Tick-Borne Encephalitis Virus Sequenced Directly from Questing and Blood-Feeding Ticks Reveals Quasispecies VarianceReportar como inadecuado




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The increased distribution of the tick-borne encephalitis virus TBEV in Scandinavia highlights the importance of characterizing novel sequences within the natural foci. In this study, two TBEV strains: the Norwegian Mandal 2009 questing nymphs pool and the Swedish Saringe 2009 blood-fed nymph were sequenced and phylogenetically characterized. Interestingly, the sequence of Mandal 2009 revealed the shorter form of the TBEV genome, similar to the highly virulent Hypr strain, within the 3′ non-coding region 3′NCR. A different genomic structure was found in the 3′NCR of Saringe 2009, as in-depth analysis demonstrated TBEV variants with different lengths within the polyA tract. This shows that TBEV quasispecies exists in nature and indicates a putative shift in the quasispecies pool when the virus switches between invertebrate and vertebrate environments. This prompted us to further sequence and analyze the 3′NCRs of additional Scandinavian TBEV strains and control strains, Hypr and Neudoerfl. Toro 2003 and Habo 2011 contained mainly a short A3CA6 polyA tract. A similar pattern was observed for the human TBEV isolates 1993-783 and 1991-4944; however, one clone of 1991-4944 contained an A3CA11 polyA sequence, demonstrating that quasispecies with longer polyA could be present in human isolates. Neudoerfl has previously been reported to contain a polyA region, but to our surprise the re-sequenced genome contained two major quasispecies variants, both lacking the polyA tract. We speculate that the observed differences are important factors for the understanding of virulence, spread, and control of the TBEV.



Autor: Naveed Asghar, Pontus Lindblom , Wessam Melik , Richard Lindqvist, Mats Haglund, Pia Forsberg, Anna K. Överby , Åshild Andreass

Fuente: http://plos.srce.hr/



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