Feline coronavirus (FCoV) exists as two different genotypes, FCoV type I and II, each including two biotypes, feline enteric coronavirus (FECV) and feline infectious peritonitis virus (FIPV), the latter being a virulent variant originating from the former virus. Recently, two amino acid substitutions, M1058L and S1060A, within the spike protein have been associated to the FECV/FIPV virulence change. In this study, we have analysed the frequency of detection of such mutations in FIPV and FECV strains circulating in Italian cats and obtained information about their evolutionary relationships with reference isolates. A total of 40 FCoV strains, including 19 strains from effusions or tissue samples of FIP cats and 21 strains from faecal samples of non-FIP cats, were analysed. Mutation M1058L was detected in 16/18 FCoV-I and 1/1 FCoV-II strains associated with FIP, while change S1060A was presented by two FIPV strains. By phylogenetic analysis, FCoV sequences clustered according to the genotype but not according to the biotype, with FECV/FIPV strains recovered from the same animal being closely related. Further studies are needed to better define the genetic signatures associated with the FECV/FIPV virulence shift.

猫冠状病毒（FCoV）有两种不同的基因型，即FCoV I型和II型，每种都包括两种生物型，即猫肠冠状病毒（FECV）和猫传染性腹膜炎病毒（FIPV），后者是源自前一种病毒的有毒变体。最近，刺突蛋白中的两个氨基酸取代，M1058L和S1060A与FECV / FIPV毒力变化相关。在这项研究中，我们分析了在意大利猫中传播的FIPV和FECV菌株中检测到此类突变的频率，并获得了有关它们与参考分离株的进化关系的信息。共分析了40株FCoV菌株，其中包括19株来自FIP猫的积液或组织样品的菌株和21株来自非FIP猫的粪便样品的菌株。在与FIP相关的16/18 FCoV-I和1/1 FCoV-II菌株中检测到突变M1058L，而两个FIPV菌株呈现S1060A变化。通过系统发育分析，FCoV序列根据基因型而不是根据生物类型成簇，与从同一动物中回收的FECV / FIPV菌株密切相关。需要进一步研究以更好地定义与FECV / FIPV毒力变化相关的遗传特征。