Protein A-immunoadsorption (Prosorba® column) in the treatment of rheumatoid arthritis

Therapeutic apheresis in kidney diseases: an updated review

Besides conventional medical therapies, therapeutic apheresis has become an important adjunctive or alternative therapeutic option to immunosuppressive agents for primary or secondary kidney diseases and kidney transplantation. The available therapeutic apheresis techniques used in kidney diseases, including plasma exchange, double-filtration plasmapheresis, immunoadsorption, and low-density lipoprotein apheresis. Plasma exchange is still the leading extracorporeal therapy. Recently, growing evidence supports the potential benefits of double-filtration plasmapheresis and immunoadsorption for more specific and effective clearance of pathogenic antibodies with fewer side effects. However, more randomized controlled trials are still needed. Low-density lipoprotein apheresis is also an important supplementary therapy used in patients with recurrent focal segmental glomerulosclerosis. This review collects the latest evidence from recent studies, focuses on the specific advantages and disadvantages of these techniques, and compares the discrepancy among them to determine the optimal therapeutic regimens for certain kidney diseases.

Staphylococcal protein A-formulated immune complexes suppress enterotoxin-induced cellular responses in nasal polyps

BACKGROUND

Recent studies have revealed that Staphylococcus aureus and its components participate in the pathogenesis of eosinophilic airway diseases, such as chronic rhinosinusitis with nasal polyps.

OBJECTIVE

We sought to determine whether staphylococcal protein A (SpA) from S aureus regulated cellular responses in nasal polyps, especially when coupled to immunoglobulins in immune complexes (ICs).

METHODS

Dispersed nasal polyp cells (DNPCs) or peripheral blood monocytes were cultured in vitro with SpA in the presence or absence of IgG, and IL-5, IL-13, IFN-γ, IL-17A, and IL-10 levels were measured in the supernatants. The effect of SpA exposure on staphylococcal enterotoxin B-induced cytokine production by DNPCs in the presence and absence of IgG, IgA, and autologous serum was also examined.

RESULTS

Exposure to SpA induced DNPCs to produce significantly higher IL-10, IL-13, and IL-17A levels than DNPCs without SpA, although the magnitude of the IL-17A increase was less than that of IL-10 and IL-13. SpA induced IL-10 production mainly from adherent DNPCs, and this was significantly enhanced in the presence of IgG; similar results were observed in peripheral blood monocytes. IC formation between SpA and IgG (SpA-IgG ICs) was confirmed by using native polyacrylamide gel electrophoresis. SpA-IgG ICs, but not SpA alone, almost completely suppressed staphylococcal enterotoxin B-induced IL-5, IL-13, IFN-γ, and IL-17A production by DNPCs; similar inhibition was observed in DNPCs treated with SpA in the presence of either IgA or autologous serum.

CONCLUSIONS

Our results suggest that SpA can regulate the pathogenesis of enterotoxin-induced inflammation in patients with chronic rhinosinusitis with nasal polyps through coupling to immunoglobulins.

In vitro molecular evolution yields an NEIBM with a potential novel IgG binding property

Staphylococcus aureus protein A (SpA) and protein G of groups C and G streptococci (SpG) are two well-defined bacterial immunoglobulin (Ig)-binding proteins (IBPs) with high affinity for specific sites on IgG from mammalian hosts. Both SpA and SpG contain several highly-homologous IgG-binding domains, each of which possesses similar binding characteristic of the whole corresponding proteins. Whether specific combinations of these domains could generate a molecule with novel IgG-binding properties remained unknown. We constructed a combinatorial phage library displaying randomly-rearranged A, B, C, D and E domains of SpA as well as the B2 (G2) and B3 (G3) domains of SpG. In vitro molecular evolution directed by human, rabbit, bovine, or goat polyclonal IgGs and four subclasses of mouse monoclonal IgGs generated one common combination, D-C-G3. A series of assays demonstrated that D-C-G3 exhibited a potential novel IgG binding property that was obviously different from those of both parent proteins. This study provides an example of successful protein engineering through in vitro molecular evolution and useful approaches for structure and function studies of IBPs.

Co-opting endogenous immunoglobulin for the regulation of inflammation and osteoclastogenesis in humans and mice

OBJECTIVE

Cells of the monocytic lineage play fundamental roles in the regulation of health, ranging from the initiation and resolution of inflammation to bone homeostasis. In rheumatoid arthritis (RA), the inflamed synovium exhibits characteristic infiltration of macrophages along with local osteoclast maturation, which, together, drive chronic inflammation and downstream articular destruction. The aim of this study was to explore an entirely novel route of immunoglobulin-mediated regulation, involving simultaneous suppression of the inflammatory and erosive processes in the synovium.

METHODS

Using in vivo and in vitro studies of human cells and a murine model of RA, the ability of staphylococcal protein A (SPA) to interact with and modulate cells of the monocytic lineage was tested. In addition, the efficacy of SPA as a therapeutic agent was evaluated in murine collagen-induced arthritis (CIA).

RESULTS

SPA showed a capacity to appropriate circulating IgG, by generating small immunoglobulin complexes that interacted with monocytes, macrophages, and preosteoclasts. Formation of these complexes resulted in Fcγ receptor type I-dependent polarization of macrophages to a regulatory phenotype, rendering them unresponsive to activators such as interferon-γ. The antiinflammatory complexes also had the capacity to directly inhibit differentiation of preosteoclasts into osteoclasts in humans. Moreover, administration of SPA in the early stages of disease substantially alleviated the clinical and histologic erosive features of CIA in mice.

CONCLUSION

These findings demonstrate the overarching utility of immunoglobulin complexes for the prevention and treatment of inflammatory diseases. The results shed light on the interface between immunoglobulin complex-mediated pathways, osteoclastogenesis, and associated pathologic processes. Thus, therapeutic agents designed to harness all of these properties may be an effective treatment for arthritis, by targeting both the innate inflammatory response and prodestructive pathways.

Guidelines on the use of therapeutic apheresis in clinical practice--evidence-based approach from the Apheresis Applications Committee of the American Society for Apheresis

The American Society for Apheresis (ASFA) Apheresis Applications Committee is charged with a review and categorization of indications for therapeutic apheresis. Beginning with the 2007 ASFA Special Issue (fourth edition), the subcommittee has incorporated systematic review and evidence-based approach in the grading and categorization of indications. This Fifth ASFA Special Issue has further improved the process of using evidence-based medicine in the recommendations by refining the category definitions and by adding a grade of recommendation based on widely accepted GRADE system. The concept of a fact sheet was introduced in the Fourth edition and is only slightly modified in this current edition. The fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis. The article consists of 59 fact sheets devoted to each disease entity currently categorized by the ASFA as category I through III. Category IV indications are also listed.

Translating basic research into clinical rheumatology

Findings from basic research in combination with precise clinical observations of the disease course in rheumatoid arthritis (RA) have led to the development of a multistage model to explain the pathophysiology of RA. Different cellular and soluble mediators, which play principal roles at different phases of the disease, have been identified. New therapeutic agents, which specifically target these factors, now allow us to intervene at several levels of the pathogenesis. This has already resulted in significant improvements for patients suffering from RA, and the development of new promising agents continues at a high pace. However, many questions concerning the optimal use of the new therapies remain unanswered. Combined efforts of basic research and clinical trials investigating the optimal timing and combination of the new treatments will be necessary to allow them to achieve their full potential and to result in the maximum benefit for patients.

Serum immunoglobulins and risk of infection: how low can you go?

OBJECTIVES

To determine the relationship between the levels of serum immunoglobulin (Ig) levels and risk of infection. The following 2 main questions are addressed: (1) At what level do reduced serum concentrations of the different Ig species (focusing on IgA, IgG, and IgM) significantly increase the risk of infection above background and (2) For how long can Ig depletion be tolerated before an increased risk of infection becomes apparent.

METHODS

Information was gathered from a search of PubMed and relevant congress abstracts up to and including November 2007.

RESULTS

Sustained, very low levels of IgA, IgG, or IgM, as occur in primary immunodeficiency syndromes, are associated with significantly increased risks of infections, primarily respiratory tract infections of bacterial origin. Patients with IgG levels <100 mg/dL or IgM levels <20 mg/dL for prolonged periods have an increased risk of recurrent and sometimes life-threatening infectious episodes. Generally, IgA deficiency appears better tolerated. Replenishment of IgG in patients with hypogammaglobulinemia reduces the infection risk to background if IgG levels are maintained at approximately 500 mg/dL, although higher levels may be necessary in the presence of certain comorbidities. Transient depletion of IgG and/or IgM (or, less commonly, IgA) can occur in some patients following the administration of certain drugs, including anticonvulsants, corticosteroids, and rituximab. Available evidence suggests that such changes are not generally associated with an increased risk of infections.

CONCLUSIONS

While prolonged, very low levels of IgG and/or IgM are associated with a heightened risk of infections, transient or less severe immunodeficiency appears to be tolerated in most subjects.

Plasma exchange for rheumatoid arthritis

Rheumatoid arthritis (RA) is the most common inflammatory joint disease. Even though, physiopathology of rheumatoid arthritis remains unclear, the presence of circulating immune complexes and rheumatoid factors had led to the use of plasma exchange (PE). Even though PE procedures have evolved over the last decades, their indications and use in RA must be replaced in the context of the evolution of disease-modifying anti-rheumatic drugs. Results of PE and leukapheresis were disappointing in patients with severe and resistant RA. Conversely, immunoadsorption, and particularly over a Staphylococcus aureus protein A column, has resulted in some good responses in refractory RA patients. But, the emergence of effective biologics has clearly restrained their use and limited their indications to some rare patients with refractory and severe RA.