Anti‐anti‐idiotypic (Ab3) antibodies that bind progesterone‐11α–bovine serum albumin differ in their combining sites from antibodies raised directly against the antigen

Abstract

SUMMARYPolyclonal rabbit anti-idiotypic (Ab2) antibodies raised against the antiprogesterone mAb DB3 (Ab1) were used to induce an Ab3 antiprogesterone response in BALB/c mice. While the af®nity of Ab3 sera for progesterone was 10±50-times lower than that of DB3, their steroid-binding speci®city showed considerable similarity to DB3. Two immunoglobulin M (IgM) Ab3 monoclonal antibodies (mAbs), 1A4 and 3B11, were obtained, both of which bound progesterone conjugated to bovine serum albumin (progesterone±BSA). 1A4 also bound free progesterone, although with low af®nity and very broad cross-reactivity. Like DB3, 1A4 is encoded by a heavy-chain variable region (V H ) gene segment from the small VGAM3.8 family, a restriction that is characteristic of antibodies raised against progesterone-11a±BSA. In contrast, 3B11 binds progesterone-11a±BSA but not free progesterone and is encoded by an unrelated V H gene from the J558 family. The light chain variable region (V L ) of 1A4 lacks the intradomain disulphide bridge owing to replacement of CysL23 by Tyr. Both the 1A4 and 3B11 heavy chains have extremely short complementarity determining region (CDR) H3 loops, comprising three and four amino acids, respectively. Modelling of the combining site of 1A4 from the X-ray crystallographic structure of DB3 indicates that the short H3 loop is a major factor in the loss of af®nity and speci®city for steroid.

A new chapter for anti-idiotypes in low molecular weight compound immunoassays

“…Ab2s can, however, be used to produce anti-antiidiotype antibodies that can recognise the original LMW compound. These antibodies can have different structural characteristics to the original Ab1, as has been demonstrated, for example, for progesterone-11α [43]. Ab2s may therefore be of use in bypassing further conjugate production if additional Ab1s are required.…”

Current advances in antifertility vaccines for fertility control and noncontraceptive applications

“…Antifertility vaccines based on gonadotropinreleasing hormone (GnRH) have also reached early clinical trials, although not exclusively for human contraception, as they require androgen supplementation to maintain libido and secondary sex characteristics [19,20]. Other hormone-associated targets under consideration include, luteinizing hormone (LH) [21], sex steroids [22][23][24] and reproductive hormone receptors [25,26]. However, these are still at the laboratory bench stage.…”

“…A variety of strategies are being employed to overcome lack of efficacy, including: production of antibodies directly in the relevant area of the genital tract [51], use of B-and T-cell epitopes as carrier molecules [47,49], examination of novel adjuvants and immunopotentiators [52,53], use of passive immunization [54], humanized and anti-idiotypic antibodies [10,22,23,55,56], construction of peptide mimetics [57], use of multiple epitopes or antigens [58][59][60][61] and use of bacterial or viral vectors [35,62].…”

Homology of ab1 and ab3 Monoclonal Antibodies That Neutralize Semliki Forest Virus

“…But it is likely that the ab3 immune response is more degenerate, e.g., low-affinity SFV-specific antibodies with mutations in the CDR3 region are not detected. Degeneration of ab3 response is most clearly demonstrated by use of polyclonal ab2 antibodies as shown recently for progesteron-11-bovine serum albumin (9). It may be of interest to prepare synthetic peptides of the CDR3 region of the SFV-neutralizing mAbs to investigate whether they could act as a neutralizing mini-antibody (12).…”