IntroductionMethodsPatientsIsolation of peripheral blood mono—nuclearT cell subsets and plasmaChest computed tomographic scansMeasurement of T cell receptor rearrangementMeasurement of T cell productionTelomere restriction fragment length meas—ure—mentStatistical analysisResultsLymphocyte subsetsThymic indexT cell receptor rearrangement excision circlesTelomere restriction fragment lengthT lymphocyte production ratesRelationship frequencies for thymic index,DiscussionAcknowledgementsReferencesPoor CD4 T cell restoration after suppression of HIV-1replication may re¯ect lower thymic functionLucileÂia Teixeiraa, Hernan Valdeza, Joseph M. McCuneb,c,e,Richard A. Koupf, Andrew D. Badleyi, Marc K. Hellersteinc,g,Laura A. Napolitanob, Daniel C. Douekf, Georgina Mbisai,Steven Deeksc, Jeffrey M. Harrisb, Jason D. Barbourb, Barry H. Grossh,Isaac R. Francish, Robert Halvorsend, Robert AsaadaandMichael M. LedermanaObjective: To characterize immune phenotype and thymic function in HIV-1-infectedadults with excellent virologic and poor immunologic responses to highly activeantiretroviral therapy (HAART).Methods: Cross-sectional study of patients with CD4 T cell rises of > 200 3 106cells/l (CD4 responders; n  10) or , 100 3 106cells/l (poor responders; n  12) in the ®rstyear of therapy.Results: Poor responders were older than CD4 responders (46 versus 38 years;P , 0.01) and, before HAART, had higher CD4 cell counts (170 versus 35 3 106cells/l; P  0.11) and CD8 cell counts (780 versus 536 3 106cells/l;P 0.02). After amedian of 160 weeks of therapy, CD4 responders had more circulating naivephenotype (CD45CD62L) CD4 cells (227 versus 44 3 106cells/l;P 0.001) andnaive phenotype CD8 cells (487 versus 174 3 106cells/l;P 0.004) than did poorresponders (after 130 weeks). Computed tomographic scans showed minimal thymictissue in 11/12 poor responders and abundant tissue in 7/10 responders (P  0.006).Poor responders had fewer CD4 cells containing T cell receptor excision circles(TREC) compared with CD4 responders (2.12 versus 27.5 3 106cells/l;P 0.004)and had shorter telomeres in CD4 cells (3.8 versus 5.3 kb;P 0.05). Metaboliclabeling studies with deuterated glucose indicated that the lower frequency of TREC-containing lymphocytes in poor responders was not caused by accelerated prolifera-tion kinetics.Conclusion: Poor CD4 T cell increases observed in some patients with good virologicresponse to HAART may be caused by failure of thymic T cell production.& 2001 Lippincott Williams & WilkinsAIDS 2001, 15:1749±1756Keywords: AIDS, highly active antiretroviral therapy, HAART, CD4, thymus,T cell reconstitutionFrom theaDivision of Infectious Diseases and the Center for AIDS Research, Case Western Reserve University School ofMedicine and University Hospitals of Cleveland, Ohio, thebGladstone Institute of Virology and Immunology, thecDepartmentof Medicine and thedDepartment of Radiology, San Francisco General Hospital and theeDepartment of Microbiology andImmunology, University of California at San Francisco, San Francisco, California, thefDepartment of Medicine, University ofTexas Southwestern Medical Center, Dallas, Texas, thegDepartment of Nutritional Sciences, University of California at Berkeley,Berkeley, California, thehDepartment of Radiology, University of Michigan, Ann Arbor, Michigan, USA and theiOttawa HospitalResearch Institute, Department of Biochemistry, Microbiology and Immunology, University of Ottawa and Division of InfectiousDiseases Ottawa Hospital, Ottawa, Ontario, Canada.Requests for reprints to Dr M. M. Lederman, Division of Infectious Diseases, University Hospitals of Cleveland, Foley Building,2061 Cornell Road, Cleveland, Ohio 44106, USA.Received: 8 December 2000; revised: 19 March 2001; accepted: 2 May 2001.ISSN 0269-9370 & 2001 Lippincott Williams & Wilkins1749IntroductionSuppression of viral replication after administration ofpotent antiretroviral therapy is associated with quantita-tive and qualitative immune enhancement [1,2], de-creased rates of opportunistic infections [3,4] anddecreased mortality [5±7]. In patients with relativelyadvanced disease, a biphasic pattern of CD4 and CD8T cell recovery has been observed after the initiation ofantiretroviral therapy. During the ®rst 4 to 8 weeks,rises in CD4 and CD8 T lymphocytes of both naiveand memory phenotypes have been observed [1,8±11].This initial increase is likely a result, at least in part, ofredistribution of sequestered cells into the circulation[12,13]. It is followed by a more gradual second-phaseincrease in CD4 T cells comprised mainly of naivephenotype cells [1,2,10,14].In approximately 8±17% of patients, suppression ofHIV-1 replication is not accompanied by an increase incirculating CD4 T cells [11,15±17]. Such patients mayremain at increased risk for opportunistic infections[15] and have higher risk for progression to AIDS ordeath [17]. Although the factors responsible for thesediscordant responses are not well understood, themagnitude of CD4 T cell restoration after highly activeantiretroviral therapy (HAART) has been correlatedwith the rate of pre-therapy CD4 T cell decline,baseline plasma viremia, total and naive-phenotypeCD4 T cell counts, and the ®rst-phase decay in plasmaHIV-1 RNA levels [2,10,16,18].We hypothesized that failure to restore circulatingCD4 T cells after initiation of effective HAART maybe caused in part by de®ciencies in T cell production,particularly from the thymus. To explore this possibi-lity, a cross-sectional study examined several indices ofT cell production in patients with sustained virologicresponses who had received at least 12 months ofHAART, comparing those with a ®rst year post-HAART CD4 T cell gain of > 200 3 106cells/l(CD4 responders) with those with a gain of, 100 3 106cells/l (poor responders).MethodsPatientsPatients were attending the John T. Carey SpecialImmunology Unit at University Hospitals of Cleve-land, Ohio and the San Francisco General Hospital,San Francisco, California. To be eligible for studyparticipation, patients were HIV-1-infected adults whohad been receiving HAART for at least 12 months,had started HAART (at least three antiretroviral drugs)with , 500 3 106cells/l CD4 cells and had sustainedplasma HIV-1 RNA levels , 400 copies/ml for at least12 months. Poor responders were those with a CD4 Tcell rise of , 100 3 106cells/l over the ®rst year ofeffective HAART; CD4 responders were those withincreases of > 200 3