Alloantibodies to Factor IX in Haemophilia B Characterized by Crossed Immunoelectrophoresis and Enzyme-conjugated Antisera to Human Immunoglobulins

Considerations on the use of Neisseria meningitidis class 5 proteins as meningococcal BC vaccine components

This investigation was carried out to evaluate the importance of individual meningococcal surface class 5 protein with respect to antibody induction and its functional activity. Two groups of mice were immunized with two vaccine preparations differing in the presence or absence of class 5 protein. The ELISA results show that both vaccines were immunogenic and elicited mainly IgG antibodies against the major classes of meningococcal surface proteins, and the absence of class 5 protein in the vaccine produced a significant change in the overall units ml-1 of antibodies against the homologous strain. The infant rat model and the bactericidal assay were used to evaluate the functional antibody activity. Our results showed that (1) even using two different challenge doses (10(6) and 10(7) bacteria/animal), mortality could not be detected when followed up at 48 h; (2) there was protection as determined by the infant rat model and bactericidal activity using sera from both vaccinated groups; (3) there were no differences in the bactericidal titres between these groups; (4) in the infant rat model there were no differences in the index of bacteraemia among the infected animals (counts ml-1 of blood); and (5) there were differences in the incidence of bacteraemia. This is the first evidence that some immunological differences in the vaccine response could be attributed to the absence of class 5 protein by using infant rat model but not by using the bactericidal assay.

Disappearance of inhibitor to factor IX in a patient with severe haemophilia B and immunological characterization of the inhibitor

Disappearance of an inhibitor to factor IX in an 11-year-old boy with haemophilia B is described. He had been given a total of 14,200 units of a prothrombin complex concentrate (PCC) before an inhibitor to factor IX developed. He subsequently received four separate infusions of PCC and his inhibitor titre rose in response to the treatment for the following 4 years. No inhibitor is presently detected despite repeated administration of PCC. Immunological characterization of the inhibitor by inhibitor neutralization assays, modified crossed-immunoelectrophoresis and enzyme-linked immunosorbent assay demonstrated that it contained IgG2 and IgG4 heavy chains and kappa and lambda light chains. No large deletion of the factor IX gene in the patient was observed using cDNA (cVII).

IgG subclass identification of inhibitors to factor IX in haemophilia B patients

Inhibitors to factor IX in haemophilia B are IgG antibodies. It is of interest to know the subclass type of these antibodies since the biological activity of the four IgG subclasses are different. Subclass identification has been difficult due to the lack of specific antibodies to IgG subclasses. Monoclonal hybridoma antibodies to these subclasses are now available. Here we present the results on the subclass identification of inhibitors from six patients with severe haemophilia B (titres 0.8-800 mu/ml). Plasma from one patient was obtained before inhibitor could be detected by coagulation assays. He had circulating complexes between factor IX and inhibitor. The technique used was crossed immunoelectrophoresis combined with an enzyme-linked immunoassay. This technique allows the subclass determination of both low-titre and high-titre inhibitors. All inhibitors gave a very strong reaction with antibody to IgG4, and four inhibitors also reacted with antibody to IgG1. Three of these inhibitors gave a faint reaction with antibody to IgG2 also, whereas no inhibitor contained any detectable IgG3. The finding of IgG4 as the main subclass is important since IgG4 antibodies do not bind complement. The presence of more than one subclass in the inhibitors demonstrates the heterogeneous nature of the inhibitors. This was demonstrated also at a stage of inhibitor development when the inhibitor could not be detected by coagulation assay.

Analysis of alpha-fetoprotein heterogeneity by an improved crossed immunoaffinoelectrophoretic technique

The crossed immunoaffinoelectrophoretic procedure described here for the analysis of alpha-fetoprotein heterogeneity includes three major modifications of a procedure previously used by others: impregnation of the second dimension gel with methylated sugar derivatives; rigorous gel washing at 37 degrees C with the same derivatives; and an immunostaining technique. These simple changes have resulted in clear, sharp electrophoretic patterns at levels of total alpha-fetoprotein as low as 50 ng/ml, a sensitivity not previously approached with the method. Individual peaks representing as little as 7.5 ng/ml can be identified.

Effects of the blocking agents bovine serum albumin and Tween 20 in different buffers on immunoblotting of brain proteins and marker proteins

The effects of the blocking agents bovine serum albumin and Tween 20 in buffers at pH values 7.2 and 10.2 were compared in immunoblotting with 2 different antisera. The antisera were raised against a purified brain-specific protein fraction from human brain, soluble in perchloric acid, and phosphate-activated glutaminase from pig brain, respectively. The antigens were a crude perchloric acid-soluble brain extract, a crude brain phosphate-activated glutaminase fraction, and proteins commonly used as molecular weight markers. The binding patterns of the 2 antisera to the respective brain antigen preparations changed, depending on the blocking agent and the pH of the blocking buffer. Also, antibody binding to the molecular weight marker proteins was observed with some of the blocking buffers. Immunoblotting with Tris-saline, pH 10.2, containing 3% bovine serum albumin as blocking agent and diluting buffer for the antisera, showed negligible antibody binding to the marker proteins and most specific binding to the brain antigens.

Human antibody response to a group B serotype 2a meningococcal vaccine determined by immunoblotting

The antibody response of 30 volunteers vaccinated with a complex of group B polysaccharide and outer membrane vesicles (OMV) from serotype 2a Neisseria meningitidis and of 3 individuals who received a placebo vaccine was determined by immunoblotting. OMV were separated by sodium dodecyl sulfate-gel electrophoresis and electrotransferred to nitrocellulose filters. Binding of immunoglobulin G (IgG), IgA, and IgM antibodies in the human sera to OMV components was detected with class-specific peroxidase-conjugated antibodies. The immunoblotting results were also related to the bactericidal activity of the sera and the meningococcal carrier status of the volunteers. Before vaccination weakly reactive bands in the molecular weight range of 140,000 to 10,000 were observed on the blots. Sera from carriers showed more marked bands. Individual patterns of increased reactivity were seen 6 weeks after vaccination. The main immunoreactive components of OMV corresponded to a molecular weight of 43,000 (class 1 protein), 30,000 (class 5 proteins), and 22,000. IgG antibodies in postvaccination sera of high bactericidal titers showed distinct binding to the 43,000-molecular-weight antigen. Meningococcal carriers had antibodies against an antigen of 22,000 molecular weight; in polyacrylamide gels this component did not stain with Coomassie brilliant blue or silver. The marked binding of IgG antibodies to the class 5 proteins decreased considerably between weeks 6 and 25 after vaccination. Periodate oxidation of OMV abolished the binding of IgG antibodies to the class 5 proteins, whereas the antigenicity of the 43,000-molecular-weight (class 1 protein) and 22,000-molecular-weight antigens was unaffected.

Characterization of an occult inhibitor to factor IX in a haemophilia B patient

Six haemophilia B patients were studied while undergoing infusion with factor IX concentrate. All were negative for factor IX antigen (IX:AG) and inhibitor to factor IX coagulant activity (IX:C). One patient showed an atypical response pattern, with prolonged survival of IX:C and IX:Ag. This patient remained under prophylactic treatment and more than 1 year later developed an inhibitor to IX:C of clinical significance. Retrospective study revealed that this patient had significantly higher levels of circulating immune complexes than other haemophilia B patients and in vivo formation of immune complexes containing IX:Ag prior to detection of his inhibitor in conventional clotting assays, suggesting long-term persistence of an occult inhibitor. The inhibitor was shown to be an IgG antibody with both kappa and lambda light chains.

Spontaneous disappearance of an IgA anti-factor IX inhibitor in a child with Christmas disease

The few inhibitors to blood coagulation factor IX in patients with Christmas disease (hemophilia B) that have been studied have been shown to belong to the IgG class of immunoglobulins. We report the first case in which a factor IX inhibitor was of the IgA class. Additionally, he appears to be the youngest patient with hemophilia B to have developed an inhibitor. His inhibitor complicated treatment of the patient for several years because of its anamnestic rise following factor IX concentrate administration. It then spontaneously vanished and has not returned in spite of repeated factor IX complex administration.

Human factor IX inhibitors: immunochemical characteristics and treatment with activated concentrate

Plasma was obtained from two patients with severe factor IX deficiency who had developed specific inhibitors of factor IX. Immunochemical characterization of the inhibitors by coagulation inhibitor neutralization assays and by immunoelectrophoretic methods demonstrated that both were IgG antibodies. One of the antibodies appeared to be monoclonal in origin with IgG subclass 4 heavy chains and lambda light chains. The other appeared to be oligoclonal and contained IgG subclass 1 and subclass 4 heavy chains and kappa and lambda light chains. One of the patients was treated with conventional, non-activated factor IX concentrate and with activated factor IX concentrate (Feiba) for repeated bleeding episodes. Administration of Feiba resulted in a progressive shortening of the kaolin cephalin clotting time and was followed by a good clinical response. Infusion of non-activated factor IX concentrate failed to induce clinical resolution of haemarthroses and had minimal effect on laboratory tests. The presence of circulating immune complexes could not be demonstrated in this patient.