Advances in Mechanism of HIV-1 Immune Reconstitution Failure: Understanding Lymphocyte Subpopulations and Interventions for Immunological Nonresponders.

In individuals diagnosed with AIDS, the primary method of sustained suppression of HIV-1 replication is antiretroviral therapy, which systematically increases CD4+ T cell levels and restores immune function. However, there is still a subset of 10-40% of people living with HIV who not only fail to reach normal CD4+ T cell counts but also experience severe immune dysfunction. These individuals are referred to as immunological nonresponders (INRs). INRs have a higher susceptibility to opportunistic infections and non-AIDS-related illnesses, resulting in increased morbidity and mortality rates. Therefore, it is crucial to gain new insights into the primary mechanisms of immune reconstitution failure to enable early and effective treatment for individuals at risk. This review provides an overview of the dynamics of key lymphocyte subpopulations, the main molecular mechanisms of INRs, clinical diagnosis, and intervention strategies during immune reconstitution failure, primarily from a multiomics perspective.

The Expression Levels of TREX1 and IFN-α Are Associated with Immune Reconstitution in HIV-1-Infected Individuals.

TREX1 acts in the initial prevention of an autoimmune response, but it may contribute to the permissiveness of retrovirus infections. This study investigated the association between the levels of TREX1 gene expression with the polymorphisms TREX1 rs3135941 (T/C) and TREX1 rs3135945 (G/A), and the presence of antinuclear antibodies (ANA) in antiretroviral therapy (ART)-naïve individuals and after 1 year of treatment. Blood samples from 119 individuals with HIV-1 were subjected to genotyping of polymorphisms and quantification of TREX1 gene expression and HIV-1 viral load by qPCR. The concentration of IFN-α and the number of CD4+/CD8+ T lymphocytes were determined by ELISA and flow cytometry, respectively; ANA was investigated by immunofluorescence. A control group of 167 seronegative individuals was used for the comparison of genotypic frequencies. The frequency of the polymorphisms were not associated with HIV infection or with variations in the expression of TREX1 and IFN-α (p > 0.05). ART-naïve individuals exhibited higher TREX1 expression and lower IFN-α expression. After 1 year of ART, TREX1 levels were reduced, while IFN-α and CD4+ T lymphocytes were elevated (p < 0.05). Some individuals on ART presented ANA. These results suggest that ART-mediated restoration of immune competence is associated with a reduction in TREX1 expression, which may induce the development of ANA, regardless of the polymorphism investigated.

Early Myeloid Derived Suppressor Cells (eMDSCs) Are Associated With High Donor Myeloid Chimerism Following Haploidentical HSCT for Sickle Cell Disease.

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is a widely available curative option for patients with sickle cell disease (SCD). Our original non-myeloablative haplo-HSCT trial employing post-transplant (PT) cyclophosphamide had a low incidence of GVHD but had high rejection rates. Here, we aimed to evaluate immune reconstitution following haplo-HSCT and identify cytokines and cells associated with graft rejection/engraftment. 50 cytokines and 10 immune cell subsets were screened using multiplex-ELISA and flow cytometry, respectively, at baseline and PT-Days 30, 60, 100, and 180. We observed the most significant differences in cytokine levels between the engrafted and rejected groups at PT-Day 60, corresponding with clinical findings of secondary graft rejection. Of the 44 cytokines evaluated, plasma concentrations of 19 cytokines were different between the two groups at PT-Day 60. Factor analysis suggested two independent factors. The first factor (IL-17A, IL-10, IL-7, G-CSF, IL-2, MIP-1a, VEGF, and TGFb1 contributed significantly) was strongly associated with engraftment with OR = 2.7 (95%CI of 1.4 to 5.4), whereas the second factor (GROa and IL-18 contributed significantly) was not significantly associated with engraftment. Sufficient donor myeloid chimerism (DMC) is critical for the success of HSCT; here, we evaluated immune cells among high (H) DMC (DMC≥20%) and low (L) DMC (DMC<20%) groups along with engrafted and rejected groups. We found that early myeloid-derived suppressor cell (eMDSC) frequencies were elevated in engrafted patients and patients with HDMC at PT-Day 30 (P< 0.04 & P< 0.003, respectively). 9 of 20 patients were evaluated for the source of eMDSCs. The HDMC group had high mixed chimeric eMDSCs as compared to the LDMC group (P< 0.00001). We found a positive correlation between the frequencies of eMDSCs and Tregs at PT-Day 100 (r=0.72, P <0.0007); eMDSCs at BSL and Tregs at PT-Day 100 (r=0.63, P <0.004). Of 10 immune regulatory cells and 50 cytokines, we observed mixed chimeric eMDSCs and IL-17A, IL-10, IL-7, G-CSF, IL-2, MIP-1a, VEGF, TGFb1 as potential hits which could serve as prognostic markers in predicting allograft outcome towards engraftment following haploidentical HSCT employing post-transplant cyclophosphamide. The current findings need to be replicated and further explored in a larger cohort.

Immune Recovery Following Autologous Hematopoietic Stem Cell Transplantation in HIV-Related Lymphoma Patients on the BMT CTN 0803/AMC 071 Trial.

We report a first in-depth comparison of immune reconstitution in patients with HIV-related lymphoma following autologous hematopoietic cell transplant (AHCT) recipients (n=37, lymphoma, BEAM conditioning), HIV(-) AHCT recipients (n=30, myeloma, melphalan conditioning) at 56, 180, and 365 days post-AHCT, and 71 healthy control subjects. Principal component analysis showed that immune cell composition in HIV(+) and HIV(-) AHCT recipients clustered away from healthy controls and from each other at each time point, but approached healthy controls over time. Unsupervised feature importance score analysis identified activated T cells, cytotoxic memory and effector T cells [higher in HIV(+)], and naïve and memory T helper cells [lower HIV(+)] as a having a significant impact on differences between HIV(+) AHCT recipient and healthy control lymphocyte composition (p<0.0033). HIV(+) AHCT recipients also demonstrated lower median absolute numbers of activated B cells and lower NK cell sub-populations, compared to healthy controls (p<0.0033) and HIV(-) AHCT recipients (p<0.006). HIV(+) patient T cells showed robust IFNγ production in response to HIV and EBV recall antigens. Overall, HIV(+) AHCT recipients, but not HIV(-) AHCT recipients, exhibited reconstitution of pro-inflammatory immune profiling that was consistent with that seen in patients with chronic HIV infection treated with antiretroviral regimens. Our results further support the use of AHCT in HIV(+) individuals with relapsed/refractory lymphoma.

B cells in multiple sclerosis - from targeted depletion to immune reconstitution therapies.

Increasing evidence indicates the involvement of B cells in the pathogenesis of multiple sclerosis (MS), but their precise roles are unclear. In this Review, we provide an overview of the development and physiological functions of B cells and the main mechanisms through which B cells are thought to contribute to CNS autoimmunity. In MS, abnormalities of B cell function include pro-inflammatory cytokine production, defective B cell regulatory function and the formation of tertiary lymphoid-like structures in the CNS, which are the likely source of abnormal immunoglobulin production detectable in the cerebrospinal fluid. We also consider the hypothesis that Epstein-Barr virus (EBV) is involved in the B cell overactivation that leads to inflammatory injury to the CNS in MS. We also review the immunological effects - with a focus on the effects on B cell subsets - of several successful therapeutic approaches in MS, including agents that selectively deplete B cells (rituximab, ocrelizumab and ofatumumab), agents that less specifically deplete lymphocytes (alemtuzumab and cladribine) and autologous haematopoietic stem cell transplantation, in which the immune system is unselectively ablated and reconstituted. We consider the insights that these effects on B cell populations provide and their potential to further our understanding and targeting of B cells in MS.

Immune Reconstitution in the Aging Host: Opportunities for Mechanism-Based Therapy in Allogeneic Hematopoietic Cell Transplantation.

Older patients with hematologic malignancies are increasingly considered for allogeneic hematopoietic cell transplantation with encouraging outcomes. While aging-related thymic dysfunction remains a major obstacle to optimal and timely immune reconstitution post- transplantation, recent accumulating evidence has suggested that various aging hallmarks such as cellular senescence, inflamm-aging, and hematopoietic stem cell exhaustion, could also impact immune reconstitution post-transplantation in both thymic-dependent and independent manner. Here we review molecular and cellular aspects of immune senescence and immune rejuvenation related to allogeneic hematopoietic cell transplantation among older patients and discuss potential strategies for mechanism-based therapeutic intervention.

Functional immune reconstitution early after allogeneic haematopoietic cell transplantation: A comparison of pre- and post-transplantation cytokine responses in stimulated whole blood.

We aimed to use a novel standardized whole-blood stimulation system to evaluate differences in the functional immune reconstitution in patients early after allogeneic haematopoietic cell transplantation (HCT). Between April and September 2018, 30 patients undergoing HCT had whole blood samples collected around day -21 (day 0 being the day of haematopoietic cell infusion) and day +28. Whole blood was transferred to TruCulture assays comprising prefilled incubation tubes with cell culture medium and a standardized stimulus. We used a panel of four stimuli (lipopolysaccharide, resiquimod, heat-killed Candida albicans and polyinosinic:polycytidylic acid) and a blank, designed to evaluate the function of critical extra- and intracellular immunological signalling pathways. For each stimulus, the cytokine response was assessed by the concentration of interferon-γ, interleukin (IL)-12p40, IL-10, IL-1ß, IL-6, IL-8, IL-10, IL-12p40, IL-17A and tumour necrosis factor-α using a multiplex Luminex assay. Pre-HCT cytokine responses were globally decreased across several different stimuli. Despite patients receiving immunosuppressive prophylaxis at the time, post-HCT cytokine responses were higher and less intercorrelated than pre-HCT responses, also after adjusting for differences in the leukocyte differential counts. For the resiquimod and heat-killed Candida albicans stimuli, we identified a cluster of patients in whom post-HCT responses were lower than average across several cytokines, indicating a possible functional immune deficiency. Our findings suggest that the standardized whole blood stimulation system can be used to reveal heterogeneity in the in vitro cytokine responses to various stimuli after HCT. Larger studies are needed to address if the functional immune reconstitution after HCT can predict the risk of infections.

Immune function in childhood cancer survivors: a Children's Oncology Group review.

Childhood cancer and its treatment often impact the haematopoietic and lymphatic systems, with immunological consequences. Immunological assessments are not routinely included in surveillance guidelines for most survivors of childhood cancer, although a robust body of literature describes immunological outcomes, testing recommendations, and revaccination guidelines after allogeneic haematopoietic cell transplantation. Survivorship care providers might not fully consider the impaired recovery of a child's immune system after cancer treatment if the child has not undergone haematopoietic cell transplantation. We did a scoping review to collate the existing literature describing immune function after childhood cancer therapy, including both standard-dose chemotherapy and high-dose chemotherapy with haematopoietic cell rescue. This Review aims to summarise: the principles of immunology and testing of immune function; the body of literature describing immunological outcomes after childhood cancer therapy, with an emphasis on the risk of infection, when is testing indicated, and preventive strategies; and knowledge gaps and opportunities for future research.

Immune Reconstitution After Gene Therapy Approaches in Patients With X-Linked Severe Combined Immunodeficiency Disease.

X-linked severe immunodeficiency disease (SCID-X1) is an inherited, rare, and life-threating disease. The genetic origin is a defect in the interleukin 2 receptor γ chain (IL2RG) gene and patients are classically characterized by absence of T and NK cells, as well as presence of partially-functional B cells. Without any treatment the disease is usually lethal during the first year of life. The treatment of choice for these patients is hematopoietic stem cell transplantation, with an excellent survival rate (>90%) if an HLA-matched sibling donor is available. However, when alternative donors are used, the success and survival rates are often lower. Gene therapy has been developed as an alternative treatment initially using γ-retroviral vectors to correct the defective γ chain in the absence of pre-conditioning treatment. The results were highly promising in SCID-X1 infants, showing long-term T-cell recovery and clinical benefit, although NK and B cell recovery was less robust. However, some infants developed T-cell acute lymphoblastic leukemia after the gene therapy, due to vector-mediated insertional mutagenesis. Consequently, considerable efforts have been made to develop safer vectors. The most recent clinical trials using lentiviral vectors together with a low-dose pre-conditioning regimen have demonstrated excellent sustained T cell recovery, but also B and NK cells, in both children and adults. This review provides an overview about the different gene therapy approaches used over the last 20 years to treat SCID-X1 patients, particularly focusing on lymphoid immune reconstitution, as well as the developments that have improved the process and outcomes.

Immune restoration in HIV-1-infected patients after 12 years of antiretroviral therapy: a real-world observational study.

Using normalization of CD4 counts as the main evaluation parameter of complete immune restoration for HIV-1 patients under antiretroviral therapy (ART) might be not enough. A comprehensive evaluation system more accurately reflecting immune restoration are urgently needed. Totally, 91,805 HIV-1 patients from 17 tertiary hospitals in China during 2005-2018 were included in this study. Immune restoration and mortality were assessed. Patients initiated ART with baseline CD4 counts <50, 50-199, 200-349, 350-499, and ≥500 cells/µL, and results showed an increase in the median CD4 counts to 445 (12-year), 467 (12-year), 581 (11-year), 644 (7-year), and 768 cells/µL (5-year), as well as the CD4/CD8 ratio to 0.59 (12-year), 0.65 (12-year), 0.79 (11-year), 0.82 (7-year), 0.9 (5-year), respectively. The median CD8 count was relatively high (median range 732-845 cells/µL), regardless of the baseline CD4 counts. Furthermore, the probabilities of death in patients achieving CD4 counts ≥500 cells/µL and CD4/CD8 ratio ≥0.8 simultaneously were significantly lower than those in patients achieving either CD4 counts ≥500 cells/µL (2.77% vs 3.50%, p=0.02) or CD4/CD8 ≥ 0.8 (2.77% vs 4.28%, p<0.001) after 12-year of ART. In this study, a new binary-indicator would accurately assess immune restoration in the era of "treat all."

Autoimmune Hemolytic Anemia in Chronic Myeloid Leukemia.

BACKGROUND: Autoimmune hemolytic anemia (AIHA) might be associated with underlying hematological malignancies such as chronic lymphocytic leukemia. However, the association between AIHA and chronic myelogenous leukemia is extremely unusual. SUMMARY: We reviewed case reports and series of 54 patients with chronic myeloid leukemia (CML) who developed autoimmune hemolysis between 1952 and 2018. Almost all the patients were in the chronic phase and were classified into transplant and non-transplant groups. The onset of autoimmune hemolysis was earlier in the transplant group and required second- and third-line therapy to control it. The etiology of hemolysis is poorly understood but attributed in the transplant group to immune reconstitution, viral infections, or CML relapse. On the other hand, it is thought to be related in the non-transplant group to CML medications, especially interferon. Key Messages: Although AIHA is uncommon in chronic myelogenous leukemia patients, it should be in the differential diagnosis list for those who develop a sudden drop in hemoglobin without a bleeding source.

Treatment of Progressive Multifocal Leukoencephalopathy Using Immune Restoration.

Progressive multifocal leukoencephalopathy (PML) is a viral disease of the brain associated with immunodeficiency, immune suppressing medications, and malignancy. In the absence of effective anti-viral therapy for the causative JC virus, immune restoration has emerged as the critical therapeutic alternative. The evolving treatment of PML (and other rare JC virus-associated neurologic syndromes) requires consideration of baseline immune functioning and comorbid diseases while selecting from a number of therapeutic options to restore an effective immune response. This review focuses on the current options for management of PML in typical situations where this disease presents, including several where immune restoration is a standard therapeutic approach such as in PML associated with HIV/AIDS and in multiple sclerosis associated with natalizumab. Other circumstances in which PML occurs including associated with primary immunodeficiencies, malignancies, and transplants present greater challenges to immune reconstitution, but emerging concepts may enhance therapeutic options for these situations. Particular attention is focused on recent experience with checkpoint inhibitors, guidance for MS drug discontinuation, and strategies to monitor and facilitate immune restoration.

The Monocytes That Repopulate in Mice After Cyclophosphamide Treatment Acquire a Neutrophil Precursor Gene Signature and Immunosuppressive Activity.

Cyclophosphamide (CTX) is a major component of the chemotherapy conditioning regimens used in the clinic to prepare cancer patients for hematopoietic stem cell transplantation or adoptive T cell therapy. Previous studies have shown that CTX given at nonmyeloablative doses in mice and patients leads to expansion of myeloid cells within which the monocytic subset exhibits immunosuppressive activity. However, the ontogeny and gene expression signature of these CTX-induced monocytes are not well-defined. Here, we report that the expansion of myeloid cells is a default process intrinsic to hematopoietic recovery after chemotherapy. During this process, the monocytes repopulated in mice acquire immunosuppressive activity, which can persist long after cessation of chemotherapy. Moreover, monocytes acquire a gene signature characteristic of neutrophil precursors, marked by increased proliferative capability and elevated expressions of multiple primary and secondary granules. We provide evidence that CTX-induced myeloid cell expansion is regulated by DNA methyltransferase 1 (Dnmt1) and dependent on chemotherapy-induced microbial translocation. These findings help advance our understanding of the differentiation, heterogeneity, and function of myeloid cells repopulating after chemotherapy.

Immune reconstitution therapies: concepts for durable remission in multiple sclerosis.

New so-called immune reconstitution therapies (IRTs) have the potential to induce long-term or even permanent drug-free remission in people with multiple sclerosis (MS). These therapies deplete components of the immune system with the aim of allowing the immune system to renew itself. Haematopoietic stem cell transplantation, the oral formulation cladribine and the monoclonal antibodies alemtuzumab, rituximab and ocrelizumab are frequently categorized as IRTs. However, the evidence that IRTs indeed renew adaptive immune cell repertoires and rebuild a healthy immune system in people with MS is variable. Instead, IRTs might foster the expansion of those cells that survive immunosuppression, and this expansion could be associated with acquisition of new functional phenotypes. Understanding immunological changes induced by IRTs and how they correlate with clinical outcomes will be instrumental in guiding the optimal use of immune reconstitution as a durable therapeutic strategy. This Perspectives article critically discusses the efficacy and potential mechanisms of IRTs in the context of immune system renewal and durable disease remission in MS.

Regulatory T cells in allogeneic hematopoietic stem cell transplantation: From the lab to the clinic.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curable strategy for the treatment of hematological malignancies and nonmalignant diseases. However, graft-versus-host disease (GVHD) and relapse are still two major causes of morbidity and mortality after allo-HSCT, and both restrict the improvement of transplant outcomes. Regulatory T cells (Tregs) has been successfully used in allo-SCT settings. In this review, we summarize recent advances in experimental studies that have evaluated the roles played by Tregs in the establishment of novel transplant modalities, the prevention of GVHD and the enhancement of immune reconstitution. We also discuss the application of Tregs in clinical to prevent acute GVHD, treat chronic GVHD, as well as enhance immune reconstitution and decrease leukemia relapse, all of which lead to improving transplant outcomes.

Plasma levels of soluble membrane attack complex are elevated despite viral suppression in HIV patients with poor immune reconstitution.

The complement system is now a therapeutic target for the management of serious and life-threatening conditions such as paroxysmal nocturnal hemoglobinuria, atypical hemolytic uremic syndrome, glomerulonephritis and other diseases caused by complement deficiencies or genetic variants. As complement therapeutics expand into more clinical conditions, monitoring complement activation is increasingly important, as is the baseline levels of complement activation fragments in blood or other body fluid levels. Although baseline complement levels have been reported in the literature, the majority of these data were generated using non-standard assays and with variable sample handling, potentially skewing results. In this study, we examined the plasma and serum levels of the soluble membrane attack complex of complement (sMAC). sMAC is formed in the fluid phase when complement is activated through the terminal pathway. It binds the regulatory proteins vitronectin and/or clusterin and cannot insert into cell membranes, and can serve as a soluble diagnostic marker in infectious disease settings, as previously shown for intraventricular shunt infections. Here we show that in healthy adults, serum sMAC levels were significantly higher than those in plasma, that plasma sMAC levels were similar between in African Americans and Caucasians and that plasma sMAC levels increase with age. Plasma sMAC levels were significantly higher in virally suppressed people living with HIV (PLWH) compared to non-HIV infected healthy donors. More specifically, PLWH with CD4+ T cell counts below 200 had even greater sMAC levels, suggesting diagnostic value in monitoring sMAC levels in this group.

Ex vivo generated human T-lymphoid progenitors as a tool to accelerate immune reconstitution after partially HLA compatible hematopoietic stem cell transplantation or after gene therapy.

Prolonged T-cell immunodeficiency following HLA- incompatible hematopoietic stem cell transplantation (HSCT) represents a major obstacle hampering the more widespread use of this approach. Strategies to fasten T-cell reconstitution in this setting are highly warranted as opportunistic infections and an increased risk of relapse account for high rates of morbidity and mortality especially during early month following this type of HSCT. We have implemented a feeder free cell system based on the use of the notch ligand DL4 and cytokines allowing for the in vitro differentiation of human T-Lymphoid Progenitor cells (HTLPs) from various sources of CD34+ hematopoietic stem and precursor cells (HSPCs). Co- transplantion of human T-lymphoid progenitors (HTLPs) and non- manipulated HSPCs into immunodeficient mice successfully accelerated the reconstitution of a polyclonal T-cell repertoire. This review summarizes preclinical data on the use of T-cell progenitors for treatment of post- transplantation immunodeficiency and gives insights into the development of GMP based protocols for potential clinical applications including gene therapy approaches. Future clinical trials implementing this protocol will aim at the acceleration of immune reconstitution in different clinical settings such as SCID and leukemia patients undergoing allogeneic transplantation. Apart from pure cell-therapy approaches, the combination of DL-4 culture with gene transduction protocols will open new perspectives in terms of gene therapy applications for primary immunodeficiencies.

Use of Multivariate Immune Reconstitution Patterns to Describe Immune Reconstitution after Allogeneic Stem Cell Transplantation in Children.

Immune reconstitution after hematopoietic stem cell transplantation (HSCT) is a complex process. Impacts of the reconstitution of different immune cells over time are complex and difficult to understand. New mathematical models are needed to better understand this process. In this study, we used principal component analysis to better analyze the process of immune reconstitution after HSCT. Forty-six consecutive patients receiving HSCT for malignant and nonmalignant disorders were included in the study. All patients were followed for at least 24 months after transplantation with regular blood sampling for analysis of lymphocyte subset numbers and function. Exponentially transformed lymphocyte subset counts and lymphocyte functional markers were analyzed to identify major trends in the reconstitution process. Using our multivariate model for mapping immune reconstitution after HSCT, we showed that dysfunctional reconstitution patterns precede severe complications, such as chronic graft-versus-host disease, relapse, and death.