Distinct mutation in the feline coronavirus spike protein cleavage activation site in a cat with feline infectious peritonitis-associated meningoencephalomyelitis

Abstract

Case summary: This report describes a cat with chronic, progressive, non-painful, non-lateralizing multifocal neurologic clinical signs associated with feline infectious peritonitis (FIP). The cat initially presented as underweight, despite a good appetite, and a complete blood count showed non-regenerative anemia. Three months later the cat was returned having developed ataxia and paraparesis, which then progressed over 2 months to tetraparesis, tail plegia, urinary and fecal incontinence, and titubation. Histologic examination of the tissues with subsequent immunohistochemistry confirmed FIP-associated meningoencephalomyelitis following necropsy. Molecular analysis of the coronavirus spike protein within the tissues identified a specific, functionally relevant amino acid change (R793M), which was only identified in tissues associated with the central nervous system (ie, brain and spinal cord).

Relevance and novel information: This case report describes an early presentation of a cat with primarily neurologic FIP, with molecular characterization of the virus within various tissues.

Keywords: Feline infectious peritonitis; feline coronavirus; meningoencephalomyelitis; neurologic; spike protein.

Figure 1

Feline infectious peritonitis (FIP)-associated meningoencephalomyelitis. (a) Spinal cord. The meninges are expanded by large numbers of plasma cells, lymphocytes and macrophages (× 200, hematoxylin and eosin). (b) Telencephalon, lateral ventricle. The choroid plexus is markedly expanded by inflammation, which extends into the surrounding periventricular tissue (× 20, hematoxylin and eosin). (c) Mesencephalon. The mesencephalic aqueduct is obliterated by inflammation, which extends in the adjacent tissue (× 200, hematoxylin and eosin). (d) Rhombencephalon, fourth ventricle. Numerous macrophages have a strong intracytoplasmic positive immunoreactive signal (× 40, FIP virus immunohistochemistry)

Figure 2

Molecular analysis of the spike gene. A 156 base pair region of the feline coronavirus (FCoV) spike protein gene is shown and represented in single amino acid code, with variant residues from the central nervous system sample colored and amino acid positions noted. The activation site between the S1 and S2 domains (S1/S2) is indicated and boxed. Amino acid positions are based on that for FCoV RM spike (Genbank accession #ACT10854.1) as a prototype sequence. Sequences were analyzed using Geneious v. 10.1.2