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. 2013 Dec 15:208 Suppl 3:S227-37.
doi: 10.1093/infdis/jit477.

Replacement and positive evolution of subtype A and B respiratory syncytial virus G-protein genotypes from 1997-2012 in South Africa

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Replacement and positive evolution of subtype A and B respiratory syncytial virus G-protein genotypes from 1997-2012 in South Africa

Marthi A Pretorius et al. J Infect Dis. .

Abstract

Background: Of the respiratory syncytial virus (RSV) genotypes previously described in South Africa during 1997-2002, only GA2 and GA5 persisted until 2006, with BA having replaced all previous RSV-B genotypes. This poses the question whether RSV-A is more stable than RSV-B and whether positive selection drives evolution of genotypes.

Methods: RSV-positive specimens were randomly selected during 2009-2012, subtyped, sequenced, and compared to RSV recovered from specimens obtained during 1997-2001 and 2006-2009. Bayesian phylogenetic analysis was performed on the G-protein.

Results: Phylogenetic analysis indicated that RSV-A genotype GA2 dissolved to form SAA2 (unique to South Africa), NA1 and NA2 (identified in Japan), and ON1 (identified in Canada and having a 72-bp insertion) and that GA5 drifted from 1999-2012 to form 3 subgenotypes (GA5 I-III). RSV-B genotypes all had the 60-bp insertion typical of BA genotypes but clustered into subgenotypes BA8-10. Positive selection was identified in the G-protein of both subtypes, but RSV-A's rate of evolution was slower than that of RSV-B, with the most recent common ancestors dating from 1945 and 1951, respectively. Seven new positively selected sites were identified in South African strains, 2 for RSV-A and 5 for RSV-B.

Conclusion: Positive selection drove both RSV-A and -B genotypes to evolve, resulting in replacement of all genotypes over the 15-year study period in South Africa.

Keywords: evolutionary rate; genotypes; positive selection; respiratory syncytial virus.

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