Immunologic responses of graft recipients to antilymphocyte globulin: effect of prior treatment with aggregate-free gamma globulin

Stability and Activity of the Hyperglycosylated Human Interferon-β R27T Variant

A hyperglycosylated recombinant human interferon-β (rhIFN-β) R27T mutant was established to improve relapsing-remitting multiple sclerosis (RRMS) in our previous study. We focused on the stability of the R27T mutant throughout its production lifetime, including culture, purification, and storage before formulation prior to clinical use. Herein, we address the stability of this protein during optimized culture and purification processes. Additionally, we employed artificial stress conditions during culture and purification to characterize R27T instability. Although, among total R27T, relative native R27T ratio displayed transiently low even under optimized production process, the ratio was recovered by the end of the overall production process, suggesting that culture and purification processes are optimized. Artificial stress during culture and purification processes resulted in degradation of R27T acidic and basic variants, and mismatched disulfide bonds in no-aggregated forms as well as in the aggregated form. The presence of disulfide bond exchange without aggregation in the unfolded/misfolded state could be a novel finding for rhIFN-β products. The results provide meaningful information for the comprehensive evaluation of the stability of the R27T variant.

Silicone Oil Microdroplets Can Induce Antibody Responses Against Recombinant Murine Growth Hormone in Mice

Therapeutic protein products can cause adverse immune responses in patients. The presence of subvisible particles is a potential contributing factor to the immunogenicity of parenterally administered therapeutic protein formulations. Silicone oil microdroplets, which derive from silicone oil used as a lubricating coating on barrels of prefilled glass syringes, are often found in formulations. In this study, we investigated the potential of silicone oil microdroplets to act as adjuvants to induce an immune response in mice against a recombinant murine protein. Antibody responses in mice to subcutaneous injections of formulations of recombinant murine growth hormone (rmGH) that contained silicone oil microdroplets were measured and compared to responses to oil-free rmGH formulations. When rmGH formulations containing silicone oil microdroplets were administered once every other week, anti-rmGH antibodies were not detected. In contrast, mice exhibited a small IgG1 response against rmGH when silicone oil-containing rmGH formulations were administered daily, and an anti-rmGH IgM response was observed at later time points. Our findings showed that silicone oil microdroplets can act as an adjuvant to promote a break in immunological tolerance and induce antibody responses against a recombinant self-protein.

In Vivo Analysis of the Potency of Silicone Oil Microdroplets as Immunological Adjuvants in Protein Formulations

Subvisible particles in a therapeutic protein product may act as adjuvants to promote unwanted immune responses against the protein. Silicone oil is used as a lubricant in prefilled syringes, and microdroplets of silicone oil are often detected in protein formulations expelled from prefilled syringes. In order to test the adjuvant potency of silicone oil microdroplets, antibody responses in mice to subcutaneous injections of formulations of ovalbumin (OVA) that contained silicone oil microdroplets were measured. These responses were compared against responses to oil-free OVA formulations and to OVA formulations that contained microparticulate aluminum hydroxide ("alum"), the common vaccine adjuvant. When administered with high concentrations of silicone oil microdroplets, OVA formulations elicited strong anti-OVA IgG1 and IgG2a antibody responses. These responses were equivalent to those observed when alum microparticles were added to OVA formulations, suggesting that silicone oil can act as a potent adjuvant. However, when OVA formulations were prepared with lower levels of silicone oil that had been obtained directly from commercial siliconized syringes, the anti-OVA antibody response was not enhanced significantly compared with responses against OVA alone.

Immunogenicity of different stressed IgG monoclonal antibody formulations in immune tolerant transgenic mice

The presence of protein aggregates in biopharmaceutical formulations is of great concern for safety and efficacy reasons. The aim of this study was to correlate the type and amount of IgG monoclonal antibody aggregates with their immunogenic potential. IgG degradation was obtained by freeze-thawing cycles, pH-shift cycles, heating, shaking and metal-catalyzed oxidation. The size, amount, morphology and type of intermolecular bonds of aggregates, as well as structural changes and epitope integrity were characterized. These formulations were injected in mice transgenic (TG) for human genes for Ig heavy and light chains and their non-transgenic (NTG) counterparts. Anti-drug antibody (ADA) titers were determined by bridging ELISA. Both unstressed IgG and freeze-thawed formulation did not induce measurable ADA levels. A mild antibody response was obtained in a fairly small percentage of mice, when injected with shaken, pH-shifted and heated formulations. The metal-catalyzed oxidized IgG formulation was the most immunogenic one, in both ADA titers and number of responders. The overall titers of NTG responders were significantly higher than the ones produced by TG mice, whereas there was no significant difference between the overall number of TG and NTG responders. This study reinforces the important role of protein aggregates on immunogenicity of therapeutic proteins and provides new insight into the immunogenic potential of different types of IgG aggregates. The results indicate that the quality of the IgG aggregates has more impact on the development of an immune response than their quantity or size.

Immunogenicity of protein aggregates--concerns and realities

Protein aggregation is one of the key challenges in the development of protein biotherapeutics. It is a critical product quality issue as well as a potential safety concern due to the increased immunogenicity potential of these aggregates. The overwhelming safety concern has led to an increased development effort and regulatory scrutiny in recent years. The main purposes of this review are to examine the literature data on the relationship between protein aggregates and immunogenicity, to highlight the linkage and existing inconsistencies/uncertainties, and to propose directions for future investigations/development.

The antigenic and immunosuppressive properties of normal and antilymphocytic equine IgG subfractions

The antigenic and immunosuppressive properties of normal and antilympho-cytic equine globulin subfractions were investigated in the rat model in an attempt to increase the efficacy of prolonged ALG therapy by limiting the immunogenic stimulus of `inactive' subfractions.

Chromatographic separation of equine IgG components yielded an electro-phoretically slow gamma 2 fraction consisting of IgG2a and IgG2b and a more heterogeneous fast gamma 1 subfraction. Immunosuppression resulting from the administration of isolated subfractions was measured by the response to alum-BSA and skin allograft survival. Antigenicity was determined by a variety of immunological procedures. The immunosuppressive character of the ALG was confined to the gamma 2 fraction, however this fraction also proved antigenic in our system.

The administration of normal equine IgG subfractions in combination with Freund's complete adjuvant resulted in the demonstration of antigenic differences between the fast and slow IgG components.

The immunogenic components of equine anti-human lymphocyte lobulin in renal allograft recipients

The antigenic components responsible for anti-ALG antibodies in the sera of ten human renal allograft recipients during ALG treatment have been evaluated. By sequential anion and cation exchange column chromatography, four ALG subfractions were demonstrated. In all cases, the antibodies were directed against the anodic components with relatively high hexose content. No precipitating antibodies were detected against the cathodic subfractions with low hexose content. Thus, the production and clinical use of pure cathodic γG-fractions of low antigenicity seems warranted.