• Jean-Daniel Lelièvre, Giovanna Melica, Emmanuel Itti, Christine Lacabaratz, Sandra Rozlan, Aurélie Wiedemann, Rémi Cheynier, Michel Meignan, Rodolphe Thiebaut, and Yves Levy.
• INSERM, Unite U955, Creteil, France. jean-daniel.lelievre@hmn.aphp.fr
• J. Acquir. Immune Defic. Syndr. 2012 Sep 1; 61 (1): 56-63.

BackgroundThe role of the thymus in the depletion or restoration of T-cell pool in HIV infection is still debatable. Studies are hampered by the lack of valuable tools to investigate thymic activity.MethodsWe have evaluated thymic activity using (18)F-fluorodeoxyglucose-positron emission tomography/computed tomography and molecular and phenotypic analyses of thymic precursors. Longitudinal analyses were performed in HIV-infected patients either treatment naive with indication to initiate combination antiretroviral therapy (c-ART) (n = 11) or stable under c-ART (n = 9).ResultsThymic standardized uptake value was significantly lower in c-ART-treated patients as compared with historical age-matched HIV-negative controls. In c-ART-naive patients, baseline thymic standardized uptake value correlated with T-cell repector excision circle levels and naive CD4+ T cells. These patients exhibited a high metabolic lymph node activity positively correlated to the percentage of activated HLA-DR+CD38+ T cells. Basal metabolic thymic activity predicts the gain in CD4+ T cells after c-ART initiation. A decrease of thymic activity, which paralleled circulating plasma IL-7 levels, was noted after c-ART initiation.DiscussionA metabolic thymic activity is detectable in c-ART naive and correlates with indirect phenotypic and molecular markers of thymic output. This activity may participate to the pool of peripheral naive CD4+ T cells and predicts the magnitude of T-cell reconstitution under treatment.

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