Changes in thymus volume in adult HIV-infected patients under HAART: correlation with the T-cell repopulation

Abstract

An important thymus role has been suggested in T-cell repopulation after HAART in adult HIV-1 infected patients. Thymus volume increase after treatment has been described in HIV-1 infected children but not in adult patients. The objective of this work was to evaluate the effect of HAART on the thymic volume of adult HIV-1 infected patients and its relation with the T-cell repopulation. Twenty-one adult patients following 24 weeks under HAART were included in the study. All patients underwent a thoracic computed tomography (CT) evaluation for the measurement of thymic volumes at weeks 0, 12 and 24. Baseline thymus volume showed a significant correlation with the patient's age. Thymic volume significantly increased after 24 weeks of HAART. Besides, a significant correlation between changes in the thymus volume and changes in both total and naïve CD4+ cell counts was found. Only patients with increases > or =100 CD4+ cell counts after treatment significantly increased the thymic volume. These data show the first evidence of an early change in thymic volume of adult HIV-1 infected patients under HAART. This increase was related to the rise of both total and naïve CD4+ cell counts suggesting a functional role of thymic volume increase.

Fig. 1

Baseline correlation of the thymic volume measured by CT and the age of the patients. r = −0.769, P < 0.0001, Spearman test.

Fig. 2

Visualization of a thymus slice of two adult HIV-1 infected patients by computed tomography (CT). One younger patient (aged 38) with a high score before and during the follow up (a, b), and an older one (aged 60) with a low score during the complete follow up (c, d). CT scans of theses two patients are represented at baseline (a, c) and at week 24 of HAART (b, d). A global thoracic area is shown for the young patient and an enhanced and amplified CT scan at the level of pulmonary artery is shown for the 60-year-old-man. The thymus is indicated by arrows at the top centre of each frame. (e) shows how to outline the thymus corresponding area (the functional thymus) using the cursor. Fat infiltration within thymic fossae is obviated. Afterwards the computer scans the highlighted area. CT slices corresponded to the aortic arch area in both patients at each time point.

Fig. 3

Correlation of basal increase of thymus volume versus baseline and the increase in CD4+ cell counts at week 24. Data has been expressed as log₁₀ for calculations. Spearman test.

Fig. 4

Evolution of thymus volume of the patients. Patients were classified for either having experienced an increase ≥100 CD4+ cells/µl at week 24 (d) or <100 CD4+ cells/µl (s). Circles represent thymus volume of each patient, and dark line the median of the patients at each time point. Friedman test; *P = 0·002; Wilcoxon matched pair signed rank test, P = 0·005 versus week 12 and P = 0·009 versus week 24.