Feline coronavirus with and without spike gene mutations detected by real-time RT-PCRs in cats with feline infectious peritonitis. Issue 8 (August 2020)

• Record Type: Journal Article
• Authors: Emmler, Laura; Felten, Sandra; Matiasek, Kaspar; Balzer, Hans-Joerg; Pantchev, Nikola; Leutenegger, Christian; Hartmann, Katrin
• Is Part Of: Journal of feline medicine and surgery. Volume 22:Issue 8(2020)
• Page Start: 791
• Page End: 799
• Publication Date: 2020-08
• Subjects: FCoV -- FIP -- RT-PCR -- S gene -- IHC -- immunohistochemistry; Cats -- Diseases -- Periodicals; Cats -- Surgery -- Periodicals; 636.8089
• DOI: 10.1177/1098612X19886671
• Languages: English
• ISSNs: 1098-612X

Abstract

Objectives: Feline infectious peritonitis (FIP) emerges when feline coronaviruses (FCoVs) mutate within their host to a highly virulent biotype and the immune response is not able to control the infection. FCoV spike ( S ) gene mutations are considered to contribute to the change in virulence by enabling FCoV infection of and replication in macrophages. This study investigated the presence of FCoV with and without S gene mutations in cats with FIP using two different real-time RT-PCRs on different samples obtained under clinical conditions. Methods: Fine-needle aspirates (FNAs) and incisional biopsies (IBs) of popliteal and mesenteric lymph nodes, liver, spleen, omentum and kidneys (each n = 20), EDTA blood (n = 13), buffy coat smears (n = 13), serum (n = 11), effusion (n = 14), cerebrospinal fluid (n = 16), aqueous humour (n = 20) and peritoneal lavage (n = 6) were obtained from 20 cats with FIP diagnosed by immunohistochemistry. Samples were examined by RT-PCR targeting the FCoV 7b gene, detecting all FCoV, and S gene mutation RT-PCR targeting mutations in nucleotides 23531 and 23537. The prevalence of FCoV detected in each sample type was calculated. Results: In 20/20 cats, FCoV with S gene mutations was present in at least one sample, but there was variation in which sample was positive. FCoV with mutations in the S gene was most frequently found in effusion (64%, 95% confidence interval [CI] 39–89), followed by spleen, omentum and kidney IBs (50%, 95% CI 28–72), mesenteric lymph node IBs and FNAs (45%, 95% CI 23–67), and FNAs of spleen and liver and liver IBs (40%, 95% CI 19–62). Conclusions and relevance: In these 20 cats with FIP, FCoVs with S gene mutations were found in every cat in at least one tissue or fluid sample. This highlights the association between mutated S gene and systemic FCoV spread. Examining a combination of different samples increased the probability of finding FCoV with the mutated S gene.