Differential recognition of peptides within feline coronavirus polyprotein 1 ab by sera from healthy cats and cats with feline infectious peritonitis

The aim of the study was to identify peptides within the polyprotein (Pp) 1 ab that are differentially recognised by cats with either enteric or systemic disease following infection with feline coronavirus. Overlapping 12-mer peptides (n = 28,426) across the entire Pp1ab were arrayed on peptide chips and reacted with pooled sera from coronavirus seropositive cats and from one seronegative cat. Eleven peptides were further tested in ELISA with individual serum samples, and three were selected for further screening. Two peptides (16433 and 4934) in the nsp3 region encoding the papain 1 and 2 proteases were identified for final testing. Peptide 4934 reacted equally with positive sera from healthy cats and cats with feline infectious peritonitis (FIP), while peptide 16433 was recognized predominantly by FIP-affected cats. The value of antibody tests based on these peptides in differentiating between the enteric and FIP forms of feline coronavirus infection remains to be determined.