A microantibody is an artificial short chain of

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

s copied from a fully functional natural

antibody An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...

. Microantibodies can stop viruses such as HIV from infecting cells ''

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology an ...

''. Antibodies are produced naturally by the body and play a key role in fighting infections caused by

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

and

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

es. They can also be used to treat infections by use of injections with

blood plasma Blood plasma is a light amber-colored liquid component of blood in which blood cells are absent, but contains proteins and other constituents of whole blood in suspension. It makes up about 55% of the body's total blood volume. It is the intra ...

that contain large amounts of them. The use of whole, natural antibodies as medicines presents many problems: they can only be produced by live cells and this process is difficult to control on an industrial scale, they are large molecules and following administration by injection, they do not diffuse easily from the blood to the tissues and other sites of infections where they are needed. The use of microantibodies potentially solves these problems. They can be chemically synthesized and their small size allows them to leave the blood circulation quickly and reach the sites of infections in the tissues. They are also poorly immunogenic and do not stimulate an immune response in the host. Production problems remain, but microantibodies have the potential to become an important weapon in the arsenal used to treat infections and other diseases.

Background

Vaccines A vaccine is a biological preparation that provides active acquired immunity The adaptive immune system, also known as the acquired immune system, is a subsystem of the immune system that is composed of specialized, systemic cells and pro ...

are used to prevent infections by stimulating the body's own immunity, which includes the production of

antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...

that destroy infectious agents such as

and

es. Some infections can be prevented or treated by antibodies derived from others sources such as blood donations or

monoclonal antibodies A monoclonal antibody (mAb, more rarely called moAb) is an antibody produced from a cell Lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell. Monoclonal antibodies ca ...

made in laboratories. This is called passive immunotherapy. However, these treatments have inherent problems; passive antibody exposes the body to foreign protein and although monoclonal antibodies can be

humanized Humanized antibodies are antibodies from non-human species whose protein sequences have been modified to increase their similarity to antibody variants produced naturally in humans. The process of "humanization" is usually applied to monoclonal an ...

they can still invoke an immune response. However, only relatively small regions on antibody molecules are involved in the recognition and inactivation of pathogens. Microantibodies are smaller, synthetic molecules that mimic these regions but do not have the larger regions on antibodies that induce an immune response.

Prototype

A microantibody has been made from a monoclonal antibody produced in mouse cells. This antibody inactivates

HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...

''in vitro''.

References

{{Engineered antibodies Peptides Antibodies

Background

Prototype

See also

References