Polarisation of Major Histocompatibility Complex II Host Genotype with Pathogenesis of European Brown Hare Syndrome Virus

Christos Iacovakis,George Valiakos,Liljana Petrovska,Labrini V Athanasiou,Themis Giannoulis,Vassiliki Spyrou,Alexios Giannakopoulos,Charalambos Billinis,Periklis Birtsas,Dimitrios Bogdanos,Anne Sofie Hammer,Costas Stamatis,Katerina A Moutou,Maria Kantere,Duncan Hannant,Charlotte M Salomonsen,Zissis Mamuris,Tommy Asferg,Antonia Touloudi

doi:10.1371/journal.pone.0074360

Abstract

A study was conducted in order to determine the occurrence of European Brown Hare Syndrome virus (EBHSV) in Denmark and possible relation between disease pathogenesis and Major Histocompatibility Complex (MHC) host genotype. Liver samples were examined from 170 brown hares (hunted, found sick or dead), collected between 2004 and 2009. Macroscopical and histopathological findings consistent with EBHS were detected in 24 (14.1%) hares; 35 (20.6%) had liver lesions not typical of the syndrome, 50 (29.4%) had lesions in other tissues and 61 (35.9%) had no lesions. Sixty five (38.2%) of 170 samples were found to be EBHSV-positive (RT-PCR, VP60 gene). In order to investigate associations between viral pathogenesis and host genotype, variation within the exon 2 DQA gene of MHC was assessed. DQA exon 2 analysis revealed the occurrence of seven different alleles in Denmark. Consistent with other populations examined so far in Europe, observed heterozygosity of DQA (H o = 0.1180) was lower than expected (H e = 0.5835). The overall variation for both nucleotide and amino acid differences (2.9% and 14.9%, respectively) were lower in Denmark than those assessed in other European countries (8.3% and 16.9%, respectively). Within the peptide binding region codons the number of nonsynonymous substitutions (dN) was much higher than synonymous substitutions (dS), which would be expected for MHC alleles under balancing selection. Allele frequencies did not significantly differ between EBHSV-positive and -negative hares. However, allele Leeu-DQA*30 was detected in significantly higher (P = 0.000006) frequency among the positive hares found dead with severe histopathological lesions than among those found sick or apparently healthy. In contrast, the latter group was characterized by a higher frequency of the allele Leeu-DQA*14 as well as the proportion of heterozygous individuals (P = 0.000006 and P = 0.027). These data reveal a polarisation between EBHSV pathogenesis and MHC class II genotype within the European brown hare in Denmark.

Highlights

The European brown hare (Lepus europaeus) is thought to have evolved on the open steppe grasslands of Eurasia and has adapted to mixed arable agriculture [1]
Regarding European Brown Hare Syndrome virus (EBHSV) positive hares without typical lesions of European brown hare syndrome (EBHS), 23 (35.4%) had liver lesions not typical of the syndrome, 13 (20%) had other lesions and the eleven (16.9%) apparently healthy hares, that were shot during hunting, had no lesions
We examined the level of genetic diversity of the brown hare from different regions of Denmark with regard to the second exon of the Major Histocompatibility Complex (MHC) DQA locus, which is one of the most polymorphic class II loci

Summary

Introduction

The European brown hare (Lepus europaeus) is thought to have evolved on the open steppe grasslands of Eurasia and has adapted to mixed arable agriculture [1]. It is widespread throughout Europe and occurs in a variety of habitats ranging from Mediterranean to subarctic regions and from sea level to an altitude of c.2200 m. It has been successfully introduced into exotic temperate environments (e.g. Argentina, North America and New Zealand) and thrives on tropical and sub-Antarctic islands [2].

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