ENZYME LINKED IMMUNOSORBENT ASSAY- ELISA

       Enzyme Linked Immunosorbent Assay (ELISA)

 ✓ Direct ELISA – Detects antigens

✓ Indirect ELIA – Detects antibodies

✓ Microtiter plates with numerous shallow wells used

✓ Popular as require little interpretive skills. Results clearly positive or negative

✓ Highly automated procedures

✓ E.g. Home pregnancy test

Positive direct ELISA to detect antigens

✓ To detect presence of drugs in urine

✓ Ab specific to drug absorbed on micro titre plate.

✓ Patient’s urine sample added to well , any of the drug it contained would bind to antibody and is captured

✓ Well rinsed to remove unbound drug.

✓ More Ab specific to drug added to make visible test. Ab with enzyme attached to them are added

✓ A sandwich of antibody/drug/enzyme-linked Ab formed.

✓ On addition of substrate for linked enzyme, visible colour produced

Positive Indirect ELISA to detect Antibodies

  

✓ To screen blood for antibodies to HIV.

✓  Microtiter plate contains Ag, such as inactivated virus that causes disease the

     test is designed to diagnose

✓ A sample of patient’s blood added to well. If it has specific Ab it will react with virus. 
✓ Rinse well to remove unbound Ab

✓ To make test visible- anti-HISG linked to enzyme added

✓ Positive test contains virus/ Ab/ enzyme linked ant-HISG sandwich

✓ On addition of substrate for linked enzyme, visible colour produced

                                                                                   - Ms. Tosha Pandya
                                                                                     Asst. Professor LJIP