www.elsevier.com/locate/tvjl

The Veterinary Journal 170 (2005) 151–152

TheVeterinary Journal

Guest editorial

When will rAbs replace mAbs in labs?

In the early 1990s, there was great optimism for the

potential that recombinant antibody (rAb) technology

would obviate the need for animal immunization and

supersede monoclonal antibody (mAb) technology in re-

search labs around the world. In 1991, 16 years after the

first mAb, even its inventor predicted the eventual obso-lescence of his new tool (Winter and Milstein, 1991). Yet

while rAb technology has proven to possess all of its

predicted potential and, indeed, numerous novel appli-

cations have been discovered, 14 more years have passed

and clearly this powerful technology has not been

adopted by the large majority of laboratories using anti-

bodies in their research. Why is this?

The two most important reasons that rAbs have notreplace mAbs in labs are probably that the technology

has required a substantial investment of time and energy

to establish and that commercial priorities have limited

the distribution of reagents, particularly clone libraries.

Most immunology labs have inherent capabilities in ani-

mal immunization and cell culture methods so the gener-

ation of mAbs is generally routine. In contrast,

production of rAbs generally requires expertise withmethods not often routine within immunology labs; such

as the preparation of DNA libraries, handling of bacte-

riophage and expression of recombinant proteins.

Expression of rAbs has probably been the biggest prob-

lem because full-length antibodies consist of multiple

protein chains and complex conformations stabilized by

disulfide bonds. To express functional, full-size antibod-

ies has usually required the use of sophisticated mamma-lian cell expression systems. In order to use microbial

host cells, researchers generally express only the antigen

combining domain of the antibody by linking the heavy

and light chain variable regions through a spacer peptide

to produce a single-chain antibody fragment. Unfortu-

nately, even this artificial antibody fragment, when pro-

duced in bacteria, has often proven to be poorly

expressed, poorly soluble and/or difficult to handle.The huge commercial potential of rAb technology

has surely retarded the publication of methods improve-

1090-0233/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.tvjl.2004.12.003

ments and new applications in order to permit their

inventors to capture intellectual property (IP) or for

companies to slow competitor progress. More impor-

tantly, construction of large, diverse and high quality

antibody display libraries is difficult and expensive,

and this investment has been too great for most aca-demic labs to make. Most such libraries have therefore

been made by companies, and they have chosen to keep

these libraries ‘‘in house’’.

It seems that the environment is now changing and

rAb technology will become much more widespread in

the next few years. One important reason for this is

that the number of publications has reached sufficient

critical mass that the technology is now widelyacknowledged to be extremely powerful and less often

perceived as too complex and quirky for most labs to

undertake. The basis for the growing positive percep-

tion of the technology is nicely exemplified in Jody

Berry�s excellent review of mAb and rAb methods

and strategies in the current issue of The Veterinary

Journal (Berry, 2005).

Also evident from Dr. Berry�s review, the number ofapplications in which rAb technology has advantages

over mAb technology is becoming too numerous, and

the power of these applications too great for many labs

to resist. Of special note, recombinant antibody display

techniques (in which antibodies are linked to their

encoding genetic material) allow researchers to ‘‘select’’

for rAbs having desired properties rather than just to

‘‘screen’’ for these properties as is done with mAbs.For example, one can develop panning techniques that

select for (or against) antibodies having higher antigen

avidity, broader antigen specificity, or recognition of in-

tact cells and organisms. The panning can even be done

at a microscopic level by incubating display libraries

with tissue sections or mixed cell populations and using

laser dissection or FACS to purify specific cell types

from which to obtain the bound antibodies.One can choose to immunize virtually any animal

to obtain the antibody coding DNA for library

152 Guest editorial / The Veterinary Journal 170 (2005) 151–152

construction. The immunized animals may be rabbits or

ruminants that are considered to be more robust at anti-

body maturation and therefore may permit identifica-

tion of antibodies with higher affinities for their target.

Alternatively, the immunization may be in camelids

which produce heavy-chain only antibodies that donot require a light chain for function (Muyldermans,

2001). These antibodies have proved to be much easier

to functionally express within microbial host cells and

more stable than recombinant antibody fragments de-

rived from mice or human (Dumoulin et al., 2002).

Newer library panning techniques, such as ribosome

display (Hanes et al., 1998) and mRNA display (Wilson

et al., 2001), and mutagenesis methods like error-pronePCR (Gram et al., 1992) and DNA shuffling (Crameri

et al., 1996), promise to dramatically improve the com-

plexity of libraries available for screening and the ability

to perform test tube affinity maturation. These robust

methods make feasible the goal of using ‘‘non-immune’’,

random sequence libraries to generate high affinity rAbs,

and thus eventually should eliminate the need for animal

immunizations. Finally, once a desirable antibody frag-ment is obtained, the antigen binding domain can be

readily engineered so as to produce full-size rAbs of vir-

tually any antibody isotype or as single chain antibody

fusions to whatever alternative effector domains are

desired.

As the power of rAb technology has grown dra-

matically, the causes that limited its widespread use

have been dissipating. The required molecular biologytools are now more routine and easy-to-use kits can

be purchased. Expression technologies have substan-

tially improved for the recombinant antibody frag-

ments and even full-size rAbs can now be expressed

within simpler expression systems such as insect cells

(Rindisbacher et al., 1995) or mass produced in plants

(Fischer et al., 1999). Because more academic labs

have begun using the technology, more vectors and li-braries are becoming more available in the public do-

main. Even the IP issues that limited more widespread

commercial use and library distribution will diminish

as patents expire and ownership issues clarify. It seems

certain that rAb technology will soon fulfill, and prob-

ably surpass, the optimistic expectations of its early

pioneers.

Charles B. Shoemaker

Division of Infectious Diseases

Department of Biomedical Sciences

School of Veterinary Medicine

Tufts University, 200 Westboro Road

North Grafton, MA 01536, USA

E-mail address: charles.shoemaker@tufts.edu

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