Autopsy Study Defines Composition and Dynamics of the HIV-1 Reservoir after Allogeneic Hematopoietic Stem Cell Transplantation with CCR5Δ32/Δ32 Donor Cells.

Allo-HSCT with CCR5Δ32/Δ32 donor cells is the only curative HIV-1 intervention. We investigated the impact of allo-HSCT on the viral reservoir in PBMCs and post-mortem tissue in two patients. IciS-05 and IciS-11 both received a CCR5Δ32/Δ32 allo-HSCT. Before allo-HSCT, ultrasensitive HIV-1 RNA quantification; HIV-1-DNA quantification; co-receptor tropism analysis; deep-sequencing and viral characterization in PBMCs and bone marrow; and post-allo-HSCT, ultrasensitive RNA and HIV-1-DNA quantification were performed. Proviral quantification, deep sequencing, and viral characterization were done in post-mortem tissue samples. Both patients harbored subtype B CCR5-tropic HIV-1 as determined genotypically and functionally by virus culture. Pre-allo-HSCT, HIV-1-DNA could be detected in both patients in bone marrow, PBMCs, and T-cell subsets. Chimerism correlated with detectable HIV-1-DNA LTR copies in cells and tissues. Post-mortem analysis of IciS-05 revealed proviral DNA in all tissue biopsies, but not in PBMCs. In patient IciS-11, who was transplanted twice, no HIV-1-DNA could be detected in PBMCs at the time of death, whereas HIV-1-DNA was detectable in the lymph node. In conclusion, shortly after CCR5Δ32/Δ32, allo-HSCT HIV-1-DNA became undetectable in PBMCs. However, HIV-1-DNA variants identical to those present before transplantation persisted in post-mortem-obtained tissues, indicating that these tissues play an important role as viral reservoirs.

Salvage treatment with plerixafor in poor mobilizing allogeneic stem cell donors: results of a prospective phase II-trial.

We conducted a prospective clinical trial to investigate the safety and efficacy of plerixafor (P) in allogeneic peripheral blood stem cells (PBSC) donors with poor mobilization response to standard-dose granulocyte colony-stimulating factor (G-CSF), defined by <2 × 106 CD34 + cells/kg recipient body-weight (CD34+/kg RBW) after 1st apheresis. A single dose of 240 µg/kg P was injected subcutaneously at 10 p.m. on the day of the 1st apheresis. Thirty-seven allogeneic PBSC donors underwent study treatment. The median CD34+ count in peripheral blood was 15/µl on Day 1 after G-CSF alone, versus 44/µl on Day 2 after G-CSF plus P (p < 0.001). The median yield of CD34+ cells was 1.1 × 108 on Day 1 and 2.8 × 108 on Day 2. In contrast to a median yield of only 1.31 × 106 CD CD34+/kg RBW on Day 1, triggering study inclusion, a median of 3.74 × 106 CD CD34+/kg RBW were collected with G-CSF plus P on Day 2. Of 37 donors, 21 reached the target cell count of >4.5 × 106 CD34+/kg RBW (57%, 95%CI 40-73%). No donor experienced a severe adverse event requiring treatment. In conclusion, P might be considered on a case-by-case basis for healthy allogeneic donors with very poor stem cell mobilization success after G-CSF.

Vulnerability to reservoir reseeding due to high immune activation after allogeneic hematopoietic stem cell transplantation in individuals with HIV-1.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only medical intervention that has led to an HIV cure. Whereas the HIV reservoir sharply decreases after allo-HSCT, the dynamics of the T cell reconstitution has not been comprehensively described. We analyzed the activation and differentiation of CD4+ and CD8+ T cells, and the breadth and quality of HIV- and CMV-specific CD8+ T cell responses in 16 patients with HIV who underwent allo-HSCT (including five individuals who received cells from CCR5Δ32/Δ32 donors) to treat their underlying hematological malignancy and who remained on antiretroviral therapy (ART). We found that reconstitution of the T cell compartment after allo-HSCT was slow and heterogeneous with an initial expansion of activated CD4+ T cells that preceded the expansion of CD8+ T cells. Although HIV-specific CD8+ T cells disappeared immediately after allo-HSCT, weak HIV-specific CD8+ T cell responses were detectable several weeks after transplant and could still be detected at the time of full T cell chimerism, indicating that de novo priming, and hence antigen exposure, occurred during the time of T cell expansion. These HIV-specific T cells had limited functionality compared with CMV-specific CD8+ T cells and persisted years after allo-HSCT. In conclusion, immune reconstitution was slow, heterogeneous, and incomplete and coincided with de novo detection of weak HIV-specific T cell responses. The initial short phase of high T cell activation, in which HIV antigens were present, may constitute a window of vulnerability for the reseeding of viral reservoirs, emphasizing the importance of maintaining ART directly after allo-HSCT.

Differences in Cellular Composition of Peripheral Blood Stem Cell Grafts from Healthy Stem Cell Donors Mobilized with Either Granulocyte Colony-Stimulating Factor (G-CSF) Alone or G-CSF and Plerixafor.

This study was conducted to characterize and compare peripheral blood stem cell grafts from healthy donors who underwent granulocyte colony-stimulating factor (G-CSF) mobilization and subsequently received 1 dose of plerixafor after insufficient stem cell yields were achieved at the first apheresis. Aliquots from 35 donors were collected from the first apheresis after mobilization with G-CSF alone and from the second apheresis after additional plerixafor administration. Samples were freshly analyzed for cellular subsets by 8-color flow cytometry. Leukapheresis samples mobilized with additional plerixafor showed a significant increase of total nucleated cells, including B cells, CD4+ and CD8+ T cells, and CD34+ hematopoietic stem and progenitor cells. Absolute numbers of plasmacytoid dendritic cells were also significantly increased, whereas no changes were detected for myeloid dendritic cells. Furthermore, absolute numbers of regulatory T cells increased, with naive CD45RA+ regulatory T cells showing the highest rise. Finally, strikingly higher numbers of myeloid-derived suppressor cells were detected in the plerixafor and G-CSF-mobilized graft. The mobilization of peripheral stem cells in healthy donors with G-CSF and plerixafor led to a significant difference in cellular graft composition compared with G-CSF alone. The clinical impact of the different cell composition for the graft recipient warrants further clinical investigation.

Single-Stage Preparation of Human Cartilage Grafts Generated from Bone Marrow-Derived CD271+ Mononuclear Cells.

Due to the limited self-healing capacity of articular cartilage, innovative, regenerative approaches are of particular interest. The use of two-stage procedures utilizing in vitro-expanded mesenchymal stromal cells (MSCs) from various cell sources requires good manufacturing practice-compliant production, a process with high demands on time, staffing, and financial resources. In contrast, one- stage procedures are directly available, but need a safe enrichment of potent MSCs. CD271 is a surface marker known to marking the majority of native MSCs in bone marrow (BM). In this study, the feasibility of generating a single-stage cartilage graft of enriched CD271+ BM-derived mononuclear cells (MNCs) without in vitro monolayer expansion from eight healthy donors was investigated. Cartilage grafts were generated by magnetic-activated cell sorting and separated cells were directly transferred into collagen type I hydrogels, followed by 3D proliferation and differentiation period of CD271+, CD271-, or unseparated MNCs. CD271+ MNCs showed the highest proliferation rate, cell viability, sulfated glycosaminoglycan deposition, and cartilage marker expression compared to the CD271- or unseparated MNC fractions in 3D culture. Analysis according to the minimal criteria of the International Society for Cellular Therapy highlighted a 66.8-fold enrichment of fibroblast colony-forming units in CD271+ MNCs and the only fulfillment of the MSC marker profile compared to unseparated MNCs. In summary, CD271+ MNCs are capable of generating adequate articular cartilage grafts presenting high cell viability and notable chondrogenic matrix deposition in a CE-marked collagen type I hydrogel, which can obviate the need for an initial monolayer expansion.

Stem cell transplantation in strategies for curing HIV/AIDS.

HIV-1 can persist in a latent form in resting memory CD4+ cells and macrophages carrying an integrated copy of the HIV genome. Because of the presence of these stable reservoir cells, eradication by antiretroviral therapy is unlikely and in order to achieve eradication, alternative treatment options are required. Stem cell transplantation has been considered previously to effect the clinical course of HIV-infection but in practice eradication or virus control was not achievable. However, modifications of stem cell transplantation using natural or artificial resistant cell sources, combination with new techniques of gene editing or generating cytotoxic anti HIV effector cells have stimulated this field of HIV cell therapy substantially. Here, we look back on 30 years of stem cell therapy in HIV patients and discuss most recent developments in this direction.

CCR5 Targeted Cell Therapy for HIV and Prevention of Viral Escape.

Allogeneic transplantation with CCR5-delta 32 (CCR5-d32) homozygous stem cells in an HIV infected individual in 2008, led to a sustained virus control and probably eradication of HIV. Since then there has been a high degree of interest to translate this approach to a wider population. There are two cellular ways to do this. The first one is to use a CCR5 negative cell source e.g., hematopoietic stem cells (HSC) to copy the initial finding. However, a recent case of a second allogeneic transplantation with CCR5-d32 homozygous stem cells suffered from viral escape of CXCR4 quasi-species. The second way is to knock down CCR5 expression by gene therapy. Currently, there are five promising techniques, three of which are presently being tested clinically. These techniques include zinc finger nucleases (ZFN), clustered regularly interspaced palindromic repeats/CRISPR-associated protein 9 nuclease (CRISPR/Cas9), transcription activator-like effectors nuclease (TALEN), short hairpin RNA (shRNA), and a ribozyme. While there are multiple gene therapy strategies being tested, in this review we reflect on our current knowledge of inhibition of CCR5 specifically and whether this approach allows for consequent viral escape.

Distribution of the CCR5-delta32 deletion in Southwest Germany.

A 32 base pair deletion in the c-c chemokine receptor gene 5 (CCR5) leads to an inactive protein. Carriers of this deletion must have had a selective advantage because the allelic frequency of the CCR5-delat32 mutation is much higher than expected. Furthermore, there is a decline from North to South Europe. For Germany there are just very few cross-sectional surveys available. Here we investigated a large number of healthy blood donors from Northern Baden-Wuerttemberg. We observed an allelic frequency of 9.21 % of the CCR5-delta32 deletion. The distribution did not follow the Hardy-Weinberg equilibrium suggesting that homozygous carriers of the deletion were overrepresented in this random sample.

Dependence on the CCR5 coreceptor for viral replication explains the lack of rebound of CXCR4-predicted HIV variants in the Berlin patient.

The "Berlin patient" is the first patient cured of HIV-1 infection after allogeneic transplantation with nonfunctional CCR5 coreceptor stem cells. We demonstrate that CXCR4-predicted minority viruses present prior to transplantation were unable to rebound after transplantation due to their dependence on CCR5 for replication and high genetic barrier toward CXCR4 usage.

HIV antibody characterization as a method to quantify reservoir size during curative interventions.

Quantitative humoral profiling of recent samples from a human immunodeficiency virus (HIV)-infected adult who was cured following a delta32/delta32 CCR5 stem cell transplant in 2007 revealed no antibodies against p24, matrix, nucleocapsid, integrase, protease, and gp120, but low levels of antibodies against reverse transcriptase, tat, and gp41. Antibody levels to these HIV proteins persisted at high and stable levels in most noncontrollers, elite controllers, and antiretroviral-treated subjects, but a rare subset of controllers had low levels of antibodies against matrix, reverse transcriptase, integrase, and/or protease. Comprehensive HIV antibody profiles may prove useful for monitoring curative interventions.

Coregulation of HIV-1 dependency factors in individuals heterozygous to the CCR5-delta32 deletion.

BACKGROUND: CCR5-delta32 heterozygous individuals are susceptible to HIV-1. However, it is not clear if there is a relevant protective effect against transmission and a beneficial effect in terms of HIV progression which cannot be attributed to CCR5 surface density alone. Therefore we investigated HIV-1 dependency factors (HDF) which might be differently regulated in CCR5 wild type (WT) and CCR5-delta32 heterozygous individuals. METHODS: We examined CD34+ hematopoietic progenitor cells derived from bone marrow samples from 19 healthy volunteers, 12 individuals with CCR5 WT and 7 with heterozygous CCR5-delta32 deletion. Samples were analyzed using a global gene expression oligonucleotide microarray (HG-U133plus 2.0, Affymetrix Inc.). RESULTS: A total of 205 genes were found with altered expression (3fold difference, present call rate of 75%, p < 0.05) and 7 of these had a connection to HIV-1 pathogenesis. In 4 genes: TOP1, CXCR2, SREBF2, and TAP we found a different regulation which was consistent with a supposed beneficial effect for CCR5-delta32 heterozygotes. CONCLUSION: The CCR5-delta32 deletion is associated with other HDFs in HIV-1 pathogenesis as a possible explanation for beneficial effects regarding the deletion leading to a variant expression profile in heterozygous carriers of this mutation.

Challenges in detecting HIV persistence during potentially curative interventions: a study of the Berlin patient.

There is intense interest in developing curative interventions for HIV. How such a cure will be quantified and defined is not known. We applied a series of measurements of HIV persistence to the study of an HIV-infected adult who has exhibited evidence of cure after allogeneic hematopoietic stem cell transplant from a homozygous CCR5Δ32 donor. Samples from blood, spinal fluid, lymph node, and gut were analyzed in multiple laboratories using different approaches. No HIV DNA or RNA was detected in peripheral blood mononuclear cells (PBMC), spinal fluid, lymph node, or terminal ileum, and no replication-competent virus could be cultured from PBMCs. However, HIV RNA was detected in plasma (2 laboratories) and HIV DNA was detected in the rectum (1 laboratory) at levels considerably lower than those expected in ART-suppressed patients. It was not possible to obtain sequence data from plasma or gut, while an X4 sequence from PBMC did not match the pre-transplant sequence. HIV antibody levels were readily detectable but declined over time; T cell responses were largely absent. The occasional, low-level PCR signals raise the possibility that some HIV nucleic acid might persist, although they could also be false positives. Since HIV levels in well-treated individuals are near the limits of detection of current assays, more sensitive assays need to be developed and validated. The absence of recrudescent HIV replication and waning HIV-specific immune responses five years after withdrawal of treatment provide proof of a clinical cure.

Skewed X-inactivation patterns in ageing healthy and myelodysplastic haematopoiesis determined by a pyrosequencing based transcriptional clonality assay.

BACKGROUND: Investigation of X-chromosome inactivation patterns (XCIP) by determination of differential CpG-methylation has been widely applied for investigation of female cell clonality. Using this approach the clonal origin of various tumours has been corroborated. Controversially, strong age-related increase of peripheral blood (PB) cell clonality in haematologically healthy female subjects was reported. Recently, transcriptional XCIP ratio analysis challenged these results and questioned the suitability of methylation based clonality assays. METHODS: To reinvestigate XCIP-skewing in CD34, low-density mononuclear bone marrow (BM) as well as PB cells from healthy female subjects and patients with myelodysplastic syndromes (MDS), we established a transcriptional assay using pyrosequencing technique for quantification of single nucleotide polymorphism allele frequencies, representative for XCIP ratios. RESULTS: Our assay provides high sensitivity for XCIP ratio assessment as determined by standard curves, reproducibility, inter-marker correlation as well as correlation with the DNA-methylation based human androgen receptor (HUMARA) assay. Notably, in agreement with most studies investigating this issue, significant age-related increase of XCIP skewing in PB cells from healthy elderly female subjects was confirmed. Moreover, XCIP ratio analysis suggests even stronger clonal manifestation in BM and CD34 cells. In MDS, XCIP skewing levels were distinctively elevated as compared with controls of similar age and higher degrees were associated with poor clinical outcome. CONCLUSIONS: Transcriptional clonal profiling via pyrosequencing allows accurate assessment of XCIP ratios, confirms the validity of the DNA-methylation based HUMARA assay and reveals important insights into ageing healthy and myelodysplastic haematopoiesis.