Aberrant T-cell exhaustion in severe combined immunodeficiency survivors with poor T-cell reconstitution after transplantation

BACKGROUND

Severe combined immunodeficiency (SCID) comprises rare inherited disorders of immunity that require definitive treatment through hematopoietic cell transplantation (HCT) or gene therapy for survival. Despite successes of allogeneic HCT, many SCID patients experience incomplete immune reconstitution, persistent T-cell lymphopenia, and poor long-term outcomes.

OBJECTIVE

We hypothesized that CD4+ T-cell lymphopenia could be associated with a state of T-cell exhaustion in previously transplanted SCID patients.

METHODS

We analyzed markers of exhaustion in blood samples from 61 SCID patients at a median of 10.4 years after HCT.

RESULTS

Compared to post-HCT SCID patients with normal CD4+ T-cell counts, those with poor T-cell reconstitution showed lower frequency of naive CD45RA+/CCR7+ T cells, recent thymic emigrants, and TCR excision circles. They also had a restricted TCR repertoire, increased expression of inhibitory receptors (PD-1, 2B4, CD160, BTLA, CTLA-4), and increased activation markers (HLA-DR, perforin) on their total and naive CD8+ T cells, suggesting T-cell exhaustion and aberrant activation, respectively. The exhaustion score of CD8+ T cells was inversely correlated with CD4+ T-cell count, recent thymic emigrants, TCR excision circles, and TCR diversity. Exhaustion scores were higher among recipients of unconditioned HCT, especially when further in time from HCT. Patients with fewer CD4+ T cells showed a transcriptional signature of exhaustion.

CONCLUSIONS

Recipients of unconditioned HCT for SCID may develop late post-HCT T-cell exhaustion as a result of diminished production of T-lineage cells. Elevated expression of inhibitory receptors on their T cells may be a biomarker of poor long-term T-cell reconstitution.

Change in erythropoietin pharmacokinetics following hematopoietic transplantation

Pre-clinical studies have demonstrated that bone marrow ablation has a profound effect in decreasing erythropoietin (EPO) elimination. The study's objective was to determine in humans if EPO pharmacokinetics (PKs) are perturbed following bone marrow ablation. EPO PK studies were performed in eight subjects, aged 4 to 61 years, undergoing fully myeloablative hematopoietic stem cell transplantation. Serial PK studies using intravenous injection of recombinant human EPO (92+/-2.0 U/kg) (mean+/-SEM) were carried out during four periods of altered marrow integrity: baseline pre-ablation, post-ablation pre-transplant, early post-transplant pre-engraftment, and late post-transplant full engraftment. Compared with baseline, post-ablation pre-transplant and early post-transplant EPO PKs demonstrated declines in clearance increases in terminal elimination half-life of 36 and 95%, respectively. Clearance and half-life returned to baseline following full engraftment. The association of EPO elimination with decreased bone marrow activity in patients undergoing transplantation conclusively establishes the bone marrow as a key determinant of EPO elimination in humans.

Hydroxychloroquine for the treatment of chronic graft-versus-host disease

Chronic graft-versus-host disease (GVHD) is a major complication of allogeneic bone marrow transplantation. Both the disease and the medications used to treat it are associated with significant morbidity and mortality. The manifestations of chronic GVHD often resemble those of autoimmune disorders. Hydroxychloroquine (HCQ) is a 4-aminoquinoline antimalarial drug used for the treatment of autoimmune diseases. HCQ interferes with antigen processing and presentation, cytokine production, and cytotoxicity and is synergistic with cyclosporine and tacrolimus in vitro. Forty patients with steroid-resistant or steroid-dependent chronic GVHD were enrolled in a phase 2 trial of HCQ 800 mg (12 mg/kg) per day. Three complete responses and 14 partial responses were seen in 32 evaluable patients (53% response rate). All responders tolerated a >50% reduction in their steroid dose while receiving HCQ. Clinical response occurred at a median of 8 weeks (range, 4 to 24 weeks). No hematologic, hepatic, renal, or retinal toxicity was associated with HCQ. In light of its mechanisms of action, clinical activity for GVHD, and low toxicity profile, HCQ may be useful in a multiagent approach for the treatment of extensive chronic GVHD.

Hydroxychloroquine inhibits calcium signals in T cells: a new mechanism to explain its immunomodulatory properties

Hydroxychloroquine (HCQ), a lysosomotropic amine, is an immunosuppressive agent presently being evaluated in bone marrow transplant patients to treat graft-versus-host disease. While its immunosuppressive properties have been attributed primarily to its ability to interfere with antigen processing, recent reports demonstrate HCQ also blocks T-cell activation in vitro. To more precisely define the T-cell inhibitory effects of HCQ, the authors evaluated T-cell antigen receptor (TCR) signaling events in a T-cell line pretreated with HCQ. In a concentration-dependent manner, HCQ inhibited anti-TCR-induced up-regulation of CD69 expression, a distal TCR signaling event. Proximal TCR signals, including inductive protein tyrosine phosphorylation, tyrosine phosphorylation of phospholipase C gamma1, and total inositol phosphate production, were unaffected by HCQ. Strikingly, anti-TCR-crosslinking-induced calcium mobilization was significantly inhibited by HCQ, particularly at the highest concentrations tested (100 micromol/L) in both T-cell lines and primary T cells. HCQ, in a dose-dependent fashion, also reduced a B-cell antigen receptor calcium signal, indicating this effect may be a general property of HCQ. Inhibition of the calcium signal correlated directly with a reduction in the size of thapsigargin-sensitive intracellular calcium stores in HCQ-treated cells. Together, these findings suggest that disruption of TCR-crosslinking-dependent calcium signaling provides an additional mechanism to explain the immunomodulatory properties of HCQ.

Poor outcome in children with refractory/relapsed leukemia undergoing bone marrow transplantation with mismatched family member donors

The utility of bone marrow transplantation for childhood leukemia in patients unable to achieve a remission prior to transplant is controversial. To address this issue, we analyzed a subset of patients with advanced leukemia entered on prospective transplant trials at our hospital. Fifty-eight patients with ALL or AML (age 1-19) were identified. They had failed standard chemotherapy and were in relapse (22 in 1st, 27 in 2nd, three in 3rd, and three in 4th) or had never achieved an initial remission (three) at the time of transplant. Fifty-two patients received marrow from mismatched family members (haplo or DR-identical), while six received marrow from matched siblings. Most patients received myeloablative therapy consisting of total body irradiation, etoposide, cyclophosphamide, and cytosine arabinoside. Marrow from mismatched donors was T cell depleted. Only one of 52 patients transplanted with a mismatched donor survived long-term while three of six patients transplanted in relapse with a fully matched sibling donor are alive 6-10 years post BMT. The major causes of death were infection (39%) and relapse (28%). Acute GVHD grade III-IV was noted in 7% of patients. A comparable group of patients with leukemia transplanted at our center in remission using similarly mismatched family member donors (haplo or DR-identical) had an event-free survival of 28%. In conclusion, our data suggest that BMT utilizing mismatched family member donors is a poor option for patients in relapse at the time of transplant. New treatment strategies need to be developed to effectively manage these patients.

Ten-year experience of unrelated bone marrow donor transplants in children with malignant and non-malignant conditions

Children who require a marrow transplant may receive such hematopoietic cells from one of many sources. This study reviews the experience of one center with 58 children who received marrow from unrelated donors over a 10-year period. These children had a variety of malignant and non-malignant diseases. During that time period, only three of these children had failed to meet engraftment criteria. All donor marrow specimens were T-lymphocyte-depleted using an antibody/complement methodology. No difference was demonstrated in outcome between donors who were perfectly HLA-DR DNA matched versus those who were only partially matched. The increased size of various marrow donor registries has increased the number of potential donors available for these patients. The lack of a requirement for perfect matching means that there is an ever-increasing number of donors available. No graft-versus-host disease (GvHD) or grade III-IV GvHD was associated with a poorer outcome. Stable, long-term engraftment with minimal morbidity has been demonstrated in these children as evidenced by stability of survival curves by two years after marrow transplant.

Defective expression of p56lck in an infant with severe combined immunodeficiency

Severe combined immune deficiency (SCID) is a heterogeneous disorder characterized by profound defects in cellular and humoral immunity. We report here an infant with clinical and laboratory features of SCID and selective CD4 lymphopenia and lack of CD28 expression on CD8(+) T cells. T cells from this patient showed poor blastogenic responses to various mitogens and IL-2. Other T cell antigen receptor- induced responses, including upregulation of CD69, were similarly inhibited. However, more proximal T cell antigen receptor signaling events, such as anti-CD3 induced protein tyrosine phosphorylation, phosphorylation of mitogen-associated protein kinase, and calcium mobilization were intact. Although p59fyn and ZAP-70 protein tyrosine kinases were expressed at normal levels, a marked decrease in the level of p56lck was noted. Furthermore, this decrease was associated with the presence of an alternatively spliced lck transcript lacking the exon 7 kinase encoding domain. These data suggest that a deficiency in p56lck expression can produce a SCID phenotype in humans.

Long-term follow-up of Keller arthroplasty with irradiated costochondral implants

The authors present results of long-term follow-up of seven patients whose degenerative disease of the first metatarsophalangeal joint was treated with irradiated chondral graft implantation arthroplasty. In appropriate candidates, this procedure is a reasonable alternative to Keller arthroplasty alone, arthrodesis, and nonbiologic implant arthroplasty.

Chevron bunionectomy fixation: in vitro stability assessment of plate-and-screw system compared with Kirschner wire

Many methods for internal fixation of the Chevron bunionectomy have been described. Currently available fixation devices stabilize the osteotomy sufficiently to ensure healing. Each has unique advantages and disadvantages. A low-profile plate buried beneath capsular tissue eliminates some complications of other forms of fixation. The authors compared the structural characteristics of a low-profile plate-and-screw system and of a single Kirschner wire. Testing was performed on dissected human cadaveric specimens by using a Telos strain gauge. Loads were applied both from the medial to the lateral aspect and from the plantar to the dorsal aspect at the capital fragment. Results indicate that both modes of fixation can resist Chevron osteotomy displacement in vitro.

Restoration of CD2-mediated signaling by a chimeric membrane protein including the cytoplasmic sequence of CD45

We showed previously that the TCR and CD2 fail to couple efficiently with their signal transduction machinery in J45.01, a CD45-deficient variant of the Jurkat T-cell line. Transfection into J45.01 of a cDNA encoding a chimeric membrane protein containing the cytoplasmic sequence of CD45 and extracellular and transmembrane sequences derived from the A2 allele of MHC class I rescues proximal signaling events after TCR stimulation. In this report, we describe rescue of CD2-mediated signaling and evaluate further the characteristics of TCR signaling in J45.01 after expression of the chimeric protein. Cells expressing the chimeric molecule demonstrate TCR- and CD2-mediated increases in PTK activity and PI turnover. Stimulation of the TCR and CD2 on the transfected cells also results in the expression of CD69 on the cell surface, a more distal signaling event. Although these measures of signal transduction via the TCR and CD2 are restored in the transfected cells, the magnitude of the responses are less than those seen in the wild-type Jurkat cells. These findings demonstrate that the cytoplasmic domain of CD45, expressed as a chimeric membrane protein, is sufficient for mediating signal transduction through CD2 as well as through the TCR complex. In addition, these results suggest that the extracellular and/or transmembrane domains of CD45 may contribute to the efficiency of signal transduction.

The association between CD45 and lck does not require CD4 or CD8 and is independent of T cell receptor stimulation

CD45, the major transmembrane tyrosine phosphatase of lymphoid cells, is required for optimal signaling via a number of receptors. A model for how CD45 regulates signaling is that it controls phosphorylation of the COOH-terminal tyrosine of src family kinases. We have shown that CD45 physically associates with lck, one src kinase. Others have shown that CD45 also interacts with the CD4 and CD8 surface antigens expressed on many T cells. In this report we examine further the relationship between CD45 and lck in a CD4+ T cell line and in peripheral T cells. We show now that CD45 associates with lck independently of both CD4 and CD8. We show also the time course of an association between CD45 and a form of lck that migrates at an apparent higher molecular mass. Finally, we demonstrate that the interaction between CD45, lck, and a previously reported 32-34 kD protein is stable after stimulation of T cells.

Rescue of signaling by a chimeric protein containing the cytoplasmic domain of CD45

Surface expression of the CD45 tyrosine phosphatase is essential for the T cell antigen receptor (TCR) to couple optimally with its second messenger pathways. CD45 may be required to dephosphorylate a TCR-activated protein tyrosine kinase, which then transduces an activation signal from the TCR. A chimeric molecule that contained extracellular and transmembrane sequences from an allele of a major histocompatibility class I molecule and cytoplasmic sequences of CD45 restored TCR signaling in a CD45-deficient mutant T cell line. Thus, expression of the complex extracellular domain of CD45 is not required for the TCR to couple to its signaling machinery.

Compartment pressure in the foot. Analysis of normal values and measurement technique

This clinical trial was carried out to verify the validity of the current objective compartment pressure parameters described in the forearm and leg for use in the foot. The authors evaluated the compartment pressures of the central plantar compartment in 25 normal volunteers (94 separate measurements). In addition to determining an average normal foot compartment pressure, two methods of measurement were compared. Results showed no significant difference in normal values through the use of an arterial line monitor technique (5.98 +/- 2.78 mm Hg [SD]) as compared with a Stryker intracompartmental pressure monitor (4.69 +/- 2.62 mm Hg [SD]). It was found that pedal edema caused a statistically significant increase in pressures. The authors propose a standard technique for pedal compartment pressure measurement and discuss diagnosis and management of compartment syndrome in the foot.

Compartment syndrome of the foot

Compartment syndrome is a relatively common posttraumatic diagnosis in the forearm and lower leg. Although the existence of this syndrome in the foot has been documented, it is not a well-known entity. Because delays in recognition and treatment can lead to catastrophic complications, practitioners should be aware of both its existence and its presentation. The authors present a case report of pedal compartment syndrome and a discussion of the literature pertaining to its diagnosis and treatment.

Renal cell carcinoma and osseous metastases. Case report and literature review

Renal cell carcinoma is one of the great mimics in medicine. The diagnosis is complicated by clinical presentations involving a multitude of symptoms, often associated with the sites of metastasis. A high percentage of renal cell carcinomas have metastasized at the time of initial presentation, and symptoms associated with this metastasis may actually initiate the diagnosis. Because the site of tumor origin is frequently unknown, a diagnostic strategy for identifying the primary source has been proposed. The prognosis for renal cell carcinoma with metastasis is poor, with fewer than 9% of patients surviving at 5 years. Consequently, treatment is directed primarily at palliation of painful symptoms and stabilization of bony structures. With these goals in mind, treatment modalities run the gamut from radiotherapy, to curettage with polymethyl methacrylate augmentation, to amputation. In the case reported here, renal cell carcinoma was diagnosed in the course of evaluation of a painful lytic lesion of the foot. Treatment alternatives and associated risks and complications were discussed at some length and the patient chose curettage and packing with polymethyl methacrylate in combination with radiotherapy. This approach was successful in palliation of pain and maintenance of walking ability and independence.

Surgical approach for enlarged peroneal tubercles

The peroneal tubercle is an anatomic landmark consistently found on the lateral aspect of the calcaneus. Its enlargement can be either congenital or acquired. In the past, surgical treatment of enlarged tubercles has consisted of simple excision of the tubercle. The authors have presented a technique to preserve the gliding facet that is often found on the inferior surface of the tubercle.

Extensor hallucis longus tendon transfer for correction of hallux varus

The authors describe radiographic results from nine patients in whom hallux varus was repaired by transferring the extensor hallucis longus tendon (EHLT) under the deep transverse intermetatarsal ligament into the proximal-lateral base of the proximal phalanx. X-ray films revealed clinically significant changes in biomechanical relations, specifically in the hallux abductus angle. No clinically significant changes were seen in the intermetatarsal angle. The EHLT transfer procedure described is a valuable surgical alternative for correction of iatrogenic hallux varus deformity when combined with the appropriate adjunctive procedures.