The goal of the present study was to develop a nonhuman primate model of intravaginal human immunodeficiency virus (HIV) transmission with cell-associated virus. Reproductively mature, cycling cynomolgus macaques with or without chemically induced, transient ulcers of the lower female reproductive tract repeatedly received challenge with a variable amount of in vitro simian immunodeficiency virus mac239–infected peripheral blood mononuclear cells. Persistent viremia was established with surprisingly few infectious lymphocytes containing physiologically relevant quantities of cell-associated virus. This model will be indispensable for the testing of vaccines and topical agents that are aimed toward the prevention of heterosexual transmission of HIV
ABSTRACT Human and simian immunodeficiency viruses (HIV and SIV) downregulate major histocompatibility complex class I (MHC-I) molecules from the surface of infected cells. Although this activity is conserved across viral isolates, its importance in AIDS pathogenesis is not clear. We therefore developed an assay to detect the level of MHC-I expression of SIV-infected cells directly ex vivo . Here we show that the extent of MHC-I downregulation is greatest in SIVmac239-infected macaques that never effectively control virus replication. Our results suggest that a high level of MHC-I downregulation is a hallmark of fast disease progression in SIV infection.
Adenovirus 5 (Ad5) vectors show promise as human immunodeficiency virus vaccine candidates. Indian rhesus macaques vaccinated with Ad5-gag controlled simian-human immunodeficiency virus SHIV89.6P viral replication in the absence of Env immunogens that might elicit humoral immunity. Here we immunized 15 macaques using either a homologous Ad5-gag/Ad5-gag (Ad5/Ad5) or a heterologous DNA-gag/Ad5-gag (DNA/Ad5) prime-boost regimen and challenged them with a high dose of simian immunodeficiency virus SIVmac239. Macaques vaccinated with the DNA/Ad5 regimen experienced a brief viral load nadir of less than 10,000 viral copies per ml blood plasma that was not seen in Mamu-A*01-negative DNA/Ad5 vaccinees, Mamu-A*01-positive Ad5/Ad5 vaccinees, or vaccine-naive controls. Interestingly, most of these animals were not durably protected from disease progression when challenged with SIVmac239. To investigate the reasons underlying this short-lived vaccine effect, we investigated breadth of the T-cell response, immunogenetic background, and viral escape from CD8+ lymphocytes that recognize immunodominant T-cell epitopes. We show that these animals do not mount unusually broad cellular immune response, nor do they express unusual major histocompatibility complex class I alleles. Viral recrudescence occurred in four of the five Mamu-A*01-positive vaccinated macaques. However, only a single animal in this group demonstrated viral escape in the immunodominant Gag181-189 CM9 response. These results suggest that viral "breakthrough" in vaccinated animals and viral escape are not inextricably linked and underscore the need for additional research into the mechanisms of vaccine failure.
Epitope-specific CD8+ T lymphocytes may play an important role in controlling human immunodeficiency virus (HIV)/simian immunodeficiency virus replication. Unfortunately, standard cellular assays do not measure the antiviral efficacy (the ability to suppress virus replication) of CD8+ T lymphocytes. Certain epitope-specific CD8+ T lymphocytes may be better than others at suppressing viral replication. We compared the antiviral efficacy of two immunodominant CD8+ T lymphocyte responses--Tat(28-35)SL8 and Gag(181-189)CM9--by using a functional in vitro assay. Viral suppression by Tat-specific CD8+ T lymphocytes was consistently greater than that of Gag-specific CD8+ T lymphocytes. Such differences in antigen-specific CD8+-T-lymphocyte efficacy may be important for selecting CD8+ T lymphocyte epitopes for inclusion in future HIV vaccines.
e14602 Background: In part (P) 1 and P2 of LUC1001 (NCT02908906), the RP2D of intravenous (IV) CET was established as 240 mg IV once every 2 weeks (Q2W) or 480 mg IV Q4W, and the PK/PD characteristics, safety profile, and clinical activity were consistent with known and approved PD-1 inhibitors (Felip et al. Cancer Chemother Pharmacol 2022). CET administered SC was investigated in P3 and P4 of LUC1001. Methods: In P3 and P4 of LUC1001, safety, PK, PD, and clinical activity of low- (30 mg/mL [CET-LC]) and high- (150 mg/mL [CET-HC]) concentration SC CET formulations, respectively, were evaluated. Key entry criteria were advanced or refractory solid tumors, previous receipt of or ineligibility for standard treatment, and being anti-PD-1/PD-L1/2–naïve. In P3, SC CET-LC injection was administered at a dose level of 600 mg with a 6-week dosing interval between doses 1 and 2, then Q3W dosing after dose 2. In P4, SC CET-HC injection was administered as a single loading dose of 900 mg, followed by 600 mg Q3W. Results: Among 30 enrolled pts (P3: n = 11; P4: n = 19), median age was 54.5 years; 17 (57%) were male; most (29 [97%]) were White and heavily pretreated, with a median of 3 (range, 1-8) prior lines of therapy. Most common tumor types were colorectal cancer (6 [20%]), breast cancer (4 [13%]), cholangiocarcinoma and NSCLC (3 [10%] each). Most commonly reported adverse events (AE) were fatigue (11 [37%]), ALT increased (7 [23%]), abdominal pain, constipation and AST increased (6 [20%] each). Overall, 20 (67%) pts had CET-related AEs, 1 (3%) of which led to CET discontinuation. Eight (27%) pts had ≥1 CET-related ≥Grade 3 AE. Immune-related AEs were reported in 9 (30%) pts. No pts experienced systemic-administration–related reactions, and 2 (6%) pts experienced Grade 1 administration-site reactions. No CET-related serious AEs were reported. Durable responses were observed in 2 (7%) patients (cholangiocarcinoma in P3 and thymoma in P4). Stable disease ≥24 weeks was observed in 4 (13% [P3, 0 (0%); P4, 4 (21%)]) pts. According to PK data, the 900-mg SC CET loading dose followed by 600-mg SC CET Q3W would likely result in comparable exposure as observed at steady state with IV RP2Ds. No differences in PK, including absorption, were observed between CET-LC and CET-HC formulations. Maximum PD-1 receptor occupancy was achieved, consistent with historical IV and SC data. Incidence of anti-CET antibodies (P3, 3/11 [27%]; P4, 0/13 [0%]) was low, and no neutralizing antibodies (0/24 [0%]) were detected. Conclusions: SC CET demonstrated a safety profile similar to IV CET. Based on safety, PK, and PD data, the RP2D of SC CET was established as a loading dose of 900 mg followed by 600 mg Q3W. Studies are planned to further evaluate the safety and efficacy of SC CET in combination with other agents. Clinical trial information: NCT02908906 .
BackgroundIt is generally accepted that CD8+ T cell responses play an important role in control of immunodeficiency virus replication. The association of HLA-B27 and -B57 with control of viremia supports this conclusion. However, specific correlates of viral control in individuals expressing these alleles have been difficult to define. We recently reported that transient in vivo CD8+ cell depletion in simian immunodeficiency virus (SIV)-infected elite controller (EC) macaques resulted in a brief period of viral recrudescence. SIV replication was rapidly controlled with the reappearance of CD8+ cells, implicating that these cells actively suppress viral replication in ECs.Methods and FindingsHere we show that three ECs in that study made at least seven robust CD8+ T cell responses directed against novel epitopes in Vif, Rev, and Nef restricted by the MHC class I molecule Mamu-B*08. Two of these Mamu-B*08-positive animals subsequently lost control of SIV replication. Their breakthrough virus harbored substitutions in multiple Mamu-B*08-restricted epitopes. Indeed, we found evidence for selection pressure mediated by Mamu-B*08-restricted CD8+ T cells in all of the newly identified epitopes in a cohort of chronically infected macaques.ConclusionsTogether, our data suggest that Mamu-B*08-restricted CD8+ T cell responses effectively control replication of pathogenic SIVmac239. All seven regions encoding Mamu-B*08-restricted CD8+ T cell epitopes also exhibit amino acid replacements typically seen only in the presence of Mamu-B*08, suggesting that the variation we observe is indeed selected by CD8+ T cell responses. SIVmac239 infection of Indian rhesus macaques expressing Mamu-B*08 may therefore provide an animal model for understanding CD8+ T cell-mediated control of HIV replication in humans.
Certain major histocompatibility complex (MHC) class I alleles are associated with the control of human immunodeficiency virus and simian immunodeficiency virus (SIV) replication. We have designed sequence-specific primers for detection of the rhesus macaque MHC class I allele Mamu-B*08 by PCR and screened a cohort of SIV-infected macaques for this allele. Analysis of 196 SIV(mac)239-infected Indian rhesus macaques revealed that Mamu-B*08 was significantly overrepresented in elite controllers; 38% of elite controllers were Mamu-B*08 positive compared to 3% of progressors (P = 0.00001). Mamu-B*08 was also associated with a 7.34-fold decrease in chronic phase viremia (P = 0.002). Mamu-B*08-positive macaques may, therefore, provide a good model to understand the correlates of MHC class I allele-associated immune protection and viral containment in human elite controllers.
Abstract Background: Blockade of the CTLA-4 pathway with ipilimumab (IPI) as monotherapy or in combination with nivolumab (anti–PD-1) is an effective treatment for a variety of cancers. Antibody-dependent cellular cytotoxicity (ADCC) is a cellular process through which effector immune cells that express an Fc receptor (FcR) recognize and eliminate antibody-bound targets. Anti–CTLA-4 has been shown to mediate the ADCC depletion of tumor-infiltrating regulatory T cells (Tregs), which play an important role in suppressing antitumor immune response in the tumor microenvironment. A version of IPI that is nonfucosylated (NF) in the Fc region (BMS-986218; anti–CTLA-4 NF) was created to increase binding affinity to activating Fcγ receptors (FcγR, CD16) and improve ADCC, thus increasing intratumoral Treg depletion. Methods: Antibody binding to CD16 was studied by surface plasmon resonance. IL-2 release from staphylococcal enterotoxin B (SEB)–stimulated normal human peripheral blood mononuclear cells (PBMCs) and CD4+ T cells was measured; ADCC function was evaluated by IL-2–activated NK cell–induced lysis of CD4+ T cells or activated CD4+Foxp3+ Tregs. Tumor growth was measured in transgenic (human CD16) mice implanted with MC38 tumors. Peripheral pharmacodynamics (PD) was evaluated in cynomolgus (CYNO) macaques after administration of customized adenovirus-5 vector vaccines. Results: Binding affinity to human CD16 was enhanced by BMS-986218 compared with IPI. BMS-986218 induced greater NK cell–mediated lysis of CD4+ T cells (37%) and Tregs (100%) compared with that induced by IPI (7% and 58%, respectively). Anti–CTLA-4 NF was also more effective than IPI in enhancing IL-2 release from SEB-stimulated PBMCs. Addition of an anti-CD16 antibody blocked the IL-2 response, supporting the concept that CD16 was necessary for anti–CTLA-4 NF activity. In mice, anti–CTLA-4 NF produced greater dose-dependent tumor growth inhibition (99%) than anti–CTLA-4 (61%). Tumors from anti–CTLA-4 NF–treated mice compared with anti–CTLA-4–treated mice had a greater decrease in Treg levels (70% vs 30%, respectively) and a larger increase in CD8+ T-cell levels (82% vs 62%, respectively) and no changes in Treg or CD8+ cell levels in the spleen. A more pronounced vaccine-induced T-cell response in anti–CTLA-4 NF–treated vs anti–CTLA-4–treated CYNO macaques was observed over a 3-week period. Conclusions: Nonfucosylation of an anti–CTLA-4 antibody increased binding affinity to CD16, induced depletion of Tregs while increasing T-effector cells in mouse tumors, and enhanced tumor growth inhibition in a dose-dependent manner, thus demonstrating improved ADCC compared with IPI. An ongoing phase 1/2 study is evaluating the safety and antitumor activity of anti–CTLA-4 NF alone and in combination with nivolumab (NCT03110107) in patients with advanced solid cancers. Citation Format: John Engelhardt, Rahima Akter, John Loffredo, Paula So, Natalie Bezman, Karen Price. Preclinical characterization of BMS-986218, a novel nonfucosylated anti–CTLA-4 antibody designed to enhance antitumor activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4552.
