Tuesday, September 02, 2014
   
TEXT_SIZE

Virosome: a vehicle for vaccines

A vaccine is a biological preparation that improves immunity to a particular infectious microorganism (microbe). A vaccine typically contains a small amount of an agent (immunogen) that resembles a microorganism. Upon administration, the immunogen stimulates the body's immune system to recognize it as foreign, destroy it, and "remember" it. Consequently, the immune system can more easily recognize and destroy or neutralize the correspondent microorganism that it later encounters, thereby avoiding severe infection and subsequently, pathologies.
The immunogen is made up of some parts of the microbe, as proteins, which are seen by the immune system as the microbe itself. This immunogen usually needs a vehicle to be delivered efficiently in the body.

What is a virosome?

A virosome is the reconstituted membrane of an enveloped virus. Many viruses are surrounded by a membrane, or envelope, that is derived from a membrane of the host cell; these viruses are produced by budding from a host cell membrane.  The envelope thus contains lipids of the host cell and viral proteins. These viral proteins have a function in binding to new host cells, and in inducing fusion of a membrane of the new host cell with the viral membrane.
The figure to the left shows an influenza virus: the envelope (green) made of influenza lipids constitute the membrane and proteins called Hemagglutinin (HA) and Neuraminidase (NA) are intercalated on it. Inside the envelope the Nucleocapsid (brown) and the genetic material of the source virus (grey).

 

 

The figure to the left shows an influenza virus: the envelope (green) made of influenza lipids constitute the membrane and proteins called Hemagglutinin (HA) and Neuraminidase (NA) are intercalated on it. Inside the envelope the Nucleocapsid (brown) and the genetic material of the source virus (grey).

 

 

 

 

Virosomes are produced by dissolving the envelope of a virus by a detergent or short-chain phospholipid. Next, the viral genetic material and non-membrane proteins are removed. Upon the subsequent removal of the detergent or short-chain phospholipid, the viral membrane is reconstituted, producing a virosome, containing the viral membrane proteins and lipids.  Viral proteins confer to virosome based vaccine structural stability, homogeneity and increase the immunological properties of virosomes.

 

 

As shown in the figure to the left, the virus is devoid of the nucleocapsid including the genetic material of the source virus: the virosome is created. Devoid of its substance, it is not able to replicate, cause an infection or a disease.

 

 

 

 

 

Virosome based vaccines

Virosomes provide a technology platform that can be adapted to many vaccines.  Lipids, antigens, adjuvants, or other materials, can be added to the dissolved viral membrane. Or can be included in the virosome during reconstitution.
The safety and tolerability of influenza virosomes have already been proven. The vaccines Inflexal® for influenza and Epaxal® for Hepatitis A are approved products on the market both using virosomes from influenza as a delivery platform.
Mymetics’ vaccine candidates for HIV/AIDS and for Malaria are both based upon the influenza virosomes.

Status and next Steps

Mymetics BV’s laboratory, led by Dr. Toon Stegmann in the Netherlands, continues to develop improved virosome technologies, used for most of its vaccines.

 

designed virosome images

 

Standard&Poors - Analysis Report

To see the latest S&P report on Mymetics, click here: