Donor lymphocyte infusions for relapse after allogeneic transplantation: when, if and for whom?

Rapid single nucleotide polymorphism based method for hematopoietic chimerism analysis and monitoring using high-speed droplet allele-specific PCR and allele-specific quantitative PCR

BACKGROUND

Chimerism analysis is important for the evaluation of engraftment and predicting relapse following hematopoietic stem cell transplantation (HSCT). We developed a chimerism analysis for single nucleotide polymorphisms (SNPs), including rapid screening of the discriminable donor/recipient alleles using droplet allele-specific PCR (droplet-AS-PCR) pre-HSCT and quantitation of recipient DNA using AS-quantitative PCR (AS-qPCR) following HSCT.

METHODS

SNP genotyping of 20 donor/recipient pairs via droplet-AS-PCR and the evaluation of the informativity of 5 SNP markers for chimerism analysis were performed. Samples from six follow-up patients were analyzed to assess the chimerism via AS-qPCR. These results were compared with that determined by short tandem repeat PCR (STR-PCR).

RESULTS

Droplet-AS-PCR could determine genotypes within 8min. The total informativity using all 5 loci was 95% (19/20). AS-qPCR provided the percentage of recipient DNA in all 6 follow-up patients without influence of the stutter peak or the amplification efficacy, which affected the STR-PCR results.

CONCLUSION

The droplet-AS-PCR had an advantage over STR-PCR in terms of rapidity and simplicity for screening before HSCT. Furthermore, AS-qPCR had better accuracy than STR-PCR for quantification of recipient DNA following HSCT. The present chimerism assay compensates for the disadvantages of STR-PCR and is readily performable in clinical laboratories.

Fetal Microchimerism in Cancer Protection and Promotion: Current Understanding in Dogs and the Implications for Human Health

Fetal microchimerism is the co-existence of small numbers of cells from genetically distinct individuals living within a mother's body following pregnancy. During pregnancy, bi-directional exchange of cells occurs resulting in maternal microchimerism and even sibling microchimerism in offspring. The presence of fetal microchimerism has been identified with lower frequency in patients with cancers such as breast and lymphoma and with higher frequency in patients with colon cancer and autoimmune diseases. Microchimeric cells have been identified in healing and healed tissues as well as normal and tumor tissues. This has led to the hypothesis that fetal microchimerism may play a protective role in some cancers and may provoke other cancers or autoimmune disease. The long periods of risk for these diseases make it a challenge to prospectively study this phenomenon in human populations. Dogs get similar cancers as humans, share our homes and environmental exposures, and live compressed life-spans, allowing easier prospective study of disease development. This review describes the current state of understanding of fetal microchimerism in humans and dogs and highlights the similarities of the common cancers mammary carcinoma, lymphoma, and colon cancer between the two species. Study of fetal microchimerism in dogs might hold the key to characterization of the type and function of microchimeric cells and their role in health and disease. Such an understanding could then be applied to preventing and treating disease in humans.

Inhibition of Akt signaling promotes the generation of superior tumor-reactive T cells for adoptive immunotherapy

Effective T-cell therapy against cancer is dependent on the formation of long-lived, stem cell-like T cells with the ability to self-renew and differentiate into potent effector cells. Here, we investigated the in vivo existence of stem cell-like antigen-specific T cells in allogeneic stem cell transplantation (allo-SCT) patients and their ex vivo generation for additive treatment posttransplant. Early after allo-SCT, CD8+ stem cell memory T cells targeting minor histocompatibility antigens (MiHAs) expressed by recipient tumor cells were not detectable, emphasizing the need for improved additive MiHA-specific T-cell therapy. Importantly, MiHA-specific CD8+ T cells with an early CCR7+CD62L+CD45RO+CD27+CD28+CD95+ memory-like phenotype and gene signature could be expanded from naive precursors by inhibiting Akt signaling during ex vivo priming and expansion. This resulted in a MiHA-specific CD8+ T-cell population containing a high proportion of stem cell-like T cells compared with terminal differentiated effector T cells in control cultures. Importantly, these Akt-inhibited MiHA-specific CD8+ T cells showed a superior expansion capacity in vitro and in immunodeficient mice and induced a superior antitumor effect in intrafemural multiple myeloma-bearing mice. These findings provide a rationale for clinical exploitation of ex vivo-generated Akt-inhibited MiHA-specific CD8+ T cells in additive immunotherapy to prevent or treat relapse in allo-SCT patients.

Clinical trials of dendritic cell-based cancer vaccines in hematologic malignancies

The potential for the immune system to target hematological malignancies is demonstrated in the allogeneic transplant setting, where durable responses can be achieved. However, allogeneic transplantation is associated with significant morbidity and mortality related to graft versus host disease. Cancer immunotherapy has the capacity to direct a specific cytotoxic immune response against cancer cells, particularly residual cancer cells, in order to reduce the likelihood of disease relapse in a more targeted and tolerated manner. Ex vivo dendritic cells can be primed in various ways to present tumor associated antigen to the immune system, in the context of co-stimulatory molecules, eliciting a tumor specific cytotoxic response in patients. Several approaches to prime dendritic cells and overcome the immunosuppressive microenvironment have been evaluated in pre-clinical and early clinical trials with promising results. In this review, we summarize the clinical data evaluating dendritic cell based vaccines for the treatment of hematological malignancies.

Immune reconstitution after haploidentical hematopoietic stem cell transplantation

Haploidentical hematopoietic stem cell transplantation (HSCT) offers the benefits of rapid and nearly universal donor availability and has been accepted worldwide as an alternative treatment for patients with hematologic malignancies who do not have a completely HLA-matched sibling or who require urgent transplantation. Unfortunately, serious infections and leukemia relapse resulting from slow immune reconstitution remain the 2 most frequent causes of mortality in patients undergoing haploidentical HSCT, particularly in those receiving extensively T cell-depleted megadose CD34(+) allografts. This review summarizes advances in immune recovery after haploidentical HSCT, focusing on the immune subsets likely to have the greatest impact on clinical outcomes. The progress made in accelerating immune reconstitution using different strategies after haploidentical HSCT is also discussed. It is our belief that a predictive immune subset-guided strategy to improve immune recovery might represent a future clinical direction.

HLA-haploidentical donor lymphocyte infusions for patients with relapsed hematologic malignancies after related HLA-haploidentical bone marrow transplantation

Treatment of relapse after related HLA-haploidentical T cell-replete bone marrow transplantation (haploBMT) with post-transplantation cyclophosphamide (PTCy) using haploidentical donor lymphocyte infusion (haploDLI) is not documented. All patients who received haploDLI after haploBMT with PTCy between June 2003 and October 2012 were identified and assessed for graft-versus-host disease (GVHD) and outcomes. Forty patients received 52 haploDLI doses. Sixteen patients had acute myeloid leukemia, 11 had lymphomas, and 34 had nonmyeloablative conditioning before haploBMT. The median time from haploBMT to relapse was 183 (range, 0 to 1399) days. The median age at haploDLI was 48 (range, 3 to 70) years. The first haploDLI doses were 1 × 10(5) CD3(+) cells/kg with subsequent escalation. The most commonly used first haploDLI dose was 1 × 10(6) CD3(+) cells/kg. The median follow-up after haploDLI was 7 (mean, 15.4; range, .5 to 96) months for the entire cohort, and 17.5 (mean, 28; range, 2.4 to 96) months for the responders. Acute GVHD developed in 10 patients (25%), 6 patients had grade 3 to 4, and 3 developed chronic GVHD. Twelve (30%) patients achieved a complete response (CR) with a median duration of 11.8 (mean, 22.5; range, .4 to 94) months. At last follow-up, 8 responders were alive in CR; 6 for over a year. HaploDLI for relapse after haploBMT is associated with acceptable toxicities and can result in durable responses.

The health effects of fetal microchimerism can be modeled in companion dogs

Fetal microchimerism (FMC) has been described to have a range of effects on health and disease. Y-chromosomal DNA has been detected in Golden Retrievers suggesting persistent FMC. In that report, nine dogs had evidence of microchimerism without prior pregnancy. To further understand this finding, a dam with prior male live births giving birth to her fourth litter of puppies, all females, was evaluated for FMC along with two of her daughters. All three female dogs had evidence of Y-chromosomal DNA in their blood. This suggests that male cells carried by the dam from previous pregnancy trafficked to her daughters to establish microchimerism in younger siblings. Companion dogs share many of the same cancers as humans, have out-bred genetics, and share the human environment, making them optimal models of human disease. Understanding the impact of FMC on health and disease of dogs could elucidate mechanisms useful for clinical interventions in humans.