Induction of ANAs and anti-dsDNA antibodies during treatment with anti-TNF-α agents was highlighted in clinical trials and in postmarketing surveillance [3
]. In a recent study, detection of ANAs among RA patients was reported to increase from 51.6% to 82.3% after treatment with infliximab plus methotrexate, and even higher figures were reported in patients with ankylosing spondylitis who were treated with slightly higher infliximab doses without methotrexate comedication [7
]. In the same study anti-dsDNA antibodies, demonstrated by both IIF and ELISA, developed in 11.3% of RA patients after 30 weeks. Interestingly, all of the anti-dsDNA antibodies after infliximab were of IgA and/or IgM isotype, whereas it is known that lupus-associated anti-dsDNA antibodies are classically of the IgG isotype [26
]. This may explain why the actual incidence of SLE or related disorders after infliximab treatment is very low despite a significant rise in anti-dsDNA antibodies [3
]. Nonetheless, several cases of anti-dsDNA antibodies associated with clinical manifestations of SLE have been reported in RA patients treated with infliximab or etanercept [28
], and in all but one case [33
] these clinical features disappeared completely after stopping treatment.
The results of the present study confirm induction of ANAs and anti-dsDNA antibodies after 30 and 54 weeks of treatment. Our findings are very similar to those reported by De Rycke and coworkers [7
] after 30 weeks of therapy using comparable assays. ANAs were present in 50% of patients before therapy and in 76.7% after 54 weeks; anti-dsDNA antibodies were detected by ELISA in 6.7% before therapy and in 16.7% after 54 weeks. Regarding anti-dsDNA antibodies detected using IIF, we used a fluorescence-labelled conjugate specifically directed toward human γ chains in order to detect only the IgG anti-dsDNA that are strictly associated with SLE [26
]. As expected, the frequency of these antibodies was lower, and only one patient converted from negative to positive during infliximab treatment.
At long-term analysis, up to 78 weeks, there was a progressive increase in the percentage of ANA-positive patients without any clinically relevant manifestations. Unexpectedly, however, the percentage of anti-dsDNA antibody positive patients returned to baseline, suggesting that the development of the latter autoantibodies may represent a transitory phenomenon that occurs only during the early phases of treatment. Further studies on larger series are needed to confirm this. However, it is interesting that almost all of the anti-TNF therapy-induced lupus syndromes were reported within the first year of treatment [2
]. Furthermore, the one patient in the present study who developed lupus-like clinical features along with anti-dsDNA antibodies exhibited a spontaneous regression of both clinical symptoms and anti-dsDNA antibodies, even though infliximab treatment were not stopped.
Transient spikes in aCL antibody levels were occasionally reported following bacterial infections in RA patients treated with infliximab [36
]; however, the aCL antibody profile has not previously been systematically studied in relation to anti-TNF therapy [37
]. We observed a significant increase in aCL antibody titres, starting from 30 weeks for IgM antibodies and at 78 weeks for IgG antibodies. However, in most cases the levels did not exceed normal limits, even after 78 weeks, and none of the patients exhibited any clinical feature related to the antiphospholipid syndrome. Longer follow up will clarify whether aCL antibody titres may further increase and whether antiphospholipid related disorders, such as thrombosis, may develop during long-term treatment.
The development of new anti-ENA reactivity, namely anti-SSA(Ro) and SSB(La), has occasionally been reported in previous studies [7
]. About 10% of the patients we studied were positive for anti-SSA(Ro) at baseline (a percentage that is to be expected in RA patients from our country [38
]), and one additional patient developed anti-SSA(Ro) during treatment without associated clinical features. Anti-ENA reactivity other than anti-SSA(Ro) was not detected.
We also analyzed other autoantibodies that have not been thoroughly investigated in RA in relation to anti-TNF-α treatment until now. The most relevant findings pertain to RF and anti-CCP antibodies, because no reactivity at all was found for MPO-ANCAs and PR3-ANCAs or for EMAs.
At baseline RF and anti-CCP antibodies were present in most cases, as expected in patients with severe, erosive RA refractory to conventional DMARD therapy [17
]. Although we did not identify any change in the number of positive patients, in the present study we found a significant decrease in the titres of both anti-CCP antibodies and RF after 30 weeks of infliximab therapy. These findings suggest that serial evaluations of these antibodies could be useful in monitoring the clinical course of RA patients undergoing treatment with infliximab. Decreased production of RF has been reported in association with successful treatment with conventional DMARDs such as methotrexate and gold salts [21
]. However, we observed a different evolution of RF titres with respect to anti-CCP antibody titres during long-term therapy. At 54 and 78 weeks, RF titres exhibited a progressive decrease whereas no decrease was observed for anti-CCP antibody titres, despite the persistence of clinical improvement as indicated by DAS 28.
The decrease in RF titre roughly paralleled DAS 28 values, suggesting that this measure could be regarded as an additional marker of disease activity, although we did not find significant correlations between changes in RF and ACR response. This lack of correlation might be due to a type 2 error related to the small sample size and, at least in part, to the fact that four patients who stopped therapy before 34 weeks because of inefficacy had to be excluded from the analysis. A further prospective study in a larger series of RA patients comparing responders and nonresponders is now in progress.
The mechanisms by which infliximab could lead to a decrease in titres of autoantibodies such as RF and anti-CCP are not understood and any explanation remains speculative. Infliximab therapy has proven to reduce the amount of synovium infiltrating cells, including plasma cells [39
]. Because RF-producing cells are present in inflamed rheumatoid synovium and the local environment may favour synovial RF production [40
], we can speculate that the reduction in inflammatory lymphoplasmacytic infiltrate in rheumatoid synovium will lead to a reduced production of RF. Our data also suggest that generation of RF and anti-CCP antibodies may be controlled in a different manner in RA, because inhibition of RF appears to be more dependent on TNF-α blockade and more persistent than inhibition of anti-CCP antibodies.