Characterisation of tropomyosin and paramyosin as vaccine candidate molecules for the poultry red mite, Dermanyssus gallinae

Background: Dermanyssus gallinae is the most economically important haematophagous ectoparasite in commercial egg laying flocks worldwide. It infests the hens during the night where it causes irritation leading to restlessness, pecking and in extreme cases anaemia and increased cannibalism. Due to an increase in the occurrence of acaricide-resistant D. gallinae populations, new control strategies are required and vaccination may offer a sustainable alternative to acaricides. In this study, recombinant forms of D. gallinae tropomyosin (Der g 10) and paramyosin (Der g 11) were produced, characterised and tested as vaccine candidate molecules. Methods: The D. gallinae paramyosin (Der g 11) coding sequence was characterised and recombinant versions of Der g 11 and D. gallinae tropomyosin (Der g 10) were produced. Hens were immunised with the recombinant proteins and the resulting antibodies were fed to D. gallinae and mite mortality evaluated. Sections of mites were probed with anti-Der g 11 and Der g 10 antibodies to identify the tissue distribution of these protein in D. gallinae. Results: The entire coding sequence of Der g 11 was 2,622 bp encoding 874 amino acid residues. Immunohistochemical staining of mite sections revealed that Der g 10 and Der g 11 were located throughout D. gallinae tissues. In phylogenetic analyses of these proteins both clustered with orthologues from tick species rather than with orthologues from astigmatid mites. Antibodies raised in hens against recombinant forms of these proteins significantly increased D. gallinae mortality, by 19 % for Der g 10 (P < 0.001) and by 23 % for Der g 11 (P = 0.009) when fed to the mites using an in vitro feeding device. Conclusions: This study has shown that Der g 10 and Der g 11 were located ubiquitously throughout D. gallinae and that antibodies raised against recombinant versions of these proteins can be used to significantly increase D. gallinae mortality in an in vitro feeding assay. When comparing archived data for all recombinant and native proteins assessed as vaccines using this in vitro feeding assay, Der g 10 and Der g 11 ranked highly and performed better than some of the pools of native proteins.