Guinea Fowl Coronavirus Diversity Has Phenotypic Consequences for Glycan and Tissue Binding

Guinea fowl coronavirus (GfCoV) causes fulminating enteritis that can result in a daily death rate of 20% in guinea fowl flocks. Here we studied GfCoV diversity and evaluated its phenotypic consequences. Over the period 2014-2016, affected guinea fowl flocks were sampled in France and avian coronavirus presence was confirmed by PCR on intestinal content and immunohistochemistry of intestinal tissue. Sequencing revealed 89% amino acid identity between the viral attachment protein S1 of GfCoV/2014 and the previously identified GfCoV/2011. To study the receptor interactions as a determinant for tropism and pathogenicity, recombinant S1 proteins were produced and analyzed by glycan and tissue arrays. Glycan array analysis revealed that viral attachment S1 proteins from GfCoV/2014 and GfCoV/2011 can, in addition to the previously elucidated biantennary diLacNAc receptor, bind to glycans capped with alpha 2,6-linked sialic acids. Interestingly, recombinant GfCoV/2014-S1 has an increased affinity for these glycans compared to GfCoV/2011-S1, which was in agreement with the increased avidity of GfCoV/2014-S1 for gastrointestinal tract tissues. Enzymatic removal of receptors from tissues before applying spike proteins confirmed the specificity of S1 tissue binding. Overall, we demonstrate that diversity in GfCoV S1 proteins results in differences in glycan and tissue binding properties.IMPORTANCE Avian coronaviruses cause major global problems in the poultry industry. As causative agents of huge economical losses, the detection and understanding of the molecular determinants of viral tropism is of ultimate importance. Here we set out to study those parameters and obtained in-depth insight in the virus-host interactions of guinea fowl coronavirus (GfCoV). Our data indicate that diversity in GfCoV viral attachment proteins result in differences in affinity for glycan receptors, as well as altered avidity for intestinal tract tissues, which might have consequences for its tissue tropism and pathogenesis in guinea fowls.