Assessing immune evasion potential and vaccine suitability of a feline panleukopenia virus strain

Abstract

Since the introduction of the feline panleukopenia virus (FPV) vaccine in China in 2011, it has played a crucial role in safeguarding the health of numerous pet cats by preventing FPV infections. However, an observed rise in FPV infections among cats previously vaccinated has prompted our investigation. Our laboratory has identified a specific FPV isolate, FPV-251, which raises concerns about its potential to evade the immune response. To validate this hypothesis, we conducted a correlational study on FPV-251. Ten sera samples were collected from ten cats two months after receiving the vaccine three times. These samples were prepared in the laboratory to assess their ability to neutralize FPV-251. Results indicated that the neutralization titers of the 10 sera ranged from 1:313.7 to 1:1051.0, with an average titer of 1:627.4. Considering the diversity and complexity of clinical practice, we expanded our study to include 86 sera samples collected from cats at the clinic after three-time immunizations. Among these, 8 out of 43 sera collected after one year post three-time immunizations and 5 out of 43 sera collected within one year post three-time immunizations exhibited a neutralization index (NI) of less than 50 against FPV-251. Despite its potential immune evasion capabilities, immunization with inactivated FPV-251 demonstrated effectiveness in providing substantial protection for cats. This was evident from the high levels of sera antibodies against FPV-251 in cats with FPV-251 immunization, as well as their ability to survive and maintain good health after being challenged with FPV-251. Furthermore, sera antibodies from immunized cats displayed the ability to neutralize the other five FPV isolates, indicating a robust cross-protection capacity of the FPV-251 vaccine. Our research findings suggest that although FPV-251 may exhibit certain immune evasion capabilities, it holds significant potential for development into a vaccine to protect pet cats from FPV infection.