Immunologic failure despite suppressive antiretroviral therapy is related to activation and turnover of memory CD4 cells.

Background: Failure to normalize CD4(+) T-cell numbers despite effective antiretroviral therapy is an important problem in human immunodeficiency virus (HIV) infection.

Methods: To evaluate potential determinants of immune failure in this setting, we performed a comprehensive immunophenotypic characterization of patients with immune failure despite HIV suppression, persons who experienced CD4(+) T-cell restoration with therapy, and healthy controls.

Results: Profound depletion of all CD4(+) T-cell maturation subsets and depletion of naive CD8(+) T cells was found in immune failure, implying failure of T-cell production/expansion. In immune failure, both CD4(+) and CD8(+) cells were activated but only memory CD4(+) cells were cycling at increased frequency. This may be the consequence of inflammation induced by in vivo exposure to microbial products, as soluble levels of the endotoxin receptor CD14(+) and interleukin 6 were elevated in immune failure. In multivariate analyses, naive T-cell depletion, phenotypic activation (CD38(+) and HLA-DR expression), cycling of memory CD4(+) T cells, and levels of soluble CD14 (sCD14) distinguished immune failure from immune success, even when adjusted for CD4(+) T-cell nadir, age at treatment initiation, and other clinical indices.

Conclusions: Immune activation that appears related to exposure to microbial elements distinguishes immune failure from immune success in treated HIV infection.