0:00:00.000,0:00:06.000
(English captions by Andrea Matsumoto, University of Michigan.) The enzyme-linked immunosorbent assay or ELISA is a commonly used format for serologic testing.

0:00:06.000,0:00:13.000
The purpose of this animation is to explain[br]how this test works.

0:00:13.000,0:00:19.000
ELISA serologies are usually done in multi-well[br]microtiter plates so that dilutions of serum

0:00:19.000,0:00:21.000
can be easily prepared and tested.

0:00:21.000,0:00:26.000
To better understand how this assay is done,[br]lets take a closer look at what happens in

0:00:26.000,0:00:29.000
one of the wells of this assay plate.

0:00:29.000,0:00:33.000
To perform the assay, the wells are coated[br]with the antigen of interest.

0:00:33.000,0:00:38.000
For commercial tests, this would be done by[br]the manufacturer of the assay.

0:00:38.000,0:00:43.000
To begin testing, the wells are filled with[br]dilutions of the patient's serum.

0:00:43.000,0:00:47.000
If antibodies against the antigen are present[br]they will bind to the antigen fixed to the

0:00:47.000,0:00:49.000
bottom of the wells.

0:00:49.000,0:00:55.000
But only antigen specific antibodies will[br]bind to the wells.

0:00:55.000,0:00:59.000
The wells are then washed out to remove all[br]unbound antibodies.

0:00:59.000,0:01:05.000
Next a solution of an animal antibody against[br]human antibodies is added.

0:01:05.000,0:01:10.000
This second antibody is covalently conjugated[br]to an enzyme.

0:01:10.000,0:01:16.000
The wells are washed again, this time to remove[br]any unbound enzyme conjugated antibody.

0:01:16.000,0:01:21.000
Finally a solution of a colorgenic enzyme[br]substrate is added.

0:01:21.000,0:01:26.000
The interaction of the substrate with the[br]enzyme on the second antibody generates visible

0:01:26.000,0:01:27.000
color.

0:01:27.000,0:01:32.000
The development of color in the wells of the[br]specific antibody can be seen with the naked

0:01:32.000,0:01:37.000
eye or quantified with an electronic plate[br]reader.

0:01:37.000,0:01:42.000
The reaction is less intense as the serum[br]is diluted and the amount of antibody captured

0:01:42.000,0:01:44.000
in the wells decreases.

0:01:44.000,0:01:48.000
The titer is the highest dilution with definite[br]color development.