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

• Published in: Microbiology and immunology 2002-01, Vol.46 (7), p.449-461
• Main Authors: Irie, Takashi, Matsuda, Yukihiro, Honda, Yoshikazu, Morimoto, Kinjiro, Kawai, Akihiko
• Format: Article
• Language: English
• Subjects: additional glycosylation; Amino Acid Sequence; Animals; Antibodies, Monoclonal - immunology; Antibodies, Viral - immunology; Antigens, Viral - chemistry; Antigens, Viral - immunology; Bacteriology; Base Sequence; Biological and medical sciences; Cells, Cultured; Electrophoresis, Polyacrylamide Gel - methods; Epitopes - chemistry; Epitopes - immunology; escape mutant; Evolution, Molecular; Fluorescent Antibody Technique; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Glycoproteins - chemistry; Glycoproteins - genetics; Glycoproteins - immunology; Microbiology; Models, Genetic; Molecular immunology; Molecular Sequence Data; monoclonal antibody (mAb); Mutagenesis, Site-Directed; Mutation; Neutralization Tests; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Protein Conformation; Rabies - immunology; rabies virus glycoprotein; Techniques; Viral Envelope Proteins - chemistry; Viral Envelope Proteins - genetics; Viral Envelope Proteins - immunology
• ISSN: 0385-5600; 1348-0421
• DOI: 10.1111/j.1348-0421.2002.tb02719.x

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.