Zoom in on microorganisms

A vaccine produced by genetic engineering? Why not!

Hepatitus B virus vaccine ZoomZoom (84KB)
© Illustration Nicole Catellier, Cinémanima inc.

Hepatitis B is a liver disease caused by HBV (hepatitis B virus). The vaccine developed to prevent infection by this virus consists of little bits of HBV that help the body defend itself against the whole virus. Production of this vaccine consists of producing HBV fragments... a case made to order for microorganisms!

The first hepatitis B vaccine consisted of virus fragments, isolated from sick individuals' blood, likely to be recognized by the body's defences. When administered to healthy people, these fragments allowed to the body to rapidly recognize the entire virus and eliminate it before it could cause infection. But this vaccination technique was not without its hazards. Despite purification procedures, a complete virus sometimes contaminated the vaccine resulting in a healthy person contracting the very disease the vaccine was meant to prevent! In addition, the use of infected individuals as the source of the vaccine presented practical difficulties. The development of a microorganism-based process to produce virus fragments was thus a welcome innovation.

How is the hepatitis B vaccine produced?
Today, the yeast Saccharomyces cerevisiae is used to produce hepatitis B vaccine. The gene (a segment of DNA strand) which controls the production of small HBV fragments is first inserted into the microorganism. The yeast then produces virus fragments which are subsequently collected, purified and used as a vaccine. Use of HBV-derived DNA segments eliminates the whole virus from the production process and reduces the risk of contamination to zero.