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Journal of Virology, March 2005, p. 3807-3821, Vol. 79, No. 6
0022-538X/05/$08.00+0 doi:10.1128/JVI.79.6.3807-3821.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Department of Pathology,1 Center for Biodefense and Emerging Infectious Diseases,2 Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas,4 Department of Arbovirology, Instituto Evandro Chagas, Ministry of Health, Belém, Brazil,3 Chicago Department of Public Health, Chicago, Illinois5
Received 5 August 2004/ Accepted 25 October 2004
The 3' noncoding region (3' NCR) of flaviviruses contains secondary and tertiary structures essential for virus replication. Previous studies of yellow fever virus (YFV) and dengue virus have found that modifications to the 3' NCR are sometimes associated with attenuation in vertebrate and/or mosquito hosts. The 3' NCRs of 117 isolates of South American YFV have been examined, and major deletions and/or duplications of conserved RNA structures have been identified in several wild-type isolates. Nineteen isolates (designated YF-XL isolates) from Brazil, Trinidad, and Venezuela, dating from 1973 to 2001, exhibited a 216-nucleotide (nt) duplication, yielding a tandem repeat of conserved hairpin, stem-loop, dumbbell, and pseudoknot structures. YF-XL isolates were found exclusively within one subclade of South American genotype I YFV. One Brazilian isolate exhibited, in addition to the 216-nt duplication, a deletion of a 40-nt repeated hairpin (RYF) motif (YF-XL-
RYF). To investigate the biological significance of these 3' NCR rearrangements, YF-XL-
RYF and YF-XL isolates, as well as other South American YFV isolates, were evaluated for three phenotypes: growth kinetics in cell culture, neuroinvasiveness in suckling mice, and ability to replicate and produce disseminated infections in Aedes aegypti mosquitoes. YF-XL-
RYF and YF-XL isolates showed growth kinetics and neuroinvasive characteristics comparable to those of typical South American YFV isolates, and mosquito infectivity trials demonstrated that both types of 3' NCR variants were capable of replication and dissemination in a laboratory-adapted colony of A. aegypti.
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