The American dog tick, Dermacentor variabilis, encodes a functional histamine release factor homolog

Insect Biochem Mol Biol. 2003 Sep;33(9):911-9. doi: 10.1016/s0965-1748(03)00097-3.


We have identified a functional Dermacentor variabilis histamine release factor (DVHRF) homolog and shown that it is a secreted tick saliva protein. The 945 base pair (bp) full-length DVHRF cDNA has a 522 bp open reading frame that encodes a 20 kDa (173 amino acid) polypeptide. Sequence analysis showed that the two HRF signature amino acid sequences were conserved in DVHRF, indicating close structural similarity between DVHRF and other characterized HRF homologs. Northern and Western blotting analyses of partially fed and unfed ticks indicates that neither DVHRF transcriptional nor translational regulation were influenced by tick feeding activity. Like its counterparts from the mammalian system, tick DVHRF is expressed in various tissues, as assessed by both Northern and Western blotting analyses. Furthermore, an Escherichia coli-expressed recombinant DVHRF induced histamine secretion from a rat basophilic leukemic cell line in a dose-dependent manner. Extensive experimental evidence has shown that high levels of histamine at tick attachment sites impede the biological success of feeding ticks and, in response, ticks secrete histamine-binding proteins to minimize the adverse effects of histamine. Our results suggest the existence of a tick-derived multifaceted control mechanism for levels of histamine at tick feeding sites.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Biomarkers, Tumor / genetics*
  • Biomarkers, Tumor / metabolism
  • Biomarkers, Tumor / pharmacology
  • Cell Line
  • Cloning, Molecular
  • DNA, Complementary / genetics
  • Dermacentor / chemistry
  • Dermacentor / genetics*
  • Dermacentor / metabolism
  • Dogs / parasitology
  • Feeding Behavior
  • Female
  • Histamine / metabolism
  • Histamine / pharmacology
  • Histamine Release / drug effects
  • Histamine Release / physiology*
  • Mast Cells / drug effects
  • Mast Cells / metabolism
  • Molecular Sequence Data
  • Rabbits
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Recombinant Proteins / pharmacology
  • Saliva / chemistry
  • Sequence Homology, Amino Acid
  • Thioredoxins / metabolism


  • Biomarkers, Tumor
  • DNA, Complementary
  • Recombinant Proteins
  • tumor protein, translationally-controlled 1
  • Thioredoxins
  • Histamine