Isolation of a feline-derived feline panleukopenia virus with an A300P substitution in the VP2 protein and confrmation of its pathogenicity in dogs

Feline panleukopenia virus(FPV)is a single-stranded DNA virus that can infect cats and cause feline panleukopenia,which is a highly contagious and fatal disease in felines.The sequence of FPV is highly variable,and mutations in the amino acids of its capsid protein play crucial roles in altering viral virulence,immunogenicity,host selection,and other abilities.In this study,the epidemiology of FPV was studied using 746 gastrointestinal swab samples derived from cats that presented gastrointestinal symptoms specifcally,diarrhea or vomiting during the period spanning from 2018 to 2022.The overall prevalence of FPV-positive patients among these samples was determined to be 45.4%.Capsid(virion)protein 2(VP2)gene of each FPV-positive sample was sequenced and amplifed,yielding 65 VP2 sequences.Among them,six VP2 gene sequences were detected in the majority of the samples test positive for FPV,and these positive samples originated from a diverse range of geographical locations.These isolates were named FPV-6,FPV-10,FPV-15,FPV-251,FPV-271 and FPV-S2.Additionally,the substitution of Ala300Pro(A300P)in VP2 was detected for the frst time in feline-derived FPV(FPV-251).FPV-251 isolate,with this substitution in VP2 protein,exhibited stable proliferative capacity in Madin-Darby canine kidney(MDCK)cells and A72 cells.FPV-271 was selected as the FPV control isolate due to its single amino acid diference from VP2 protein of FPV-251 at position 300(FPV-271 has alanine,while FPV-251 has proline).After oral infection,both FPV-251 and FPV-271 isolates caused feline panleukopenia,which is characterized by clinical signs of enterocolitis.However,FPV-251 can infect dogs through the oral route and cause gastrointestinal(GI)symptoms with lesions in the intestine and mesenteric lymph nodes(MLNs)of infected dogs.This is the frst report on the presence of an A300P substitution in VP2 protein of feline-derived FPV.Additionally,FPV isolate with a substitution of A300P at VP2 protein demonstrated efcient replication capabilities in canine cell lines and the ability to infect dogs.

Analysis of Genetic Variation of VP2 Gene in 6 FPV Strainsin China

In order to understand the variation of FPV strains in the Jinan area, Shandong Province, China, the VP2 gene of 6 FPV strains was sequenced, and the analysis of the genetic relationship, evolution and main functional site variation was carried out. It was found that FPV-XY2, FPV-XY3 and FPV-XY6 were the same strain with 100% homology, and also close to FPV-XY1, and the homology between FPV-XY4 and FPV-XY5 was close. The homology between the reference strain and the test strain was over 99.3%. According to the evolutionary analysis, the genetic relationship among FPV-XY1, FPV-XY2, FPV-XY3, FPV-XY6 was close, and the genetic relationship between FPV-XY4 and FPV-XY5 was close, and the result was similar to the homologous result. Compared with the VP2 amino acid sequence of the standard strain FPV-CU4, the VP2 protein of all the test strains changed from I to t on the 101st Amino acid, this may be the cause of immune failure in these 6 cases;the change of a to s in the 91st amino acid position of FPV-XY1, FPV-XY2, FPV-XY3, FPV-XY6 may be the cause of enhanced virulence of FPV. This study provides a reference for exploring the epidemic law of FP in the Jinan area, the standard of FP treatment plan and the research and development of FPV subunit vaccine.