Clinical hematopoietic stem cell (HSC) transplantation is associated with high toxicity due to the so-called “conditioning regimen”, which is aimed at depleting host immune and hematopoietic cells in order to achieve significant engraftment of donor cells. The standard conditioning includes chemotherapy and total body irradiation (TBI). Furthermore, after engraftment, donor cells can provoke severe alloimmune reaction against residual host cells - graft-versus-host-disease (GVHD), associated with high mortality.

This outcome generates much risk of morbidity and mortality for the recipient. Therefore risk of transplantation is weighed against risk of disease in decision algorithms. The difficulty is that although HSCT might be the most secure way to be alive in three decades, it is also the most likely way of being dead in 3 months.

There are many ongoing clinical trials, aimed to reduce intensity (which is equal to reduced toxicity) of conditioning and in the same time retain optimal engraftment of donor’s HSC. One of the most promising approaches is depletion of recipient’s bone marrow cells by antibodies against surface antigens. I wrote about one experimental study, showed the proof-of-principal of “making more bone marrow niches available for donor’s HSC”.

Now we have the first clinical report about the possibility of minimization of conditioning regimen toxicity by antibody-based clearance of host immune and hematopoietic cells.

In the protocol, published in the Lancet journal, TBI and standard chemotherapeutic doses were replaced by monoclonal antibodies - CD45 and CD52, in 16 high-risk children with primary immunodeficiency. High risk mean that these children are not going to survive without bone marrow transplant, but they are so weak that will not able to resist toxic conditioning treatment. This approach called “minimal-intensity conditioning” (MIC). Anti-CD45 antibody was used for myelosupression, anti-CD52 - for immunosupression.

Our study provides a novel approach for allogeneic stem-cell transplantation and represents a shift from the paradigm that intensive chemotherapy or radiotherapy, or both, with a stem-cell agent is needed to secure engraftment of donor haemopoietic stem cells. This novel conditioning regimen enables successful transplantation in patients who would not previously be eligible for stem-cell transplantation with presently available regimens, and might thus extend the benefits of such transplantation to virtually all those with primary immunodeficiency.

2 important conclusions were made by the authors: first - the engraftment level achieved in the study is similar to those children which underwent reduced-intensity conditioning; the second - relatively low and comparable (to conventional and reduced-intensity conditioning regimens) level of GVHD as complication of MIC was observed.

This trial is remarkable! It’s a proof-of-principal study showed that monoclonal antibody can be used for depletion host marrow hematopoietic cells, reduce toxicity and pretransplant comorbidity in non-malignant disease. It brings us a hope to treat more patients with non-malignant disorders, such as immunodeficiency, metabolic defects and maybe autoimmune diseases.

You can see the evolution of conditioning regimens in scheme below:

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Lancet 2009;374;912
Citation from: Lancet 2009;374;856

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Connotea tag: clinical trial

 

Introduction

Background

Common variable immunodeficiency (CVID) is one of the most prevalent primary immunodeficiency diseases. Common variable immunodeficiency is a heterogeneous group of immunologic disorders of unknown etiology, characterized by impaired antibody responses. Patients with common variable immunodeficiency have marked reduction in serum levels of both immunoglobulin G (IgG) and immunoglobulin A (IgA); about half of these patients also have reduced immunoglobulin M (IgM). Diagnosis is based on exclusion of known causes of humoral immune system defects.

Most patients with common variable immunodeficiency present as sporadic cases, although familiar cases with various inheritance modes have been reported, including autosomal dominant with variable penetrance, autosomal recessive, or X-linked.

Pathophysiology

The common immunologic defect in patients with common variable immunodeficiency is defective antibody formation. As is expected in a heterogeneous group of diseases, many different immune system defects have been reported in this group of patients.

B-cell defect

The basic and common immunologic defect in common variable immunodeficiency is a failure of B-lymphocyte differentiation into plasma cells that produce the various immunoglobulin (Ig) isotypes. Earlier studies suggested a primary B-lymphocyte defect as a cause of common variable immunodeficiency in a small group of patients. B lymphocytes from these patients failed to differentiate into Ig-producing cells when stimulated with pokeweed mitogen (PWM) in vitro, even when cocultured with normal T cells; they were also L-selectin negative. These studies described failure of B-cell differentiation because of altered B-cell surface–molecule expression.

Primary B-cell dysfunction secondary to newly discovered genetic defects has been described in a small number of patients with common variable immunodeficiency (see Causes). These include CD19 deficiency and mutations in the genes that encode TACI (the transmembrane activator and calcium-modulating cyclophilin ligand interactor, TNFRSF13B), ICOS (the inducible costimulator of activated T cells), and BAFFR (the B-cell activating factor of the tumor necrosis factor [TNF] family receptor, TNFRSF13C). CD19 plays a crucial role in regulating B-cell responses to antigens and B-cell survival.

TACI is one of the TNF receptor superfamily members. TACI plays an indispensable role in isotype switching, terminal differentiation of B cells, and T-cell–independent antibody responses. TACI mutations that lead to immunodeficiency account for an estimated 10-15% of patients with common variable immunodeficiency. ICOS mutation is associated with absent ICOS expression on the surface of activated T cells and results in reduced class-switched memory B cells. The BAFFR defect is also associated with reduced class-switched and nonswitched memory B cells.

B cells develop in bone marrow from pluripotent hemopoeitic stem cells through rearrangement of immunoglobulin heavy-chain and light-chain genes and initial positive and negative selection in the bone marrow. Mature B cells expressing both IgM and IgD leave bone marrow and enter secondary lymphoid organs. Within the secondary lymphoid follicles, affinity maturation and class switching take place through somatic hypermutation of the variable region genes and class-switch recombination. These B cells become either memory B cells or long-lived plasma cells that home back to the bone marrow and produce high-affinity antibodies.

Enumeration of the B-cell subsets in peripheral blood may be useful in classifying of common variable immunodeficiency. These subsets include class-switched memory B cells (CD27+IgD-IgM-), nonswitched memory B cells (CD27+IgD+IgM+), IgM memory B cells (CD27+IgM+IgDdim), transitional B cells (CD38+++IgM+++), plasmablasts (CD38+++IgM-), mature B cells (CD19+CD21+), and CD21lo B cells (CD19+CD21lo).

Several groups have reported classification of common variable immunodeficiency based on B-cell subtype using flow-cytometry techniques. Paris1 and Freiburg2 classifications are based on the presence or absence of class-switched memory B cells. A EUROclass trial unified the 2 classifications and attempted to provide clinical links with B-cell subset phenotypes and clinical manifestations.3 The data included 303 patients with common variable immunodeficiency and suggested that severe reduction in the number of class-switched memory B cells is associated with granulomatous disease, splenomegaly, and autoimmune cytopenias.

Other studies have observed a lack of protein kinase C activation and translocation to the plasma membrane when B cells of patients with common variable immunodeficiency were stimulated with phorbol ester or anti-µ antibody. B-cell lines from a subset of patients with common variable immunodeficiency displayed absent IgG and IgA production and increased spontaneous apoptosis that was associated with increased expression of CD95 (APO-1/Fas).

A subset of patients with common variable immunodeficiency displayed impaired B-cell signal transduction cascade associated with abnormalities in protein tyrosine phosphorylation. Another subset exhibited chromosomal radiosensitivity, presumably due to impaired ability to repair DNA.

Mutations interfering with the regulation of the Ig gene expression, deficiency of memory B cells, and somatic hypermutation (SHM) abnormalities have been reported in patients with common variable immunodeficiency. Memory B cells develop in the germinal centers where SHMs are introduced, followed by antigen-mediated selection of cells with high affinity for the antigen. Low level of SHM, which correlated with increased frequency of severe respiratory tract infection, has been reported in patients with common variable immunodeficiency. B cells from these patients were unable to undergo isotype switching and were unable to upregulate activation markers on B cells when stimulated in vitro.

Others reported that loss of IgM memory B cells correlates with clinical features of recurrent pneumonia caused by encapsulated microbes and bronchiectasis in common variable immunodeficiency.

T-cell defect

An overwhelming body of literature suggests that most patients with common variable immunodeficiency have intact B lymphocytes of immature phenotype. Common variable immunodeficiency B cells can secrete immunoglobulins (Ig), although often limited to IgM, if given the appropriate in vitro stimulation. Ig secretion has been induced from common variable immunodeficiency B cells using B-cell mitogens with soluble T-cell factors, monoclonal B-cell differentiation factors, Epstein-Barr virus (EBV), anti-CD40 plus interleukin (IL)-4 and IL-10. CD40 ligand (CD154) is expressed by activated CD4+ cells and is pivotal in inducing B-cell proliferation and differentiation.

Approximately 40% of patients with common variable immunodeficiency have low expression of CD40 ligand on activated T cells. At least 30% of patients with common variable immunodeficiency have lymphopenia due to the low number of CD4+ subsets. These patients also have decreased in vitro production of IL-2 when their peripheral blood mononuclear cells are stimulated in vitro. Decreased IL-2 production with stimuli via T-cell receptors is correlated with diminished CD40 ligand expression. Reduced expression of ICOS was reported in some families with autosomal recessive common variable immunodeficiency due to homozygous mutations in the ICOS gene. ICOS deficiency results in severe B-cell defect, which is caused by impaired T-cell help.

T cells in patients with common variable immunodeficiency have low frequency of antigen-specific precursor T cells following immunization with the neoantigens keyhole-limpet hemocyanin and dinitrophenol (DNP)-Ficoll. Many patients with common variable immunodeficiency have a defect in CD4+ T-cell priming to antigens, as measured by the number of circulating responsive CD4+ T cells following immunization. Many patients have a reduction in CD4+ CD45RA+ (“unprimed”) T cells, suggesting activation of T cells.

Most patients with common variable immunodeficiency reportedly have increased production of interferon gamma by circulating CD8+ subsets, increased numbers of DR+/CD4+ T cells with up-regulated Fas expression, and an increased apoptosis. The abnormality appears to reside in CD4+ T cells and can be overcome by stimulating T cells with phorbol myristate acetate (PMA) and ionomycin, an alternative T-cell activation pathway. This is consistent with defective signal transduction in T cells.

Increased endogenous cyclic adenosine monophosphate (cAMP) levels in T cells from patients with common variable immunodeficiency are associated with increased activation of protein kinase A type I (PKAI) in T cells and with decreased proliferative response to anti-CD3. A selective antagonist of PKAI induces a significant increase in anti-CD3-stimulated proliferative responses, particularly in CD4+ lymphocytes. Approximately 25-30% of patients with common variable immunodeficiency have increased numbers of CD8+ lymphocytes, normal or decreased CD4+, and reduced CD4/CD8 ratios (<1). This increase in CD8+ T cells has been observed most often in patients with splenomegaly and bronchiectasis. These cells coexpress human leukocyte antigen (HLA)-DR and IL-2 receptors, suggesting in vivo activation.

Approximately 60% of patients with common variable immunodeficiency have diminished proliferative responses to T-cell receptor stimuli and decreased induction of gene expression for IL-2, IL-4, IL-5, and interferon gamma. T-cell receptors of patients with common variable immunodeficiency have no evident abnormality; T-cell receptor gene analyses indicate normal heterogeneity of gene rearrangements. TNF production from T cells and monocytes is increased in a subgroup of patients with granulomatous diseases. Standard tests to assess T-cell function, including in vitro proliferation in response to mitogens, antigens, and allogeneic cells, are subnormal in as many as 50% of patients with common variable immunodeficiency with a small subgroup of patients having very low responses. These results support the hypothesis that most patients with common variable immunodeficiency have antibody deficiency secondary to abnormalities in T-cell signaling and defective T-cell and B-cell interactions.

The recovery of Ig production (mostly IgG and IgM) transiently or permanently following human immunodeficiency virus (HIV) or hepatitis C virus (HCV) infection has been reported in patients with common variable immunodeficiency. These cases indicate that common variable immunodeficiency is associated with potentially reversible defects in immunoregulatory factors and intact B-cell systems.

Other defects

A decrease in the number of peripheral blood dendritic cells (DCs) was noted in patients with common variable immunodeficiency. Low numbers of DCs correlated with a greater incidence of autoimmunity, splenomegaly, and granulomatous disease and a higher incidence of clinical complications. DCs play a role in B-cell growth and differentiation of plasma cells into immunoglobulin-secreting plasma cells. Others reported defective functions of DCs in patients with common variable immunodeficiency, inducing weak proliferation of allogeneic T cells and producing significantly low amounts of interleukin 12 upon CD40 signaling.

Increased functional capacity in both classic and alternative complement pathways in patients with common variable immunodeficiency was noted. Many patients with common variable immunodeficiency with increased levels of complement split products, presumably from complement activation, had autoimmune manifestations. Others reported a strong inverse correlation between mannose-binding lectin levels and the frequency of lower respiratory tract infection and bronchiectasis in patients with common variable immunodeficiency.

 

Frequency

United States

Estimated incidence of common variable immunodeficiency is 1 case per 10,000-50,000 population.

International

Incidence is similar to that in the United States.

Mortality/Morbidity

The prognosis for patients with common variable immunodeficiency is reasonably good if they do not have bronchiectasis and chronic lung damage or severe autoimmune disease or malignancy.

• In one large series, the most frequent cause of death was lymphoma. Other causes of death include cor pulmonale from chronic pulmonary infection, liver failure caused by viral or autoimmune hepatitis, respiratory insufficiency associated with malnutrition,

Race

Common variable immunodeficiency has been reported in many different races.

Sex

Common variable immunodeficiency equally affects males and females.

Age

Although the usual age at presentation is in the second or third decades of life according to some reports, other reports described the onset of clinical disease as early as the first decade of life, with peaks of onset in children aged 1-5 years and in persons aged 16-20 years. Likewise, age of diagnosis demonstrated bimodal peaks at 6-10 years and 26-30 years. More than two thirds of the patients were adults who were older than 21 years at the time of initial diagnosis.

Clinical

History

Clinical manifestations of common variable immunodeficiency (CVID) include recurrent infections, autoimmune disease, lymphoid hyperplasia, granulomatous diseases, and malignancy.

• Recurrent infections
  • Recurrent pyogenic infections of upper and lower respiratory tracts are the main clinical manifestations of common variable immunodeficiency. Symptoms may appear during childhood or, more often, after puberty. Bronchiectasis may develop if optimal therapy is delayed. Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, and Staphylococcus aureus are the organisms most commonly involved.
  • A few patients with common variable immunodeficiency present with unusual organisms, such as Pneumocystis carinii, mycobacteria, or various fungi. Mycoplasma pneumoniae infections in the urinary tract, joints, and deep abscesses have been reported.
  • Persistent diarrhea and malabsorption caused by Giardia lamblia also have been reported in patients with common variable immunodeficiency. GI symptoms disappeared after G lamblia was eradicated with metronidazole.
  • Severe and recurrent infections with herpes simplex are common, and herpes zoster eventually develops in as many as 20% of patients with common variable immunodeficiency.
  • Some patients may develop unusual enteroviral infections with a chronic meningoencephalitis and a dermatomyositislike illness. Presenting symptoms are either acute or insidious, with signs of encephalitis, seizures, headache, sensory motor disturbances, and personality changes.
  • Vaccine-associated paralytic poliomyelitis (VAPP) in a patient with common variable immunodeficiency has been reported; this patient developed paralytic poliomyelitis 7 years after the last administration of trivalent oral poliovirus vaccine.
  • The best indicator for susceptibility to pneumonia and severe infections was a reduced baseline serum immunoglobulin (Ig)G.
• Autoimmune diseases and common variable immunodeficiency
  • In contrast to X-linked agammaglobulinemia (XLA), common variable immunodeficiency is associated with a high frequency of autoimmune and granulomatous diseases.
  • Some patients develop rheumatoid arthritis, hemolytic anemia, thrombocytopenia, neutropenia, thyroid abnormalities, vitiligo, or keratoconjunctivitis sicca.
  • Approximately 20% of these patients have a severe gastroenteropathy with severe malabsorption resembling celiac sprue, nodular lymphoid hyperplasia, and chronic inflammatory bowel disease such as ulcerative colitis and Crohn disease.
  • A small number of patients develop achlorhydria and pernicious anemia, autoimmune hepatitis, primary biliary cirrhosis, alopecia totalis, hyperthyroidism, vasculitis, and lymphoid interstitial pneumonia.
  • Although regular Ig replacement therapy reduces susceptibility to Giardia species and Campylobacter enteritis, it does not prevent autoimmune mucosal inflammation. Ig replacement therapy does not affect the clinical course of inflammatory bowel disease.
• Lymphoid hyperplasia and granulomatous diseases
  • Atypical lymphoid hyperplasia due to clonal expansion of B or T lymphocytes has been reported in as many as one third of patients with common variable immunodeficiency. Extranodal sites, such as the lungs, GI tract, skin, spleen, liver, and parotid gland, may be involved by these lymphoproliferative processes. Lymph nodes show a reactive follicular hyperplasia, atypical hyperplasia, or granulomatous inflammation. Nodular lymphoid hyperplasia in the GI tract with clonal rearrangement of the Ig heavy chain gene or clonal T-cell receptor (TCR) gene rearrangement has been described in otherwise benign cases of lymphoid proliferation in patients with common variable immunodeficiency.
  • Granulomas have been reported in approximately 8-22% of patients with common variable immunodeficiency. These patients were more likely to have deficient T-cell proliferation to mitogens and antigens. Previous studies have reported 22 common variable immunodeficiency patients with sarcoidosis. Granulomas are indistinguishable from those of classic sarcoidosis and are found in the lungs, liver, spleen, and conjunctivae. Others reported involvement of lymph nodes, skin, GI tract, kidney, bone marrow, or brain. These patients were more likely to have increased frequencies of infections, hepatosplenomegaly, iridocyclitis, autoimmune hemolytic anemia, or immune thrombocytopenic purpura. Successful treatment of granulomas with tumor necrosis factor-alpha antagonists has been reported in a few patients with common variable immunodeficiency.
  • One report described a possible role of human herpesvirus 8 (HHV-8) in the lymphoproliferative disorders in patients with common variable immunodeficiency. Authors reported high copy numbers of HHV-8 genome in peripheral blood mononuclear cells as well as in the lymph node in patients with common variable immunodeficiency who have lymphoproliferative disorders.
• Increased risk of developing malignant neoplasms
  • Patients with common variable immunodeficiency have a high risk of developing malignant neoplasms, such as non-Hodgkin lymphoma, GI carcinoma, or malignant lymphoma. Most of these are of the B-cell immunophenotype and frequently are associated with Epstein-Barr virus (EBV).
  • Lymphoma occurs 3 times more frequently in women with common variable immunodeficiency than in affected men. Women with common variable immunodeficiency are reported to have more than 400-fold increased risk of developing non-Hodgkin lymphoma than general population. Malignant lymphomas in patients with common variable immunodeficiency occur most frequently in the fifth to seventh decade and not in childhood. These malignant lymphomas are usually extranodal and histologically are intermediate-grade to high-grade non-Hodgkin lymphomas. Most of these lymphomas are of the B-cell immunophenotype and may be associated with EBV. Patients with common variable immunodeficiency also have a 47-fold increased risk for gastric carcinoma than general population. Other malignancies include colon cancer, breast cancer, gastric cancer, prostate cancer, ovarian cancer, oral cancer, and melanoma.

Several laboratories attempted classification of common variable immunodeficiency based on B-cell subpopulation as prognostic markers. Reduced numbers of switched memory B cells (CD19+CD27+IgM-IgD-) were predictors of autoimmune diease, granulomatous disease, and splenomegaly. 

 

Physical

In contrast to patients with X-linked agammaglobulinemia, many patients with common variable immunodeficiency have generalized lymphadenopathy and splenomegaly. Other positive physical examination findings depend on their clinical presentation and organ involvement (see History). Young children with common variable immunodeficiency may present with failure-to-thrive (FTT) secondary to frequent infection and increased energy expenditure. FTT may occur secondary to malabsorption syndrome associated with infection, inflammatory bowel disease, or spruelike illness.

Causes

This disorder likely has various causes, and a single etiology is unlikely. The search for gene(s) that underlie common variable immunodeficiency has been difficult, partly because of the heterogeneity. Although most cases are sporadic, at least 10% are familial with autosomal dominant inheritance more common than autosomal recessive inheritance. 

The following genetic defects have been described in patients with common variable immunodeficiency: TACI (transmembrane activator and calcium-modulating cyclophilin ligand interactor, TNFRSF13B), ICOS (inducible costimulator of activated T cells), CD19 deficiency, and BAFFR (B-cell activating factor of the TNF family receptor, TNFRSF13C). 

Table 1. Genetic Defects in Common Variable Immunodeficiency

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