The production of antibody fragments and antibody fusion proteins by yeasts and filamentous fungi

Abstract

In this review we will focus on the current status and views concerning the production of antibody fragments and antibody fusion proteins by yeasts and filamentous fungi. We will focus on single-chain antibody fragment production (scFv and VHH) by these lower eukaryotes and the possible applications of these proteins. Also the coupling of fragments to relevant enzymes or other components will be discussed. As an example of the fusion protein strategy, the 'magic bullet' approach for industrial applications, will be highlighted.

Figure 1

Schematical representation of the structure of a conventional IgG and fragments that can be generated thereof. The constant heavy-chain domains C_H1, C_H2 and C_H3 are shown in yellow, the constant light-chain domain (C_L) in green and the variable heavy-chain (V_H) or light-chain (V_L) domains in red and orange, respectively. The antigen binding domains of a conventional antibody are Fabs and Fv fragments. Fab fragments can be generated by papain digestion. Fvs are the smallest fragments with an intact antigen-binding domain. They can be generated by enzymatic approaches or expression of the relevant gene fragments (the recombinant version). In the recombinant single-chain Fv fragment, the variable domains are joined by a peptide linker. Both possible configurations of the variable domains are shown, i.e. the carboxyl terminus of V_H fused to the N-terminus of V_L and vice versa.

Figure 2

Schematical representation of the structure of a conventional IgG, a heavy-chain IgG antibody and the variable heavy-chain antibody fragment (V_HH) that can be generated of the latter. Heavy-chain antibodies found in llama and camel are only composed of heavy-chains and lack the light chain completely, as shown in this Figure. The antigen-binding domain consists of only the V_H domain, which is referred to as V_HH (variable heavy-chain antibody fragment), to distinguish it from a normal V_H. The constant heavy-chain domains C_H1, C_H2 and C_H3 are shown in yellow, the constant light-chain domain (C_L) in green and the variable heavy-chain (V_H or V_HH) or light-chain (V_L) domains in red and orange, respectively.

Figure 3

Schematical example of the 'Magic bullet' approach in consumer applications, where an antibody fragment (in this case a llama variable heavy-chain antibody fragment; V_HH) recognising a spot on textile, is coupled to an effector molecule (in this case A. ramosus peroxidase; ARP). ARP is a peroxidase, which utilises hydrogen peroxide to catalyse the oxidation of a wide range of organic and inorganic compounds, which makes the enzyme suitable for use in bleaching processes [139].