Técnica ELISA [Teoría y Práctica]

Elisa Technique: Theory and Practice

In this video, the Elisa technique is explored, focusing on its theory and practical application in detecting and quantifying substances like peptides, proteins, antibodies, and hormones. The acronym EIA stands for Enzyme-Linked Immunosorbent Assay.

Principles of Elisa

• The basic principles of the Elisa assay involve antigen immobilization on a solid phase followed by specific antibody binding.

• To amplify the antigen-antibody complex, a specific enzyme-linked antibody reacts with the complex to produce a measurable colored product.

Types of Elisa Assays

• Indirect assays enhance sensitivity by using a second antibody that amplifies the immune complex.

• These assays are crucial in diagnosing various infectious diseases by detecting antibodies produced by the body to combat them.

Applications of Elisa

• Elisa can detect HIV through anti-HIV antibodies in blood plasma.

• For detecting specific antigens like proteins, the sandwich Elisa technique is employed.

Practical Application of Direct Elisa

This section delves into the practical implementation of direct Elisa in serum samples to determine the presence or absence of a specific antibody (Antibody X).

Steps in Direct Elisa

• Coating involves absorbing antigen onto a solid phase followed by overnight incubation.

• Blocking prevents nonspecific interactions by adding an irrelevant protein to unoccupied areas on the solid phase.

Antigen-Antibody Reaction

• The sample is incubated with absorbed antigen; after washing, any unbound antibodies are removed.

• Amplification occurs as an enzyme-linked antibody reacts with bound antibodies for detection.

Practical Procedure Continuation

New Section

This section discusses the process of enzyme-linked immunosorbent assay (ELISA) and how the density of specific antibodies is measured.

Enzyme-Linked Immunosorbent Assay Process

• The final step involves the revelation where the antibody's conjugate enzyme reacts with an incolor substrate to convert it into a colored product.

• Measurement of optical density is done using a spectrophotometer, with the amount of specific antibodies against the immobilized antigen directly related to substrate conversion by the enzyme.

New Section

This part emphasizes the importance of running various controls during ELISA testing for accurate results.

Controls in ELISA Testing

• Essential controls include negative controls with known antibody absence and positive controls with serum containing the antibody.

• Running samples in wells without antigen helps account for non-specific binding sources like conjugate background and spontaneous conversion.

New Section

This segment highlights result analysis methods and interpretation techniques in ELISA testing.

Result Analysis in ELISA Testing

• Optical density is automatically subtracted as a blank from all wells for qualitative result analysis based on coloration presence, indicating specific antibodies against immobilized antigens.

• Quantitative analysis involves setting a cutoff point related to positive control density and creating curves with known serum dilutions to infer unknown sample antibody concentrations.