Increased thymic output after initiation of antiretroviral therapy in human immunodeficiency virus type 1-infected children in the Paediatric European Network for Treatment of AIDS (PENTA) 5 trial

To investigate the thymic contribution to immune reconstitution during antiretroviral therapy (ART), T cell receptor gene rearrangement excision circles (TRECs) were measured in peripheral blood mononuclear cells (PBMC) and CD4 cells from 33 human immunodeficiency virus (HIV) type 1-infected children monitored for 96 weeks after ART initiation. Baseline TREC levels were associated positively with baseline CD4 cell percentage and inversely with age and HIV-1 RNA load. During therapy, TREC level changes in PBMC and CD4 cells were fairly comparable. TREC level changes were inversely related to baseline CD4 cell percentage and positively associated with CD4 cell percentage increases, the main source being naive CD4 cells. TREC changes were independent of age and baseline HIV-1 RNA load; however, HIV-1 suppression was independently associated with smaller TREC changes. Thymic output appears to be the main source of CD4 cell repopulation in children receiving ART. Recovery of thymic function is independent of age and influenced by the status of peripheral CD4 cell depletion and HIV-1 suppression.