The estimated mean increase in CD4+ T-cell counts between weeks 0 and 24 was more than 78 cells/μl per month [95% confidence interval (CI) +66 to 90] in the IL-2 group, whereas it was stable (more than 2 cells/μl per month, 95% CI −11 to +15) in the control group. When adjusting for other factors (Table 1), the cumulative duration of exposure to ART before inclusion and the level of HIV-1 DNA were associated with the CD4 T-cell counts dynamics before antiretroviral interruption. Indeed, the increase of CD4 T-cell counts was blunted for longer exposure to antiretrovirals (four cells per month less per year of exposure, P = 0.04) and for higher levels of HIV-1 DNA (28 cells/month less per log10 copies/million of peripheral blood mononuclear cells, P = 0.02). None of these factors modified the effect of IL-2 on CD4+ T-cell counts change.
After week 24, we identified a biphasic decline of CD4 with a first slope before week 32 and a weaker decline between week 32 and week 168. These slopes (in cells/μl per month) were significantly different (all P ≤ 0.0001) between the two groups being more pronounced in the IL-2 group (−234 and −17) than in the control group (−106 and −7).
Figure 3b shows actual median plasma HIV-RNA over time. All patients had viral loads less than 50 copies/ml at week 24. Following ART cessation, plasma HIV RNA rebounded up to 4.33 log10 copies/ml (3.86; 4.79) in the IL-2 group and 4.39 log10 copies/ml (3.92; 4.76) in the control group (P = 0.71) and did not change throughout the follow-up period.
Thirty patients from each group participated in an immunologic substudy. Baseline characteristics of these patients were globally similar to the study population with the exception of sex (Table 2 in SDC 1, http://links.lww.com/QAD/A204). In this substudy, at week 24, median CD4+ T cells/μl were 1143 and 653 in IL-2 and control groups, respectively (P < 0.001). These values were 811 and 645 at week 48 (P = 0.01) and 594 and 541 at week 96 (P = 0.57). Analyses of CD4+ T-cell subpopulations in the IL-2 group show that naive, central memory, effector memory cells increased from 356, 284, 57 to 461, 458 and 144 cells/μl (P < 0.006 for all comparisons) at week 24, whereas no changes in terminally differentiated effector memory cells were noted (47 and 42). As expected [2,7], IL-2-expanded-CD4+ T cells expressed CD25 (41% of all CD4 T cells at week 24; Fig. 4a). The proportion of CD4+ T cells expressing CD38 or human leucocyte antigen (HLA-DR) decreased significantly between baseline and week 24 (P < 0.001 and P = 0.041) in the IL-2 group. No significant changes for any of the above markers were noted in the control group (Fig. 4b). Following interruption of ART, between weeks 24 and 48, the median decline of naive, central memory, effector memory and terminally differentiated effector memory populations at week 48 was −96, −119, −40 and −20 cells/μl in the IL-2 group. These values were similar in the control group (P > 0.07 for all comparisons): −61, −35, −12 and −5 cells/μl, so that differences observed at week 24 persisted at week 48. The proportion of CD4+ T cells expressing activation markers (CD38 or HLA-DR) tended to remain lower in IL-2 recipients as compared to controls at weeks 24 and 48 (P = 0.023 and P = 0.081, respectively). IL-2-expanded CD4+CD25+ T cells decreased to 26% at week 96 but remained higher than in the control group (26 vs. 16%, P = 0.006). Conversely, the number of CD4+CD25− T cells decreased after week 24 but did not differ between the two groups (P > 0.07 for all comparisons). The differential expression of the activation markers CD38 and HLA-DR on CD4+CD25+ T cells between IL-2 recipients and controls was even more pronounced than in the total CD4+ T-cell population (Fig. 4b). The pattern of the dynamics of the markers seemed remarkably defined very early after viral rebound as seen in the three patients with highly repeated measurements after treatment interruption (Table 3 in SDC 1, http://links.lww.com/QAD/A204).
Safety and tolerability
A high number of adverse events related to IL-2 administration were reported during the first 24 weeks of the trial. The vast majority of these events were mild (grades 1 to 2). Constitutional symptoms (such as asthenia, fever, nausea…) were the most frequent complaints and accounted for 50% of all adverse events. Among the 17 patients who decided to stop IL-2, adverse effects of IL-2 were involved as the main reason in 11 of them. The number of severe adverse events was low (n = 10 patients; seven in IL-2 group and three in control group). Also, 11 patients (14%) in the IL-2 group and 16 (24%) in the control group experienced grade 3 or 4 laboratory abnormalities (P = 0.11), with a similar number of events in each group. One patient from the IL-2 group (esophageal candidasis) at week 196 and three patients from the control group (ocular B-cell lymphoma, B-cell lymphoma, esophageal candidasis at week 43, 104 and 82, respectively) experienced an AIDS-defining event. Six cardiovascular events occurred in four patients after week 24 (antiretroviral interruption): one myocardial infarction with coronary bypass in a patient presenting an abdominal aneurysm, two strokes (same patient), one pulmonary embolism, one arterial thrombosis. Only one occurred in the IL-2 group (i.e. pulmonary embolism).
The ANRS-National Institute of Health (NIH) ILIADE trial showed that administration of three cycles of IL-2 in HIV-infected patients with high CD4+ T-cell counts and controlled viral load while on ART may significantly delay indication of ART resumption following ART interruption. Longitudinal phenotypic analyses showed a unique behavior and phenotype of IL-2-expanded CD4+ T cells. Despite viral replication, IL-2-expanded CD4+ T cells remained significantly higher than in the control group up to 72 weeks. This effect was related to a significant increase of CD4+ T cells harboring CD25 and expressing a low level of activation markers.
The ANRS/NIH ILIADE trial was designed at a period in which several clinical studies evaluating the potential interest of structured treatment interruption (STI) [22,23] were initiated. The major safety problem for patients enrolled in a study with STI of a short-term duration (less than 6 months) is related to CD4+ T-cell counts drop below 350 cells/μl. Recent studies from our group and others have shown that patients’ survival might be affected if they are exposed to CD4+ T-cell counts less than 500 cells/μl [24,25]. Although the value of CD4+ T-cell counts as a surrogate marker for disease progression in IL-2 therapy setting is highly challenged, the rationale of the use of IL-2 before treatment interruption was to limit CD4+ T-cell decline. Moreover, our study differed in several aspects to the large majority of ART interruption studies [26,27]. First, the population of patients eligible to participate was expected to have a high CD4+ T-cell counts at inclusion (higher than 500) and most patients had still high CD4+ T-cell counts at week 48. Second, the decrease of CD4+ T cells following ART interruption was steeper in the present study and even more pronounced in IL-2-treated patients. The same magnitude of CD4 steep decrease and viral load plateau was reported by the ACTG A5132 among IL-2-treated patients after ART interruption included . This observation may be seen as unexpected in regard of previous studies demonstrating clearly that IL-2-expanded CD4+ T cells exhibit a longer half-life as compared to ‘conventional’ CD4+ T cells . However, one mechanistic explanation is that the drop of CD4+ T cells at a given time is proportional to the number of cells in addition to the death rate. Therefore, for a given death rate, the decline of CD4+ T-cell counts will be steeper for a patient with a higher number of CD4+ T cells at the time of antiretroviral treatment interruption. This could also be the explanation of observed differences in CD4+ T-cell drop in the control group (with a median of 703 cells/μl at week 24) compared to the previously published studies (with a median around 350 cells/μl before interruption). As previously reported, we also found that the frequency of CD4+ T cells expressing activation markers, even following treatment interruption, was lower in IL-2-treated patients as compared to those treated with ART only. Altogether, these data suggest at least two phases in the homeostasis of T-cell pool in IL-2-treated patients following viral rebound. The initial phase is marked by drop of CD4+ T cells highly correlated with the CD4+ T-cell gain at the end of IL-2 cycling (week 24). In contrast, the second phase is characterized by a slow decline of long-living CD4+CD25+ T cells that were not activated, quiescent, and therefore prone to resist HIV infection.
A key challenge in developing disease-modifying interventions is showing that a biomarker or combination of biomarkers is a surrogate for disease progression. Results from SILCAAT and ESPRIT studies have shown that CD4+ T-cell counts under IL-2 therapy cannot be considered as a valuable surrogate marker of disease progression. Our results suggest that in addition to total CD4 cell counts, markers such as T-cell immunophenotypic analyses (e.g., activated and regulatory T cells), and possibly functional assays or other markers of inflammation and activation, should be considered. We show that IL-2 administration before ART interruption tips the balance in favor of CD4+CD25+ as compared to ‘conventional’ CD4+CD25−. Long-term clinical consequences of this new equilibrium are not obvious. In one hand, the recent observation in ART-treated patients that these cells may suppress effector T cells responses, suggest a potential harmful effect . On the other hand, a limited expansion and persistence of these cells might help to contain immune activation and to prevent the development of opportunistic infections as recently suggested in more advanced patients with a benefit of IL-2 restricted to a narrow range of CD4+ T-cell counts . More recently, further analyses of SILCAAT and ESPRIT studies have also shown that the effect of IL-2 on all causes of death may vary by baseline D-dimer levels . These results underscore the need to pursue researches aiming at identifying a target population who might benefit from disease-modifying interventions and specifically from gamma chain-utilizing cytokines such as IL-7 and IL-15.
In conclusion, this study shows that the administration of IL-2 before antiretroviral treatment interruption in individuals with nonadvanced HIV disease led to a longer period before antiretroviral resumption that might be explained by the expansion of CD4+ T cells with a unique phenotype [29,32] and a long survival despite the presence of replicating virus.
Presented in part at the 16th Conference on Retroviruses and Opportunistic Infections, Montreal, February 2009, ML, USA (abstract H-110).
We thank Chiron laboratories for graciously providing Interleukin 2 for this trial. We are grateful to Jean-Pierre Aboulker, Pablo Tebas, Claude Bazin and Dominique Emilie, members of the Data and Safety Monitoring Board of the study.
We acknowledge the excellent work performed by the events validation committee: Geneviève Beck-Wirth, Véronique Joly, A.S.L., Corinne Rancinan and I.S.
We thank Cecile François and Daniel Commenges for their contribution to the modeling analysis.
ILIADE ANRS 118 study team: The following institutions and investigators participated in the ILIADE trial. CH Annecy: C Michon, JP Bru, J Gaillat; CH Belfort: JP Faller; Hôpital Jean Verdier, Bondy: V Jeantils, M Thomas; CHU Bordeaux, Hôpital Saint-André: J Beylot, P.M., Hôpital Pellegrin: JM Ragnaud; CHU Clermont-Ferrand: J Beytout, C Jacomet; Hospices Civils de Lyon, Hôtel Dieu: L Cotte, C Trepo; Hôpital Edouard Herriot: JL Touraine, F Jeanblanc; CHU Montpellier: J Reynes; CH Mulhouse: G Beck-Wirth; CHU Nantes, Hôtel Dieu: F Raffi; Assistance Publique-Hôpitaux de Marseille, Hôpital Sainte Marguerite: JA Gastaud, I Poizot-Martin; Assistance Publique-Hôpitaux de Paris, Hôpital Avicenne, Bobigny: M Bentata; Hôpital de Bicêtre, Le Kremlin Bicêtre: J.F.D., C Goujard; Hôpital Antoine Béclère, Clamart: F Boué, P Galanaud; Hôpital Henri Mondor, Créteil: Y.L., A Sobel; Hôpital Bichat Claude-Bernard: E Bouvet, P Yéni; Hôpital Européen Georges Pompidou: M Kazatchkine, L.W.; Hôpital Lariboisière: JF Bergmann, P Sellier; Hôpital Necker: B Dupont, J.P.V.; Hôpital Saint-Antoine: P.M.G.; Hôpital Saint-Louis: C Lascoux-Combe, J.M.M., E Oksenhendler, D Séréni; National Institutes of Health Clinical Center, Bethesda (USA): C.L., T Miller, I.S.
Steering Committee: G.C., JF Delfraissy, M.L.G., C Goujard, Y.L., J.M.M., C Rancinan, C.R., AM Taburet, A.V., J.P.V., L.W., S Couffin-Cadiergues (representing ANRS), M Beumont (representing Chiron), and invited experts: V Avettand-Fenoel, M Bocquentin, C Jung, C Lacabaratz, A.S.L., B.P., L Rogge, R.T.
Funding: This study was supported by the French National Agency for Research on AIDS and Viral Hepatitis (ANRS, Trial No. 118) and the Intramural Research Program of NIAID/NIH (NIH 04-I-0018 trial).
Clinical Trials Unit/INSERM U897, Bordeaux School of Public Health (ISPED), University Victor Segalen Bordeaux 2: M Badets, M Bonarek, C.B., G.C., S Desjardins, C Fagard, M François, A Frosch, L Lallemand, G Poizat, C Rancinan, R Winum.
Sponsor: ANRS (French National Agency for Research on AIDS and Viral Hepatitis): M.J. Commoy, S. Couffin-Cadiergues, A. Metro.
Conflicts of interest
None of the authors declare conflict of interest.
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antiretroviral therapy interruption; HIV; interleukin-2
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