These changes in median platelet counts in the IT arms were similar to those previously reported with CD4 T-cell counts, and mirrored those of plasma HIV RNA levels and CD8 T-cell counts which increased during treatment interruptions and decreased under treatment.2
We therefore wished to assess correlations between changes from baseline to week 8 in platelet counts with those of CD4 T-cells, CD8 T-cells, and plasma viral load among patients randomized in the IT arm. As shown in Figure 3A, there was a moderate but significant correlation between changes in platelet counts and changes in CD4 T-cell counts (P < 0.0001), and an inverse correlation between platelet counts and plasma HIV RNA levels (P = 0.0005; Fig. 3B), whereas no correlation was found with changes in CD8 T-cells count (Fig. 3C).
Many clinical trials have addressed the issue of treatment interruption among patients with controlled HIV infection under antiretroviral therapy.1-4 Very few, however, have reported on the risk of thrombocytopenia associated with treatment discontinuation, although thrombocytopenia could potentially lead to severe clinical manifestations. In the Staccato trial, the authors reported a low incidence of thrombocytopenia, defined as a platelet count below 100 × 103/mm3, among patients randomized in the interruption arm (2.5%), which was not significantly higher than in the continuous arm (0%, P = 0.1).1 The same authors have also described 3 patients with recurrent thrombocytopenia in this same trial during periods off treatment.13 Maggiolo et al10 have reported the case of a patient with a history of HIV-related thrombocytopenia who experienced a platelet count below 1000/mm3, 4 months after treatment discontinuation, and who recovered after resuming antiretroviral therapy.
Using data from the Window trial, we were able to show that the risk of thrombocytopenia is high among patients interrupting their antiretroviral therapy, with a 96-week incidence of near 25% (Fig. 1). This incidence was significantly higher than among patients maintaining their antiretroviral therapy (9.8%, P < 0.0001 by the Log-rank test). Interestingly, median time to thrombocytopenia was only 9 weeks in the IT arm, and the main difference between arms was seen already at week 8, at the end of the first treatment interruption, with Kaplan-Meier plots remaining almost parallel between arms after week 8 (Fig. 1).
According to the definition of thrombocytopenia used in this study, a platelet count below 150 × 103/mm3, the clinical relevance of these observations could seem limited. However, 11 patients developed a severe thrombocytopenia with a platelet count below 50 × 103/mm3 during the study, after discontinuation of antiretroviral therapy in all but 2. Two of the patients were symptomatic with hematomas and gynecological bleeding. The consequences of these low platelet counts could have been more severe if antiretroviral therapy was not resumed after 8 weeks, and if platelet counts were not monitored every 8 weeks in this clinical trial. Fatal bleeding due to intracranial hemorrhage has been reported in patients with idiopathic thrombocytopenic purpura (ITP).14 It is, therefore, important to remind patients and physicians that even a short treatment interruption of a few weeks could lead to severe thrombocytopenia and that platelet counts should be carefully monitored if antiretroviral therapy has to be discontinued.
We then tried to identify baseline predictors of thrombocytopenia in this study. Among all baseline variables tested in our multivariate model (Table 2), being randomized in the treatment interruption arm, having a low baseline platelet count, and a history of HIV-related thrombocytopenia were all significantly associated with the occurrence of thrombocytopenia.
Other variables including CD4 cell count, either at baseline or at the nadir, were not associated with thrombocytopenia. Female sex was not found either as a risk factor for thrombocytopenia in this study. Also, the use of zidovudine or ddI in the antiretroviral regimen was not found to be associated with thrombocytopenia, probably because the reported beneficial effects of these drugs in patients with HIV-related thrombocytopenia are not specific, but rather the consequence of their antiviral activity.15-18 The benefit of antiretroviral therapy on HIV-related thrombocytopenia has indeed been well documented.16-20
Analyzing the changes in median platelet counts among patients randomized in the interruption arm during the 96 weeks of the Window trial, could also give insights into the pathogenesis of thrombocytopenia during HIV infection. Thrombocytopenia is indeed a common complication of HIV infection, and HIV-related thrombocytopenia resembles ITP, with normal or increased numbers of megakaryocytes in the bone marrow, and increased platelet-associated IgG autoantibodies. HIV-related thrombocytopenia is supposed to be the consequence of both a depressed platelet production secondary to HIV infection of megakaryocytes,15,21-26 and a reduction in platelet survival due to their increased peripheral destruction by macrophages through platelet-associated autoantibodies or circulating immune complexes, with sequestration in the spleen and sometimes the liver.15,22,27-30 Molecular mimicry between HIV antigens, mainly the envelope glycoprotein 120/160,31-34 and membrane-associated platelet glycoproteins such as IIB/IIIa, explains the cross-reactivity of these platelet-associated autoantibodies with HIV antigens.33,35,36 In patients with ITP, antibodies against glycoprotein IIb/IIIa probably originate from a limited number of B-cell clones, and these patients have increased numbers of HLA DR+ T-cells, and a cytokine profile suggesting T-cell activation, similar to what is found during HIV infection. The factors that initiate autoantibody production are unknown in patients with ITP, but it is tempting to hypothesize that HIV replication triggers the production of platelet autoantibodies in patients with HIV infection.37
During this study, median platelet count indeed decreased during each treatment interruption and increased to near the baseline value after each period on treatment (Fig. 2). These changes in platelet counts were fast, and followed the same course previously reported with CD4 cell counts in this study. Also, changes in platelet counts mirrored those seen with plasma HIV RNA levels during periods on and off treatment. Interestingly, week 8 changes from baseline in median platelet counts were significantly positively correlated with changes in CD4 T-cells, and negatively correlated with plasma HIV RNA levels. Such an association between platelet counts and plasma HIV RNA levels has already been reported in cohorts of HIV-infected hemophiliacs.38 The decrease of platelet counts observed during each treatment interruption is therefore likely to be the direct consequence of HIV replication.
In conclusion, this study demonstrated that antiretroviral therapy interruption among patients with well-controlled HIV infection, could lead to the rapid occurrence of thrombocytopenia, especially among those with a low baseline platelet count or a history of HIV-related thrombocytopenia. Treatment interruption should therefore be strictly forbidden for such patients. The decrease in platelet count during treatment interruption is correlated to the decrease in CD4 T-cells, and negatively correlated to plasma HIV RNA levels. This risk of thrombocytopenia is therefore another limitation of IT, which should be avoided as much as possible.
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The members of Window ANRS 106 Study Team were as follows: Trial chair-B. Marchou; Trial co-chair-J.M. Molina; Trial Coordinator and Monitors-P. Tangre, J.P. Aboulker; Trial Statistician-I. Charreau; Trial virologists-J. Izopet; Scientific Committee-B. Marchou, J. Izopet, P. Tangre, J.P. Aboulker, P.M. Girard, T. May, J.M. Molina Data Safety and Monitoring Board-M. Seligmann, F. Brun-Vezinet, A. Laplanche; Coordinating Trial Centre: INSERM SC10 J.P. Aboulker, P. Tangre, A. Uludag, M. Saouzanet, V. Eliette, C. Lascoux, S. Delmas, S. Gueguen, A. Polaert, I. Charreau (statistics) B. Guillon and Y. Saïdi (data management). Participating Centers and Investigators (all in France)-Hôpital Debré, Reims: Remy, Strady, Rouger, Beguinot, Berger, Brodard, Tabary, Gourdier; Hôpital Lagny Marne la Vallée: Lagarde, David-Ouaknine, Simon, Froguel, Le Rudulier, Costa, Louin; Hôpital Avicenne, Bobigny: Guillevin, Jarrousse, Krivitzki, Lortholary, Bentata, Klutse, Djebbar, Makki, Belarbi, Obenga, Honoré, Touam, Mansouri, Baazia, Feuillard, Soreda; Hôpital Bellevue, St. Etienne: Lucht, Fresard, Cazorla, Ronat, Saoubin, Lambert, Simoens; Hôpital St. Jacques, Besançon: Estavoyer, Hoen, Pichon, Coquet, Bettinger, Tiberghien, Legalery; Hôpital Pellegrin, Bordeaux: Dupon, Ragnaud, Raymond, Dutronc, Ochoa, Lafabie, Neau, Chambon, Garrigue, Moreau, Dupin; Hôpital Bicêtre, Kremlin-Bicêtre: Delfraissy, Goujard, Robquin, Segeral, Quertainmont, Guillet, Lambert, Rannou, Taburet, Bocquentin, Idri, Gubler; Hôpital Lariboisière, Paris: Bergmann, Sellier, Diemer, Bendenoun, Rami, Parinello, Mazeron, Boval, Roux; Hôpital R Poincaré, Garches: Perronne, De Truchis, Melchior, Salomon, Berthe, Mathez, Paillet; Hôpital P Brousse, Villejuif: Vittecoq, Teicher, Smadja, Bergerol, Merad, Minozzi, Bolliot, Mallet, Bensidhoum, Mackiewicz, Kara Terki, Rudant; Hôpital G Pompidou, Paris: Kazatchkine, Weiss, Gonzales-Canali, Haddadi, Piketty, Karhaman, Karmochkine, Bengrait, Si Mohamed, Caccavelli, Sabatier; Hôpital Bichat, Paris: Yeni, Vilde, Leport, Bouvet, Al Kaied, Charlois, Jestin, Benabdelmoumen, Fournier, Hadjoudj, Phung, Gaudebout, Le Gac, Pahlavan, Zeng, Chams, Elbim, Certain; Hôpital Cochin, Paris: Sicard, Salmon-Ceron, Spiridon, Krivine, Lacombe, Guerin; Hôpital Foch, Suresnes: Bletry, Zucman, Majerholc, Honderlick, Drupt, Bessard; Hôpital Pitié-Salpêtrière, Paris: Bricaire, Herson, Katlama, Simon, Tubiana, Ghosn, Duvivier, Boubezari, Schoen, Curjol, Kouadio, Amirat, Bonmarchand, Capitaine, Lambert, Brançon, Carcelain, Samri, Hrichi, Fievet; Hôpital St. Antoine, Paris: Girard, Meynard, Meyohas, Bollens, Roussard, Lefebvre, Besse, Berriot, Gaujour, Lagneau, Lupin, Morand-Joubert, Rosenzwajg, Charrois, Archi, Daguenel-Nguyen; Hôpital St Louis, Paris: Molina, Ponscarme, Tourneur, Fournier, Ferret, Balkan, Bani Sadr, De Castro, Garrait, Goguel, Lafaurie, Neuville, Furco, Perignon, Maslo, Colin de Verdière, Rachline, Loze, Schnell, Palmer, Rabian, Madelaine; Hôpital St. André, Bordeaux: Beylot, Morlat, Lacoste, Bernard, Malvy, Nouts, Pertusa, Bonarek, Thibault, Garrigue, Moreau, Pedeboscq; Hôpital E Herriot, Lyon: Touraine, Livrozet, Jeanblanc, Makhloufi, Brunel, Palmer, Tardy, Malcus, Nageotte; Hôpital Hôtel-Dieu, Lyon: Trepo, Augustin-Normand, Benmakhlouf, Cotte, Bailly, Miailhes, Schlienger, Thoirain, Brochier, Ritter, Bataillard; Hôpital Ste Marguerite, Marseille: Gastaut, Poizot-Martin, Frixon-Marin, Dinh, Dignat-Georges, Tamalet, Penot-Ragon; Hôpital Gui de Chauliac, Montpellier: Reynes, Atoui, Baillat, Lotthe, Siffert, Le Moing, Merle de Boever, Vidal, Tramoni, Montes, Pages, Giraudon; Hôpital Hôtel-Dieu, Nantes: Raffi, Billaud, Milpied, Bugnon, Bonnet, Hue, Ferre, Poirier, Audrain, Lepelletier; Hôpital Les Oudairies, La Roche sur Yon: Perre, Aubry, Desailly-Chanson, Ferre, Berruchon; Hôpital L'Archet, Nice: Dellamonica, Cassuto, Ceppi, Rahelinirina, Poirée, Bagot, Cottalorda, Benhamou, Ticchioni, Rigault; CHRU de Strasbourg: Lang, Cheneau, Hess, Kempf, Priester, Rey, Fischer, Ebel, Schmitt, Uring-Lambert, Hutt; Hôpital Bretonneau, Tours: Choutet, Bastides, Besnier, Nau, Vauthier, Dailloux, Guerois, Barin, Thibault, Chartrin; Hôpital Purpan, Toulouse: Massip, Marchou, Cuzin, Obadia, Bicart-See, Bonnet, Khatibi, Alvarez, Labau, Picot, Balsarin, Jaafar, Izopet, Kuhlein, Peyranne; CHU de Clermont-Ferrand: Beytout, Laurichesse, Jacomet, Henquell, Chassagne, Coudert; CHU de Grenoble: Leclercq, Blanc, Trappo, Dufresnes, Schmuck, Jacob, Boitard; Centre Hospitalier de Tourcoing: Mouton, Cheret, Dos Santos, De la Tribonnière, Vandamme, Labalette, Bocket, Dubar; CHU Brabois, Nancy: May, Boyer, Ahmed Khalifa, Kolopp-Sarda, Le Faou, Demore; Hôpital Croix-Rousse, Lyon: Peyramond, Boibieux, Braun, Lippmann, Cozon, Ritter, Charpiat; Hôpital La Grave, Toulouse: Viraben, Aquilina, Cuzin, Abboud, Lucas, Prevoteau du Clary, Barone, Pomies.