Studies on the escape mutants of rabies virus which are resistant to neutralization by a highly conserved conformational epitope-specific monoclonal antibody #1-46-12.
We investigated a virus-neutralizing conformational epitope of the rabies virus glycoprotein (G) that is recognized by an anti-G monoclonal antibody (mAb; #1-46-12) and shared by most of the laboratory strains of the virus. To investigate the epitope structure, we isolated escape mutants from the HEP-Flury virus (wild-type; wt) after repeated passages in culture in the presence of the mAb. Immunofluorescence studies indicated that the mutants could be classified into two groups; the Group I lacked the epitope, while Group II preserved the epitope. The latter was dominant under the passage conditions, since Group I disappeared during the continuous passages. G proteins showed different electrophoretic mobilities; G protein of Group I migrated at the same rate as wt G protein, while that of Group II migrated at a slower rate, which was shown to be due to acquisition of an additional oligosaccharide side chain. Nucleotide sequencing of the G gene strongly suggested that amino acid substitutions at Thr-36 by Pro and Ser-39 by Thr of the G protein are responsible for the escape mutations of Groups I and II, respectively. The latter is a unique mutation of the rabies virus that allows the G protein to be glycosylated additionally at Asn-37, a potential glycosylation site that is not glycosylated in the parent virus, in preserving the epitope-positive conformation. These results suggest that to keep the 1-46-12 epitope structure is of greater survival advantage for the virus to escape the neutralization than to destroy it, which could be achieved by acquiring an additional oligosaccharide chain at Asn-37.
Irie
Takashi
T
Department of Molecular Microbiology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan.
Matsuda
Yukihiro
Y
Honda
Yoshikazu
Y
Morimoto
Kinjiro
K
Kawai
Akihiko
A
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000914:Antibodies, Viral / Q000276:immunology*; D000956:Antigens, Viral / Q000737:chemistry / Q000276:immunology*; D001483:Base Sequence; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D000939:Epitopes / Q000737:chemistry / Q000276:immunology*; D019143:Evolution, Molecular; D005455:Fluorescent Antibody Technique; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009500:Neutralization Tests; D011487:Protein Conformation; D011818:Rabies / Q000276:immunology; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000956:Antigens, Viral; D000939:Epitopes; D006023:Glycoproteins; D014759:Viral Envelope Proteins; C064951:glycoprotein G, Rabies virus