Central nervous system immune reconstitution disease in acquired immunodeficiency syndrome patients receiving highly active antiretroviral treatment

Highly active antiretroviral therapy (HAART)-induced immune restoration has been very beneficial for acquired immunodeficiency syndrome (AIDS) patients. In rare instances, HAART may induce a paradoxical clinical deterioration due to an immune reconstitution inflammatory syndrome (IRIS). This syndrome has been described with a wide variety of systemic infections and, in the central nervous system, with Cryptococcus neoformans infection, cytomegalovirus retinitis, and progressive multifocal leukoencephalopathy (PML). The authors have examined brain tissue in eight cases of IRIS: two autopsy cases and three biopsy cases of HIV encephalitis with IRIS and one autopsy case and two biopsy cases of PML with IRIS. All the patients presented with clinical deterioration following initiation of HAART and imaging showed contrast enhancement of the lesions. The symptoms regressed in four patients whereas the other four patients died. Neuropathological examination revealed severe inflammatory and demyelinating lesions with marked intraparenchymal and perivascular infiltration by macrophages and T lymphocytes. In some cases abundant viral proliferation was identified by immunocytochemistry or in situ hybridization, but in others the infectious agent could only be detected using PCR. T lymphocytes were predominantly CD8(+). In those cases with the more favorable course, inflammation was less severe with marked macrophage activation and a number of CD4(+) lymphocytes; in contrast, in the lethal cases inflammation was severe and mostly composed of CD8(+) cytotoxic lymphocytes. We conclude that HAART-induced paradoxical aggravation of HIV encephalitis or AIDS-related PML due to IRIS is reversible in most cases but may be lethal in others. In fatal cases, fulminant viral infection and/or acute perivenous leukoencephalitis may result from a dysregulation of the CD8(+)/CD4(+) T-cell balance.