Virus-like particles (VLPs) are among the most exciting emerging vaccine technologies for generating effective and long-lasting protection. It is an advanced technology that has a number of advantages over traditional vaccines. These resemble viruses that are non-infectious as they do not contain any viral genetic material.

A number of companies around the world are working on developing vaccines with these virus-like particles. US-based companies Medicago and Novavax are pursuing clinical trials of VLP-based influenza vaccines. Also, Taiwan-based emerging company, Medigen, has developed VLP for the development of new vaccine candidates against human immunodeficiency virus (HIV), hepatitis B virus (HBV), human papilloma virus (HPV) and influenza virus. (Also read Vaccine delivery technologies of the future)

The particles are made to look like viruses, allowing them to be recognized by the body's immune system. They help in effectively activating key aspects of the immune response to achieve potent immune stimulation and to provide immunological memory. Because VLPs closely match the exact structural components, shape and size of the actual pathogen, they more effectively trigger key parts of the immune system for a longer lasting and more robust immune response.

Medicago has developed VLPExpress, a high throughput platform that rapidly expresses, purifies and tests candidate VLPs. The company is conducting phase I study of its pandemic H5N1 influenza VLP vaccine candidate and has received positive results from an immunogenicity study in mice with this new vaccine candidate for the influenza A virus. Results have demonstrated that the company's H1 VLP vaccine induced a positive immune response in 100 percent of the mice against the H1N1 influenza.

"There is a unique opportunity in VLPs for vaccine development. It takes 19 days from gene sequencing to incubation, extraction, purification and flu VLP development. The company is conducting phase II trial for H5N1 in Canada and phase I trial in the US for H1N1 using this technology," says Mr Frederic Ors, vice president, Business Development, Medicago.