The Host Response: Toll Like Receptor Expression in Periprosthetic Tissues as a Biomarker for Deep Joint Infection

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1 The Host Response: Toll Like Receptor Expression in Periprosthetic Tissues as a Biomarker for Deep Joint Infection Cara Cipriano, MD, Aparna Maiti, PhD, Gregory Hale, MD, William A. Jiranek, MD. VCU Health System, Richmond, VA, USA. Disclosures: C. Cipriano: None. A. Maiti: None. G. Hale: None. W.A. Jiranek: 1; Depuy, Inc. 3B; Depuy, Inc. Introduction: Accurately detecting periprosthetic joint infection (PJI) is critical to patient care and outcomes, yet there is no gold standard for this diagnosis. Toll like receptors (TLRs) 1 and 6 are consistent molecular indicators of the host inflammatory response against bacterial infection. Our purpose was to determine whether TLR elevation could be detected in periprosthetic tissues and to assess the utility of these biomarkers as tests for PJI. Methods: Under an IRB approved protocol, 59 patients undergoing revision total joint arthroplasty (29 hip and 28 knee) were prospectively evaluated for PJI according to currently recommended diagnostic criteria. 9 patients were excluded based on insufficient workup, leaving 50 available for study. Of these, 21 were designated infected and 29 noninfected. Periprosthetic tissues were collected intraoperatively and total ribonucleic acid (RNA) extracted via standard techniques. TLR mrnas expression was assessed by first strand cdna synthesis from 1μg of total RNA, followed by real time polymerase chain reaction (PCR). Samples were normalized relative to the housekeeping gene GAPDH. TLR1, 6, and 10 expression in the infected versus noninfected groups were compared using a student t test. Receiver operating characteristic curves, area under the curves (AUC), sensitivity, specificity, positive Likelihood Ratio (LR+), and negative Likelihood Ratio (LR-) were calculated to determine the accuracy of each TLR for predicting PJI at its optimal diagnostic threshold. Results: TLR1 and 6 mrna expression were significantly elevated in infected compared to noninfected samples (p=0.0003, CI= and p=0.0059, CI= , respectively), while TLR10 was not (p=0.6238, CI=-9.436x x10-4). AUCs were for TLR1, for TLR6, and for TLR10. Optimal thresholds for diagnosing PJI were for TLR1 (95.2% sensitivity, 93.1% specificity, LR , LR- 0.70) and for TLR6 (85.7% sensitivity, 82.8% specificity, LR+ 4.98, LR- 0.83). Discussion: In our pilot study, TLR1 expression in periprosthetic tissues most accurately predicted PJI. This measure of the host response may be particularly helpful in detecting culture-negative infections and avoiding false positives resulting from contamination. Significance: Our pilot study suggests that TLRs could be valuable biomarkers in the assessment of PJI, particularly in detecting culture-negative infections and avoiding false positives from contamination. Acknowledgments: Special thanks to our colleagues in the Department of Orthopaedic surgery for their assistance in sample collection. This research was funded by the Department of Orthopaedic Surgery, Virginia Commonwealth University School of Medicine. References: 1. Steckelberg JM, Osmon DR. Prosthetic joint infections. In: Waldvogel FA, Bisno AL, Eds. Infections associated with indwelling medical devices. 3rd ed. Washington, D.C.: American Society for Microbiology, 2000: Harris WH, Sledge CB. Total hip and total knee replacement. N Engl J Med 1990; 323: Schafroth M, Zimmerli W, Brunazzi M, Ochsner PE. Infections. In: Ochsner PE, Ed. Total hip replacement. Berlin: Springer- Verlag, 2003: Workgroup Convened by the Musculoskeletal Infection Society. New definition for periprosthetic joint infection. J Arthroplasty Dec;26(8): Della Valle C, Parvizi J, Bauer TW, DiCesare PE, Evans RP, Segreti J, Spangehl M, Watters WC 3rd, Keith M, Turkelson CM, Wies JL, Sluka P, Hitchcock K; American Academy of Orthopaedic Surgeons. American Academy of Orthopaedic Surgeons clinical practice guideline on: the diagnosis of periprosthetic joint infections of the hip and knee. J Bone Joint Surg Am Jul 20;93(14): Choi HR, Kwon YM, Freiberg AA, Nelson SB, Malchau H. Periprosthetic Joint Infection with Negative Culture Results: Clinical Characteristics and Treatment Outcome. J Arthroplasty Mar 20. doi:pii: S (13) Trampuz A, Steckelberg JM, Osmon DR,Cockerill FR, Hanssen AD, Patel R. Advances in the laboratory diagnosis of prosthetic joint infection. Rev Med Microbiol 2003;14: Hopkins PA, Sriskandan S. Mammalian Toll-like receptors: to immunity and beyond. Clin Exp Immunol 2005 Jun;140(3): Hashimoto C, Hudson KL, Anderson KV. The Toll gene of Drosophila, required for dorsal-ventral embryonic polarity, appears to encode a transmembrane protein. Cell 1988 Jan 29;52(2): Medzhitov R, Preston-Hurlburt P, Janeway CA,Jr. A human homologue of the Drosophila Toll protein signals activation of adaptive immunity. Nature 1997 Jul 24;388(6640): Hasan UA, Trinchieri G, Vlach J. Toll-like receptor signaling stimulates cell cycle entry and progression in fibroblasts. J Biol Chem 2005 May 27;280(21):

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3 0.83) Table 1: TLR expression in periprosthetic tissues. Mean, minimum, and maximum levels of TLR1, 6, and 10 mrna expression in patients undergoing revision total joint arthroplasty. Patients were designated infected or noninfected according to current diagnostic recommendations. Table 2: Standard errors, asymptomatic significance, and confidence intervals of AUCs for TLR1, 6, and 10. The nonparametric

4 assumption was used to calculate the standard error, and the null hypothesis area of 0.5 for asymptomatic significance. ORS 2014 Annual Meeting Poster No: 0104

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