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Mutation of neutralizing/antibody-dependent enhancing epitope on spike protein and 7b gene of feline infectious peritonitis virus: Influences of viral replication in monocytes/macrophages and virulence in cats

Takano, Tomomi, Tomiyama, Yoshika, Katoh, Yasuichiroh, Nakamura, Michiyo, Satoh, Ryoichi, Hohdatsu, Tsutomu
Virus research 2011 v.156 no.1-2 pp. 72-80
Feline coronavirus, amino acids, cats, epitopes, genes, macrophages, monoclonal antibodies, monocytes, mutants, neutralization, nucleotides, sequence deletion, virulence, virus replication, viruses
We previously prepared neutralizing monoclonal antibody (MAb)-resistant (mar) mutant viruses using a laboratory strain feline infectious peritonitis virus (FIPV) 79-1146 (Kida et al., 1999). Mar mutant viruses are mutated several amino acids of the neutralizing epitope of Spike protein, compared with the parent strain, FIPV 79-1146. We clarified that MAb used to prepare mar mutant viruses also lost its activity to enhance homologous mar mutant viruses, strongly suggesting that neutralizing and antibody-dependent enhancing epitopes are present in the same region in the strain FIPV 79-1146. We also discovered that amino acid mutation in the neutralizing epitope reduced viral replication in monocytes/macrophages. We also demonstrated that the mutation or deletion of two nucleotides in 7b gene abrogate the virulence of strain FIPV 79-1146.