MAJOR ARTICLE Immunogenetics of CD4 Lymphocyte Count Recovery during Antiretroviral Therapy: An AIDS Clinical Trials Group Study Downloaded from https://academic.oup.com/jid/article/194/8/1098/870426 by guest on 28 September 2021 David W. Haas,1 Daniel E. Geraghty,2 Janet Andersen,3,4 Jessica Mar,3,4 Alison A. Motsinger,1 Richard T. D’Aquila,1 Derya Unutmaz,1 Constance A. Benson,5 Marylyn D. Ritchie,1 and Alan Landay6 1Vanderbilt University, Nashville, Tennessee; 2Fred Hutchinson Cancer Research Center, Seattle, Washington; 3Harvard School of Public Health and 4Statistical Data and Analysis Center, Boston, Massachusetts; 5University of California, San Diego, San Diego; 6Rush University Medical Center, Chicago, Illinois During antiretroviral therapy, CD4 lymphocyte count increases are modest in some patients despite virologic control. We explored whether polymorphisms in genes important for T cell expansion, survival, and apoptosis are associated with the magnitude of CD4 lymphocyte count recovery during antiretroviral therapy. We studied treatment-naive individuals who achieved sustained control of plasma viremia (!400 HIV-1 RNA copies/mL) for at least 48 weeks after initiation of antiretroviral therapy and compared genotypes among individuals who had an increase of either !200 or у200 CD4 cells/mm3 from baseline. A total of 137 single-nucleotide poly- morphisms across 17 genes were characterized in 873 study participants. In multivariate analyses that controlled for clinical variables, polymorphisms in genes encoding tumor necrosis factor (TNF)–related apoptosis-in- ducing ligand (TRAIL), TNF-a, Bcl-2–interacting molecule (Bim), interleukin (IL)–15, and IL-15 receptor a chain (IL-15Ra) were associated with the magnitude of the increase in CD4 lymphocyte count, as were haplotypes in genes encoding interferon-a, IL-2, and IL-15Ra (P ! .05 , for each). Multifactor dimensionality reduction identifie a gene-gene interaction between IL-2/IL-15 receptor common b chain and IL-2/IL-7/IL- 15 receptor common g chain. Immune recovery during antiretroviral therapy is a complex phenotype that is influence by multiple genetic variants. Future studies should validate these tentative associations and defin underlying mechanisms. HIV-1 infection causes decreased production and in- several cytokines (interleukin [IL]–2, IL-7, and IL-15) creased destruction of CD4 lymphocytes [1–3]. Anti- and their receptors (IL-2R, IL-7R, and IL-15R) [10, 11]. retroviral therapy typically brings about substantial im- Both IL-7 and IL-15 are required for naive T cell sur- mune reconstitution [4, 5], but there is considerable vival [12], and both promote memory T cell prolifer- interindividual variability in peripheral-blood CD4 lym- ation [13, 14]. In addition, both IL-7 and IL-15 may phocyte count recovery during HIV therapy. Predictors enhance memory T cell survival by increasing the ex- of lesser CD4 lymphocyte count increases include in- pression of antiapoptotic proteins [15, 16]. Growth of creasing age [6] and lower pretreatment plasma HIV- 1 RNA concentrations [6–9]. Proliferation and survival of T cells are regulated by Presented in part: 3rd International AIDS Society Meeting, Rio de Janeiro, 24– 27 July 2005 (abstract MoOa0303); 13th Conference on Retroviruses and Op- portunistic Infections, Denver, 22–25 February 2006 (abstract 443). Potential conflicts of interest: D.W.H. has received research grants from Bristol- Myers Squibb (BMS), Boehringer Ingelheim (BI), Schering Plough, Bavarian Nordic, Received 24 March 2006; accepted 16 May 2006; electronically published 6 and Gilead Sciences. J.A. is a consultant for Tibotec. R.T.D. is a consultant for September 2006. and/or has received honoraria or research grant support from BMS, Gilead Reprints or correspondence: Dr. David W. Haas, Center for Human Genetics Sciences, GlaxoSmithKline (GSK), Abbott Laboratories, BI, and Tibotec. M.D.R. is Research, Vanderbilt University School of Medicine, 345 24th Ave. N., Suite 105, a consultant for BI. C.A.B. is a consultant for and/or has received research grant Nashville, TN 37203 ([email protected]). support from Gilead Sciences, Merck, BI, GSK, Tibotec, and Johnson and Johnson The Journal of Infectious Diseases 2006;194:1098–1107 Research. A.L. has received a research grant from Abbott Laboratories. A.A.M., ᮊ 2006 by the Infectious Diseases Society of America. All rights reserved. J.M., D.E.G., and D.U. report no potential conflicts of interest. 0022-1899/2006/19408-0010$15.00 Financial-support information is given in the Acknowledgments. 1098 • JID 2006:194 (15 October) • Haas et al. CD4 lymphocytes in vitro requires IL-2, and, after T cell ac- ation, survival, and apoptosis. This is the firs study to system- tivation, IL-2R expression is transiently up-regulated [17], al- atically address the immunogenetics of CD4 lymphocyte count though the importance of IL-2 for T cell expansion in vivo is recovery during antiretroviral therapy. less certain [18]. The effects of IL-2, IL-7, and IL-15 may be regulated through the differential expression of their receptors. PARTICIPANTS, MATERIALS, AND METHODS All 3 receptors share an identical g chain (IL-2Rg). In addition, IL-2R and IL-15R share a common b chain (IL-2Rb) [19], Study participants. This retrospective analysis included par- ticipants from AIDS Clinical Trails Group (ACTG) protocol whereas each receptor has a distinct a chain (IL-2Ra, IL-7Ra, A5001, a prospective, longitudinal cohort study that coenrolls and IL-15Ra). Tumor necrosis factor (TNF)–a also affects T participants from randomized ACTG antiretroviral treatment cell proliferation, whereas interferon (IFN)–a and IFN-b in- trials in the United States and Puerto Rico to evaluate long- fluenc activated T cell survival. term responses to antiretroviral therapies. The participants in- Normal homeostasis requires a balance between cellular pro- Downloaded from https://academic.oup.com/jid/article/194/8/1098/870426 by guest on 28 September 2021 cluded in the present analyses (1) were antiretroviral naive and liferation and programmed death (apoptosis). During the ac- had a CD4 lymphocyte count of !800 cells/mm3 at baseline quired immune response to foreign antigen, T cell expansion and (2) achieved a plasma viremia of !400 HIV-1 RNA copies/ is followed by the apoptosis of activated antigen-specifi cells, mL during therapy and maintained this level of suppression at with relatively few cells surviving to provide memory. The ex- every determination (generally at 8–16-week intervals) for at trinsic apoptosis pathway is initiated by the binding of several least 48 weeks. As a convenience sample, we included every TNF family ligands to death receptors. Specificall , Fas ligand eligible A5001 participant with sustained control of plasma binds to the death receptor Fas [20], TNF-related apoptosis- viremia for 48 weeks as of June 2004 who contributed speci- inducing ligand (TRAIL) binds to 2 death-inducing receptors mens to the ACTG Human DNA Repository (Center for Hu- (DR4 and DR5) [21], and TNF-a binds to TNF receptor man Genetics Research, Vanderbilt University) under protocol (TNFR)–I and TNFR-II. Signaling through TNFR-I can both A5128 [30]. We compared participants with a CD4 lymphocyte abrogate and potentiate apoptosis [22]. Death receptor binding count increase of !200 cells/mm3 from baseline to 48 weeks of triggers activation of the cysteine protease, caspase 8, and cul- virologic suppression with those with an increase of у200 cells/ minates in cell death [23, 24]. mm3. Although this value was chosen a priori, it happened to The intrinsic pathway to apoptosis is controlled by Bcl-2 approximate the median CD4 lymphocyte count increase. Ad- family proteins [25, 26]. In vivo, many activated T cells die of ditional post hoc analyses excluded individuals with a CD4 lym- the effects of the proapoptotic Bcl-2 family member, Bcl-2– 3 phocyte count of 1350 cells/mm at baseline and with a CD4 interacting molecule (Bim) [27]. Normally, Bcl-2 protects T lymphocyte count increase between 100 and 200 cells/mm3. cells from the apoptotic actions of Bim [27]. Cytokine signaling The present study complied with the Helsinki Declaration and through g chain receptors (IL-2, IL-7, and IL-15) increases Bcl- was approved by institutional review boards at each site, and 2 expression, which protects against Bim. Conversely, cytokine participants provided written, informed consent. withdrawal allows Bim to trigger apoptosis [27]. The death of Identificatio of genetic variants. Primer pairs amplifie naive T cells may also involve Bim [28]. intervals from 800 bp to 1.2 kbp; the human genome sequence There is extensive cross talk between proliferation and ap- consensus was used as template, and software that incorporated optosis pathways. Proliferation after T cell receptor engagement fundamentals of Primer3 was used [31]. Repetitive regions were is enhanced by TRAIL, IL-2 primes activated T cells for apo- avoided by use of RepeatMasker [32]. Polynucleotide and mul- ptosis, and both TNF-a and IFN-b can stimulate apoptosis. tisatellite sequences were avoided or directed toward the center Furthermore, IFN-a and IFN-b produced by HIV-1–activat- of amplicons. SNPs were chosen on the basis of 3 criteria: (1) ed plasmacytoid dendritic cells can regulate the expression of known nonsynonymous coding variants, (2) variants in or near TRAIL by CD4 lymphocytes [29]. In addition, TNF-a can stim- promoter sequences, and (3) variants of unknown function that ulate HIV-1 replication, whereas IFN-a and IFN-b inhibit HIV- marked genes, including haplotype-tagging polymorphisms [33, 1 replication. 34]. A balance among these criteria was achieved within the The influenc that human genetics has on CD4 lymphocyte funding available for this project. Primer pairs were firs tested count recovery during antiretroviral therapy is not known. We on DNAs from 4 cell lines, to assure the ability to generate hypothesized that increased expression or activity of genes that reliable amplicons and derivative sequence data.