The anti-cyclic citrullinated peptide response in tuberculosis patients is not citrulline-dependent and sensitive to treatment

Serum samples of 134 patients with untreated mycobacterium infections (122 TB, 12 nontuberculous mycobacterium) were tested for antibodies against both the citrullinated (Cit) and the non-citrullinated (Arg) form of 2 cyclic synthetic peptides. In 33 patients, a follow-up sample was tested six months after starting anti-mycobacterial drugs.A substantial proportion of patients with mycobacterial infections demonstrated antibodies against 0401Cit, 0401Arg, 0722Cit and 0722Arg. Fourteen patients demonstrated anti-0401Cit, 83 anti-0401Arg, 22 anti-0722Cit and 61 anti-0722Arg, while none of these antibodies were detected in the 20 healthy controls. All the patients but one, who were anti-0401Cit and anti-0722Cit positive, demonstrated reactivity against the respective Arg peptide. In the subset of 33 patients with a follow-up test six months after starting treatment, the mean levels of antibodies to 0401Cit, 0401Arg, 0722Cit and 0722Arg significantly decreased after treatment. All the patients who were anti-0401Cit and anti-0722Cit positive turned negative after treatment. The presence of anti-0401Cit/Arg and anti-0722Cit/Arg was found to be significantly correlated with the presence of HIV.ACPA may be found in patients with TB. In most of the cases, the reactivity is citrulline independent. A positive cyclic citrullinated peptide (CCP) test in these patients should therefore be interpreted with care, and preferably followed by a control ELISA with a non-citrullinated antigen.A group of autoantibodies, anti-citrullinated protein antibodies (ACPA), has been described in patients with rheumatoid arthritis (RA) [1]. The specificity for RA has been shown to be up to 98% in comparison with 0 to 1% of healthy controls and 2 to 5% of disease controls [1]. ACPA (most frequently detected by a cyclic citrullinated peptide, CCP, test) are present early in the disease process and may even predict the development of RA [2]. Schellekens et al. [3] and Girbal-Neuhauser et al. [4] have