Severe Lyme arthritis: Gagging on GAGs

Janis Weis' group has been mapping genetic variants that make laboratory mice prone to severe Lyme arthritis.  One of these variants is described in a paper that appeared in The Journal of Clinical Investigation earlier this year.  The affected gene encodes the enzyme β-glucuronidase, which carries out a critical function in the lysosome. β-glucuronidase cooperates with other degradative enzymes in the lysosome to break down glycosaminoglycans (GAGs) into their individual sugar units, which are then removed from the lysosome and reused by the cells.  GAGs are long chains of specific disaccharides located on the cell surface and within the extracellular matrix.  GAGs are covalently (in proteoglycans) or noncovalently attached to proteins.  GAGs are always being degraded and resynthesized by cells. Blocking any of the enzymes involved in GAG breakdown causes accumulation of GAG fragments, which are potentially detrimental to health.  In humans, certain mutations in the β-glucuronidase gene lead to a rare condition called Sly syndrome.

Large amounts of GAGs are found in the joints, where they serve an important mechanical function.  GAGs carry a high density of negative charge due to the presence of acidic sugars such as glucuronic acid, the target of β-glucuronidase, and the sulfate groups attached to most types of GAGs.  The negative charge attracts cations, which in turn attract large numbers of water molecules.  The water within GAGs acts as a cushion that allows the joints to withstand large compressive forces.

The key to the study was having strains of mice that differed in their susceptibility to Lyme arthritis. The C3H mouse strain develops severe joint inflammation during B. burgdorferi infection. On the other hand, the B6 strain develops mild joint inflammation when infected. Weis' group had earlier narrowed the locations of the genetic variations accounting for the different susceptibilities to several distinct segments within the mouse genome.  They used the traditional techniques of mouse genetics, which involved numerous matings involving the C3H and B6 strains and their progeny (see this review for details).  The authors focused on one of the segments, and with help from mouse genome sequence data that became available, they found a nucleotide difference within the Gusb (β-glucuronidase) gene that changed a single amino acid in the enzyme.

The investigators found that β-glucuronidase activity was mildly reduced in the infected C3H strain relative to the B6 strain.  Staining tissue sections of infected mice with Alcian blue, a dye attracted to polyanions, revealed accumulation of GAGs in the joint tissues of infected C3H mice but not infected B6 mice, lending further support to the lesion in Gusb being responsible for severe inflammation.  When a functional copy of the β-glucuronidase gene was stitched into the genome of C3H mice, B. burgdorferi infection no longer caused joint inflammation.

Does the same process occur in humans with Lyme arthritis?  One hint that β-glucuronidase influences the course of Lyme arthritis is the finding from other labs that found that the concentration of the enzyme in joint fluid is higher in patients with Lyme arthritis than it is in healthy uninfected individuals, although how the high enzyme levels are mechanistically linked to arthritis remains unexplained.

So how does β-glucuronidase deficiency lead to severe Lyme arthritis?  One possibility raised by the authors is that GAG fragments worsen tissue inflammation by stimulating Toll-like receptors, as shown in other studies (see this paper for an example).

The findings may also tell us something about rheumatoid arthritis (RA).  The B6 strain ends up with a form of RA following injection with certain autoantibodies.  One of Weis' mouse crosses generated a B6 strain with its Gusb gene and flanking regions swapped for the same region of the C3H strain.  This strain developed severe arthritis when injected with the same autoantibodies and when infected with B. burgdorferi.  Therefore, the pathologic processes leading to Lyme arthritis and RA share common steps, at least in laboratory mice.  In humans, RA patients, like those with Lyme arthritis, have high levels of β-glucuronidase levels in their joint fluid.

The search for host factors affecting the development of Lyme arthritis goes on.  Weis' group continue to identify genetic variants responsible for severe Lyme arthritis.


References

Bramwell KK, Ma Y, Weis JH, Chen X, Zachary JF, Teuscher C, & Weis JJ (2014). Lysosomal β-glucuronidase regulates Lyme and rheumatoid arthritis severity. The Journal of Clinical Investigation, 124 (1), 311-320 PMID: 24334460

Bramwell KK, Teuscher C, & Weis JJ (2014). Forward genetic approaches for elucidation of novel regulators of Lyme arthritis severity. Frontiers in Cellular and Infection Microbiology, 4 PMID: 24926442

Pancewicz S, Popko J, Rutkowski R, Knaś M, Grygorczuk S, Guszczyn T, Bruczko M, Szajda S, Zajkowska J, Kondrusik M, Sierakowski S, & Zwierz K (2009). Activity of lysosomal exoglycosidases in serum and synovial fluid in patients with chronic Lyme and rheumatoid arthritis. Scandinavian Journal of Infectious Diseases, 41 (8), 584-589 PMID: 19513935

Jiang D, Liang J, Fan J, Yu S, Chen S, Luo Y, Prestwich GD, Mascarenhas MM, Garg HG, Quinn DA, Homer RJ, Goldstein DR, Bucala R, Lee PJ, Medzhitov R, & Noble PW (2005). Regulation of lung injury and repair by Toll-like receptors and hyaluronan. Nature Medicine, 11 (11), 1173-1179 PMID: 16244651

An autoantigen targeted during Lyme arthritis

Infection by the spirochete Borrelia burgdorferi, if left untreated, can lead to a form of Lyme disease called Lyme arthritis.  About 10% of Lyme arthritis patients end up with a chronic form that doesn't go away with antibiotic treatment.  Allen Steere's group has long suspected that the antibiotic-refractory form of Lyme arthritis involves an autoimmune process.  This notion seems reasonable since those with antibiotic-refractory Lyme arthritis tend to have certain forms of the HLA-DR gene that are also common among those afflicted with the autoimmune disease rheumatoid arthritis.

Several groups have been searching for autoantigens (self antigens) that could drive the joint inflammation seen in Lyme arthritis patients.  Several candidate protein autoantigens were identified based on their short sequence similarities (molecular mimicry) to a T-cell or antibody epitopes in the B. burgdorferi OspA protein, which is targeted by the immune system in many Lyme arthritis patients, especially those with the antibiotic-refractory form.  However, further studies demonstrated that none of these autoantigens were likely to stimulate a sufficiently robust T-cell or antibody response that could account for the prolonged joint swelling experienced by patients with antibiotic-refractory Lyme disease (see this excellent review article for the complete story).  Therefore, an additional approach is needed to identify additional autoantigen candidates, an approach that does not assume that molecular mimicry underlies antibiotic-refractory Lyme arthritis.

An unbiased approach for finding autoantigens is to gather all of the different self-peptides being displayed by the HLA-DR molecules in the synovial tissue of the swollen joint and then figure out which of these peptides are capable of stimulating T cells.  At one time this approach wasn't possible since the individual peptides presented by HLA-DR molecules are found in such tiny amounts in human tissues, but the sensitivity of today's liquid chromatography/tandem mass spectrometry systems have improved to the point where many of the peptides can now be sorted and sequenced.

Steere's new study, which appeared in January's print issue of Arthritis and Rheumatism, was conducted in collaboration with Catherine Costello's group in Boston University.  The study was a follow-up to an earlier one published two years ago.  The authors extracted the inflamed synovial tissue from the swollen knee of a 12 year old boy suffering from antibiotic-refractory Lyme arthritis (see picture below).  He had gone through three months of antibiotic therapy a year prior to the procedure.  The tissue was culture and PCR negative.  When the patient's HLA-DR genes were examined, he turned out to have a copy of the DRB1*0101 allele, one of the HLA-DRB gene variants that places individuals at a higher risk for antibiotic-refractory Lyme arthritis.

Figure 1A from Drouin et al., 2013

The boy's synovial tissue was ground up, and HLA-DR-specific antibodies were used to capture the HLA-DR molecules with their bound peptides.  The peptides were then analyzed by liquid chromatography/tandem mass spectrometry.  The authors identified 120 different self-peptides from this analysis.  When each peptide was chemically synthesized and mixed with the boy's blood mononuclear cells, one peptide turned out to stimulate proliferation of his T cells.  This peptide came from a human protein called endothelial cell growth factor, or ECGF.

What's the function of ECGF?  The protein stimulates angiogenesis, the sprouting of new blood vessels from pre-existing ones.  Angiogenesis is a general feature of inflammatory arthritis, including Lyme arthritis and rheumatoid arthritis.

The authors went on to examine the T- and B-cell responses to ECGF in other Lyme arthritis patients.  The T-cell response was determined by measuring the amount of interferon-γ secreted by the patients' blood mononuclear cells upon exposure to ECGF in vitro.  In antibiotic-refractory patients, the T-cell response was observed in 38% (14/37) subjects against 30% (8/27) among Lyme arthritis patients who responded to antibiotics. The difference between the two groups was not statistically significant.  The B-cell (antibody) response was examined by ELISA in a larger group of patients.  17% (19/109) of antibiotic-refractory patients and 8% (6/77) of antibiotic-responsive patients had an IgG antibody response against ECGF that was higher than among healthy controls, yet the difference between the antibiotic-refractory and -responsive groups again was not statistically significant (P = 0.09).  So a link between an autoimmune response to ECGF and antibiotic-refractory arthritis was not clear-cut.  However, in support of a link, the authors mentioned that almost all of the Lyme arthritis patients with a T-cell response to ECGF (20/21, 98%) had one of the HLA-DR alleles known to be a risk factor for antibiotic-refractory arthritis.

The authors also looked at the levels of ECGF in the swollen joints of Lyme arthritis patients.  Those with antibiotic-refractory Lyme arthritis had much higher levels of ECGF in their joint fluid (mean 448 ng/ml, 37 subjects) than those whose arthritis responded to antibiotic treatment (mean 154 ng/ml, 19 subjects, P < 0.0001)

Further evidence for a link between an immune response to ECGF and chronic Lyme arthritis came from a group of untreated Lyme disease patients who were followed in the late 1970s, before the cause of Lyme disease was known.  Sera from sequential bleeds were still available from many of these patients.  If an autoimmune process involving ECGF was responsible for the disease, then the immune response to the autoantigen should have appeared before the disease symptoms.  This turned out to be the case.  Six of the seven Lyme arthritis patients who had antibodies against ECGF developed the antibody response before their joints swelled up.  The duration of the arthritis attack was longer in Lyme arthritis patients with an immune response to ECGF, lasting a median of 67 weeks in the seven patients with an ECGF antibody response and only 17 weeks in the 20 Lyme arthritis lacking the response (P = 0.004).

Steere's paper proposes that the immune response to ECGF leads to a persisting, autoimmune form of arthritis in those who have a high level of ECGF in their joint fluid.  In those patients, T cells that recognize ECGF would be activated more easily because of the high levels of ECGF available for phagocytes to engulf, process, and display to the T cells.  These events would lead to a chronic form of arthritis that would persist even when the spirochetes were cleared from the joints by the immune system or antibiotics.  These patients also have a lot of ECGF in their synovial tissue.  Antibody against ECGF could bind to the tissue and trigger attack by complement, contributing to the tissue damage.

Molecular mimicry doesn't appear to be involved in triggering an immune response to ECGF.  The authors were unable to identify any B. burgdorferi proteins that could cross-react with ECGF.

The immune response to ECGF can't be the whole story since most patients with antibiotic-refractory Lyme arthritis don't generate a T-cell or antibody response to the protein.  An autoimmune process in these other patients may involve other self-antigens waiting to be discovered.  Other host and spirochete factors also influence the course of Lyme arthritis (see this post, which gives the spirochete's point of view).


References

Drouin, E.E., Seward, R.J., Strle, K., McHugh, G., Katchar, K., Londoño, D., Yao, C., Costello, C.E., & Steere, A.C. (2013). A novel human autoantigen, endothelial cell growth factor, is a target of T and B cell responses in patients with Lyme disease. Arthritis & Rheumatism, 65 (1), 186-196 DOI: 10.1002/art.37732

Seward, R.J., Drouin, E.E., Steere, A.C., & Costello, C.E. (2010). Peptides presented by HLA-DR molecules in synovia of patients with rheumatoid arthritis or antibiotic-refractory Lyme arthritis. Molecular & Cellular Proteomics, 10 (3) DOI: 10.1074/mcp.M110.002477

A helpful review

Steere, A.C., Drouin, E.E., & Glickstein, L.J. (2011). Relationship between immunity to Borrelia burgdorferi Outer-surface protein A (OspA) and Lyme arthritis. Clinical Infectious Diseases, 52 (Supplement 3) DOI: 10.1093/cid/ciq117

Related post

• The genetics of both host and pathogen matter in antibiotic-refractory Lyme arthritis

Inflammatory spirochete debris left behind following antibiotic treatment for Lyme disease

According to the CDC, 10-20% of Lyme disease patients who have completed antibiotic therapy continue to suffer from symptoms such as joint, muscle, and neurological pain.  The following hypotheses are often presented as possible reasons for the lingering symptoms:  autoimmunity triggered by the infection, tissue damage inflicted by the spirochetes, and (depending on whom you ask) failure of antibiotics to kill all the spirochetes.  A new paper from Linda Bockenstedt's group at Yale proposes that antibiotic treatment of disseminated Borrelia burgdorferi infection leaves behind inflammatory pieces of dead spirochetes that are responsible for the persisting symptoms.

Bockenstedt's group used the mouse model of Lyme disease for the study.  To ensure that the tissues harbored enough B. burgdorferi spirochetes to be visible by intravital microscopy, the mice were genetically deficient in the intracellular signaling protein MyD88.  MyD88 links the recognition of microbial parts by most Toll-like receptors to activation of certain nuclear genes whose products are involved in the inflammatory process.  Mice lacking MyD88 are unable to control the proliferation of a number of bacterial pathogens, including B. burgdorferi.  The load of B. burgdorferi in tissues is about 100-fold higher in MyD88-deficient mice than in mice with a complete immune system.

The spirochetes were genetically altered to express green fluorescent protein (GFP).  The GFP⁺ B. burgdorferi was introduced into the MyD88-deficient mice by tick inoculation.  21 days later some of the mice were treated for one month with doxycycline, one of the antibiotics used to treat Lyme disease in humans.

The researchers next peered into the thin layer of skin covering the ear by intravital microscopy.  In the mice that were left untreated, they saw lots of spirochetes scurrying about in the dermis.

At the deepest depths of the dermis, they noticed immobile specks and patches of green material deposited near the cartilage.  They also saw the deposits in the doxycycline-treated mice.  The material was detected by immunofluorescence of ear sections with antibody against B. burgdorferi up to 10 weeks after antibiotic treatment was completed, indicating that the immune system was unable to clear the deposits.

There was no evidence that any spirochetes survived antibiotic treatment.  The researchers did not see any motile spirochetes in the skin by intravital microscopy.  In addition, tissues were culture negative, ticks that fed on the treated mice were culture negative (xenodiagnosis), and transplantation of skin from the treated mice failed to transmit the infection to recipient mice.  Based on these results, the authors concluded that the deposits were remnants of dead spirochetes.  As expected, untreated mice tested positive by these assays.

Since chronic infection can lead to Lyme arthritis, the investigators also examined the joints.  In another set of mice, the infection was allowed to proceed for four months.  The mice were then treated with the antibiotic ceftriaxone for 18 days.  When the researchers looked in the joints by intravital microscopy, they again saw the green material (see figure below).

Fig. 5 from Bockenstedt et al. showing the surface of the patella where it meets the tendon (enthesis).   Panel A, from mouse infected for 4 months, untreated.  Panel B, from mouse infected for 4 months and then treated with ceftriaxone for 18 days. Scale bar, 30 µm.

A critical issue to address is whether the amorphous material left behind following antibiotic treatment inflames the joints.   The authors could not answer this question directly because of the limitations of the mouse model. Histopathology is unlikely reveal joint inflammation, even in the untreated animals, because laboratory mice do not reliably exhibit joint inflammation so late (4-5 months) during B. burgdorferi infection.  Instead, the authors conducted a test tube experiment to see whether the deposits had inflammatory potential.  They ground up joint tissue from antibiotic-treated mice in buffer and applied the homogenate to cultured mouse macrophages.  The macrophages responded by producing TNF, a key cytokine that promotes inflammation.  The more tissue that was added, the more TNF that was produced by the macrophages.  In contrast, joint tissue from uninfected mice did not promote TNF production by the macrophages.  Therefore, the deposits had the potential to spark inflammation, even after motile spirochetes were eliminated by antibiotics.  The debris would continue to inflame the tissues even after antibiotics killed all live spirochetes, explaining why symptoms persist in ~10% of Lyme arthritis cases even after antibiotic treament.

The relevance of the deposits to Lyme disease in humans could be questioned because the MyD88-deficient mice did not have a complete immune system.  The authors addressed this concern in the Discussion by mentioning a recent study that described a TLR1 variant linked to severe inflammation and treatment failure in Lyme arthritis patients.  Although the gene encoding MyD88 has never been examined in Lyme disease patients, it is conceivable that the TLR1 variant or different forms of other immune genes lead to deposits of Borrelia antigen in the joint and other host tissues.

The authors also addressed the possibility that the deposits are really biofilms, which generally resist killing by antibiotics.  Biofilms are believed to be populated by persister cells, which are in a nondividing state that allows bacteria to tolerate antibiotics.  According to the authors, if the deposits had harbored persister cells, those cells should have resumed growing when conditions became favorable for growth again.  Because the skin and joints from the treated mice were culture negative and because the skin also tested negative by xenodiagnosis and transplantation assays, the authors quickly dismissed the biofilm hypothesis.

Stricly speaking, the authors are correct.  Persister cells should start multiplying again in fresh culture medium.  However, it's hard to dismiss the biofilm hypothesis completely given the known examples of culture-negative chronic infections associated with biofilms (see this review for one example).  Electron microscopy of the joint tissue could reveal whether these deposits are intact spirochetes or debris.

Regardless of their exact nature, deposits of antigen have never been detected within the joints of Lyme arthritis patients.  Allen Steere's group failed to find such deposits in pieces of synovial membrane removed from 26 patients with antibiotic-refractory Lyme arthritis.   The findings of Bockenstedt and colleagues, who detected the deposits in a location outside of the synovial membrane, suggest that Steere's group was looking in the wrong place.


Featured paper

Bockenstedt, L., Gonzalez, D., Haberman, A., & Belperron, A. (2012). Spirochete antigens persist near cartilage after murine Lyme borreliosis therapy Journal of Clinical Investigation, 122 (7), 2652-2660 DOI: 10.1172/JCI58813
 
Helpful references

Bolz DD, Sundsbak RS, Ma Y, Akira S, Kirschning CJ, Zachary JF, Weis JH, and Weis JJ (August 1, 2004).  MyD88 plays a unique role in host defense but not arthritis development in Lyme disease.  The Journal of Immunology 173(3):2003-2010.  Link

Strle K, Shin JJ, Glickstein LJ, and Steere AC (May 2012).  Association of a Toll-like Receptor 1 polymorphism with heightened Th1 inflammatory responses and antibiotic-refractory Lyme arthritis.  Arthritis and Rheumatism 64(5):1497-1507.  DOI: 10.1002/art.34383

Bakaletz LO (October 2007).  Bacterial biofilms in otitis media, evidence and relevance.  The Pediatric Infectious Disease Journal 26(10):S17-S19.  Link

Carlson D, Hernandez J, Bloom BJ, Coburn J, Aversa JM, Steere AC (December 1999).  Lack of Borrelia burgdorferi DNA in synovial samples from patients with antibiotic treatment-resistant Lyme arthritis.  Arthritis and Rheumatism 42(12):2705-2709.  DOI: 10.1002/1529-0131(199912)42:12<2705::aid-anr29>3.0.CO;2-H


Related posts

• Chronic Lyme disease in mice?
• Tigecycline fails to eradicate persisting Borrelia burgdorferi
• The magic of antibiotic tolerance

The genetics of both host and pathogen matter in antibiotic-refractory Lyme arthritis

The arthritic form of Lyme disease was first reported in the 1970s by Allen Steere, who described the condition in a group of children (and a few adults) residing in and around the town of Lyme, Connecticut. Lyme arthritis can strike when Borrelia burgdorferi introduced into the skin by an Ixodes tick burrows into deeper tissues and ends up in the joints, usually the knee. Swelling results from an inflammatory response to B. burgdorferi residing in the joint. Lyme arthritis is treated with antibiotics, which destroy the bacteria driving inflammation. Unfortunately, arthritic symptoms endure in ~10% of treated patients despite the complete or almost complete eradication of the infection, as determined by negative PCR tests for B. burgdorferi DNA in joint fluid. Such cases are called antibiotic-refractory Lyme arthritis, which can persist for months or sometimes years. In severe cases cartilage and bone erode. Although the pathogenesis of antibiotic-refractory Lyme arthritis could involve persistence of small numbers of B. burgdorferi (or their antigens) in the joints, investigators have been seeking an autoimmune mechanism to explain the prolonged attack on joint tissue by the immune system after the spirochetes have been cleared.

Many autoimmune diseases are linked to variants of HLA (immunity) genes such as those encoding the MHC class II complex. Antibiotic-refractory Lyme arthritis is associated with MHC class II variants that are able to bind to fragments of the B. burgdorferi protein OspA (outer surface protein A) encompassing amino acid residues 165 through 173. Antigen-presenting cells whose MHC class II molecules display OspA_165-173 peptides on their surface stimulate T cells that recognize the OspA peptide. How OspA_165-173-reactive T cells cause autoimmunity has been an area of intensive research, yet a clear answer has not emerged.

One potential pathway to autoimmunity is molecular mimicry, in which a cross-reactive host protein in the joint continues to stimulate OspA_165-173-specific T cells even after the eradication of B. burgdorferi by antibiotics. Although the simplicity of the molecular mimicry model is appealing, exhaustive efforts to find a cross-reactive autoantigen that stimulates OspA_165-173-specific T cells have failed. Moreover, levels of OspA_165-173-reactive T cells decline soon after initiation of antibiotic therapy despite continuing arthritis following treatment. Thus, chronic arthritis does not seem to involve molecular mimicry driven by a cross reaction between the OspA_165-173 epitope and a self-antigen in the joint. It is possible that molecular mimicry involves another B. burgdorferi antigen that is able to bind the MHC class II variants found in genetically susceptible individuals.

Other potential routes to autoimmunity in antibiotic-refractory Lyme arthritis patients emphasize the role of the high levels of key proinflammatory cytokines and chemokines found in their joint fluid, levels even higher than those found in treatment-responsive patients prior to initiation of antibiotic therapy:

• In a model known as bystander activation, the immune response to OspA_165-173 (or another B. burgdorferi antigen) causes an excessive inflammatory response that activates other T cells that react to autoantigens in the joint.
• The immune system is unable to turn off the intense inflammatory response associated with OspA_165-173 after the spirochetes are cleared from the joint.

Although much attention has been focused on the role of host genetics, a recent study indicates that the genetics of the pathogen could also influence the course of Lyme arthritis. In the July 2009 issue of Arthritis and Rheumatism, Allen Steere and his collaborators showed that antibiotic-refractory Lyme arthritis is associated with different strains of B. burgdorferi. The strains were typed from joint fluid samples collected before or during antibiotic treatment. Among the methods available to group B. burgdorferi isolates, they used the 16S-23S ribosomal RNA intergenic spacer type (RST), of which there are three. Antibiotic-refractory arthritis was defined as joint swelling lasting for at least 3 months after the start of antibiotic treatment. Antibiotic treatment consisted of 8 weeks of oral antibiotics or up to 4 weeks of antibiotics administered intravenously. Joint fluid from all 17 patients in the study tested positive by PCR for B. burgdorferi DNA prior to or during antibiotic treatment.

The authors found that all 7 Lyme arthritis patients infected with RST1 strains had the antibiotic-refractory form. Joint fluid was obtained after antibiotic treatment from 5 of the 7 patients; all 5 samples tested negative for B. burgdorferi DNA by PCR. In contrast, 2 of 6 and 3 of 4 infected with RST2 and RST3 strains, respectively, were successfully treated with antibiotics (see the table below from the Jones et al. 2009 article). A larger number of samples is needed to demonstrate that the difference observed between RST1 and RST2 strains is statistically significant, but there is a clear trend towards RST1 infections having the greatest association with antibiotic treatment failure and RST3 having the least, with RST2 having an intermediate effect. The duration of arthritis also depended on the infecting RST strain.


How do RST1 strains cause arthritis to persist even after the apparent eradication of the spirochetes by the recommended course of antibiotics? The investigators proposed that RST1 strains provoke a stronger inflammatory response in the joint than RST2 or RST3 strains. Coupled with an immune response to OspA_165-173 in genetically susceptible patients, this could cause inflammation to continue at high levels even after elimination of the spirochetes from the joints. RST1 strains may be more likely than the other genotypes to spark intense joint inflammation even in patients who are not genetically prone to antibiotic-refractory arthritis.

In future studies, it would be interesting to see if proinflammatory cytokine levels are related to the RST type that infects the joint. Ultimately, researchers need to identify the B. burgdorferi gene or genes whose variation among the RSTs causes the different treatment outcomes of Lyme arthritis.

Featured paper

Jones, K.L., McHugh, G.A., Glickstein, L.J., & Steere, A.C. (2009). Analysis of Borrelia burgdorferi genotypes in patients with Lyme arthritis: High frequency of ribosomal RNA intergenic spacer type 1 strains in antibiotic-refractory arthritis
Arthritis & Rheumatism, 60 (7), 2174-2182 DOI: 10.1002/art.24812

Other references

Drouin E.E., Glickstein, L., Kwok, W.W., Nepom, G.T., and Steere, A.C. (2008). Human homologues of a Borrelia T cell epitope associated with antibiotic-refractory Lyme arthritis. Molecular Immunology 45(1):180-189. DOI: 10.1016/j.molimm.2007.04.017

Kannian, P., Drouin, E.E., Glickstein, L., Kwok, W.W., Nepom, G.T., and Steere A.C. (2007). Decline in the frequencies of Borrelia burgdorferi OspA_161-175-specific T cells after antibiotic therapy in HLA-DRB1*0401-positive patients with antibiotic-responsive or antibiotic-refractory Lyme arthritis. The Journal of Immunology 179(9):6336-6342.

Shin J.J., Glickstein, L.J., and Steere, A.C. (2007). High levels of inflammatory chemokines and cytokines in joint fluid and synovial tissue throughout the course of antibiotic-refractory Lyme arthritis. Arthritis & Rheumatism 56(4):1325-1335. DOI: 10.1002/art.2241

Steere, A.C., Klitz, W., Drouin, E.E., Falk, B.A., Kwok, W.W., Nepom, G.T., and Baxter-Lowe, L.A. (2006). Antibiotic-refractory Lyme arthritis is associated with HLA-DR molecules that bind a Borrelia burgdorferi peptide. The Journal of Experimental Medicine 203(4):961-971. DOI: 10.1084/jem.20052471