Phylogenetic and virulence analysis of tick-borne encephalitis virus field isolates from Switzerland

Gäumann, Rahel; Růžek, Daniel; Mühlemann, Kathrin; Strasser, Marc; Beuret, Christian M (2011). Phylogenetic and virulence analysis of tick-borne encephalitis virus field isolates from Switzerland. Journal of medical virology, 83(5), pp. 853-63. Hoboken, N.J.: Wiley-Liss 10.1002/jmv.21993

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Tick-borne encephalitis (TBE) is an endemic disease in Switzerland, with about 110-120 reported human cases each year. Endemic areas are found throughout the country. However, the viruses circulating in Switzerland have not been characterized so far. In this study, the complete envelope (E) protein sequences and phylogenetic classification of 72 TBE viruses found in Ixodes ricinus ticks sampled at 39 foci throughout Switzerland were analyzed. All isolates belonged to the European subtype and were highly related (mean pairwise sequence identity of 97.8% at the nucleotide and 99.6% at the amino acid level of the E protein). Sixty-four isolates were characterized in vitro with respect to their plaque phenotype. More than half (57.8%) of isolates produced a mixture of plaques of different sizes, reflecting a heterogeneous population of virus variants. Isolates consistently forming plaques of small size were associated with recently detected endemic foci with no or only sporadic reports of clinical cases. All of six virus isolates investigated in an in vivo mouse model were highly neurovirulent (100% mortality) but exhibited a relatively low level of neuroinvasiveness, with mouse survival rates ranging from 50% to 100%. Therefore, TBE viruses circulating in Switzerland belong to the European subtype and are closely related. In vitro and in vivo surrogates suggest a high proportion of isolates with a relatively low level of virulence, which is in agreement with a hypothesized high proportion of subclinical or mild TBE infections.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Service Sector > Institute for Infectious Diseases > Bacteriology FB)
04 Faculty of Medicine > Service Sector > Institute for Infectious Diseases

UniBE Contributor:

Gäumann, Rahel and Mühlemann, Kathrin

ISSN:

0146-6615

Publisher:

Wiley-Liss

Language:

English

Submitter:

Factscience Import

Date Deposited:

04 Oct 2013 14:24

Last Modified:

17 Mar 2015 21:04

Publisher DOI:

10.1002/jmv.21993

PubMed ID:

21412794

Web of Science ID:

000288464400016

URI:

https://boris.unibe.ch/id/eprint/8448 (FactScience: 213995)

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