Nishitani Kohei, Beck Christopher A, Rosenberg Alexander F, Kates Stephen L, Schwarz Edward M, Daiss John L
Center for Musculoskeletal Research, University of Rochester Medical Center, Rochester, NY, USA.
Clin Orthop Relat Res. 2015 Sep;473(9):2735-49. doi: 10.1007/s11999-015-4354-2. Epub 2015 May 27.
Because immunity against Staphylococcus aureus has not been fully elucidated, there is no diagnostic test to gauge how robust a patient's host response is likely to be. Therefore, we aimed to develop a test for specific antibodies in serum with diagnostic and prognostic potential.
QUESTIONS/PURPOSES: We describe the development and validation of a multiplex immunoassay for characterizing a patient's immune response against 14 known S aureus antigens, which we then used to answer four questions: (1) Do certain antigens predominate in the immune response against S aureus? (2) Is there a predominant pattern of antigens recognized by patients and mice with infections? (3) Is the immunoglobulin G (IgG) response to any single antigen a useful predictor of ongoing S aureus infection? (4) Does measurement of the combined response against all 14 antigens provide a better predictor of ongoing infection?
A case-control study was performed. Sera were collected from 35 consecutive patients with S aureus culture-confirmed (methicillin-sensitive S aureus or methicillin-resistant S aureus) musculoskeletal infections (deep implant-associated, osteomyelitis, and cases of established septic arthritis). Patients were excluded only if they did not give informed consent for participation. Twenty-four patients had implant infections after total joint replacements, five had fracture implant infections, four had native knee infections, and two had chronic osteomyelitis without an implant. Control patients were chosen from a group of healthy, medically optimized patients scheduled to undergo elective arthroplasty. Control patients were matched for age (± 3 years), BMI (± 3 kg/m(2)), and sex as closely as possible to patients with infections. Sera from patients with S aureus infections and murine S aureus tibial implant infections were used to evaluate a multiplex immunoassay for immunoglobulin titers against 14 recombinant S aureus antigens. All patients were treated with organism-targeted antibiotic therapy and appropriate, timely surgery. Treatment response was monitored with clinical examination, erythrocyte sedimentation rate, C-reactive protein, and resampling of the infection site for the pathogen as needed. Elevated inflammatory markers or persistent positive culture results were considered evidence of ongoing infection. Treatment provided was considered standard-of-care therapy in our medical center and all patients were treated jointly with a board-certified infectious disease specialist.
Four antigens elicited more than 65% of the measurable IgG, the most dominant being against iron-regulated surface determinant protein B (IsdB). Patients with infections had different patterns of elevated IgG titers, so that no single titer was elevated in more than 50% of patients with infections (area under the curve [AUC] ≤ 0.80). Multivariate analysis of IgG titers yielded greater predictive power of S aureus infection (AUC = 0.896). Patients with infections who had high titers against IsdB (median of survivors, 7.28 [25%-75% range, 2.22-21.26] vs median of patients with infection-related death, 40.41 [25%-75% range, 23.57-51.37], difference of medians, 33.13; p = 0.043) and iron-regulated surface determinant protein A (IsdA) median of survivors, 2.21 [25%-75% range, 0.79-9.11] vs median of patients with infection-related death, 12.24 [25%-75% range, 8.85-15.95], difference of medians, 10.03; p = 0.043) were more likely to die from infections than those who did not have high titers of IsdB.
Measurement of the host antibody response is a predictor of ongoing infection that may prove to have prognostic value. Future studies will seek to enlarge the patient population with infections to allow us to reduce the number of antigens required to achieve a stronger predictive power.
Measurement of the immune response against S aureus with this diagnostic tool may help guide future studies on prophylaxis and therapy in an era of personalized medicine and pathogen-specific therapies.
由于针对金黄色葡萄球菌的免疫机制尚未完全阐明，目前尚无诊断测试来评估患者宿主反应的强度。因此，我们旨在开发一种检测血清中特定抗体的方法，该方法具有诊断和预后潜力。
问题/目的：我们描述了一种用于表征患者针对14种已知金黄色葡萄球菌抗原的免疫反应的多重免疫测定法的开发和验证，然后用其回答四个问题：（1）在针对金黄色葡萄球菌的免疫反应中，某些抗原是否占主导地位？（2）感染患者和小鼠识别的抗原是否存在主要模式？（3）免疫球蛋白G（IgG）对任何单一抗原的反应是否是正在进行的金黄色葡萄球菌感染的有用预测指标？（4）测量针对所有14种抗原的联合反应是否能更好地预测正在进行的感染？
进行了一项病例对照研究。从35例连续的金黄色葡萄球菌培养确诊（甲氧西林敏感金黄色葡萄球菌或耐甲氧西林金黄色葡萄球菌）的肌肉骨骼感染患者（深部植入物相关感染、骨髓炎和确诊的化脓性关节炎病例）中采集血清。仅在患者未给予知情同意参与时才将其排除。24例患者在全关节置换后发生植入物感染，5例发生骨折植入物感染，4例发生原发性膝关节感染，2例发生无植入物的慢性骨髓炎。对照患者选自一组计划进行择期关节成形术的健康、医学状况良好的患者。对照患者在年龄（±3岁）、体重指数（±3 kg/m²）和性别方面尽可能与感染患者匹配。使用来自金黄色葡萄球菌感染患者和小鼠金黄色葡萄球菌胫骨植入物感染的血清来评估针对14种重组金黄色葡萄球菌抗原的免疫球蛋白滴度的多重免疫测定法。所有患者均接受针对病原体的抗生素治疗和适当、及时的手术。通过临床检查、红细胞沉降率、C反应蛋白以及根据需要对感染部位进行病原体重新采样来监测治疗反应。炎症标志物升高或培养结果持续呈阳性被视为正在进行感染的证据。所提供的治疗被认为是我们医疗中心的标准治疗方法，所有患者均由一名获得董事会认证的传染病专家联合治疗。
四种抗原引发了超过65%的可测量IgG，其中最主要的是针对铁调节表面决定簇蛋白B（IsdB）。感染患者的IgG滴度升高模式不同，因此在超过50%的感染患者中没有单一滴度升高（曲线下面积[AUC]≤0.80）。对IgG滴度进行多变量分析得出金黄色葡萄球菌感染的预测能力更强（AUC = 0.896）。与感染相关死亡患者相比，针对IsdB滴度高的感染患者（幸存者中位数，7.28 [25%-75%范围，2.22-21.26] 对比感染相关死亡患者中位数，40.41 [25%-75%范围，23.57-51.37]，中位数差异，33.13；p = 0.043）以及针对铁调节表面决定簇蛋白A（IsdA）滴度高的患者（幸存者中位数，2.21 [25%-75%范围，0.79-9.11] 对比感染相关死亡患者中位数，12.24 [25%-75%范围，8.85-15.95]，中位数差异，10.03；p = 0.043）比那些没有高滴度IsdB的患者更有可能死于感染。
测量宿主抗体反应是正在进行感染的预测指标，可能具有预后价值。未来的研究将寻求扩大感染患者群体，以便我们能够减少获得更强预测能力所需的抗原数量。
使用这种诊断工具测量针对金黄色葡萄球菌的免疫反应可能有助于指导个性化医学和病原体特异性疗法时代的预防和治疗的未来研究。
