The
haemagglutination assay is a method used to measure virus particle. This assay takes advantage of the fact that many viruses contain the two spike proteins: Neuraminidase and Haemagglutinin that blinds specifically to the red blood cells. Examples of viral protein with ability to bind to red blood cells are influenza virus and other virus.
Haemagglutination inhibition is whereby one measures the ability of soluble antigen to inhibit the aggulutination of antigen coated red blood cells by antibodies. The neutralisation of virus inhibits agglutination. Virus neutralisation is a method where antibodies are added to a virus preparation and the infectivity of this preparation is then measured using indicator cells. A subset of antibodies produced against any given virus will have the ability to neutralize the infectivity of the virus. These antibodies have the ability to neutralize the infectivity of virus; it prevents or lowers the virus infectivity.
Complement fixation is a test that is used to detect the presence of either specific antibody or specific antigen in a patient’s serum. If the antibody is present in the patient’s serum, it binds to the antigen and complement reagent is completely consumed in the reaction. The antibody bound to cellà complement bindingàcomplement cascadeà cell lysis. The complement of cascade of molecules in blood serum initiated causing lysis of infected cell or pathogen.
Immunofluorescence is where antibodies or antigen are tagged with fluorescent dyes.
This method usually uses two sets of antibodies whereby a primary antibody is used against the antigen of interest and follow by a secondary, dye-coupled antibody is introduced which recognizes the primary antibody. Under immunofluorescene, there are direct fluorescent-antibody (FA) technique and indirect fluorescent-antibody (IFA) technique.
-The antibody attached specifically to antigen.
-The specimen is viewed under exciting light using fluorescence microscope.
Immunogold electron microscopy has the same principle as immunoflourscence. However, instead of staining the antibodies with fluorescent dyes, gold particles (nano sized) are attached to the antibodies. The specimen is then viewed under electron microscope to localise specific proteins or antigens.
Immunoblot and immunoprecipitation are methods that allow one to detect specific viral proteins in lysates from infected tissues or cells.
In immunoprecipitation, the antigen is radioactively labelled. The cells are then lysed and the labelled antigne are precipitated out of solution using a specific antibody. The antibody-antigen complex is then isolated for analysis by SDS-polyacrylamide gel electrophoresis (SDS-PAGE). It is then detected through x ray film.
In immunoblot also known as western blog analysis, the proteins are not prelabeled with radioactivity instead the whole protein sample is subjected to SDS-PAGE, so as to separate out the proteins on the basis of their size and other physical properties. The proteins are then transfer to nitrocellulose membrane, the membrane can then be probed with specific antibodies follow up, the antibodies is labelled with sensitive indicator (e.g. horse radish peroxidise).
Enzyme-linked immunosorbent assay also known as ELISA is biochemical technique used mainly in immunology that used an enzyme to detect the building of antigen (Ag) and antibodies (Ab). The colourless substrate was converted to a coloured product by the enzyme and this indicates the presence of Ag: Ab binding.
Generally, there are 5 types of ELISA:
-Direct ELISA
-Indirect ELISA
-Sandwich ELISA
-Competitive ELISA
-Multiplex ELISA
Detection, identification and diagnosis of virus
The haemagglutination assay is a method used to measure virus particle. This assay takes advantage of the fact that many viruses contain the two spike proteins: Neuraminidase and Haemagglutinin that blinds specifically to the red blood cells. Examples of viral protein with ability to bind to red blood cells are influenza virus and other virus. 