Detection of antigenic heterogeneity in feline coronavirus nucleocapsid in feline pyogranulomatous meningoencephalitis.
A new monoclonal antibody (mAb), CCV2-2, was compared with the widely used FIPV3-70 mAb, both directed against canine coronavirus (CCoV), as a diagnostic and research tool. Western blot showed that both anti-CCoV mAbs only reacted with a protein of 50 kD, a weight consistent with the feline coronavirus (FCoV) viral nucleocapsid. A competitive inhibition enzyme-linked immunosorbent assay showed that the 2 recognized epitopes are distinct. Preincubation of CCV2-2 mAb with FCoV antigen suppressed the immunostaining. Formalin-fixed, paraffin-embedded sections from brains of 15 cats with the dry form of feline infectious peritonitis (FIP) were examined by immunohistochemistry. Immunohistochemistry was performed with both anti-CCoV mAbs, either on consecutive or on the same sections. A myeloid-histiocytic marker, MAC 387, was also used to identify FIP virus-infected cells. In all regions where MAC 387-positive cells were present, positive staining with the CCV2-2 mAb was systematically detected, except at some levels in 1 cat. In contrast, none or only a few cells were positive for the FIPV3-70 mAb. Double immunostaining showed macrophages that were immunopositive for either CCV2-2 alone or alternatively for CCV2-2 and FIPV3-70 mAbs. This reveals the coexistence of 2 cohorts of phagocytes whose FIP viral contents differed by the presence or absence of the FIPV3-70-recognized epitope. These findings provide evidence for antigenic heterogeneity in coronavirus nucleocapsid protein in FIP lesions, a result that is in line with molecular observations. In addition, we provide for the first time morphologic depiction of viral variants distribution in these lesions.
Poncelet
L
L
Anatomy/Embryology Department, CP 619, Faculty of Medicine, Free University of Brussels, Route de Lennik 808, Brussels, Belgium. lcponce@ulb.ac.be
Coppens
A
A
Peeters
D
D
Bianchi
E
E
Grant
C K
CK
Kadhim
H
H
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000940:Antigenic Variation; D015153:Blotting, Western / Q000662:veterinary; D001921:Brain / Q000821:virology; D002415:Cats; D000086462:Coronavirus Nucleocapsid Proteins; D016765:Coronavirus, Feline / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D016766:Feline Infectious Peritonitis / Q000276:immunology / Q000821:virology*; D005260:Female; D007150:Immunohistochemistry / Q000662:veterinary; D008297:Male; D008590:Meningoencephalitis / Q000276:immunology / Q000662:veterinary* / Q000821:virology; D019590:Nucleocapsid Proteins / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000086462:Coronavirus Nucleocapsid Proteins; D019590:Nucleocapsid Proteins