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Summary 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 ≥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.

SUMMARY Previous studies have shown a slow recovery of naive CD4+ T cell counts after anti-retroviral therapy in HIV-1-infected adults, which is in accordance with thymus atrophy after puberty. Here we investigate whether or not different patterns of naive CD4+ and CD8+ T cell repopulation are present in adult and child patients undergoing anti-retroviral treatment. Thus, 25 adults under highly active anti-retroviral therapy and 10 children under combined anti-retroviral therapy were retrospectively analysed for T cell subpopulations at baseline (T0) and around week 12 (T1) and week 24 (T2) of anti-retroviral treatment. Mean serum HIV-1 RNA levels dropped in both groups. Recovery of T cells in adults was characterized by a heterogeneous response between patients, with only 44% of them increasing their naive CD4+ and CD8+ T cell counts at T1, and changes in mean total CD4+ T cells were mainly shaped by memory cells. Otherwise, children were characterized by an early increase in naive T cells. Thus, at T1, all children analysed had a strong rise in CD4+ (from 389 ± 116 to 569 ± 121 cells/μl; P