Background e objetivo. A reconstituição celular hematopoiética com o transplante de células tronco hematopoiéticas (TCTH) alogênicas é um método de tratamento estabelecido para uma variedade de doenças hematológicas, oncológicas e imunológicas. Entretanto, TCTH está associado a considerável morbimortalidade devido a fatores como recidiva da doença de base, grau de compatibilidade HLA, tipo de regime de condicionamento e infecções durante o período de neutropenia. Este estudo investigou a associação entre o aloantígenoneutrofílico humano (HNA) e o dia de pega, a ocorrência de DECH aguda e TRM em pacientes que foram submetidos a transplante de células tronco hematopoiéticas alogênico. Tipo de estudo e local. Estudo de coorte prospectivo realizado no Hospital de Clínicas de Porto Alegre. Métodos. Avaliamos 27 pacientes transplantados entre maio de 2013 e abril de 2014 e seus respectivos doadores. A tipagem HNA foi realizada, nas amostras dos doadores, por PCR-SSP e os anticorpos anti-HNA foram detectados nos pacientes utilizando o kit LABSCREEN MULTI (LSMUTR – One Lambda). Resultados. A idade variou entre 1 a 63 anos, com uma média de 20,4 ± 17,5 anos. Dezenove pacientes eram pediátricos (<21 anos) com média de idade de 10,05 ± 6,4 anos e entre os pacientes adultos a média foi 42,2 ± 12,6 anos. Houve um discreto predomínio do sexo masculino 16 (59,3%). As leucemias agudas foram frequentes em 19 (70,4%) dos pacientes, outras doenças oncohematológicas malignas (Linfoma Hodgkin e Linfoma não Hodgkin) estiveram em 3 (11,1%) e as não malignas (síndrome mielodisplásica, osteopetrose, hemoglobinúria paroxicística noturna, aplasia e doença granulomatosa) estiveram em 6 (22,2%) dos casos. A maioria dos pacientes 19 (70,4%), apresentavam a doença há menos de 12 meses na época do transplante e 24 (88,9%) deles foram totalmente compatível com seus doadores quanto ao sistema HLA. O regime de condicionamento mieloablativo foi utilizado em 16 (59,2%) dos pacientes e a profilaxia padrão para DECH (ciclosporina e metotrexate) foi utilizada em 15 (55,5%) dos pacientes. O dia de pega teve uma mediana de 19 e mínimo e máximo de 15 e 30, respectivamente. Quatro pacientes (14,8%) tiveram óbito antes da pega. Aproximadamente 63% (17 pacientes) apresentaram DECH aguda (em todos os estágios) e a taxa de mortalidade (TRM) foi de aproximadamente 44% dos casos (12 pacientes). Os pacientes que receberam TCTH de um doador aparentado tiveram TRM de aproximadamente 41% (7 pacientes) e os que receberam de um doador não aparentado foi de aproximadamente 45% (5 pacientes). A frequência dos antígenos HNA detectados nos doadores foi de 46,4% HNA-1a, 89,3% HNA-1b, 3,6% HNA-1c, 96,4% HNA-3a, 32,1% HNA-3b, 96,4% HNA-4a, 21,4% HNA-4b, 85,7% HNA-5a e 71,4% HNA-5b. A frequência dos anticorpos anti-HNA1a, anti-HNA1b, anti-HNA1c e anti-HNA2 no D0 foram respectivamente 46,4%, 42,9%, 42,9% e 53,6%. A associação entre a tipagem HNA dos doadores e anticorpos anti-HNAdos receptores com dia da pega, DECH aguda e TRM não mostrou correlação estatisticamente significativa. Conclusão. A frequência de HNA encontradanos doadores está de acordo com o descrito pela literatura. Contudo, a frequência dos anticorpos anti-HNAs foi bastante alta na população do estudo, embora a maioria apresentasse doença há menos de 12 meses até o transplante. Apesar de não encontrarmos uma correlação, novos estudos são necessários para melhor avaliar o papel do HNA no desfecho do TCTH. / Background and purpose. Hematopoietic cellular reconstruction with allogeneic hematopoietic stem cell transplantation (HSCT) is an established method of treatment for a variety of hematological, oncologic and immunologic diseases. However, HSCT is associated with considerable morbidity and mortality due to recurrence of underlying disease, incomplete HLA compatibility, type of conditioning regimen and infection during the unavoidable period of neutropenia. This study investigates a surrogate cause of morbidity: compatibility of Human Neutrophil Antigens (HNA) between donors and receivers and its association with day of engraftment, incidence of acute graft versus host disease (GVHD) and total rate of mortality (TRM) in patients who underwent allogeneic HSCT. Type of study and location. Prospective cohort study carried out at the Hospital de Clínicas de Porto Alegre (HCPA), Brazil. Methods. We have studied 27 patients who underwent HSCT between May, 2013 and April, 2014, and their respective donors. HNA typing in the donors was performed by PCR-SSP (One Lambda) and anti-HNA antibodies in receivers were detected using the LABSCREEN MULTI kit (LSMUTR-One Lambda). Results. The age ranged from 1 to 63 years, with an average of 20.4 ± 17.5 years. Nineteen were pediatric patients (<21 years) with an average age of 10.05 ± 6.4 years, and among adult patients the average was 42.2 ± 12.6 years. There was a discreet male prevalence, 16 (59,3%). The acute leukemias were frequent in 19 (70,3%) of patients, other malignant onco-hematological diseases (Hodgkin Lymphoma and non-Hodgkin's Lymphoma) in 3 (11,1%) and non-malignant (myelodysplastic syndrome, osteopetrosis, paroxysmal nocturnal hemoglobinuria, aplasia and granulomatous disease) in 6 (22,2%). Nineteen (70,3%) of the patients, had the disease for less than 12 months at the time of the transplant and 24 (88,9%) were fully HLA compatible with their donors. Myeloablative conditioning regimen was used in 16 (59,3%) of the patients and the standard prophylaxis for GVHD (cyclosporine and methotrexate) was used in 15 (55,5%) of the patients. The day of engraftment had a median of 19 and minimum and maximum of 15 and 30, respectively. Four patients (14,8%) died before the engraftment. Approximately 17 patients (63%) showed acute GVHD (in all stages) and the total rate of mortality (TRM) was approximately 44% of the cases (12 patients). Patients who received HSCT from a related donor had TRM of approximately 41% (7 patients) and those who have received an unrelated donor was approximately 45% (5 patients). The frequency of HNA antigens detected in donors was 46,4% HNA-1a, 89,3% HNA-1b, 3,6% HNA-1c, 96,4% HNA-3a, 32,1% HNA-3b, 96,4% HNA-4a, 21,4% HNA-4b, 85,7% HNA-5a and 71,4% HNA-5b. The frequency of antibodies anti-HNA1a, anti-HNA1b, anti-HNA1c and anti-HNA2 at D0 were respectively 46,4%, 42,9%, 42,9% and 53,6%. The association between the HNA donor typing and anti-HNA antibodies of receivers with day of the engraftment, acute GVHD and TRM showed no statistically significant correlation. Conclusion. The HNA frequency found in our donors was close to the described in the literature. The frequency of anti-HNAs antibodies, however, was quite high in our study population; although the majority presented the disease for less than 12 months before the transplant. The association between HNA donor typing and anti-HNA antibodies of patients with day of engraftment, acute GVHD incidence and TRM showed no statistically significant correlation. As the number of cases was small, further studies with higher numbers and with antigen/antibodies assayed in both sides of transplantation pairs, are needed to better assess the role of the HNAs on the outcome of HSCT.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2014-09-25T17:34:38Z No. of bitstreams: 2 Dissertação_Lucianna G. N. Lemes.pdf: 2661301 bytes, checksum: c0238e41dfbe2adbd10e5ddcff7a139e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2014-09-26T11:31:18Z (GMT) No. of bitstreams: 2 Dissertação_Lucianna G. N. Lemes.pdf: 2661301 bytes, checksum: c0238e41dfbe2adbd10e5ddcff7a139e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-09-26T11:31:18Z (GMT). No. of bitstreams: 2 Dissertação_Lucianna G. N. Lemes.pdf: 2661301 bytes, checksum: c0238e41dfbe2adbd10e5ddcff7a139e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-12-20 / The calicivirus (norovirus and sapovirus) are important etiologic agents of acute gastroenteritis. Recent studies show that in immunocompromised patients such as those undergoing allogeneic hematopoietic stem cell transplantation (HSCT), norovirus infection can lead to worsening of symptoms and be confused with clinical symptoms of graft versus host disease (GVHD). However, calicivirus screening is not performed, routinely, as part of the patients’ follow-up laboratory exams. The main objective of this study was to evaluate the occurrence of norovirus (NoV) and sapovirus (SaV) in patients who underwent HSCT, and to conduct the molecular characterization of the samples positive for these viruses. Fecal samples were collected weekly, and serum samples were obtained every two weeks of ten patients who underwent HSCT, for a minimum period of five months and a maximum of one year. The secretor status was determined by an enzyme immunoassay and the detection of calicivirus was performed by RT-PCR using primers specific for a partial region of the gene encoding the NoV genogroup I and II (GI and GII) and SaV capsid protein. The genomic sequencing was performed for positive samples. The results showed that from ten patients participating in the study, eight had diarrhea. Among these, six (60%) had positive samples for NoV, and all of them had a secretor phenotype. The duration of NoV excretion in feces ranged from five to 143 days. Viral RNA was also detected in serum specimens, ranging from 29 to 36 days in the five patients infected with NoV. Three of the six patients had acute intestinal GVHD. Through genomic sequencing and phylogenetic analysis all NoV-positive samples were characterized as genotype GI.3, and because they had a high nucleotide identity, they were all characterized as a single haplotype. The data highlight the urgent need of the inclusion of calicivirus screening in the routine testing performed before transplantation and during follow-up of these patients. This is the first report of the occurrence of NoV in patients undergoing HSCT in Brazil. / Os calicivírus (norovírus e sapovírus) são importantes agentes etiológicos da gastroenterite aguda. Estudos recentes mostram que em pacientes imunocomprometidos, como os submetidos a transplante alogênico de células progenitoras hematopoiéticas (TACPH), a infecção por norovírus pode levar ao agravamento dos sintomas e ser confundida com quadro clínico da doença do enxerto contra o hospedeiro (DECH). Entretanto, a triagem para calicivírus não é realizada, rotineiramente, como parte dos exames laboratoriais de acompanhamento destes pacientes. O principal objetivo deste estudo foi avaliar a ocorrência de norovírus (NoV) e sapovírus (SaV) em pacientes que foram submetidos ao TACPH e proceder à caracterização molecular das amostras positivas para estes vírus. Foram obtidas amostras de fezes, coletadas semanalmente, e de soro, a cada quinze dias, de dez pacientes que realizaram o TACPH, por um período mínimo de cinco meses e máximo de um ano. O fenótipo secretor dos pacientes foi determinado utilizando um teste imunoenzimático e a pesquisa de calicivírus foi realizada pela RT-PCR, utilizando-se iniciadores específicos para uma região parcial do gene codificante para a proteína dos capsídeos dos NoV do genogrupo I e II (GI e GII) e dos SaV. Os amplicons das amostras positivas foram submetidos ao sequenciamento genômico e análise filogenética. Os resultados obtidos revelaram que de dez pacientes participantes do estudo, oito apresentaram diarreia e vômito. Dentre esses, seis (60%) apresentaram amostras positivas para NoV, sendo que todos foram identificados como secretores. O período de excreção de NoV nas fezes variou de cinco a 143 dias. Foi também detectado RNA viral nas amostras de soro, variando de 29 a 36 dias, em cinco pacientes infectados por NoV. Três, dos seis pacientes, apresentaram DECH aguda intestinal. Através do sequenciamento genômico e análise filogenética, todas as amostras positivas para NoV, de todos os pacientes, foram caracterizadas como genótipo GI.3 dos NoV, e como foi comprovada elevada identidade nucleotídica entre elas, foram caracterizadas como um único haplótipo. Os dados obtidos ressaltam a urgente necessidade da inclusão da pesquisa de calicivírus na rotina de exames realizados antes do transplante, bem como durante o acompanhamento destes pacientes. Este é o primeiro relato da ocorrência de NoV em pacientes submetidos ao TACPH no Brasil.

Survival of patients with poor prognosis or relapsed haematopoietic malignancies can be markedly improved by allogeneic haematopoietic stem cell transplantation (HSCT). HSCT reconstitutes the immune and haematopoietic systems after myeloablative conditioning and inhibits the recurrence of the malignancy by a graft-versus-leukaemia (GVL) response mediated by donor T cells. However, significant post-transplant complications such as graft-versus-host disease (GVHD) continue to plague the event-free survival of this curative procedure. GVHD is facilitated by donor T cells that recognise histocompatibility antigens on host antigen presenting cells (APC), such as dendritic cells (DC). Current treatment options for GVHD are focused on these T cells. However, these treatments result in an increased incidence of infection, graft rejection and relapse. A novel means of immunosuppression in GVHD is the use of multi-potent, mesenchymal stromal cells (MSC). MSC are non-immunogenic cells that actively suppress T cell function in vitro, and can resolve steroid-refractory GVHD in the clinic. Despite their use in the clinic, there is a paucity of pre-clinical data. Our aim was to investigate the in vivo efficacy of MSC to control GVHD while maintaining the beneficial GVL effect, and to begin to understand the mechanism by which MSC exert their immunosuppressive effects. We isolated and characterised MSC from murine bone/bone marrow and demonstrated that they suppressed T cell proliferation in vitro, even at low ratios of 1 MSC per 100 T cells. This was true of both donor-derived MSC, and MSC derived from unrelated donors (third party). Importantly, we observed that MSC significantly reduced T cell production of the pro-inflammatory cytokines TNFα and IFNγ in culture supernatants and that IFNγ plays a key role in the ability of MSC to suppress T cell proliferation. In vivo, we examined the effects of donor-derived MSC on GVHD severity and onset in two myeloablative murine models of HSCT. A major histocompatibility complex (MHC)-mismatched donor-recipient pair combination was used as a proof–of-principle model [UBI-GFP/BL6 (H-2b)àBALB/c (H-2d)], and an MHC-matched, minor histocompatibility antigen (miHA) mismatched donor-recipient pair combination was used to mimic MHC-matched sibling transplantation [UBI-GFP/BL6 (H-2b)àBALB.B (H-2b)]. We examined a number of variables related to MSC infusion including timing, dose and route of injection. We found that early post transplant infusion of MSC by the intraperitoneal injection was most effective at delaying death from GVHD, compared to pre-transplant infusion or intravenous injection. Furthermore, we found that the dose of MSC was critical, as infusion of too few MSC was ineffective and infusion of too many MSC exacerbated the development of GVHD. Taken together, these results suggest that timing, dose and route of injection are all important factors to be considered to ensure successful therapeutic outcome. To investigate the in vivo mechanism of action, we conducted timed sacrifice experiments in the MHC-mismatched model to determine if MSC altered cytokine secretion and cellular effectors, such as DC, known to play a key role in GVHD. Despite the fact that MSC given post-HSCT enter an environment full of activated DC and IFNγ levels, by day 3 and 6 post infusion, these activated DC and IFNγ levels are decreased compared to controls or mice infused with MSC pre-transplant (p<0.05). This confirmed our in vitro data that IFNγ played an important role in MSC-mediated immunosuppression. In addition, when we removed a major source of IFNγ production in vivo by administering the T cell depleting antibody KT3 to mice with or without MSC, we found that although T cell depletion prolonged survival, MSC were unable to further enhance this effect. This was also true when MSC were used in combination with the conventional immunosuppressant cyclosporine. Finally, we examined whether the infusion of MSC would compromise the GVL effect. We found that whilst MSC could delay the onset of GVHD, in our model they did not alter the anti-tumour effects of the donor T cells. Overall, we have shown that MSC can delay but not prevent death from GVHD when administered at an appropriate time and dose and that IFNγ is required for MSC-mediated immunosuppression in our model. These data suggest that patients undergoing HSCT should be monitored for IFNγ, and administered MSC when high levels are reached. Whilst MSC may be a promising therapy for patients with severe GVHD, we highlight that further investigation is warranted before MSC are accepted for widespread use in the clinic. The risks and benefits for transplant recipients should be carefully considered before utilising MSC to treat or prevent GVHD.

The Fas pathway is critical for the maintenance of normal T cell homeostasis. Humans and mice with defects in this pathway exhibit the accumulation of large numbers of peripheral lymphocytes and lupus-like autoimmunity. A major feature of these organisms is the accumulation of non-NK TCRαβ+CD4-CD8- “double negative” (DN) T cells. While regulatory T cells (Tregs) with the DN phenotype have been extensively characterized in Fas-sufficient mice and humans, limited data exist on the role of DN T cells as Tregs in Fas-deficient animals. In fact, most of the literature suggests that the DN T cells accumulating in Fas-deficiency states are pathogenic, contributing to secondary lymph node enlargement and autoimmune disease. In this body of work, data are presented that illustrate that Fas-deficient lymphoproliferative (LPR) DN T cells can act as Tregs in an interferon γ (IFNγ)- and Fas ligand (FasL)-dependent fashion toward Fas-sufficient T cells. LPR DN T cells needed to be able to secrete and respond to IFNγ in order to upregulate surface FasL, in order to ameliorate GVHD mediated by CD4+ T cells in vivo and to suppress the proliferation of and kill activated CD4+ T cells in vitro. FcRγ, a key molecule involved in innate immune responses, can substitute for CD3ζ in the T cell receptor (TCR) of mouse and human T cells in certain circumstances; in doing so, it is essential for the regulatory function of TCR transgenic DN Tregs. FcRγ-deficient LPR mice were found to have exacerbated T cell accumulation and early mortality. We show that while FcRγ expression was required for LPR DN T cells to regulate CD4+ and CD8+ T cells responding to alloantigens in vitro and in vivo, it does not control autologous lymphoproliferation in LPR mice by supporting the function of a regulatory cell, nor does it affect the rate of proliferation of LPR T cells in vivo. Instead, FcRγ-expressing LPR CD4+, CD8+ and DN T cells were found to be undergoing apoptosis at a high rate in vivo, and in contrast to their FcRγ-deficient counterparts, FcRγ+ LPR DN T cells were capable of undergoing TCR restimulation-induced cell death (RICD). The data presented in this thesis therefore show that LPR DN T cells can exhibit IFNγ-, FasL- and FcRγ-dependent regulatory function, and also illustrate a previously unknown function for FcRγ in controlling the expansion of Fas-deficient T cells. The implications of these data for autoimmune lymphoproliferative syndromes, and normal T cell homeostasis, are discussed.

CD28 co-stimulation is required for the generation of naturally occurring regulatory T cells (nTregs) in the thymus through Lck-signaling. However, high level of CD28 suppresses the generation of induced Tregs (iTregs) from naïve CD4 T cells, although underlying mechanism(s) has not been defined. Here we investigated the role of CD28-mediated signaling pathways in the suppression of Treg generation. We used a series of transgenic (Tg) mice on CD28-deficient background that bears WT CD28 or mutated CD28 in its cytosolic tail incapable of binding to Lck, PI3K or Itk. Regardless of exogenous IL-2, strong CD28 costimulation suppressed iTreg generation through Lck signaling. Using a GVHD model to test the role of CD28-mediated iTreg suppression in T cell pathogenicity in vivo, we found that CD28-Lck T cells induced significantly less GVHD than T cells from CD28-WT mice. Furthermore, we found that the recipients of T cells from CD28-Lck mice generated significantly more iTregs than those with T cells from CD28-WT, which contribute to reduced graft-versus-host disease (GVHD) development in recipients of CD28-Lck T cells. These results indicate that CD28 costimulation can negatively regulate Treg generation and may provide an avenue for control of T-cell immunity or tolerance by regulating Tregs using the CD28 signal as a target. We went a step forward and investigated the therapeutic potential of antigen-specific iTregs in the prevention of GVHD. Donor hematopoietic stem cells and mature T cells are transplanted into a lymphopenic host to potentially cure many cancers and hematopoietic diseases like leukemia in bone marrow transplantation (BMT) or hematopoietic stem cell transplantation (HCT), but the frequent development of GVHD is the main drawback of this treatment. nTregs suppress the development of GVHD and may spare graft-versus-tumor effect. However, nTregs are a minor (~5%) subpopulation of CD4 helper T cells in healthy individuals, and using in vitro expanded nTregs is a common strategy to test their therapeutic potential in BMT. The concern of in vitro expanded nTregs may include their stability of Foxp3 (master regulatory gene for the development and function of regulatory T cell) expression and suppressive function, survival in vivo, and the non-selective suppression of the pre-activated nTregs. Antigen-specific activation of the regulatory T cells is important for optimal function. In this study, we used an alternative strategy to generate antigen-specific, iTregs and assessed their suppressive potential by comparing their effectiveness in preventing GVHD with polyclonal iTregs. We found that antigen-specific iTregs prevented GVHD lethality in recipients that expressed the target antigen, but were not protective of recipients who did not express the target antigen. Furthermore, antigen-specific iTregs were significantly more efficient than those polyclonal Tregs in the prevention of GVHD. These results reveal the therapeutic potential of antigen-specific iTregs to prevent GVHD efficiently and selectively, and provide the rationale to use antigen-specific iTregs in clinical HCT.

The Fas pathway is critical for the maintenance of normal T cell homeostasis. Humans and mice with defects in this pathway exhibit the accumulation of large numbers of peripheral lymphocytes and lupus-like autoimmunity. A major feature of these organisms is the accumulation of non-NK TCRαβ+CD4-CD8- “double negative” (DN) T cells. While regulatory T cells (Tregs) with the DN phenotype have been extensively characterized in Fas-sufficient mice and humans, limited data exist on the role of DN T cells as Tregs in Fas-deficient animals. In fact, most of the literature suggests that the DN T cells accumulating in Fas-deficiency states are pathogenic, contributing to secondary lymph node enlargement and autoimmune disease. In this body of work, data are presented that illustrate that Fas-deficient lymphoproliferative (LPR) DN T cells can act as Tregs in an interferon γ (IFNγ)- and Fas ligand (FasL)-dependent fashion toward Fas-sufficient T cells. LPR DN T cells needed to be able to secrete and respond to IFNγ in order to upregulate surface FasL, in order to ameliorate GVHD mediated by CD4+ T cells in vivo and to suppress the proliferation of and kill activated CD4+ T cells in vitro. FcRγ, a key molecule involved in innate immune responses, can substitute for CD3ζ in the T cell receptor (TCR) of mouse and human T cells in certain circumstances; in doing so, it is essential for the regulatory function of TCR transgenic DN Tregs. FcRγ-deficient LPR mice were found to have exacerbated T cell accumulation and early mortality. We show that while FcRγ expression was required for LPR DN T cells to regulate CD4+ and CD8+ T cells responding to alloantigens in vitro and in vivo, it does not control autologous lymphoproliferation in LPR mice by supporting the function of a regulatory cell, nor does it affect the rate of proliferation of LPR T cells in vivo. Instead, FcRγ-expressing LPR CD4+, CD8+ and DN T cells were found to be undergoing apoptosis at a high rate in vivo, and in contrast to their FcRγ-deficient counterparts, FcRγ+ LPR DN T cells were capable of undergoing TCR restimulation-induced cell death (RICD). The data presented in this thesis therefore show that LPR DN T cells can exhibit IFNγ-, FasL- and FcRγ-dependent regulatory function, and also illustrate a previously unknown function for FcRγ in controlling the expansion of Fas-deficient T cells. The implications of these data for autoimmune lymphoproliferative syndromes, and normal T cell homeostasis, are discussed.

Survival of patients with poor prognosis or relapsed haematopoietic malignancies can be markedly improved by allogeneic haematopoietic stem cell transplantation (HSCT). HSCT reconstitutes the immune and haematopoietic systems after myeloablative conditioning and inhibits the recurrence of the malignancy by a graft-versus-leukaemia (GVL) response mediated by donor T cells. However, significant post-transplant complications such as graft-versus-host disease (GVHD) continue to plague the event-free survival of this curative procedure. GVHD is facilitated by donor T cells that recognise histocompatibility antigens on host antigen presenting cells (APC), such as dendritic cells (DC). Current treatment options for GVHD are focused on these T cells. However, these treatments result in an increased incidence of infection, graft rejection and relapse. A novel means of immunosuppression in GVHD is the use of multi-potent, mesenchymal stromal cells (MSC). MSC are non-immunogenic cells that actively suppress T cell function in vitro, and can resolve steroid-refractory GVHD in the clinic. Despite their use in the clinic, there is a paucity of pre-clinical data. Our aim was to investigate the in vivo efficacy of MSC to control GVHD while maintaining the beneficial GVL effect, and to begin to understand the mechanism by which MSC exert their immunosuppressive effects. We isolated and characterised MSC from murine bone/bone marrow and demonstrated that they suppressed T cell proliferation in vitro, even at low ratios of 1 MSC per 100 T cells. This was true of both donor-derived MSC, and MSC derived from unrelated donors (third party). Importantly, we observed that MSC significantly reduced T cell production of the pro-inflammatory cytokines TNFα and IFNγ in culture supernatants and that IFNγ plays a key role in the ability of MSC to suppress T cell proliferation. In vivo, we examined the effects of donor-derived MSC on GVHD severity and onset in two myeloablative murine models of HSCT. A major histocompatibility complex (MHC)-mismatched donor-recipient pair combination was used as a proof–of-principle model [UBI-GFP/BL6 (H-2b)àBALB/c (H-2d)], and an MHC-matched, minor histocompatibility antigen (miHA) mismatched donor-recipient pair combination was used to mimic MHC-matched sibling transplantation [UBI-GFP/BL6 (H-2b)àBALB.B (H-2b)]. We examined a number of variables related to MSC infusion including timing, dose and route of injection. We found that early post transplant infusion of MSC by the intraperitoneal injection was most effective at delaying death from GVHD, compared to pre-transplant infusion or intravenous injection. Furthermore, we found that the dose of MSC was critical, as infusion of too few MSC was ineffective and infusion of too many MSC exacerbated the development of GVHD. Taken together, these results suggest that timing, dose and route of injection are all important factors to be considered to ensure successful therapeutic outcome. To investigate the in vivo mechanism of action, we conducted timed sacrifice experiments in the MHC-mismatched model to determine if MSC altered cytokine secretion and cellular effectors, such as DC, known to play a key role in GVHD. Despite the fact that MSC given post-HSCT enter an environment full of activated DC and IFNγ levels, by day 3 and 6 post infusion, these activated DC and IFNγ levels are decreased compared to controls or mice infused with MSC pre-transplant (p<0.05). This confirmed our in vitro data that IFNγ played an important role in MSC-mediated immunosuppression. In addition, when we removed a major source of IFNγ production in vivo by administering the T cell depleting antibody KT3 to mice with or without MSC, we found that although T cell depletion prolonged survival, MSC were unable to further enhance this effect. This was also true when MSC were used in combination with the conventional immunosuppressant cyclosporine. Finally, we examined whether the infusion of MSC would compromise the GVL effect. We found that whilst MSC could delay the onset of GVHD, in our model they did not alter the anti-tumour effects of the donor T cells. Overall, we have shown that MSC can delay but not prevent death from GVHD when administered at an appropriate time and dose and that IFNγ is required for MSC-mediated immunosuppression in our model. These data suggest that patients undergoing HSCT should be monitored for IFNγ, and administered MSC when high levels are reached. Whilst MSC may be a promising therapy for patients with severe GVHD, we highlight that further investigation is warranted before MSC are accepted for widespread use in the clinic. The risks and benefits for transplant recipients should be carefully considered before utilising MSC to treat or prevent GVHD.

Survival of patients with poor prognosis or relapsed haematopoietic malignancies can be markedly improved by allogeneic haematopoietic stem cell transplantation (HSCT). HSCT reconstitutes the immune and haematopoietic systems after myeloablative conditioning and inhibits the recurrence of the malignancy by a graft-versus-leukaemia (GVL) response mediated by donor T cells. However, significant post-transplant complications such as graft-versus-host disease (GVHD) continue to plague the event-free survival of this curative procedure. GVHD is facilitated by donor T cells that recognise histocompatibility antigens on host antigen presenting cells (APC), such as dendritic cells (DC). Current treatment options for GVHD are focused on these T cells. However, these treatments result in an increased incidence of infection, graft rejection and relapse. A novel means of immunosuppression in GVHD is the use of multi-potent, mesenchymal stromal cells (MSC). MSC are non-immunogenic cells that actively suppress T cell function in vitro, and can resolve steroid-refractory GVHD in the clinic. Despite their use in the clinic, there is a paucity of pre-clinical data. Our aim was to investigate the in vivo efficacy of MSC to control GVHD while maintaining the beneficial GVL effect, and to begin to understand the mechanism by which MSC exert their immunosuppressive effects. We isolated and characterised MSC from murine bone/bone marrow and demonstrated that they suppressed T cell proliferation in vitro, even at low ratios of 1 MSC per 100 T cells. This was true of both donor-derived MSC, and MSC derived from unrelated donors (third party). Importantly, we observed that MSC significantly reduced T cell production of the pro-inflammatory cytokines TNFα and IFNγ in culture supernatants and that IFNγ plays a key role in the ability of MSC to suppress T cell proliferation. In vivo, we examined the effects of donor-derived MSC on GVHD severity and onset in two myeloablative murine models of HSCT. A major histocompatibility complex (MHC)-mismatched donor-recipient pair combination was used as a proof–of-principle model [UBI-GFP/BL6 (H-2b)àBALB/c (H-2d)], and an MHC-matched, minor histocompatibility antigen (miHA) mismatched donor-recipient pair combination was used to mimic MHC-matched sibling transplantation [UBI-GFP/BL6 (H-2b)àBALB.B (H-2b)]. We examined a number of variables related to MSC infusion including timing, dose and route of injection. We found that early post transplant infusion of MSC by the intraperitoneal injection was most effective at delaying death from GVHD, compared to pre-transplant infusion or intravenous injection. Furthermore, we found that the dose of MSC was critical, as infusion of too few MSC was ineffective and infusion of too many MSC exacerbated the development of GVHD. Taken together, these results suggest that timing, dose and route of injection are all important factors to be considered to ensure successful therapeutic outcome. To investigate the in vivo mechanism of action, we conducted timed sacrifice experiments in the MHC-mismatched model to determine if MSC altered cytokine secretion and cellular effectors, such as DC, known to play a key role in GVHD. Despite the fact that MSC given post-HSCT enter an environment full of activated DC and IFNγ levels, by day 3 and 6 post infusion, these activated DC and IFNγ levels are decreased compared to controls or mice infused with MSC pre-transplant (p<0.05). This confirmed our in vitro data that IFNγ played an important role in MSC-mediated immunosuppression. In addition, when we removed a major source of IFNγ production in vivo by administering the T cell depleting antibody KT3 to mice with or without MSC, we found that although T cell depletion prolonged survival, MSC were unable to further enhance this effect. This was also true when MSC were used in combination with the conventional immunosuppressant cyclosporine. Finally, we examined whether the infusion of MSC would compromise the GVL effect. We found that whilst MSC could delay the onset of GVHD, in our model they did not alter the anti-tumour effects of the donor T cells. Overall, we have shown that MSC can delay but not prevent death from GVHD when administered at an appropriate time and dose and that IFNγ is required for MSC-mediated immunosuppression in our model. These data suggest that patients undergoing HSCT should be monitored for IFNγ, and administered MSC when high levels are reached. Whilst MSC may be a promising therapy for patients with severe GVHD, we highlight that further investigation is warranted before MSC are accepted for widespread use in the clinic. The risks and benefits for transplant recipients should be carefully considered before utilising MSC to treat or prevent GVHD.

Survival of patients with poor prognosis or relapsed haematopoietic malignancies can be markedly improved by allogeneic haematopoietic stem cell transplantation (HSCT). HSCT reconstitutes the immune and haematopoietic systems after myeloablative conditioning and inhibits the recurrence of the malignancy by a graft-versus-leukaemia (GVL) response mediated by donor T cells. However, significant post-transplant complications such as graft-versus-host disease (GVHD) continue to plague the event-free survival of this curative procedure. GVHD is facilitated by donor T cells that recognise histocompatibility antigens on host antigen presenting cells (APC), such as dendritic cells (DC). Current treatment options for GVHD are focused on these T cells. However, these treatments result in an increased incidence of infection, graft rejection and relapse. A novel means of immunosuppression in GVHD is the use of multi-potent, mesenchymal stromal cells (MSC). MSC are non-immunogenic cells that actively suppress T cell function in vitro, and can resolve steroid-refractory GVHD in the clinic. Despite their use in the clinic, there is a paucity of pre-clinical data. Our aim was to investigate the in vivo efficacy of MSC to control GVHD while maintaining the beneficial GVL effect, and to begin to understand the mechanism by which MSC exert their immunosuppressive effects. We isolated and characterised MSC from murine bone/bone marrow and demonstrated that they suppressed T cell proliferation in vitro, even at low ratios of 1 MSC per 100 T cells. This was true of both donor-derived MSC, and MSC derived from unrelated donors (third party). Importantly, we observed that MSC significantly reduced T cell production of the pro-inflammatory cytokines TNFα and IFNγ in culture supernatants and that IFNγ plays a key role in the ability of MSC to suppress T cell proliferation. In vivo, we examined the effects of donor-derived MSC on GVHD severity and onset in two myeloablative murine models of HSCT. A major histocompatibility complex (MHC)-mismatched donor-recipient pair combination was used as a proof–of-principle model [UBI-GFP/BL6 (H-2b)àBALB/c (H-2d)], and an MHC-matched, minor histocompatibility antigen (miHA) mismatched donor-recipient pair combination was used to mimic MHC-matched sibling transplantation [UBI-GFP/BL6 (H-2b)àBALB.B (H-2b)]. We examined a number of variables related to MSC infusion including timing, dose and route of injection. We found that early post transplant infusion of MSC by the intraperitoneal injection was most effective at delaying death from GVHD, compared to pre-transplant infusion or intravenous injection. Furthermore, we found that the dose of MSC was critical, as infusion of too few MSC was ineffective and infusion of too many MSC exacerbated the development of GVHD. Taken together, these results suggest that timing, dose and route of injection are all important factors to be considered to ensure successful therapeutic outcome. To investigate the in vivo mechanism of action, we conducted timed sacrifice experiments in the MHC-mismatched model to determine if MSC altered cytokine secretion and cellular effectors, such as DC, known to play a key role in GVHD. Despite the fact that MSC given post-HSCT enter an environment full of activated DC and IFNγ levels, by day 3 and 6 post infusion, these activated DC and IFNγ levels are decreased compared to controls or mice infused with MSC pre-transplant (p<0.05). This confirmed our in vitro data that IFNγ played an important role in MSC-mediated immunosuppression. In addition, when we removed a major source of IFNγ production in vivo by administering the T cell depleting antibody KT3 to mice with or without MSC, we found that although T cell depletion prolonged survival, MSC were unable to further enhance this effect. This was also true when MSC were used in combination with the conventional immunosuppressant cyclosporine. Finally, we examined whether the infusion of MSC would compromise the GVL effect. We found that whilst MSC could delay the onset of GVHD, in our model they did not alter the anti-tumour effects of the donor T cells. Overall, we have shown that MSC can delay but not prevent death from GVHD when administered at an appropriate time and dose and that IFNγ is required for MSC-mediated immunosuppression in our model. These data suggest that patients undergoing HSCT should be monitored for IFNγ, and administered MSC when high levels are reached. Whilst MSC may be a promising therapy for patients with severe GVHD, we highlight that further investigation is warranted before MSC are accepted for widespread use in the clinic. The risks and benefits for transplant recipients should be carefully considered before utilising MSC to treat or prevent GVHD.

Introdução: Células-troco mesenquimais (CTM) vêm mostrando seus benefícios na doença do enxerto-versus-hospedeiro (DECH), observada no transplante de células tronco hematopoéticas (TCTH), existem três questões em aberto: (1) Expansão de CTM em meio de cultura suplementado com soro fetal bovino (SFB), pelo o risco de xenorreação; (2) Otimização de condições de cultura para a obtenção, em tempo hábil, de um numero que permita de 4 a 6 infusões de 2x106cells/kg do receptor; (3) Obter células do doador de medula óssea, evitando assim a utilização de um terceiro doador. Objetivos: Este estudo foi desenhado para comparar o lisado de plaquetas (LP) e o SFB na expansão de CTM, a densidade de plaqueamento das células e os dias entre cada passagem, e para investigar se as células nucleadas totais obtidas da bolsa e filtro do TCTH, podem ser utilizadas para expansão de CTM para utilização clínica. Métodos: Células residuais foram removidas do filtro e da bolsa utilizados para o TCTH, plaqueadas e depois da primeira passagem foram cultivadas em diferentes concentrações com SFB ou LP e observado o número de dias que levaram para chegar a 80% de confluência. Em seguida, as culturas com as mesmas densidades de plaqueamento foram suplementadas com LP ou SFB e depois de sete dias contou-se o número de células para analisar o quanto elas cresceram nesse período. Resultados: A proliferação de CTM, na presença de LP e SFB foi em média 11,88 e 2,5 vezes, respectivamente, num período de 7 dias. A concentração mais elevada de células usando LP demorou menos tempo para atingir a confluência, em comparação com os três inferiores. Este estudo sugere que o LP é a melhor escolha como suplemento para expandir CTM, e permite a proliferação de um número suficiente de CTM de doadores para uso clínico. / Introduction: Mesenchymal stromal cells (MSC) have shown their benefits in graft-versus-host disease (GVHD), with three unsettled matters:(1) MSCs expansion in medium with Fetal Calf Serum (FCS) and its risk of xenoreaction; (2) The number of cells indicated for therapy is 2x106cells/Kg with the need to optimize expansion, number and time wise; and (3) the utilization of third party donors. Aims: This study was designed to compare the platelet lysate (LP) and FCS on the expansion of MSC, the optimal cell plating density and days between each pass, and to investigate if donor total nucleated cells (TNC) obtained from the washouts of hematopoietic stem cell transplantation (HSCT) explants can be expanded to be used at clinical grade. Methods: TNC were removed, plated and after the first passage were cultivated in different concentrations with FCS or PL and the number of days reach 80% of confluence was observed. Next, cultures with the same plating density were fed either with PL or FCS and after seven days counted to analyze how much they have grown in that period. Results: The proliferation of mesenchymal stromal cells in the presence of PL and SFB was averaged 11.88 and 2.5 times, respectively, in a period of 7 days. The highest concentration of plating cells using PL, took less time to reach confluence as compared with the three lower ones. This study suggests that the PL is the best choice as a supplement to expand MSC, and allows the proliferation of a sufficient number of donors MSC at P2 for clinical use.