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Infliximab partially impairs the anti-Mycobacterium tuberculosis immune responses of severe psoriasis patients with positive tuberculin skin-test


  • Financial support
    This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (contracts # 05/57761-7 and 05/60075-8), the Netherlands Leprosy Relief Foundation (NLR) and the European Commission. GB and AJSD are senior researchers of the Conselho Nacional para o Desenvolvimento Científico e Tecnológico.

  • Conflict of interest
    All authors declare no conflicts of interest.

G. Benard, MD, PhD.


Background  Infliximab and etarnecept are now widely used for treating severe psoriasis. However, these drugs, especially infliximab, increased the risk of tuberculosis reactivation. Surprisingly, epidemiological data suggest that the tuberculosis rate in patients taking infliximab in São Paulo State, Brazil, is similar to that of some developed, non-endemic countries.

Objective  The aim of this study was to better understand the effect of infliximab on Mycobacterium tuberculosis (Mtb) immune responses of psoriasis patients in an endemic setting (Brazil).

Methods  We evaluated the tuberculosis-specific immune responses of severe psoriasis patients and healthy individuals, both tuberculin skin test (TST) positive, in the presence/absence of infliximab. Patients had untreated severe psoriasis, no co-morbidities affecting the immune responses and a TST >10 mm. Healthy TST+ (>10 mm) individuals were evaluated in parallel. PBMC cultures from both groups were stimulated with different Mycobacterium tuberculosis (Mtb) antigens (ESAT-6, 85B and Mtb lysate) and phytohemagglutinin, with or without infliximab (5 μg/mL). Parameters evaluated were TNF-α, IFN-γ and IL-10 secretion by ELISA, overnight IFN-γ ELISpot and lymphocyte proliferative response (LPR).

Results  Infliximab almost abolished TNF-α detection in PBMC supernatants of both groups. It also significantly reduced the LPR to phytohemagglutinin and the Mtb antigens as well as the IFN-γ levels secreted into day 5 supernatants in both groups. There was no concomitant exaggerated IL-10 secretion that could account for the decreases in these responses. ELISpot showed that, contrasting with the central-memory responses above, infliximab did not affect effector-memory INF-γ-releasing T-cell numbers.

Conclusions  Infliximab affected some, but not all aspects of the in vitro antituberculosis immune responses tested. The preserved effector-memory responses, putatively related to exposure to environmental mycobacteria, may help to explain the lower than expected susceptibility to tuberculosis reactivation in our setting.