Knee acoustic emission: a potential biomarker for quantitative assessment of joint ageing and degeneration.

Based on a single time-point study of 34 healthy and 19 osteoarthritic knees in three different age groups (early, middle and late adulthood), this paper reports the potential of knee acoustic emission as a biomarker to monitor joint ageing and degeneration. Measurements were made of short transient high frequency acoustic emission signals generated by knee joints under stress during repeated sit-stand-sit movements along with joint angle. A statistically significant feature profile was established using a four-phase model of sit-stand-sit movements and two waveform features. The four-phase movement model is derived from joint angle measurement during repeated sit-stand-sit movements, and it consists of the ascending-acceleration and ascending-deceleration phases in the sit-to-stand movement, followed by the descending-acceleration and descending-deceleration phases in the stand-to-sit movement. The two statistically significant waveform features are extracted from AE measurement during repeated sit-stand-sit movements, and they consist of the peak magnitude value and average signal level of each AE burst. In addition to the use of bilateral plots, statistical distributions and 2D colour histograms to visualise the differences and similarities among participants, use of principal component analysis showed not only distinct data clusters corresponding to participating groups, but also an age- and disease-related trajectory progressing from the early adulthood healthy group to the late adulthood healthy group followed by the middle adulthood osteoarthritic group to the late adulthood osteoarthritic group. Furthermore, this trajectory shows increasing areas for each data cluster, with a highly compact cluster for the early adulthood healthy group at one end and a widely spread cluster for the late adulthood osteoarthritic group at the other end. From these results, a strong basis is formed for further development of knee acoustic emission as a convenient and non-invasive biomarker for quantitative assessment of joint ageing and degeneration.

Outcome of active disease in ankylosing spondylitis: a prospective study.

BACKGROUND: People with ankylosing spondylitis (AS) typically experience episodic exacerbations, but the extent to which they subsequently experience a sustained reduction in disease markers below recognized thresholds for active disease is unclear. OBJECTIVE: To investigate changes in, and associations between, disease markers over 18 months in people with active AS. METHODS: Within a cohort of 89 participants with AS, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) scores of 4 or higher were used to identify those with active disease. Standard assessment tools were used to monitor participants prospectively at four consecutive six-monthly intervals. Participants received standard treatments but none received anti-tumor necrosis factor-alpha (TNFalpha) medication during the study. RESULTS: The median age of the cohort was 50 years (inter-quartile range [IQR] 38.5-55.5), the median age of disease onset was 25 years (IQR 18-33) and the median disease duration was 18 years (IQR 13-27). Forty-seven (53%) participants had a BASDAI score of 4 or higher on the first assessment, of whom 45 (51%) scored 4 or higher on all subsequent assessments. Furthermore, 38 (43%) and 16 (18%) participants scored BASDAI 5 or 6, respectively, or higher, throughout. BASDAI scores correlated strongly with Bath Ankylosing Spondylitis Functional Index (BASFI) scores. Compared with 19 (21%) participants whose BASDAI scores were consistently below 4 throughout, participants with persistently high BASDAI scores showed higher scores for anxiety and depression, and some evidence of functional deterioration during the study period. CONCLUSIONS: In this cohort, disease markers in most people with active AS were sustained above the standard threshold for active disease. This has important implications for planning care pathways and for optimal utilization of anti-TNFalpha treatment.

Exploratory study of a non-invasive method based on acoustic emission for assessing the dynamic integrity of knee joints.

The paper presents the development of a new measurement system based on acoustic emission (AE) for assessing the dynamic integrity of knee joints, and the evaluation of its efficacy, through an exploratory study using healthy and osteoarthritic knees. For the former, the paper describes the system implemented to acquire joint angle-based AE and the protocol developed to obtain repeatable results. For the latter, the paper reports significant differences between healthy and osteoarthritic knees using statistical analysis of AE occurrence and distribution of AE features in different movement phases. Osteoarthritic knees are found to produce 6-10 times more acoustic emissions than healthy knees, with amplitudes which can be 20 dB higher, and durations which can be 10 times longer. These findings lead to a visual representation method of AE feature profiles based on multidimensional density of AE hits per repeated movement and the use of principal component analysis for objective assessment of the clinical status of knee joints.

Development and validation of a patient-centred Measure of Activity Limitation (MAL) in rheumatoid arthritis.

OBJECTIVE: This study sought to understand patients' experiences of activity limitation in rheumatoid arthritis (RA) to inform the development and preliminary validation of a new patient-centred assessment tool. METHODS: Interviews, focus groups and diaries provided insight into patients' experiences of change in activity limitation. These data informed item generation for the Measure of Activity Limitation (MAL) questionnaire. Postal surveys, comprising the MAL, Short Form 36 (SF36) and Health Assessment Questionnaire (HAQ), were used to inform item reduction and assess the MAL's validity, reliability and sensitivity. RESULTS: Qualitative exploration of activity limitation with 30 patients led to the development of a 36-item questionnaire addressing the impact of symptoms on activity, difficulty in global function and difficulty in task performance. Analysis of data from a postal survey of 168 patients led to the development of a 19-item questionnaire which demonstrated moderate correlations with the HAQ and relevant scales of the SF36. A second postal questionnaire, completed on two occasions by 308 patients, assessed test-retest reliability. One hundred and ninety-three people reporting no change in disease showed mean change in MAL score between the two completions of 0.41 [95% confidence interval (CI) -0.38 -1.22)], demonstrating test-retest reliability. Thirty-two patients reporting improvement showed a mean change of -7.84 (95% CI -11.15 to -4.54) and 83 reporting deterioration showed mean change of 4.63 (95% CI 3.09-6.16), suggesting that the MAL is sensitive to self-reported clinical change. CONCLUSION: Our results suggest that the MAL is valid, reliable and sensitive to self-reported change. The MAL may provide a useful patient-centred adjunct to existing measures of activity limitation.

Disease and psychological status in ankylosing spondylitis.

OBJECTIVES: Psychological factors may be important in the assessment and management of ankylosing spondylitis (AS). Our primary objective was to describe associations between disease and psychological status in AS, using AS-specific assessment tools and questionnaires. Our secondary objectives were to identify patient subgroups based on such associations and to determine the stability of the measures over time. METHODS: A total of 110 patients were assessed at 6-monthly intervals up to four times using tools to measure disease [Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI) and the Bath Ankylosing Spondylitis Metrology Index (BASMI)], psychological [Hospital Anxiety and Depression Questionnaire (HADS), Health Locus of Control-Form C Questionnaire (HLC-C)] and generic health [Short form (SF)-36] status. RESULTS: Eighty-nine participants completed all four assessments. Throughout the study, BASDAI, BASFI and BASMI scores correlated significantly with anxiety, depression, internality and health status, but not with levels of belief in chance or powerful others. Clinically anxious or depressed subgroups had significantly worse BASDAI and BASFI, but not BASMI, scores. BASMI scores were the least closely linked to psychological status. Mean scores for disease, psychological and health status were clinically stable over the 18 months period. CONCLUSIONS: Disease status scores in AS correlated significantly with anxiety, depression, internality and health status. Interpretation of AS disease scores should take an account of psychological status and the choice of measures used. These findings have important potential applications in AS management and monitoring, including the identification of patients for biological therapies.

Factors influencing the beliefs of patients with rheumatoid arthritis regarding disease-modifying medication.

OBJECTIVE: To investigate factors influencing the beliefs of patients with rheumatoid arthritis (RA) regarding disease-modifying medication. METHOD: Twenty-nine patients with RA either starting a disease-modifying anti-rheumatic drug (DMARD) for the first time or changing DMARD were recruited. Semi-structured interviews, activity diaries and focus groups were conducted over 9 months. A coding framework was developed and data analysed using the constant comparative method to identify key themes. RESULTS: DMARDs were perceived as central to the management of RA but strong concerns were expressed about potential long-term effects. Beliefs about DMARDs were informed by material from a wide range of sources. Judgements of efficacy were influenced by symptom relief, occurrence of side-effects and perception of alternative treatment options. Perception, reporting and tolerance of side-effects differed widely between individuals. The emotional impact of starting and being withdrawn from medication appeared stronger in people with more experience of DMARD use. CONCLUSIONS: Patients have complex and evolving belief systems relating to DMARDs. Understanding these systems will facilitate the provision of appropriate information and effective support not only in decision-making about treatment but also in relation to discontinuing treatment.

Health problems following Campylobacter jejuni enteritis in a Lancashire population.

OBJECTIVES: Campylobacter jejuni enteritis can lead to musculoskeletal, neuropathic or other health sequelae. We investigated the coexistence, seasonal occurrence, strain-type associations and impact on work capacity of different health problems following C. jejuni enteritis in a Lancashire population during 1999 and 2001. METHODS: A semistructured questionnaire was used to characterize health problems that occurred in the community after laboratory-confirmed episodes of C. jejuni enteritis. The questionnaire was posted to all adults in the Preston and Chorley area who developed C. jejuni enteritis in 1999 or 2001. All Campylobacter isolates from this population were serotyped. RESULTS: Several types of sequelae occurred consistently in both years, including the coexistence of musculoskeletal and neuropathic problems. There was no evidence of C. jejuni strain-type associations or seasonal preponderance for any type of sequela. The overall health impact of C. jejuni enteritis, as measured by workdays lost, was high in this population. CONCLUSIONS: A variety of health problems occur consistently following C. jejuni enteritis and substantially increase morbidity due to campylobacteriosis in the community.

Serum antibodies to group A streptococcal extracellular and cell-associated antigens in Egyptians with post-streptococcal diseases.

We investigated serum antibodies to a comprehensive array of group A streptococcal antigens and superantigens in Egyptian subjects. Antibodies to Streptococcus pyogenes cell-associated proteins and to proteins released by rapidly dividing S. pyogenes were compared in four patient groups with different post-streptococcal diseases and in healthy controls. Enzyme-linked immunosorbent assays showed that total Ig and IgG to extracellular antigens were significantly higher in patients with acute rheumatic fever (ARF) compared to healthy controls, but no differences were found in either total Ig or IgG titres to cell-associated proteins between any of the groups. Western blotting showed that multiple extracellular and cell-associated antigens, covering a wide range of molecular masses, were recognised by all sera, including healthy controls. No evidence was obtained for putative dominant antigens associated with any disease group, although a low molecular mass cell-associated protein (approximately 4 kDa) was clearly recognised by two-thirds of subjects irrespective of disease status. These findings demonstrate that raised serum Ig and IgG titres to extracellular, but not cell-associated, S. pyogenes antigens are a feature of ARF in this population, and suggest that multiple S. pyogenes antigens contribute to this response.

Characterization of an isogenic mutant of Streptococcus pyogenes Manfredo lacking the ability to make streptococcal acid glycoprotein.

An isogenic mutant of Streptococcus pyogenes Manfredo that lacks the ability to make streptococcal acid glycoprotein (SAGP) has been constructed by inserting a deletion in the sagp gene using the method of allelic exchange. An assay of cell extracts (CE) prepared from the wild-type and mutant Manfredo strains for the enzyme arginine deiminase (AD) showed that significant activity was present in wild-type CE but none could be detected in mutant CE. These findings confirm our earlier conclusion that SAGP has AD activity (B. A. Degnan, J. M. Palmer, T. Robson, C. E. D. Jones, M. Fischer, M. Glanville, G. D. Mellor, A. G. Diamond, M. A. Kehoe, and J. A. Goodacre, Infect. Immun. 66:3050-3058, 1998). Wild-type CE but not mutant CE potently inhibited human peripheral blood mononuclear cell proliferation in response to phytohemagglutinin, and this inhibition was overcome by the addition of L-arginine to proliferation assay mixtures. Invasion assays showed that the isogenic mutant organisms lacking SAGP, and thus AD activity, were between three and five times less able to enter epithelial cells (Hep-2C and A549) than were the wild-type streptococci. Both wild-type and mutant S. pyogenes bacteria were extremely sensitive to low pH. However, L-arginine (1 mM or above) significantly increased the viability of the wild type but not the isogenic mutant organisms under acidic conditions. The difference in acid susceptibility between wild-type and mutant bacteria may explain the reduced capacity of the isogenic mutant bacteria to invade and survive intracellularly.

Inhibition of human peripheral blood mononuclear cell proliferation by Streptococcus pyogenes cell extract is associated with arginine deiminase activity.

Streptococcus pyogenes (group A Streptococcus) cell extracts (CE) have a remarkably powerful and dose-dependent inhibitory effect on antigen, superantigen, or mitogen-stimulated human peripheral blood mononuclear cell (PBMC) proliferation in vitro. Purification of the inhibitory component present in S. pyogenes type M5 (Manfredo strain) CE by anion-exchange chromatography followed by gel filtration chromatography showed that the inhibitor had an approximate native molecular mass of 100 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified inhibitory fractions followed by silver staining gave a single band with an approximate molecular mass of 47 kDa, indicating that the inhibitor is composed of two identical subunits. NH2-terminal sequencing of the protein revealed that it was identical to the previously characterized streptococcal acid glycoprotein (SAGP); this protein possesses between 31.5 and 39.0% amino acid identity with arginine deiminase (AD) from Mycoplasma hominis, Mycoplasma arginini, Pseudomonas putida, and Pseudomonas aeruginosa. AD enzyme activity was present in unfractionated CE prepared from a range of streptococcal strains, and partially purified inhibitory fractions of Manfredo CE also had high levels of activity. The inhibitory effect of Manfredo CE was overcome by the addition of L-arginine to proliferation assays in which human PBMC were stimulated with phytohemagglutinin. We conclude that SAGP, or its homolog, possesses AD activity and that the potent inhibition of proliferation of human T cells by streptococcal CE is due to activity of this enzyme.

Cryptic T-cell epitopes and their role in the pathogenesis of autoimmune diseases.

Immune recognition of self-proteins features prominently in the early pathogenesis of autoimmune rheumatic diseases such as rheumatoid arthritis (RA), Sjögren's syndrome (SS), systemic lupus erythematosus (SLE) and systemic sclerosis. The mechanisms which provide lymphocytes with access to such autoantigens are therefore fundamental in creating the opportunity for autoimmune responses to develop. It has long been thought that the tissue or cellular location of some self-proteins may determine that they are normally 'hidden' from immune recognition, thereby reducing their potential for autoantigenicity. Recently, this concept has been extended to apply even to different epitopes within the same protein. Many studies, encompassing a wide variety of antigens, have shown that some epitopes are not presented for recognition by T lymphocytes unless they are produced in unusually large concentrations or unless they are freed from the configuration of their native antigen. Epitopes for which this phenomenon occurs are described as cryptic. There is increasing interest in the possibility that crypticity may be an important characteristic of epitopes which are recognized by T lymphocytes in autoimmune pathogenesis. The evidence which has led to this theory and its significance are reviewed.

Streptococcus pyogenes type 5 M protein is an antigen, not a superantigen, for human T cells.

M proteins are coiled-coil dimers expressed on group A streptococcal cell surfaces. They have an important role in host antistreptococcal immunity and in poststreptococcal autoimmune sequelae. Controversy has arisen regarding whether type 5 M proteins are superantigenic for human T cells. To investigate this, we have produced and tested M5 in the form of two novel recombinant proteins. We found no evidence of superantigenicity using either recombinant whole M5 protein (rM5) or recombinant pep M5 protein (rpepM5) to activate peripheral blood mononuclear cells (PBMC) from healthy adult volunteers. Short-term, rM5-specific T-cell lines from different subjects were uniformly self-APC restricted and showed no consistent pattern of TCR V beta usage. A synthetic peptide of M5 residues 217-237 was found to contain epitope(s) recognized by some rM5-specific human T cells. PBMC responses to rM5 and rpepM5 in 3- and 7-day proliferation assays were characteristic of antigenic rather than superantigenic stimulation. We conclude that type 5 M protein activates human T cells as a conventional antigen.

Analysis of human T cell responses to group A streptococci using fractionated Streptococcus pyogenes proteins.

Cell extract and spent culture supernatant proteins from Streptococcus pyogenes Manfredo strain (type M5) were each separated to give 22 narrow range molecular weight fractions by blot-elution from SDS-polyacrylamide gels. Eluted samples and unfractionated proteins were screened for T cell stimulatory activity using human peripheral blood mononuclear cells (PBMC) from healthy adults in proliferation assays. Responses were measured in 4- and 7d cultures. Responses to a wide range of cell extract proteins were revealed by fractionation, the degree of response to each fraction varying between donors. Unfractionated culture supernatant proteins elicited proliferative responses by PBMC from all individuals examined. Responses to culture supernatant fractions containing 25-33 kDa proteins could be attributed to known superantigens. Furthermore, samples from culture supernatants containing higher molecular weight fractions (> 45 kDa) elicited responses in 50% of donors in 7d cultures, suggesting that these fractions contained common recall antigens. The efficacy of using electroeluted samples to identify T lymphocyte stimulatory proteins was confirmed by demonstrating that a known superantigen of S. pyogenes Manfredo strain, streptococcal pyrogenic exotoxin C (SPEC), could be fractionated successfully using this method and its activity recovered. Our results show that human T cell responses to group A streptococci involve a remarkably wide range of both cell-associated and released streptococcal proteins.

Limitations of flow cytometry in the analysis of CD1a/HLADR+ human oral mucosal Langerhans cells.

Suspensions of human oral epithelial cells were stained with antibodies to CD1a and HLADR conjugated with fluorochromes and analysed by flow cytometry with the aim of purifying double-labelled Langerhans cells, a population comprising approximately 2% of the cell total. Whole suspensions had high levels of autofluorescence and a wide range of forward and right angle scatter properties. The mean percentage of CD1a/HLADR+ cells was 2.1%, though the double-labelled cells did not form a discrete group and the percentages of positive cells using control antibodies were similar. Density gradient centrifugation prior to flow cytometry did not facilitate Langerhans cell identification within the suspension. The results indicate flow cytometric analysis of minority cell populations (such as Langerhans cells) within oral epithelium is limited by the autofluorescence of physically heterogeneous keratinocytes, and emphasize the importance of controls in studies of oral epithelium which use this method.

Group A streptococcal antigens and superantigens in the pathogenesis of autoimmune arthritis.

Evidence from repeated clinical observations and from a variety of experimental approaches implicates group A streptococci in the pathogenesis of the autoimmune arthritides. Several streptococcal antigens and superantigens have now been characterized and their properties suggest that they may be involved in the mechanisms which underlie these diseases, although other antigens and superantigens yet to be discovered may also be involved. The association between group A streptococcal infection and autoimmune arthritis offers a useful model for providing a long-elusive understanding of the role of bacterial infection in the pathogenesis of autoimmune disease.

Bacterial superantigens in autoimmune arthritis.

Discoveries of the biological properties of bacterial superantigens have given rise to much speculation about their possible role in the pathogenesis of autoimmune diseases. There is an increasing body of data to support these speculations. This field of research has the potential to provide a long-elusive understanding of the mechanisms which underlie microbial involvement in the pathogenesis of autoimmune polyarthritides.