Poster Presentation 8th Australasian Virology Society Meeting and 11th Annual Meeting of the Australian Centre for Hepatitis & HIV Virology Meeting 2015

FUNCTIONAL ANALYSIS OF THREE DISTINCT CHEMOKINE-BINDING PROTEINS ENCODED BY THE PARAPOXVIRUS OF RED DEER IN NEW ZEALAND (#192)

Saeed Sharif 1 , Sheree Clifton 1 , Yoshio Nakatani 1 , Kurt Krause 2 , Nicola Real 1 , Lyn Wise 1 , Andy Mercer 1 , Stephen Fleming 1
  1. Department of Microbiology & Immunology, University of Otago, Dunedin, New Zealand
  2. Department of Biochemistry, University of Otago, Dunedin, New Zealand

Parapoxvirus of red deer in New Zealand (PVNZ) is a relatively new species within the Parapoxvirus (PPV) genus, which cause localized skin diseases. The genomes of PPVs encode a number of immunomodulatory factors that temporarily suppress the host’s immune response and facilitate viral replication. Many of the PPVs have been shown to encode a chemokine-binding protein (CBP), which can bind to chemokines and disrupt recruitment of host immune cells. Interestingly, unlike other PPVs, PVNZ encodes three distinct CBP genes (112.0, 112.3 and 112.6). Homology modeling of the PVNZ-CBPs against the crystal structure of the CBP from Orf virus (ORFV) reveals that, although the sequence identity between the ORFV and PVNZ CBPs is low (27-36%), the core beta-sandwich folds are conserved thus certain chemokine binding activity is predicted for these viral proteins.

In this study, the binding activities of recombinant PVNZ-CBPs were evaluated against various chemokines using an indirect ELISA and surface plasmon resonance assay. The binding assays showed that each PVNZ-CBP has a unique chemokine-binding spectrum. In general, PVNZ-CBP 112.3 binds to α-chemokines selectively, while PVNZ-CBP 112.6 has strong binding affinity with β-chemokines. Remarkably, PVNZ-CBP 112.0 had no or very weak binding against all chemokines tested. The ability of the CBPs to interfere with neutrophil chemotaxis was then evaluated using transwell migration assay. The transwell model confirmed that PVNZ-CBP 112.3 can reduce neutrophil migration in response to classic neutrophil-attractant α-chemokines CXCL1 and CXCL2. In addition, PVNZ-CBP 112.6 decreased neutrophil transmigration towards the β-chemokine CCL3.

This study is the first to show that CBPs derived from PVNZ are functionally active and are antagonists for key neutrophil chemotactic proteins. These findings suggest that the CBPs may play a role in limiting neutrophil trafficking to the site of PVNZ infection, and that the proteins could be used therapeutically to reduce inflammation or neutrophilia.