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Journal of Virology, February 2000, p. 1079-1084, Vol. 74, No. 3
Metabolic Diseases and Immunology Research
Unit, National Animal Disease Center, Agricultural Research Service,
U. S. Department of Agriculture, Ames, Iowa
50010,1 and Laboratory of Infectious
Diseases, National Institute of Allergy and Infectious Diseases,
National Institutes of Health, Bethesda, Maryland
208922
Received 30 June 1999/Accepted 10 December 1999
Feline calicivirus (FCV) strains can show significant antigenic
variation when tested for cross-reactivity with antisera produced against other FCV strains. Previous work has demonstrated the presence
of hypervariable amino acid sequences in the capsid protein of FCV
(designated regions C and E) that were postulated to constitute the
major antigenic determinants of the virus. To examine the involvement
of hypervariable sequences in determining the antigenic phenotype, the
nucleotide sequences encoding the E regions from three antigenically
distinct parental FCV strains (CFI, KCD, and NADC) were exchanged for
the equivalent sequences in an FCV Urbana strain infectious cDNA clone.
Two of the three constructs were recovered as viable, chimeric viruses.
In six additional constructs, of which three were recovered as viable
virus, the E region from the parental viruses was divided into left
(N-terminal) and right (C-terminal) halves and engineered into the
infectious clone. A final viable construct contained the C, D, and E
regions of the NADC parental strain. Recovered chimeric viruses showed
considerable antigenic variation from the parental viruses when tested
against parental hyperimmune serum. No domain exchange was able to
confer complete recognition by parental antiserum with the exception of
the KCD E region exchange, which was neutralized at a near-homologous titer with KCD antiserum. These data demonstrate that it is possible to
recover engineered chimeric FCV strains that possess altered antigenic
characteristics. Furthermore, the E hypervariable region of the capsid
protein appears to play a major role in the formation of the antigenic
structure of the virion where conformational epitopes may be more
important than linear in viral neutralization.
0022-538X/00/$04.00+0
Recovery and Altered Neutralization Specificities
of Chimeric Viruses Containing Capsid Protein Domain Exchanges from
Antigenically Distinct Strains of Feline Calicivirus
*
Corresponding author. Mailing address: National Animal
Disease Center, 2300 Dayton Rd., Ames, IA 50010. Phone: (515) 663-7730. Fax: (515) 663-7458. E-mail:
jneill{at}nadc.ars.usda.gov.
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