THU0267 SERUM IGG2 LEVELS PREDICT VERY LONG-TERM PROTECTION FOLLOWING PNEUMOCOCCAL VACCINE IN SYSTEMIC LUPUS ERYTHEMATOSUS (SLE)

Background:

Systemic lupus erythematosus (SLE) patients are at increased risk forStreptococcus pneumoniaeinfection. Although pneumococcal vaccination is an attractive method to prevent invasive pneumococcal infection, vaccination coverage remains dramatically low in SLE. Moreover, the efficacy of vaccination may be reduced in SLE patients and sequential pneumococcal vaccination using new conjugated pneumococcal vaccines in combination with 23-valent pneumococcal polysaccharide vaccine (PPV23) is now advocated. However, limited study directly addressed the immune efficacy of such prime-and-boost strategy in SLE

Objectives:

We aimed to measure the immunological efficacy of the sequential pneumococcal vaccination using PCV13 in combination with PPV23 and identify factors associated with long-term immune protection following vaccination in SLE.

Methods:

SLE patients received PCV13 vaccine followed by PPSV23 vaccine 8 weeks later. Immune protection, defined by an antigen-specific IgG concentration ≥ 1.3 µg/mL for at least 70% of 7 pneumococcal serotypes (4, 6B, 9V, 14, 18C, 19F, 23F), was assessed at baseline, 2 months, 12 months, and 36 months, defining very long-term protection.

Results:

21 (40[25-75] years; 85.7% female) SLE patients received the sequential PCV13/PPV23 vaccines. Only 10 (47.6%) showed a sustained immune protection against pneumococcal infection 36 months after PCV13 shot (very long-term protected, VLTP). Eleven patients had no long-term protection (NLTP) with a seroconversion that never (n=6) or only transiently (n=5) occurred. SLE disease features, treatment received and immunological characteristic did not differ between VLTP and NLTP patients except for a lower serum IgG2 levels in NLTP (1.45 [1.30, 1.82] vs 3.30 [2.92, 4.44] g/L, p<0.001). Noteworthy the ROC curve showed that the serum IgG2 level before vaccination (AUC 0.95 [95% CI: 0.84-1]; p=0.004) was predictive for very long-term protection. A baseline serum IgG2 level of 2.125µg/ml or more showed a sensitivity of 100% and a specificity of 90.9% for very long-term protection

Conclusion:

The benefit of sequential PCV13/PPV23 vaccination in SLE is limited. Baseline IgG2 serum level before vaccination is strongly indicative of very long term protection following vaccination

Disclosure of Interests:

None declared

Reduced susceptibility to amoxicillin of oral streptococci following amoxicillin exposure

As antibiotic pressure often triggers bacterial resistance, the use of short-duration therapies is increasingly recommended. The objective of the present study was to evaluate both the clinical efficiency and the impact on oral streptococci of a 3 day versus a 7 day amoxicillin therapy for odontogenic infection requiring tooth extraction. On day 0, patients were randomly assigned to a 3 day or 7 day amoxicillin treatment. The tooth was extracted on day 2 and the post-operative follow-up was carried out on day 9. Oral flora was collected on days 0, 9 and 30, and the susceptibility of the streptococci to amoxicillin was determined. The results showed that treatment with amoxicillin for 3 or 7 days had a similar clinical efficiency, and also induced similar selection of oral streptococci with reduced susceptibility to amoxicillin, suggesting that the selection of strains with reduced susceptibility to amoxicillin is a rapid phenomenon, appearing even with short-duration therapies.

Pharmacokinetics of total immunoglobulin G and immunoglobulin G subclasses in patients undergoing replacement therapy for primary immunodeficiency syndromes

BACKGROUND AND OBJECTIVES

Careful evaluation of the pharmacokinetic properties of a new immunoglobulin G (IgG) preparation is necessary to ensure that the product will not deviate significantly from existing products, in terms of pharmacological activity.

MATERIALS AND METHODS

A prospective, open and uncontrolled trial was performed in 16 patients with primary immunodeficiency syndromes. Patients who had been under replacement therapy with licensed preparations prior to study inclusion, received 280 +/- 60 mg/kg of a solution of IgG, ready for intravenous administration, every 3 weeks for 6 months. Trough and peak plasma levels were measured immediately before and 1 h after each infusion, respectively. Pharmacokinetic parameters were calculated for total IgG and IgG subclasses.

RESULTS

Total IgG, IgG1, IgG2 and IgG3 declined mono-exponentially in contrast to IgG4 which showed a bi-exponential decline. Half-lives which were highly variable among patients were similar for total IgG, IgG1 and IgG2 (35.9 +/- 10.8, 36.3 +/- 9.2, and 37.1 +/- 13.9 days, respectively) and shorter for IgG3 and IgG4 (28.6 +/- 10.4 and 15.6 +/- 4.5 days, respectively).

CONCLUSIONS

The decline of IgG4 probably reflected a complex catabolic pathway specific for this subclass. As the plasma level of IgG4 is low, the decline of total IgG remained unaffected. Pharmacokinetic properties were consistent with results reported elsewhere in patients undergoing replacement therapy for primary immunodeficiency syndromes.

Infected splenic dendritic cells are sufficient for prion transmission to the CNS in mouse scrapie

Transmissible spongiform encephalopathies display long incubation periods at the beginning of which the titer of infectious agents (prions) increases in peripheral lymphoid organs. This "replication" leads to a progressive invasion of the CNS. Follicular dendritic cells appear to support prion replication in lymphoid follicles. However, the subsequent steps of neuroinvasion remain obscure. CD11c(+) dendritic cells, an unrelated cell type, are candidate vectors for prion propagation. We found a high infectivity titer in splenic dendritic cells from prion-infected mice, suggesting that dendritic cells carry infection. To test this hypothesis, we injected RAG-1(0/0) mice intravenously with live spleen cell subsets from scrapie-infected donors. Injection of infected dendritic cells induced scrapie without accumulation of prions in the spleen. These results suggest that CD11c(+) dendritic cells can propagate prions from the periphery to the CNS in the absence of any additional lymphoid element.

Plasma cell dyscrasia-related glomerulopathies and Fanconi's syndrome: a molecular approach

Considerable advances in the understanding of renal complications of dysglobulinemia have occurred in the last 10 years. They mostly result from sequence studies of nephritogenic immunoglobulin chains and comparison with sequence database, and from a careful analysis of clinicopathological features including electron microscopy characteristics of immunoglobulin deposits. These advances should help define subpopulations of patients with plasma cell dyscrasia at risk of developing renal complications and to design novel therapeutic approaches. Although renal complications of plasma cell dyscrasias may be considered as anecdotal diseases, understanding their pathophysiology may help dissect the mechanisms of glomerular and proteinuria-induced interstitial fibrosis.

Prion diseases and the immune system

Transmissible spongiform encephalopathies are caused by unusual infectious agents that are purported to contain a single type of macromolecule, a modified host glycoprotein. The term prion has been applied to this group of agents. Surprisingly, the immune system appears to behave as a Trojan's horse rather than a protective fortification during prion infections. Because prions seem to be essentially composed of a protein, PrP(Sc), identical in sequence to a host encoded protein, PrP(C), the specific immune system displays a natural tolerance. However, lymphoid organs are strongly implicated in the preclinical stages of the disease. Certain immunodeficient animals are resistant to prions after peripheral inoculation. In normal subjects, cells of the immune system support the replication of prions and/or allow neuroinvasion. A better understanding of these aspects of prion diseases could lead to immunomanipulation strategies aimed at preventing the spread of infectious agents to the central nervous system.

Adult Fanconi syndrome secondary to light chain gammopathy. Clinicopathologic heterogeneity and unusual features in 11 patients

Fifty-seven cases of Ig light chain-associated Fanconi syndrome (FS) have been reported so far, mostly as isolated reports. The pioneering work by Maldonado and associates (35), who reviewed the first 17 cases in 1975, led to the unifying concept that patients with FS and Bence Jones proteinuria have a special form of plasma cell dyscrasia characterized by slow progression of the tumor and by prominent crystal formation in proximal tubule cells, in the absence of myeloma casts in the distal tubule. We carefully reappraised these characteristics in a series of 11 patients. Ten renal biopsy specimens were available for electron microscopy, adding to the 15 previously reported cases with ultrastructural studies. Moreover, 10 of the kappa light chains could be entirely or partially sequenced and tested for their resistance to cathepsin B, a lysosomal protease present in proximal tubule cells. Our series showed an unexpected clinicopathologic heterogeneity. Seven patients presented with the typical clinical and pathologic features of FS and low-mass myeloma or monoclonal gammopathy of undetermined significance (MGUS), in keeping with Maldonado et al's description. Crystals in bone marrow cells were detected in patients of this group, only. Three patients who presented with full-blown FS exhibited, however, the characteristic features of myeloma cast nephropathy in the setting of high-mass myeloma. One patient of this group also had numerous crystals in proximal tubule cells. The eleventh patient had complete FS with MGUS, but no crystals in proximal tubule cells even after electron microscopy. Contrasting with the clinicopathologic heterogeneity, genetic and biochemical analyses of the light chains showed a striking homogeneity. First, they all were of the kappa type. Second, 8 of 9 belonged to the V kappa I variability subgroup, which indicates that FS light chains are related by the sequence of their variable regions. Third, the 8 V kappa I light chain sequences most likely originated from only 2 germline genes, LCO2/012 and LCO8/018. Fourth, all 5 LCO2/012-derived sequences presented an unusual hydrophobic or nonpolar residue at position 30. These sequence peculiarities may account for unusual physicochemical properties of the light chains including the resistance of their variable domain V kappa to proteolysis by cathepsin B, observed in 7 of 9 patients in our series, while light chains isolated from patients with myeloma cast nephropathy are completely digested. Resistance of V kappa to proteolysis in FS patients can explain the accumulation of the light chain in the endocytotic compartment of the proximal tubule cells, leading to impairment of proximal tubule functions.

Reversion of prion protein conformational changes by synthetic beta-sheet breaker peptides

BACKGROUND

Transmissible spongiform encephalopathies are associated with a structural transition in the prion protein that results in the conversion of the physiological PrPc to pathological PrP(Sc). We investigated whether this conformational transition can be inhibited and reversed by peptides homologous to the PrP fragments implicated in the abnormal folding, which contain specific residues acting as beta-sheet blockers (beta-sheet breaker peptides).

METHODS

We studied the effect of a 13-residue beta-sheet breaker peptide (iPrP13) on the reversion of the abnormal structure and properties of PrP(Sc) purified from the brains of mice with experimental scrapie and from human beings affected by sporadic and variant Creutzfeldt-Jakob disease. In a cellular model of familial prion disease, we studied the effect of the peptide in the production of the abnormal form of PrP in intact cells. The influence of the peptide on prion infectivity was studied in vivo by incubation time assays in mice with experimental scrapie.

FINDINGS

The beta-sheet breaker peptide partly reversed in-vitro PrP(Sc) to a biochemical and structural state similar to that of PrPc. The effect of the peptide was also detected in intact cells. Treatment of prion infectious material with iPrP13 delayed the appearance of clinical symptoms and decreased infectivity by 90-95% in mice with experimental scrapie.

INTERPRETATION

Beta-sheet breaker peptides reverse PrP conformational changes implicated in the pathogenesis of spongiform encephalopathies. These peptides or their derivatives provide a useful tool to study the role of PrP conformation and might represent a novel therapeutic approach for prion-related disorders.

Long-term chimerism and B-cell function after bone marrow transplantation in patients with severe combined immunodeficiency with B cells: A single-center study of 22 patients

We retrospectively analyzed the B-cell function and leukocyte chimerism of 22 patients with severe combined immunodeficiency with B cells (B(+) SCID) who survived more than 2 years after bone marrow transplantation (BMT) to determine the possible consequences of BMT procedures, leukocyte chimerism, and SCID molecular deficit on B-cell function outcome. Circulating T cells were of donor origin in all patients. In recipients of HLA-identical BMT (n = 5), monocytes were of host origin in 5 and B cells were of host origin in 4 and of mixed origin in 1. In recipients of HLA haploidentical T-cell-depleted BMT (n = 17), B cells and monocytes were of host origin in 14 and of donor origin in 3. Engraftment of B cells was found to be associated with normal B-cell function. In contrast, 10 of 18 patients with host B cells still require Ig substitution. Conditioning regimen (ie, 8 mg/kg busulfan and 200 mg/kg cyclophosphamide) was shown neither to promote B-cell and monocyte engraftment nor to affect B-cell function. Eight patients with B cells of host origin had normal B-cell function. Evidence for functional host B cells was further provided in 3 informative cases by Ig allotype determination and by the detection, in 5 studied cases, of host CD27(+) memory B cells as in age-matched controls. These results strongly suggest that, in some transplanted patients, host B cells can cooperate with donor T cells to fully mature in Ig-producing cells.

Biochemical and conformational variability of human prion strains in sporadic Creutzfeldt-Jakob disease

The pathogenesis of prion (PrP) diseases is thought to be related to conformational changes of a normal cellular protein, PrPC, into a protease resistant protein called PrPSc, which is infectious by itself. A difficulty with this 'protein only' hypothesis is the existence of numerous PrP strains, that require PrPSc to have multiple conformations. Sporadic Creutzfeldt-Jakob disease (CJD), which accounts for nearly 80% of human prionoses, was reported to include at least two 'strains' termed types 1 and 2 which differ by electrophoretic patterns of their proteinase K (PK)-resistant fragments (PrP27-30). We have analyzed the biochemical and structural properties of PrPSc and PrP27-30 isolates from six sporadic CJD patients. Fourier transform-infra-red spectroscopy, PrP27-30 glycosylation patterns and studies of PK sensitivity revealed a striking heterogeneity. Furthermore, one isolate yielded a PrP27-30 fragment with a lower mobility clearly different from previously described sporadic CJD types. Although the average beta-sheet content was higher among type 1 isolates, there was overlap between the two types. Our study suggests that human sporadic CJD-related prions display a significant heterogeneity.

Megalin knockout mice as an animal model of low molecular weight proteinuria

Megalin is an endocytic receptor expressed on the luminal surface of the renal proximal tubules. The receptor is believed to play an important role in the tubular uptake of macromolecules filtered through the glomerulus. To elucidate the role of megalin in vivo and to identify its endogenous ligands, we analyzed the proximal tubular function in mice genetically deficient for the receptor. We demonstrate that megalin-deficient mice exhibit a tubular resorption deficiency and excrete low molecular weight plasma proteins in the urine (low molecular weight proteinuria). Proteins excreted include small plasma proteins that carry lipophilic compounds including vitamin D-binding protein, retinol-binding protein, alpha(1)-microglobulin and odorant-binding protein. Megalin binds these proteins and mediates their cellular uptake. Urinary loss of carrier proteins in megalin-deficient mice results in concomitant loss of lipophilic vitamins bound to the carriers. Similar to megalin knockout mice, patients with low molecular weight proteinuria as in Fanconi syndrome are also shown to excrete vitamin/carrier complexes. Thus, these results identify a crucial role of the proximal tubule in retrieval of filtered vitamin/carrier complexes and the central role played by megalin in this process.

Heavy chain deposition disease: the disease spectrum

A 45-year-old white woman was found to have microscopic hematuria during her annual physical examination. After a negative urologic workup, she returned 5 months later with nephrotic syndrome, renal insufficiency, and hypocomplementemia. Renal biopsy showed a nodular sclerosing glomerulopathy that could not be further characterized because of inadequate tissue for immunofluorescence. The patient returned 8 months later with chronic renal failure. A repeat renal biopsy showed deposits composed of immunoglobulin G (IgG) heavy chain and complement components C3 and C1 along glomerular, tubular, and vascular basement membranes, with negativity for kappa and lambda light chains, findings consistent with heavy chain deposition disease (HCDD). The heavy chain subclass was exclusively IgG3. Staining with monoclonal antibodies to epitopes of the constant domains of IgG heavy chain showed a CH1 deletion, indicating a truncated heavy chain. On review of the previously reported cases of HCDD, common clinical presentations include nephrotic syndrome, renal insufficiency, hematuria, and, in some cases, hypocomplementemia. In most patients, the hematologic disorder is mild, without overt myeloma. Light microscopy shows a nodular sclerosing glomerulopathy, and heavy chain deposits are detectable within basement membranes throughout the kidney by immunofluorescence and electron microscopy. There is no effective treatment for this condition, and virtually all patients progress to chronic renal failure.

Kappa light chain-associated Fanconi's syndrome: molecular analysis of monoclonal immunoglobulin light chains from patients with and without intracellular crystals

Plasma cell dyscrasias may be responsible for Fanconi's syndrome, due to the toxicity of a free monoclonal kappa light chain toward kidney proximal tubules. Eight cases of Fanconi's syndrome were analyzed. We compared the structures of VkappaI variability subgroup V domains from five cases of Fanconi's syndrome and one myeloma without renal involvement. Among Fanconi cases, four putative structures were obtained after molecular modeling by homology, and the other had previously been refined by X-ray crystallography. The complete sequences of one VkappaI, one VkappaIII and N-terminal sequences of two VkappaI light chains, from patients with different forms of Fanconi's syndrome, were compared with four previously studied sequences. All three kappa chains responsible for a 'classical' form with intralysosomal crystals and a low mass myeloma, were encoded by the LCO2/O12 germline gene and had an unusual non-polar residue exposed to the solvent in the CDR-L1 loop. Of both VkappaI light chains from patients with Fanconi's syndrome without intracellular crystals, one derived from LCO2/O12 and the other from LCO8/O18 gene. Another feature that could be related to non-crystallization was the absence of accessible side chains in the CDR-L3 loop which is known to be implicated in dimer formation.

Nodular glomerulosclerosis with deposition of monoclonal immunoglobulin heavy chains lacking C(H)1

The objective of this study was to further characterize the clinical and immunopathologic features of heavy chain deposition disease (HCDD), a recently described entity. Four patients were diagnosed as having HCDD on a kidney biopsy. All presented with nodular glomerulosclerosis with deposition of gamma1 heavy chains lacking CH1 epitopes, but without light chains. Two different patterns were observed in the serum. First, patients 1 and 2 had a circulating monoclonal IgGlambda containing a short gamma1 heavy chain lacking CH1 epitopes, with an apparent molecular weight of 40 kD consistent with a complete CH1 deletion. Biosynthetic experiments also showed that the deleted heavy chain was produced in excess compared with light chains, and was secreted in vitro together with half Ig molecules, although these abnormal components were not detected by Western blot analysis of whole serum. Second, patients 3 and 4 had a circulating monoclonal IgG1lambda with an apparently normal, nondeleted heavy chain subunit, but serum fractionation followed by immunoblotting revealed an isolated monoclonal gamma1 chain lacking CH1 epitopes. These data strongly suggest that renal deposition of a CH1-deleted heavy chain circulating in low amounts in the serum as a free unassembled subunit is a major feature of HCDD. The CH1 deletion is most likely responsible for the premature secretion in blood of the heavy chain by a clone of plasma cells.

The structure of an entire noncovalent immunoglobulin kappa light-chain dimer (Bence-Jones protein) reveals a weak and unusual constant domains association

Monoclonal free light chains secreted in immunoproliferative disorders are frequently involved in renal complications, including a specific proximal tubule impairment, Fanconi's syndrome. The latter is characterized in most cases by intracellular crystallization including a light-chain variable-domain fragment which resists lysosomal proteases. Bence-Jones protein (BJP) DEL was isolated from a patient with myeloma-associated Fanconi's syndrome. The crystal structure of this human kappa immunoglobulin light-chain noncovalent dimer was determined using molecular replacement with the structure of molecule REI, as the variable domain, and that of BJP LOC as the constant domain. To our knowledge, DEL is the first complete kappa BJP structure described to date. The R-factor is 20.7% at 2.8 A resolution. The BJP DEL dimer was compared with other light-chain dimers and with Fab fragments with a kappa light chain. Although the domain-folding pattern was similar, the relative positions of the constant domains differed. BJP DEL showed a noncanonical quaternary structural arrangement which may be attributable to the poor CL-CL affinity and lack of an interchain disulfide bridge, combined with the conformational editing effect of the crystal-packing forces. Our results suggest that, in the absence of a disulfide bridge, most BJP CLs are probably mobile in solution. This may explain their high susceptibility to proteases and the absence of naturally occurring crystals for these dimers. Furthermore, these findings of an unusual quaternary structure of an immunoglobulin light-chain association extend our knowledge about the large and highly diverse structures of the immunoglobulin superfamily.

Prion diseases and the immune system

Unlike other infectious diseases, transmissible spongiform encephalopathies elicit no specific immune response. Indeed, because the infectious agent, the prion, seems to be essentially composed of a protein with a primary structure identical to a host encoded protein, the lymphoid system is naturally tolerant. However, lymphoid organs are strongly implicated in the early peripheral steps of the disease. Paradoxically, immunodeficient animals, which are more susceptible to infections by usual pathogens, appear to be partially or completely resistant to experimental infection by prions by peripheral route. Several studies suggest that in normal subjects, cells of the immune system support the replication of prions and might allow their spreading from the periphery to the central nervous system. Thus, the lymphoid system appears to behave as a Trojan horse rather than a protective fortification in the process of prion infection. A greater understanding of the pathophysiology of these aspects of prion diseases could lead to immunomanipulation strategies aimed at preventing prion spread into the central nervous system, once peripheral exposure has occurred.

The prionoses and other conformational disorders

The basic pathogenesis of numerous neurodegenerative disorders is now thought to be related to abnormal protein conformation. The common theme in all these diseases is the conversion of a normal cellular and/or circulating protein into an insoluble, aggregated, beta-sheet rich form which is deposited in the brain, sometimes in the form of amyloid. These deposits are toxic and produce neuronal dysfunction and death. The most common of these illnesses is Alzheimer's disease (AD), in which a central event is the conversion of the normal soluble amyloid beta (sA beta) peptide to amyloid beta (A beta) within neuritic plaques and cerebral vessels. A unique category of the conformational conditions are prion related diseases (or prionoses), where the etiology is thought to be related to conversion of the normal prion protein, PrPC, into an infectious and pathogenic form, PrPSc. In the case of AD and the prionoses, the conformational change can be influenced by the presence of mutations in various gene products, as well as by chaperone proteins. Apolipoprotein E is thought to act as such a chaperone protein in AD; however, among the prionoses such a protein has been hypothesized to exist only by indirect evidence and is called "protein X". Our growing understanding of the mechanisms involved in this category of diseases, raises the possibility of therapeutic approaches based directly on the prevention and reversal of pathologic protein conformation.

IgG subclass distribution of antibody responses to protein and polysaccharide mycobacterial antigens in leprosy and tuberculosis patients

Immunoenzymatic assays were developed for the measurement of antibodies against mycobacterial lipoarabinomannan (LAM), a cell-free proteic extract (CFX) of Mycobacterium leprae, and the 38-kD protein antigen of M. tuberculosis. Sera from 108 leprosy patients, belonging to all clinical-immunological forms of the spectrum, and 81 patients with localized or disseminated tuberculosis (TB) were tested for antibodies of the four IgG subclasses. Standard calibration curves were used to allow comparisons between results of different isotypes and specificities. Mean concentrations of total IgG antibodies were higher in the overall leprosy population than in TB patients. In leprosy, levels of anti-CFX increased from tuberculoid toward lepromatous forms, with a clear switch from IgG1 to IgG2 subclass predominance. A similar IgG1 to IgG2 conversion was observed in anti-LAM antibodies, although total levels of anti-LAM were similar in patients with tuberculoid and lepromatous forms. In TB, antibodies against polysaccharide and protein antigens were both predominantly of IgG1 subclass, whatever the patient's clinical status, although lower in disseminated forms, probably due to concomitant HIV infection. A hypergammaglobulinaemia was also found in most leprosy and TB patients. In TB this was due to increased IgG1 and IgG3, especially in HIV co-infected patients. Based on the current knowledge of the influence of T cell-secreted cytokines on human immunoglobulin isotype expression, these results do not fit with a putative role of Th1 (such as found in TB and tuberculoid leprosy (TT)) and Th2 (such as found in leprosy lepromatous (LL) leprosy) environment in the isotypy of antibody responses in mycobacterial infections. Nor do variations of isotypy according to pathological conditions seem to be related to the biochemical nature of antigens, since antibodies to LAM and protein antigens had comparable evolutions of their subclass distribution. Other factors are to be investigated in order to understand better the significance and possible roles of antibodies in mycobacterial diseases.

[Immunoglobulin amyloidosis]

AL amyloidosis is a rare disease. Its diagnosis is based on histopathology. It is always secondary to light chain, only rarely heavy chain, synthesis of monoclonal immunoglobulin, associated or not with tumoural proliferation (myeloma, Waldenström's macroglobulinaemia). Its pathophysiology has not been elucidated, but recent progress provided by biochemical and molecular biology studies has provided some data on the structural anomalies responsible for the formation of amyloid fibrils. As in AA amyloidosis, the clinical picture is heterogeneous and mainly depends on the degree and extent of the lesions. Prognosis remains poor and is influenced by the degree of cardiac, gastrointestinal, neurologic and renal involvement, but also by the presence of absence of underlying hemopathy, and particularly of myeloma. Treatment is still essentially symptomatic, but recent progress points to hope of effective treatment modalities aiming at reducing or eliminating the clone producing the immunoglobulin, or inhibiting the formation or amyloid fibrils.

Molecular modeling of immunoglobulin light chains implicates hydrophobic residues in non-amyloid light chain deposition disease

Light chain deposition disease is a severe complication of certain immunoproliferative disorders, due to the secretion of a monoclonal light chain which precipitates close to basement membranes of several tissues. A kappa isotype restriction and an unusual frequency of a variable region subgroup (VkappaIV) suggest that precise structural features govern the propensity of pathogenic light chains to precipitate in extracellular spaces. We studied primary structures of light chains from six patients with light chain deposition disease in comparison with light chains from other pathological conditions. Sequence alignment revealed the presence of certain amino acids only in light chain deposition disease, in particular non-polar replacing hydrophilic residues. To determine the role of these residues, structures of the variable domain from four kappa chains belonging to VkappaI and VkappaIV subgroups responsible for deposition disease were modeled using known immunoglobulins as templates. The most evident structural features shared by all pathogenic light chains were hydrophobic residues exposed to the solvent in complementarity determining regions 1 or 3. In contrast to immunoglobulin light chain-related amyloidosis, where deposition of organized material might be due to electrostatic interactions between light chain dimers, hydrophobic interactions could enhance amorphous precipitation in non-amyloid light chain deposition disease.

Selective IgG1 deficiency

Measurement of serum IgG subclass levels in 3005 patients disclosed abnormally low IgG1 levels with normal levels of the other IgG subclasses and of IgM and IgA in 119 patients, predominantly adults. Not all patients were hypogammaglobulinemic due to nonrare increases of other isotypes, mostly IgM. A familial context of immunodeficiency was frequent, more often combined than selective IgG1 deficiency. A familial association with IgG2 deficiency was found also and IgG1 replaced IgG2 deficiency in 3 cases (and succeeded to or preceded more complex IgG defects in 3 cases, whereas IgG1 deficiency was consistently found at examinations repeated in the absence of therapy in 10 additional cases). Most but not all (83.2%) patients suffered infections, generally moderate, similar to those observed in other selective IgG subclass deficiencies (IgGSD), with predominantly sinorespiratory infections. Other clinical manifestations such as atopy, congenital cardiopathy, and autoimmune diseases were already known in IgGSD but the incidence of asthma was strikingly high (one-fifth of the cases).

High prevalence and usual persistence of serum monoclonal immunoglobulins evidenced by sensitive methods in renal transplant recipients

BACKGROUND

The occurrence of serum monoclonal immunoglobulins in kidney transplant recipients is well known but their significance and predictive value for the occurrence of lymphoma are a matter of debate. We therefore conducted a study of monoclonal immunoglobulins by a sensitive method during the long-term follow up of grafted patients.

METHODS

Monoclonal immunoglobulins were characterized by high-resolution electrophoresis, conventional immunoelectrophoretic analysis, and a sensitive Western blotting procedure in the serum from 84 renal transplant recipients prior to grafting and subsequently, with a 1-8-year follow-up and excluding the patients who developed posttransplant lymphoma.

RESULTS

Low abundance monoclonal immunoglobulins were detectable prior to transplantation in 56 cases (66.6%) and after graft in 72 cases (85.5%) (and in 1 case (1.2%) and 18 cases (21.4%) of cases respectively, by immunoelectrophoresis). These abnormalities were often multiple in individual sera. Monoclonal components detected by immunoblotting were transient in 23.8% of patients only (whereas those evidenced by immunoelectrophoresis usually became undetectable by this method) and their pattern was remarkably stable in the majority of cases. The frequency of post-transplant monoclonal immunoglobulins was higher in patients of more than 50 years of age than in younger patients. The appearance of monoclonal components after grafting and their transient character correlated with CMV infections. No correlation was found with various other parameters. The isotypic distribution of monoclonal immunoglobulins with an IgM, IgG3, and IgG1 predominance and an abnormally low kappa/lambda ratio was the same as that observed in various immunodeficiency states. The monoclonal immunoglobulin pattern in three further patients who developed post-transplant lymphoma was unremarkable.

CONCLUSION

Monoclonal immunoglobulins hence are not discriminant for lymphoma and their characterization does not appear to be necessary in the evaluation of followed up grafted patients, at least for a prediction of post-transplant lymphoma.

Evaluation of monoclonal antibodies with specificity for human IgA, IgA subclasses and allotypes and secretory component. Results of an IUIS/WHO collaborative study

51 monoclonal antibodies (McAb) with putative specificity for human IgA, the IgA subclasses, Am allotypes or secretory component (SC) were evaluated for immunoreactivity and specificity by nine laboratories employing immunodiffusion, agglutination, immunohistological assays, immunoblotting and direct binding and competitive inhibition enzyme immunoassays. McAbs specific for IgA PAN (n = 24), IgA1 (n = 7), IgA2 (n = 3), IgA2m(2) (n = 2), non-IgA2m(2) (n = 4) and SC or secretory IgA (n = 5) were identified that were immunoreactive and specific in the assays employed. The McAbs identified as IgA- or SC-reactive were shown to be non-reactive to human IgG, IgM, IgD, IgE, kappa and lambda by direct binding and competitive inhibition immunoassays. Interestingly, no McAbs with restricted specificity for IgA2m(1) were identified. Some McAbs displayed higher affinity and/or better performance in one or several of the assay groups. The IgA- and SC-specific McAbs identified in this international collaborative study have potential as immunochemical reference reagents to identify and quantitate monomeric and polymeric IgA in human serum and secretions.

Mitogenic activity of new lectins from seeds of wild Artocarpus species from Vietnam

Proliferative response of human peripheral blood mononuclear cells (PBMC) stimulated by new lectins purified from seeds of differents Artocarpus species from Vietnam (A. asperulus, A. heterophyllus, A. masticata, A. melinoxylus, A. parva and A. petelotii) was studied and compared to those of the lectin jacalin purified from jackfruit (A. heterophyllus) seeds collected in the island La Réunion. All lectins stimulated human PBMC to proliferate, with a variable efficiency of the mitogenic activity. Phenotypic analysis of cells recovered after 7 day-cultures showed that these lectins mostly stimulated CD4+ T lymphocytes. These results suggest that these lectins from different Artocarpus species are similar in terms of their mitogenic activity although their structural features are not identical.

In vivo role of IL-6 on the viral load and on immunological abnormalities of HIV-infected patients

In vitro experiments have suggested that interleukin (IL)-6 may contribute to human immunodeficiency virus (HIV) burden and to immunological abnormalities in HIV-infected patients. We had the opportunity to directly address this question in vivo through the virological and immunological monitoring of HIV-infected patients treated with an anti-IL-6 monoclonal antibody (mAb) for a lymphoma (ANRS 018 trial). Sixteen courses of anti-IL-6 mAb administration, performed in 11 patients, were studied. All patients were at a late stage of HIV infection. The HIV load and the immunological status were determined at the initiation of each course and at its end, 21 days later. The mAb induced no significant change of HIV load, as evaluated by p24 antigenemia, plasma viremia, and quantification of circulating HIV RNA by reverse transcriptase-polymerase chain reaction and branched DNA techniques. The anti-IL-6 mAb also did not affect CD4+, CD8+, and CD19+ circulating cell counts, nor the serum concentrations of sIL-2R and of sCD8. In contrast, the mAb completely abrogated acute-phase reaction, as demonstrated by the normalization of C-reactive protein and fibrinogen circulating levels (p = 0.013 and p = 0.008, respectively). It increased serum albumin concentration. The latter effect was restricted to patients with a spontaneously low albuminemia (p = 0.01). It decreased B-lymphocyte hyperactivity, as reflected by decreased IgG and IgA serum levels (p = 0.008 and p < 0.001, respectively), and by a decreased production of IgG in vitro (p = 0.017). In contrast, the IgM hyperproduction was not affected by the mAb. Therefore, increased IL-6 production in HIV-infected patients at a late stage of the infection may not stimulate HIV replication in vivo, but it may represent a key mechanism contributing to the metabolic and immunological dysbalance of the disease.

Role of light chain variable region in myeloma with light chain deposition disease: evidence from an experimental model

Light chain deposition disease (LCDD) results from a propensity of some human monoclonal L chains to form tissue deposits. We designed an experimental model for in vivo expression of human kappa L chain sequences in mice and compared a somatically mutated LCDD chain with a closely related control kappa chain, both encoded by the unique V kappa IV gene. Mice secreting the LCDD chain but not those producing the control chain showed deposits with a distribution similar to that observed in patients. These data show that discrete changes in V region sequences can play a major role in tissue deposition of human L chains.

Sequences of V kappa L subgroup light chains in Fanconi's syndrome. Light chain V region gene usage restriction and peculiarities in myeloma-associated Fanconi's syndrome

Certain monoclonal Ig light chains (LC) are responsible for marked disturbances of proximal tubule cell functions (Fanconi's syndrome, FS). In patients with FS, intracellular crystal-like inclusions containing LC determinants are commonly found in plasma cells, macrophages, and renal tubular cells. In an attempt at understanding the pathogenesis of myeloma-associated FS, we recently determined the first complete primary sequence of a kappa-LC (CHEB) responsible for the disease. We now report on the primary structure of three other kappa-LC of the V kappa l variability subgroup associated with FS (TRE, TRO, and DEL). After PCR amplification, cDNA encoding these LC were sequenced. CHEB, TRE, and TRO LC genes were found to be highly homologous to the same germline gene O2/O12. These patients had numerous intracellular crystals, whereas the fourth patient, DEL, had no detectable crystals. The LC from the latter patient was homologous to another germline gene, O8/O18. Comparison of these LC sequences to previously reported LC of the V kappa l subgroup allowed identification of a number of unusual amino acid substitutions in the V region that had rarely or never been previously described at the corresponding positions. Some of these unusual substitutions affect highly conserved amino acids located either in an external loop (residue 30) or in inner (residues 48 and 55) and outer (positions 63 and 72) beta-sheets that may be important for the structure and binding properties of the kappa-chains. These and several other substitutions, some of them shared with amyloidogenic kappa-LC, could induce conformational alterations and represent a determinant pathogenic factor.

Sequences of V kappa L subgroup light chains in Fanconi's syndrome. Light chain V region gene usage restriction and peculiarities in myeloma-associated Fanconi's syndrome

Certain monoclonal Ig light chains (LC) are responsible for marked disturbances of proximal tubule cell functions (Fanconi's syndrome, FS). In patients with FS, intracellular crystal-like inclusions containing LC determinants are commonly found in plasma cells, macrophages, and renal tubular cells. In an attempt at understanding the pathogenesis of myeloma-associated FS, we recently determined the first complete primary sequence of a kappa-LC (CHEB) responsible for the disease. We now report on the primary structure of three other kappa-LC of the V kappa l variability subgroup associated with FS (TRE, TRO, and DEL). After PCR amplification, cDNA encoding these LC were sequenced. CHEB, TRE, and TRO LC genes were found to be highly homologous to the same germline gene O2/O12. These patients had numerous intracellular crystals, whereas the fourth patient, DEL, had no detectable crystals. The LC from the latter patient was homologous to another germline gene, O8/O18. Comparison of these LC sequences to previously reported LC of the V kappa l subgroup allowed identification of a number of unusual amino acid substitutions in the V region that had rarely or never been previously described at the corresponding positions. Some of these unusual substitutions affect highly conserved amino acids located either in an external loop (residue 30) or in inner (residues 48 and 55) and outer (positions 63 and 72) beta-sheets that may be important for the structure and binding properties of the kappa-chains. These and several other substitutions, some of them shared with amyloidogenic kappa-LC, could induce conformational alterations and represent a determinant pathogenic factor.

SUBIM: a program for analysing the Kabat database and determining the variability subgroup of a new immunoglobulin sequence

Although various programs are available to extract all the information included in protein sequence databases, none is dedicated to immunoglobulins. For this purpose, we designed a program, SUBIM, which is adapted to the Kabat database specialized in immunoglobulin sequences. Besides all the possibilities of any database searching program, SUBIM analyses new sequences of variable regions and determines the variability subgroup they belong to. It also numbers the new sequence according to the system established by Kabat and co-workers for an easier comparison with the other immunoglobulins, thus realizing an automatic alignment with other members of a given type of immunoglobulin chain. This program is largely machine independent and requires very little memory, and should help biochemists concerned with new immunoglobulin sequences.

Protease resistance and binding of Ig light chains in myeloma-associated tubulopathies

Kidney tubule dysfunction and lesions are frequent complications of myeloma, related to unknown properties of the monoclonal light chain. We have analyzed protease sensitivity and binding properties of urinary light chains from four patients with Fanconi's syndrome, 12 with cast nephropathy, and four control patients without myeloma-associated tubulopathy. All light chains were normal-sized, monomeric and/or dimeric, and none was N-glycosylated. Kinetic studies of light chain digestion by pepsin and the lysosomal enzyme cathepsin B showed the generation of a protease-resistant 12 kDa fragment, corresponding to the V domain of the kappa chain in the four Fanconi's syndrome patients; in two out of four the V domain was also completely resistant to trypsin. Western and dot blots revealed similar patterns of reactivity of light chains from patients with the Fanconi's syndrome towards other light chains. Properties of cast-nephropathy light chains were more heterogeneous but clearly differed from those of Fanconi's syndrome: (i) 9 out of 12 were of the lambda-type; (ii) only four yielded a transient 12 kDa fragment after cathepsin B digestion, but all showed some resistance to proteolysis of the entire molecule or a fragment thereof to at least one protease, at variance with control light chains; (iii) they displayed various patterns of reactivity with other light chains; (iv) 7 out of 12 reacted specifically with Tamm-Horsfall protein (THP) by ELISA, in contrast with those of Fanconi's syndrome. In one patient who presented with cast nephropathy and the Fanconi's syndrome, the light chain exhibited both partial resistance of the V kappa domain to cathepsin B and the highest reactivity with THP.(ABSTRACT TRUNCATED AT 250 WORDS)

Structure of abnormal heavy chains in human heavy-chain-deposition disease

The sequences of two immunoglobulin gamma 1 heavy chains involved in the formation of non-amyloid tissue deposits were determined in two patients (RIC and THR) affected with plasma cell monoclonal proliferation and heavy-chain-deposition disease. The proliferating plasma cells of patients RIC and THR synthesized truncated gamma 1 chains of 45 kDa and 24 kDa, respectively, carrying internal deletions of the first constant (CH1) domain (RIC) or of the CH1, hinge and CH2 domains(THR). The shortened gamma chains were associated with lambda light chains in the monoclonal IgG component present in the serum from both patients but not in tissue deposits which lacked any detectable light chains. Bone marrow plasma cells from RIC contained short gamma 1 heavy-chain transcripts in which a VDJ exon related to the VH2 subgroup was directly joined to the hinge exon; plasma cells from THR contained short gamma 1 transcripts with a VDJ exon related to the VH3 subgroup joined to the CH3 exon. In both cases, the truncated transcripts carried precise deletions of complete exons and used regular splice sites at the variable/constant junction, consistent with the hypothesis that they originated from abnormal splicing of primary transcripts from the productively rearranged heavy-chain genes. Striking abnormalities of the variable regions were found, especially in framework regions, including replacement of an invariant tryptophan residue in protein from THR, hydrophobic residues most likely exposed to the solvent and inversion of charged amino acids probably exposed on the surface of the molecule.

Renal involvement in hematological disorders: monoclonal immunoglobulins and nephropathy

The study of monoclonal immunoglobulin-associated nephropathies is useful for analyzing the physicochemical properties of immunoglobulin components responsible for their deposition in the kidney. Notable advances include the first description of truncated heavy-chain deposition disease, characterization of protease resistance and binding properties of immunoglobulin light chains involved in myeloma-associated Fanconi's syndrome and cast nephropathy, and identification of hepatitis C virus as a plausible causative agent of the so-called essential mixed cryoglobulinemias.

[A new alpha chain of jacalin from two wild species of jack-fruit seeds]

Jacalins, from jack-fruit seeds of 2 wild species (Artocarpus asperulus, Artocarpus masticata) were purified by mucine-sepharose 4B affinity chromatography. The alpha and beta chains were separated by reverse phase high pressure liquid chromatography (HPLC). Analysis by HPLC with a C8 column and the determination of the N-terminal sequence of the alpha-chain of these jacalins allowed the identification of a new alpha-chain. Immunological cross-reactivity and carbohydrate specificity indicate that jacalins possessing the new alpha-chain conserve structural and functional properties of the other members of Artocarpus genus.

Overrepresentation of the V kappa IV subgroup in light chain deposition disease

The variability subgroup of human monoclonal kappa chains purified from urine in 3 consecutive patients with myeloma associated light chain deposition disease was determined from amino acid sequences of their first framework regions (FR1). N-glycosylation was searched for by N-glycosidase F treatment. These data together with our previously published results, indicate the pathogenic potential of the rare V kappa IV subgroup and confirm the absence of detectable serum and urine free monoclonal light chains when they are N-glycosylated.