Antibody development using mice was precedently established, and most of antibody medicines currently available are of chimeric or humanized antibody, which is a modification of mouse antibody with replacement of the mouse element, a cause of allergy, with human counterpart. However, it is coming to be major lately to develop fully human antibodies containing no mouse element. The transgenic mouse method, using mouse with human antibody gene, and the phage display method, using bacteriophages, have been devised to develop fully human antibodies.

Evec devised a unique technique to develop fully human antibodies from blood B lymphocytes, cells responsible for antibody production in human body.

Human bodies are exposed to various antigens, with infection, for example. On each exposure, antibody-producing lymphocytes are activated, which then remain as memory B lymphocytes. Namely our peripheral B lymphocyte population can be considered as a library of memory B lymphocytes expressing antibodies.

EB virus induces proliferation of B lymphocytes, and promotes antibody production. In in vitro experiment, EB virus-infected lymphocytes stably proliferate over 6 months while non-infected lymphocytes die within a week or so.

We develop antibodies by using the EB virus activity to proliferate B lymphocytes.
B lymphocytes are separated from 10～20ml blood, and infected with EB virus.
From the proliferated B lymphocytes, cell clones producing the antibody of interest are separated. The clone separation is carried out by a combination of the clone culture method (repeating dilution culture) and the sorting method (selectively separating the antibody of interest with the use of FACS). After the separation, the antibody gene is cloned and transfected into CHO cells for antibody production. Namely EB virus is used merely as a means to isolate antibody genes from blood lymphocytes. There is no risk for contamination of the antibody with EB virus.

In the antibody development using mice, an excessive antigen is immunized for a short period to promote lymphocytes to produce antibodies of interest. Because of the excessive antigen, even those producing low affinity antibodies are activated. In contrast, human blood lymphocytes are activated through natural immune reaction, such as reaction to infection; lymphocytes are stimulated repeatedly with a small amount of antigen, and thus only those producing high affinity antibodies are activated. Consequently the lymphocytes producing the antibodies with high binding activity are accumulated in human blood. The highest binding activity of the antibodies developed by mouse immunization is around 10^-9M, and those of the antibody medicines already in the market are much the same as that.
In contrast, the binding activity of Evec’s antibodies developed from blood B lymphocytes is 10^-11M, 100 times higher than that of mouse antibody.

Most of the techniques of antibody development are patent-granted to the pharmaceutical companies in Europe and USA, and extremely high licensing fees are charged for using them.
While the method using EB virus was known more than 30 years ago, it has been thought difficult to realize it. Evec achieved the technique for stable antibody development, commanding accumulated know-how.