Chemoprophylaxis Vaccination: Phase I Study to Explore Stage-specific Immunity to Plasmodium falciparum in US Adults.

BACKGROUND: Chemoprophylaxis vaccination with sporozoites (CVac) with chloroquine induces protection against a homologous Plasmodium falciparum sporozoite (PfSPZ) challenge, but whether blood-stage parasite exposure is required for protection remains unclear. Chloroquine suppresses and clears blood-stage parasitemia, while other antimalarial drugs, such as primaquine, act against liver-stage parasites. Here, we evaluated CVac regimens using primaquine and/or chloroquine as the partner drug to discern whether blood-stage parasite exposure impacts protection against homologous controlled human malaria infection. METHODS: In a Phase I, randomized, partial double-blind, placebo-controlled study of 36 malaria-naive adults, all CVac subjects received chloroquine prophylaxis and bites from 12-15 P. falciparum-infected mosquitoes (CVac-chloroquine arm) at 3 monthly iterations, and some received postexposure primaquine (CVac-primaquine/chloroquine arm). Drug control subjects received primaquine, chloroquine, and uninfected mosquito bites. After a chloroquine washout, subjects, including treatment-naive infectivity controls, underwent homologous, PfSPZ controlled human malaria infection and were monitored for parasitemia for 21 days. RESULTS: No serious adverse events occurred. During CVac, all but 1 subject in the study remained blood-smear negative, while only 1 subject (primaquine/chloroquine arm) remained polymerase chain reaction-negative. Upon challenge, compared to infectivity controls, 3/3 chloroquine arm subjects displayed delayed patent parasitemia (P = .01) but not sterile protection, while 3/11 primaquine/chloroquine subjects remained blood-smear negative. CONCLUSIONS: CVac-primaquine/chloroquine is safe and induces sterile immunity to P. falciparum in some recipients, but a single 45 mg dose of primaquine postexposure does not completely prevent blood-stage parasitemia. Unlike previous studies, CVac-chloroquine did not produce sterile immunity. CLINICAL TRIALS REGISTRATION: NCT01500980.

Preemptive mitigation of CD19 CAR T-cell cytokine release syndrome without attenuation of antileukemic efficacy.

Immunotherapy with the adoptive transfer of T cells redirected with CD19-specific chimeric antigen receptors (CARs) for B-lineage acute lymphoblastic leukemia (ALL) can salvage >80% of patients having relapsed/refractory disease. The therapeutic index of this emerging modality is attenuated by the occurrence of immunologic toxicity syndromes that occur upon CAR T-cell engraftment. Here, we report on the low incidence of severe cytokine release syndrome (CRS) in a subject treated with a CAR T-cell product composed of a defined ratio CD4:CD8 T-cell composition with a 4-1BB:zeta CAR targeting CD19 who also recieved early intervention treatment. We report that early intervention with tocilizumab and/or corticosteroids may reduce the frequency at which subjects transition from mild CRS to severe CRS. Although early intervention doubled the numbers of subjects dosed with tocilizumab and/or corticosteroids, there was no apparent detrimental effect on minimal residual disease-negative complete remission rates or subsequent persistence of functional CAR T cells compared with subjects who did not receive intervention. Moreover, early intervention therapy did not increase the proportion of subjects who experience neurotoxicity or place subjects at risk for infectious sequelae. These data support the contention that early intervention with tocilizumab and/or corticosteroids in subjects with early signs of CRS is without negative impact on the antitumor potency of CD19 CAR T cells. This intervention serves to enhance the therapeutic index in relapsed/refractory patients and provides the rationale to apply CAR T-cell therapy more broadly in ALL therapy. This trial was registered at www.clinicaltrials.gov as #NCT020284.

Glial injury in neurotoxicity after pediatric CD19-directed chimeric antigen receptor T cell therapy.

OBJECTIVE: To test whether systemic cytokine release is associated with central nervous system inflammatory responses and glial injury in immune effector cell-associated neurotoxicity syndrome (ICANS) after chimeric antigen receptor (CAR)-T cell therapy in children and young adults. METHODS: We performed a prospective cohort study of clinical manifestations as well as imaging, pathology, CSF, and blood biomarkers on 43 subjects ages 1 to 25 who received CD19-directed CAR/T cells for acute lymphoblastic leukemia (ALL). RESULTS: Neurotoxicity occurred in 19 of 43 (44%) subjects. Nine subjects (21%) had CTCAE grade 3 or 4 neurological symptoms, with no neurotoxicity-related deaths. Reversible delirium, headache, decreased level of consciousness, tremor, and seizures were most commonly observed. Cornell Assessment of Pediatric Delirium (CAPD) scores ≥9 had 94% sensitivity and 33% specificity for grade ≥3 neurotoxicity, and 91% sensitivity and 72% specificity for grade ≥2 neurotoxicity. Neurotoxicity correlated with severity of cytokine release syndrome, abnormal past brain magnetic resonance imaging (MRI), and higher peak CAR-T cell numbers in blood, but not cerebrospinal fluid (CSF). CSF levels of S100 calcium-binding protein B and glial fibrillary acidic protein increased during neurotoxicity, indicating astrocyte injury. There were concomitant increases in CSF white blood cells, protein, interferon-γ (IFNγ), interleukin (IL)-6, IL-10, and granzyme B (GzB), with concurrent elevation of serum IFNγ IL-10, GzB, granulocyte macrophage colony-stimulating factor, macrophage inflammatory protein 1 alpha, and tumor necrosis factor alpha, but not IL-6. We did not find direct evidence of endothelial activation. INTERPRETATION: Our data are most consistent with ICANS as a syndrome of systemic inflammation, which affects the brain through compromise of the neurovascular unit and astrocyte injury. ANN NEUROL 2019.

CD19 CAR T cell product and disease attributes predict leukemia remission durability.

BACKGROUND: Chimeric antigen receptor (CAR) T cells can induce remission in highly refractory leukemia and lymphoma subjects, yet the parameters for achieving sustained relapse-free survival are not fully delineated. METHODS: We analyzed 43 pediatric and young adult subjects participating in a Phase I trial of defined composition CD19CAR T cells (NCT02028455). CAR T cell phenotype, function and expansion, as well as starting material T cell repertoire, were analyzed in relation to therapeutic outcome (defined as achieving complete remission within 63 days) and duration of leukemia free survival and B cell aplasia. RESULTS: These analyses reveal that initial therapeutic failures (n = 5) were associated with attenuated CAR T cell expansion and/or rapid attrition of functional CAR effector cells following adoptive transfer. The CAR T products were similar in phenotype and function when compared to products resulting in sustained remissions. However, the initial apheresed peripheral blood T cells could be distinguished by an increased frequency of LAG-3+/TNF-αlow CD8 T cells and, following adoptive transfer, the rapid expression of exhaustion markers. For the 38 subjects who achieved an initial sustained MRD-neg remission, remission durability correlated with therapeutic products having increased frequencies of TNF-α-secreting CAR CD8+ T cells, and was dependent on a sufficiently high CD19+ antigen load at time of infusion to trigger CAR T cell proliferation. CONCLUSION: These parameters have the potential to prospectively identify patients at risk for therapeutic failure and support the development of approaches to boost CAR T cell activation and proliferation in patients with low levels of CD19 antigen. TRIAL REGISTRATION: ClinicalTrials.gov NCT02028455. FUNDING: Partial funding for this study was provided by Stand Up to Cancer & St. Baldrick's Pediatric Dream Team Translational Research Grant (SU2C-AACR-DT1113), RO1 CA136551-05, Alex Lemonade Stand Phase I/II Infrastructure Grant, Conquer Cancer Foundation Career Development Award, Washington State Life Sciences Discovery Fund, Ben Towne Foundation, William Lawrence & Blanche Hughes Foundation, and Juno Therapeutics, Inc., a Celgene Company.

Manufacture of Chimeric Antigen Receptor T Cells from Mobilized Cyropreserved Peripheral Blood Stem Cell Units Depends on Monocyte Depletion.

Cytotoxic chemotherapy and radiation can render lymphocyte repertoires qualitatively and quantitatively defective. Thus, heavily treated patients are often poor candidates for the manufacture of autologous chimeric antigen receptor (CAR)-T cell products. In the United States and Europe, children with high-risk neuroblastoma undergo apheresis early in the course of treatment to collect peripheral blood stem cells (PBSCs) for cryopreservation in preparation for high-dose chemotherapy followed by autologous stem cell rescue. Here, we investigate whether these cryopreserved chemotherapy and granulocyte colony-stimulating factor (G-CSF)-mobilized PBSCs can serve as starting material for CAR-T cell manufacturing. We evaluated T cell precursor subsets in cryopreserved PBSC units from 8 patients with neuroblastoma using fluorescent activated cell sorting-based analysis. Every cryopreserved unit collected early in treatment contained both CD4 and CD8 precursors with significant numbers of naïve and central memory precursors. Significant numbers of Ki67+/PD1+ T cells were detected, presumably the result of chemotherapy-induced lymphopenia and subsequent homeostatic proliferation. Cryopreserved PBSC units containing 56 to 112 × 106 T cells were amenable to immunomagnetic selection, CD3 × 28 bead activation, lentiviral transduction, and cytokine-driven expansion, provided that CD14 monocytes were depleted before the initiation of cultures. Second- and third-generation CD171 CAR+ CD4 and CD8 effector cells derived from cryopreserved units displayed antineuroblastoma lytic potency and cytokine secretion comparable to those derived from a healthy donor and mediated in vivo antitumor regression in NSG mice. We conclude that cryopreserved PBSCs procured via standard methods during early treatment can serve as an alternative starting source for CAR-T cell manufacturing, extending the options for heavily treated patients.

P. falciparum enhances HIV replication in an experimental malaria challenge system.

Co-infection with HIV and P. falciparum worsens the prognosis of both infections; however, the mechanisms driving this adverse interaction are not fully delineated. To evaluate this, we studied HIV-1 and P. falciparum interactions in vitro using peripheral blood mononuclear cells (PBMCs) from human malaria naïve volunteers experimentally infected with P. falciparum in a malaria challenge trial. PBMCs collected before the malaria challenge and at several time points post-infection were infected with HIV-1 and co-cultured with either P. falciparum infected (iRBCs) or uninfected (uRBCs) red blood cells. HIV p24Ag and TNF-α, IFN-γ, IL-4, IL-6, IL-10, IL-17, and MIP-1α were quantified in the co-culture supernatants. In general, iRBCs stimulated more HIV p24Ag production by PBMCs than did uRBCs. HIV p24Ag production by PBMCs in the presence of iRBCs (but not uRBCs) further increased during convalescence (days 35, 56, and 90 post-challenge). In parallel, iRBCs induced higher secretion of pro-inflammatory cytokines (TNF-α, IFN-γ, and MIP-1α) than uRBCs, and production increased further during convalescence. Because the increase in p24Ag production occurred after parasitemia and generalized immune activation had resolved, our results suggest that enhanced HIV production is related to the development of anti-malaria immunity and may be mediated by pro-inflammatory cytokines.

Phenotypic analysis of human peripheral blood regulatory T cells (CD4+FOXP3+CD127lo/-) ex vivo and after in vitro restimulation with malaria antigens.

Regulatory T cells (Treg) play crucial roles in regulating autoimmune responses and immunity to tumors and infectious diseases. However, numerous subpopulations of Treg are now being described and the utility of various Treg markers is being reassessed. Here we report the results of a detailed phenotypic comparison of two supposedly regulatory human T-cell populations, namely CD4+FOXP3+ T cells and CD4+CD25hi T cells. We find that CD4+FOXP3+ cells are extremely heterogeneous with respect to CD25 expression and that FOXP3+ and CD25hi CD4+ T cells differ in their expression of chemokine receptors (CCR), CD95 and Bcl-2, suggestive of distinct migration characteristics and susceptibility to apoptosis. Further, we propose that CD25 expression should be regarded as an activation marker rather than as a defining marker of Treg. Lastly, CD4+FOXP3+ T cells activated in vitro with malaria antigen expressed the highest levels of CCR4 and CD95, and the lowest levels of CCR7, indicating that they are most likely generated from effector memory cells during an immune response and rapidly succumb to apoptosis at the end of the response.