Thymic function in severely immunodeficient HIV type 1-infected patients receiving stable and effective antiretroviral therapy.
The role of the thymus in long-term immune reconstitution has not been addressed in HIV patients who were severely immunodeficient prior to successful treatment with combination antiretroviral therapy (ART). Adult HIV-1 patients (n = 78) with nadir CD4+ T cell counts <100 T cells/microl, at least 12 months on ART and 6 months of complete viral suppression (<50 HIV RNA copies/ml) were selected from a patient database. The cohort was divided according to current CD4+ T cell counts and patients from the lowest (n = 15) and highest (n = 12) tertiles were studied. Thymic volume was assessed by spiral computed tomography. Naive (CD45RA+CD62L+) and replicating (Ki67+) T cells were quantitated by flow cytometry, T cell receptor excision circles (TREC) were assessed by real-time PCR, and serum IL-7 and testosterone by immunoassay. Patients with low CD4+ T cell counts had smaller thymuses [0(0-5.3) vs. 3.5(0-15.6) cm(3), p = 0.04] and were more likely to have no detectable thymus. They had similar proportions of replicating cells, but fewer naive CD4+ and CD8+ T cells and less TREC in CD4+ and CD8+ T cells/ml of blood than patients with high CD4+ T cell counts. However, some patients with no detectable thymus had high numbers of naive and TREC-bearing T cells. Thus, the recovery of CD4+ T cells in severely immunodeficient HIV patients with a virological response to ART is probably limited by thymic function. However, the data are consistent with extrathymic T cell production contributing to the naive T cell pool in some patients.
Fernandez
Sonia
S
School of Surgery and Pathology, University of Western Australia, Department of Clinical Immunology and Biochemical Genetics, Royal Perth Hospital, The University of Melbourne, Melbourne, Australia.
Nolan
Richard C
RC
Price
Patricia
P
Krueger
Romano
R
Wood
Christopher
C
Cameron
David
D
Solomon
Ajantha
A
Lewin
Sharon R
SR
French
Martyn A
MA
D000328:Adult; D000368:Aged; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D018791:CD4 Lymphocyte Count; D005260:Female; D015658:HIV Infections / Q000188:drug therapy* / Q000503:physiopathology; D015497:HIV-1 / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012367:RNA, Viral; D016176:T-Lymphocyte Subsets; D013950:Thymus Gland / Q000503:physiopathology*; D019562:Viral Load
D019380:Anti-HIV Agents; D012367:RNA, Viral