Quantification Neutralization病毒定量与中和课件.ppt

Virus Quantification Neutralization Introduction The hemagglutinin (HA) protein agglutinates erythrocytes (hence, the derivation of its name.) The hemagglutination inhibition (HAI) The method for identifying influenza field isolates Specific attachment of antibody to the antigenic sites on the HA molecule interferes with the binding between the viral HA and receptors on the erythrocytes. This effect inhibits hemagglutination and is the basis for the test. Originally described by Hirst (1942) and later modified by Salk (1944), is currently performed in microtiter plates. In general, a standardized quantity of HA antigen is mixed with serially diluted antisera, and red blood cells are added to determine specific binding of antibody to the HA molecule. Virus Quantification The most important property of a virus is its infectivity or ability to invade a cell and parasitize that cell to replicate itself. There are 2 basic types of infectivity assays, Quantal Assays: not count the number of infectious virus particles present in the inoculum but instead obtain a value for the virus titer. Ex) TCID50 (50% Tissue Culture Infective Dose), LD50 (50% Lethal Dose), EID50 (50% Egg Infective Dose) Quantitative Assays: The number of infectious virus particles present in the original suspension can be quantified. Ex) Plaque assays ? We will see this assay result by slide feature of microscope. Other properties Ex) Hemagglutination assay, Hemadsorption Hemagglutination Assay (HA) Hegagglutination is the aggregation of RBCs in the presence of hemagglutinating virus particles. This phenomenon is due to the presence of outer surface proteins on the hemagglutinating virus that recognize and attach to cellular surface receptors expressed by RBCs. Most common indirect methods for quantifying virus particles in suspension. Not a very sensitive assay since a large minimum number of virus particles are necessary to obtain macroscopic agglutination. It is convenient because of its rapid