HIV-1 infection is characterised by high levels of virus replication and a progressive loss of immune cells, particularly CD4+ T lymphocytes. Highly active antiretrovial therapy (HAART) for HIV-1 infection results in profound suppression of viral replication, a substantial increase in CD4+ T lymphocytes and a decrease in morbidity and mortality. The primary source of T lymphocytes in early human development is the thymus. Recently, it has been demonstrated that the thymus remains functional thro ....HIV-1 infection is characterised by high levels of virus replication and a progressive loss of immune cells, particularly CD4+ T lymphocytes. Highly active antiretrovial therapy (HAART) for HIV-1 infection results in profound suppression of viral replication, a substantial increase in CD4+ T lymphocytes and a decrease in morbidity and mortality. The primary source of T lymphocytes in early human development is the thymus. Recently, it has been demonstrated that the thymus remains functional throughout adult life. The role of the thymus in HIV-1 infection remains controversial. Studies of the role of the thymus in HIV-1-infected individuals has been limited by the lack of a marker of thymic function in vivo. We have recently developed a novel assay to quantify cells of recent thymic origin by taking advantage of certain molecular events that occur in the thymus during the production of new T lymphocytes. This molecular event creates a circular piece of DNA, called a T-cell receptor excision circles (TREC). TREC concentration in the periphery will increase with an increase in thymic output but will reduce in the presence of T cell proliferation or cell death. In order to determine the contribution of the thymus to immune reconstitution following HAART, we plan to study the dynamics of thymus function in HIV-1 infection by measuring TREC and T cell turnover in HIV-1 infection prior to and following HAART. In a subgroup of individuals, more commonly seen following treatment of HIV-1 infection in children, there is an increase in CD4+ T lymphocytes in the absence of a significant reduction in viral suppression. The role of the thymus in this unique subset of individuals will be studied.Read moreRead less