Debra G. B. Leonard

Successful transduction of liver in hemophilia by AAV-Factor IX and limitations imposed by the host immune response

We have previously shown that a single portal vein infusion of a recombinant adeno-associated viral vector (rAAV) expressing canine Factor IX (F.IX) resulted in long-term expression of therapeutic levels of F.IX in dogs with severe hemophilia B. We carried out a phase 1/2 dose-escalation clinical study to extend this approach to humans with severe hemophilia B. rAAV-2 vector expressing human F.IX was infused through the hepatic artery into seven subjects. The data show that: (i) vector infusion at doses up to 2 × 1012 vg/kg was not associated with acute or long-lasting toxicity; (ii) therapeutic levels of F.IX were achieved at the highest dose tested; (iii) duration of expression at therapeutic levels was limited to a period of ∼8 weeks; (iv) a gradual decline in F.IX was accompanied by a transient asymptomatic elevation of liver transaminases that resolved without treatment. Further studies suggested that destruction of transduced hepatocytes by cell-mediated immunity targeting antigens of the AAV capsid caused both the decline in F.IX and the transient transaminitis. We conclude that rAAV-2 vectors can transduce human hepatocytes in vivo to result in therapeutically relevant levels of F.IX, but that future studies in humans may require immunomodulation to achieve long-term expression*.

Ex vivo expansion of polyclonal and antigen-specific cytotoxic T lymphocytes by artificial APCs expressing ligands for the T-cell receptor, CD28 and 4-1BB

The ex vivo priming and expansion of human cytotoxic T lymphocytes (CTLs) has potential for use in immunotherapy applications for cancer and infectious diseases. To overcome the difficulty in obtaining sufficient numbers of CTLs, we have developed artificial antigen-presenting cells (aAPCs) expressing ligands for the T-cell receptor (TCR) and the CD28 and 4-1BB co-stimulatory surface molecules. These aAPCs reproducibly activate and rapidly expand polyclonal or antigen-specific CD8+ T cells. The starting repertoire of CD8+ T cells was preserved during culture. Furthermore, apoptosis of cultured CD8+ T cells was diminished by this approach. This approach may have important therapeutic implications for adoptive immunotherapy.

Graft-Versus-Tumor Induction With Donor Leukocyte Infusions as Primary Therapy for Patients With Malignancies

PURPOSE Histocompatible allogeneic donor leukocyte infusions (DLIs) were administered as primary cancer therapy in a phase I trial to determine (1) whether mixed chimerism could be detected without a prior allogeneic transplantation, (2) the toxicity of primary DLI, and (3) whether a graft-versus-tumor (GVT) reaction could be observed. PATIENTS AND METHODS Eighteen patients were studied. Patients received interferon alfa-2b for a minimum of 4 weeks, followed by DLI (level 1). Patients with no toxicity or engraftment were eligible to receive cytarabine or cyclophosphamide followed by another course of DLI (level 2). Engraftment was determined using polymerase chain reaction amplification of donor and host-specific DNA polymorphisms. RESULTS Donor cells were detected in the blood in 14 of 16 assessable patients within 1 hour of DLI. Chimerism detectable 4 weeks after DLI was observed in four patients, and five patients were not assessable. Prior autologous transplantation was associated with late chimerism (P =.0014). Acute graft-versus-host disease (GVHD) occurred in four of 16 assessable patients (grade 1, two patients; grade 2, one patient; grade 4, one patient). One patient with grade 4 acute GVHD developed pancytopenia. Only the four patients treated after prior autologous transplantation developed acute GVHD (P =.0005). Three of four patients with acute GVHD and late chimerism responded to primary DLI, and one patient was not assessable for response. CONCLUSION Allogeneic adoptive immunotherapy resulted in sustained chimerism, acute GVHD, and a GVT response in heavily pretreated patients. This indicates that it may be possible to generate a direct GVT response for patients with malignancies without the need for intensive conditioning therapy immediately before DLI. Immunosuppression may be required for sustained donor cell engraftment.

Proteolipid protein is necessary in peripheral as well as central myelin

Alternative products of the proteolipid protein gene (PLP), proteolipid protein (PLP) and DM20, are major components of compact myelin in the central nervous system, but quantitatively minor constituents of Schwann cells. A family with a null allele of PLP has a less severe CNS phenotype than those with other types of PLP mutations. Moreover, individuals with PLP null mutations have a demyelinating peripheral neuropathy, not seen with other PLP mutations of humans or animals. Direct analysis of normal peripheral nerve demonstrates that PLP is localized to compact myelin. This and the clinical and pathologic observations of the PLP null phenotype indicate that PLP/DM20 is necessary for proper myelin function both in the central and peripheral nervous systems.

Diagnostic testing fails the test

The pitfalls of patents are illustrated by the case of haemochromatosis.

Opportunities and challenges associated with clinical diagnostic genome sequencing: a report of the Association for Molecular Pathology.

This report of the Whole Genome Analysis group of the Association for Molecular Pathology illuminates the opportunities and challenges associated with clinical diagnostic genome sequencing. With the reality of clinical application of next-generation sequencing, technical aspects of molecular testing can be accomplished at greater speed and with higher volume, while much information is obtained. Although this testing is a next logical step for molecular pathology laboratories, the potential impact on the diagnostic process and clinical correlations is extraordinary and clinical interpretation will be challenging. We review the rapidly evolving technologies; provide application examples; discuss aspects of clinical utility, ethics, and consent; and address the analytic, postanalytic, and professional implications.

Breaking a Vicious Cycle

New tumor-biomarker diagnostics will emerge along with changes in regulation, development, reimbursement, and investment practices. Despite prodigious advances in tumor biology research, few tumor-biomarker tests have been adopted as standard clinical practice. This lack of reliable tests stems from a vicious cycle of undervaluation, resulting from inconsistent regulatory standards and reimbursement, as well as insufficient investment in research and development, scrutiny of biomarker publications by journals, and evidence of analytical validity and clinical utility. We offer recommendations designed to serve as a roadmap to break this vicious cycle and call for a national dialogue, as changes in regulation, reimbursement, investment, peer review, and guidelines development require the participation of all stakeholders.

Hepatosplenic and Subcutaneous Panniculitis-Like γ/δ T Cell Lymphomas Are Derived from Different Vδ Subsets of γ/δ T Lymphocytes

Gamma/delta T cell lymphomas (γ/δ TCL) represent rare, often aggressive types of T cell malignancy that are clinically and pathologically diverse. Most γ/δ TCL occur as a hepatosplenic or subcutaneous type. To date, analysis of the T cell receptor δ (TCRδ) gene repertoire of hepatosplenic γ/δ TCL (γ/δ HSTCL) and subcutaneous panniculitis-like γ/δ TCL (γ/δ SPTCL) has been reported only in a limited number of cases. In this study we analyzed 11 γ/δ HSTCL and 4 γ/δ SPTCL by polymerase chain reaction and immunostaining to determine their usage of the Vδ subtypes (Vδ1–6). It is noteworthy that 10 of 11 γ/δ HSTCL expressed the Vδ1 gene. The remaining case also expressed T cell receptor δ (TCRδ) as determined by flow cytometry and TCRδ rearrangement in Southern blot. However, the Vδ gene expressed by this lymphoma could not be determined, which suggests usage of an as yet unidentified Vδ gene. In striking contrast to the γ/δ HSTCL, all 4 γ/δ SPTCL expressed the Vδ2 gene. Our data demonstrate that γ/δ HSTCL are preferentially derived from the Vδ1 subset of γ/δ T lymphocytes, whereas γ/δ SPTCL are preferentially derived from the Vδ2 subset. The pattern of Vδ gene expression in HSTCL and SPTCL corresponds to the respective, predominant γ/δ T cell subsets normally found in the spleen and skin. This finding suggests that γ/δ TCL are derived from normal γ/δ T lymphocytes which reside in the affected tissues. Furthermore, the selective, lymphoma type-specific Vδ gene segment usage may provide a molecular tool to distinguish better among various types of γ/δ TCL lymphoma particularly in the clinically advanced, widely disseminated cases.

Association of Susceptibility Alleles in ELAC2/HPC2, RNASEL/HPC1, and MSR1 with Prostate Cancer Severity in European American and African American Men

Reported associations of ELAC2/HPC2, RNASEL/HPC1, and MSR1 with prostate cancer have been inconsistent and understudied in African Americans. We evaluated the role of 16 sequence variants in these genes with prostate cancer using 888 European American and 131 African American cases, and 473 European American and 163 African American, controls. We observed significant differences in ELAC2, RNASEL, and MSR1 allele frequencies by race. However, we did not observe significant associations between prostate cancer and any variants examined for both races combined. Associations were observed when stratified by race, family history, or disease severity. European American men homozygous for MSR1 IVS7delTTA had an elevated risk for localized stage [odds ratio, (OR), 3.5; 95% confidence interval (95% CI), 1.4-6.9], low-grade (OR, 3.2; 95% CI, 1.4-7.3) disease overall, and with low-grade (OR, 2.9; 95% CI, 1.2-7.2) or late-stage disease (OR, 5.2; 95% CI, 1.1-25.7) in family history–negative African Americans. MSR1 Arg293X was associated with family history–negative high-grade disease (OR, 4.0; 95% CI, 1.1-14.1) in European Americans. RNASEL Arg462Gln was associated with low-grade (OR, 1.5; 95% CI, 1.04-2.2) and early-stage (OR, 1.5; 95% CI, 1.02-2.1) disease in family history–negative European Americans. In family history–positive individuals, Arg462Gln was inversely associated with low-grade (OR, 0.43; 95% CI, 0.21-0.88) and low-stage (OR, 0.46; 95% CI, 0.22-0.95) disease. In African Americans, Arg462Gln was associated with positive family history high-stage disease (OR, 14.8; 95% CI, 1.6-135.7). Meta-analyses revealed significant associations of prostate cancer with MSR1 IVS7delTTA, −14,742 A>G, and Arg293X in European Americans; Asp174Tyr in African Americans; RNASEL Arg462Gln in European Americans overall and in family history–negative disease; and Glu265X in family history–positive European Americans. Therefore, MSR1 and RNASEL may play a role in prostate cancer progression and severity.

Duplications and de novo deletions of the SMNt gene demonstrated by fluorescence-based carrier testing for spinal muscular atrophy.

Approximately 95% of individuals with spinal muscular atrophy (SMA) lack both copies of the SMNt gene at 5q13. The presence of a nearly identical centromeric homolog of the SMNt gene, SMNc, necessitates a quantitative polymerase chain reaction approach to direct carrier testing. Adapting a radioactivity-based method described previously, multiplex polymerase chain reaction was performed using fluorescently labeled primers followed by analysis on an ABI 373a DNA sequencer. The SMNt copy number was calculated from ratios of peak areas using both internal and genomic standards. Samples from 60 presumed carriers (50 parents of affected individuals and 10 relatives implicated by linkage analysis) and 40 normal control individuals were tested. Normalized results (to the mean of five or more control samples harboring two copies of the SMNt gene) were consistently within the ranges of 0.4 to 0.6 for carriers (one copy) and 0.8 to 1.2 for normal controls (two copies), without overlap. Combining linkage analyses with direct carrier test results demonstrated de novo deletions associated with crossovers, unaffected individuals carrying two SMNt gene copies on one chromosome and zero SMNt gene copies on the other chromosome, and unaffected individuals with three copies of the SMNt gene. This report demonstrates that fluorescence-based carrier testing for SMA is accurate, reproducible, and useful for genetic risk assessment, and that carrier testing may need to be combined with linkage analysis in certain circumstances.