Thymus volume correlates with the progression of vertical HIV infection

Background: The thymus is the organ responsible for the maturation and sele ction of T lymphocytes and is thus pivotal in allowing the development of a functional immune system. Because in HIV infection cell-mediated immune re sponses are severely impaired, we studied the role of thymus in the control of the progression of HIV infection to AIDS. Methods: Thymic volume was analysed by magnetic resonance imaging in 31 ver tically HIV-infected children. Plasma HIV viral load and phenotypic and fun ctional cellular immunity-defining parameters were examined in the same pat ients. Results: Thymic volume was not correlated with age or nutritional status; t hymic volume was nevertheless correlated with CD4 T-lymphocyte counts and w ith the percentage and absolute number of CD45RA+CD62L+ (naive) T lymphocyt es. In addition, the ability of peripheral blood mononuclear cells to proli ferate upon tetanus stimulation was directly proportional to thymic volume. Finally, a negative correlation was detected between thymic volume and HIV viral load. Conclusion: Because low HIV plasma viraemia and preserved immune function a re favourable prognostic indices in HIV disease, these data indicate that a n immunological, thymic-dependent control of the progression of HIV infecti on might be possible, at least in vertically transmitted HIV infection. (C) 1999 Lippincott Williams & Wilkins.