Reverse Genetics
A flu virus contains eight gene segments. One of the gene segments codes for the surface antigen hemagglutinin (HA) and another codes for the surface antigen neuraminidase (NA).
Scientists can custom-make a flu strain by assembling genes that code for the desired features. Two genes representing the HA and NA antigens are selected from the target strain (flu strain 1), while the remaining six genes come from a virus that's time-tested for its ability to grow inside an egg (flu strain 2). (Although the influenza virus actually uses RNA as its genetic material, the researchers make complementary pieces of DNA because DNA is easier to work with.)
The illustration details the following steps in creating the vaccine:
- After removing the dangerous part of the HA gene, scientists splice the HA and NA genes from flu strain 1 into circular pieces of DNA called plasmids.
- Additional plasmids are created using the remaining six genes found in flu strain 2.
- Scientists insert the HA and NA plasmids from flu strain 1 and the six plasmids carrying genes from flu strain 2 into animal cells growing in the laboratory.
- The genes in the plasmids instruct the animal cells to make the desired new flu strain
Credit: This image is in the public domain. Please credit the National Institute of Allergy and Infectious Diseases (NIAID).
Illustrator: Links Studio.
Download: high resolution version of the Reverse Genetics illustration.
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