Turbidity of hyperimmune equine antivenom: the role of phenol and serum lipoproteins.

The article presents a study examining the cause of turbidity in polyvalent antivenom. It found that the interaction between freezing, high initial cholesterol and lipoprotein concentration, and the inclusion of phenol during serum fractionation contribute to this turbidity.

Study Objective and Methodology

• The research delved into the subject of turbidity (cloudiness or haziness in a fluid caused by microscopic particles) in various batches of polyvalent antivenom produced by the Instituto Clodomiro Picado.
• The researchers examined the antivenom before and after two processes: freezing-thawing and lyophilization (freeze-drying).
• A key intention behind this study was to figure out whether phenol, which is commonly used as a preservative during serum fractionation – the process of dividing or breaking up the serum, could lead to changes in lipoproteins (these are biomolecules composed of proteins and lipids) and eventually cause turbidity following freezing-thawing processes.
• To test this hypothesis, the team fractionated a sample of hyperimmune serum with different phenol concentrations, while one sample was fractionated without phenol.

Study Findings

• Eight batches of the antivenom became turbid after the freezing-thawing process. This observed change was found to correlate with high levels of cholesterol, triglycerides, and lipoproteins, particularly beta-lipoprotein.
• It was observed that normal horse serum, which inherently has high levels of lipoprotein, does not become turbid after freezing-thawing, which launched the theory that phenol might impact the lipoproteins and bring about turbidity after freezing-thawing.
• The result of the fractionation experiment showed that among the samples with identical cholesterol and triglyceride levels before fractionation, only the one with 0.25 g/dl phenol exhibited turbidity when subjected to freezing-thawing.
• It also contained a diffuse lipoprotein band on electrophoresis, which is a method used to separate and identify particles like proteins and nucleic acids.

Conclusion

• The research concluded that the occurrence of turbidity in equine antivenoms is due to the combination of three factors: freezing, the original high concentration of cholesterol and lipoprotein in the serum, and the addition of phenol during the fractionation of serum.