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Reverse vaccinology approach for the identification of novel Rhipicephalus (boophilus) microplus vaccine candidates

Lew-Tabor, A., Jackson, L., Rodriguez-Valle, M., Piper, E., Kurscheid, S., Moolhuijzen, P., Constantinoiu, C., Jones, M., Gondro, C., Bruyeres, A., Jarrett, S., Minchin, C., Venus, B., Zhang, B., Bellgard, M., Guerrero, F. and Jonsson, N. (2008) Reverse vaccinology approach for the identification of novel Rhipicephalus (boophilus) microplus vaccine candidates. In: VIth International Conference on Ticks and Tick-Borne Pathogens, 21 - 26 September 2008, Buenos Aires, Argentina


Ticks and tick borne diseases cost Australian cattle enterprises $US170m per annum with global losses estimated at $US2.5bn. Rising acaricide resistance and market failure of TickGARD PLUS (Bm86) vaccine in Australia has led to an investment to identify new vaccine candidates with longer lasting immunity. Capitalizing on 13,643 available R. microplus ESTs (BmiGeneIndex2), Ixodes scapularis draft tick genome contigs and gene discovery tools such as suppressive subtractive hybridization, R. microplus microarrays (NimbleGen), proteomics and bioinformatics, we are applying a reverse vaccinology approach to identify putative R. microplus vaccine candidates. In parallel, we have undertaken comprehensive analyses of host responses pre- and post- R.microplus infestation by measuring peripheral cellular and antibody responses, skin histology and immunohistochemistry, and bovine microarray (Affymetrix) analysis of skin and blood from rsistant (Brahman and Santa-Gertrudis) and susceptible (Holstein-Fricsian and Santa-Gertrudis) cattle. Our trials demonstrated that the resistant host mounts a Th1 protective response to ticks whereas the immune response of susceptible cattle appears to become 'confused' as cattle respond vigorously to a wide variety of tick extracts. We have developed novel in vitro screening tools (utilizing cells and sera from the above trials) for pre-in vivo high-throughput screening of expressed candidates. Bioinformatics and gene discovery studies identified 250 vaccine candidates including lipocalins, lipoprotein receptors, proteases/metalloproteases, extracellular matrix proteins, membrane proteins, cuticle enzymes, chitin binding and ~170 proteins of unknown function mostly specific to tick species. These candidates are under further scrutiny using criteria such as hydropathy/epitope prediction, relative abundance of similar epitopes in other tick species and host proteins, abundance in multiple tick stages, in vitro functional analyses and immune recognition (proteomics) to select a total of 50 genes for expression for in vitro screening prior to selection for in vivo 'proof of concept' trials.

Publication Type: Conference Paper
Murdoch Affiliation: Centre for Comparative Genomics
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