A phase I study to evaluate the safety and tolerability of AB680 combination therapy in participants with gastrointestinal malignancies

TPS788

Background: Metastatic pancreatic ductal adenocarcinoma (mPDAC) expresses very high levels of CD73 among tumor types, and CD73 expression level is a known poor prognostic factor in PDAC. Adenosine, a product of AMP breakdown by CD73, is highly immunosuppressive against effector T & NK cells in the tumor microenvironment. AB680 is the first clinical-stage small-molecule CD73 inhibitor, which is highly potent, pharmacodynamically active, and safe in healthy volunteer dose escalation studies. Targeting the adenosine pathway in combination with standard of care regimens may have a more profound effect on activating and inducing sustained anti-tumor immunity. Methods: This is a Phase 1/1b, open-label, dose-escalation, and dose-expansion study to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and clinical activity of AB680 in combination with AB122 (anti-PD-1 antibody) and standard chemotherapy (nab-paclitaxel [NP] and gemcitabine [Gem]) in participants with first line (1L) mPDAC. In the dose-escalation Ph1 portion, increasing dose levels of AB680 are administered every 2 weeks (Q2W) in combination with AB122 (240 mg Q2W) and NP/Gem (Gem 1000 mg/m2 + NP 125 mg/m2 IV on Days 1, 8, and 15 of each 28-day cycle). Up to 30 participants may be evaluated in Ph1 dose-escalation. In the dose-expansion Ph1b portion, AB680 will be administered at the recommended dose for expansion in combination with AB122 and NP/Gem in up to 40 participants. Adverse events will be graded according to NCI CTCAE 5.0 and antitumor activity assessed using RECIST v1.1. Conclusions: This Ph1/1b study will be the first to target the adenosine axis using a highly potent small-molecule inhibitor of CD73, AB680, in 1L mPDAC in combination with standard of care chemotherapy (NP/Gem) and a PD-1 antibody (AB122). Future results will be shared in upcoming scientific conferences. Clinical trial information: NCT04104672.

Granzyme B regulates antiviral CD8+ T cell responses

CTLs and NK cells use the perforin/granzyme cytotoxic pathway to kill virally infected cells and tumors. Human regulatory T cells also express functional granzymes and perforin and can induce autologous target cell death in vitro. Perforin-deficient mice die of excessive immune responses after viral challenges, implicating a potential role for this pathway in immune regulation. To further investigate the role of granzyme B in immune regulation in response to viral infections, we characterized the immune response in wild-type, granzyme B-deficient, and perforin-deficient mice infected with Sendai virus. Interestingly, granzyme B-deficient mice, and to a lesser extent perforin-deficient mice, exhibited a significant increase in the number of Ag-specific CD8(+) T cells in the lungs and draining lymph nodes of virally infected animals. This increase was not the result of failure in viral clearance because viral titers in granzyme B-deficient mice were similar to wild-type mice and significantly less than perforin-deficient mice. Regulatory T cells from WT mice expressed high levels of granzyme B in response to infection, and depletion of regulatory T cells from these mice resulted in an increase in the number of Ag-specific CD8(+) T cells, similar to that observed in granzyme B-deficient mice. Furthermore, granzyme B-deficient regulatory T cells displayed defective suppression of CD8(+) T cell proliferation in vitro. Taken together, these results suggest a role for granzyme B in the regulatory T cell compartment in immune regulation to viral infections.

Efficacy, safety, and pharmacokinetics of a 10% liquid immune globulin preparation (GAMMAGARD LIQUID, 10%) administered subcutaneously in subjects with primary immunodeficiency disease

A multi-center, prospective, open-label study was conducted in primary immunodeficiency disease patients to determine the tolerability and pharmacokinetics of a 10% liquid IgG preparation administered subcutaneously. Forty-nine subjects (3-77 years old) were enrolled. Pharmacokinetic equivalence of subcutaneous treatment was achieved at a median dose of 137% of the intravenous dose, with a mean trough IgG level of 1,202 mg/dL at the end of the assessment period. The overall infection rate during subcutaneous treatment was 4.1 per subject-year. Three acute serious bacterial infections were reported, resulting in a rate of 0.067 per subject-year. A low overall rate of temporally associated adverse events (8%), and a very low rate of infusion site adverse events (2.8%), was seen at volumes up to 30 mL/site and rates ≤ 30 mL/h/site. Thus, subcutaneous replacement therapy with a 10% IgG preparation proved effective, safe and well-tolerated in our study population of subjects with primary immunodeficiency disease.

Impact of trough IgG on pneumonia incidence in primary immunodeficiency: A meta-analysis of clinical studies

Primary immunodeficiency disease (PIDD) associated with hypogammaglobulinemia is typically treated with immunoglobulin replacement therapy. When administered as intravenous immunoglobulin (IVIG), an IgG trough occurs prior to the next replacement dose. While frequently measured, IgG trough levels required to minimize infection risk are not established. To address this question, all available studies evaluating trough IgG and pneumonia incidence in PIDD patients with hypogammaglobulinemia receiving IVIG were quantitatively combined by meta-analysis. Seventeen studies with 676 total patients and 2,127 patient-years of follow-up were included. Pneumonia incidence declined by 27% with each 100mg/dL increment in trough IgG (incidence rate ratio, 0.726; 95% confidence interval, 0.658-0.801). Pneumonia incidence with maintenance of 500 mg/dL IgG trough levels (0.113 cases per patient-year) was 5-fold that with 1000 mg/dL (0.023 cases per patient-year). This meta-analysis provides evidence that pneumonia risk can be progressively reduced by higher trough IgG levels up to at least 1000 mg/dL.

Multiplexed quantitative real-time PCR to detect 22q11.2 deletion in patients with congenital heart disease

22q11.2 Deletion syndrome (22q11.2 DS) [DiGeorge syndrome type 1 (DGS1)] occurs in ∼1:3,000 live births; 75% of children with DGS1 have severe congenital heart disease requiring early intervention. The gold standard for detection of DGS1 is fluorescence in situ hybridization (FISH) with a probe at the TUPLE1 gene. However, FISH is costly and is typically ordered in conjunction with a karyotype analysis that takes several days. Therefore, FISH is underutilized and the diagnosis of 22q11.2 DS is frequently delayed, often resulting in profound clinical consequences. Our goal was to determine whether multiplexed, quantitative real-time PCR (MQPCR) could be used to detect the haploinsufficiency characteristic of 22q11.2 DS. A retrospective blinded study was performed on 382 subjects who had undergone congenital heart surgery. MQPCR was performed with a probe localized to the TBX1 gene on human chromosome 22, a gene typically deleted in 22q11.2 DS. Cycle threshold (C(t)) was used to calculate the relative gene copy number (rGCN). Confirmation analysis was performed with the Affymetrix 6.0 Genome-Wide SNP Array. With MQPCR, 361 subjects were identified as nondeleted with an rGCN near 1.0 and 21 subjects were identified as deleted with an rGCN near 0.5, indicative of a hemizygous deletion. The sensitivity (21/21) and specificity (361/361) of MQPCR to detect 22q11.2 deletions was 100% at an rGCN value drawn at 0.7. One of 21 subjects with a prior clinical (not genetically confirmed) DGS1 diagnosis was found not to carry the deletion, while another subject, not previously identified as DGS1, was detected as deleted and subsequently confirmed via microarray. The MQPCR assay is a rapid, inexpensive, sensitive, and specific assay that can be used to screen for 22q11.2 deletion syndrome. The assay is readily adaptable to high throughput.

Implementing routine testing for severe combined immunodeficiency within Wisconsin's newborn screening program

Severe combined immunodeficiency (SCID) is the result of genetic defects that impair normal T-cell development. SCID babies typically appear normal at birth, but acquire multiple life-threatening infections within a few months. Early diagnosis and treatment with a bone-marrow transplant markedly improves long-term outcomes. On January 1, 2008, the newborn screening (NBS) program in Wisconsin became the first in the world to routinely test all newborns for SCID. A realtime quantitative polymerase chain reaction assay measures T-cell receptor excision circles (TRECs), which are formed during the maturation of normal T-cells. A lack or very low number of TRECs is consistent with T-cell lymphopenia. The development and validation of the TREC assay and the results of the first year of screening have been published. This article describes the process used to add SCID to the NBS panel, the establishment of follow-up capacity, and the integration of SCID screening into routine NBS workflows. The development of this expanded NBS program is described so that other states might benefit from the processes used in Wisconsin.

Statewide newborn screening for severe T-cell lymphopenia

CONTEXT

A newborn blood screening (NBS) test that could identify infants with a profound deficiency of T cells may result in a reduction in mortality.

OBJECTIVE

To determine if quantitating T-cell receptor excision circles (TRECs) using real-time quantitative polymerase chain reaction on DNA extracted from dried blood spots on NBS cards can detect infants with T-cell lymphopenia in a statewide program.

DESIGN, SETTING, AND PARTICIPANTS

Between January 1 and December 31, 2008, the Wisconsin State Laboratory of Hygiene screened all infants born in Wisconsin for T-cell lymphopenia by quantitating the number of TRECs contained in a 3.2-mm punch (approximately 3 microL of whole blood) of the NBS card. Flow cytometry to enumerate the number of T cells was performed on full-term infants and preterm infants when they reached the equivalent of at least 37 weeks' gestation with TREC values of less than 25/microL. Infants with T-cell lymphopenia were evaluated by a clinical immunologist.

MAIN OUTCOME MEASURES

The number of infants with TREC values of less than 25/microL with T-cell lymphopenia confirmed by flow cytometry.

RESULTS

Exactly 71,000 infants were screened by the TREC assay. Seventeen infants aged at least 37 weeks' gestation had at least 1 abnormal TREC assay (TREC values < 25/microL), 11 of whom had samples analyzed by flow cytometry to enumerate T cells. Eight infants demonstrated T-cell lymphopenia. The causes of the T-cell lymphopenia included DiGeorge syndrome (n = 2), idiopathic T-cell lymphopenia (n = 2), extravascular extravasation of lymphocytes (n = 3), and a Rac2 mutation (n = 1). The infant with the Rac2 mutation underwent successful cord blood transplantation.

CONCLUSION

In a statewide screening program, use of the TREC assay performed on NBS cards was able to identify infants with T-cell lymphopenia.

Development of a routine newborn screening protocol for severe combined immunodeficiency

BACKGROUND

Severe combined immunodeficiency (SCID) is characterized by the absence of functional T cells and B cells. Without early diagnosis and treatment, infants with SCID die from severe infections within the first year of life.

OBJECTIVE

To determined the feasibility of detecting SCID in newborns by quantitating T-cell receptor excision circles (TRECs) from dried blood spots (DBSs) on newborn screening (NBS) cards.

METHODS

DNA was extracted from DBSs on deidentified NBS cards, and real-time quantitative PCR (RT-qPCR) was used to determine the number of TRECs. Positive controls consisted of DBS from a 1-week-old T(-)B(-)NK(+) patient with SCID and whole blood specimens selectively depleted of naive T cells.

RESULTS

The mean and median numbers of TRECs from 5766 deidentified DBSs were 827 and 708, respectively, per 3.2-mm punch ( approximately 3 muL whole blood). Ten samples failed to amplify TRECs on initial analysis; all but 1 demonstrated normal TRECs and beta-actin amplification on retesting. No TRECs were detected in either the SCID or naive T-cell-depleted samples, despite the presence of normal levels of beta-actin.

CONCLUSIONS

The use of RT-qPCR to quantitate TRECs from DNA extracted from newborn DBSs is a highly sensitive and specific screening test for SCID. This assay is currently being used in Wisconsin for routine screening infants for SCID.

Cellular and genetic basis of primary immune deficiencies

Knowledge of the genetic mutations of primary immune deficiency syndromes has grown significantly over the last 30 years. In this article the authors present an overview of the clinical aspects, laboratory evaluation, and genetic defects of primary immunodeficiencies, with an emphasis on the pathophysiology of the known molecular defects. This article is designed to give the primary pediatrician a general knowledge of this rapidly expanding field.

Hemophagocytic lymphohistiocytosis: diagnosis, pathophysiology, treatment, and future perspectives

Hemophagocytic lymphohistiocytosis (HLH) is a rare life-threatening disease in which the immune system becomes overactive due to its inability to effectively respond to infections and/or shut down the immune response to such infections. The discovery of genetic defects in the secretory pathway of natural killer (NK) cells and cytotoxic T cells in some patients with this disease has raised important questions of the role of cytotoxic cells in the control of infections and in immune regulation. This review will give a brief overview of the clinical presentation and accepted treatment of HLH. Furthermore, it will give an in-depth review into the known genetic defects and current knowledge of the pathophysiology of this disorder, and will highlight recent evidence suggesting that cytotoxic defects in CD4+ T regulatory cells may contribute to the pathogenesis of HLH.

Allergic dysregulation and hyperimmunoglobulinemia E in Foxp3 mutant mice

BACKGROUND

Regulatory T cells have been proposed to play an important role in regulating allergic inflammation. The transcription factor Foxp3 is a master switch gene that controls the development and function of natural and adaptive CD4(+)CD25(+) regulatory T (T(R)) cells. In human subjects loss-of-function Foxp3 mutations trigger lymphoproliferation, autoimmunity, and intense allergic inflammation in a disease termed immune dysregulation polyendocrinopathy enteropathy-X-linked syndrome.

OBJECTIVE

We sought to examine the evolution and attributes of allergic inflammation in mice with a targeted loss-of-function mutation in the murine Foxp3 gene that recapitulates a known disease-causing human Foxp3 mutation.

METHODS

Foxp3 mutant mice were generated by means of knock-in mutagenesis and were analyzed for histologic, immunologic, and hematologic abnormalities. The role of signal transducer and activator of transcription 6 (Stat6) in disease pathogenesis was analyzed by using Stat6 and Foxp3 double-mutant mice.

RESULTS

Foxp3 mutant mice developed an intense multiorgan inflammatory response associated with allergic airway inflammation, a striking hyperimmunoglobulinemia E, eosinophilia, and dysregulated T(H)1 and T(H)2 cytokine production in the absence of overt T(H)2 skewing. Concurrent Stat6 deficiency reversed the hyperimmunoglobulinemia E and eosinophilia and delayed mortality, which is consistent with a pathogenic role for allergic inflammation in Foxp3 deficiency.

CONCLUSION

Allergic dysregulation is a common and fundamental consequence of loss of CD4(+)CD25(+) T(R) cells caused by Foxp3 deficiency in different species. Abnormalities affecting T(R) cells might contribute to a variety of allergic diseases.

A novel reduced-intensity stem cell transplant regimen for nonmalignant disorders

Bone marrow transplantation (BMT) benefits nonmalignant diseases but is limited by regimen-related toxicity, graft-versus-host disease (GVHD), donor availability, and graft rejection (GR). To overcome some of these barriers, we developed a new conditioning strategy for these patients. In total, 16 patients received Campath-1H (33/48 mg; days -21 to -19), fludarabine (150 mg/m(2); days -8 to -4), melphalan (140/70 mg/m(2); day -3), and transplant using related/unrelated stem cells. GVHD prophylaxis included cyclosporine/methylprednisolone for cord cells. Other recipients also received methotrexate. Risk factors for GR included multiple transfusions (6), low stem cell numbers (1), and immunologic/metabolic disorders (3). Donor engraftment was present in 14/16 recipients. Neutrophils (ANC>0.5 x 10(9)/l) and platelets (>50 x 10(9)/l) engrafted at a median of 13 and 24 days. Two patients died of Pseudomonas sepsis prior to engraftment, one of CMV disease, and another of intracranial hemorrhage. With median follow-up of 281 days (78-907), 12/16 are stable/improved, or cured. Acute GVHD was absent (n=10) or mild and transient (grade1-2 skin) (n=4). There was no chronic GVHD. Toxicities were predominantly early infections within 100 days, and correlated with lymphopenia (CD4+ T and B cells). Stable engraftment and low incidence of significant GVHD, irrespective of age or stem cell source, make this reduced-intensity regimen attractive for nonmalignant disorders.

Development of hemophagocytic lymphohistiocytosis in triplets infected with HHV-8

Hemophagocytic lymphohistiocytosis (HLH) is a rare disorder of immune dysregulation, characterized by end-organ damage from lymphocytic infiltration and macrophage activation. All known mutations associated with the HLH occur in genes critical in the perforin-granzyme pathway. Herein, we report HLH occurring in 2 female triplet infants who also had associated human herpesvirus type 8 (HHV-8) infections. The subjects had identical novel compound-heterozygous mutations in the Perforin alleles, resulting in undetectable perforin expression and NK-cell cytotoxicity. Both infants also had evidence of infection with HHV-8. These reports are, to our knowledge, the first cases of HLH in triplets and the first reported cases of HHV-8 infection associated with HLH in non-renal transplant and non-HIV-infected subjects.

Granzyme B and the Downstream Granzymes C and/or F Are Important for Cytotoxic Lymphocyte Functions

Although the functions of granzyme A (GzmA) and GzmB are well-defined, a number of orphan granzymes of unknown function are also expressed in cytotoxic lymphocytes. Previously, we showed that a targeted loss-of-function mutation for GzmB was associated with reduced expression of several downstream orphan granzyme genes in the lymphokine-activated killer cell compartment. To determine whether this was caused by the retained phosphoglycerate kinase I gene promoter (PGK-neo) cassette in the GzmB gene, we retargeted the GzmB gene with a LoxP-flanked PGK-neo cassette, then removed the cassette in embryonic stem cells by transiently expressing Cre recombinase. Mice homozygous for the GzmB null mutation containing the PGK-neo cassette (GzmB-/-/+PGK-neo) displayed reduced expression of the closely linked GzmC and F genes in their MLR-derived CTLs and lymphokine-activated killer cells; removal of the PGK-neo cassette (GzmB-/-/DeltaPGK-neo) restored the expression of both genes. Cytotoxic lymphocytes derived from mice with the retained PGK-neo cassette (GzmB-/-/+PGK-neo) had a more severe cytotoxic defect than those deficient for GzmB only (GzmB-/-/DeltaPGK-neo). Similarly, GzmB-/-/+PGK-neo mice displayed a defect in the allogeneic clearance of P815 tumor cells, whereas GzmB-/-/DeltaPGK-neo mice did not. These results suggest that the retained PGK-neo cassette in the GzmB gene causes a knockdown of GzmC and F expression, and also suggest that these granzymes are relevant for the function of cytotoxic lymphocytes in vitro and in vivo.

Human T Regulatory Cells Can Use the Perforin Pathway to Cause Autologous Target Cell Death

Cytotoxic T lymphocytes and natural killer cells use the perforin/granzyme pathway to kill virally infected cells and tumor cells. Mutations in genes important for this pathway are associated with several human diseases. CD4(+) T regulatory (Treg) cells have emerged as important in the control of immunopathological processes. We have previously shown that human adaptive Treg cells preferentially express granzyme B and can kill allogeneic target cells in a perforin-dependent manner. Here, we demonstrate that activated human CD4(+)CD25(+) natural Treg cells express granzyme A but very little granzyme B. Furthermore, both Treg subtypes display perforin-dependent cytotoxicity against autologous target cells, including activated CD4(+) and CD8(+) T cells, CD14(+) monocytes, and both immature and mature dendritic cells. This cytotoxicity is dependent on CD18 adhesive interactions but is independent of Fas/FasL. Our findings suggest that the perforin/granzyme pathway is one of the mechanisms that Treg cells can use to control immune responses.

Differential expression of granzymes A and B in human cytotoxic lymphocyte subsets and T regulatory cells

Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells use the perforin/granzyme pathway as a major mechanism to kill pathogen-containing cells and tumor cells.(1,2) Dysregulation of this pathway results in several human diseases, such as hemophagocytic lymphohistiocytosis. Here we characterize the single-cell expression pattern of granzymes A and B in human lymphocytes using a flow cytometry-based assay. We demonstrate that most circulating CD56(+)8(-) NK cells, and approximately half of circulating CD8(+) T lymphocytes, coexpressed both granzymes A and B. In contrast, few circulating CD4(+) T lymphocytes expressed granzymes A or B. Activation of CD8(+) T lymphocytes with concanavalin A (ConA)/interleukin-2 (IL-2), and activation of CD4(+) T lymphocytes with antibodies to CD3/CD28 or CD3/CD46 (to generate T regulatory [Tr1] cells), induced substantial expression of granzyme B, but not granzyme A. Naive CD4(+)CD45RA(+) cells stimulated with antibodies to CD3/CD46 strongly expressed granzyme B, while CD3/CD28 stimulation was ineffective. Finally, we show that granzyme B-expressing CD4(+) Tr1 cells are capable of killing target cells in a perforin-dependent, but major histocompatibility complex (MHC)/T-cell receptor (TCR)-independent, manner. Our results demonstrate discordant expression of granzymes A and B in human lymphocyte subsets and T regulatory cells, which suggests that different granzymes may play unique roles in immune system responses and regulation.

Isolated CNS relapse following stem cell transplantation for juvenile myelomonocytic leukemia

A 1-year-old girl with juvenile myelomonocytic leukemia (JMML) underwent allogeneic bone marrow transplantation (BMT) from her HLA-matched brother. A few months after BMT she experienced a bone marrow relapse that did not respond to withdrawal of immunosuppression. To enhance the graft-versus-leukemia (GVL) effect, she underwent peripheral stem cell transplantation (PSCT) from the same donor, using a nonmyeloablative conditioning regimen. She achieved clinical remission and developed chronic graft-versus-host disease (GVHD), which was treated with prednisone and cyclosporine A. One year after PSCT she experienced an isolated central nervous system (CNS) relapse. She was treated with intrathecal Ara-C followed by craniospinal irradiation and achieved a third clinical remission. While extramedullary relapses have been described in JMML, this is the first report of a CNS relapse. Based on this case and others in the literature, the authors suggest that newer therapies are changing the natural history of JMML. By manipulating the GVL effect it is possible to achieve a prolonged bone marrow remission, but only at the expense of unmasking the risk of late extramedullary relapse.

Sudden unexplained hemolysis occurring in an infant due to presumed Loxosceles envenomation

We report the case of a 3-week-old infant referred for evaluation of sudden onset jaundice and unexplained hemolysis. After an exhaustive workup, the most likely etiology was found to be envenomation by a brown recluse spider, Loxosceles reclusa. This case underscores the fact that severe loxoscelism may occur in the absence of the classically described necrotic cutaneous lesion, and represents one of the youngest presumed cases of loxoscelism. We present the case to illustrate the importance of considering loxoscelism in the differential diagnosis of sudden massive hemolysis in children, particularly in endemic areas of the midwestern and southern United States.

The orphan granzymes of humans and mice

The granzyme/perforin pathway is a central pathway for lymphocyte-mediated killing in both the innate and adaptive immune systems. This pathway is important in a variety of host defenses, including viral clearance and tumor cell killing, and its dysregulation results in several human and rodent diseases. To date, the majority of reports in this field have concentrated on the functions of granzymes A and B. Recent reports, however, suggest that the non-A/non-B 'orphan' granzymes found in both humans and mice are potentially significant. Although the functions of these orphan granzymes have yet to be fully established, initial data suggests their importance in both immune and nonimmune cells.

Analysis of p53 inactivation in a human T-cell leukemia virus type 1 Tax transgenic mouse model

Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent of adult T-cell leukemia/lymphoma (ATLL). The HTLV-1 Tax protein has been strongly linked to oncogenesis and is considered to be the transforming protein of this virus. A Tax transgenic mouse model was utilized to study the contribution of p53 inactivation to Tax-mediated tumorigenesis. These mice develop primary, peripheral tumors consisting of large granular lymphocytic (LGL) cells, which also infiltrate the lymph nodes, bone marrow, spleen, liver, and lungs. Primary Tax-induced tumors and tumor-derived cell lines exhibited functional inactivation of the p53 apoptotic pathway; such tumors and tumor cell lines were resistant to an apoptosis-inducing stimulus. In contrast, p53 mutations in tumors were found to be associated with secondary organ infiltration. Three of four identified mutations inhibited transactivation and apoptosis induction activities in vitro. Furthermore, experiments which involved mating Tax transgenic mice with p53-deficient mice demonstrated minimal acceleration in initial tumor formation, but significantly accelerated disease progression and death in mice heterozygous for p53. These studies suggest that functional inactivation of p53 by HTLV-1 Tax, whether by mutation or another mechanism, is not critical for initial tumor formation, but contributes to late-stage tumor progression.

Dysregulated myelopoiesis in mice lacking Jak3

Jak3 is a cytoplasmic tyrosine kinase that associates with the common chain of the interleukin-2 (IL-2) receptor and is involved in the function of the receptors for IL-2, IL-4, IL-7, IL-9, and IL-15. Mice deficient in Jak3 have few T and B cells, and no natural killer cells. Herein we show that the myeloid lineages in these mice are also affected by the loss of Jak3. Mice lacking Jak3 exhibit splenomegaly by 4 months of age. Peripheral blood smears show an increase in the number of neutrophils and cells of the monocytic lineage. Flow cytometry of splenocytes and peripheral blood show a significant increase in FcgammaRII/III(FcgammaR)/Mac-1, FcgammaR/Gr-1, and FcgammaR/F4/80 double-positive cells in -/- and +/- mice compared to wild-type mice, consistent with an expansion of cells of the myeloid lineages. In addition, as the mice age, F4/80 and CD3 positive mononuclear cells infiltrate the kidneys, lungs, and liver of these mice. When Jak3-/- mice are crossed with a transgenic mouse expressing Jak3 in the T and NK cell compartments, the splenomegaly and myeloid expansion are accentuated. These data correlate with the constitutive activation of T cells in the periphery as the transgenic cells lose their expression of Jak3 with age. However, when Jak3-/- mice are crossed with RAG-1-deficient animals, no splenomegaly or myeloid expansion is apparent. These results indicate that the loss of Jak3 in the T-cell compartment drives the expansion of the myeloid lineages.

Cytokine expression and tumorigenicity of large granular lymphocytic leukemia cells from mice transgenic for the tax gene of human T-cell leukemia virus type I

The human T-cell leukemia virus type I (HTLV-I) regulatory protein, Tax, has been speculated to play a major role in HTLV-I leukemogenesis. Indeed, several studies have suggested that upregulation of various cellular oncogenes and cytokines by Tax may explain the pathogenesis observed in HTLV-I-infected individuals, as well as several Tax-transgenic animal models. We report here the analysis of cytokine expression in a Tax-transgenic animal model with large granular lymphocytic (LGL) leukemia. Two different transgenic mice showed identical expression of interleukin-1alpha (IL-1alpha), IL-1beta, interferon gamma (IFNgamma), and granulocyte-macrophage colony-stimulating factor (GM-CSF) in peripheral tail tumors. Interestingly, LGL cell lines derived from these same tumors expressed high levels of both IFNgamma and GM-CSF, which correlated with the level of Tax expression. These same LGL cell lines also expressed high levels of lymphocyte function-associated antigen-1 (LFA-1) and intracellular adhesion molecule-1 (ICAM-1). Engraftment of these LGL cell lines into severe combined immunodeficient (SCID) mice led to the development of leukemia and lymphomas. Examination of these SCID mice showed that their pathology was nearly identical to that observed in the original Tax-transgenic mouse model. Both the Tax-transgenic and engrafted SCID mouse models allow for the analysis of cellular events that are required for tumor development associated with HTLV infection and suggest that Tax expression may be responsible for the upregulation of certain cytokines and adhesion molecules that affect the infiltrating capabilities of HTLV-I-infected cells.

Transgenic mouse models for HTLV-I infection

Human T-cell leukemia virus type I (HTLV-I) was the first human retrovirus isolated and is responsible for at least one form of human leukemia. The pathogenic mechanism(s) whereby HTLV transforms T lymphocytes in vivo is(are) obscure due to its long-term latency and the lack of practical representative animal models. The tax gene of HTLV-I has been implicated in this transformation process because of its ability to transactivate several cellular genes associated with T-cell replication and activation. Here, transgenic mouse models are discussed that express the Tax protein of HTLV-I and provide insights into its role in the cellular transformation process.

Development of leukemia in mice transgenic for the tax gene of human T-cell leukemia virus type I

The human T-cell leukemia virus type I Tax protein trans-activates several cellular genes implicated in T-cell replication and activation. To investigate its leukemogenic potential, Tax was targeted to the mature T-lymphocyte compartment in transgenic mice by using the human granzyme B promoter. These mice developed large granular lymphocytic leukemia, demonstrating that expression of Tax in the lymphocyte compartment is sufficient for the development of leukemia. Furthermore, these observations suggest that human T-cell leukemia virus infection may be involved in the development of large granular lymphocytic leukemia.

Antihypertensive effects of lofexidine in patients with essential hypertension

1 Single oral doses of lofexidine, 0.1, 0.3, and 0.6 mg produced dose related decreases in supine and standing arterial pressure and heart rate in nineteen patients with essential hypertension. 2 A mean oral antihypertensive threshold dose of less than 0.1 mg was estimated. 3 Lofexidine decreased mean urinary noradrenaline excretion 28% and caused significant retention of sodium and water. 4 The most prominent side effects were sedation and orthostatic dizziness. 5 Lofexidine is pharmacologically similar to, but apparently less potent than clonidine as an antihypertensive agent.