Large-Scale Spatial and Temporal Genetic Diversity of Feline Calicivirus

Abstract

Feline calicivirus (FCV) is an important pathogen of domestic cats and a frequently used model of human caliciviruses. Here we use an epidemiologically rigorous sampling framework to describe for the first time the phylodynamics of a calicivirus at regional and national scales. A large number of FCV strains cocirculated in the United Kingdom at the national and community levels, with no strain comprising more than 5% and 14% of these populations, respectively. The majority of strains exhibited a relatively restricted geographical range, with only two strains (one field virus and one vaccine virus) spreading further than 100 km. None of the field strains were identified outside the United Kingdom. Temporally, while some strains persisted locally for the majority of the study, others may have become locally extinct. Evolutionary analysis revealed a radial phylogeny with little bootstrap support for nodes above the strain level. In most cases, spatially and temporally diverse strains intermingled in the phylogeny. Together, these data suggest that current FCV evolution is not associated with selective competition among strains. Rather, the genetic and antigenic landscape in each geographical location is highly complex, with many strains cocirculating. These variants likely exist at the community level by a combination of de novo evolution and occasional gene flow from the wider national population. This complexity provides a benchmark, for the first time, against which vaccine cross-protection at both local and national levels can be judged.

Antiviral effect of mefloquine on feline calicivirus in vitro

“…FCV F9 was chosen for screening due to its well characterised in vitro growth properties, however it is unclear whether FCV F9 used in the current study is representative of currently circulating viruses, due to natural viral evolution of circulating field viruses over the last half century in face of vaccination with F9 based vaccines, or cell culture adaptation, as can occur with high passage number. It is therefore possible that results obtained against FCV F9 may not be representative of efficacy against circulating strains, particularly given the known genetic heterogeneity of FCV (Coyne et al, 2012). Additional antiviral screening was performed against a panel of seven recent FCV isolates from Australia.…”

Protective Efficacy of the Calicivirus Valency of the Leucofeligen Vaccine against a Virulent Heterologous Challenge in Kittens

“…It seems that the maximum dissimilarity detected within the calicivirus pool is in the order of 30% [5], and one study demonstrated that FCV-255 and F9 have only 70% homology within region E of the capsid protein, which is a similar level of relatedness to that seen with other highly diverse strains including some of the highly virulent strains examined in that study [9]. In one seroneutralisation study performed with sera raised to FCV-255 and F9, it was clear that amongst the field strains neutralised by the highest antibody dilution titres of one of the sera there was rarely a corresponding high titre for the other serum [10].…”

“…The replication of FCV, like other RNA viruses in general, results in a high proportion of genomic as well as antigenic variants. Indeed the overall identity of FCV isolates collected worldwide was reported to be approximately 80% for the variable and immunodominant regions C to E of the capsid gene [4, 5]. This genomic diversity gives rise to antigenic variants and argues for the importance of cross-reactive vaccines that can provide protection against antigenically distinct FCV strains.…”

Antiviral effect of lithium chloride on feline calicivirus in vitro

“…Accordingly, older vaccines cannot provide crossprotection against newer strains [22,23]. In addition, the genetic and antigenic landscape is highly complex in each geographical location; thus, vaccine application must be based on an assessment of the situation at both the local and national level [9]. FCV vaccines are generally effective at reducing the severity and duration of clinical signs but do not prevent infection or shedding [24].…”