Cells function as vaccine factories

1

In some vaccines such as HPV, scientists isolate the genes that hold the code for the portion of the virus which the immune system can recognize.

2

The gene is transplanted into a ring-shaped DNA molecule (plasmid) from a harmless bacterium.

3

The plasmid with the virus genes is injected into a yeast cell, which immediately starts to produce empty copies of the virus shell without the genes that cause disease.

4

The harmless virus shells are harvested, cleansed, and injected into the body. The immune system starts to produce antibodies, which combat the virus efficiently, if the person encounters it again.