Correlation between the response to Mycobacterium tuberculosis antigens and the tuberculin skin test in patients with rheumatoid arthritis in Colombia / Correlación de la respuesta a antígenos de Mycobacterium tuberculosis y la prueba cutánea de tuberculina en pacientes con artritis reumatoide

Introduction. Rheumatoid arthritis patients under treatment with anti-TNF-α are at a high risk of developing active tuberculosis, and therefore, screening for latent tuberculosis infection is recommended before anti-TNF-α therapy. Objective. To compare the tuberculin test and IFNγ production induced by culture filtrate proteins(CFPs) and Mycobacterium tuberculosis-specific CFP-10 antigens in rheumatoid arthritis patients. Materials and methods. An analytic transversal study was conducted in rheumatoid arthritis patients treated at Hospital Universitario San Vicente Fundación between January and December 2007. IFNγ production in response to CFPs and CFP-10 was measured in the supernatants of whole blood cultures and evaluated for correlations with tuberculin reactivity. The degree of concordance between both tests was also established. Results. Forty-five patients were included, of which 14 (31.1%) had a tuberculin reaction of ≥10 mm of induration, 9 (20%) produced IFNγ in response to CFP-10, and 7 were positive for both tests. The correlation between tests was r=0.53 (IC 95%:0.28-0.72), and the global concordance between tests was80%, with a Kappa coefficient of 0.48 (IC95%:0.20-0.76). Conclusions. Only two tuberculin (-)/CFP-10+ "anergic" patients were observed. By contrast, six tuberculin +/CFP-10(-) "tuberculin false-positive" patients were observed. These data suggest that the tuberculin test is not an appropriate tool for determining the need for tuberculosis prophylaxis.

Introducción. Los pacientes con artritis reumatoide bajo tratamiento con anti-TNFα están en alto riesgo de desarrollar tuberculosis activa, por lo cual se recomienda hacer la tamización para infección latente de tuberculosis, antes de iniciar el tratamiento. Objetivo. Comparar la prueba de tuberculina y la producción de IFNγ inducida por antígenos CFP (Culture Filtrate Protein) y antígenos específicos de Mycobacterium tuberculosis (CFP-10) para el diagnóstico de infección latente de tuberculosis en pacientes con artritis reumatoide. Materiales y métodos. Se llevó a cabo un estudio transversal analítico en pacientes con artritis reumatoide atendidos en el Hospital Universitario San Vicente Fundación, entre enero y diciembre de 2007, a los cuales se les determinó la producción de IFNγ en respuesta a CFP y CFP-10 en sobrenadantes de cultivos de sangre total, y se correlacionó con la reacción en la prueba de tuberculina. Además, se estableció el grado de concordancia entre ambas pruebas. Resultados. Se incluyeron 45 pacientes, de los cuales, 14 (31,1 %) tuvieron un diámetro de induración ≥10 mm (tuberculina positiva), nueve (20 %) produjeron IFNγ en respuesta a CFP-10, y siete fueron positivos para ambas pruebas. La correlación entre las pruebas fue de r=0,53 (IC95%: 0,28-0,72) y la concordancia global entre pruebas fue de 80 %, con un coeficiente kappa de 0,48 (IC95%: 0,20-0,76). Conclusiones. Solo se observaron dos pacientes con tuberculina positiva y CFP-10 positivo "anérgicos" y se encontraron seis pacientes con tuberculina positiva y CFP-10 negativa "falsos positivos para tuberculina", lo cual sugiere que la prueba de la tuberculina no es la más adecuada para indicar profilaxis para tuberculosis.

Role of PGL-I of M. leprae in TNF-alpha production by in vitro whole blood assay.

Phenolic glycolipid-I (PGL-I) is known to be a major antigen of Mycobacterium leprae. We have studied the influence of PGL-I on the production of Tumour Necrosis Factor alpha (TNF-alpha) using the in vitro whole blood assay. Armadillo-derived M. leprae (ADML) are thought to be depleted of PGL-I during the purification process. M. leprae obtained from mouse foot pad material (MFPML) has been subjected to a less rigorous purification process; their PGL-I coating is therefore believed to be more intact than that of ADML. PGL-I or ADML alone induced the secretion of minimal levels of TNF-alpha in whole blood assay; when added in combination, higher levels of this cytokine were observed. The highest TNF-alpha response was seen following stimulation with MFPML. MFP material not infected with ML did not elicit any response. The difference in TNF-alpha response shown by ADML and MFPML was postulated to be largely due to the presence of higher levels of PGL-I in MFPML. This increase in TNF-alpha production suggests that PGL-I may play a significant role in the induction of TNF-alpha during natural infection.