To understand how natural sooty mangabey hosts avoid AIDS despite high levels of simian immunodeficiency virus (SIV) SIVsm replication, we inoculated mangabeys and nonnatural rhesus macaque hosts with an identical inoculum of uncloned SIVsm. The unpassaged virus established infection with high-level viral replication in both macaques and mangabeys. A species-specific, divergent immune response to SIV was evident from the first days of infection and maintained in the chronic phase, with macaques showing immediate and persistent T-cell proliferation, whereas mangabeys displayed little T-cell proliferation, suggesting subdued cellular immune responses to SIV. Importantly, only macaques developed CD4؉ -T-cell depletion and AIDS, thus indicating that in mangabeys limited immune activation is a key mechanism to avoid immunodeficiency despite high levels of SIVsm replication. These studies demonstrate that it is the host response to infection, rather than properties inherent to the virus itself, that causes immunodeficiency in SIV-infected nonhuman primates.

Relapsed T-cell malignancies have poor outcomes when treated with chemotherapy, but survival after allogeneic bone marrow transplantation (BMT) approaches 50%. A limitation to BMT is the difficulty of achieving remission prior to transplant. Chimeric antigen receptor (CAR) T-cell therapy has shown successes in B-cell malignancies. This approach is difficult to adapt for the treatment of T-cell disease due to lack of a T-lymphoblast specific antigen and the fratricide of CAR T cells that occurs with T-cell antigen targeting. To circumvent this problem two approaches were investigated. First, a natural killer (NK) cell line, which does not express CD5, was used for CAR expression. Second, CRISPR-Cas9 genome editing technology was used to knockout CD5 expression in CD5-positive Jurkat T cells and in primary T cells, allowing for the use of CD5-negative T cells for CAR expression. Two structurally distinct anti-CD5 sequences were also tested, i) a traditional immunoglobulin-based single chain variable fragment (scFv) and ii) a lamprey-derived variable lymphocyte receptor (VLR), which we previously showed can be used for CAR-based recognition. Our results show i) both CARs yield comparable T-cell activation and NK cell-based cytotoxicity when targeting CD5-positive cells, ii) CD5-edited CAR-modified Jurkat T cells have reduced self-activation compared to that of CD5-positive CAR-modified T cells, iii) CD5-edited CAR-modified Jurkat T cells have increased activation in the presence of CD5-positive target cells compared to that of CD5-positive CAR-modified T cells, and iv) although modest effects were seen, a mouse model using the CAR-expressing NK cell line showed the scFv-CAR was superior to the VLR-CAR in delaying disease progression.

Current limitations in using chimeric antigen receptor T(CART) cells to treat patients with hematological cancers include limited expansion and persistence in vivo that contribute to cancer relapse. Patients with chronic lymphocytic leukemia (CLL) have terminally differentiated T cells with an exhausted phenotype and experience low complete response rates after autologous CART therapy. Because PI3K inhibitor therapy is associated with the development of T-cell–mediated autoimmunity, we studied the effects of inhibiting the PI3Kδ and PI3Kγ isoforms during the manufacture of CART cells prepared from patients with CLL. Dual PI3Kδ/γ inhibition normalized CD4/CD8 ratios and maximized the number of CD8+ T-stem cell memory, naive, and central memory T-cells with dose-dependent decreases in expression of the TIM-3 exhaustion marker. CART cells manufactured with duvelisib (Duv-CART cells) showed significantly increased in vitro cytotoxicity against CD19+ CLL targets caused by increased frequencies of CD8+ CART cells. Duv-CART cells had increased expression of the mitochondrial fusion protein MFN2, with an associated increase in the relative content of mitochondria. Duv-CART cells exhibited increased SIRT1 and TCF1/7 expression, which correlated with epigenetic reprograming of Duv-CART cells toward stem-like properties. After transfer to NOG mice engrafted with a human CLL cell line, Duv-CART cells expressing either a CD28 or 41BB costimulatory domain demonstrated significantly increased in vivo expansion of CD8+ CART cells, faster elimination of CLL, and longer persistence. Duv-CART cells significantly enhanced survival of CLL-bearing mice compared with conventionally manufactured CART cells. In summary, exposure of CART to a PI3Kδ/γ inhibitor during manufacturing enriched the CART product for CD8+ CART cells with stem-like qualities and enhanced efficacy in eliminating CLL in vivo.