Human Immunoglobulins

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Chapter: Pharmaceutical Microbiology : The Manufacture And Quality Control Of Immunological Products

Human immunoglobulins are preparations of the immunoglobulins, principally immunoglobulin G (IgG) subclasses, that are present in human blood. They are derived from the plasma of donated blood and from plasma obtained by plasmapheresis.


HUMAN  IMMUNOGLOBULINS

 

A) Source Material

 

Human immunoglobulins are preparations of the immunoglobulins, principally immunoglobulin G (IgG) subclasses, that are present in human blood. They are derived from the plasma of donated blood and from plasma obtained by plasmapheresis. Normal immunoglobulin, that is immunoglobulin that has relatively low titres of antibodies representative of those present in the population at large, is prepared from pools of plasma obtained from not fewer than 1000 individuals. Specific immunoglobulins, that is immunoglobulins with a high titre of a particular antibody, are usually prepared from smaller pools of plasma obtained from individuals who have suffered recent infections or who have undergone recent immunization and who thus have a high titre of a particular antibody. Each contribution of plasma to a pool is tested for the presence of hepatitis B surface antigen (HBsAg), for antibodies to HIV 1 and 2 and for antibodies to hepatitis C virus in order to identify, and to exclude from a pool, any plasma capable of transmitting infection from donor to recipient. Donors who have been resident for 6 months or more in areas endemic for transmissible spongiform bovine encephalopathy (BSE), which currently includes the UK, are also excluded. The solventdetergent process, one of the methods used to inactivate enveloped viruses, uses treatment with a combination of tributyl phosphate and octoxinol 10; these reagents are subsequently removed by oil extraction or by solid phase extraction (British Pharmacopoeia, 2010).

 

B) Fractionation

  

The immunoglobulins are obtained from the plasma pools by fractionation methods that are based on ethanol precipitation in the cold with rigorous control of protein concentration, pH and ionic strength (Cohn et al., 1946). The variation of Kistler & Nitschmann (1962) is widely used. Some of the fractionation steps may contribute to the safety of immunoglobulins by inactivating or removing contaminating viruses that have not been detected by tests on the blood donations. The immunoglobulins may be presented either as a freeze-dried or a liquid preparation at a concentration that is at least 10 times that in the initial pooled plasma. Glycine may be added as a stabilizer. Multidose preparations contain an antimicrobial preservative but single-dose preparations do not (British Pharmacopoeia, 2010).

 

C) Quality Control

 

The quality control of immunoglobulins includes potency tests and conventional tests for safety and sterility. The potency tests consist of toxin or virus neutralization tests that parallel those used for the potency assay of immune sera, except that for in-process control of some immunoglobulins wider use is made of in vitro assays. In addition to the safety and sterility tests, total protein is determined by nitrogen estimations, the protein composition by sodium dodecyl sulphate (SDS)–polyacrylamide gel electrophoresis and molecular size by high performance liquid chromatography. The presence of immunoglobulins derived from species other than humans is excluded by precipitin tests. Table 24.4 lists six human immunoglobulins and their requisite potencies and indicates the methods by which the potencies are determined.


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