Failure of CD4+ T-cell Recovery upon Virally-Effective cART: an Enduring Gap in the Understanding of HIV+ Immunological non-Responders

The introduction of cART in the treatment of HIV infection has significantly decreased morbidity and mortality by inducing suppression of viral replication and recovery of CD4+ T-cell counts. How- ever, about 30% of HIV-infected individuals fail to achieve normalization of CD4+ T-cell counts, de- spite antiretroviral therapy and complete suppression of the HIV load: these patients are referred to as "immunological non-responders". Several studies have shown an increased risk of clinical pro- gression to both AIDS and non-AIDS events as well as a higher mortality in these patients. The pathogenetic factors underlying this condition are multiple and none of these alone can exhaustive- ly explain the mechanism of incomplete immune reconstitution. In light of this, the purpose of the present review is to: i) describe in detail the pathogenetic mechanisms that contribute to scarce immune recovery; ii) discuss the higher morbidity and mortality which feature such a condition; iii) take stock of therapeutic strategies used in recent years for these patients.