Magnetic resonance imaging/angiography and transcranial Doppler velocities in sickle cell anemia: results from the SWiTCH trial.

The Stroke With Transfusions Changing to Hydroxyurea (SWiTCH) trial compared standard (transfusions/chelation) to alternative (hydroxyurea/phlebotomy) treatment to prevent recurrent stroke and manage iron overload in children chronically transfused over 7 years before enrollment. Standardized brain magnetic resonance imaging/magnetic resonance angiography (MRA) and transcranial Doppler (TCD) exams were performed at entry and exit, with a central blinded review. A novel MRA vasculopathy grading scale demonstrated frequent severe baseline left/right vessel stenosis (53%/41% ≥Grade 4); 31% had no vessel stenosis on either side. Baseline parenchymal injury was prevalent (85%/79% subcortical, 53%/37% cortical, 50%/35% subcortical and cortical). Most children had low or uninterpretable baseline middle cerebral artery TCD velocities, which were associated with worse stenoses (incidence risk ratio [IRR] = 5.1, P ≤ .0001 and IRR = 4.1, P < .0001) than normal velocities; only 2% to 12% had any conditional/abnormal velocity. Patients with adjudicated stroke (7) and transient ischemic attacks (19 in 11 standard/8 alternative arm subjects) had substantial parenchymal injury/vessel stenosis. At exit, 1 child (alternative arm) had a new silent infarct, and another had worse stenosis. SWiTCH neuroimaging data document severe parenchymal and vascular abnormalities in children with SCA and stroke and support concerns about chronic transfusions lacking effectiveness for preventing progressive cerebrovascular injury. The novel SWiTCH vasculopathy grading scale warrants validation testing and consideration for use in future clinical trials. This trial was registered at www.clinicaltrials.gov as #NCT00122980.

Baseline HIV type 1 coreceptor tropism predicts disease progression.

BACKGROUND: Human immunodeficiency virus type 1 (HIV-1) coreceptor tropism, the ability of the virus to enter cells via CCR5 or CXCR4, is a viral characteristic mediated by the envelope gene. The impact of coreceptor tropism on the natural history of HIV-1 infection has not been fully explored. METHODS: Coreceptor tropism was measured using a recombinant virus single-cycle assay on plasma specimens obtained at baseline from 126 children and adolescents in the Hemophilia Growth and Development Study cohort who were enrolled from 1989 through 1990 and underwent follow-up through 1997. RESULTS: Detectable CXCR4-using virus at baseline was associated with a lower baseline CD4(+) T cell count and a higher plasma HIV-1 RNA level. In addition, it independently predicted a greater decrease in CD4(+) T cell count over time (P<.001) and was associated with a 3.8-fold increased risk of progression to clinical AIDS. CONCLUSIONS: This study demonstrates that coreceptor tropism, as assessed by this single-cycle assay, independently influences the natural history of HIV-1 disease.

HIV-1 pol replication capacity predicts disease progression.

OBJECTIVE: To determine the influence of pol replication capacity on the natural history of HIV-1 infection. DESIGN: Pol replication capacity was measured using a recombinant virus single cycle assay on baseline plasma specimens from subjects enrolled in the Hemophilia Growth and Development Study. SETTING: Children and adolescents with hemophilia and HIV-1 infection were enrolled at multiple sites across the USA into a natural history study. PARTICIPANTS: The Hemophilia Growth and Development Study enrolled 207 HIV-1-infected hemophiliacs between 6 and 19 years of age in 1989 and 1990. Subjects were followed every 6 months through 1997 with pol replication capacity measurements available from 128 of the subjects. MAIN OUTCOME MEASURES: A univariate model defined the relationship between pol replication capacity and HIV-1 RNA and CD4 T-cell number. A random effects model assessed the ability of this measure to predict CD4 T-cell decline over time and a Cox proportional hazards model and Kaplan-Meier analyses defined how it predicts clinical progression. RESULTS: Pol replication capacity measures correlated with baseline HIV-1 RNA, R = 0.189 (P = 0.03) and CD4 T-cell number, -0.197 (P = 0.03). It also independently predicted CD4 T-cell decline over time and progression to AIDS. CONCLUSIONS: This study demonstrates that pol replication capacity independently influences the natural history of HIV-1 infection.