Identification of bacterial antigens and super antigens in synovial fluid of patients with arthritis: a cross sectional study

An accurate and prompt diagnosis of bacterial arthritis is essential for earlier treatment and a good outcome. Superantigens produced by Staph. Aureus are among the most lethal toxins. The paper objective was Identification of common bacterial antigens and S. aureus superantigens in synovial fluid [SF] of children with negative culture and direct smear for other bacteria except for S. aureus. In this cross-sectional study a total of 62 patients with a mean age of 11 +/- 3.8 years [range: 5 months-16 years] with acute arthritis in pediatric and orthopedic wards of Rasoul Hospital [2008-2010] were studied. Three common bacterial antigens [e.g. S.pneumonia, H.influenza, N. meningitis] using LPA [latex particle antigen] and Staphylococcal superantigens [TSSTl; Enterotoxin A; B; C] using ELISA method [ABcam; USA] were identified in 60 adequate SF samples with negative culture and negative direct smears [for other bacteria except for S. aureus. Staphylococcal superantigens were compared with S. aureus infection [positive culture or direct smear]. Positive bacterial antigens [LPA test] were found in 4 cases including two S. Pneumonia, one N. meningitis, and one H.influenza. S.aureus was diagnosed in 7 cases including 4 positive cultures and 3 positive smears. Staphylococcal superantigens [toxins] were found in 73% of SF samples. Some cases had 2 or 3 types of toxins. S. aureus toxins were reported in 47% of culture negative SF samples. Positive TSSTl, Enterotoxin B, Enterotoxin A, and Enterotoxin C were found in 47% [n= 28], 18% [n= 10], 39% [n= 22], and 39% [n=21] of cases respectively. The most common type of superantigens was TSSTl; and Enterotoxin A was the less common type. Except for Enterotoxin A, no relation between positive S. aureus culture and positive tests for superantigens in SF was found. S. aureus has a prominent role in septic arthritis. S.aureus toxins might have a prominent role in arthritis with negative SF culture. Rapid identification of bacterial antigens [LPA] or S.aureus superantigens [toxins] are valuable for diagnosis in cases with negative cultures. We recommend usage of complementary methods [e.g. antigen detection tests] in children. Those tests are cheaper and easier in comparison with PCR as a complex and time-taking method. Identification of S. aureus superantigens in SF of all cases with negative culture, or treatment with antagonist drugs needs further clinical trial studies

Interleucina-18 em pacientes com artrite idiopática juvenil: um marcador de atividade e gravidade de doença / Interleukin-18 as a maker of disease activity and severity in juvenile idiopathic athritis patients

Com o intuito de verificar a importância da IL-18 na patogênese da artrite idiopática juvenil (AIJ) foram mensurados os níveis de IL-18 no líquido sinovial (LS) e soro de 50 pacientes, sua correlação com parâmetros de atividade e gravidade de doença foi determinada. Os níveis de IL-1, IL-1Ra, IL-6 e IL-18 foram mais elevados no soro dos pacientes que nos controles. Os níveis de IL-18 do soro não diferiram dos níveis do LS, e ambos se correlacionaram positivamente com PCR, articulações ativas, escore radiológico e IL-1, IL-1Ra e IL-6 / In order to verify the importance of IL-18 in the pathogenesis of juvenile idiopathic arthritis (JIA) we measured IL-18 levels in synovial fluid (SF) and serum of 50 patients and their correlation with parameters of disease activity and severity was determined. The levels of IL-1, IL-1Ra, IL-6 and IL-18 were higher in patient’s sera than in controls. SF levels of IL-18 didn’t differ from those of serum. The levels of IL-18 (SF and serum) positively correlated with: CRP, active joints, radiological score and with IL-1, IL1Ra and IL-6...

Detection of antibodies against glucose 6-phosphate isomerase in synovial fluid of rheumatoid arthritis using surface plasmon resonance (BIAcore)

We have used a surface plasmon resonance biosensor (SPR, BIACORE 2000) to detect antibodies against glucose 6-phosphate isomerase (GPI) in synovial fluids of rheumatoid arthritis (RA) and osteoarthritis (OA). Recombinant human GPI proteins fused with or without NusA were expressed in E. coli, purified to homogeneity and immobilized in flow cells of CM5 sensor chips. The flow cells immobilized with NusA protein or bovine serum albumin were used to monitor non-specific binding. Synovial fluid samples from RA patients showed a significantly higher level of binding to recombinant GPI proteins than samples from OA patients. Proteins which bound to the recombinant GPI proteins were confirmed to be immunoglobulin through the administration of anti-human immunoglobulin. NusA fusion protein was excellent for this assay because of a low background binding activity in the SPR analysis and its advantage of increased solubility in recombinant protein production. These results suggested a useful utilization of recombinant NusA-GPI fusion protein for the detection of autoantibodies against GPI in RA patients.

Natural Killer Cell Activity in Rheumatoid Arthritis Measured by a Single Cell Cytotoxicity Assay

The natural killer(NK) cell activity of mononuclear cells (MNC) from peripheral blood (PB) and synovial fluid (SF) of 40 rheumatoid arthritis(RA) patients was investigated by employing 51-chromium-(51Cr) release microcytotoxicity and single cell cytotoxicity assays against K562 target cells. It has been revealed that SF-MNC from RA patients showed a significantly lower NK activity than PB-MNC from the same patients and this might be due to an impaired target binding capacity of the effector cells and not due to a deficiency of active NK cells.

In Vitro Study of Nonspecific Cellular Immunity in Rheumatoid Arthritis

Nonspecific immune parameters such as natural killer(NK) activity, antibody-dependent cellular cytotoxicity(ADCC), production of leukocyte migration inhibitory factor(LlF) and levels of immune complex(IC) were assessed in 47 patients with rheumatoid arthritis (RA) 20 with degenerative arthritis (DA) and 40 healthy controls. Peripheral blood (PB) as well as synovial fluid (SF) were collected from both RA and DA patients before treatment. Mononuclear cell suspensions and sera were prepared and submitted for the in vitro tests; 4-hr chromium-release assays using human K562 and mouse L1210 cells as targets for NK and ADCC assays respectively, 2-step agarose assay for LIF and platelet aggregation test for IC. Results revealed that 1) LIF activity of PB lymphocytes (PBL) from both RA and DA patients showed a significant (P < 0.05) decrease as compared with that from healthy controls. 2) PB-NK activity from RA patients showed an insignificant decrease as compared with that from DA or healthy controls. However, mononuclear cells isolated from SF (SFL) of RA patients exhibited significantly(P < 0.02) lower NK activity than PBL from the same patients. 3) In ADCC assays with PBL no significant differencies were observed among the 3 groups. 4) Higher titers of IC were detected in both PB and SF from RA patients than DA, and a negative correlation was found between serum IC levels and PB-NK activity. These data are discussed in light of previous reports, and a hypothesis regarding a decreased nonspecific cell-mediated immunity in conjunction with an increased humoral immune response, particularly in local sites, is proposed as one of the mechanisms underlying the pathogenesis of RA.