Download Opportunities with USDA-ARS Locations in South Central Texas Kevin Temeyer

Opportunities with USDA-ARS
Locations in South Central Texas
Kevin Temeyer
Knipling-Bushland U.S. Livestock Insects
Research Laboratory, Kerrville, TX 78028
USDA-ARS Locations in Texas
Kerrville (Moore Field & Panama), Temple, College Station, Bushland, Lubbock
Pathogenic Landscape
River willows
Arundo
donax
Infested hosts
Cattle
Cattle fever tick
Deer
1. Arundo and Guineagrass enhance survival of tick
2. Transition back to native vegetation--better biological barrier to ticks
Racelis, A.E., R. B. Davey, J. A. Goolsby, A. A. Pérez de León,
K. Varner, and R. Duhaime. 2012. Facilitative ecological interactions
between invasive species: Arundo donax (Poaceae) stands as
favorable habitat for cattle ticks (Acari: Ixodidae) along the USMexico border. Journal of Medical Entomology 49: 410-417.
Nilgai
Deployed Warfighter Protection Program
Joint program between Dept. of Defense and Dept. of Agriculture
Agricultural
Research
Service
Identical residues
Sand fly AChE
Non-identical residues
Target of organophosphate insecticides
Unaligned residues
Catalytic triad:
Ser336, Glu462, His576
of P. papatasi sequence
• Constructed rPpAChE1G119S by targeted
mutagenesis containing
Gly→Ser OP-R substitution
(G256S) for biochemical
characterization
Alignment of PpAChE sequence to Drosophila melanogaster AChE (MMDB 1QO9)
Partial PpAChE1 cDNA sequence containing G119S codon identified as OP-R
in An. gambiae and other insects
Ser OP-insensitive
TGGATCTTCGGTGGTAGCTTCTACTCAGGAACATCCAC
TGGATCTTCGGTGGTGGCTTCTACTCAGGAACATCCAC
Gly
OP-sensitive
rPpAChE1 containing G119S codon
OP-R in An. gambiae and other insects
Ser OP-insensitive
ATCTTCGGTGGTAGCTTCTACTCAGGAACATCC
ATCTTCGGTGGTGGCTTCTACTCAGGAACATCC
Gly OP-sensitive (wt)
Biochemical properties of rPpAChE1
Propertya
rPpAChE1
(OP-sensitive)
rPpAChE1-G256S
(OP-insensitive)
Km AcSChb (μM)
24
98 (4-fold)
IC50 Paraoxon (10-7 M)
2.9
3800 (1300-fold)
IC50 Malaoxon (10-8 M)
4.4
2000 (455-fold)
IC50 Eserine (10-9 M)
4.8
120 (25-fold)
Continuing need for new pest control technologies
Genomics
Pest physiology
Vaccines
New, targeted pesticides
Strategies for control of pest populations
Strategies to prevent pathogen transmission by vectors
Host animal resistance to parasites & disease
Tick AChE Phylogram
Ixodes scapularis predicted AChEs
R. microplus BmAChEs
Acetylcholinesterase - Target Site Insensitivity in R. microplus
 Three AChEs expresses in synganglion:
 BmAChE1, Km ≈ 4-5 μM
 BmAChE2, Km ≈ 40-50 μM
 BmAChE3, Km ≈ 90-100 μM
 BmAChE1, BmAChE2 & BmAChE3 are functional complements
 BmAChE1, BmAChE2 & BmAChE3 are amplified, expressing
more than two transcript alleles
 Multiple amino acid substitutions were associated with resistance
for each of the three BmAChEs
 Individual ticks maintained & expressed multiple alleles for each of
the three BmAChEs
 Acetylcholinesterase target site insensitivity is multigenic in R.
microplus
 Current studies – probable
additional BmAChEs
•
•
•
Fsg186 (salivary)
Tc19987 (gut)
possible vaccine candidates?
•
Noteworthy opportunity to
investigate host-parasite interaction
(nervous/immune integration)
•
External collaborations with Univ.
Florida, Virginia Tech., Southwest
Research Institute (San Antonio),
Mayo Clinic, Iowa State University
Ixodes scapularis
AChE phylogram
R. microplus AChEs:
BmAChE2
BmAChE3
BmAChE1
Proposed Role of Tick Salivary AChE
Tick Salivary AChE:
Tick Gut AChE:
 Detoxifies
Bloodmeal
Host factors
 Hydrolyzes
acetylcholine in host
tissues
 Alters acetylcholine
activation of nicotinic
and muscarinic
receptors
Parasite
factors
Pathogen
factors
 Modulates host
inflammatory response
 Modulates host innate
immunity
 Modulates host
acquired immunity
Acetylcholinesterase: The Target of
Organophosphates
• AChE function
 Key synaptic enzyme in CNS
 Hydrolyzes neurotransmitter AcCh
 Regulation of Inflammation &
Immune Response via local
acetylcholine
 Detoxification of bloodmeal
• OPs bind to and inhibit AChE
 Blocking nerve impulse
transmission
 Desensitizes AcCh receptors
• Mutations in AChE may lead to
OP resistance
Thank you for your attention!