Target validation of a myokinin receptor from the southern cattle tick Boophilus microplus (Canestrini)
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A novel approach to control Boophilus microplus is to disrupt the physiological function of an endogenous myokinin receptor of this tick that was previously cloned in our laboratory. To test the hypothesis that this myokinin receptor might be a suitable target for development of a novel acaricide, this target was validated by immunological disruption. A mixture of peptides, corresponding to the sequence of the extracellular loops of this receptor which were synthesized and linked to a carrier protein, was injected into Hereford cattle to induce an immunological response. Immunological tests (ELISA) were developed to test the sera of these animals for antibody titers. The data were analyzed using a randomized block split plot design and were compared between the control (calves numbers 407, 408, 427, 436, and 438) and peptide-injected calves (calves numbers 417, 420, 421, 426, and 435). A gradual increase of antibody production was observed with the peptide-injected calves with bleed 4 showing the highest absorbances. Control calves and peptide-injected calves with high antibody titers were challenged with approximately 20,000 tick larvae at the USDA Cattle Tick Research laboratory. The tick challenge test determined that disruption of the receptor function produces a detrimental effect on tick physiology (development, feeding and reproduction) by looking at percentage of molting, time of survivorship, number of ticks dropped, weight of fed females, weight of egg masses, and blood meal conversion. The results, which were analyzed by a contingency table and a 2 sample T-test, did not support the hypothesis that the sera ingested from the peptide-injected cattle would cause a detrimental effect on tick physiology. There was no statistical significance in the percentage of metanymphs molting from peptide-injected calves versus control calves (p = 0.282) and in the time of adult survivorship. A statistical inference could be made about the number of ticks that dropped since four calves died of bovine babesiosis after the metanymphal collection. There was no statistical significance in the weight of fed females (p = 0.061), weight of egg masses (p = 0.885), and bloodmeal conversion (p = 0.312) from peptide-injected calves versus control calves.
Blandon, Maria Adylia (2003). Target validation of a myokinin receptor from the southern cattle tick Boophilus microplus (Canestrini). Master's thesis, Texas A&M University. Texas A&M University. Available electronically from