Abstract
Vaccination as a control method against the cattle tick, Rhipicephalus (Boophilus) microplus has been practiced since the introduction of two products in the mid-1990s. There is a need for a vaccine that could provide effective control of R. microplus in a more consistent fashion than existing products. During our transcriptome studies of R. microplus, several gene coding regions were discovered to encode proteins with significant amino acid similarity to aquaporins. A cDNA encoding an aquaporin from the cattle tick, Rhipicephalus microplus, was isolated from transcriptomic studies conducted on gut tissues dissected from fully engorged adult female R. microplus. Bioinformatic analysis indicates this aquaporin, designated RmAQP1, shows greatest amino acid similarity to the human aquaporin 7 family. Members of this family of water-conducting channels can also facilitate the transport of glycerol in addition to water. The efficacy of this aquaporin as an antigen against the cattle tick was explored in cattle vaccine trials conducted in Brazil. A cDNA encoding a significant portion of RmAQP1 was expressed as a recombinant protein in Pichia pastoris, purified under native conditions using a polyhistidine C-terminus tag and nickel affinity chromatography, emulsified with Montanide adjuvant, and cattle vaccinated intramuscularly. The recombinant protein provided 75% and 68% efficacy in two cattle pen trials conducted in Campo Grande, Brazil on groups of 6 one year old Holstein calves. The effectiveness of this vaccine in reducing the numbers of adult female ticks shows this aquaporin antigen holds promise as an active ingredient in cattle vaccines targeted against infestations of R. microplus.
Highlights
Vaccination as a control method against the cattle tick, Rhipicephalus (Boophilus) microplus has been practiced since the introduction of two products in the mid-1990s
Tissues that were the source of RNA for gene expression study were dissected from 25 1–2 day old adult male and female ticks from the R. microplus Deutch strain f41 generation maintained at the Cattle Fever Tick Research Laboratory
Aquaporin-like sequences from the cattle tick Using ESTs from BmiGI Ver 2.0 as a starting point [11], we used 5′ RACE to isolate an 1,800 bp transcript that included the entire open reading frame (ORF) to an aquaporin-like protein (Figure 1; GenBank Accession No KJ626366)
Summary
Vaccination as a control method against the cattle tick, Rhipicephalus (Boophilus) microplus has been practiced since the introduction of two products in the mid-1990s. The cattle tick, Rhipicephalus (Boophilus) microplus, is an obligate parasitic cattle pest that has established populations throughout the world’s tropical and subtropical regions. Acaricide resistant populations of R. microplus have become a major problem in most of the cattleproducing countries of the world and novel cattle tick control technologies are needed to maintain efficiencies in cattle production [2,3,4]. Vaccination as a tick control method has been practiced since the introduction of two products in the mid-1990s, TickGARD [5] and Gavac© [6], that were developed using the midgut glycoprotein Bm86 as the immunoreactive antigen. TickGARD is no longer commercially available, but Gavac© continues to be used to date, primarily in
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