Highly active antiretroviral therapy (HAART) suppresses viral replication and augments CD4 T cell counts. HAART-associated immune restoration is often difficult to predict. We verified whether increases in CD4 cells, and particularly in cells of the naive phenotype, would be associated in HAART-treated children with thymic volume. Long-term immune reconstitution is significantly better in children with bigger thymuses at the initiation of HAART. Thymic volume has a strong predictive value for the immunological effect of HAART.

Highly active antiretroviral therapy (HAART) suppresses viral replication and augments CD4 T cells in HIV-infected individuals. The virological effect of HAART is highly reproducible; in contrast, the degree of immune restoration is variable among different patients and is difficult to predict [1, 2]. CD4 T cells include both memory (CD4+ CD45RO+) and naive (CD4+ CD45RA+ CD62L+) subpopulations. In HAART-treated adults, increases in CD4 T cells are for a long period of time supported by the redistribution of memory lymphocytes, whereas early increases in naive lymphocytes are seen in paediatric patients [2, 3]. Because thymic maturation and selection lead to the generation of naive T cells, we verified whether the degree of HAART-associated immune reconstitution was associated with thymic volume. We report here that immune reconstitution after 3 years of therapy is significantly better in children with bigger thymuses at the initiation of HAART. Thymic volume thus has a strong predictive value for the immunological effect of HAART.