[Infectious complications of biological therapy]

Biological treatment represents a significant progress in the therapy of many serious diseases. Together with the growing knowledge of pathophysiology and subsequent development of new therapeutic agents, this progress will definitely lead to further expansion of biologics. Since biologics interfere with many mechanisms of host defence, which may sometimes be compromised by them, increased risk of infectious complications must be taken into account. Patients treated with biologics are prone to classical virulent infections (e.g. listeriosis, legionellosis and tuberculosis) and opportunistic infections such as progressive multifocal leukoencephalopathy. Furthermore, suppression of the immune response that is caused by biologics may lead to reactivation of latent infections such as tuberculosis or viral hepatitis B. Therefore, the knowledge of basic mechanisms by which biologics modify the immune response is important for a rapid clinical diagnosis of possible aetiology of infectious complications.