the wild-type ospC gene. These studies conclusively demonstrate the importance of OspC in the invasion of tick salivary glands by B. burgdorferi, a critical step in the transmission of spirochetes from the arthropod vector to the mammalian host.