Serum Protein Profile in Systemic-Onset Juvenile Idiopathic
Systemic-onset juvenile idiopathic arthritis (SJIA) is a disease of unknown etiology with an unpredictable response to treatment. We examined two groups of patients to determine whether there are serum protein profiles reflective of active disease and predictive of response to therapy. The first group ( n = 8) responded to conventional therapy. The second group ( n = 15) responded to an experimental antibody to the IL-6 receptor (MRA). Paired sera from each patient were analyzed before and after treatment, using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS). Despite the small number of patients, highly significant and consistent differences were observed before and after response to therapy in all patients. Of 282 spectral peaks identified, 23 had mean signal intensities significantly different ( P < 0.001) before treatment and after response to treatment. The majority of these differences were observed regardless of whether patients responded to conventional therapy or to MRA. These peaks represent potential biomarkers of active disease. One such peak was identified as serum amyloid A, a known acute-phase reactant in SJIA, validating the SELDI-TOF MS platform as a useful technology in this context. Finally, profiles from serum samples obtained at the time of active disease were compared between the two patient groups. Nine peaks had mean signal intensities significantly different ( P < 0.001) between active disease in patients who responded to conventional therapy and in patients who failed to respond, suggesting a possible profile predictive of response. Collectively, these data demonstrate the presence of serum proteomic profiles in SJIA that are reflective of active disease and suggest the feasibility of using the SELDI-TOF MS platform used as a tool for proteomic profiling and discovery of novel biomarkers in autoimmune diseases.
Systemic-onset juvenile idiopathic arthritis (SJIA) is a form of childhood arthritis of unknown etiology, characterized by systemic features in addition to arthritis, including spiking fever, erythematous rash, articular involvement, and other, visceral manifestations. Its clinical course is associated with changes in the levels of several serum proteins, including IL-6. Over half of children with SJIA eventually recover almost completely. The other half have severe, unremitting arthritis, poorly responsive to conventional therapy, leading to poor functional outcome and substantial morbidity. In view of the heterogeneity of clinical disease manifestations and the unpredictability of treatment responses in SJIA, there would be great clinical benefit in the discovery of biomarkers reflective of disease activity and predictive of response to therapy.
Proteomics, or protein pattern analysis, is the characterization and quantitation of proteins in tissues and body fluids. Proteomic methods can be used to compare protein expression patterns between disease states. Although two-dimensional gel electrophoresis has been the primary technique in conventional proteomic analysis, it is relatively insensitive to proteins of low abundance and below 10 kDa in mass, is labor intensive, and has low throughput. A more recent technology known as surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS), a derivative of conventional matrix-associated laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), involves the application of a biologic sample, such as serum, to a protein-binding chip. The chip is irradiated with a laser, resulting in ionization of the adherent molecules. The ions travel through a vacuum tube and their mass-to-charge ratios are calculated from their time of flight through the vacuum chamber. The technology is high throughput, rapid, and sensitive and provides a profile of low-molecular-weight peptides and proteins within a complex mixture such as serum.
SELDI-TOF MS does not directly identify specific proteins. It has been used to differentiate disease states from nondisease states by analysis of protein profiles in sera. Examples include the differentiation of neoplastic from non-neoplastic breast masses, prognostic and diagnostic classification of breast cancer, neoplastic versus non-neoplastic disease of the ovary, and prostate cancer from both men with benign hyperplasia and healthy men. SELDI-TOF MS has also been used for the discovery of disease-related biomarkers in sera. Examples include detection of serum amyloid α in patients with renal cancer and the quantitation of prostate-specific membrane antigen in prostate cancer.
The present study was designed to determine whether there are serum proteomic profiles in SJIA that are reflective of active disease and predictive of response to therapy, as well as to determine whether SELDI-TOF MS could be used as a tool for proteomic profiling and for discovery of novel biomarkers of SJIA.
Systemic-onset juvenile idiopathic arthritis (SJIA) is a disease of unknown etiology with an unpredictable response to treatment. We examined two groups of patients to determine whether there are serum protein profiles reflective of active disease and predictive of response to therapy. The first group ( n = 8) responded to conventional therapy. The second group ( n = 15) responded to an experimental antibody to the IL-6 receptor (MRA). Paired sera from each patient were analyzed before and after treatment, using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS). Despite the small number of patients, highly significant and consistent differences were observed before and after response to therapy in all patients. Of 282 spectral peaks identified, 23 had mean signal intensities significantly different ( P < 0.001) before treatment and after response to treatment. The majority of these differences were observed regardless of whether patients responded to conventional therapy or to MRA. These peaks represent potential biomarkers of active disease. One such peak was identified as serum amyloid A, a known acute-phase reactant in SJIA, validating the SELDI-TOF MS platform as a useful technology in this context. Finally, profiles from serum samples obtained at the time of active disease were compared between the two patient groups. Nine peaks had mean signal intensities significantly different ( P < 0.001) between active disease in patients who responded to conventional therapy and in patients who failed to respond, suggesting a possible profile predictive of response. Collectively, these data demonstrate the presence of serum proteomic profiles in SJIA that are reflective of active disease and suggest the feasibility of using the SELDI-TOF MS platform used as a tool for proteomic profiling and discovery of novel biomarkers in autoimmune diseases.
Systemic-onset juvenile idiopathic arthritis (SJIA) is a form of childhood arthritis of unknown etiology, characterized by systemic features in addition to arthritis, including spiking fever, erythematous rash, articular involvement, and other, visceral manifestations. Its clinical course is associated with changes in the levels of several serum proteins, including IL-6. Over half of children with SJIA eventually recover almost completely. The other half have severe, unremitting arthritis, poorly responsive to conventional therapy, leading to poor functional outcome and substantial morbidity. In view of the heterogeneity of clinical disease manifestations and the unpredictability of treatment responses in SJIA, there would be great clinical benefit in the discovery of biomarkers reflective of disease activity and predictive of response to therapy.
Proteomics, or protein pattern analysis, is the characterization and quantitation of proteins in tissues and body fluids. Proteomic methods can be used to compare protein expression patterns between disease states. Although two-dimensional gel electrophoresis has been the primary technique in conventional proteomic analysis, it is relatively insensitive to proteins of low abundance and below 10 kDa in mass, is labor intensive, and has low throughput. A more recent technology known as surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS), a derivative of conventional matrix-associated laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), involves the application of a biologic sample, such as serum, to a protein-binding chip. The chip is irradiated with a laser, resulting in ionization of the adherent molecules. The ions travel through a vacuum tube and their mass-to-charge ratios are calculated from their time of flight through the vacuum chamber. The technology is high throughput, rapid, and sensitive and provides a profile of low-molecular-weight peptides and proteins within a complex mixture such as serum.
SELDI-TOF MS does not directly identify specific proteins. It has been used to differentiate disease states from nondisease states by analysis of protein profiles in sera. Examples include the differentiation of neoplastic from non-neoplastic breast masses, prognostic and diagnostic classification of breast cancer, neoplastic versus non-neoplastic disease of the ovary, and prostate cancer from both men with benign hyperplasia and healthy men. SELDI-TOF MS has also been used for the discovery of disease-related biomarkers in sera. Examples include detection of serum amyloid α in patients with renal cancer and the quantitation of prostate-specific membrane antigen in prostate cancer.
The present study was designed to determine whether there are serum proteomic profiles in SJIA that are reflective of active disease and predictive of response to therapy, as well as to determine whether SELDI-TOF MS could be used as a tool for proteomic profiling and for discovery of novel biomarkers of SJIA.
SHARE
