Question

Which technique is of great value when it is necessary to discriminate between antibodies produced in response to vaccination and those produced in response to infection.

• A. Enzyme linked Immuno sorbent assay
• B. Radio Immuno Assay
• C. Western Blot immune assay
• D. Flow cytometry

Hint:

This concept is known as the DIVA strategy (Differentiating Infected from Vaccinated Animals).
The companion diagnostic test is always a specialized ELISA designed to detect antibodies against the deleted gene product of the marker vaccine.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Differentiating Infected from Vaccinated Animals (DIVA) is a critical strategy in veterinary disease eradication and surveillance programs.
This strategy relies on the use of marker (or deleted) vaccines alongside a companion diagnostic test that can specifically distinguish between the two types of immune responses.

Step 2: Detailed Explanation:
Marker vaccines are engineered by deleting a specific, non-essential gene encoding an immunogenic protein of the pathogen (for example, deleting the glycoprotein E gene in Aujeszky's disease virus, or the NS1 protein gene in Foot-and-Mouth Disease virus).
Animals vaccinated with this marker vaccine will produce antibodies against all viral proteins *except* the deleted protein.
In contrast, animals infected with the wild-type virus will mount an immune response and produce antibodies against all viral proteins, including the deleted protein.
To screen herds, a companion Enzyme-Linked Immunosorbent Assay (ELISA) (A) (specifically a DIVA or blocking ELISA) is developed.
This ELISA is coated with the deleted protein antigen.
If a serum sample contains antibodies that bind to this specific antigen, it indicates the animal has been exposed to the wild-type pathogen (infection).
If no antibodies are detected against this specific antigen, but the animal is positive for other viral antibodies, it indicates the animal was vaccinated.
ELISAs are highly automated, rapid, cost-effective, and provide excellent sensitivity and specificity for large-scale herd screening, making them the premier diagnostic choice for this purpose.

Step 3: Final Answer:
The diagnostic technique of great value for discriminating between vaccination and infection antibodies is the Enzyme-linked immunosorbent assay (ELISA).