Method for evaluating the neuraminidase activity of receptor-destroying enzyme (RDE) compounds using the influenza virus

Abstract

Introduction. The classic hemagglutination inhibition reaction (RTGA) is used to determine the level of antiviral antibodies in human and animal serum specimens. During the performance of RTGA the tested sera must be treated with a receptor-destroying enzyme (RDE) to remove serum glycans that degrade the accuracy of the RTGA results. To optimize the amounts of RDE compounds used, it is necessary to know their real neuraminidase activity. This article describes a simple and economical method for testing the neuraminidase activity of receptor-destroying compounds using standard reagents and laboratory equipment.Aims of investigation. Design of an improved simple and convenient method for evaluating the neuraminidase activity using the flu virus.Material and methods. Here, we propose a convenient method for evaluating the activity of neuraminidase by double-fold dilution procedure with human or animal erythrocytes followed by hemagglutination assay with influenza A virus.Results and discussion. The method is based on the ability of neuraminidase to hydrolyze sialic acid residues on the cell surface of erythrocytes, that deprives red blood cells to be agglutinated with the flu virus, since these sialic glycans provide virus attachment and hemagglutination.Conclusion. The designed method allows the accurate measurement of the receptor-destroying (neuraminidase) activity of RDE compounds and the comparison of the compounds with each other. This test is necessary to optimize the RTGA protocol when monitoring blood sera of animals and humans after influenza infection and/or Acute Respiratory diseases (ARD). The designed method can be included in the guidelines of regulations for the RTGA protocol, which is used in different laboratories to monitor the epidemic process of influenza and ARD infections.