[Biologic therapy and infections]

Biologic therapy is an important therapeutic arsenal in rheumatic diseases. Anti-TNF therapies affect host defenses against infections, since TNF mediates inflammation and modulates cellular immune responses. Cases of tuberculosis have been observed in patients treated with TNF antagonists, mainly due to the presence of latent or "dormant" tuberculosis infection (LTB1). Other microorganisms responsible for the infectious complications associated with biologic therapy are generally intracellular pathogens or pathogens that commonly exist in a chronic latent state: Mycobacterium sp., Listeria monocytogenes, Legionella sp., Brucella sp., toxoplasmosis and deep mycoses, that are normally held in control by cell-mediated immunity. Diagnosis may require a high index of suspicion and prompt acquisition of appropriate tissue samples for microscopic examination and microbiologic culture. Patients who develop a new infection while undergoing treatment with biologic therapy should be monitored closely. Administration of anti-TNF should be discontinued if a patient develops a serious infection or sepsis. The relationship between TNF-inhibition and infection risk remains unclear, many of the serious infections have occurred in patients on concomitant immunosuppressive therapy that, in addition to severe rheumatic diseases, could predispose them to infections, and most reports present low level of evidence. Nevertheless, prompt diagnosis and empiric therapy infections is necessary to prevent mortality.