Isolation of highly suppressive CD25+FoxP3+ T regulatory cells from G-CSF-mobilized donors with retention of cytotoxic anti-viral CTLs: application for multi-functional immunotherapy post stem cell transplantation

Granulocyte Colony Stimulating Factor-Mobilized Peripheral Blood Mononuclear Cells: An Alternative Cellular Source for Chimeric Antigen Receptor Therapy

Lymphocyte collection by apheresis for CAR-T production usually does not include blood mobilized using granulocyte colony stimulating factor (G-CSF) due to the widespread knowledge that it causes a decrease in the number and functionality of lymphocytes. However, it is used for stem cell transplant, which is a common treatment for hematological malignancies. The growing demand for CAR therapies (CAR-T and NK-CAR), both in research and clinics, makes it necessary to evaluate whether mobilized PBSC products may be potential candidates for use in such therapies. This review collects recent works that experimentally verify the role and functionality of T and NK lymphocytes and the generation of CAR-T from apheresis after G-CSF mobilization. As discussed, T cells do not vary significantly in their phenotype, the ratio of CD4+ and CD8+ remains constant, and the different sub-populations remain stable. In addition, the expansion and proliferation rates are invariant regardless of mobilization with G-CSF as well as the secretion of proinflammatory cytokines and the cytotoxic ability. Therefore, cells mobilized before apheresis are postulated as a new alternative source of T cells for adoptive therapies that will serve to alleviate high demand, increase availability, and take advantage of the substantial number of existing cryopreserved products.

Is It Feasible to Use CMV-Specific T-Cell Adoptive Transfer as Treatment Against Infection in SOT Recipients?

During the last decade, many studies have demonstrated the role of CMV specific T-cell immune response on controlling CMV replication and dissemination. In fact, it is well established that transplanted patients lacking CMV-specific T-cell immunity have an increased occurrence of CMV replication episodes and CMV-related complications. In this context, the use of adoptive transfer of CMV-specific T-cells has been widely investigated and applied to Hematopoietic Stem Cell Transplant patients and may be useful as a therapeutic alternative, to reconstitute the CMV specific T-cell response and to control CMV viremia in patients receiving a transplantation. However, only few authors have explored the use of T-cell adoptive transfer in SOT recipients. We propose a novel review in which we provide an overview of the impact of using CMV-specific T-cell adoptive transfer on the control of CMV infection in SOT recipients, the different approaches to stimulate, isolate and expand CMV-specific T-cells developed over the years and a discussion of the possible use of CMV adoptive cellular therapy in this SOT population. Given the timeliness and importance of this topic, we believe that such an analysis will provide important insights into CMV infection and its treatment/prevention.

Advances in biomarker detection: Alternative approaches for blood-based biomarker detection

In the clinical setting, a blood sample is typically the starting point for biomarker search and discovery. Mass spectrometry (MS) is a highly sensitive and informative method for characterizing a very wide range of metabolites and proteins and is therefore a potentially powerful tool for biomarker discovery. However, the physicochemical characteristics of blood coupled with very large ranges of protein and metabolite concentrations present a significant technical obstacle for resolving and quantifying putative biomarkers by MS. Blood fractionation procedures are being developed to reduce the proteome/metabolome complexity and concentration ranges, allowing a greater diversity of analytes, including those at very low concentrations, to be quantified. In this chapter, several strategies for enriching and/or isolating specific blood components are summarized, including methods for the analysis of low and high molecular weight compounds, usually neglected in this type of assays, extracellular vesicles, and peripheral blood mononuclear cells (PBMCs). For each method, relevant practical information is presented for effective implementation.

A Native Human Monoclonal Antibody Targeting HCMV gB (AD-2 Site I)

Hyperimmune globulin (HIG) has shown efficacy against human cytomegalovirus (HCMV) for both transplant and congenital transmission indications. Replicating that activity with a monoclonal antibody (mAb) offers the potential for improved consistency in manufacturing, lower infusion volume, and improved pharmacokinetics, as well as reduced risk of off-target reactivity leading to toxicity. HCMV pathology is linked to its broad cell tropism. The glycoprotein B (gB) envelope protein is important for infections in all cell types. Within gB, the antigenic determinant (AD)-2 Site I is qualitatively more highly-conserved than any other region of the virus. TRL345, a high affinity (Kd = 50 pM) native human mAb to this site, has shown efficacy in neutralizing the infection of fibroblasts, endothelial and epithelial cells, as well as specialized placental cells including trophoblast progenitor cells. It has also been shown to block the infection of placental fragments grown ex vivo, and to reduce syncytial spread in fibroblasts in vitro. Manufacturing and toxicology preparation for filing an IND (investigational new drug) application with the US Food and Drug Administration (FDA) are expected to be completed in mid-2019.

Peripheral Blood or Bone Marrow Stem Cells? Practical Considerations in Hematopoietic Stem Cell Transplantation

Although peripheral blood stem cells (PBSC) have worldwide become the predominant source of progenitor cells for hematopoietic stem cell transplantation (HSCT), debate about their role compared with bone marrow (BM) has recently intensified, in large part based on the results of a multicenter Clinical Trials Network study which showed lower incidence of chronic graft-versus-host disease (cGVHD) and improved quality of life in recipients of myeloablative HLA-matched unrelated BM compared with PBSC transplants. However, in certain patient populations, PBSC may lead to improved clinical outcomes due to faster hematologic recovery, a lower risk of graft failure, and possibly a lower probability of relapse. This review will provide a comprehensive summary of studies comparing PBSC with BM as the graft source in terms of acute and chronic GVHD incidence, time to engraftment, and disease-free and overall survival probabilities after HLA-matched related and unrelated donor transplantation and haploidentical donor transplantation. Recommendations based on these studies regarding the use of PBSC versus BM for HSCT are offered.

Deregulated Mucosal Immune Surveillance through Gut-Associated Regulatory T Cells and PD-1+ T Cells in Human Colorectal Cancer

Disturbed balance between immune surveillance and tolerance may lead to poor clinical outcomes in some malignancies. In paired analyses of adenocarcinoma and normal mucosa from 142 patients, we found a significant increase of the CD4/CD8 ratio and accumulation of regulatory T cells (Tregs) within the adenocarcinoma. The increased frequency of Tregs correlated with the local infiltration and extension of the tumor. There was concurrent maturation arrest, upregulation of programmed death-1 expression, and functional impairment in CD8⁺ T cells (CTLs) isolated from the adenocarcinoma. Adenocarcinoma-associated Tregs directly inhibit the function of normal human CTLs in vitro. With histopathological analysis, Foxp3⁺ Tregs were preferentially located in stroma. Concurrent transcriptome analysis of epithelial cells, stromal cells, and T cell subsets obtained from carcinomatous and normal intestinal samples from patients revealed a distinct gene expression signature in colorectal adenocarcinoma-associated Tregs, with overexpression of CCR1, CCR8, and TNFRSF9, whereas their ligands CCL4 and TNFSF9 were found upregulated in cancerous epithelium. Overexpression of WNT2 and CADM1, associated with carcinogenesis and metastasis, in cancer-associated stromal cells suggests that both cancer cells and stromal cells play important roles in the development and progression of colorectal cancer through the formation of a tumor microenvironment. The identification of CTL anergy by Tregs and the unique gene expression signature of human Tregs and stromal cells in colorectal cancer patients may facilitate the development of new therapeutics against malignancies.

Preservation of Antigen-Specific Functions of αβ T Cells and B Cells Removed from Hematopoietic Stem Cell Transplants Suggests Their Use As an Alternative Cell Source for Advanced Manipulation and Adoptive Immunotherapy

Hematopoietic stem cell transplantation is standard therapy for numerous hematological diseases. The use of haploidentical donors, sharing half of the HLA alleles with the recipient, has facilitated the use of this procedure as patients can rely on availability of a haploidentical donor within their family. Since HLA disparity increases the risk of graft-versus-host disease, T-cell depletion has been used to remove alloreactive lymphocytes from the graft. Selective removal of αβ T cells, which encompass the alloreactive repertoire, combined with removal of B cells to prevent EBV-related lymphoproliferative disease, proved safe and effective in clinical studies. Depleted αβ T cells and B cells are generally discarded as by-products. Considering the possible use of donor T cells for donor lymphocyte infusions or for generation of pathogen-specific T cells as mediators of graft-versus-infection effect, we tested whether cells in the discarded fractions were functionally intact. Response to alloantigens and to viral antigens comparable to that of unmanipulated cells indicated a functional integrity of αβ T cells, in spite of the manipulation used for their depletion. Furthermore, B cells proved to be efficient antigen-presenting cells, indicating that antigen uptake, processing, and presentation were fully preserved. Therefore, we propose that separated αβ T lymphocytes could be employed for obtaining pathogen-specific T cells, applying available methods for positive selection, which eventually leads to indirect allodepletion. In addition, these functional T cells could undergo additional manipulation, such as direct allodepletion or genetic modification.

An innovative method to generate a Good Manufacturing Practice-ready regulatory T-cell product from non-mobilized leukapheresis donors

BACKGROUND AIMS

There is real and sustained interest in preparing T-regulatory cells from leukapheresis collections for cellular therapy through the use of simple, effective and reliable methods conforming to Good Manufacturing Practice (GMP). We describe a GMP-ready isolation procedure for CD25(+) products with the use of a sterile docking device, pigtail sampling, a laminar flow hood and the CliniMACS system that uses leukapheresis collections made by two apheresis machines.

METHODS

We used CD8/CD19 depletion followed by CD25-positive selection. The median number of CD4(+) cells recovered was 72.5 ± 32.6 × 10(6), of which 60.5% ± 17.8% were CD25(+)FOXP3(+) cells. Suppression of autologous CD25(-) cell proliferation by the cryopreserved CD25(+) products was 51.3% ± 4.4%, 49.0% ± 3.7% and 39.0% ± 3.6% at CD25(+):CD25(-) ratios of 1:1, 1:2 and 1:4 (n = 6), respectively, comparable to suppression by fresh CD25(+) products (53% ± 6.2%, 51% ± 3.3% and 39% ± 7.1%).

RESULTS

We found Leukapheresis collections by Cobe Spectra contained more lymphocytes and platelets than collections by Spectra Optia apheresis machine (median, 9.2 × 10(9) versus 6.7 × 10(9); P = 0.04) and platelets (median, 610 × 10(9) versus 170 × 10(9); P = 0.04). The frequency of CD4(+)CD25(+)FOXP3(+) was significantly higher in the leukapheresis (4.85%; 95% confidence interval, 1.95% to 5.38%) than in peripheral blood (3.9%; 95% confidence interval, 2.63% to 6.45%) (P = 0.02). The CD8- and CD19-negative depletion step was associated with significant loss of total CD4(+) T cells (P = 0.001).

CONCLUSIONS

Results suggest that functional CD25(+) products can be isolated with a GMP-ready method, and good recovery can be obtained with the use of an optimized cryopreservation protocol. These data and methods show the potential, possibilities and future work needed to isolate target cell populations in a reproducible, time-efficient and cost-efficient manner for clinical applications.

Assessment of the effector function of CMV-specific CTLs isolated using MHC-multimers from granulocyte-colony stimulating factor mobilized peripheral blood

BACKGROUND

Adoptive transfer of CMV-specific T cells has shown promising results in preventing pathological effects caused by opportunistic CMV infection in immunocompromised patients following allogeneic hematopoietic stem cell transplantation. The majority of studies have used steady-state leukapheresis for CMV-reactive product manufacture, a collection obtained prior to or months after G-CSF mobilization, but the procurement of this additional sample is often not available in the unrelated donor setting. If the cellular product for adoptive immunotherapy could be generated from the same G-CSF mobilized collection, the problems associated with the additional harvest could be overcome. Despite the tolerogenic effects associated with G-CSF mobilization, recent studies described that CMV-primed T cells generated from mobilized donors remain functional.

METHODS

MHC-multimers are potent tools that allow the rapid production of antigen-specific CTLs. Therefore, in the present study we have assessed the feasibility and efficacy of CMV-specific CTL manufacture from G-CSF mobilized apheresis using MHC-multimers.

RESULTS

CMV-specific CTLs can be efficiently isolated from G-CSF mobilized samples with Streptamers and are able to express activation markers and produce cytokines in response to antigenic stimulation. However, this anti-viral functionality is moderately reduced when compared to non-mobilized products.

CONCLUSIONS

The translation of Streptamer technology for the isolation of anti-viral CTLs from G-CSF mobilized PBMCs into clinical practice would widen the number of patients that could benefit from this therapeutic strategy, although our results need to be taken into consideration before the infusion of antigen-specific T cells obtained from G-CSF mobilized samples.

A high-affinity native human antibody neutralizes human cytomegalovirus infection of diverse cell types

Human cytomegalovirus (HCMV) is the most common infection causing poor outcomes among transplant recipients. Maternal infection and transplacental transmission are major causes of permanent birth defects. Although no active vaccines to prevent HCMV infection have been approved, passive immunization with HCMV-specific immunoglobulin has shown promise in the treatment of both transplant and congenital indications. Antibodies targeting the viral glycoprotein B (gB) surface protein are known to neutralize HCMV infectivity, with high-affinity binding being a desirable trait, both to compete with low-affinity antibodies that promote the transmission of virus across the placenta and to displace nonneutralizing antibodies binding nearby epitopes. Using a miniaturized screening technology to characterize secreted IgG from single human B lymphocytes, 30 antibodies directed against gB were previously cloned. The most potent clone, TRL345, is described here. Its measured affinity was 1 pM for the highly conserved site I of the AD-2 epitope of gB. Strain-independent neutralization was confirmed for 15 primary HCMV clinical isolates. TRL345 prevented HCMV infection of placental fibroblasts, smooth muscle cells, endothelial cells, and epithelial cells, and it inhibited postinfection HCMV spread in epithelial cells. The potential utility for preventing congenital transmission is supported by the blockage of HCMV infection of placental cell types central to virus transmission to the fetus, including differentiating cytotrophoblasts, trophoblast progenitor cells, and placental fibroblasts. Further, TRL345 was effective at controlling an ex vivo infection of human placental anchoring villi. TRL345 has been utilized on a commercial scale and is a candidate for clinical evaluation.