Single dose of Medicago's vaccine could offer cross-protection against flu

Researchers recently found that a single dose of a vaccine being developed by Medicago, Inc., a publicly traded biopharmaceutical company, could protect against not only the avian influenza (H5N1) strain it was designed for, but also another H5N1 strain and a strain of a different flu subtype, called H2N2.

This phenomenon, known as "cross-protection," is highly desirable in an influenza vaccine, especially when the threat of a pandemic influenza outbreak looms. That's because influenza strains often mutate, rendering stockpiled vaccines ineffective. Medicago has a special advantage in this regard, because the company can rapidly produce a vaccine in less than a month after the identification of a flu strain. This speed results from Medicago's use of entities known as virus-like particles (VLPs) to create its vaccines. Medicago is a worldwide leader in the development of VLP vaccines using a transient expression system, which produces recombinant vaccine antigens in plants. The accelerated production time frame gives the potential to vaccinate the general public before the first wave of a pandemic.

In the study, researchers gave mice a single dose of Medicago's H5N1 VLP vaccine formulated for the Indonesia H5N1 Influenza virus. After 28 days, the mice were given a lethal dose of either the Vietnam H5N1 strain or an H2N2 Influenza virus strain that caused a pandemic in humans in the late 1950s. The study found Medicago's vaccine protected 100 percent of mice from the Vietnam strain and 70 percent of mice from the H2N2 strain. In the past, the company has completed Phase I and Phase II human clinical trials for its vaccine for the Indonesia H5N1 Influenza virus, demonstrating that that vaccine produced a solid immune response and was safe and well tolerated.

If further studies support this result, there is a possibility that Medicago's vaccine could offer cross-protection to the general public—perhaps keeping many of us safer from a rapidly mutating menace during the next flu pandemic.