Canine and feline coronaviruses analyzed in this study: nucleotide sequence acquisition numbers and serum cross-neutralizing activity.

<p>N.D.: Not done.</p>a<p>Serum was collected from the cat that was inoculated intraorally with type I FCoV C3663 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106534#pone.0106534-Terada1" target="_blank">[36]</a>.</p>b<p>Serum was collected from the cat that was inoculated intraperitoneally with type II FCoV M91-267 (unpublished data).</p>c<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106534#pone.0106534-Terada1" target="_blank">[36]</a>.</p><p>Canine and feline coronaviruses analyzed in this study: nucleotide sequence acquisition numbers and serum cross-neutralizing activity.</p

Schema of feline and canine coronaviruses.

<p>(<b>A</b>) Schema of type II CCoV. Each ORF is indicated by squares. Arrowheads indicate location of primers for amplification of partial RdRp, partial S and full N genes. (<b>B</b>) Schema of type II CCoV fc1, type II FCoV M91-267, KUK-H/L and Tokyo/cat/130627, and type I FCoV C3663 and Yayoi. Blue boxes indicate ORFs originating from type II CCoV. Red boxes indicate ORFs originating from type I FCoV.</p

Simplot analysis of canine and feline coronaviruses.

<p>Similarity between nucleotide sequences of 3′-region of genome of type II CCoV fc1, type I FCoV Black, and type II FCoVs KUK-H/L, M91-267 and Tokyo/cat/130627. Horizontal axis refers to nucleotide position of fc1. Upper region of the plot map shows ORF structure in type II CCoV fc1 and corresponds to nucleotide positions in the plot map. A similarity of 1.0 indicates 100% identity with the nucleotide sequence. Parameters for calculation were as follows: window size, 200 bp; and step size, 40 bp.</p

Hypothesis of emergence of type II FCoV.

<p>Some cats persistently infected with type I FCoV are superinfected with type II CCoV which is excreted from dogs. Inside the cat body, type II FCoV emerges by homologous recombination and induces severe clinical disease, FIP. Diseased cats do not spread type II FCoV.</p