Comparison of serological and sequencebased methods for typing feline calicivirus isolates from vaccine failures

Abstract

Feline calicivirus (FCV) can be typed by exploiting antigenic differences between isolates or, more recently, by the sequence analysis of a hypervariable region of the virus's capsid gene. These two methods were used to characterise FCV isolates from 20 vaccine failures which occurred after the use of a commercial, live-attenuated vaccine. Using virus neutralisation, the isolates showed a spectrum of relatedness to the vaccine; depending on the criterion adopted for identity, 10 to 40 per cent of them appeared to be similar to the vaccine virus. Using sequence analysis, the isolates fell into one of two categories; 20 per cent had a similar sequence to the vaccine (0-67 to 2-67 per cent distant), and the remainder had a dissimilar sequence (21-3 to 36-0 per cent distant). Sequence analysis identified one cat that appeared to be infected with two distinct FCVs. The serological and sequence-based typing methods gave the same result in 80 to 95 per cent of individual cases, depending on the criterion adopted for serological identity. It is suggested that molecular typing is a more definitive method for characterising the relatedness of FCV isolates.

Feline calicivirus

“…As a result, it has not proved possible to identify groupings of FCV either on spatial (except possibly Japan), temporal or clinical grounds, and the virus is generally considered to exist as multiple strains that are all members of a single diverse genotype. The definition of "strain" is perhaps somewhat arbitrary, but has been defined by some as FCV isolates that are > 20% different based on nucleotide sequence of capsid region E [84,87,88].…”

“…Parenteral modified-live FCV vaccines have been associated with clinical signs in the immediate period postvaccination. Most of these appear to be due to coincidental infection with field virus although in some cases, sequence analysis has shown that vaccine virus may be involved [84,87]. Vaccine virus has also occasionally been detected circulating in the cat population, though the significance of this is not yet known [77,88,89].…”

Large-Scale Spatial and Temporal Genetic Diversity of Feline Calicivirus

“…To assign sequences to strains, we used the previously defined nucleotide distance threshold of 20% for hypervariable region E of the capsid (31,35). Pairwise genetic distances between sequences were calculated using the Jukes-Cantor approach as implemented in MEGAv4.0 (47).…”

“…Nucleotide sequences of the variable and immunodominant regions C to E of the capsid gene (44) differ at more than 20% of sites when epidemiologically unrelated viruses are compared, and these are considered distinct strains (33). Epidemiologically related viruses such as those found in acute outbreaks of disease are usually less than 1 to 2% divergent (and rarely more than 5% divergent) and are considered variants of the same strain (31,35). However, during endemic infections, such as those that exist in some household colonies, variants of a single strain have been shown to vary by up to 18% (7).…”

Hemocytes Are Sites of Enteric Virus Persistence within Oysters

“…For PV, primers P6 (5Ј-CCTCCGGCCCCTGAATG-3Ј) and P7 (5Ј-ACCGGATGGCCAATCCAA-3Ј) were used to generate a 197-bp amplicon, as originally described by Jaykus et al (26). For feline calicivirus, primer 4 (5Ј-TTGCAACTGATTATATTGTTCCTGG-3Ј) and primer 5 (5Ј-GC AGTGTTGGATATTTTCTTGTCACC-3Ј) were used to generate a 243-bp amplicon, as originally described by Radford et al (41). For HAV, primers HAV 2949 (5Ј-TATTTGTCTGTCACAGAACAATCAG-3Ј) and 3192 (5Ј-AGGAGG TGGAAGCACTTCATTTGA-3Ј) were used to generate a 267-bp amplicon, as previously described (37,45).…”