Predictors of immunological failure after initial response to highly active antiretroviral therapy in HIV-1-infected adults: a EuroSIDA study.

Background: Factors that determine the immunological response to highly active antiretroviral therapy (HAART) are poorly defined.
Objective: Our aim was to investigate predictors of immunological failure after initial CD4(+) response.
Methods: Data were from EuroSIDA, a prospective, international, observational human immunodeficiency virus (HIV) type 1 cohort.
Results: Of 2347 patients with an increase in CD4(+) cell count >or=100 cells/microL within 6-12 months of the initiation of HAART, 550 (23%) subsequently experienced immunological failure (CD4(+) count less than or equal to the pre-HAART value). The incidence of failure was 11.6 incidences/100 person-years of follow-up (95% confidence interval [CI], 10.2-13.4) during the first 12 months and decreased significantly over time (P<.0001). Independent predictors of immunological failure were pre-HAART CD4(+) cell count (per 50% higher; relative hazard [RH], 2.05; 95% CI, 1.83-2.31; P<.0001), time-updated virus load (per 1 log(10) higher; RH, 1.77; 95% CI, 1.64-1.92; P<.0001), and HIV-1 risk behavior (P=.047 for a global comparison of risk groups).
Conclusion: The risk of immunological failure in patients with an immunological response to HAART diminishes with a longer time receiving treatment and is associated with pretreatment CD4(+) cell count, ongoing viral replication, and intravenous drug use.