Antibodies

Origin of antisperm antibodies

During the 20th century, several cases of infertile men and women were observed. At this time, the reasons of this sterility were elusive. Researchers discovered that this was the result of the production of antisperm antibodies (ASA). These antibodies can be produced in the body of women and men against spermatozoa, and they cause infertility. Presence of ASA in male and/or female partner have been considered as infertility cause in around 2-30% of infertile couples [1]. For example, ASA production in women can be caused after spermatozoal deposition into genital tract with a compromised epithelial barrier, the peritoneal cavity or the gastrointestinal tract.

Researchers tried to use these antibodies and related antigens to create a contraceptive vaccine (CV) [2]. They made mice produce ASA (production by B cells) by vaccinating them with the related antigen. The results show that vaccination with a sperm antigen or its cDNA causes a long-term, reversible contraception in female mice [3].

They showed that ASA can be very effective for a long-term and reversible contraception. This is exactly what we want to create by engineering L. jensenii to make them produce ASA against a spermatozoa antigen.

Why do we chose to synthesize ASA ?

What is and antibody ?

The classical representation of an antibody is as a Y-shaped molecule composed of four polypeptide subunits with two identical heavy and light chains, linked by disulfure bounds. Each chain is composed of a constant (constant heavy CH, constant light CL) and a variable part (variable heavy VH, variable light VL). It is secreted by B lymphocytes that specifically recognize and neutralize antigens.

scFv

scFv (for Single-Chain Variable Fragment) are recombinant molecules where the variable region of the heavy (VH) and light (VL) immunoglobulin chains are linked into a single peptide. VH and VL are linked with a flexible linker sequence, here Gly4Ser. Glycine amino-acids ensure a good flexibility of the linker. Effect of scFv is similar to antibodies.

Antisperm antibodies

ASA are immunoglobulins (IgG, IgA, IgM) directed against sperm antigens. The production can be caused whenever sperm encounter the immune system. They can have different effects.

Effect of ASA on sperm

ASA can affect fertility through several mechanisms : inhibition of sperm motility, capacitation, acrosome reaction, sperm zona interaction, sperm-oolemma binding and penetration and preimplantation embryonic development.
The main activity of spermicides is the inhibition of sperm motility. We chose several ASA that have this effect. If spermatozoa have their motility inhibited, they can not fertilize the egg anymore [2].

YLP20 and YLP12

Objectives

Experiments