Because FCoV spike protein plays critical roles in receptor binding (S1) and fusion (S2), we focused on structural changes in this protein and potential role in altered cellular tropism.
FCoV primers that detect most circulating strains were used to screen all fecal samples (25).
At the initial sampling in 2009 (t = 1), both cats were asymptomatic for FIP and were shedding FCoV in their feces.
The full-length and partial FCoV genomic nucleotide sequences we obtained were deposited in the National Center for Biotechnology Information database (www.
To identify the distinguishing difference(s) between the FCoV pathotypes, we initiated a full genome sequencing program of FECVs found in the feces of apparently healthy cats and of FIPVs found in organs or ascites of cats with pathologically confirmed feline infectious peritonitis.
GenBank accession numbers for the FCoV M gene sequences determined in this study are HQ738691-HQ738733.
Exceptions in this picture were FIPV 9 in cattery F and FECVs 406 and 407 in cattery D, presumably caused by multiple FCoV lineages in these open catteries (an open cattery is one in which cats can move in and out, usually for breeding purposes).
At the 3' end of the same gene, subtype IIa and IIb strains segregated together and were separated from the FCoVs
and the porcine CoVs TGEV and PRCoV (Figure, panel B).
Furthermore, circulating FCoVs found in different tissues of FCoV-infected asymptomatic cats were indistinguishable (17,18).
An alternative circulating virulent-avirulent FCoV hypothesis of viral pathogenesis suggests that distinctive benign and pathogenic strains of FECV circulate in a population, and that the disease will develop only in those persons infected by the virulent strains.
The onset of acute fatal disease (feline infectious peritonitis) is caused by pantropic variants (able to disseminate throughout the organism) of enteric FCoVs with deletions or recombinations in the 3c and 7b genes at the 3' end of the FCoV genome (4).
The S protein of strain CB/05 had the highest identity to FCoV type II strain 79-1683 (Figure 2).