Using bispecific antibodies in forced degradation studies to analyze the structure-function relationships of symmetrically and asymmetrically modified antibodies

Forced degradation experiments of monoclonal antibodies (mAbs) aid in the identification of critical quality attributes (CQAs) by studying the impact of post-translational modifications (PTMs), such as oxidation, deamidation, glycation, and isomerization, on biological functions. Structure-function characterization of mAbs can be used to identify the PTM CQAs and develop appropriate analytical and process controls. However, the interpretation of forced degradation results can be complicated because samples may contain mixtures of asymmetrically and symmetrically modified mAbs with one or two modified chains. We present a process to selectively create symmetrically and asymmetrically modified antibodies for structure-function characterization using the bispecific DuoBody® platform. Parental molecules mAb1 and mAb2 were first stressed with peracetic acid to induce methionine oxidation. Bispecific antibodies were then prepared from a mixture of oxidized or unoxidized parental mAbs by a controlled Fab-arm exchange process. This process was used to systematically prepare four bispecific mAb products: symmetrically unoxidized, symmetrically oxidized, and both combinations of asymmetrically oxidized bispecific mAbs. Results of this study demonstrated chain-independent, 1:2 stoichiometric binding of the mAb Fc region to both FcRn receptor and to Protein A. The approach was also applied to create asymmetrically deamidated mAbs at the asparagine 330 residue. Results of this study support the proposed 1:1 stoichiometric binding relationship between the FcγRIIIa receptor and the mAb Fc. This approach should be generally applicable to study the potential impact of any modification on biological function.

[Importance of prolactinemia and IgA-transferrin ratio in chronic alcoholism and alcoholic hepatopathies]

Levels of prolactinaemia, IgA and transferrin and the ratio between the two latter were measured in 20 male chronic alcoholics and a second group of controls in order to verify the diagnostic importance of such measurements. In partial conflict with reports in the literature, it is concluded that prolactinaemia measurement is not particularly important. The evaluation of the IgA-transferrin ratio, on the other hand, is judged to be useful for the diagnosis of alcohol-induced hepatopathologies.

[Significance of concentrations and ratio of immunoglobulin G and M in the evaluation of anti-Toxoplasma IGM]

The Authors have tested the significance of the correlation of the mean total IgM concentration, the IgG: IgM ratio and the presence of specific anti-Toxoplasma gondii IgM, determined with different serological reactions. The piece of research has been carried out on 72 samples of subjects with active toxoplasmic infections.

[Anti-toxoplasma antibody titers and immunoglobulins]

285 sera from parturient patients have been tested for the presence of anti-toxoplasma antibodies by the direct Agglutination test and for Immunoglobulins by the immunochemical turbidimetric determination. 17 sera showed a significant increase in the titre of anti-toxoplasma antibodies; 5 of these 17 presented a simultaneous IgM level increase, subsequently confirmed by a 2 Mercaptoethanol pretreatment, this fact suggesting the presence of active infectious disease. The authors think it can be useful in the diagnostic assessment of active toxoplasmic infectious disease the simultaneous screening of sera by the two described methods: the direct Agglutination test and the immunochemical turbidimetric determination.