Aim: To investigate the stability of the anti-pneumococcal (PCP) and anti-haemophilus type B (Hib) immunoglobulins (IgGs) in human IgG-depleted serum samples frozen at -20°C. Materials & methods: Modified commercially available immunoassays (ELISAs) were bioanalytically validated. These ELISAs were used to measure levels of the two anti-bacterial IgG in samples kept at -20°C for up to 15 months. Human IgG-depleted serum was spiked with GAMMAGARD Liquid to obtain those samples. Results: Both ELISAs passed the validation test. Anti-PCP IgG and anti-Hib IgG were shown to be stable for at least 15 months at -20°C. Conclusion: These data confirm the stability of anti-bacterial IgG in human IgG-depleted serum and support the common practice of testing frozen samples.
Keywords: GAMMAGARD Liquid/KIOVIG; analytical method validation; anti-hemophilus influenza immunoglobulin G; anti-pneumococcal immunoglobulin G; enzyme-linked immunosorbent assay; immunoglobulin replacement therapy; intravenous immunoglobulin preparation; primary immunodeficiency; stability of anti-bacterial immunoglobulins.
Immunodeficiency disorders can prevent your body from fighting infections. These disorders make it easier to catch viruses and bacterial infections caused by so-called pathogens. Patients suffering from immunodeficiencies are treated throughout their lives with antibodies purified from human plasma. This immunoglobulin replacement therapy, which helps to avoid infections, provides specific antibodies directed against these pathogens. An antibody is a protein produced by the body's immune system to detect (bind) antigens and to help eliminating harmful substances. Little is known about the stability of such specific antibodies in samples taken from patients during clinical studies carried out to improve the replacement therapy. We investigated the stability of two such antibodies using a standard technique for their measurement. In a process termed validation, these methods were demonstrated to deliver accurate and precise results. For the stability study, we prepared human serum (= the liquid part of human blood) samples with specific antibodies levels expected in samples from patients on replacement therapy. These samples were kept frozen at -20°C for up to 15 months. The data obtained on analysis of the frozen samples showed the adequate stability of both antibodies directed against important pathogen. This stability confirms a common testing practice applied for samples obtained in clinical studies where usually such samples are not tested immediately but are stored frozen and tested in batches. In particular, the data for the two anti-bacterial antibodies support the storage of such samples for at least 15 months at -20°C before testing.