Elevated CD8 counts during HAART are associated with HIV virologic treatment failure

To evaluate whether elevated CD8 counts are associated with increased risk of virologic treatment failure in HIV-infected individuals.

Retrospective cohort study.

US Military HIV Natural History Study participants who initiated highly active antiretroviral therapy (HAART) in 1996-2008 had 6- and 12-month post-HAART HIV RNA <400 copies per milliliter, ≥ 2 subsequent HIV viral loads and a baseline CD8 count were eligible (n = 817). Baseline was 12 months after the start of HAART, virologic failure (VF) was defined as confirmed HIV RNA ≥ 400 copies per milliliter, and CD8 counts ≥ 1200 cells per cubic millimeter were considered elevated. Cox models were used to examine the effect of baseline and time-updated CD8 counts on VF.

There were 216 failures for a rate of 5.6 per 100 person-years [95% confidence interval (CI): 4.9 to 6.4]. Among those initiating HAART in 2000-2008, the participants with elevated baseline CD8 counts had significantly greater risk of VF compared with those with baseline CD8 counts ≤ 600 cells per cubic millimeter [hazard ratio (HR) = 2.68, 95% CI: 1.13 to 6.35]. The participants with elevated CD8 counts at >20% of previous 6-month follow-up visits had a greater risk of failure at the current visit than those who did not (HR = 1.53, 95% CI: 1.14 to 2.06). Those with CD8 counts that increased after the start of HAART had a greater risk of failure than those with CD8 counts that decreased or remained the same (HR = 1.59, 95% CI: 1.19 to 2.13).

Initial or serial elevated CD8 counts while on HAART or an increase in CD8 counts from HAART initiation may be early warnings for future treatment failure.