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Journal of Virology, March 1999, p. 1878-1884, Vol. 73, No. 3
Department of Virology and Molecular
Biology1 and
Department of Epidemiology
and Biostatistics,2 St. Jude Children's
Research Hospital, Memphis, Tennessee 38105-2794
Received 9 March 1998/Accepted 11 November 1998
In 1979, an H1N1 avian influenza virus crossed the species barrier,
establishing a new lineage in European swine. Because there is no
direct or serologic evidence of previous H1N1 strains in these pigs,
these isolates provide a model for studying early evolution of
influenza viruses. The evolutionary rates of both the coding and
noncoding changes of the H1N1 swine strains are higher than those of
human and classic swine influenza A viruses. In addition, early H1N1
swine isolates show a marked plaque heterogeneity that consistently
appears after a few passages. The presence of a mutator mutation was
postulated (C. Scholtissek, S. Ludwig, and W. M. Fitch, Arch.
Virol. 131:237-250, 1993) to account for these observations and the
successful establishment of an avian H1N1 strain in swine. To address
this question, we calculated the mutation rates of A/Mallard/New
York/6750/78 (H2N2) and A/Swine/Germany/2/81 (H1N1) by using the
frequency of amantadine-resistant mutants. To account for the inherent
variability of estimated mutation rates, we used a probabilistic model
for the statistical analysis. The resulting estimated mutation rates of
the two strains were not significantly different. Therefore, an
increased mutation rate due to the presence of a mutator mutation is
unlikely to have led to the successful introduction of avian H1N1
viruses in European swine.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Independence of Evolutionary and Mutational Rates
after Transmission of Avian Influenza Viruses to Swine
and
*
Corresponding author. Mailing address: Department of
Virology and Molecular Biology, St. Jude Children's Research Hospital, 332 N. Lauderdale St., Memphis, TN 38105-2794. Phone: (901) 495-3400. Fax: (901) 495-2622. E-mail: Robert.Webster{at}stjude.org.
Present address: Waldstrasse 53, Linden-Leihgestern 35440, Germany.
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