Antibodies against Crandell Rees Feline Kidney (CRFK) Cell Line Antigens, α‐Enolase,and Annexin A2 in Vaccinated and CRFK Hyperinoculated Cats

Background: Cats inoculated with feline herpesvirus 1, calicivirus, and panleukopenia (FVRCP) vaccines grown on the Crandell Rees feline kidney (CRFK) cell line have been shown to develop anti‐CRFK antibodies. The identities of common CRFK antigens are unknown. Hypothesis: Cats inoculated with CRFK lysates and FVRCP vaccines will develop autoantibodies measurable by Western blot immunoassay. Antigens associated with these antibodies can be isolated for further study. Animals: One CRFK hyperinoculated rabbit, 44 age‐matched unvaccinated kittens purchased from a commercial vendor. Methods: Commonly recognized CRFK antigens were identified by comparison of Western blot immunoassays using sera from a hyperinoculated rabbit and kittens inoculated with CRFK lysate or 1 of 4 commercially available FVRCP vaccines. Antigens were purified from CRFK lysates and sequenced. Antigen recognition was confirmed by Western blot immunoassay and indirect ELISA for 2 proteins using sera from CRFK and FVRCP inoculated kittens. Results: CRFK antigens 47, 40, and 38 kD in size were identified. Protein isolation and sequencing identified 3 CRFK proteins as α‐enolase, annexin A2, and macrophage capping protein (MCP). Sera from FVRCP and CRFK inoculated cats were confirmed to recognize annexin A2 and α‐enolase by Western blot immunoassay and indirect ELISA. Conclusions and Clinical Relevance: This study validated the use of Western blot immunoassay for detection of antibodies against CRFK proteins and identified 3 CRFK antigens. In humans, α‐enolase antibodies are nephritogenic; α‐enolase and annexin A2 antibodies have been associated with autoimmune diseases. Further research will be necessary to determine the clinical relevance of these findings.