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Infection and Immunity, September 2007, p. 4621-4628, Vol. 75, No. 9
0019-9567/07/$08.00+0 doi:10.1128/IAI.00263-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Department of Dermatology, Medical University of Graz, Graz, Austria,1 Center for Immunology and Inflammatory Diseases, Division of Rheumatology, Allergy and Immunology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts2
Received 16 February 2007/ Returned for modification 3 April 2007/ Accepted 20 June 2007
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In Europe, LB is caused by three pathogenic species of Borrelia burgdorferi sensu lato: Borrelia afzelii, Borrelia garinii, and Borrelia burgdorferi sensu stricto (hereafter referred to as B. burgdorferi) (5). However, in Europe (and specifically in Austria), B. afzelii is the most common cause of each of these dermatologic manifestations of the infection (2, 26, 30, 39, 40). In the United States, Lyme disease is caused only by B. burgdorferi. There, EM lesions are a feature of the illness, but not BL or ACA lesions (38).
In EM lesions, perivascular infiltrates of macrophages and CD8+ and CD4+ T cells are found along with smaller numbers of B cells and plasma cells (25, 42). ACA lesions are infiltrated throughout the dermis with these cells, including abundant plasma cells (7, 42). In contrast, BL lesions have dense infiltrates of B cells with proportionally fewer T cells, and the B cells often form follicular structures, sometimes with the appearance of germinal centers (11, 42).
Two previous studies have analyzed cytokine responses in human EM lesions. In our initial study of Austrian patients, the major cytokines expressed by infiltrating cells in the lesions were the proinflammatory cytokine gamma interferon (IFN-
) and the anti-inflammatory cytokine interleukin-10 (IL-10), as determined by in situ hybridization with riboprobes (25). In addition, in patients with extracutaneous signs and symptoms, tumor necrosis factor alpha (TNF-
), IL-1ß, and IL-6 were often expressed. In a study of EM lesions in U.S. patients (33), in which flow cytometry was used to characterize cytokines in fluids aspirated from suction blisters raised over EM lesions, the fluids, which were enriched for T cells, macrophages, and dendritic cells, contained predominantly IL-6 and IFN-
. Thus, in both studies, proinflammatory cytokines, particularly IFN-
, were predominant.
Chemokines (chemoattractant cytokines) play a crucial role in the homing of inflammatory cells to infected tissues. In a seminal study with B. burgdorferi-infected mice, which develop arthritis but not skin or neurologic abnormalities, CXCL1, a neutrophil chemokine, and CCL2, a macrophage chemokine, were highly expressed in infected joints (9). In tissue culture systems of monocytes, endothelial cells, keratinocytes, fibroblasts, or mast cells, B. burgdorferi sensu lato potently induced the neutrophil chemoattractants CXCL1 and CXCL8; the macrophage chemoattractants CCL2, CCL3, and CCL5; or the T-cell chemoattractants CXCL9 and CXCL10 (10, 15, 16, 36). In human patients or nonhuman primates with neuroborreliosis, elevated levels of the neutrophil chemokine CXCL8; the macrophage chemokines CCL3, CCL4, and CCL5; the T-cell chemokines CXCL10, CXCL11, and CXCL12; or the B-cell chemokine CXCL13, were found in serum or cerebrospinal fluid (18, 22, 29, 32) or in nervous system tissues (27).
Chemokine and cytokine signatures have not yet been defined and compared in lesional skin of the three skin disorders of LB in Europe. In the current study, we determined the mRNA expression of 12 chemokines, 8 cytokines, and 5 leukocyte markers in the lesional skin of 100 patients with EM, BL, or ACA, using high-throughput quantitative reverse transcription-PCR (QRT-PCR) techniques. We found a predominance of IFN-
-inducible T-cell-active chemokines CXCL9 and CXCL10 in EM and ACA and of the B-cell-active chemokine CXCL13, in BL.
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Patients were excluded if they had a history of previous LB; if they had a coincident condition, disease, or medication that might alter immune function; or if they had already received antibiotic therapy for the infection. Finally, they were required to be seronegative for coinfection with Anaplasma phagocytophilum by indirect immunofluorescence assay (MRL Diagnostics, Cypress, CA). Of the 128 patients with EM, 38 were excluded because of a negative serologic result for B. burgdorferi sensu lato, 11 because of inconclusive histopathology, and 15 because of a positive serologic test for A. phagocytophilum. One of the 12 BL patients and 9 of the 34 ACA patients were excluded because of inconclusive histologic findings. Patient recruitment was continued until samples were obtained from 100 evaluable patients.
Skin biopsy samples. In all patients, two 4-mm punch skin biopsy samples were obtained, one for histologic examination and one for chemokine, cytokine, and leukocyte marker mRNA analyses and B. burgdorferi sensu lato species determinations. Biopsies were taken from the active borders of EM lesions or from the areas of BL or ACA lesions with the most prominent signs of inflammation. The sample for histology was placed in 4% formaldehyde, embedded in paraffin, and stained with hematoxylin and eosin. The sample for mRNA and B. burgdorferi sensu lato determinations was placed immediately in a 2-ml tube containing RNAlater (Ambion, Austin, TX), an RNA stabilization/protection reagent. The tubes were refrigerated overnight at 4°C and then stored at –70°C until ready for use.
A control group of 25 healthy subjects was developed, from whom normal skin samples (4 to 6 mm) were obtained at the edges of elliptical excision specimens of atypical melanocytic nevi. These samples were also placed immediately in a 2-ml tube containing RNAlater.
RNA isolation and cDNA synthesis. Each skin sample was ground mechanically in guanidine isothiocyanate-containing lysis buffer (QIAGEN, Valencia, CA), which immediately inactivates RNases, and total RNA was extracted using the RNeasy kit according to the manufacturer's protocol (QIAGEN). After DNase I treatment, total RNA from each sample (1 µg) was used as the template for the RT reaction. cDNA (100 µl) was synthesized using oligo(dT)15, random hexamers, and Multiscribe reverse transcriptase (Applied Biosystems, Foster City, CA) in a Peltier PTC 200 thermal cycler (MJ Research, Ramsey, MN). All samples were reverse transcribed under the same conditions (25°C for 10 min and 48°C for 30 min) and from the same RT master mix to minimize differences in RT efficiency. As a negative control, each experiment included a sample without reverse transcriptase.
Identification of the B. burgdorferi sensu lato species. The B. burgdorferi sensu lato species was determined from the cDNA by PCR amplification of B. burgdorferi sensu lato ospA transcripts using published primer sets (13, 31). This reaction amplifies a sequence of approximately 300 bp for each of the three pathogenic B. burgdorferi sensu lato species. Each ospA PCR product was subjected to restriction digestion with the BfaI or MseI enzyme (New England Biolabs, Beverly, MA), which yields specific restriction fragment length polymorphisms for each species. For these analyses, the PCR product (10 µl) was mixed with 4 µl of enzyme-specific buffer and 5 units of enzyme in a 40-µl total volume. For MseI digestions, 4 µl of 0.1-mg/ml bovine serum albumin was included in the mixture as a carrier molecule. Digests were incubated overnight at 37°C and visualized on 2% agarose gels (Invitrogen, Carlsbad, CA), with ethidium bromide staining. After digestion with BfaI, B. afzelii was predicted to have a single band of 293 bp; B. burgdorferi, a single band of 245 bp; and B. garinii, two bands of 147 and 146 bp. After digestion with MseI, B. afzelii was predicted to have two bands of 221 and 66 bp, and both B. burgdorferi and B. garinii were predicted to have two bands of 148 and 74 bp.
Quantitative PCR for chemokines, cytokines, and leukocyte markers. Quantitation of chemokine, cytokine, and leukocyte marker mRNA expression was performed as previously described (23), using the MX4000 multiplex QRT-PCR system (Stratagene, La Jolla, CA). The primers for each reaction (Table 1) were synthesized commercially (Invitrogen). The 25-µl QRT-PCR mixture contained 2 µl of cDNA, 12.5 µl of 2x SYBR green master mix (Stratagene), and 250 nmol (1.625 µl) of sense and antisense primer. The reaction conditions were 50°C for 2 min, 95°C for 10 min, and then 40 cycles of 95°C for 15 s and 60°C for 1 min. Emitted fluorescence for each reaction was measured during the annealing/extension phase, and amplification plots were analyzed using the MX4000 software version 3.0 (Stratagene). The DNA encoding sequence for each gene analyzed by QRT-PCR was cloned into a plasmid vector. A series of standards were prepared by performing serial 10-fold dilutions of full-length coding DNAs from 20 million copies to two copies per QRT-PCR. The QRT-PCR primer efficiencies were similar for all target and housekeeping genes. Analysis was performed on the data output from the MX4000 software using Excel XP (Microsoft, Redmond, WA). The threshold cycle (the cycle at which the amount of the amplified gene reaches threshold fluorescence) was determined using the adaptive baseline algorithm in the MX4000 analysis software. Quantity values (i.e., copies) for gene expression were generated by comparison of the fluorescence generated by each sample with standard curves of known quantities. To control for variation in the size of the biopsies, the number of copies was then divided by the number of copies of a housekeeping gene, that for glyceraldehyde-3-phosphate dehydrogenase (GAPDH). As a negative control, reactions without cDNA were included on each plate.
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TABLE 1. Oligonucleotide primers for the leukocyte antigens, chemokines, and cytokines analyzed
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Statistics.
Differences in mRNA expression of chemokines, cytokines, and leukocyte markers among patients with EM, BL, or ACA or normal control subjects were determined by the Kruskal-Wallis test. All P values were two tailed. P values of
0.05 were considered statistically significant.
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Analysis of B. burgdorferi sensu lato DNA in the skin biopsy samples showed that 77% or more of the patients with each of the skin disorders were infected with B. afzelii, about 10% had B. burgdorferi, and the remaining patients had B. garinii or mixed infection (Table 2). By definition, all patients were seropositive for B. burgdorferi sensu lato infection. Most patients with EM were treated with oral doxycycline for 2 or 3 weeks, and those with BL or ACA were usually given 4 weeks of this medication. A small number of patients received other, comparable regimens. All patients responded to therapy, but in several patients with ACA, skin atrophy persisted or neuropathy resolved slowly.
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TABLE 2. Borrelia burgdorferi sensu lato species in lesional skin from patients with skin disorders of Lyme borreliosis in Austria
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FIG. 1. mRNA expression of neutrophil, dendritic cell, and macrophage chemoattractants and their cell markers in 64 EM lesions, 11 BL lesions, 25 ACA lesions, and 25 normal skin samples relative to the GAPDH gene. Data are shown in box plots in which the boxes represent the 25th and 75th percentiles, the lines within the boxes represent the median values, and the lines outside the boxes represent the 5th and 95th percentiles. A difference between normal and lesional skin (*), between EM and BL or EM and ACA lesions (**), or between BL and ACA lesions ( ) at the 0.05 level is indicated above the bars. Low mRNA levels of neutrophil and dendritic cell chemoattractants and moderate mRNA levels of macrophage chemoattractants, primarily CCL2, were found.
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-inducible chemokines CXCL9 and CXCL10, which are strong chemoattractants for effector CD8+ and Th1-type CD4+ T cells, were found in lesional skin in EM, BL, and particularly ACA (Fig. 2). Consistent with these findings, high mRNA levels were identified for both the CD8 and CD4 T-cell markers; the CD8/CD4 ratios were 1.3 in EM, 1.9 in BL, and 2.0 in ACA. In contrast, mRNAs for the Th2 cell chemokines CCL1 and CCL22 were virtually absent. Whereas EM and ACA had only low mRNA levels of the B-cell chemoattractant CXCL13, BL had significantly higher levels of this chemokine and the CD19 B-cell marker and proportionately lower levels of CXCL9 and CXCL10. In each of the three skin disorders of the infection, mRNA levels for Th1 and B-cell chemoattractants were greater in lesional skin than in normal skin.
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FIG. 2. mRNA expression of T- and B-cell chemoattractants and their cell markers in 64 EM lesions, 11 BL lesions, 25 ACA lesions, and 25 normal skin samples relative to the GAPDH gene. Data are shown in box plots in which the boxes represent the 25th and 75th percentiles, the lines within the boxes represent the median values, and the lines outside the boxes represent the 5th and 95th percentiles. A difference between normal and lesional skin (*), between EM and BL or EM and ACA lesions (**), or between BL and ACA lesions ( ) at the 0.05 level is indicated above the bars. High levels of the CD8+ and Th1-type CD4+ T-cell chemoattractants CXCL9 and CXCL10 were found in EM and ACA lesions, whereas BL lesions had high levels of the B-cell chemoattractant CXCL13 and proportionally lower levels of CXCL9 and CXCL10.
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FIG. 3. Immunohistochemistry of skin biopsy samples from a representative patient with EM (A to D) or BL (E to H). At low power (A), infiltrating CD3+ T cells are seen around sweat glands in the reticular dermis of the EM lesion, and at higher power (B), they are seen in perivascular locations in the papillary dermis. In panel C, with the microscope centered on the same location, staining for CXCL9 is visualized in the area of the T-cell infiltrate, and in panel D, the same area is stained without primary antibody. In the biopsy of the central portion of a BL lesion, intense staining of CD20+ B-cell clusters is seen at low power, particularly within the mid- and deeper dermis (E), and at higher power (F), a single aggregate of B cells is seen. In panel G, with the microscope centered on the same location, staining for CXCL13 is visualized in the area of the B-cell aggregate, and in panel H, the same area is stained without primary antibody. In each section, the specific stain is diaminobenzidine (brown) and the nonspecific background stain is hematoxylin (purple). Magnifications, x100 (A and E) and x400 (B to D and F to H).
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and the Th1 cytokine IFN-
was greater than that for the anti-inflammatory cytokines IL-10 and transforming growth factor ß (TGF-ß) and the Th2 cytokines IL-4 and IL-5, but mRNA levels of the proinflammatory cytokine IL-12p40 were low (Fig. 4). Cytokine mRNA expression was usually lowest and similar to that in normal skin in EM lesions, intermediate in BL, and highest in ACA, which had significantly greater levels of IFN-
, TNF-
, IL-10, and IL-5 than normal skin or EM lesions.
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FIG. 4. mRNA expression of proinflammatory and anti-inflammatory cytokines in 64 EM lesions, 11 BL lesions, 25 ACA lesions, and 25 normal skin samples relative to the GAPDH gene. Data are shown in box plots in which the boxes represent the 25th and 75th percentiles, the lines within the boxes represent the median values, and the lines outside the boxes represent the 5th and 95th percentiles. A difference between normal and lesional skin (*) or between EM and ACA lesions (**) at the 0.05 level is indicated above the bars. mRNA expression of the proinflammatory cytokines IFN- , IL-1ß, and TNF- was greater than of the anti-inflammatory cytokines IL-10, IL-4, IL-5, and TGF-ß.
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6 months) had significantly higher mRNA levels of the potentially profibrotic cytokine TGF-ß than the 15 patients with early inflammatory lesions (median values, 0.09 versus 0.06 copies/GAPDH; P = 0.05). However, there were no other significant differences between these two groups. |
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-inducible CD8+ and Th1-type CD4+ T-cell chemoattractants CXCL9 and CXCL10, intermediate levels of the macrophage chemokine CCL2, and low levels of the B-cell chemokine CXCL13. In contrast, BL lesions had high mRNA levels of CXCL13 and proportionally lower levels of the T-cell chemokines. This chemokine pattern was consistent with leukocyte marker mRNA in lesional skin. Moreover, using immunohistologic techniques, T cells and CXCL9 were visualized directly in EM and ACA, and B cells and CXCL13 were seen in BL. The major purpose of these T- and B-cell responses in LB seems to be to promote antibody production, since opsonization of spirochetes with antibodies results in more effective spirochetal killing (24). Among the current patients, 77% or more with each skin disorder had B. afzelii infection, about 10% had B. burgdorferi, and the remaining patients had B. garinii or mixed infection. Similar distributions of these three Borrelia species (72% B. afzelii, 15% B. burgdorferi, 6% B. garinii, 5% mixed infection, and 2% Borrelia valaisiana) were found in a survey of Ixodes ricinus ticks from southeastern Austria, where the current patients resided (R. R. Müllegger and M. Glatz, unpublished data). Although B. afzelii is the most common cause of ACA, each of these Borrelia species has now been recovered from ACA lesions (21, 30). Thus, in southeastern Austria, the three skin disorders of LB are primarily but not exclusively associated with B. afzelii infection.
In EM lesions, cytokine protein levels or cytokine mRNA expression have been measured by flow cytometry (33), in situ hybridization (25), and, in the current analysis, by QRT-PCR techniques. QRT-PCR does not distinguish mRNA of infiltrating cells from that of constituent cells, and mRNA expression does not prove that a biologically active protein is produced. However, as shown here for CXCL9 and CXCL13 and as documented in the literature (8), mRNA expression correlates well with actual cytokine and chemokine responses at sites of inflammation. Thus, QRT-PCR has become the method of choice for the quantification and comparison of immune mediators in tissues (17, 41). In the current study, mRNAs for a large number of chemokines, cytokines, and leukocyte markers were measured in skin biopsy samples from 100 patients and 25 control subjects at one time, thereby limiting experimental variables and facilitating the comparison of immune reactants within and among the groups.
Consistent with previous cytokine analyses (25, 33), the current chemokine data provide unequivocal evidence for a dominant Th1 response in lesional skin of each of the three skin disorders of LB. In addition, CD8+ T cells, which presumably serve as a source of IFN-
, are often more abundant than CD4+ T-helper cells. The major difference in this study compared with past experience concerns ACA. This chronic skin lesion was originally thought to occur predominately in older women (3). However, with more awareness of the disease and better diagnostic testing, it is becoming clear that younger adults, including both men and women, may also develop this lesion (26). In the current study, the age ranges of EM and ACA patients were similar, and the sex ratios in both groups were only 2 to 1 in favor of women. In our previous analysis, ACA lesions had a more restricted cytokine profile than EM lesions, with little or no expression of IFN-
, as determined by in situ hybridization (25). We hypothesized that this cytokine response may be less effective in spirochetal killing, thereby explaining in part the chronicity of the lesion. However, in the current analysis, similar but higher mRNA expression of chemokines and cytokines, including IFN-
, was found in ACA compared with EM lesions, and these values did not differ by age or sex. In another study, high levels of IFN-
were found in the blood of ACA patients (43). Nevertheless, the microenvironment of ACA is primarily acral surfaces of the extremities, where the immune response may be modulated so that complete spirochetal killing is inhibited.
Although BL lesions had inflammatory mediators similar to those of EM and ACA lesions, mRNA expression of the B-cell chemoattractant CXCL13 and the B-cell marker CD19 were dominant in BL. Presumably, this finding relates to the almost exclusive location of such lesions on the ear or the nipple or areola of the breast (4, 26). Inflammatory responses may depend on tissue microenvironments (e.g., stromal cells) and their interactions with infiltrating immune cells (14). Lymphotoxin-
or -ß induces the secretion of CXCL13 (19, 28), which is responsible for the formation of lymphoid aggregates with germinal center-like structures in ectopic locations (ectopic lymphoid organogenesis) (6, 14). As shown again here, this morphological characteristic is found in most BL lesions (11). In addition, B-cell aggregates occur in some synovial lesions in patients with Lyme arthritis (1), and the finding of CXCL13 in cerebrospinal fluid in patients with neuroborreliosis suggests that lymphoid aggregates with germinal centers might be found in inflamed meninges (32).
In conclusion, the three skin disorders of European LB had similar chemokine and cytokine signatures, but they differed in the amounts of these inflammatory mediators. Chemoattractants for cells of the innate immune response, neutrophils, dendritic cells, and macrophages, were present in all three skin disorders. However, it was chemoattractants for cells of the adaptive immune response that differed most. EM and ACA lesions had high mRNA expression of the T-cell-active chemokines CXCL9 and CXCL10, whereas BL lesions had especially high levels of CXCL13. In southeastern Austria, where B. afzelii is the primary cause of these infections, the microenvironment of the skin (and perhaps as-yet-unidentified host immune factors) seems to influence these differences. Thus, depending on the site of the infection, B. afzelii or occasionally other B. burgdorferi sensu lato species may cause an acute, self-limited EM lesion particularly in or near intertriginous sites, a subacute BL lesion on the nipple or ear, or a chronic persistent ACA lesion primarily on extensor surfaces of the extremities.
This work was supported by the National Institutes of Health (grant CA-69212); the Centers for Disease Control and Prevention (grant C1000157); the English, Bonter, Mitchell Foundation; the Eshe Fund; and the Lyme/Arthritis Research Fund at Massachusetts General Hospital. J.J.S. and K.L.J. received scholarships from the Walter J. and Lille A. Berbecker Foundation for the study of Lyme disease and were also supported by rheumatology training grant AR T32-07258 from the National Institutes of Health.
The authors state no conflict of interest.
Published ahead of print on 2 July 2007. ![]()
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