Passive immunization of guinea pigs with llama single-domain antibody fragments against foot-and-mouth disease

• Published in: Veterinary microbiology 2007-03, Vol.120 (3), p.193-206
• Main Authors: Harmsen, M.M., van Solt, C.B., Fijten, H.P.D., van Keulen, L., Rosalia, R.A., Weerdmeester, K., Cornelissen, A.H.M., De Bruin, M.G.M., Eblé, P.L., Dekker, A.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; amino acid sequences; animal models; Animals; antibodies; Antibodies, Viral - administration & dosage; Antibodies, Viral - biosynthesis; Antibodies, Viral - chemistry; Antibodies, Viral - genetics; Applied microbiology; Biological and medical sciences; Camelids, New World - immunology; Enzyme-Linked Immunosorbent Assay - veterinary; epitopes; Foot-and-mouth disease; Foot-and-Mouth Disease - immunology; Foot-and-Mouth Disease - prevention & control; Foot-and-mouth disease virus; Foot-and-Mouth Disease Virus - immunology; Fundamental and applied biological sciences. Psychology; Guinea Pigs; immunization; Immunization, Passive - methods; Immunization, Passive - veterinary; Immunoglobulin Fragments - administration & dosage; Immunoglobulin Fragments - genetics; Immunoglobulin Variable Region - immunology; immunotherapy; in vivo studies; llamas; Male; Microbiology; Molecular Sequence Data; Monoclonal antibody; Nanobody; neutralization tests; Neutralization Tests - veterinary; Passive vaccination; Phylogeny; Recombinant Proteins - blood; Recombinant Proteins - genetics; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Sequence Alignment; serotypes; Single-domain antibody; vaccines; Vaccines, antisera, therapeutical immunoglobulins and monoclonal antibodies (general aspects)
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/j.vetmic.2006.10.029

Foot-and-mouth disease (FMD) is a highly contagious disease that occasionally causes outbreaks in Europe. There is a need for therapies that provide rapid protection against FMD in outbreak situations. We aim to provide such rapid protection by passive immunization with llama single-domain antibody fragments (VHHs). Twenty-four VHHs binding serotype O FMDV in vitro were isolated from immunized llamas by phage display and expressed in bakers yeast for further characterization. They recognized four functionally independent antigenic sites. Six strongly FMDV neutralizing VHHs bound to a peptide representing the GH-loop of viral protein 1 known to be involved in binding to the cellular receptor of FMDV. Clone M8, recognizing this antigenic site, and clone M23, recognizing another antigenic site, showed synergistic in vitro virus neutralization. Three FMDV specific VHHs were PEGylated in order to decrease their rapid blood clearance and thus enable in vivo guinea pig protection experiments. Passive immunization with individual VHHs showed no protection, but a mixture of M8 and M23 showed partial transient protection. The protection afforded by these VHHs was however low as compared to the complete protection afforded by convalescent guinea pig serum. In contrast, these VHHs showed far more efficient in vitro FMDV neutralization than convalescent guinea pig serum. This lack of correlation between in vitro neutralization and in vivo protection lends further credence to the notion that opsonophagocytosis of FMDV is important for protection in vivo.