Immune reconstitution inflammatory syndrome

Immune reconstitution inflammatory syndrome (IRIS) or immune reconstitution syndrome (IRS) is a condition seen in some cases of AIDS or immunosuppression, in which the immune system begins to recover, but then responds to a previously acquired opportunistic infection with an overwhelming inflammatory response that paradoxically makes the symptoms of infection worse. [Shelburne SA, Visnegarwala F, Darcourt J, Graviss EA, Giordano TP, White Jr AC, Hamill RJ. (2005) Incidence and risk factors for immune reconstitution inflammatory syndrome during highly active antiretroviral therapy. AIDS 19, 399-406.]

The suppression of CD4 T cells by HIV (or by immunosuppressive drugs) causes a decrease in the body's normal response to certain infections. Not only does this make it more difficult to fight the infection; it may mean that a level of infection that would normally produce symptoms is instead undetected (subclinical infection). If the CD4 count rapidly increases (due to effective treatment of HIV, or removal of other causes of immunosuppression), a sudden increase in the inflammatory response produces nonspecific symptoms such as fever, and in some cases a worsening of damage to the infected tissue.

There are two common IRIS scenarios. The first is the “unmasking” of an occult opportunistic infection. The second is the “paradoxical” symptomatic relapse of a prior infection despite microbiologic treatment success. Often in paradoxical IRIS, microbiologic cultures are sterile. In either scenario, there is hypothesized reconstitution of antigen-specific T cell-mediated immunity with activation of the immune system following HIV therapy against persisting antigen, whether present as intact organisms, dead organisms, or debris. [ Bohjanen PR. Boulware DR. Chapter 18: Immune Reconstitution Inflammatory Syndrome. In: Volberding P, Sande MA, Lange J, Greene W. editors. Global HIV/AIDS Medicine. Philadelphia: Elsevier. 2007. 193-205.]

Though these symptoms can be dangerous, they also indicate that the body may now have a better chance to defeat the infection. The best treatment for this condition is unknown. In paradoxical IRIS reactions, the events will usually spontaneously get better with time without any additional therapy. In unmasking IRIS, the most common treatment is to administer an antibiotic or antiviral drugs against the infectious organism. In some severe cases anti-inflammatory medications, such as corticosteroids are needed to suppress inflammation until the infection has been eliminated.

Infections most commonly associated with IRIS include cytomegalovirus, herpes zoster, Mycobacterium avium complex (MAC), Pneumocystis pneumonia, and tuberculosis. AIDS patients are more at risk for IRIS if they are starting HAART for the first time, or if they have recently been treated for an opportunistic infection.

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External links

* [http://www.thebody.com/sfaf/winter05/irs.html The Body]