Treatment of cyclic neutropenia with granulocyte colony-stimulating factor

Erythropoietin: A Personal Alice in Wonderland Trip in the Shadow of the Giants

The identification of the hormone erythropoietin (EPO), which regulates red blood cell production, and its development into a pharmaceutical-grade product to treat anemia has been not only a herculean task but it has also been the first of its kind. As with all the successes, it had "winners" and "losers", but its history is mostly told by the winners who, over the years, have published excellent scientific and divulgate summaries on the subject, some of which are cited in this review. In addition, "success" is also due to the superb and dedicated work of numerous "crew" members, who often are under-represented and under-recognized when the story is told and often have several "dark sides" that are not told in the polished context of most reviews, but which raised the need for the development of the current legislation on biotherapeutics. Although I was marginally involved in the clinical development of erythropoietin, I have known on a personal basis most, if not all, the protagonists of the saga and had multiple opportunities to talk with them on the drive that supported their activities. Here, I will summarize the major steps in the development of erythropoietin as the first bioproduct to enter the clinic. Some of the "dark sides" will also be mentioned to emphasize what a beautiful achievement of humankind this process has been and how the various unforeseen challenges that emerged were progressively addressed in the interest of science and of the patient's wellbeing.

The highs and lows of cyclic thrombocytopenia

Cyclic thrombocytopenia (CTP) is characterized by periodic platelet oscillation with substantial amplitude. Most CTP cases have a thrombocytopenic background and are often misdiagnosed as immune thrombocytopenia with erratically effective treatment choices. CTP also occurs during hydroxyurea treatment in patients with myeloproliferative diseases. While the aetiology of CTP remains uncertain, here we evaluate historical, theoretical and clinical findings to provide a framework for understanding CTP pathophysiology. CTP retains the intrinsic oscillatory factors defined by the homeostatic regulation of platelet count, presenting as reciprocal platelet/thrombopoietin oscillations and stable oscillation periodicity. Moreover, CTP patients possess pathogenic factors destabilizing the platelet homeostatic system thereby creating opportunities for external perturbations to initiate and sustain the exaggerated platelet oscillations. Beyond humoral and cell-mediated autoimmunity, we propose recently uncovered germline and somatic genetic variants, such as those of MPL, STAT3 or DNMT3A, as pathogenic factors in thrombocytopenia-related CTP. Likewise, the JAK2 V617F or BCR::ABL1 translocation that drives underlying myeloproliferative diseases may also play a pathogenic role in hydroxyurea-induced CTP, where hydroxyurea treatment can serve as both a trigger and a pathogenic factor of platelet oscillation. Elucidating the pathogenic landscape of CTP provides an opportunity for targeted therapeutic approaches in the future.

Efficacy of Low-Dose rhGM-CSF Treatment in a Patient With Severe Congenital Neutropenia Due to CSF3R Deficiency: Case Report of a Novel Biallelic CSF3R Mutation and Literature Review

This study reports the clinical manifestations, genetics, and efficacy of treatment with the efficacy of recombinant human granulocyte macrophage colony-stimulating factor (rhGM-GSF) of a 2-year-old female patient with severe congenital neutropenia (SCN) type 7 (SCN7) caused by novel biallelic mutations in the colony-stimulating factor 3 receptor (CSF3R) gene. Genetic diagnosis of the patient was performed by whole-exome and Sanger sequencing. Expression of the CSF3R gene in the peripheral neutrophils of the patient was detected by real-time PCR and Western blotting. The patient presented with recurrent suppurative tonsillitis and decreased absolute neutrophil count <0.5 × 10⁹/L. Novel heterozygous mutations were found to be inherited from each parent (maternal c.690delC [p.met231Cysfs^*32] and paternal c.64+5G>A). The patient's neutrophils had lower CSF3R mRNA and protein levels than those of the parents. Low-dose rhGM-CSF (3 μg/kg/day once a week) prevented recurrent infection in the patient. These results demonstrate that the clinical manifestations of SCN7 with biallelic CSF3R mutations and downregulated CSF3R can be effectively treated with rhGM-CSF.

In canine bacterial pneumonia circulating granulocyte counts determine outcome from donor cells

BACKGROUND

In experimental canine septic shock, depressed circulating granulocyte counts were associated with a poor outcome and increasing counts with prophylactic granulocyte colony-stimulating factor (G-CSF) improved outcome. Therapeutic G-CSF, in contrast, did not improve circulating counts or outcome, and therefore investigation was undertaken to determine whether transfusing granulocytes therapeutically would improve outcome.

STUDY DESIGN AND METHODS

Twenty-eight purpose-bred beagles underwent an intrabronchial Staphylococcus aureus challenge and 4 hours later were randomly assigned to granulocyte (40-100 × 109 cells) or plasma transfusion.

RESULTS

Granulocyte transfusion significantly expanded the low circulating counts for hours compared to septic controls but was not associated with significant mortality benefit (1/14, 7% vs. 2/14, 14%, respectively; p = 0.29). Septic animals with higher granulocyte count at 4 hours (median [interquartile range] of 3.81 3.39-5.05] vs. 1.77 [1.25-2.50]) had significantly increased survival independent of whether they were transfused with granulocytes. In a subgroup analysis, animals with higher circulating granulocyte counts receiving donor granulocytes had worsened lung injury compared to septic controls. Conversely, donor granulocytes decreased lung injury in septic animals with lower counts.

CONCLUSION

During bacterial pneumonia, circulating counts predict the outcome of transfusing granulocytes. With low but normal counts, transfusing granulocytes does not improve survival and injures the lung, whereas for animals with very low counts, but not absolute neutropenia, granulocyte transfusion improves lung function.

New insights into the pathomechanism of cyclic neutropenia

Cyclic neutropenia (CyN) is a hematologic disorder in which peripheral blood absolute neutrophil counts (ANCs) show cycles of approximately 21-day intervals. The majority of CyN patients harbor ELANE mutations, but the mechanism of ANC cycling is unclear. We performed analysis of bone marrow (BM) subpopulations in CyN patients at the peak and the nadir of the ANC cycle and detected high proportions of BM hematopoietic stem cells (HSCs) and hematopoietic stem and progenitor cells (HSPCs) at the nadir of the ANC cycle, as compared with the peak. BM HSPCs produced fewer granulocyte colony-forming unit colonies at the ANC peak. To investigate the mechanism of cycling, we found that mRNA expression levels of ELANE and unfolded protein response (UPR)-related genes (ATF6, BiP (HSPA5), CHOP (DDIT3), and PERK (EIF2AK3)) were elevated, but antiapoptotic genes (Bcl-2 (BCL2) and bcl-xL (BCL2L1)) were reduced in CD34⁺ cells tested at the ANC nadir. Moreover, HSPCs revealed increased levels of reactive oxygen species and gH2AX at the ANC nadir. We suggest that in CyN patients, some HSPCs escape the UPR-induced endoplasmic reticulum (ER) stress and proliferate in response to granulocyte colony-stimulating factor (G-CSF) to a certain threshold at which UPR again affects the majority of HSPCs. There is a cyclic balance between ER stress-induced apoptosis of HSPCs and compensatory G-CSF-stimulated HSPC proliferation followed by granulocytic differentiation.

Registries for study of nonmalignant hematological diseases: the example of the Severe Chronic Neutropenia International Registry

PURPOSE OF REVIEW

Registries provide 'real world' perspectives on the natural history and outcomes for many clinical conditions. The purpose of this review is to identify registries for nonmalignant hematological disease and to describe the operation of a successful long-term registry for patients with severe chronic neutropenia.

RECENT FINDINGS

There was an upswing in registries about 20 years ago, based on optimism about their utility to improve patient care. To show value, registries must define outcomes for populations of patients with specific medical conditions and the effects of treatment. This is challenging for many reasons. The Severe Chronic Neutropenia International Registry is an example of a successful registry. This report describes underlying reasons for its success.

SUMMARY

Registries are important to organize and analyze clinical information across geographic, ethnic and social boundaries. They are also challenging to organize, administer and support.

Severe congenital neutropenias

Severe congenital neutropenias are a heterogeneous group of rare haematological diseases characterized by impaired maturation of neutrophil granulocytes. Patients with severe congenital neutropenia are prone to recurrent, often life-threatening infections beginning in their first months of life. The most frequent pathogenic defects are autosomal dominant mutations in ELANE, which encodes neutrophil elastase, and autosomal recessive mutations in HAX1, whose product contributes to the activation of the granulocyte colony-stimulating factor (G-CSF) signalling pathway. The pathophysiological mechanisms of these conditions are the object of extensive research and are not fully understood. Furthermore, severe congenital neutropenias may predispose to myelodysplastic syndromes or acute myeloid leukaemia. Molecular events in the malignant progression include acquired mutations in CSF3R (encoding G-CSF receptor) and subsequently in other leukaemia-associated genes (such as RUNX1) in a majority of patients. Diagnosis is based on clinical manifestations, blood neutrophil count, bone marrow examination and genetic and immunological analyses. Daily subcutaneous G-CSF administration is the treatment of choice and leads to a substantial increase in blood neutrophil count, reduction of infections and drastic improvement of quality of life. Haematopoietic stem cell transplantation is the alternative treatment. Regular clinical assessments (including yearly bone marrow examinations) to monitor treatment course and detect chromosomal abnormalities (for example, monosomy 7 and trisomy 21) as well as somatic pre-leukaemic mutations are recommended.

How I manage children with neutropenia

Neutropenia, usually defined as a blood neutrophil count <1·5 × 10⁹ /l, is a common medical problem for children and adults. There are many causes for neutropenia, and at each stage in life the clinical pattern of causes and consequences differs significantly. I recommend utilizing the age of the child and clinical observations for the preliminary diagnosis and primary management. In premature infants, neutropenia is quite common and contributes to the risk of sepsis with necrotizing enterocolitis. At birth and for the first few months of life, neutropenia is often attributable to isoimmune or alloimmune mechanisms and predisposes to the risk of severe bacterial infections. Thereafter when a child is discovered to have neutropenia, often associated with relatively minor symptoms, it is usually attributed to autoimmune disorder or viral infection. The congenital neutropenia syndromes are usually recognized when there are recurrent infections, the neutropenia is severe and there are congenital anomalies suggesting a genetic disorder. This review focuses on the key clinical finding and laboratory tests for diagnosis with commentaries on treatment, particularly the use of granulocyte colony-stimulating factor to treat childhood neutropenia.

Allogeneic Transplant in ELANE and MEFV Mutation Positive Severe Cyclic Neutropenia: Review of Prognostic Factors for Secondary Severe Events

Objective and Importance. Cyclic neutropenia (CyN) is a rare autosomal dominant inherited disorder due to the mutation ELANE primarily affecting bone marrow stem cells and is characterized by recurrent neutropenia every 2 to 4 weeks. Symptoms vary from benign to severe, including death. Postulations on the cause of wide spectrum in symptom presentation include the possibility of other genetic mutations, such as MEFV. Recommended treatment for CyN is G-CSF to keep ANC higher to minimize risk of infection. Case. A 25-year-old male diagnosed with CyN, on G-CSF but worsening quality of life. Pretransplant investigations revealed ELANE mutation positive severe CyN along with familial Mediterranean fever (MEFV) mutation. Intervention. Bone marrow transplantation as treatment for dual mutation (ELANE and MEFV mutation) positive severe CyN. Conclusion. BMT may be considered as an alternative treatment for severe CyN in patients who are refractory to G-CSF. It is postulated that in our patient the combined mutations (CyN and MEFV) may have contributed to the severity of this individual's symptoms. We suggest CyN patients who present with severe symptoms have evaluation with ELANE mutation testing, Periodic Fever Syndromes Panel, and routine marrow assessment with FISH, conventional cytogenetics, and morphological evaluation for MDS/AML.

G-CSF and GM-CSF in Neutropenia

G-CSF and GM-CSF are used widely to promote the production of granulocytes or APCs. The U.S. Food and Drug Administration approved G-CSF (filgrastim) for the treatment of congenital and acquired neutropenias and for mobilization of peripheral hematopoietic progenitor cells for stem cell transplantation. A polyethylene glycol-modified form of G-CSF is approved for the treatment of neutropenias. Clinically significant neutropenia, rendering an individual immunocompromised, occurs when their number is <1500/μl. Current guidelines recommend their use when the risk for febrile neutropenia is >20%. GM-CSF (sargramostim) is approved for neutropenia associated with stem cell transplantation. Because of its promotion of APC function, GM-CSF is being evaluated as an immunostimulatory adjuvant in a number of clinical trials. More than 20 million persons have benefited worldwide, and >$5 billion in sales occur annually in the United States.

Recombinant Hemopoietic Growth Factors: Comparative Hemopoietic Response in Younger and Older Subjects

OBJECTIVE

To study the effectiveness of hemopoietic growth factors in older patients.

DESIGN

Literature review. All articles published in English language between 1987 and 1990 were reviewed. Those reporting studies without age limits as entry criteria and describing the effects of growth factors in individual patients were suitable for analysis. Bone marrow transplantation related articles were excluded.

MAIN OUTCOME MEASURES

The meanfold increase of granulocytes for Granulocyte-Colony Stimulating Factor, Granulocyte Macrophage-Colony Stimulating Factor, and Interleukin 3 and of hemoglobin for erythropoietin were compared in subjects younger and older than 65, by Mann-Whitney U test.

RESULTS

Of 68 studies, 23 were suitable for analysis. These included patients with myelodysplastic syndromes, aplastic anemia, chemotherapy-induced myelosuppression, chronic granulocytopenia, anemia, and myelosuppression of malignancies and of chronic disease. Of 204 patients, 67 were 65 years of age or older and 42 were over 70. No difference was seen in meanfold increase of granulocyte and hemoglobin in time of response to growth factors or in response in presence of an absolute neutrophil count lower than 1000/microliters between younger and older patients.

CONCLUSION

Early response to hemopoietic growth factors appears well maintained with advanced age. Prospective studies of the prolonged effects of these factors in older and younger patients are needed.

Understanding, treating and avoiding hematological disease: better medicine through mathematics?

This paper traces the experimental, clinical and mathematical modeling efforts to understand a periodic hematological disease-cyclical neutropenia. It is primarily a highly personal account by two scientists from quite different backgrounds of their interactions over almost 40 years and their attempts to understand this intriguing disease. It's also a story of their efforts to offer effective treatments for the patients who suffer from cyclic neutropenia and other conditions causing neutropenia and infections.

Leukocyte integrin activation mediates transient neutropenia after G-CSF administration

After administration of granulocyte colony-stimulating factor (G-CSF), there is a marked, albeit transient, drop in circulating neutrophils. To determine the role of leukocyte integrins in this disappearance, a dog having canine leukocyte adhesion deficiency (CLAD) or CLAD dogs who had undergone gene correction either by matched littermate allogeneic transplant or autologous gene therapy were evaluated. Shortly after G-CSF administration, a dramatic, yet transient, neutropenia was observed in the control littermates. This neutropenia was not as marked in the CLAD dogs. In all instances, it was CD18(+) neutrophils that preferentially egressed from the circulation. The association of CD18 with this rapid loss suggested leukocyte integrin activation after G-CSF administration. To determine the activation status of the integrin, a monoclonal antibody recognizing the activated α-subunit cation binding domain (mAb24) was used to evaluate human leukocytes after G-CSF administration. Mirroring the dramatic decrease in circulating neutrophil numbers, there was a dramatic and specific increase in the activation of the α-subunit after G-CSF expression on polymorphonuclear leukocytes. This activation, like the drop in neutrophil count, was transient. These results demonstrate that the leukocyte integrin on circulating neutrophils is transiently activated after G-CSF administration and mediates the transient neutropenia observed after G-CSF administration.

A case of systemic amyloidosis associated with cyclic neutropenia

Reactive AA amyloidosis is caused by the accumulation of the acute phase reactant, serum amyloid A (SAA), as a complication of chronic inflammatory conditions. Cyclic neutropenia is a rare hereditary disorder characterized by repeated episodes of neutropenia at regular intervals, with or without concurrent infection, and is known to be a rare cause of AA amyloidosis. Here, we report a case of a patient who developed systemic AA amyloidosis following a prolonged course of undiagnosed cyclic neutropenia. The patient had a history of recurrent infections since infancy and developed goiter, proteinuria, and azotemia at age 14 years. Her SAA level was markedly increased (601.8 μg/mL, normal range <8 μg/mL), and a thyroid and kidney biopsy revealed typical lesions of AA amyloidosis. Amyloid deposits were also detected in the myocardium, colon, and gallbladder. She had repeated episodes of neutropenia regularly at 3-week intervals and a pathogenic mutation in the ELA2 gene. After 10 months of treatment with recombinant human granulocyte colony-stimulating factor, her SAA level normalized (<2.5 μg/mL), but her renal function did not recover. This case clearly shows that cyclic neutropenia can be complicated by AA amyloidosis unless it is detected early and treated adequately.

G-CSF influences mouse skeletal muscle development and regeneration by stimulating myoblast proliferation

Granulocyte colony-stimulating factor and its receptor are needed for skeletal muscle development and injury-induced regeneration in mice.

After skeletal muscle injury, neutrophils, monocytes, and macrophages infiltrate the damaged area; this is followed by rapid proliferation of myoblasts derived from muscle stem cells (also called satellite cells). Although it is known that inflammation triggers skeletal muscle regeneration, the underlying molecular mechanisms remain incompletely understood. In this study, we show that granulocyte colony-stimulating factor (G-CSF) receptor (G-CSFR) is expressed in developing somites. G-CSFR and G-CSF were expressed in myoblasts of mouse embryos during the midgestational stage but not in mature myocytes. Furthermore, G-CSFR was specifically but transiently expressed in regenerating myocytes present in injured adult mouse skeletal muscle. Neutralization of endogenous G-CSF with a blocking antibody impaired the regeneration process, whereas exogenous G-CSF supported muscle regeneration by promoting the proliferation of regenerating myoblasts. Furthermore, muscle regeneration was markedly impaired in G-CSFR–knockout mice. These findings indicate that G-CSF is crucial for skeletal myocyte development and regeneration and demonstrate the importance of inflammation-mediated induction of muscle regeneration.

Cyclic and chronic neutropenia

Patients with severe chronic neutropenia have blood neutrophil level <0.5 × 10(9)/L, predisposing them to increased susceptibility to life-threatening bacterial infections. This chapter focuses on cyclic and congenital neutropenia, two very interesting and rare hematological conditions causing severe chronic neutropenia. Both disorders respond well to treatment with the myeloid growth factor, granulocyte colony-stimulating factor (G-CSF). This chapter describes the basic features of these diseases and addresses several current clinical issues regarding their diagnosis and management. Cyclic neutropenia is a rare, inherited autosomal dominant disorder due to mutations in the gene for neutrophil elastase (ELA-2 or ELANE). Usually these patients have regular oscillation of blood neutrophil counts with periods of severe neutropenia occurring every 21 days. During these periods, they have painful mouth ulcers, fevers, and bacterial infections. The most severe consequences are gangrene, bacteremia, and septic shock. Cyclic neutropenia patients respond well to treatment with granulocyte colony-stimulating factor (G-CSF) given by subcutaneous injections on a daily or alternate-day basis. Severe congenital neutropenia is also a rare hematological disease, but it is probably more common than cyclic neutropenia. Blood neutrophils are extremely low on a continuing basis; the levels may be <0.2 × 10(9)/L, and the risk of severe bacterial infections is even greater than in cyclic neutropenia. The majority of cases are due to autosomal dominant inheritance of mutations in the ELA-2 or ELANE gene. Less commonly, mutations in HAX-1, G6PC3, and other genes cause this disorder. Treatment with G-CSF is usually effective, but the dose of G-CSF required to normalize blood neutrophils varies greatly. Ten to thirty percent of severe congenital neutropenia patients evolve to develop acute myeloid leukemia, necessitating careful clinical monitoring.

Cyclic neutropenia and severe congenital neutropenia in patients with a shared ELANE mutation and paternal haplotype: evidence for phenotype determination by modifying genes

BACKGROUND

Cyclic neutropenia (CN) and severe congenital neutropenia (SCN) are disorders of neutrophil production that differ markedly in disease severity. Mutations of the ELANE gene (the symbol recently replacing ELA2) are considered largely responsible for most cases of CN and SCN, but specific mutations are typically associated with one or the other.

PROCEDURE

We performed ELANE genotyping on all individuals and paternal sperm in an SCN kindred with eight SCN progeny of a sperm donor and six different mothers.

RESULTS

One patient with CN had the same S97L ELANE mutation as seven patients with the SCN phenotype. The mutant allele was detected in the donor's spermatozoa, representing 18% of the ELANE gene pool, but not in DNA from his lymphocytes, neutrophils, or buccal mucosa, indicating gonadal mosaicism.

CONCLUSIONS

The coexistence of CN and SCN phenotypes in this kindred with a shared paternal haplotype strongly suggests both a role for modifying genes in determination of congenital neutropenia disease phenotypes, and the classification of CN and SCN within a spectrum of phenotypes expressing varying degrees of the same disease process.

The colony-stimulating factors and cancer

The four colony-stimulating factors (CSFs) are glycoproteins that regulate the generation and some functions of infection-protective granulocytes and macrophages. Recombinant granulocyte-CSF (G-CSF) and granulocyte-macrophage-CSF (GM-CSF) have now been used to increase dangerously low white blood cell levels in many millions of cancer patients following chemotherapy. These CSFs also release haematopoietic stem cells to the peripheral blood, and these cells have now largely replaced bone marrow as more effective populations for transplantation to cancer patients who have treatment-induced bone marrow damage.

Progenitor cell self-renewal and cyclic neutropenia

OBJECTIVES

Cyclic neutropenia (CN) is a rare genetic disorder where patients experience regular cycling of numbers of neutrophils and various other haematopoietic lineages. The nadir in neutrophil count is the main source of problems due to risk of life-threatening infections. Patients with CN benefit from granulocyte colony stimulating factor therapy, although cycling persists. Mutations in neutrophil elastase gene (ELA2) have been found in more than half of patients with CN. However, neither connection between phenotypic expression of ELA2 and CN nor the mechanism of cycling is known.

MATERIALS AND METHODS

Recently, a multicompartment model of haematopoiesis that couples stem cell replication with marrow output has been proposed. In the following, we couple this model of haematopoiesis with a linear feedback mechanism via G-CSF.

RESULTS

We propose that the phenotypic effect of ELA2 mutations leads to reduction in self-renewal of granulocytic progenitors. The body responds by overall relative increase of G-CSF and increasing progenitor cell self-renewal, leading to cell count cycling.

CONCLUSION

The model is compatible with available experimental data and makes testable predictions.

Lessons from congenital neutropenia: 50 years of progress in understanding myelopoiesis

Severe congenital neutropenia (SCN) was first described just over 50 years ago. The progress in elucidating the clinical features and molecular pathophysiology of SCN closely parallels the progressive growth in our understanding of myelopoiesis. In this historical review, I have delineated this parallel progression in our understanding of the processes of granulocyte differentiation and the pathogenesis of congenital neutropenia. SCN is a heterogeneous disease that can serve as a model for the failure of myelopoiesis, and dissection of its pathogenesis has yielded important insights into the normal process of myeloid development.

Granulocyte colony-stimulating factor: molecular mechanisms of action during steady state and 'emergency' hematopoiesis

Neutrophils are phagocytes whose principal function is to maintain anti-bacterial immunity. Neutrophils ingest and kill invading bacteria, releasing cytotoxic, chemotactic and inflammatory mediators at sites of infection. This serves to control the immediate host immune response and attract other cells, such as macrophages and dendritic cells, which are important for establishing long-term adaptive immunity. Neutrophils thus contribute to both the initiation and the maintenance of inflammation at sites of infection. Aberrant neutrophil activity is deleterious; suppressed responses can cause extreme susceptibility to infection while overactivation can lead to excessive inflammation and tissue damage. This review will focus on neutrophil regulation by granulocyte colony-stimulating factor (G-CSF), the principal cytokine controlling neutrophil development and function. The review will emphasize the molecular aspects of G-CSF-driven granulopoiesis in steady state (healthy) conditions and during demand-driven or 'emergency' conditions elicited by infection or clinical administration of G-CSF. Understanding the molecular control of granulopoiesis will aid in the development of new approaches designed to treat disorders of neutrophil production and function.

[Periodic fever syndromes]

Periodic fever syndromes comprise a group of disorders characterized by attacks of seemingly unprovoked inflammation. The genetic causes of five hereditary autoinflammatory syndromes have been identified in the last few years: familial Mediterranean fever, the cryopyrinopathies [Muckle-Wells, chronic infantile neurological, cutaneous, articular syndrome (CINCA) and familial autoinflammatory syndromes], TNF-receptor associated periodic syndrome, cyclic neutropenia syndrome and periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome. The study of periodic fever syndromes has progressed from clinical characterization to genetic analysis and to the definition of the functional defects linking genes or domains to apoptotic proteins and signal transduction pathways. This new research opens the way for more specific treatment options with a further improvement in prognosis and outcome.

Paradoxical drop in circulating neutrophil count following granulocyte-colony stimulating factor and stem cell factor administration in rhesus macaques

OBJECTIVE

Granulocyte colony-stimulating factor (G-CSF) is frequently used therapeutically to treat chronic or transient neutropenia and to mobilize hematopoietic stem cells. Shortly following G-CSF administration, we observed a dramatic transient drop in circulating neutrophil number. This article characterizes this effect in a rhesus macaque animal model.

METHODS

Hematologic changes were monitored following subcutaneous (SQ) administration of G-CSF. G-CSF was administered as a single SQ dose at 10 microg/kg or 50 microg/kg. It was also administered (10 microg/kg) in combination with stem cell factor (SCF; 200 microg/kg) over 5 days. Flow cytometry was performed on serial blood samples to detect changes in cell surface adhesion protein expression.

RESULTS

Neutrophil count dramatically declined 30 minutes after G-CSF administration. This decline was observed whether 10 microg/kg G-CSF was administered in combination with SCF over 5 days, or given as a single 10 microg/kg dose. At a single 50 microg/kg dose, the decline accelerated to 15 minutes. Neutrophil count returned to baseline after 120 minutes and rapidly increased thereafter. An increase in CD11a and CD49d expression coincided with the drop in neutrophil count.

CONCLUSION

A transient paradoxical decline in neutrophil count was observed following administration of G-CSF either alone or in combination with SCF. This decline accelerated with the administration of a higher dose of G-CSF and was associated with an increase in CD11a and CD49d expression. It remains to be determined whether this decline in circulating neutrophils is associated with an increase in endothelial margination and/or entrance into extravascular compartments.

G-CSF treatment of canine cyclical neutropenia: A comprehensive mathematical model

OBJECTIVE

To study the effects of different G-CSF temporal treatment schemes using a comprehensive mathematical model of the mammalian hematopoietic system that couples the pharmacokinetics of granulocyte colony-stimulating factor (G-CSF) to the hematopoietic stem cell, neutrophil, platelet, and erythrocyte dynamics.

MATERIALS AND METHODS

Data from cyclical neutropenic (CN) grey collies are used to build an extended model that reproduces the dynamics of circulating blood cells found in laboratory data from the dogs with and without daily G-CSF therapy. The effects of varying the treatment initiation time, and whether injections are given daily, every other day, or every three days, are examined.

RESULTS

The mathematical model is able to reproduce the large variation in data that occurs from one dog to another. Different drug delivery times, with no other changes in the model parameters, can have significant long-term effects on neutrophil numbers. The frequency of drug delivery also has long-term effects on the oscillations.

CONCLUSION

Using a realistic representation of the effects of G-CSF on the tissue-level hematopoietic system, the model matches a wide range of laboratory data. This implies that it would be possible to generate individualized predictions for specific dogs if data were available in real time. The proposed interventions are practical and may reduce the amount of G-CSF required while potentially maintaining or even improving the treatment effects.

The investigation and management of chronic neutropenia in children

Unravelling the cause of a neutropenia poses a complex diagnostic challenge. The differential diagnosis ranges from life threatening disease to transient benign causes of little clinical significance. This review offers a practical guide to investigating the neutropenic child, and highlights features that merit specialist referral. Therapeutic options, the role of long term follow up, and the complications of severe chronic neutropenia are considered.

Cost-effective G-CSF therapy strategies for cyclical neutropenia: Mathematical modelling based hypotheses

Using computer simulations of a mathematical model for the regulation of stem cell and neutrophil production in dogs, we have studied the efficacy of four different treatment protocols for cyclical neutropenia involving granulocyte colony stimulating factor (G-CSF). The first treatment scheme is based on the bifurcation analysis of the mathematical model and proposes a daily, phase-dependent, protocol. The second involves alternate day administration of G-CSF. The third triggers G-CSF administration whenever neutrophil levels fall below a predetermined level, and the fourth one follows a random administration protocol. The computer simulations predict that clinically desirable results can be achieved with the three last methods, using far less G-CSF than would be needed with the standard daily treatment. If the results of this modelling are borne out clinically, they will entail a considerable financial savings for patients.

Neutropenia: Etiology and Pathogenesis

Neutropenia is defined as an absolute neutrophil count <1500 cells/mm(3) and can be graded as mild (1000-1500 cells/mm(3)), moderate (500-1000 cells/mm(3)), or severe (<500 cells/mm(3)). Neutropenia can develop as a result of > or =1 pathologic mechanism, including decreased bone marrow production, the sequestering of neutrophils, and increased destruction of neutrophils in the peripheral blood. The clinical result is increased risk for infection. This risk is directly proportional to the severity and duration of neutropenia. Neutropenia is classified according to the etiology as congenital or acquired, with the latter further defined according to the etiology or pathology. Febrile neutropenia is associated with substantial morbidity and even mortality.

A mathematical model of hematopoiesis: II. Cyclical neutropenia

Cyclical neutropenia is a dynamical disease of the hematopoietic system marked by an oscillation in circulating leukocyte (e.g. neutrophil) numbers to near zero levels and then back to normal. This oscillation is also mirrored in the platelets and reticulocytes which oscillate with the same period. Cyclical neutropenia has an animal counterpart in the grey collie. Using the mathematical model of the hematopoietic system of Colijn and Mackey [A mathematical model of hematopoiesis: I. Periodic chronic myelogenous leukemia. Companion paper to the present paper.] we have determined what parameters are necessary to mimic laboratory and clinical data on untreated grey collies and humans, and also what changes in these parameters are necessary to fit data during treatment with granulocyte colony stimulating factor (G-CSF). Compared to the normal steady-state values, we found that the major parameter changes that mimic untreated cyclical neutropenia correspond to a decreased amplification (increased apoptosis) within the proliferating neutrophil precursor compartment, and a decrease in the maximal rate of re-entry into the proliferative phase of the stem cell compartment. For the data obtained during G-CSF treatment, good fits were obtained only when parameters were altered that would imply that G-CSF led to higher amplification (lower rate of apoptosis) in the proliferating neutrophil precursors, and a elevated rate of differentiation into the neutrophil line.

Distinguishing among prolonged, recurrent, and periodic fever syndromes: approach of a pediatric infectious diseases subspecialist

Most children with prolonged, recurrent, or periodic fever are healthy and have self-limited, common illnesses, and the primary care practitioner usually can reassure families and continue to reassess the patient as circumstances dictate. For a child with true fever of unknown origin, a pediatric infectious diseases subspecialist should be consulted. This article discusses three objectives for the clinician: (1) to categorize patterns of fever illnesses and prioritize differential diagnoses; (2) to diagnose and manage the most frequently encountered prolonged fever syndrome, deconditioning; and (3) to expand knowledge and approach to diagnosing periodic fever syndromes. The approach described in this article represents the honed, 30-year experience of a pediatric infectious diseases subspecialist.

Thrombopoietic Factors in Chronic Bone Marrow Failure States: The Platelet Problem Revisited: Table 1

Thrombocytopenia is a serious clinical problem in several different clinical settings. In chronic bone marrow failure states, which include aplastic anemia, myelodysplastic syndrome, and graft failure, the prolonged nature of thrombocytopenia often leads to alloimunization after repeated platelet transfusions, the consequence of which is a platelet-refractory state and enhanced risk of bleeding. Despite the introduction of several thrombopoietic factors into clinical trials, an effective way to alleviate thrombocytopenia has been elusive, and the problem in chronic bone marrow failure states has remained poorly addressed by clinical investigations. Even so, several studies by our group and others suggest that a subset of patients suffering from chronic bone marrow failure can respond to appropriate growth factor therapy. The temporal pace of response appears, however, to be much slower than that observed after administering growth factors which act on neutrophils. On the other hand, durable responses can be secured in some patients given thrombopoietic factors for long periods of time. Herein, we provide an overview of the clinical research investigations of thrombopoietic factors in chronic bone marrow failure, and the emerging insights these studies provide for understanding the process of thrombopoiesis and its therapy in this setting.

Sustained elevation of neutrophils in rats induced by lentivirus-mediated G-CSF delivery

BACKGROUND

Patients with severe chronic and cyclic neutropenia, characterized by neutrophil numbers <500 cells/microl, are treated daily with recombinant granulocyte colony-stimulating factor (G-CSF). As an alternative delivery approach we investigated the ability of lentivirus vectors to provide sustained G-CSF expression.

METHODS

Fischer rats were injected intramuscularly (IM) with vesicular stomatitis virus G (VSV-G)-pseudotyped lentivirus pRRL-CMV-G-CSF-SIN that encoded rat G-CSF cDNA regulated by the human cytomegalovirus (CMV) promoter and incorporated a self-inactivating (SIN) construct in the 3' long terminal repeat (LTR). Control rats received normal saline or lentivirus encoding the enhanced green fluorescent protein (eGFP). Rats were serially monitored for blood cell production and tissues assayed for provirus distribution.

RESULTS

Rats receiving a single IM injection of lentivirus exhibited elevated neutrophil counts for 14 months. Virus administration of 6 x 10(7) infectious units induced sustained levels of neutrophil production having a mean +/- standard deviation (SD) of 5650 +/- 900 cells/microl and rats that received a 10-fold lower dose of virus showed mean neutrophil counts of 3340 +/- 740 cells/microl. These were significantly higher than the mean of control animals receiving saline or control lentivirus (1,760 +/- 540 cells/microl, P < 0.0001). White blood cell (WBC) counts were significantly elevated in treated over control animals (P < 0.0001). Hematocrits (P > 0.3), lymphocytes (P > 0.2) and platelets (P > 0.1) were not significantly different between control and treated animals. Genomic DNA from muscle at the injection sites was positive for provirus, whereas lung, spleen, liver, kidney and non-injected muscle samples were all negative, suggesting lack of virus spread.

CONCLUSIONS

These studies indicate that lentivirus vectors administered IM provide sustained, therapeutic levels of neutrophils and suggest this approach to treat patients with severe and cyclic neutropenia.

Stability of a model of human granulopoiesis using continuous maturation

A class of mathematical models involving a convection-reaction partial differential equation (PDE) is introduced with reference to recovering human granulopoiesis after high dose chemotherapy with stem cell support. The stability properties of the model are addressed by means of numerical investigations and analysis. A simplified model with proliferation rate and mobilization rate independent of maturity shows that the model is stable as the maturation rate grows without bounds, but may go through stable and non-stable regimens as the maturation rate varies. It is also shown that the system is stable when parameters are chosen to approximate a real physiological situation. System characteristics do not change profoundly by introduction of a maturity-dependent proliferation and mobilization rate, as is necessary to make the model operate more in accordance with hematological observations. However, by changing the system mitotic responsiveness with respect to changes in cytokine level, the system is still stable but may show persistent oscillations much resembling clinical observations of cyclic neutropenia. Furthermore, in these cases, changes in the model feedback signal caused by, for instance, an impaired effective cytokine elimination by cell receptors may enforce these oscillations markedly.

Treatment of canine cyclic neutropenia by lentivirus-mediated G-CSF delivery

Cyclic neutropenia is a rare disease that occurs both in humans and gray collie dogs and is characterized by recurrent severe neutropenia leading to bacterial infections and shortened life expectancy. Daily injections of recombinant granulocyte colony-stimulating factor (rG-CSF) are effective in shortening the period of severe neutropenia and reducing infections. After demonstrating that rG-CSF induced elevated neutrophil production in an affected dog, cytokine administration was stopped and 109 infectious units (IUs) of a lentivirus pseudotyped with vesicular stomatitis virus G protein (VSV-G) encoding canine G-CSF cDNA was administered intramuscularly. Serial blood cell counts showed elevated neutrophil production for longer than 17 months. Although neutrophil counts continued to cycle, the range at nadirs was from 3710 to 5300 cells/microL, well above the nadirs before lentivirus administration. After the injection of lentivirus, mean neutrophil counts +/- SD were 12 460 +/- 4240 cells/microL, significantly increased over both pretreatment values of 3040 +/- 2540 cells/microL(P <.0001) and neutrophil counts during G-CSF administration of 10 290 +/- 4860 cells/microL(P <.007). The changes in blood counts from lentivirus injection were associated with absence of clinical signs of infection and fever. The gray collie continued to gain weight and was no longer housed in a pathogen-free environment. Genomic DNA from muscle at injection sites was positive for provirus, whereas gonad, lung, spleen, heart, liver, kidney, leukocytes, and noninjected muscle samples were all negative for provirus. Thus, intramuscular administration of lentivirus encoding G-CSF provided sustained therapeutic levels of neutrophils, suggesting this approach may be applied for long-term treatment of patients with cyclic and other neutropenias.

Oscillations in cyclical neutropenia: new evidence based on mathematical modeling

We present a dynamical model of the production and regulation of circulating blood neutrophil number. This model is derived from physiologically relevant features of the hematopoietic system, and is analysed using both analytic and numerical methods. Supercritical Hopf bifurcations and saddle-node bifurcations of limit cycles are shown to exist. We make the estimation of kinetic parameters for dogs and then apply the model to cyclical neutropenia (CN) in the grey collie, a rare disorder in which oscillations in all blood cell counts are found. We conclude that the major cause of the oscillations in CN is an increased rate of apoptosis of neutrophil precursors which leads to a destabilization of the hematopoietic stem cell compartment.

26. Immunomodulation and immunotherapy: drugs, cytokines, cytokine receptors, and antibodies

The preceding chapters in this primer have provided an overview of the immune response that serves as a background for understanding potential sites for immune modulation and immunotherapy. A number of soluble growth and activation factors are released from various cell populations involved in the immune response. They play vital roles in the initiation, propagation, and regulation of immunologic responses. Pharmacologic immunomodulators include suppressive and stimulatory agents. Immunosuppressive therapies include antimetabolites, cytotoxic drugs, radiation, adrenocortical glucocorticosteroids, immunophilins, and therapeutic antibodies. The field of clinical immunostimulation is emerging as an important therapeutic modality for a number of immunodeficiency diseases, chronic viral infections, and cancer. These compounds will be discussed in terms of general principles, molecular targets, major indications, and adverse effects.

Management strategies for HIV-associated aphthous stomatitis

Recurrent aphthous stomatitis (RAS) is the most common oral mucosal disorder found in men and women of all ages, races, and geographic regions. There are three forms of the lesions (minor, major, and herpetiform), with major aphthous ulcers causing significant pain and potential for scarring. In HIV-infected individuals, these ulcers occur more frequently, last longer, and produce more painful symptoms than in immunocompetent persons. In addition, they may be associated with similar ulcerations involving the esophagus, rectum, anus, and genitals. The diagnosis of HIV-induced RAS requires a careful history of the condition, and a thorough extra- and intra-oral examination. Oral mucosal biopsies are required for non-healing ulcers in order to exclude the possibility of deep fungal infections, viral infections, and neoplasms. The cause of the ulcers in HIV-positive persons has not been elucidated--local diseases, genetic, immunologic, and infectious factors all probably play a role. The goals of current treatments are to promote ulcer healing, to reduce ulcer duration and pain while maintaining nutritional intake, and to prevent or diminish the frequency of recurrence. Initial therapy for infrequent RAS recurrences includes over-the-counter topical protective and analgesic products. Initial therapy for frequent RAS outbreaks requires topical anesthetics, binding agents, and corticosteroids. Major RAS and non-healing minor or herpetiform RAS may require intralesional corticosteroids and systemic prednisone. Second-line immunomodulators for frequent and non-healing ulcers includes thalidomide and other immunomodulators.

History of pediatric hematology oncology

Pediatric Hematology Oncology as a specialty was possible because of the evolution of the science of Hematology, which developed microscopy for describing blood cell morphology and methods for quantitation of these elements. Before pediatric blood diseases could be defined, it was necessary to establish the normal blood values of infancy and childhood. The unique features of the blood of the newborn were the focus of many of the early studies. After normal values were established, specific blood disease and hematologic syndromes of children began to be described in Europe and the United States. Pediatric Hematology Oncology is a broad and complex area that encompasses perturbations of the several-formed elements of the blood and their precursors in the bone marrow, as well as the coagulation-fibrinolytic systems in the plasma, the reticuloendothelial system, and malignancies of the blood and solid tissues and organs. The interactions of the blood and nutrition have long been important areas of study. Advances in Pediatric Oncology have been particularly spectacular in the last 50 years. Using multi-modal therapy including combination chemotherapy, more than 80% of children with cancer can now be cured. During the last 50 years, Pediatric Hematology Oncology has increasingly used tools of the "new biology": immunology, biochemistry, enzymology, genetics and molecular genetics, and others. During the last century, many diseases have been recognized and defined by biochemical and genetic mechanisms, and in some instances they have been prevented or cured.