Neutralizing Feature of Commercially Available Feline Calicivirus (FCV) Vaccine Immune Sera against FCV Field Isolates

Abstract

ABSTRACT. Four types of commercially available feline calicivirus (FCV) vaccine were compared in terms of their efficacy on the basis of the ability of the sera of specific-pathogen-free cats immunized by two injections of each type of vaccine to neutralize FCV field isolates. Each vaccine immune serum neutralized relatively well strains F4, F9, and 255, which were FCV laboratory strains. As to 36 strains of field isolates, however, vaccines A, B, C, and D immune sera did not neutralize 18-20 of the strains (50.0%-55.6%), 19-22 of the strains (52.8%-61.1%), 22-25 of the strains (61.1%-69.4%), and 8-16 of the strains (22.2%-44.4%), respectively. These results indicate that there is much difference in neutralizing antigenicity between the existing vaccine strains and the FCV strains that are prevalent in Japan, suggesting the need for improvement of FCV vaccines.-KEY WORDS: feline calicivirus, neutralizing antigenicity, vaccine immune serum.J. Vet. Med. Sci. 61(3): 299-301, 1999 The FCV used were laboratory strains F4, F9, and 255 and 36 strains of field isolates prepared in Japan in 1991 [9]. Of these 36 strains of field isolates, 23 isolates, 7 isolates, 2 isolates, and each of the remaining 4 isolates were obtained from the oral or nasal swabs of the cats suspected of having viral respiratory diseases, which had been maintained in Tokyo, and Tottori, Yamagata, Ehime, Okayama, Kanagawa, and Saitama Prefectures, respectively. All of the field isolates were purified by three rounds of plaque cloning and propagated in Crandell feline kidney (CrFK) cells.The immune sera were prepared from eight 12-monthold SPF cats immunized by two injections, with an interval of 3 weeks, of each type of feline triple combined vaccine. Serum samples collected 3 weeks after the second injection were used as the immune sera.Serial two-fold dilutions of the test sera were mixed with an equal volume of an FCV strain suspension containing approximately 200 TCID 50 and the mixtures were incubated at 37°C for 60 min. Each mixture was then inoculated into the CrFK cell cultures in flat-bottomed microplates, and incubated in an atmosphere of 5% CO 2 in air at 37°C for 4 days. Each serum dilution was plated in duplicate. The antibody titer was expressed as the reciprocal of the highest dilution of serum that completely inhibited a viral cytopathic effect. Table 1 shows the neutralizing antibody titers of FCV vaccine immune sera against three FCV laboratory strains and 36 strains of FCV field isolates. Each immune serum neutralized three laboratory strains well, with the exception of the reactivity of the vaccine C immune serum against strain 255. The F9 strain particularly was neutralized well with every immune serum. Against the 36 field isolates, however, the immune sera showed various neutralizing antibody titers, and there were eight isolates (91-4, 91-16, 91-19, 91-28, 91-29, 91-34, 91-36, and 91-38) which were not neutralized by any immune serum. Table 2 shows the Feline calicivirus (FCV) is an important cause of acute oral and resp...

Recent Epidemiological Status of Feline Upper Respiratory Infections in Japan.

“…Although there is probably no doubt that an introduction of novel antigenic vaccine strains into existing circumstances is immediately potent [3,11,13], they do not appear to protect against all FCV strains as also revealed here (Table 2) and another vicious circle may develop in time. As commented in one review article [1], a fundamental improvement of vaccine designation, such as a peptide vaccine designed from the conserved antigenic region [24], is desired.…”

“…Recently Hohdatsu et al [11] also reported antigenic disagreement between commercially available vaccine strains and field FCV strains in Japan. They analyzed FCV isolates in early 1990s and showed a vaccine incorporating bivalent FCV strains had produced more cross-reactive antibodies in cats than the monovalent vaccine products.…”

An isolated epizootic of hemorrhagic-like fever in cats caused by a novel and highly virulent strain of feline calicivirus

“…Even though many ®eld strains of FCV do not cross-react with the almost universal FCV-F9 vaccine strain (Pedersen et al, 1983;Knowles et al, 1990;Pedersen and Hawkins, 1995;Laruritzen et al, 1997;Hohdatsu et al, 1999), none of these strains have been of this virulence and the consequences have therefore been small. Antibodies against the universal FCV-F9 vaccine strain also did not signi®cantly cross-react with FCV-Ari, and laboratory cats immunized by the oral route with FCV-F9 6 weeks prior to challenge-exposure possessed only a small measure of immunity.…”

Serum survey for antibodies to coronavirus, herpesvirus, calicivirus, and parvovirus in domestics cats from Rio Grande do Sul, Brazil

“…Blood samples were collected by cephalic or jugular vein puncturing and sent to the virology and immunology laboratory of UFPel where they were centrifuged for serum separation. The sera were submitted to serum neutralization test (SN) according to Hohdatsu et al (1999), with a few modifications. Serum serial dilutions from 1:4 to 1:256 were incubated with 100 TCID 50 of the virus to which the presence of neutralizing antibodies was investigated.…”