Dataset Information

Cutaneous Exposure to Clinically Relevant Lone Star Ticks Promotes IgE Production and Hypersensitivity through CD4+ T Cell- and MyD88-Dependent Pathways in Mice.

ABSTRACT: Tick-borne allergies are a growing public health concern and have been associated with the induction of IgE-mediated food allergy to red meat. However, despite the increasing prevalence of tick bite-induced allergies, the mechanisms by which cutaneous exposure to ticks leads to sensitization and the production of IgE Abs are poorly understood. To address this question, an in vivo approach was used to characterize the IgE response to lone star tick proteins administered through the skin of mice. The results demonstrated that tick sensitization and challenge induced a robust production of IgE Abs and supported a role for IgE-mediated hypersensitivity reactions in sensitized animals following oral administration of meat. The induction of IgE responses was dependent on cognate CD4+ T cell help during both the sensitization phase and challenge phase with cutaneous tick exposure. In addition, IgE production was dependent on B cell-intrinsic MyD88 expression, suggesting an important role for TLR signaling in B cells to induce IgE responses to tick proteins. This model of tick-induced IgE responses could be used to study the factors within tick bites that cause allergies and to investigate how sensitization to food Ags occurs through the skin that leads to IgE production.

SUBMITTER: Chandrasekhar JL

PROVIDER: S-EPMC6684363 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Cutaneous Exposure to Clinically Relevant Lone Star Ticks Promotes IgE Production and Hypersensitivity through CD4<sup>+</sup> T Cell- and MyD88-Dependent Pathways in Mice.

Chandrasekhar Jessica L JL Cox Kelly M KM Loo William M WM Qiao Hui H Tung Kenneth S KS Erickson Loren D LD

Journal of immunology (Baltimore, Md. : 1950) 20190703 4

Tick-borne allergies are a growing public health concern and have been associated with the induction of IgE-mediated food allergy to red meat. However, despite the increasing prevalence of tick bite-induced allergies, the mechanisms by which cutaneous exposure to ticks leads to sensitization and the production of IgE Abs are poorly understood. To address this question, an in vivo approach was used to characterize the IgE response to lone star tick proteins administered through the skin of mice. ...[more]

PMID: 31270149

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Project description:The Lone Star tick, Amblyomma americanum, transmits several bacterial pathogens including species of Anaplasma and Ehrlichia. Amblyomma americanum also hosts a number of non-pathogenic bacterial endosymbionts. Recent studies of other arthropod and insect vectors have documented that commensal microflora can influence transmission of vector-borne pathogens; however, little is known about tick microbiomes and their possible influence on tick-borne diseases. Our objective was to compare bacterial communities associated with A. americanum, comparing Anaplasma/Ehrlichia -infected and uninfected ticks. Field-collected questing specimens (n = 50) were used in the analyses, of which 17 were identified as Anaplasma/Ehrlichia infected based on PCR amplification and sequencing of groEL genes. Bacterial communities from each specimen were characterized using Illumina sequencing of 16S rRNA gene amplicon libraries. There was a broad range in diversity between samples, with inverse Simpson's Diversity indices ranging from 1.28-89.5. There were no statistical differences in the overall microbial community structure between PCR diagnosed Anaplasma/Ehrlichia-positive and negative ticks, but there were differences based on collection method (P < 0.05), collection site (P < 0.05), and sex (P < 0.1) suggesting that environmental factors may structure A. americanum microbiomes. Interestingly, there was not always agreement between Illumina sequencing and PCR diagnostics: Ehrlichia was identified in 16S rRNA gene libraries from three PCR-negative specimens; conversely, Ehrlichia was not found in libraries of six PCR-positive ticks. Illumina sequencing also helped identify co-infections, for example, one specimen had both Ehrlichia and Anaplasma. Other taxa of interest in these specimens included Coxiella, Borrelia, and Rickettsia. Identification of bacterial community differences between specimens of a single tick species from a single geographical site indicates that intra-species differences in microbiomes were not due solely to pathogen presence/absence, but may be also driven by vector life history factors, including environment, life stage, population structure, and host choice.

Project description:The lone star tick (Amblyomma americanum) is an abundant and aggressive biter of humans, domestic animals, and wildlife in the southeastern-central USA and an important vector of several known and suspected zoonotic bacterial pathogens. However, the biological drivers of bacterial community variation in this tick are still poorly defined. Knowing the community context in which tick-borne bacterial pathogens exist and evolve is required to fully understand the ecology and immunobiology of the ticks and to design effective public health and veterinary interventions. We performed a metagenomic survey of the bacterial communities of questing A. americanum and tested 131 individuals (66 nymphs, 24 males, and 41 females) from five sites in three states. Pyrosequencing was performed with barcoded eubacterial primers targeting variable 16S rRNA gene regions 5-3. The bacterial communities were dominated by Rickettsia (likely R. amblyommii) and an obligate Coxiella symbiont, together accounting for 6.7-100% of sequences per tick. DNAs from Midichloria, Borrelia, Wolbachia, Ehrlichia, Pseudomonas, or unidentified Bacillales, Enterobacteriaceae, or Rhizobiales groups were also detected frequently. Wolbachia and Midichloria significantly co-occurred in Georgia (p<0.00001), but not in other states. The significance of the Midichloria-Wolbachia co-occurrence is unknown. Among ticks collected in Georgia, nymphs differed from adults in both the composition (p?=?0.002) and structure (p?=?0.002) of their bacterial communities. Adults differed only in their community structure (p?=?0.002) with males containing more Rickettsia and females containing more Coxiella. Comparisons among adult ticks collected in New York and North Carolina supported the findings from the Georgia collection despite differences in geography, collection date, and sample handling, implying that the differences detected are consistent attributes. The data also suggest that some members of the bacterial community change during the tick life cycle and that some sex-specific attributes may be detectable in nymphs.

Dataset Information

Cutaneous Exposure to Clinically Relevant Lone Star Ticks Promotes IgE Production and Hypersensitivity through CD4+ T Cell- and MyD88-Dependent Pathways in Mice.

Publications

Cutaneous Exposure to Clinically Relevant Lone Star Ticks Promotes IgE Production and Hypersensitivity through CD4<sup>+</sup> T Cell- and MyD88-Dependent Pathways in Mice.

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