The effect of SARS coronavirus on blood system: its clinical findings and the pathophysiologic hypothesis

Severe acute respiratory syndrome (SARS) has recently recognized as a new human infectious disease. A novel coronavirus was identified as the causative agent of SARS. This report summarizes the hematological findings in SARS patients and proposes a hypothesis for the pathophysiology of SARS coronavirus related abnormal hematopoiesis. Hematological changes in patients with SARS were common and included lymphopenia (68% - 90% of adults; 100% of children, n = 10), thrombocytopenia (20% - 45% of adults, 50% of children), and leukopenia (20% - 34% of adults, 70% of children). The possible mechanisms of this coronavirus on blood system may include (1) directly infect blood cells and bone marrow stromal cells via CD13 or CD66a; and/or (2) induce auto-antibodies and immune complexes to damage these cells. In addition, lung damage in SARS patients may also play a role on inducing thrombocytopenia by (1) increasing the consumption of platelets/megakaryocytes; and/or (2) reducing the production of platelets in the lungs. Since the most common hematological changes in SARS patients were lymphopenia and immunodeficiency. We postulate that hematopoietic growth factors such as G-CSF, by mobilizing endogenous blood stem cells and endogenous cytokines, could become a hematological treatment for SARS patients, which may enhance the immune system against these virus.

Plasmapheresis in immune hematology: review of clinical outcome data with respect to evidence-based medicine and clinical experience

The objective of this paper is to assess the role of plasmapheresis in immune hematology by reviewing published clinical outcome data and narrative review articles. This information will be used to define evidence levels for appraisal of the efficacy and rank of plasmapheresis among other management options. This evidence-based strategy conforms to the concepts of the American Society of Hematology (ASH). as put forward in 1996 in the context of immune thrombocytopenia (ITP) treatment. The term 'experimental' is used to describe indications where the only scientific evidence of the efficacy of plasmapheresis consists of pathophysiological reasoning and empiric clinical findings. We reviewed the available literature on the use of plasmapheresis in autoimmune hemolytic anemia (AIHA), hemolytic disease of the newborn (HDN), autoimmune thrombocytopenic purpura (AITP), heparin-induced thrombocytopenia type II (HIT II), post-transfusion purpura (PTP), refractoriness to platelet transfusion (RPT), coagulation factor inhibitor (CFI) and catastrophic antiphospholipid syndrome (CAS). Plasmapheresis completes the spectrum of management options as it eliminates physically circulating free antibodies involved in the pathogenesis of these immune hematological syndromes. Because of the paucity of data, evidence levels had to be defined based on the findings of uncontrolled case series and the opinions of independent experts. In many cases, randomized clinical trials were not feasible because the syndromes are so rare. When defined as an 'experimental indication', plasmapheresis has a firm scientific basis, but larger scale clinical experience with the method is still lacking. In these cases, the detection and monitoring of symptomatic disease-related circulating free antibodies or immune complexes is a mandatory prerequisite for the use of plasmapheresis. The therapeutic benefit of plasmapheresis is substantiated by the level V of evidence of its efficacy in treatment of HDN, HIV-associated AITP, induction of tolerance in CFI and in CAS. The goal of future studies should be to establish a firmer base of scientific evidence for indications classified as experimental by setting up case series large enough for proper assessment of plasmapheresis alone or combination with other treatment measures. This goal can only be achieved through multiinstitutional cooperation.

Parvovirus B19: a pathogen responsible for more than hematologic disorders

The clinical and pathomorphological patterns of parvovirus B19 (PVB19)-associated diseases is the result of a balance between virus, host target cells and immune response. It is a characteristic feature of PVB19 that in patients with various other preexisting diseases, e.g., many hemolytic anemias, immune complex-mediated vasculitic disorders, and primary or secondary immunodeficiencies, the underlying diseases can be triggered, aggravated or complicated by severe organ manifestations. Identification of PVB19 by means of routine histology and immunohistology is only given in lytic infections occurring in transient aplastic anemia or nonimmune hydrops fetalis by the detection of viral inclusion bodies in erythroid precursor cells. In all other PVB19-associated diseases, molecular pathological methods must be applied. In this report, quantitative real-time polymerase chain reaction was used to determine the viral load in formalin-fixed and paraffin-embedded tissues derived from various organs. Using in situ hybridization it was demonstrated that endothelial cells of the microcirculatory periphery of the heart and hepatobiliar system in lytic infections are PVB19-specific target cells in children and adults. Because treatment of lytic PVB19 infection has been successfully applied, the pathologist should be alerted to include PVB19 into the diagnostic spectrum of viral disease, especially in immunocompromised patients.

Hyperviscosity Syndrome in Cryoglobulinemia: Clinical Aspects and Therapeutic Considerations

The term cryoglobulinemia refers to the presence in the serum of proteins that precipitate at temperatures below 37 degrees C and redissolve on rewarming. The cryoglobulins can be divided into three categories: monoclonal, mixed, and polyclonal. Hyperviscosity syndrome is much more common in monoclonal than in mixed or polyclonal cryoglobulinemia. The clinical manifestations of cryoglobulinemia depend on the underlying disease and may involve various organs or systems. Mixed cryoglobulinemia (MC) is dominated by a vasculitic process, and the clinical manifestations can range from mild to life threatening in their severity. Another common feature of this disorder is the presence of a benign smoldering lymphoproliferative process that can evolve (in a limited number of cases) into non-Hodgkin's lymphoma. The elective treatment for hyperviscosity syndrome, whether associated with monoclonal, mixed, or polyclonal cryoglobulinemia, is plasma exchange. In monoclonal cryoglobulinemia, this procedure seems to act by removing large amounts of abnormal proteins, but its mechanism in MC is far from clear. Here it is possible that qualitative and quantitative variations in the circulating cryoglobulins, as well as hemodynamic changes, are at play. This article will focus on the hyperviscosity syndrome in cryoglobulinemia, beginning with a discussion of its clinical features and then examining the role of hemorheological parameters in the condition.

Long-term follow-up of chimerical state of the patients transplanted for different haematologic diseases

Long-term follow-up of peripheral cellular chimerism in patients treated with BMT or PBSCT revealed the usefulness of their continuous monitoring at molecular level. Our results are based on monitoring of 120 patients, who were followed for at least 24 months. Comparison of the patients treated for chronic myelogenous leukemia (CML), acute myelocytic leukemia (AML), acute lymphocytic leukemia (ALL), myelodysplastic syndromes (MDS) and aplastic anaemia (AA) revealed that mixed chimerism was practically absent in MDS and relatively long-lasting in ALL and AA (regardless to substantially different post-transplantation treatment). The first disease relapses signalized by molecular checking of mixed peripheral chimerism were observed also after a period of remission lasting for several years. Molecular watching enables us to detect relapses at their very beginning that would remain hidden to less sensitive methods. We believe that all of the transplanted patients ought to be monitored for residual disease i.e. cellular chimerism using molecular methods without time limits. On the other hand low level of mixed cellular chimerism is not necessarily a sign of disease progression and can remain unchanged as "status quo" for a very long period.

CAMPATH-1H in the treatment of autoimmune cytopenias

BACKGROUND

The autoimmune cytopenias encompass the disorders of immune thrombocytopenia purpura (ITP), pure red-cell aplasia (PRCA), autoimmune hemolytic anemia (AIHA), autoimmune neutropenia and various combinations of these conditions. T lymphocytes are thought to play an important role in the pathogenesis of autoimmune cytopenias, and the presence of autoantibody may represent an epiphenomenon, rather than the primary pathogenetic mechanism. The majority of patients usually respond to standard immunosuppressive therapy and can mostly be treated as out-patients. A small proportion, however, have severe, resistant and life-threatening disease, or may experience major morbidity from side effects of drugs given to treat their disease.

METHODS

We have treated 21 patients with autoimmune cytopenias with the MAb Campath-1H, and for later patients in this series, in combination with low dose CYA.

RESULTS

Responses were seen in 14 of 20 evaluable patients, although relapse occurred in seven patients. In many patients corticosteroid therapy could be discontinued or greatly reduced.

DISCUSSION

We conclude that Campath-1H can induce remissions in autoimmune cytopenias and we critically review its role in the treatment of these disorders.

An association between human leucocyte antigen alleles and acute and chronic graft-versus-host disease after allogeneic haematopoietic stem cell transplantation

The association between various human leucocyte antigen (HLA) alleles and the occurrence of acute and chronic graft-versus-host disease (GVHD) was evaluated in 493 haematopoietic stem-cell transplant (HSCT) patients with HLA identical sibling donors. There were 307 men and 186 women with a median age of 30 years (0.2-77). Most of the patients had a haematological malignancy and received total body irradiation or busulphan combined with cyclophosphamide as conditioning before transplantation. GVHD prophylaxis consisted of monotherapy with methotrexate (MTX) or cyclosporin (CsA) in 118 patients, MTX + CsA in 323, T-cell depletion in 28 and other combinations in 24. In total, 84 patients (17%) received a peripheral blood stem-cell graft, whereas the rest received bone marrow. The cumulative incidence of acute GVHD grades II-IV was 20%, and chronic GVHD 46%. In the multivariate analysis, HLA-A10 (OR 2.14, CI 1.04-4.41, P = 0.03) and HLA-B7 (OR 1.80, CI 1.04-3.12, P = 0.03) correlated with an increased risk of acute GVHD grades II-IV. We also found an association between HLA-B27 (RR 0.60, CI 0.37-0.95, P = 0.04) and a lower incidence of chronic GVHD. These HLA alleles were independent of other known risk factors for acute or chronic GVHD, as shown by multivariate analysis. These results show that major histocompatibility comlex (MHC) alleles may influence the incidence of GVHD in HSCT with HLA identical sibling donors.

Cell surface antigen and molecular targeting in the treatment of hematologic malignancies

Conventional cytotoxic therapy of hematologic malignancies is often associated with significant morbidity. This morbidity is often due to the lack of specificity for hematopoietic cells. Therefore, the concept of targeted therapy for patients with hematologic malignancies has received attention for many years. The goal of monoclonal antibody therapy is to target specific cell surface antigens on malignant hematopoietic cells, while sparing normal cells and tissues. Currently, monoclonal antibodies are being evaluated for their cytotoxic effects as well as their ability to deliver toxic agents or radiation. Rituximab, a chimeric anti-CD20 antibody, has shown response rates of approximately 50% with minimal toxicity in patients with refractory indolent lymphoma. Campath-1H (anti-CD52) has shown encouraging results in patients previously treated for chronic lymphocytic leukemia, with response rates up to 33%, although with significant toxicity. Anti-CD33 antibodies are being used to deliver cytotoxic agents, such as calicheamicin to patients with acute myeloid leukemia with response rates up to 30%. In addition, anti-CD33 and anti-CD45 antibodies have been used to deliver radiation directly to leukemic cells. (131)I-labeled anti-CD45 antibodies are being studied in combination with conventional preparative regimens in patients receiving bone marrow transplantation. Lastly, the therapeutic agent STI571 (signal transduction inhibitor 571) has demonstrated the capability of targeting specific molecular abnormalities seen in hematologic malignancies. STI571 targets the tyrosine kinase activity of the bcr-abl fusion protein seen in chronic myeloid leukemia. STI571 has induced complete hematologic responses in up to 98% of patients evaluated in clinical trials.

Dendritic cell recovery following nonmyeloablative allogeneic stem cell transplants

Nonmyeloablative allogeneic stem cell transplantation (NMSCT) may destroy some malignancies through a graft-versus-tumor (GVT) effect, but tumor relapse and viral reactivation remain challenges for which immunizations may be helpful. Dendritic cells (DC), particularly DC1 and ex vivo-cultured DC, induce antigen-specific immune responses following viral infections and anti-tumor immunizations. DC2 may be tolerogenic. We hypothesize that successful immunizations following NMSCT will require adequate numbers of functional DC1 or ex vivo-generated DC. We determined the number, phenotype, and function of blood DC1 and DC2 and ex vivo-generated DC obtained from donor-recipient pairs before and up to 90 days after NMSCT. Although the percentage and number of recipient blood Lin(-) HLA-DR(+) CD11c(+) DC1 following NMSCT (median 0.46%, IQR 0.33-0.52%) was lower than donor DC1 (median 0.94%, IQR 0.40-2.2%) this was not significant. In contrast, the percentage and absolute number of blood Lin(-) HLA-DR(+) CD11c(-) CD123(+) DC2 was significantly decreased following the transplant (median 0.01% IQR 0.01-0.01% at day 60 compared with median 0.14%, IQR 0.10-0.38% for the donor before transplantation, p < 0.05). The yield (median 6.0%, IQR 5.5-8.5%) and allostimulatory function of ex vivo-generated DC did not differ significantly at any time point. The donor chimerism of blood and cultured DC reflected that of the overall white blood cells. Ex vivo-generated, donor DC loaded with cytomegalovirus (CMV) antigens were capable of stimulating a CMV-specific immune response in vitro within peripheral blood mononuclear cells of a patient following NMSCT. We conclude that blood DC numbers may be diminished following NMSCT transplant, but that DC1 recovery exceeds DC2 and functional DC may be generated from peripheral blood progenitors at all time points suggesting a possible use in immunization strategies.

B lymphocyte stimulator (BLyS): a therapeutic trichotomy for the treatment of B lymphocyte diseases

B Lymphocyte Stimulator (BLyS protein) is a member of the tumor necrosis factor (TNF) family of ligands and functions as an essential in vivo regulator of B lymphocyte homeostasis. As such, changes in systemic BlyS protein expression caused by disruption of the gene encoding BLyS or administration of neutralizing soluble receptors have resulted in profound losses in mature B cell numbers and impaired humoral immunity. A similar phenotype has been observed in A/WySnJ mice that express a truncated BLyS receptor and are thus defective in BLyS signal transduction. In contrast, overexpression of BLyS protein in BLyS-transgenic mice results in B cell hyperplasia, hypergammaglobulinemia, and development of autoimmune-like disease. The ability of BLyS to regulate both the size and repertoire of the peripheral B cell compartment raises the possibility that BLyS and antagonists thereof may form the basis of a therapeutic trichotomy. As an agonist, BLyS protein may enhance humoral immunity in congenital or acquired immunodeficiencies such as those resulting from viral infection or cancer therapy. BLyS-specific antagonists (antibodies or soluble receptors) that inhibit the biological activity of BLyS may be effective therapies for those autoimmune diseases characterized by polyclonal hypergammaglobulinemia and elevated autoantibody titers. Finally, the specificity of BLyS for B-lineage cells raises the possibility that BLyS may be used as a targeting vehicle for delivery of a cytotoxic or cytolytic signal to neoplastic B-lineage cells expressing one or more of the three known BLyS receptors. This review discusses the therapeutic potential of BLyS in the context of BLyS structure, function and receptor specificity.

Immune-mediated complications during interferon therapy in hematological patients

Interferon (IFN), a leukocyte-derived cytokine, has been used to treat several hematological malignancies. The most common adverse effects of IFN are flu-like symptoms. Autoimmune side effects are infrequent but may be hazardous and irreversible. These may occur in several ways: autoantibodies may either appear during the treatment or existing titers may rise, subclinical autoimmune phenomena may become clinically manifest or autoimmune diseases may appear de novo. The main categories of IFN immune-mediated side effects are: thyroid, hematological, connective tissue, renal and miscellaneous disorders. The most common ones are thyroid disorders, which manifest either as hypo- or hyperthyroidism. Patients with pre-existing autoantibodies are more susceptible to the exacerbation of thyroid autoimmunity, probably since IFN enhances the levels of autoimmunity. Hematological disorders include autoimmune anemia and thrombocytopenia and thrombotic thrombocytopenic purpura. The immunological derangement of autoimmune hemolytic anemia manifests as enhanced destruction of antibody-coated red blood cells and induction of autoreactive B cells secreting these antibodies. Although autoimmune thrombocytopenia is rare, a sharp reduction in the platelet counts, beyond that expected from the antiproliferative effects of IFN, should raise this possibility. Thrombotic thrombocytopenic purpura has recently been included among the autoimmune disorders. Sporadic cases have been reported in association with IFN treatment. The clinical spectrum of IFN-induced connective tissue disorders ranges from typical systemic lupus erythematosus to seropositive or seronegative rheumatoid arthritis. Some authors also reported on the development of Behçet's disease in chronic myeloid leukemia patients treated with IFN. The underlying reason for the skin hyperreactivity in Behçet's disease and the effect of IFN treatment in these patients may be altered neutrophil activity in both disorders. Several series evaluated the incidence of Raynaud's phenomenon in patients treated with IFN for hematological disorders. Some of them reported on a rather high incidence of nailfold capillary microscopy abnormalities with or without Raynaud's phenomenon. Whether IFN-induced Raynaud's phenomenon is immune-mediated or directly caused vasospasm, is still unknown although the occurrence of several autoantibodies suggests an immune mechanism. Adverse effects of IFN therapy on the kidney include proteinuria and rarely nephrotic syndrome or acute and chronic renal failure. The mechanism of renal injury is unclear although an immune mechanism is suggested. Sporadic cases of other immune-mediated side effects have been published. These include dermatological adverse effects manifesting as psoriasis, pemphigus and vitiligo, and also rare cases of sarcoidosis, hepatitis, colitis or cryoglobulinemia. In conclusion, patients treated with IFN should be monitored for symptoms of autoimmunity. Patients with previous autoimmune phenomena should be treated, if possible, with alternative drugs since there is risk of exacerbation of these manifestations in these patients.

Impact of hepatitis B and hepatitis C virus infections in a hematology-oncology unit at a children's hospital in Nicaragua, 1997 to 1999

The risk of acquiring both hepatitis B virus (HBV) and hepatitis C virus (HCV) infections in patients with hematological-oncological disorders has been documented. However, the impact and risk factors for such infections from different geographical areas vary, and the use of both immunological and molecular assays to determine HCV infections has been our approach. Children from a hematology-oncology unit (HOU) in Nicaragua were studied for both HBV and HCV serological markers; studies for the latter used both immunological (anti-HCV) and molecular (HCV RNA) assays. The children from the HOU included patients with leukemia, lymphoma, other neoplasias, and anemia and a smaller group with other hematological diseases. As a control group, children from other units at the same hospital were enrolled, as well as health care workers attending both patient populations. Pertinent clinical and personal data for each child at the HOU were obtained for statistical analysis. Of the 625 children from the HOU enrolled in this study 53.3% were infected with HCV and 29.4% had a prior or present HBV infection. In the child patient control group 3.2% had HBV markers and all were negative for HCV. The group of children with leukemia had the highest infection rate for both HBV and HCV. However, the determination of anti-HCV was found to have an overall low sensitivity in children from HOU, and a retest consisting of a molecular assay to determine HCV RNA was performed to better establish the total number of HCV-infected subjects in this group. The highest independent risk factor for infection was hospitalization. The very high prevalence rates for both HBV and HCV infection in this patient group indicate an urgent need to implement better control of known risk factors and to consider the use of both immunological and molecular assays for HCV diagnostic purposes.

Surveillance study of bacteraemic episodes in febrile neutropenic children

We prospectively studied the type, frequency and outcome of infections in 513 patients with 762 consecutive episodes of febrile neutropenia (FN) over a five-year period between 1995 and 1999 in a single paediatric oncology unit. The findings were then compared with a similar study carried out in our unit between 1990 and 1994. The types of bacterial isolates and sensitivity patterns were also studied to identify trends and to gauge the suitability of antibiotics chosen for empirical therapy. Bacteraemia was documented in 35.4% of FN episodes, although 70% of patients did not have an obvious site of sepsis. The majority of isolates (61.9%) were gram-negative bacteria, a consistent finding throughout the study period. Resistance to ceftazidime, amikacin and imipenem among gram-negative bacteria was 26.3%, 21.2% and 0.7%, respectively. Methicillin resistance among gram-positive bacteria was 26.3%, while no vancomycin-resistant bacteria were encountered. There were 36 sepsis-related deaths. Factors associated with a fatal outome were prolonged capillary refill time, hypotension, fever above 39 degrees C and pneumonia. Rapid neutrophil recovery was associated with a good prognosis. A change to our current choice of empirical antibiotics for FN, comprising ceftazidime/ceftriaxone and amikacin appears necessary because of the relatively high resistance rates found.

Hematologic complications of primary immune deficiencies

Primary immune deficiencies have an estimated overall incidence of 1 in 10,000 individuals. These disorders are diverse, depending on the specific immune functions involved, and lead to chronic or recurrent infections, inflammatory conditions, and a variety of autoimmune diseases. The most common autoimmune disorder is immune thrombocytopenic purpura (ITP), followed by autoimmune hemolytic anemia (AHA). While cytopenias are common in all the congenital immune diseases, they are particularly common in the antibody defects, common variable immunodeficiency and selective immunoglobulin A deficiency. In common variable immunodeficiency, ITP occurred in 7.6% of the patients and AHA in 4.8%. Treatment options include corticosteroids, intravenous immunoglobulin (i.v.Ig), anti-D, and splenectomy. Although the association between cytopenias and congenital immune deficiency is unclear, defects in T-cell regulation, cytokine defects, abnormal apoptosis, and abnormal production of immunoglobulins with autoimmune features are potential mechanisms.

[New perspectives in immuno-mediated blood diseases]

Immune-mediated blood diseases are organ-specific autoimmune disorders where one or more blood cell lineages are the target of the autoimmune process. They are classically divided into peripheral immune-mediated blood diseases when the immune attack occurs outside the bone marrow and autoimmune myelopathies. Overall they are the prototype of diseases that bridge immunology and hematology including blood malignancies. They also provide a fertile ground for new modalities of immunosuppression. The investigations of platelet autoimmunity as a model of peripheral immune-mediated blood diseases have confirmed that platelet disorders hover between hemorrhage and thrombosis and have led to develop the concept of autoimmune thrombophilia.

Genotypes of clustered cases of Pneumocystis carinii pneumonia

Reports of outbreaks of Pneumocystis carinii pneumonia (PCP) among human immunodeficiency virus-negative immunocompromised patients have suggested a person-to-person transmission of P. carinii. In this study, 17 bronchoalveolar lavage isolates from patients in 3 PCP outbreaks were genotyped, 2 in renal transplant recipients and 1 outbreak among patients with haematological disorders. Genotypes in the P. carinii sp. f. hominis (P. carinii f.sp. hominis) mt large subunit ribosomal RNA site 85 were detected by 2 methods: direct sequencing and 3 different allele-specific polymerase chain reaction assays. Although limited data on patient contacts were available, the detected P. c. hominis genotypes do not support person-to-person transmission as the predominant transmission route of P. carinii in humans.