Flt3 ligand expands lymphoid progenitors prior to recovery of thymopoiesis and accelerates T cell reconstitution after bone marrow transplantation

Deficient thymopoiesis and retarded recovery of newly developed CD4(+) T cells is one of the most important determinants of impaired immunocompetence after hemopoietic stem cell transplantation. Here we evaluated whether Fms-like tyrosine kinase 3 (Flt3) ligand (FL) alone or combined with IL-7 affects T cell recovery, thymopoiesis, and lymphoid progenitor expansion following bone marrow transplantation in immunodeficient mice. FL strongly accelerated and enhanced the recovery of peripheral T cells after transplantation of a low number of bone marrow cells. An additive effect on T cell recovery was not observed after coadministration of IL-7. Lineage(-)sca-1(+)c-kit(+)flt3(+) lymphoid progenitor cell numbers were significantly increased in bone marrow of FL-treated mice before recovery of thymopoiesis. Thymocyte differentiation was advanced to more mature stages after FL treatment. Improved T cell recovery resulted in better immunocompetence against a post-bone marrow transplantation murine CMV infection. Collectively, our data suggest that FL promotes T cell recovery by enhanced thymopoiesis and by expansion of lymphoid progenitors.     

Clinical aspects of cytomegalovirus infection after allogenic bone marrow grafts

CMV infection is one of the major infection after bone marrow transplantation. CMV viremia was systematically studied in 66 patients with aplastic anemia or leukemia undergoing BMT. 57% patients had CMV viremia with a frequency peak between 7 and 9 weeks after transplant. Clinical symptoms found during viremia were pancytopenia, fever, cytolytic hepatitis. Interstitial pneumonitis was found only in 4 cases. In 3 cases, viremia was not associated with clinical symptoms. Survival was identical to the group of patients without viremia. Viremia was positively associated with the presence of high anti-CMV antibody titer in donor or recipient before transplant, or to a lymphocyte proliferative response against CMV antigens in donor or recipient before BMT. Granulocyte transfusions increased the frequency of CMV viremia. CMV infection was significantly associated with acute and chronic graft versus host disease. The relation showed between these parameters and viremia provides a basis for an accurate diagnosis of CMV infection and a better background for the study of prophylactic or curative treatment of CMV infection.     

Immunity related to cytomegalovirus after allogenic bone marrow transplantation: role of donor immunity to cytomegalovirus in the incidence of cytomegalovirus infection in recipients

Cytomegalovirus infections are severe and frequent after BMT. This study included 34 bone marrow transplant recipients (23 aplastic anaemias and 11 leukaemias), their marrow donors and 125 related or non related normal controls. Assays were performed before transplantation and every 30 days between D 0 and D 90, and then every six months. They included detection of CMV induced lymphocyte proliferation in vitro, CMV antibody determinations by complement fixation and reverse haemagglutination, viraemia and/or viruria. Similarly, cellular immunity to mitogens and to other specific antigens was evaluated. During the period of study, 22 patients developed CMV infection. The diagnostic was confirmed by virus isolation from the 12th to the 96th day after the graft. Development of positive CMV proliferation test occurred from the 9th to the 84th day after virus isolation (30 to 120th day after the graft). In one case, the CMV infection was only proved by the lymphocyte proliferation to CMV in vitro and only 60 days later by viruria and 105 days later by detection of CMV antibodies. For the other 12 patients (7 aplasies and 5 leukaemias) and 10 of their bone marrow donors, no CMV infection was proved, before or after transplant, by any of the assays performed. By selecting a donor without previous CMV infection, we hope to reduce the incidence of CM infection in recipients.     

B cell development and regulation after T cell-depleted marrow transplantation

Antibody secreting B lymphocytes from immunized donors can be adoptively transferred after T cell-depleted marrow transplantation to produce protective levels of antibody in the recipient. We have investigated whether these transferred lymphocytes remain subject to continued clonal selection and subsequently became memory B cells even in the initial absence of T cells. Twenty-eight donor/recipient pairs were randomized pretransplant to be immunized or not with tetanus toxoid (TT). The recipients were then vaccinated with TT at 3, 6, and 12 mo posttransplant, and the anti-TT antibody response (IgG and IgM) was measured. Only when both donor and recipient were immunized pretransplant could the recipient respond to antigen challenge within the first year posttransplant. Examination of the spectrotype pattern of the recipient anti-TT antibody shows that selection of B cell clones continues, so that T cell depletion does not prevent the appearance of oligoclonal antibody responses. However, because the spectrotype pattern of the recipient did not match the donors, B cell regulatory mechanisms in donor and recipient are nonidentical. These data contrast with observations made in recipients of non-T cell-depleted marrow and serve to illustrate the role of T lymphocytes in the induction and regulation of secondary antibody responses in man. The results also suggest that optimal humoral responses to any antigen after T cell depletion can only occur when both donor and recipient are immunized pretransplant, a prediction borne out by studies on the influence of donor cytomegalovirus status on the severity of cytomegalovirus infection in the recipient.     

Immunoreconstitution after human bone marrow transplantation

Immunologic reconstitution was studied in 24 patients who underwent bone marrow transplantation, 17 allogenic and 7 autologous. The GVHD prophylaxis consisted of methotrexate and prednisone. The complete immune evaluation was to be carried out prior to transplantation at 1, 2, 3, 6, 9, 12 months after BMT and subsequently every 6 months up to 4 years. The investigated immunological parameters included total lymphocyte count, B-lymphocytes, T3-, T4-, T8-lymphocytes, T4/T8 ratio, natural killer cell activity, ADCC, lymphocyte blastogenic response and serum-IgG, -IgA, -IgM. Absolute lymphocyte count, B-lymphocytes, T3-lymphocytes recovered to normal levels after 6 months. T4-lymphocytes decreased significantly during the first 180 days posttransplant. T8-lymphocytes increased after 6 months to values higher than normal and the T4/T8 ratio decreased significantly and continued below 0.8 for 48 months. Patients without and with GVHD had low lymphocyte response to PHA and Con A for the first 6 months.     

Elimination of T lymphocytes from the bone marrow in HLA-incompatible bone marrow transplantation

The method presented is very well suited to eliminate T-lymphocytes from great amounts of bone-marrow. The stem cells required to reconstitute the bone-marrow are enriched in this way. It can be completely performed in a closed system. Any contamination with germs is excluded. It can be reproduced well and learnt quickly. It takes 10 hours for two trained co-workers to process 1,500 ml of bone-marrow. The vitality of cells is very good (100%). Its suitability for transplantation has still to be checked.     

Emergence of a CD4+CD28- granzyme B+, cytomegalovirus-specific T cell subset after recovery of primary cytomegalovirus infection

Cytotoxic CD4(+)CD28(-) T cells form a rare subset in human peripheral blood. The presence of CD4(+)CD28(-) cells has been associated with chronic viral infections, but how these particular cells are generated is unknown. In this study, we show that in primary CMV infections, CD4(+)CD28(-) T cells emerge just after cessation of the viral load, indicating that infection with CMV triggers the formation of CD4(+)CD28(-) T cells. In line with this, we found these cells only in CMV-infected persons. CD4(+)CD28(-) cells had an Ag-primed phenotype and expressed the cytolytic molecules granzyme B and perforin. Importantly, CD4(+)CD28(-) cells were to a large extent CMV-specific because proliferation was only induced by CMV-Ag, but not by recall Ags such as purified protein derivative or tetanus toxoid. CD4(+)CD28(-) cells only produced IFN-gamma after stimulation with CMV-Ag, whereas CD4(+)CD28(+) cells also produced IFN-gamma in response to varicella-zoster virus and purified protein derivative. Thus, CD4(+)CD28(-) T cells emerge as a consequence of CMV infection.     

Murine model of interstitial cytomegalovirus pneumonia in syngeneic bone marrow transplantation: persistence of protective pulmonary CD8-T-cell infiltrates after clearance of acute infection

Interstitial pneumonia (IP) is a severe organ manifestation of cytomegalovirus (CMV) disease in the immunocompromised host, in particular in recipients of bone marrow transplantation (BMT). Diagnostic criteria for the definition of CMV-IP include clinical evidence of pneumonia together with CMV detected in bronchoalveolar lavage or lung biopsy. We have used the model of syngeneic BMT and simultaneous infection of BALB/c mice with murine CMV for studying the pathogenesis of CMV-IP by controlled longitudinal analysis. A disseminated cytopathic infection of the lungs with fatal outcome was observed only when reconstituting CD8 T cells were depleted. Neither CD8 nor CD4 T cells mediated an immunopathogenesis of acute CMV-IP. By contrast, after efficient hematolymphopoietic reconstitution, viral replication in the lungs was moderate and focal. The histopathological picture was dominated by preferential infiltration of CD8 T cells confining viral replication to inflammatory foci. Notably, after clearance of acute infection, CD62L(lo) and CD62L(hi) subsets of CD44(+) memory CD8 T cells were found to persist in lung tissue. One can thus operationally distinguish an early CMV-positive IP (phase 1) and a late CMV-negative IP (phase 2). According to the definition, phase 2 histopathology would not be diagnosed as a CMV-IP and could instead be misinterpreted as a CMV-induced immunopathology. We document here that phase 1 as well as phase 2 pulmonary CD8 T cells are capable of exerting effector functions and are effectual in protecting against productive infection. We propose that antiviral "stand-by" memory-effector T cells persist in the lungs to prevent virus recurrence from latency.     

T and B cell responses to cytomegalovirus antigens in healthy blood donors and bone marrow transplant recipients

Abstract We measured the production of interferon-gamma (IFN-γ) from single T cells and the T cell proliferative response to different cytomegalovirus (CMV) antigens in healthy blood donors and bone marrow transplant recipients. The antigens consisted of a CMV nuclear antigen (CMV na) containing the pp65-kDa matrix protein and the immediate early antigens but lacking CMV glycoproteins, and an antigen comprising native CMV glycoproteins (CMV gp). We also measured the IgG antibodies to CMV na and CMV gp. The T cells reacted to CMV na in CMV seropositive blood donors both with the production of IFN-γ and with proliferation, while bone marrow transplant recipients had a deficient T cell response. After stimulation with CMV gp, no T cell response could be observed in CMV seropositive subjects. IgG antibodies to CMV na coexisted in plasma with similar levels of antibodies to CMV gp.     

Graves-Basedow disease after allogeneic bone marrow transplantation

One severe aplastic anaemia case who presented autoimmune thyroid disease after allogeneic bone marrow transplantation (alloBMT) is described. A 19 year old Polish girl developed Graves' hyperthyroidisms 19 months after allogeneic BMT for severe aplastic anaemia (SAA) donated from her brother. Her serum was positive for thyroid stimulating antibody (TSAb) and anti-thyroid peroxidase autoantibodies (aTPO) while her brother remained euthyroid, seronegative for TSAb, and showed no clinical signs of thyroid pathology. The genetic studies of lymphocytes FISH (fluorescence in situ hybridization) and analysis of STR (short tandem repeated) fragments suggested, that lymphocytes responsible for hyperthyroidisms were of donor origin.     

The kinetics of early T and B cell immune recovery after bone marrow transplantation in RAG-2-deficient SCID patients

The kinetics of T and B cell immune recovery after bone marrow transplantation (BMT) is affected by many pre- and post-transplant factors. Because of the profoundly depleted baseline T and B cell immunity in recombination activating gene 2 (RAG-2)-deficient severe combined immunodeficiency (SCID) patients, some of these factors are eliminated, and the immune recovery after BMT can then be clearly assessed. This process was followed in ten SCID patients in parallel to their associated transplant-related complications. Early peripheral presence of T and B cells was observed in 8 and 4 patients, respectively. The latter correlated with pre-transplant conditioning therapy. Cells from these patients carried mainly signal joint DNA episomes, indicative of newly derived B and T cells. They were present before the normalization of the T cell receptor (TCR) and the B cell receptor (BCR) repertoire. Early presentation of the ordered TCR gene rearrangements after BMT occurred simultaneously, but this pattern was heterogeneous over time, suggesting different and individual thymic recovery processes. Our findings early after transplant could suggest the long-term patients' clinical outcome. Early peripheral presence of newly produced B and T lymphocytes from their production and maturation sites after BMT suggests donor stem cell origin rather than peripheral expansion, and is indicative of successful outcome. Peripheral detection of TCR excision circles and kappa-deleting recombination excision circles in RAG-2-deficient SCID post-BMT are early markers of T and B cell reconstitution, and can be used to monitor outcome and tailor specific therapy for patients undergoing BMT.     

Allogeneic T cells treated with amotosalen prevent lethal cytomegalovirus disease without producing graft-versus-host disease following bone marrow transplantation

Infusion of donor antiviral T cells can provide protective immunity for recipients of hemopoietic progenitor cell transplants, but may cause graft-vs-host disease (GVHD). Current methods of separating antiviral T cells from the alloreactive T cells that produce GVHD are neither routine nor rapid. In a model of lethal murine CMV (MCMV) infection following MHC-mismatched bone marrow transplantation, infusion of MCMV-immune donor lymphocytes pretreated with the DNA cross-linking compound amotosalen prevented MCMV lethality without producing GVHD. Although 95% of mice receiving 30 x 10(6) pretreated donor lymphocytes survived beyond day +100 without MCMV disease or GVHD, all mice receiving equivalent numbers of untreated lymphocytes rapidly died of GVHD. In vitro, amotosalen blocked T cell proliferation without suppressing MCMV peptide-induced IFN-gamma production by MCMV-primed CD8(+) T cells. In vivo, pretreated lymphocytes reduced hepatic MCMV load by 4-log(10) and promoted full hemopoietic chimerism. Amotosalen-treated, MCMV tetramer-positive memory (CD44(high)) CD8(+) T cells persisted to day +100 following infusion, and expressed IFN-gamma when presented with viral peptide. Pretreated T cells were effective at preventing MCMV lethality over a wide range of concentrations. Thus, amotosalen treatment rapidly eliminates the GVHD activity of polyclonal T cells, while preserving long-term antiviral and graft facilitation effects, and may be clinically useful for routine adoptive immunotherapy.