Cellular therapy for multiple pathogen infections after hematopoietic stem cell transplant

Diagnostic performance and clinical impacts of metagenomic sequencing after allogeneic hematopoietic stem cell transplantation

BACKGROUND

Metagenomic Next-Generation Sequencing (mNGS) is a rapid, non-culture-based, high-throughput technique for pathogen diagnosis. Despite its numerous advantages, only a few studies have investigated its use in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT).

METHODS

We conducted a retrospective analysis of 404 mNGS tests performed on 264 patients after allo-HSCT. The tests were divided into three groups (Phase A, B, C) based on the time spent hospitalized post-transplantation, and we evaluated the analytical performance of mNGS in comparison with conventional microbiological tests (CMT), while also analyzing its clinical utility for clinical impacts.

RESULTS

Metagenomic sequencing demonstrated a significantly higher rate of positive microbiological findings as compared to CMT (334/404 (82.7 %) vs. 159/404 (39.4 %), respectively, P < 0.001). The detection rates by both mNGS and CMT varied across the three-phase (mNGS: A-60/89 (67.4 %), B-147/158 (93.0 %), C-125/157 (79.6 %), respectively, P < 0.001; CMT: A-21/89 (23.6 %), B-79/158 (50.0 %), C-59/157 (37.6 %), respectively, P < 0.001). The infection sites and types of pathogens were also different across the three phases. Compared to non-GVHD cases, mNGS detected more Aspergillus spp. and Mucorales in GVHD patients (Aspergillus: 12/102 (11.8 %) vs. 8/158 (5.1 %), respectively, P = 0.048; Mucorales: 6/102 (5.9 %) vs. 2/158 (1.3 %), respectively, P = 0.035). Forty-five (181/404) percent of mNGS tests yielded a positive impact on the clinical diagnosis, while 24.3 % (98/404) of tests benefited the patients in antimicrobial treatment.

CONCLUSION

mNGS is an indispensable diagnostic tool in identifying pathogens and optimizing antibiotic therapy for hematological patients receiving allo-HSCT.

The effect of varicella-zoster virus reactivation on the long-term outcomes of patients undergoing allogeneic hematopoietic stem cell transplantation

BACKGROUND

A virus infection may lead the body to produce more immune cells of particular types or stimulate the production of new ones, both of which may have anti-leukemic effects. There has been no research on whether immune cells stimulated by varicella-zoster virus (VZV) infection have anti-leukemic effects. The objective of this investigation is to assess the impact of VZV infection on patients' long-term survival following allogeneic hematopoietic stem cell transplantation (allo-HSCT).

METHODS

This retrospective study investigated the association between varicella-zoster virus (VZV) reactivation and outcomes in 219 individuals who received allogeneic hematopoietic stem cell transplantation (allo-HSCT) at the Sun Yat-sen University's First Affiliated Hospital. According to being diagnosed with VZV infection or not, these patients were grouped into two groups. The comparison of cumulative incidence of relapse, non-recurrent mortality, and overall survival (OS) was conducted between the two groups.

RESULTS

Analyzing multivariate data, VZV reactivation was linked to lower relapse incidence in the group containing all individuals (hazard ratio [HR] = 0.27; 95% confidence interval [CI], 0.12-0.64), patients suffering from acute myeloid leukaemia (HR = 0.10; 95% CI, 0.01-0.83), and patients suffering from acute lymphoblastic leukaemia (HR = 0.25; 95% CI, 0.08-0.77). Moreover, VZV reactivation was linked with decreased non-relapse mortality in all individuals (HR = 0.20; 95% CI, 0.05-0.79), but no statistical significance was found for any disease subgroup. Further, VZV reactivation was an independent predictor for improved OS in the group containing all individuals (HR = 0.10; 95% CI, 0.03-0.29), patients suffering from acute myeloid leukaemia (HR = 0.09; 95% CI, 0.01-0.66), and patients suffering from acute lymphoblastic leukaemia (HR = 0.16; 95% CI, 0.04-0.68).

CONCLUSION

This is the first study to show that VZV reactivation following allo-HSCT is an independent predictor for lower relapse rates and improved OS, providing novel therapeutic approaches to improve patients' long-term survival following allo-HSCT.

Potency assessment of IFNγ-producing SARS-CoV-2-specific T cells from COVID-19 convalescent subjects

The development of new therapies for COVID-19 high-risk patients remains necessary to prevent additional deaths. Here, we studied the phenotypical and functional characteristics of IFN-γ producing-SARS-CoV-2-specific T cells (SC2-STs), obtained from 12 COVID-19 convalescent donors, to determine their potency as an off-the-shelf T cell therapy product. We found that these cells present mainly an effector memory phenotype, characterized by the basal expression of cytotoxicity and activation markers, including granzyme B, perforin, CD38, and PD-1. We demonstrated that SC2-STs could be expanded and isolated in vitro, and they exhibited peptide-specific cytolytic and proliferative responses after antigenic re-challenge. Collectively, these data demonstrate that SC2-STs can be a suitable candidate for the manufacture of a T cell therapy product aimed to treat severe COVID-19.

Cytokine Release Syndrome and Sepsis: Analogous Clinical Syndromes with Distinct Causes and Challenges in Management

Both cytokine release syndrome (CRS) and sepsis are clinical syndromes rather than distinct diseases and share considerable overlap. It can often be challenging to distinguish between the two, but it is important given the availability of targeted treatment options. In addition, several other clinical syndromes overlap with CRS and sepsis, further making it difficult to differentiate them. This has particularly been highlighted in the recent coronavirus disease-2019 pandemic. As we start to understand the differences in the inflammatory markers and presentations in these syndromes, hopefully we will be able to enhance treatment and improve outcomes.

Infection-Related Mortality in Adults and Children Undergoing Allogeneic Hematopoietic Cell Transplantation: An Australian Registry Report

Infection-related mortality (IRM) is the most common non-relapse-related cause of death reported after allogeneic hematopoietic cell transplantation (HCT). Information on the incidence and timing of specific infective organisms and the risk factors for IRM is essential to developing prevention strategies. This report provides the first account of IRM in adults and children undergoing HCT in Australia. Between 2013 and 2018, 2705 adult and 689 pediatric first HCTs were identified from the Australasian Bone Marrow Transplant Recipient Registry database, associated with 1075 (39.7%) total overall deaths in adults and 134 (19.4%) in children. Demographics and causes of death, including infectious etiology and causative organisms, were extracted from the database for adults and children for analysis. At day +100 and 1 year post-HCT, IRM was the leading cause of early post-HCT mortality in adults, accounting for 6.2% and 9.8%, respectively; in children, IRM was the leading cause of post-HCT mortality at day +100 at 2.5% and the second highest cause of post-HCT mortality at 1 year post-HCT at 4.9%, following relapse at 5.8%. In adults, older age, transplantation not in a first complete remission (non-CR1), the use of antithymocyte globulin (ATG) or alemtuzumab, donor-positive/recipient-negative cytomegalovirus (CMV) serostatus, and acute graft-versus-host disease were significant risk factors for IRM. However, in children, age >5 years, acute lymphocytic leukemia as the primary disease, and mismatched unrelated or haploidentical donor source were predictive of IRM. Of the deaths in which an infectious etiology was reported in adults (52.4%), 49.3% were attributed to bacteria, 25.3% to fungus, 21.7% to viruses, and 3.6% to post-transplantation lymphoproliferative disorder (PTLD). The most common organisms were Pseudomonas spp, Enterococcus spp, Candida spp, Aspergillus spp, and CMV. In children where an infectious etiology was reported (64%), 13% were attributed to bacteria, 26% to fungus, 45% to viruses, and 16% to PTLD. This report highlights that IRM was the leading cause of death early post-HCT in Australia. Strategies to reduce IRM, such as individualized pre-transplantation infection risk assessment, rapid diagnostics, and prevention management strategies should be explored to determine whether these outcomes can be improved. In addition, improving the completeness and accuracy of reported data, particularly for infectious pathogens, could assist in directing management strategies to reduce IRM in HCT.

Pathogen-Specific T Cells Beyond CMV, EBV and Adenovirus

PURPOSE OF REVIEW

Infectious diseases contribute significantly to morbidity and mortality in recipients of allogeneic haematopoietic stem cell transplantation (aHSCT), particularly in the era of highly immunosuppressive transplant regimens and alternate donor transplants. Delayed cellular immune recovery is a major mechanism for the increased risk in these patients. Adoptive cell therapy with ex vivo manipulated pathogen-specific T cells (PSTs) is increasingly taking its place as a treatment strategy using donor-derived or third party-banked cells.

RECENT FINDINGS

The majority of clinical trial data in the form of early-phase studies has been in the prophylaxis or treatment of cytomegalovirus (CMV), Epstein-Barr virus (EBV) and adenovirus (AdV). Advancements in methods to select and enrich PSTs offer the opportunity to target the less common viral pathogens as well as fungi with this technology. Early clinical studies of PSTs targeting polyomaviruses (BK virus and JC virus), human herpesvirus 6 (HHV6), varicella zoster virus (VZV) and Aspergillus spp. have shown promising results in small numbers of patients. Other potential targets include herpes simplex virus (HSV), respiratory viruses and other invasive fungal species. In this review, we describe the burden of disease of this wider spectrum of pathogens, the progress in the development of manufacturing capability, early clinical results and the opportunities and challenges for implementation in the clinic.

Adoptive T-cell therapy for pediatric cytomegalovirus-associated retinitis

TCRαβ+/CD19+-depleted haploidentical HSCT was used to restore immunity in a pediatric patient with combined immunodeficiency syndrome. Posttransplant drug-resistant CMV retinitis was successfully treated with T cells expanded from a haploidentical HSCT donor.

Adoptive cell therapies for posttransplant infections

PURPOSE OF REVIEW

Viral and fungal infections cause significant morbidity and mortality following hematopoietic stem-cell transplantation (HSCT), primarily due to the prolonged and complex immunodeficient state that results from conditioning chemo-radiotherapy and subsequent prophylaxis of graft vs. host disease. Although currently available antimicrobial pharmacotherapies have demonstrated short-term efficacy, their toxicities often preclude long-term use, and cessation if frequently associated with recurrent infection. Adoptive cell therapy (ACT) offers the potential to more rapidly reconstitute antimicrobial immune responses in the posttransplant setting.

RECENT FINDINGS

Traditional approaches to manufacture of adoptive T-cell therapies are time consuming and limited to single pathogen specificity. Recent advances in the understanding of immunogenic epitopes, improved methods for pathogen-specific T-cell isolation and cultureware technologies is allowing for rapid generation of ACTs for clinical use.

SUMMARY

The current review summarizes the potential infectious targets and manufacturing methodologies for ACTs and contrasts their clinical efficacy and safety to currently available pharmacotherapies for patients recovering after HSCT.

Generation of Zika virus-specific T cells from seropositive and virus-naïve donors for potential use as an autologous or "off-the-shelf" immunotherapeutic

BACKGROUND

Zika virus (ZIKV) infection can cause severe birth defects in newborns with no effective currently available treatment. Adoptive transfer of virus-specific T cells has proven to be safe and effective for the prevention or treatment of many viral infections, and could represent a novel treatment approach for patients with ZIKV infection. However, extending this strategy to the ZIKV setting has been hampered by limited data on immunogenic T-cell antigens within ZIKV. Hence, we have generated ZIKV-specific T cells and characterized the cellular immune responses against ZIKV antigens.

METHODS

T-cell products were generated from peripheral blood of ZIKV-exposed donors, ZIKV-naive adult donors and umbilical cord blood by stimulation with pentadecamer (15mer) overlapping peptide libraries spanning four ZIKV polyproteins (C, M, E and NS1) using a Good Manufacturing Practice-compliant protocol.

RESULTS

We successfully generated T cells targeting ZIKV antigens with clinically relevant numbers. The ex vivo-expanded T cells comprised both CD4⁺ and CD8⁺ T cells that were able to produce Th1-polarized effector cytokines and kill ZIKV-infected HLA-matched monocytes, confirming functionality of this unique T-cell product as a potential "off-the-shelf" therapeutic. Epitope mapping using peptide arrays identified several novel HLA class I and class II-restricted epitopes within NS1 antigen, which is essential for viral replication and immune evasion.

DISCUSSION

Our findings demonstrate that it is feasible to generate potent ZIKV-specific T cells from a variety of cell sources including virus naïve donors for future clinical use in an "off-the-shelf" setting.

Virus-Specific T Cells: Current and Future Use in Primary Immunodeficiency Disorders

Viral infections are common and can be potentially fatal in patients with primary immunodeficiency disorders (PIDDs). Because viral susceptibility stems from poor to absent T-cell function in most patients with moderate to severe forms of PIDD, adoptive immunotherapy with virus-specific T cells (VSTs) has been used to combat viral infections in the setting of hematopoietic stem cell transplantation in multiple clinical trials. Most trials to date have targeted cytomegalovirus, EBV, and adenovirus either alone or in combination, although newer trials have expanded the number of targeted pathogens. Use of banked VSTs produced from third-party donors has also been studied as a method of expanding access to this therapy. Here we review the clinical experience with VST therapy for patients with PIDDs as well as future potential targets and approaches for the use of VSTs to improve clinical outcomes for this specific patient population.

The polymorphism at residue 156 determines the HLA-B*35 restricted peptide repertoire during HCMV infection

Peptide selection in infected cells is not fully understood yet, but several indications point to the fact that there are differences to uninfected cells, especially in productive HCMV infection, since HCMV evolved various strategies to disable the hosts immune system, including presentation of peptide-HLA complexes to immune effector cells. Therefore, peptide predictions for specific HLA alleles are limited in these cases and the naturally presented peptide repertoire of HCMV-infected cells is of major interest to optimize adoptive T cell therapies. The allotypes HLA-B*35:01 and B*35:08 differ at a single amino acid at position 156 and have been described to differ in their peptide features and in their association with the peptide loading complex. Virus specific T cells recognizing the allelic pHLA-B*35 complexes could be detected, indicating a significant role of this HLA subtypes in viral immunity. However, naturally selected and presented viral peptides have not been described so far. In this study, we analyzed the peptide binding repertoire for HLA-B*35:01 and HLA-B*35:08 in HCMV-infected cells. The isolated peptides from both allelic subtypes were of extraordinary length, however differed in their features, origin, and sequence. For these HCMV-originated peptides, no overlap in the peptide repertoire could be observed between the two allelic subtypes. These findings reveal the discrepancies between predicted and naturally presented immunogenic epitopes and support the need of comprehensive peptide recruitment data for personalized and effective cellular therapies.

Immunomodulation as Therapy for Fungal Infection: Are We Closer?

Invasive fungal disease (IFD) causes significant morbidity in immunocompromised patients due to their weakened immune system. Immunomodulatory therapy, in synergy with existing antifungal therapy, is an attractive option to enhance their immune system and aid clearance of these opportunistic pathogens. From a scientific and clinical perspective, we explore the immunotherapeutic options to augment standard antifungal drugs for patients with an IFD. We discuss the range of immunomodulatory therapies being considered in IFD - from cytokines, including G-CSF, GM-CSF, M-CSF, IFN-γ, and cytokine agonists, to cellular therapies, consisting of granulocyte transfusion, adoptive T-cell, CAR T-cell, natural killer cell therapies, and monoclonal antibodies. Adjunct pharmaceutical agents which augment the immunity are also being considered. Lastly, we explore the likelihood of the use of probiotics and manipulation of the microbiome/mycobiome to enhance IFD treatment outcomes.