Immune reconstitution inflammatory syndrome: immune restoration disease 20 years on

Restoration of immune responses against opportunistic pathogens after commencing antiretroviral therapy (ART) may cause immune restoration disease (IRD) in about 10%-40% of HIV patients with low CD4(+) T-cell counts and usually presents clinically as a type of immune reconstitution inflammatory syndrome (IRIS). IRIS may be associated with many different opportunistic pathogens, but types associated with Mycobacterium tuberculosis, BCG, cryptococci, JC polyomavirus (the cause of progressive multifocal leukoencephalopathy [PML]), hepatitis C virus and hepatitis B virus infection are the most informative about disease pathogenesis and management. A CD4(+) T-cell count of < 50/μL and a high pathogen load are the most commonly identified risk factors for IRIS. Recovery of pathogen-specific T-cell responses and perturbations of innate immune responses before and after ART appear to cause immunopathological abnormality in tissues infected by the pathogen. Prevention of IRIS may be influenced by the timing of ART: The risk of tuberculosis (TB)-associated-IRIS can be reduced by commencing ART after 8 weeks of TB treatment, but rates of AIDS or death are lower if ART is commenced during the first 4 weeks of TB treatment. Outcomes for patients with HIV and treated cryptococcal or TB meningitis may be improved by deferring ART until the opportunistic infection is fully suppressed, but data are inadequate. As ART is currently the only effective treatment for PML in patients with HIV, PML-associated IRIS cannot be prevented by manipulating the timing of ART. A greater understanding of the immunopathogenesis of IRIS may lead to targeted therapies.