Different profiles of immune reconstitution in children and adults with HIV-infection after highly active antiretroviral therapy

Background: Recent advances in characterizing the immune recovery of HIV-1-infected people have highlighted the importance of the thymus for peripheral T-cell diversity and function. The aim of this study was to investigate differences in immune reconstitution profiles after highly active antiretroviral therapy ( HAART) between HIV-children and adults. Methods: HIV patients were grouped according to their previous clinical and immunological status: 9 HIV-Reconstituting-adults (HIV-Rec-adults) and 10 HIV-Reconstituting-children (HIV-Rec-children) on HAART with viral load (VL) <= 400 copies/ml and CD4(+) >= 500 cells/mu L at least during 6 months before the study and CD4(+) <= 300 cells/mu L anytime before. Fifteen healthy-adults and 20 healthy-children ( control subjects) were used to calculate Z-score values to unify value scales between children and adults to make them comparable. Results: HIV-Rec-children had higher T-cell receptor excision circles (TREC) and lower interleukin (IL)-7 levels than HIV-Rec-adults ( p < 0.05). When we analyzed Z-score values, HIV-Rec-children had higher TREC Z-score levels ( p = 0.03) than HIV-Rec-adults but similar IL-7 Z-score levels. Regarding T-cell subsets, HIV-Rec-children had higher nave CD4(+) (CD4(+) CD45RA (hi+)CD27(+)), naive CD8(+) (CD8(+) CD45RA (hi+)CD27(+)), and memory CD8(+) (CD8+ CD45RO(+)) cells/mu l than HIV-Rec-adults, but similar memory CD4(+) (CD4(+) CD45RO(+)) counts. HIV-Rec-children had lower naive CD8(+) Z-score values than HIV-Rec-adults ( p = 0.05). Conclusion: Our data suggest that HIV-Rec-children had better thymic function than HIV-Rec-adults and this fact affects the peripheral T-cell subsets. Thus, T-cell recovery after HAART in HIV-Rec-adults could be the consequence of antigen-independent peripheral T-cell expansion while in HIV-Rec-children thymic output could play a predominant role in immune reconstitution.