Fatal pancreatitis in simian immunodeficiency virus SIV(mac251)-infected macaques treated with 2',3'-dideoxyinosine and stavudine following cytotoxic-T-lymphocyte-associated antigen 4 and indoleamine 2,3-dioxygenase blockade

Abstract

Human immunodeficiency virus (HIV) infection is associated with immune activation, CD4⁺-T-cell loss, and a progressive decline of immune functions. Antiretroviral therapy (ART) only partially reverses HIV-associated immune dysfunction, suggesting that approaches that target immune activation and improve virus-specific immune responses may be needed. We performed a preclinical study in rhesus macaques infected with the pathogenic simian immunodeficiency virus SIV(mac251) and treated with ART. We tested whether vaccination administered together with cytotoxic-T-lymphocyte-associated antigen 4 (CTLA-4) blockade and treatment with the indoleamine 2,3-dioxygenase (IDO) inhibitor 1-methyl-D-tryptophan (D-1mT), decreased immune activation and improved vaccine efficacy. The treatment did not augment vaccine immunogenicity; rather, it dramatically increased ART-related toxicity, causing all treated animals to succumb to acute pancreatitis and hyperglycemic coma. The onset of fulminant diabetes was associated with severe lymphocyte infiltration of the pancreas and complete loss of the islets of Langerhans. Thus, caution should be used when considering approaches aimed at targeting immune activation during ART.

Fig 1

Study design and effect of CTLA-4 and IDO blockade on Kyn/Trp ratio. (A) Study design. Details are given in Materials and Methods. (B) IDO mRNA/18S rRNA ratio in the lymph nodes during ART only (week 32) and at 1 week from the second treatment. (C to E) Trp (C) and Kyn (D) levels and Kyn/Trp ratio (E) measured at 1 week after treatment with 1mT. Each animal is represented by a symbol, as indicated. In all graphs the thick lines represent the mean values among all animals at each time point.

Fig 2

Effect of CTLA-4 and IDO blockade on T-cell numbers and vaccine immunogenicity. (A) Average values of the absolute numbers of CD4⁺ and CD8⁺ T cells in the blood over time. The arrows and the dark squares represent each MDX-010 and d-1mT administration. The gray area represents ART. (B) Averages ± standard deviations of the frequencies of Ki67⁺ CD95⁺ CD4⁺ and CD8⁺ T cells during ART only (week 32) and at 1 week after each treatment (weeks 38, 42, and 46). (C) TGF-β mRNA normalized on 18S rRNA in the lymph nodes during ART only (week 32) and at 1 week from the second treatment. (D) Frequency of T_h1 cells, defined as CD4⁺ T cells producing IFN-γ, after 6 h of stimulation with PMA-ionomycin. (E) SIV_mac251 viral RNA in plasma over time. (F and G) Absolute numbers of tetramer⁺ CD95⁺ CD8⁺ T cells specific for SIV gag (CM9) (F) and for SIV tat (SL8) (G) in blood. The bars represent the averages ± standard deviations for 4 MamuA*01⁺ macaques used in the current study and 3 MamuA*01⁺ macaques used in previous studies, vaccinated with the same vaccine and treated with the same antiretroviral treatment (8), at 1 week from each vaccination.

Fig 3

Treatment related-metabolic dysfunctions and onset of fulminant diabetes. (A) Incidence of diabetes after each treatment. (B and C) Effect of the treatment on plasma lipase (B) and glucose (C) levels. (D) Microscopic examination of pancreatic tissues collected at necropsy from animal M683, revealing tissue destruction (left panel) and lymphocytic infiltration (left panel, arrow, and right panel).