Virus-Specific T Cells for the Immunocompromised Patient

Challenges of CAR- and TCR-T cell-based therapy for chronic infections

While therapy with T cells engineered with a chimeric antigen receptor (CAR) or a classical T cell receptor (TCR) is revolutionizing cancer treatment, its adoption in infectious diseases has been met with considerable resistance. Can we find its value for the cure of infections?

Cytomegalovirus Infection in Solid Organ and Hematopoietic Cell Transplantation: State of the Evidence

This review focuses on recent advances in the field of cytomegalovirus (CMV). The 2 main strategies for CMV prevention are prophylaxis and preemptive therapy. Prophylaxis effectively prevents CMV infection after solid organ transplantation (SOT) but is associated with high rates of neutropenia and delayed-onset postprophylaxis disease. In contrast, preemptive therapy has the advantage of leading to lower rates of CMV disease and robust humoral and T-cell responses. It is widely used in hematopoietic cell transplant recipients but is infrequently utilized after SOT due to logistical considerations, though these may be overcome by novel methods to monitor CMV viremia using self-testing platforms. We review recent developments in CMV immune monitoring, vaccination, and monoclonal antibodies, all of which have the potential to become part of integrated strategies that rely on viral load monitoring and immune responses. We discuss novel therapeutic options for drug-resistant or refractory CMV infection, including maribavir, letermovir, and adoptive T-cell transfer. We also explore the role of donor factors in transmitting CMV after SOT. Finally, we propose a framework with which to approach CMV prevention in the foreseeable future.

EBV-directed viral-specific T-lymphocyte therapy for the treatment of EBV-driven lymphoma in two patients with primary immunodeficiency and DNA repair defects

Children with ataxia telangiectasia (AT), a primary immunodeficiency caused by mutations in ATM, which is critical for repairing DNA defects, are at risk for the development of hematologic malignancy, frequently driven by infection with Epstein-Barr virus (EBV). Conventional chemotherapy is poorly tolerated by patients with AT, with excessive toxicity even when doses are reduced. Here, we report on two patients with AT and EBV-positive neoplasms who were treated with EBV-targeted viral-specific T cells (VST). One patient had a prolonged complete response to VSTs while the other had a partial response. Therapy was well tolerated without infusion toxicity or graft-versus-host disease.

Characterization of a Cytomegalovirus-Specific T Lymphocyte Product Obtained Through a Rapid and Scalable Production Process for Use in Adoptive Immunotherapy

Immunosuppressed patients are susceptible to virus reactivation or de novo infection. Adoptive immunotherapy, based on virus-specific T lymphocytes (VST), can prevent or treat viral diseases. However, donor availability, HLA-compatibility restrictions, high costs, and time required for the production of personalized medicines constitute considerable limitations to this treatment. Ex vivo rapid and large-scale expansion of VST, compliant with current good manufacturing practice (cGMP) standards, with an associated cell donor registry would overcome these limitations. This study aimed to characterize a VST product obtained through an expansion protocol transferable to cGMP standards. Antigenic stimulus consisted of cytomegalovirus (CMV) pp65 peptide pool-pulsed autologous dendritic cells (DCs) derived from monocytes. G-Rex technology, cytokines IL-2, IL-7, and IL-15, and anti-CD3 and anti-CD28 antibodies were used for culture. At day 14 of cell culture, the final product was characterized regarding T cell subsets, specificity, and functionality. The final product, comprised mainly CD4⁺ and CD8⁺ T lymphocytes (49.2 ± 24.7 and 42.3 ± 25.2, respectively). The culture conditions made it possible to achieve at least a 98.89-fold increase in pp65-specific CD3⁺ IFN-γ⁺ cells. These cells were specific, as pp65-specific cytotoxicity was demonstrated. Additionally, in complete HLA mismatch and without the presence of pp65, alloreactivity resulted in <5% cell lysis. In conclusion, a cGMP scalable process for the generation of a large number of doses of CMV-specific cytotoxic T cells was successfully performed.

Aspergillus fumigatus and Aspergillosis in 2019

Aspergillus fumigatus is a saprotrophic fungus; its primary habitat is the soil. In its ecological niche, the fungus has learned how to adapt and proliferate in hostile environments. This capacity has helped the fungus to resist and survive against human host defenses and, further, to be responsible for one of the most devastating lung infections in terms of morbidity and mortality. In this review, we will provide (i) a description of the biological cycle of A. fumigatus; (ii) a historical perspective of the spectrum of aspergillus disease and the current epidemiological status of these infections; (iii) an analysis of the modes of immune response against Aspergillus in immunocompetent and immunocompromised patients; (iv) an understanding of the pathways responsible for fungal virulence and their host molecular targets, with a specific focus on the cell wall; (v) the current status of the diagnosis of different clinical syndromes; and (vi) an overview of the available antifungal armamentarium and the therapeutic strategies in the clinical context. In addition, the emergence of new concepts, such as nutritional immunity and the integration and rewiring of multiple fungal metabolic activities occurring during lung invasion, has helped us to redefine the opportunistic pathogenesis of A. fumigatus.

Donor Allospecific CD44high Central Memory T Cells Have Decreased Ability to Mediate Graft-vs.-Host Disease

Data from both animal models and humans have demonstrated that effector memory T cells (T_EM) and central memory T cells (T_CM) from unprimed donors have decreased ability to induce graft-vs-host disease (GVHD). Allospecific T_EM from primed donors do not mediate GVHD. However, the potential of alloreactive T_CM to induce GVHD is not clear. In this study, we sought to answer this question using a novel GVHD model induced by T cell receptor (TCR) transgenic OT-II T cells. Separated from OT-II mice immunized with OVA protein 8 weeks earlier, the allospecific CD44^high T_CM were able to mediate skin graft rejection after transfer to naive mice, yet had dramatically decreased ability to induce GVHD. We also found that these allospecific CD44^high T_CM persisted in GVHD target organs for more than 30 days post-transplantation, while the expansion of these cells was dramatically decreased during GVHD, suggesting an anergic or exhausted state. These observations provide insights into how allospecific CD4⁺ T_CM respond to alloantigen during GVHD and underscore the fundamental difference of alloresponses mediated by allospecific T_CM in graft rejection and GVHD settings.

Chimeric Antigen Receptors for T-Cell Malignancies

Development of chimeric antigen receptor (CAR)-modified T cells for the treatment of T-lineage leukemia and lymphoma has encountered several unique challenges. The most widely expressed tumor antigen targets for malignant T cells are often also expressed on non-malignant T cells. Transducing T cells with CARs targeted to these shared antigens can therefore promote over-activation or fratricide of CAR T cells, reducing their therapeutic potency. If fratricide is resolved, clinical CAR T cell activity may eliminate normal T-cell subsets and cause temporary immunosuppression. In this review, we summarize the preclinical development of CAR-based therapies for T-cell malignancies and discuss strategies to minimize toxicities associated with on-target fratricide and off-tumor activity.

Adverse Effects of Virus-Specific T-Cell Therapy: An Integrative Review

Allogeneic hematopoietic stem cell transplant (HSCT) remains the mainstay in treating many hematologic malignancies. T-cell-depleted grafts designed to reduce graft-vs.-host disease (GVHD) may be complicated by severe viral infections that increase morbidity and mortality. Despite the use of antiviral pharmacologic therapy, challenges in controlling viral infections include drug resistance and/or side-effect intolerability. Virus-specific T-cell (VST) therapy is a promising targeted therapy for treating severe or drug-refractory viral infections after HSCT. An integrative review was conducted to inform advanced practitioners of the adverse effects associated with VST. A total of 836 articles were identified using PubMed, Scopus, and CINAHL databases, with 7 included in this review. Studies reviewed indicate that the adverse effects associated with VST therapy are limited and generally treatable. These studies reported low rates of adverse events of mild to moderate severity, including acute, recurrent, chronic, and de novo GVHD; cytokine release syndrome; infusion toxicity; and other adverse events. No deaths were attributed to VSTs in these studies.

Treatment and Prevention of CMV Disease in Transplant Recipients: Current Knowledge and Future Perspectives

This review summarizes the significant impact of cytomegalovirus (CMV) infection on solid organ and hematopoietic stem cell transplant recipients. A discussion of the various CMV prevention and treatment strategies is provided, including a detailed description of each of the available CMV antiviral drugs.

Levels of anti-CMV antibodies are modulated by the frequency and intensity of virus reactivations in kidney transplant patients

Anti-CMV (cytomegalovirus) antibody titers are related to immune alterations and increased risk of mortality. To test whether they represent a marker of infection history, we analyzed the effect of viral reactivations on the production of specific antibodies in kidney transplant patients. We quantified CMV-DNAemia and antibody titers in 58 kidney transplant patients before transplantation and during a follow-up of 315 days (standard deviation, SD: 134.5 days). In order to calculate the intensity of the infection, we plotted the follow-up time of the infection on the x-axis and the number of DNA-CMV copies on the y-axis and calculated the area under the curve (CMV-AUC). The degree of T-lymphocyte differentiation was analyzed with flow cytometry, the cells were labelled with different monoclonal antibodies in order to distinguish their differentiation state, from naive T-cells to senescent T-cells. Peak viremia was significantly higher in patients experiencing a primary infection (VI) compared to patients experiencing viral reactivation (VR). Our data indicate that the overall CMV viral load over the course of a primary infection is significantly higher than in a reactivation of a previously established infection. Whereas patients who experienced an episode of CMV reactivation during the course of our observation showed increased levels of CMV-specific antibodies, patients who did not experience CMV reactivation (WVR) showed a drop in CMV antibody levels that corresponds to an overall drop in antibody levels, probably due to the continuing immunosuppression after the renal transplant. We found a positive correlation between the CMV viremia over the course of the infection or reactivation and the CMV-specific antibody titers in the examined patients. We also observed a positive correlation between anti-CMV titers and T-cell differentiation. In conclusion, our data show that anti-CMV antibody titers are related to the course of CMV infection in kidney transplant patients.