Prolonged CD4+ cell/virus load discordance during treatment with protease inhibitor-based highly active antiretroviral therapy: immune response and viral control.

Mechanisms that underly discordant CD4+ cell/virus load (VL) responses in patients who receive highly active antiretroviral therapy (HAART) were studied in 30 human immunodeficiency virus (HIV)-positive patients, in 3 groups. Discordant responders maintained CD4+ cell levels >200/mm(3) with stable or increasing trend, despite sustained VLs of 500-5000 copies/mL, for >2 years. Treatment-success patients had CD4+ cell counts >200/mm(3) with stable or increasing trend and VLs <50 copies/mL, for >2 years. Treatment-failure patients initially responded to HAART, followed by decreasing CD4+ cell counts and increasing VLs. Interferon-gamma production to gag and noncytolytic CD8+ cell suppressive activity were greater in discordant responders. Cellular activation was greatest in patients with treatment failure. All discordant responders had non-syncytium-inducing (CCR5-tropic) viruses. Viruses from discordant responders and from patients with treatment failure had extensive resistance mutations; discordant responders had significantly lower viral replication capacities. These findings suggest that discordant responses may be related to enhanced HIV-directed immune responses, diminished cellular activation, decreased viral replication capacity, and preservation of non-syncytium-inducing virus strains.