Investigation of whether the acute hemolysis associated with Rh(o)(D) immune globulin intravenous (human) administration for treatment of immune thrombocytopenic purpura is consistent with the acute hemolytic transfusion reaction model

Impact of human leucocyte antigen class II polymorphism on anti-red blood cell antibody development: Correlations and indications

BACKROUND AND OBJECTIVES

Blood transfusion therapy is vital for many patient groups. They can cause many complications, and the development of anti-red blood cell (RBC) antibodies is of significant importance. Molecules of class II human leucocyte antigens (HLA) are one of the several factors that influence antibody development in patients.

MATERIALS AND METHODS

In this study, we investigated 108 patients who developed antibodies against different erythrocyte antigens and 115 patients on multiple transfusion therapies who did not develop anti-RBC antibodies. The HLA loci HLA-DRB1 and HLA-DQB1 were typed using commercial molecular assays routinely used in HLA laboratories.

RESULTS

An increased frequency of the HLA-DRB1*04 allele group was observed in patients who developed antibodies. Additionally, HLA-DRB1*09 was also significant for anti-E development and in patients with multi-specific alloimmunization. It was found that the HLA-DRB1*07 allele group is associated with antibodies to antigents of the Rh and MNS systems but also lacks an association with anti-K development. The HLA-DRB1*11 and -DRB1*01 allele groups displayed a protective mechanism for anti-E development, similar to that of HLA-DQB1*02 for anti-K.

CONCLUSION

There is an association between various HLA class II alleles and anti-RBC development.

An optimized microplate-based method to evaluate complement-dependent hemolysis mediated by intravenous immunoglobulins (IVIG)

Hemolytic reactions can cause serious complications after administration of Intravenous Immunoglobulin (IVIG), due to passive transfer of anti-A and anti-B IgG antibodies (isoagglutinins). A maximum allowable amount of isoagglutinins is established in the US and EU for licensed IVIG, as measured by a specified direct hemagglutination test (DHAT). Despite this limit, reports of hemolysis have increased over time, raising the question of how well the DHAT predicts clinically significant hemolysis. This study was undertaken to develop a microplate-based complement-dependent hemolysis assay (CDHA) that reproducibly measures functional hemolytic activity of IVIG, for assessment of IVIG products. An IVIG working reference reagent (NIBSC 14/160) was qualified as an assay control and for quantitation purposes. Hemolytic activities of 36 IVIG product lots encompassing seven brands and including 6 clinically hemolytic lots were measured. Hemolytic activity varied among IVIG product brands, and to a lesser extent, from lot-to-lot for individual brands. Correlation between the CDHA and DHAT was not robust which may reflect imprecision of the DHAT method or additional variables that influence complement-dependent hemolysis after opsonization. In conclusion, the CDHA provides a simple, specific, and sensitive tool for IVIG product characterization and investigation of hemolytic events by manufacturers, researchers, and regulatory authorities.

Treatment of primary and secondary immune thrombocytopenia

PURPOSE OF REVIEW

Medical therapies for the treatment of immune thrombocytopenia (ITP) complicating SLE are increasingly being investigated as alternatives to splenectomy and IVIG. The purpose of this review is to highlight the therapies that are utilized in the treatment of primary ITP and ITP secondary to lupus.

RECENT FINDINGS

Corticosteroids are still the standard initial treatment of ITP, with the addition of IVIG when a rapid response is needed. There are few studies dedicated to assessing the efficacy of disease-modifying antirheumatic (DMARD), biologic, and nonimmunosuppressive agents as treatment for lupus thrombocytopenia/lupus ITP. Rituximab and thrombopoeitin mimetics have been the most extensively studied therapies for primary ITP in recent years. Results of trials show adequate initial responses; however, the duration of therapy and sustainability of responses are variable. Splenectomy is less often utilized.

SUMMARY

Although corticosteroids, intravenous immunoglobulin and splenectomy have proven to be effective measures to treat immune thrombocytopenia, newer studies have demonstrated positive outcomes of immunosuppressives and thrombopoeitin mimetics. In most cases, the reported duration of therapy was not prolonged. More studies are needed to fully assess the effect of medical therapy in lupus ITP and to determine how long to continue maintenance therapy.

Development of RBC Membrane Antigen Arrays for Validating Blood Grouping Reagents

Antibody reagents have been remained as a standard approach to characterize blood group (BG) antigens in clinic. The specificity and cross-reactivity of these BG antibodies are routine detected using the gel microcolumn assay (GMA). However, the GMA is neither specific nor sensitive, thus increasing the risk of improperly matched RBC transfusions. In this work, we describe a bead-based RBC membrane antigen array to detect BG antibody-antigen binding with ∼700-fold higher sensitivity and dynamic range than the GMA. RBC membrane antigen arrays were fabricated using fragmented RBC membranes highly enriched in BG panel antigens. The arrays were then used to screen the interactions of 15 BG reagents to three antigen panels. The majority of the antibody reactions (i.e., 86.7%; 39/45) aligned with those obtained with the GMA. The six cross-reactive, nonspecific antibody reactions identified only by our arrays (i.e., 13.3%; 6/45) were confirmed by agglutination inhibition and genotyping assays. These results demonstrate that our RBC membrane antigen array has great potential in screening BG antibodies and improving the safety of RBC transfusions.

Different dosages of intravenous immunoglobulin (IVIg) in treating immune thrombocytopenia with long-term follow-up of three years: Results of a prospective study including 167 cases

This study compared the effects of different dosages of intravenous immunoglobulin (IVIg) against immune thrombocytopenia (ITP). A total of 167 patients, 91 adults and 76 children, with ITP, followed-up for three years in the case-control study, were divided into three subgroups according to the dosages of IVIg administered: group A (0.2 g/kg/day), group B (0.3 g/kg/day) and group C (0.4 g/kg/day). The therapeutic response in 91 adult patients did not differ significantly among the three groups of IVIg dosages (p = 0.459). The response rate of IVIg treatment in the three adult groups was 97.1% for group A, 97.2% for group B and 100% for group C. The mean time for raising platelets to 30 × 10(9)/L in group A was 2.5 days, group B 3.2 days and group C 2.9 days (p = 0.324). The median IVIg consumption in group A was 0.83 g/kg, group B 1.22 g/kg and group C 1.64 g/kg (p < 0.01). Similar results were shown in the children groups. The follow-up results showed no significant difference of clinical outcome between groups A, B and C. In conclusion, low-dose IVIg treatment is shown to be as effective as high-dose regimen without increasing the risk of developing the patients into chronic ITP conditions, suggesting that ITP patients could be treated more cost-effectively by lower conventional dosage of IVIg regimen.

Rozrolimupab, a mixture of 25 recombinant human monoclonal RhD antibodies, in the treatment of primary immune thrombocytopenia

Rozrolimupab, a recombinant mixture of 25 fully human RhD-specific monoclonal antibodies, represents a new class of recombinant human antibody mixtures. In a phase 1 or 2 dose escalation study, RhD(+) patients (61 subjects) with primary immune thrombocytopenia received a single intravenous dose of rozrolimupab ranging from 75 to 300 μg/kg. The primary outcome was the occurrence of adverse events. The principal secondary outcome was the effect on platelet levels 7 days after the treatment. The most common adverse events were headache and pyrexia, mostly mild, and reported in 20% and 13% of the patients, respectively, without dose relationship. Rozrolimupab caused an expected transient reduction of hemoglobin concentration in the majority of the patients. At the dose of 300 μg/kg platelet responses, defined as platelet count ≥ 30 × 10(9)/L and an increase in platelet count by > 20 × 10(9)/L from baseline were observed after 72 hours and persisted for at least 7 days in 8 of 13 patients (62%). Platelet responses were observed within 24 hours in 23% of patients and lasted for a median of 14 days. Rozrolimupab was well tolerated and elicited rapid platelet responses in patients with immune thrombocytopenia and may be a useful alternative to plasma-derived products. This trial is registered at www.clinicaltrials.gov as #NCT00718692.

RhIG for the treatment of immune thrombocytopenia: consensus and controversy (CME)

Anti-D immune globulin (RhIG) is a front-line option in North America for the treatment of immune thrombocytopenia (ITP) in children and adults. Recently, addition of a Food and Drug Administration-mandated black box warning highlighted the risks of intravascular hemolysis, renal failure, and disseminated intravascular coagulation after anti-D infusion, prompting concern within the medical community regarding its use. A working group convened in response to this warning to prepare a consensus document regarding the safety of RhIG because there has been no increased incidence of adverse events since the initial discovery of these reactions many years ago. The efficacy of anti-D is well documented and only briefly reviewed. The estimated incidence and proposed mechanisms for the rare, major treatment-related complications are discussed, and signal detection data associated with heightened risk of acute hemolytic reactions are presented. The importance of considering host factors, given the rarity of severe reactions, is emphasized. Safety profiles of parallel treatment options are reviewed. The working group consensus is that RhIG has comparable safety and efficacy to other front-line agents for the treatment of children and adults with ITP. Safety may be further improved by careful patient selection.