Annick Lim

egc, A Highly Prevalent Operon of Enterotoxin Gene, Forms a Putative Nursery of Superantigens in Staphylococcus aureus

The recently described staphylococcal enterotoxins (SE) G and I were originally identified in two separate strains of Staphylococcus aureus. We have previously shown that the corresponding genes seg and sei are present in S. aureus in tandem orientation, on a 3.2-kb DNA fragment (Jarraud, J. et al. 1999. J. Clin. Microbiol. 37:2446–2449). Sequence analysis of seg-sei intergenic DNA and flanking regions revealed three enterotoxin-like open reading frames related to seg and sei, designated sek, sel, and sem, and two pseudogenes, ψ ent1 and ψ ent2. RT-PCR analysis showed that all these genes, including seg and sei, belong to an operon, designated the enterotoxin gene cluster (egc). Recombinant SEG, SEI, SEK, SEL, and SEM showed superantigen activity, each with a specific Vβ pattern. Distribution studies of genes encoding superantigens in clinical S. aureus isolates showed that most strains harbored such genes and in particular the enterotoxin gene cluster, whatever the disease they caused. Phylogenetic analysis of enterotoxin genes indicated that they all potentially derived from this cluster, identifying egc as a putative nursery of enterotoxin genes.

Implication of γδ T cells in the human immune response to cytomegalovirus

In normal individuals, γδ T cells account for less than 6% of total peripheral T lymphocytes and mainly express T-cell receptor (TCR) Vδ2-Vγ9 chains. We have previously observed a dramatic expansion of γδ T cells in the peripheral blood of renal allograft recipients only when they developed cytomegalovirus (CMV) infection. This increase was long lasting (more than 1 year), was associated with an activation of γδ T cells, and concerned only Vδ1 or Vδ3 T-cell subpopulations. Analysis of γδ TCR junctional diversity revealed that CMV infection in these patients was accompanied by (a) a marked restriction of CDR3 size distribution in Vδ3 and, to a lesser extent, in Vδ1 chains; and (b) a selective expansion of Vδ1 cells bearing recurrent junctional amino acid motifs. These features are highly suggestive of an in vivo antigen-driven selection of γδ T-cell subsets during the course of CMV infection. Furthermore, Vδ1 and Vδ3 T cells from CMV-infected kidney recipients were able to proliferate in vitro in the presence of free CMV or CMV-infected fibroblast lysates but not uninfected or other herpes virus–infected fibroblast lysates. This in vitro expansion was inhibited by anti-γδ TCR mAb’s. These findings suggest that a population of γδ T cells might play an important role in the immune response of immunosuppressed patients to CMV infection.

A Modified γ-Retrovirus Vector for X-Linked Severe Combined Immunodeficiency

BACKGROUND In previous clinical trials involving children with X-linked severe combined immunodeficiency (SCID-X1), a Moloney murine leukemia virus-based γ-retrovirus vector expressing interleukin-2 receptor γ-chain (γc) complementary DNA successfully restored immunity in most patients but resulted in vector-induced leukemia through enhancer-mediated mutagenesis in 25% of patients. We assessed the efficacy and safety of a self-inactivating retrovirus for the treatment of SCID-X1. METHODS We enrolled nine boys with SCID-X1 in parallel trials in Europe and the United States to evaluate treatment with a self-inactivating (SIN) γ-retrovirus vector containing deletions in viral enhancer sequences expressing γc (SIN-γc). RESULTS All patients received bone marrow-derived CD34+ cells transduced with the SIN-γc vector, without preparative conditioning. After 12.1 to 38.7 months of follow-up, eight of the nine children were still alive. One patient died from an overwhelming adenoviral infection before reconstitution with genetically modified T cells. Of the remaining eight patients, seven had recovery of peripheral-blood T cells that were functional and led to resolution of infections. The patients remained healthy thereafter. The kinetics of CD3+ T-cell recovery was not significantly different from that observed in previous trials. Assessment of insertion sites in peripheral blood from patients in the current trial as compared with those in previous trials revealed significantly less clustering of insertion sites within LMO2, MECOM, and other lymphoid proto-oncogenes in our patients. CONCLUSIONS This modified γ-retrovirus vector was found to retain efficacy in the treatment of SCID-X1. The long-term effect of this therapy on leukemogenesis remains unknown. (Funded by the National Institutes of Health and others; ClinicalTrials.gov numbers, NCT01410019, NCT01175239, and NCT01129544.).

The Repertoires of Circulating Human CD8+ Central and Effector Memory T Cell Subsets Are Largely Distinct

Memory T cells are divided into central and effector subsets with distinct functions and homing capabilities. We analyzed the composition and dynamics of the CD8(+) T cell repertoire of these subsets within the peripheral blood of four healthy individuals. Both subsets had largely distinct and autonomous TCRbeta repertoires. Their composition remained stable over a 9 month period, during which no cell passage between these subsets was detected despite important size variation of several clones. In one donor, four out of six TCRbeta clonotypes specific for the influenza A virus were detected in the central subset only, while the two others were shared. Altogether, these observations suggest that most effector memory T cells may not have derived from the central memory subset.

A novel immunodeficiency associated with hypomorphic RAG1 mutations and CMV infection

Amorphic mutations in the recombination activating genes RAG1 and RAG2 have been reported to cause T- B- SCID, whereas hypomorphic mutations led to the expansion of a few autoimmune T cell clones responsible for the Omenn syndrome phenotype. We report here a novel clinical and immunological phenotype associated with recessive RAG1 hypomorphic mutations in 4 patients from 4 different families. The immunological phenotype consists of the oligoclonal expansion of TCR gammadelta T cells combined with TCR alphabeta T cell lymphopenia. The clinical phenotype consists of severe, disseminated CMV infection and autoimmune blood cell manifestations. Repertoire studies suggest that CMV infection, in the setting of this particular T cell immunodeficiency, may have driven the TCR gammadelta T cell clonal expansion. This observation extends the range of clinical and immunological phenotypes associated with RAG mutations, emphasizing the role of the genetic background and microbial environment in determining disease phenotype.

MST1 mutations in autosomal recessive primary immunodeficiency characterized by defective naive T-cell survival

The molecular mechanisms that underlie T-cell quiescence are poorly understood. In the present study, we report a primary immunodeficiency phenotype associated with MST1 deficiency and primarily characterized by a progressive loss of naive T cells. The in vivo consequences include recurrent bacterial and viral infections and autoimmune manifestations. MST1-deficient T cells poorly expressed the transcription factor FOXO1, the IL-7 receptor, and BCL2. Conversely, FAS expression and the FAS-mediating apoptotic pathway were up-regulated. These abnormalities suggest that increased cell death of naive and proliferating T cells is the main mechanism underlying this novel immunodeficiency. Our results characterize a new mechanism in primary T-cell immunodeficiencies and highlight a role of the MST1/FOXO1 pathway in controlling the death of human naive T cells.

Outcomes Following Gene Therapy in Patients With Severe Wiskott-Aldrich Syndrome

IMPORTANCE Wiskott-Aldrich syndrome is a rare primary immunodeficiency associated with severe microthrombocytopenia. Partially HLA antigen-matched allogeneic hematopoietic stem cell (HSC) transplantation is often curative but is associated with significant comorbidity. OBJECTIVE To assess the outcomes and safety of autologous HSC gene therapy in Wiskott-Aldrich syndrome. DESIGN, SETTING, AND PARTICIPANTS Gene-corrected autologous HSCs were infused in 7 consecutive patients with severe Wiskott-Aldrich syndrome lacking HLA antigen-matched related or unrelated HSC donors (age range, 0.8-15.5 years; mean, 7 years) following myeloablative conditioning. Patients were enrolled in France and England and treated between December 2010 and January 2014. Follow-up of patients in this intermediate analysis ranged from 9 to 42 months. INTERVENTION A single infusion of gene-modified CD34+ cells with an advanced lentiviral vector. MAIN OUTCOMES AND MEASURES Primary outcomes were improvement at 24 months in eczema, frequency and severity of infections, bleeding tendency, and autoimmunity and reduction in disease-related days of hospitalization. Secondary outcomes were improvement in immunological and hematological characteristics and evidence of safety through vector integration analysis. RESULTS Six of the 7 patients were alive at the time of last follow-up (mean and median follow-up, 28 months and 27 months, respectively) and showed sustained clinical benefit. One patient died 7 months after treatment of preexisting drug-resistant herpes virus infection. Eczema and susceptibility to infections resolved in all 6 patients. Autoimmunity improved in 5 of 5 patients. No severe bleeding episodes were recorded after treatment, and at last follow-up, all 6 surviving patients were free of blood product support and thrombopoietic agonists. Hospitalization days were reduced from a median of 25 days during the 2 years before treatment to a median of 0 days during the 2 years after treatment. All 6 surviving patients exhibited high-level, stable engraftment of functionally corrected lymphoid cells. The degree of myeloid cell engraftment and of platelet reconstitution correlated with the dose of gene-corrected cells administered. No evidence of vector-related toxicity was observed clinically or by molecular analysis. CONCLUSIONS AND RELEVANCE This study demonstrated the feasibility of the use of gene therapy in patients with Wiskott-Aldrich syndrome. Controlled trials with larger numbers of patients are necessary to assess long-term outcomes and safety.

T-cell repertoires in healthy and diseased human tissues analysed by T-cell receptor β-chain CDR3 size determination: evidence for oligoclonal expansions in tumours and inflammatory diseases

Many examples of oligoclonal T-cell expansion in infiltrated diseased tissues have been reported. However, it remains to be established whether such observations can be generalized and to what extent oligoclonal patterns obtained after in vitro culture of T-cell infiltrates reflect in vivo situations. Using new high resolution analysis which requires no in vitro cellular expansion, we detected such oligoclonal T-cell expansions in 7/7 melanoma tumour biopsies, 3/3 biopsies of inflammatory skin during acute graft versus host disease (aGVHD) after allogeneic bone marrow transplantation (alloBMT) and 7/7 synovial membranes from patients with rheumatoid arthritis. Thus, oligoclonal T-cell expansions are readily observed when a sufficiently sensitive detection method is used, suggesting that similar expansions are the rule among T-cell infiltrates in different diseases. This observation and the monitoring of the in vivo evolution of such expansion during the course of the disease and during in vitro culture should have important clinical implications.

Long-Term Remissions of Severe Pemphigus After Rituximab Therapy Are Associated with Prolonged Failure of Desmoglein B Cell Response

Changes in the B cell repertoire mediate long-lasting therapeutic effects of rituximab in pemphigus patients. A Blistering Attack on Autoimmunity The devastating effects of autoimmune diseases like type 1 diabetes and multiple sclerosis are front-page news. However, rare autoimmune diseases may be even more distressing in their relative anonymity. One such condition is pemphigus, which is a severe blistering condition caused by autoantibodies to adhesion proteins in the skin and mucus. The B cell–depleting antibody rituximab has been shown to treat pemphigus short term in early clinical trials. Now, Colliou et al. find that rituximab therapy can help pemphigus patients even after 6 years, in part by reshaping the B cell repertoire during reconstitution. The authors followed pemphigus patients from their early trial out at least 6 years after rituximab therapy. They found that nearly two-thirds of patients achieved a long-term complete response—either completely off of therapy or when treated with low levels of supplementary prednisone. They then compared patients with complete response to those with incomplete response to look at differences in reconstitution of the B cell compartment. Patients with complete response had a greater proportion of naïve and transitional B cells than those with incomplete response, which suggests a barrier to B cell maturation. Indeed, many of these transitional B cells secreted the regulatory cytokine interleukin-10. Moreover, complete responders had a specific loss of anti–desmoglein-specific B cells, which are pathogenic in pemphigus patients, but not B cells that respond to infectious agents. Together, these data suggest that B cell repertoire is reshaped after rituximab therapy, allowing for long-term effects in addition to the short-term loss of pathogenic B cells. If these observations are confirmed in large studies, these data could form the basis for a new frontline therapy for recalcitrant pemphigus. Pemphigus is a severe blistering condition of the skin and mucosa caused by autoantibodies directed against desmogleins, which are a type of keratinocyte adhesion protein. B cell depletion by rituximab has short-term efficacy against pemphigus. We aimed to assess the long-term course of pemphigus patients after B cell depletion and to understand the immunological mechanisms that mediate long-lasting remissions. We evaluated the clinical course of 22 pemphigus patients treated with rituximab after a 79-month median follow-up and compared the anti-desmoglein B cell response and B and T lymphocyte subpopulations and repertoire between patients who achieved complete remission (CR) and those who had incomplete remission (IR). Thirteen patients (59%) experienced CR during the study, including 10 patients off treatment and 3 patients with prednisone doses <10 mg/day; 9 patients had IR. A marked increase was observed in the ratio of CD19+CD27− naïve B cells to CD19+CD27+ memory B cells. Indeed, patients in CR had a fourfold higher number of transitional B cells and interleukin-10–secreting regulatory B cells than those in IR. Furthermore, CR was associated with modification of the initial B cell repertoire and the disappearance of desmoglein-specific circulating immunoglobulin G–positive (IgG+) B lymphocytes, whereas a skewed B cell repertoire was observed in patients in IR. Thus, a blockage of B cell maturation, a prolonged repopulation with naïve B cells, and a delayed reappearance of memory B cells, which resulted in the disappearance of circulating desmoglein-specific IgG+ B lymphocytes, contribute to the long-lasting effectiveness of rituximab for treating pemphigus.

Adoptive Transfer of Tumor-Reactive Melan-A-Specific CTL Clones in Melanoma Patients Is Followed by Increased Frequencies of Additional Melan-A-Specific T Cells

In this study, we report the adoptive transfer of highly tumor-reactive Melan-A-specific T cell clones to patients with metastatic melanoma, and the follow-up of these injected cells. These clones were generated from HLA-A*0201 patients by in vitro stimulations of total PBMC with the HLA-A*0201-binding Melan-A peptide analog ELAGIGILTV. Ten stage IV melanoma patients were treated by infusion of these CTL clones with IL-2 and IFN-α. The generated T cell clones, of effector/memory phenotype were selected on the basis of their ability to produce IL-2 in response to HLA-A*0201 Melan-A-positive melanoma lines. Infused clones were detected, by quantitative PCR, in the blood of three patients for periods ranging from 7 to 60 days. Six patients showed regression of individual metastases or disease stabilization, and one patient experienced a complete response, but no correlation was found between the detection of the infused clones in PBMC or tumor samples and clinical responses. Nonetheless, frequencies of Melan-A/A2-specific lymphocytes, measured by tetramer labeling, increased after treatment in most patients. In one of these patients, who showed a complete response, this increase corresponded to the expansion of new clonotypes of higher avidity than those detected before treatment. Together, our results suggest that infused CTL clones may have initiated an antitumor response that may have resulted in the expansion of a Melan-A-specific CTL repertoire.