An Ad5-vectored HIV-1 vaccine elicits cell-mediated immunity but does not affect disease progression in HIV-1-infected male subjects: results from a randomized placebo-controlled trial (the Step study)

Abstract

Background: The Step study was a randomized trial to determine whether an adenovirus type 5 (Ad5) vector vaccine, which elicits T cell immunity, can lead to control of human immunodeficiency virus (HIV) replication in participants who became HIV-infected after vaccination.

Methods: We evaluated the effect of the vaccine on trends in HIV viral load, CD4+ T cell counts, time to initiation of antiretroviral therapy (ART), and AIDS-free survival in 87 male participants who became infected with HIV during the Step study and who had a median of 24 months of post-infection follow-up.

Results: There was no overall effect of vaccine on mean log(10) viral load (estimated difference between groups, -0.11; P = .47). In a subset of subjects with protective HLA types (B27, B57, B58), mean HIV-1 RNA level over time was lower among vaccine recipients. There was no significant difference in CD4+ T cell counts, time to ART initiation, or in AIDS-free survival between HIV-1-infected subjects who received vaccine versus those who received placebo.

Conclusions: HIV RNA levels, CD4+ T cell counts, time to initiation of ART, and AIDS-free survival were similar in vaccine and placebo recipients. There may have been a favorable effect of vaccine on HIV-1 RNA levels in participants with HLA types associated with better control of HIV-1.

Trial registration: ClinicalTrials.gov NCT00095576.

Figures

Figure 1.

Pre-antiretroviral therapy log10 viral load measurements at each post-infection visit. Black points are observed values, and red points are averages of 10 imputed values. The red curve shows the mean value at each time point (MI mean), which was estimated using both the observed and imputed data. The blue curve shows the mean value as estimated using the weighted generalized estimating equation model (WGEE mean).

Figure 2.

Pre-antiretroviral therapy CD4+ cell count measurements at each post-infection visit. Black points are observed values, and red points are averages of 10 imputed values. The red curve shows the mean value at each time point, which was estimated using both the observed and imputed data. The blue curve shows the mean as estimated using the weighted generalized estimating equation model.

Figure 3.

Kaplan-Meier curves for the time between human immunodeficiency virus infection diagnosis and initiation of antiretroviral therapy (ART).