Polyclonal catalytic antibodies

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Abstract

Polyclonal catalytic antibodies offer advantages in the evaluation of immunogens and in the ease of production of large quantities of antibodies. They comprise the entire immune response of an animal to an immunogen where monoclonals represent a subset. Polyclonal antibodies are consequently particularly suitable for evaluating catalytic antibody responses generated by different haptens or a group of structurally related haptens.

The authors reported the first polyclonal catalytic antibodies in 1990. An unexpected finding is that polyclonal catalytic antibodies show single-site kinetic behaviour, i.e. whatever structural heterogeneity exists, the kinetic behaviour is homogeneous. Many groups worldwide have since published work in this area. Three groups are prominent. The authors' group, a group based in Austin, Texas, and led by Iverson, and a Shanghai group. The authors' group works with sheep antibodies and has published mechanistic studies and, more recently, specificity studies that revealed the catalysis of a β-lactam. Most of this work over a 10-year period was performed by using a single bleed from a single sheep, which gives an indication of the ease of production and utility of such catalytic antibodies. Iverson's group works with rabbit antibodies and has published much work on the evaluation of catalytic antibodies generated by structurally related haptens. The Shanghai group has concentrated on the studies of polyclonal catalytic antibodies for electrocyclic reactions where any danger of contaminating enzymes is reduced.

The use of immunisation to generate therapeutically useful catalytic antibodies (necessarily polyclonal) in a host animal is an attractive target. Several groups are working towards this. The authors themselves have published in this area and promising recent studies come from a group working in France on immunisation to protect against nerve agents and a Texas group (based in Houston) that has demonstrated active immunisation to generate antibodies that catalyse the hydrolysis of a carbamate insecticide.

Section snippets

Background

Following Jencks' (1969) celebrated proposal for generating catalytic antibodies, several groups lost no time in attempting to bring his ideas to fruition. In the early 1970s, attempts were necessarily confined to polyclonal antibodies and all were unsuccessful. The only example to reach publication was Raso and Stoller's (1975) unsuccessful attempt to generate antibodies that would catalyse a transamination reaction. This was published in the same year that Kohler and Milstein (1975) reported

The question of supply

Polyclonal catalytic antibodies offer many advantages (See Table 1). They are cheap and simple to produce. Large quantities (tens of grams) of catalytic antibodies can be generated from a single sheep. While it is often claimed to be theoretically possible to produce unlimited quantities of monoclonal IgG, only a very few groups have the resources and expertise to generate grams of monoclonal catalytic antibodies (and even then clonal drift and the occasional loss of clones remain a

Groups working with polyclonal catalytic antibodies

There are about 50 publications describing polyclonal catalytic antibody activity, and much of the published data originates from three groups; a UK group, jointly led initially by Brocklehurst in London and Gallacher in Brighton, and subsequently strengthened by the recruitment of Resmini and Ostler, a Texas (Austin) group, led by Brent Iverson, and a group based in Shanghai, led by Yeh. The remaining publications have originated from isolated reports of other investigations of polyclonal

Demonstration of polyclonal antibody catalysis

The group led by Brocklehurst and Gallacher was the first to describe the successful production of polyclonal catalytic antibodies. Sheep antibodies (Gallacher et al., 1990) generated by the phosphate (2) catalyse the hydrolysis of the carbonate (1). These polyclonal catalytic antibodies have been investigated extensively over the last 11 years, and have generated a considerable amount of detailed information. Having established that polyclonal catalytic antibodies could indeed be generated,

The Texas (Austin) group

Iverson et al. (1991) entered the polyclonal catalytic antibody field by repeating their own successful monoclonal work, but this time, generating rabbit polyclonal antibodies that catalysed the hydrolysis of a trityl ether. This work avoided potential false positive results from enzyme contamination by studying a reaction with no known enzyme counterpart. This advantage has also been exploited by groups investigating the generation of catalytic antibodies that catalyse Diels–Alder reactions

Shanghai group

Workers at the Shanghai Institutes of Organic Chemistry and of Cell Biology entered the area of polyclonal catalytic antibodies by studying hydrolysis but quickly moved on to extending the range of reactions that can be catalysed by polyclonal antibodies.

Antiidiotypic antibodies

The antiidiotypic approach represents an alternative method for the generation of antibody catalysts, and polyclonal systems have been used to good effect for this purpose by several groups Friboulet et al., 1994, Johnson and Moore, 1995, Crespeau et al., 1994. This topic is covered in more detail elsewhere in this journal issue, and so this article highlights just one advantage of using polyclonal antibodies for this purpose.

Polyclonal antiidiotypic antibodies can be particularly informative

Active immunisation to generate polyclonal catalytic antibodies

One major aim of catalytic antibody research is to develop therapeutic agents. One can foresee the administration of monoclonal or polyclonal catalytic antibodies to patients to exert designed therapeutic effects. This is, of course, passive immunisation. Alternatively, one can envisage immunising with a transition-state analogue to generate the patient's own catalytic antibodies. This is active immunisation and would involve polyclonal catalytic antibodies. This is an attractive target to

Some common findings

Some results have emerged as general within those groups working with polyclonal catalytic antibodies. They are the following.

(1) Every group has found a homogeneous kinetic response. This is not what would be predicted but does greatly simplify the study of polyclonal catalytic antibodies.

(2) Catalytic antibodies are found later than simple binding antibodies. This suggests that affinity maturation is important and may contribute to the kinetic homogeneity in (1) above.

(3) The catalytic

Conclusions

Polyclonal catalytic antibodies have been used to investigate the catalysis of a variety of reactions, and to probe the steric and electronic features required in the haptens used to generate them. It has been shown that conformationally rigid haptens are generally more successful in eliciting catalytic antibody activity than flexible ones. Thus, if a hapten has a broader range of potential conformations, then the antibodies elicited may also have a broad set of active site conformations, some

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