Haemopoietic cell transplantation in patients living with HIV

Hematopoietic stem cell transplantation and cellular therapy in persons living with HIV

PURPOSE OF REVIEW

Summarize the latest research of both stem cell transplantation and cellular therapy and present the implications with respect to persons with HIV (PWH), hematologic malignancies, and HIV-1 cure.

RECENT FINDINGS

Allogeneic (alloSCT) and autologous (autoSCT) stem cell transplantation have been shown to be well tolerated and effective regardless of HIV-1 status. AlloSCT leads to a decrease in the HIV-1 latently infected reservoir orders of magnitude below that achieved with antiretroviral therapy (ART) alone. Utilization of CCR5Δ2/Δ32 donors in an alloSCT has resulted in HIV-1 cures. In the last 12 months, three cases of cure have been published, giving further insight into the conditions required for HIV-1 control. Other advances in the treatment of hematological cancers include chimeric antigen receptor T-cell (CART) therapy, which are active in PWH with lymphoma.

SUMMARY

Here we discuss the advances in SCT and cellular therapy in PWH and cancer. Additionally, we discuss how these technologies are being utilized to achieve HIV-1 cure.

Gaining momentum: stem cell therapies for HIV cure

PURPOSE OF REVIEW

Durable HIV-1 remission has been reported in a person who received allogeneic stem cell transplants (SCTs) involving CCR5 Δ32/Δ32 donor cells. Much of the reduction in HIV-1 burden following allogeneic SCT with or without donor cells inherently resistant to HIV-1 infection is likely due to cytotoxic graft-versus-host effects on residual recipient immune cells. Nonetheless, there has been growing momentum to develop and implement stem cell therapies that lead to durable long-term antiretroviral therapy (ART)-free remission without the need for SCT.

RECENT FINDINGS

Most current research leverages gene editing techniques to modify hematopoietic stem cells which differentiate into immune cells capable of harboring HIV-1. Approaches include targeting genes that encode HIV-1 co-receptors using Zinc Finger Nucleases (ZFN) or CRISPR-Cas-9 to render a pool of adult or progenitor cells resistant to de-novo infection. Other strategies involve harnessing multipotent mesenchymal stromal cells to foster immune environments that can more efficiently recognize and target HIV-1 while promoting tissue homeostasis.

SUMMARY

Many of these strategies are currently in a state of infancy or adolescence; nonetheless, promising preclinical and first-in-human studies have been performed, providing further rationale to focus resources on stem cell therapies.

Haematopoietic stem-cell transplantation in an HIV endemic area: time to consider donors exposed to or living with HIV

South Africa has more than 8 million people living with HIV. However, the number of patients undergoing haematopoietic stem-cell transplantation (HSCT) in South Africa is far below the target number. Donor numbers are insufficient to meet demand. Both HSCT and solid organ transplantation have proved successful in people living with HIV. Solid organ transplantation also has good outcomes when both donors and recipients have HIV. This Personal View explores the possible inclusion of people living with HIV and umbilical cord blood from HIV-negative infants exposed to HIV as donor sources for HSCT. Beyond the risk of HIV transmission, additional complications must be considered, such as delayed or inadequate immune reconstitution and an increased risk of haematological abnormalities and malignancies. Interactions between antiretroviral drugs and drugs used in the conditioning regimen, as well as the need to maintain virological suppression when gastrointestinal absorption deteriorates, are additional complicating factors. The process also requires more stringent ethical processes to be in place to minimise physical and emotional harm. However, in an HIV endemic country, people living with HIV or donors exposed to HIV must be considered as part of a multidisciplinary collaborative effort to provide more patients with the opportunity to have a life-saving HSCT.

The next horizon now that everyone has a donor: Precision allogeneic transplantation

Post-transplant cyclophosphamide (PTCy) allows safe and effective partially matched donor allogeneic blood or marrow transplantation (alloBMT), so that almost everyone in need of the procedure now has a donor. Moreover, PTCy and other recent advances have lowered alloBMT mortality rates to less than half of that seen before the turn of the century, at costs that are substantially less than most newly approved anticancer agents. These advances also make tailoring BMT based on patients' unique diseases and characteristics now feasible for further improving outcomes. Personalizing every aspect of alloBMT, including conditioning, donor, graft type, and post-transplant maintenance is now possible. For example, alloBMT's antitumor activity historically was restricted to the allogeneic graft-versus-tumor effect directed against histocompatibility antigens. However, replacing exhausted immune systems with healthy non-exhausted, non-tolerant ones likely can enhance the activity of novel targeted therapies. The impressive results seen with tyrosine kinase inhibitors after alloBMT for patients with both Ph+ acute lymphoblastic leukemia and FLT/ITD+ acute myeloid leukemia herald the potential of precision BMT.

Treating Cancer in People With HIV

The Oncology Grand Rounds series is designed to place original reports published in the Journal into clinical context. A case presentation is followed by a description of diagnostic and management challenges, a review of the relevant literature, and a summary of the authors' suggested management approaches. The goal of this series is to help readers better understand how to apply the results of key studies, including those published in Journal of Clinical Oncology, to patients seen in their own clinical practice.People with HIV (PWH) have an increased lifetime risk of developing certain cancers, even when HIV is well-controlled with antiretroviral therapy. Despite the tremendous advancements in HIV and cancer care over the past several decades, PWH have lower cancer-related survival compared with the general population. Treating HIV-associated cancers requires a multidisciplinary team to manage concurrent opportunistic infections, potential drug-drug interactions, and the co-occurrence of more than one cancer in the same patient. Many factors may lead PWH to receive inappropriate dose adjustments, exclusion from emerging therapies and clinical trials, or no cancer therapy at all. In general, PWH should receive the same standard, full-dose cancer therapy used in the general population unless there are data for specific cancer regimens in PWH. Agents targeting PD-1 and PD-L1 have US Food and Drug Administration (FDA)-approved indications in many HIV-associated cancers, including Hodgkin lymphoma, cervical cancer, head and neck cancer, hepatocellular carcinoma, and non-small-cell lung cancer; however, PWH were excluded from all clinical trials that led to FDA approval of these agents. Several prospective studies and an international retrospective study of PWH with advanced cancer have shown anti-PD-(L)-1 agents to be safe and effective across expected cancer types and CD4+ T-cell counts, supporting their use in PWH for FDA-approved indications. Learning from the experience in anti-PD-(L)-1 agents, future cancer clinical trials should include and seek to actively enroll PWH, so that they have equal and timely access to emerging cancer therapies.

A Review of the Development of Multitarget Molecules against HIV-TB Coinfection Pathogens

The human immunodeficiency virus (HIV) produces the pathologic basis of acquired immunodeficiency syndrome (AIDS). An increase in the viral load in the body leads to a decline in the number of T lymphocytes, compromising the patient's immune system. Some opportunistic diseases may result, such as tuberculosis (TB), which is the most common in seropositive patients. Long-term treatment is required for HIV-TB coinfection, and cocktails of drugs for both diseases are used concomitantly. The most challenging aspects of treatment are the occurrence of drug interactions, overlapping toxicity, no adherence to treatment and cases of resistance. Recent approaches have involved using molecules that can act synergistically on two or more distinct targets. The development of multitarget molecules could overcome the disadvantages of the therapies used to treat HIV-TB coinfection. This report is the first review on using molecules with activities against HIV and Mycobacterium tuberculosis (MTB) for molecular hybridization and multitarget strategies. Here, we discuss the importance and development of multiple targets as a means of improving adherence to therapy in cases of the coexistence of these pathologies. In this context, several studies on the development of structural entities to treat HIV-TB simultaneously are discussed.

HIV-1 remission and possible cure in a woman after haplo-cord blood transplant

Previously, two men were cured of HIV-1 through CCR5Δ32 homozygous (CCR5Δ32/Δ32) allogeneic adult stem cell transplant. We report the first remission and possible HIV-1 cure in a mixed-race woman who received a CCR5Δ32/Δ32 haplo-cord transplant (cord blood cells combined with haploidentical stem cells from an adult) to treat acute myeloid leukemia (AML). Peripheral blood chimerism was 100% CCR5Δ32/Δ32 cord blood by week 14 post-transplant and persisted through 4.8 years of follow-up. Immune reconstitution was associated with (1) loss of detectable replication-competent HIV-1 reservoirs, (2) loss of HIV-1-specific immune responses, (3) in vitro resistance to X4 and R5 laboratory variants, including pre-transplant autologous latent reservoir isolates, and (4) 18 months of HIV-1 control with aviremia, off antiretroviral therapy, starting at 37 months post-transplant. CCR5Δ32/Δ32 haplo-cord transplant achieved remission and a possible HIV-1 cure for a person of diverse ancestry, living with HIV-1, who required a stem cell transplant for acute leukemia.

Brief Report: Rebound HIV Viremia With Meningoencephalitis After Antiretroviral Therapy Interruption After Allogeneic Bone Marrow Transplant

BACKGROUND

Allogeneic bone marrow transplant (alloBMT) in people living with HIV can lead to the undetectable levels of HIV reservoirs in blood, even using highly sensitive assays. However, with antiretroviral therapy (ART) interruption, rebound of HIV viremia occurs. The source of this rebound viremia is of interest in HIV cure strategies.

METHODS

Within a trial of alloBMT in individuals with hematologic malignancies and HIV (ClinicalTrials.gov, NCT01836068), one recipient self-interrupted ART after achieving >99.5% host cell replacement in peripheral blood by day 147 and developed severe acute retroviral syndrome with meningoencephalitis at 156 days post alloBMT. We isolated replication-competent HIV using a quantitative viral outgrowth assay at 100 and 25 days before alloBMT and from the same time points before alloBMT for HIV DNA and cell-associated RNA from peripheral blood mononuclear cells and resting memory CD4+ T cells. We isolated HIV RNA in plasma and cerebrospinal fluid (CSF) at viral rebound. We sequenced the RT-region of pol and performed neighbor-joining phylogenetic reconstruction.

RESULTS

Phylogenetic analysis revealed an identical viral sequence at both pre-alloBMT time points accounting for 9 of 34 sequences (26%) of the sampled HIV reservoir. This sequence population grouped with viral rebound sequences from plasma and CSF with high sequence homology.

DISCUSSION

Despite >99.5% replacement of host cells in peripheral blood, ART interruption led to HIV viral rebound in plasma and CSF. Furthermore, the rebound virus matched replication-competent virus from resting memory CD4+ T cells before alloBMT. This case underscores that HIV-infected recipient cells can persist after alloBMT and that latent replication-competent virus can reestablish infection.

Short Communication: Persistence of HIV After Allogeneic Bone Marrow Transplant in a Dually Infected Individual

Allogeneic bone marrow transplant (alloBMT) with continuous antiretroviral therapy alone has not been shown to completely eradicate HIV, possibly due to HIV persistence in rare residual host cells or infection of donor cells. Within a trial of alloBMT in individuals with hematological malignancies and HIV (ClinicalTrials.gov, NCT01836068), we measured HIV reservoirs longitudinally using a quantitative viral outgrowth assay. We sequenced the reverse transcriptase region of pol for replication-competent virus and performed maximum-likelihood phylogenetic reconstruction. Replacement of host cells was measured using short-tandem repeats. In one participant who had ≥99.5% donor cell replacement, HIV reservoirs declined from 2.2 infectious units per million to undetectable levels at post-alloBMT time points except for week 64. Sequence analysis revealed dual infection pre-alloBMT. Replication-competent virus isolated at week 64 post-alloBMT was identical to a pre-alloBMT variant. This report provides proof-of-concept that minor replication-competent HIV variants can persist at low levels despite ≥99.5% donor cell engraftment post-alloBMT.

A study of the mechanisms responsible for the action of new immunosuppressants and their effects on rat small intestinal transplantation

In a series of studies, using an identical rat intestinal transplantation model, we evaluated the effects of several drugs. FK-506 caused a significant attenuation in the proliferation of allogeneic CD4+ T cells and IFN-γ secreting effector functions. FYT720 resulted in a marked reduction in the numbers of lymphocytes, associated with a reduction of T cell recruitment, in grafts. An anti-MAdCAM antibody was next reported to significantly down-regulate CD4+ T cell infiltration in intestinal grafts by blocking the adhesion molecule, and could be useful as an induction therapy. Concerning TAK-779, this CCR5 and CXCR3 antagonist diminished the number of graft-infiltrating cells by suppressing the expression of their receptors in the graft. As a result, it reduced the total number of recipient T cells involved in graft rejection. As the next step, we focused on the participation of monocytes/ macrophages in this field. PQA-18 has been the focus of a novel immunosuppressant that attenuates not only the production of various cytokines, such as IL-2 & TNF-α, on T cells, but the differentiation of macrophages by inhibiting PAK2 as well. In this report, we summarize our previous studies not only regarding the above drugs, but on an anti-complement drug and a JAK inhibitor as well.

The Interplay of HIV and Autophagy in Early Infection

HIV/AIDS is still a global threat despite the notable efforts made by the scientific and health communities to understand viral infection, to design new drugs or to improve existing ones, as well as to develop advanced therapies and vaccine designs for functional cure and viral eradication. The identification and analysis of HIV-1 positive individuals that naturally control viral replication in the absence of antiretroviral treatment has provided clues about cellular processes that could interact with viral proteins and RNA and define subsequent viral replication and clinical progression. This is the case of autophagy, a degradative process that not only maintains cell homeostasis by recycling misfolded/old cellular elements to obtain nutrients, but is also relevant in the innate and adaptive immunity against viruses, such as HIV-1. Several studies suggest that early steps of HIV-1 infection, such as virus binding to CD4 or membrane fusion, allow the virus to modulate autophagy pathways preparing cells to be permissive for viral infection. Confirming this interplay, strategies based on autophagy modulation are able to inhibit early steps of HIV-1 infection. Moreover, autophagy dysregulation in late steps of the HIV-1 replication cycle may promote autophagic cell-death of CD4⁺ T cells or control of HIV-1 latency, likely contributing to disease progression and HIV persistence in infected individuals. In this scenario, understanding the molecular mechanisms underlying HIV/autophagy interplay may contribute to the development of new strategies to control HIV-1 replication. Therefore, the aim of this review is to summarize the knowledge of the interplay between autophagy and the early events of HIV-1 infection, and how autophagy modulation could impair or benefit HIV-1 infection and persistence, impacting viral pathogenesis, immune control of viral replication, and clinical progression of HIV-1 infected patients.

Stem Cell-Derived Viral Antigen-Specific T Cells Suppress HIV Replication and PD-1 Expression on CD4+ T Cells

The viral antigen (Ag)-specific CD8+ cytotoxic T lymphocytes (CTLs) derived from pluripotent stem cells (PSCs), i.e., PSC-CTLs, have the ability to suppress the human immunodeficiency virus (HIV) infection. After adoptive transfer, PSC-CTLs can infiltrate into the local tissues to suppress HIV replication. Nevertheless, the mechanisms by which the viral Ag-specific PSC-CTLs elicit the antiviral response remain to be fully elucidated. In this study, we generated the functional HIV-1 Gag epitope SL9-specific CTLs from the induced PSC (iPSCs), i.e., iPSC-CTLs, and investigated the suppression of SL9-specific iPSC-CTLs on viral replication and the protection of CD4+ T cells. A chimeric HIV-1, i.e., EcoHIV, was used to produce HIV replication in mice. We show that adoptive transfer of SL9-specific iPSC-CTLs greatly suppressed EcoHIV replication in the peritoneal macrophages and spleen in the animal model. Furthermore, we demonstrate that the adoptive transfer significantly reduced expression of PD-1 on CD4+ T cells in the spleen and generated persistent anti-HIV memory T cells. These results indicate that stem cell-derived viral Ag-specific CTLs can robustly accumulate in the local tissues to suppress HIV replication and prevent CD4+ T cell exhaustion through reduction of PD-1 expression.

Mito-managing ROS & redox to reboot the immune system: Tapping mitochondria & redox management to extend the reach of hematopoietic stem cell transplantation

Hematopoietic stem cells (HSCs) are responsible for life-long production of blood and immune cells. HSC transplantation (HSCT) is the original cell therapy which can cure hematological disorders but also has the potential to treat other diseases if technical and safety barriers are overcome. To maintain homeostatic hematopoiesis or to restore hematopoiesis during transplantation HSCs must perform both self-renewal, replication of themselves, and differentiation, generation of mature blood and immune cells. These are just two of the cell fate choices HSCs have; the transitional phases where HSCs undergo these cell fate decisions are regulated by reduction-oxidation (redox) signaling, mitochondrial activity, and cellular metabolism. Recent studies revealed that mitochondria, a key source of redox signaling components, are central to HSC cell fate decisions. Here we highlight how mitochondria serve as hubs in HSCs to manage redox signaling and metabolism and thus guide HSC fate choices. We focus on how mitochondrial activity is modulated by their clearance, biogenesis, dynamics, distribution, and quality control in HSCs. We also note how modulating mitochondria in HSCs can help overcome technical barriers limiting further use of HSCT.

CAR T-cell therapy for cancer and HIV through novel approaches to HIV-associated haematological malignancies

People living with HIV are a global population with increased cancer risk but their access to modern immunotherapies for cancer treatment has been limited by socioeconomic factors and inadequate research to support safety and efficacy in this population. These immunotherapies include immune checkpoint inhibitors and advances in cellular immunotherapy, particularly chimeric antigen receptor (CAR) T-cell therapy. Despite the field of cancer immunotherapy rapidly expanding with ongoing clinical trials, people with HIV are often excluded from such trials. In 2019, post-approval evaluation of anti-CD19 CAR T-cell therapy in people with HIV and aggressive B-cell lymphoma showed the feasibility of CAR T-cell therapy for cancer in this excluded group. Along with expanded treatment options for people with HIV is the ability to assess the effects of immunotherapy on the latent HIV reservoir, with certain immunotherapies showing the ability to alleviate this burden. This Series paper addresses the increased cancer burden in people with HIV, the increasing evidence for the safety and efficacy of immunotherapies in the context of HIV and cancer, and opportunities for novel applications of CAR-T therapy for the treatment of both haematological malignancies and HIV.