Borrelia Burgdorferi Induces a Type I Interferon Response During Early Stages of Disseminated Infection in Mice

BACKGROUND: Lyme borrelia genotypes differ in their capacity to cause disseminated disease. Gene array analysis was employed to profile the host transcriptome induced by Borrelia burgdorferi strains with different capacities for causing disseminated disease in the blood of C3H/HeJ mice during early infection. RESULTS: B. burgdorferi B515, a clinical isolate that causes disseminated infection in mice, differentially regulated 236 transcripts (P \u3c 0.05 by ANOVA, with fold change of at least 2). The 216 significantly induced transcripts included interferon (IFN)-responsive genes and genes involved in immunity and inflammation. In contrast, B. burgdorferi B331, a clinical isolate that causes transient skin infection but does not disseminate in C3H/HeJ mice, stimulated changes in only a few genes (1 induced, 4 repressed). Transcriptional regulation of type I IFN and IFN-related genes was measured by quantitative RT-PCR in mouse skin biopsies collected from the site of infection 24 h after inoculation with B. burgdorferi. The mean values for transcripts of Ifnb, Cxcl10, Gbp1, Ifit1, Ifit3, Irf7, Mx1, and Stat2 were found to be significantly increased in B. burgdorferi strain B515-infected mice relative to the control group. In contrast, transcription of these genes was not significantly changed in response to B. burgdorferi strain B331 or B31-4, a mutant that is unable to disseminate. CONCLUSIONS: These results establish a positive association between the disseminating capacity of B. burgdorferi and early type I IFN induction in a murine model of Lyme disease

Landscape structure affects the prevalence and distribution of a tick-borne zoonotic pathogen

Background Landscape structure can affect pathogen prevalence and persistence with consequences for human and animal health. Few studies have examined how reservoir host species traits may interact with landscape structure to alter pathogen communities and dynamics. Using a landscape of islands and mainland sites we investigated how natural landscape fragmentation affects the prevalence and persistence of the zoonotic tick-borne pathogen complex Borrelia burgdorferi(sensu lato), which causes Lyme borreliosis. We hypothesized that the prevalence of B. burgdorferi (s.l.) would be lower on islands compared to the mainland and B. afzelii, a small mammal specialist genospecies, would be more affected by isolation than bird-associated B. garinii and B. valaisiana and the generalist B. burgdorferi (sensu stricto). Methods Questing (host-seeking) nymphal I. Ricinus ticks (n = 6567) were collected from 12 island and 6 mainland sites in 2011, 2013 and 2015 and tested for B. burgdorferi(s.l.). Deer abundance was estimated using dung transects. Results The prevalence of B. burgdorferi (s.l.) was significantly higher on the mainland (2.5%, 47/1891) compared to island sites (0.9%, 44/4673) (P < 0.01). While all four genospecies of B. burgdorferi (s.l.) were detected on the mainland, bird-associated species B. garinii and B. valaisiana and the generalist genospecies B. burgdorferi(s.s.) predominated on islands. Conclusion We found that landscape structure influenced the prevalence of a zoonotic pathogen, with a lower prevalence detected among island sites compared to the mainland. This was mainly due to the significantly lower prevalence of small mammal-associated B. afzelii. Deer abundance was not related to pathogen prevalence, suggesting that the structure and dynamics of the reservoir host community underpins the observed prevalence patterns, with the higher mobility of bird hosts compared to small mammal hosts leading to a relative predominance of the bird-associated genospecies B. garinii and generalist genospecies B. burgdorferi (s.s.) on islands. In contrast, the lower prevalence of B. afzelii on islands may be due to small mammal populations there exhibiting lower densities, less immigration and stronger population fluctuations. This study suggests that landscape fragmentation can influence the prevalence of a zoonotic pathogen, dependent on the biology of the reservoir host

Multilocus Sequence Typing of <i>Borrelia burgdorferi</i> Suggests Existence of Lineages with Differential Pathogenic Properties in Humans

<div><p>The clinical manifestations of Lyme disease, caused by <i>Borrelia burgdorferi,</i> vary considerably in different patients, possibly due to infection by strains with varying pathogenicity. Both rRNA intergenic spacer and <i>ospC</i> typing methods have proven to be useful tools for categorizing <i>B. burgdorferi</i> strains that vary in their tendency to disseminate in humans. Neither method, however, is suitable for inferring intraspecific relationships among strains that are important for understanding the evolution of pathogenicity and the geographic spread of disease. In this study, multilocus sequence typing (MLST) was employed to investigate the population structure of <i>B. burgdorferi</i> recovered from human Lyme disease patients. A total of 146 clinical isolates from patients in New York and Wisconsin were divided into 53 sequence types (STs). A goeBURST analysis, that also included previously published STs from the northeastern and upper Midwestern US and adjoining areas of Canada, identified 11 major and 3 minor clonal complexes, as well as 14 singletons. The data revealed that patients from New York and Wisconsin were infected with two distinct, but genetically and phylogenetically closely related, populations of <i>B. burgdorferi</i>. Importantly, the data suggest the existence of <i>B. burgdorferi</i> lineages with differential capabilities for dissemination in humans. Interestingly, the data also indicate that MLST is better able to predict the outcome of localized or disseminated infection than is <i>ospC</i> typing.</p></div

Distribution of <i>B. burgdorferi</i> STs between Lyme disease patients with disseminated and localized infection.

a<p>Only STs that are represented by ≥2 isolates with available clinical data are shown.</p><p>STs, sequence types.</p

Distribution of <i>B. burgdorferi</i> isolates from Lyme disease patients with localized and disseminated infection between clonal complexes and singletons.

<p>Distribution of <i>B. burgdorferi</i> isolates from Lyme disease patients with localized and disseminated infection between clonal complexes and singletons.</p

Geographical distribution of <i>B. burgdorferi ospC</i> major groups found in skin of Lyme disease patients from New York and Wisconsin.

a<p>New York data (n = 290) based on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073066#pone.0073066-Wormser4" target="_blank">[19]</a>. One additional isolate (E3) was added from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073066#pone.0073066-Hanincova1" target="_blank">[13]</a>.</p>b<p><i>ospC</i> major group designation according to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073066#pone.0073066-Barbour1" target="_blank">[8]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073066#pone.0073066-Wang1" target="_blank">[12]</a>. <i>ospC</i> major groups X and Y were not published at the time this article was written but are available in GenBank under accession numbers HM047876 and HM047875 respectively.</p

Unrooted ML tree of <i>B. burgdorferi</i> based on concatenated sequences of eight MLST housekeeping genes.

<p>The tree was created using data from this study and the previously published data sets downloaded from <a href="http://borrelia.mlst.net/" target="_blank">http://borrelia.mlst.net/</a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073066#pone.0073066-Margos1" target="_blank">[7]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073066#pone.0073066-Ogden1" target="_blank">[41]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073066#pone.0073066-Hoen1" target="_blank">[43]</a>. A total of 420 <i>B. burgdorferi</i> samples (88 STs) found in humans and ticks from the northeastern United States and Canada were used. The aLRT statistical values and nonparametric bootstrap values for highly supported nodes in both maximum parsimony (with >70% support) and maximum likelihood (with aLRT >0.9 support) are indicated above and below the branches, respectively. STs newly identified in this study are in bold. The grouping of STs into major clonal complexes (CCs) is indicated by right brackets. The STs found only in humans are shown in blue, those found only in ticks are shown in red and those found in both humans and ticks are shown in green. The type of infection is indicated next to the ST using solid square (ST found in patients with localized infection), solid triangle (ST found in patients with disseminated infection) and solid diamond (ST found in both patients with localized and patients with disseminated infection). Geographical origin of STs found in humans and identified in this study is indicated in brackets next to the STs (NY – New York; WI – Wisconsin).</p