OAKTrust :: Browsing by Author "Snowden, Karen"

Browsing by Author "Snowden, Karen"

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Analysis of over 1500 triatomine vectors from across the US, predominantly Texas, for Trypanosoma cruzi infection and discrete typing units
(2017-12-22) Curtis-Robles, Rachel; Auckland, Lisa; Snowden, Karen; Hamer, Gabriel; Hamer, Sarah
Bioinformatic and Biochemical Characterization of Amblyomma americanum (Acari: Ixodidae) Serine Protease Inhibitors (Serpins)
(2016-05-06) Porter, Lindsay Michelle; Mulenga, Albert; Pietrantonio, Patricia; Snowden, Karen; Slotman, Michel; Teel, Pete
Ticks bites are a source of morbidity and mortality for humans and animals. Chemicals have been insufficient for tick control whereas an anti-tick vaccine may be an effective alternative. Hosts use serpins to control their immune pathways therefore ticks may inject serpins into the host for the same purpose. Amblyomma americanum transcriptome data were analyzed to determine extent and diversity of serpins. Candidate serpins were assayed for function against 17 proteses and for ability to affect blood coagulation and platelet aggregation. Spliced serpin constructs consisting of putatively immunogenic regions of selected serpins were designed for expression and vaccine trials. A. americanum expresses 122 unique serpins. The greatest diversity of serpins were in males and in feeding ticks. Forty percent were conserved in other ticks. A. americanum serpins 4 and 8 were selected for characterization as representatives of similar serpin clusters. These serpins bound host antibodies to tick saliva indicating they are immunogenic and used in feeding. Serpin 8 inhibited inflammatory proteases cathepsin G and proteinase 3. Serpin 4 inhibited inflammatory proteases cathepsin G and chymase, and the cysteine protease papain. Neither serpin affected blood coagulation however, serpin 4 delayed platelet aggregation. A spliced serpin construct was cloned in bacteria and yeast cells, however recombinant proteins failed to express. Results indicate serpins 4 and 8 function in the vertebrate host as counter-defense serpins and thus may be useful as anti-tick vaccine candidates, however their relative importance in tick feeding physiology will need to be addressed using an alternative protocol.
Biological and Biochemical Characterization of a Tick Feeding Stimuli Responsive Amblyomma americanum Acidic Chitinase in Tick Feeding Physiology
(2014-04-01) Kim, Tae Kwon; Mulenga, Albert; Pietrantonio, Patricia; Snowden, Karen
Without successful feeding, ticks can neither cause damage to their host nor transmit disease agents. Thus, a deeper understanding of tick physiology as a means to discover weaknesses that can be targeted for tick control is needed. In a previous study, 40 genes were discovered that are differentially up regulated in Amblyomma americanum (Aam) (Linnaeus) females when exposed to feeding stimuli. The purpose of this study was to biologically and biochemically characterize one of the 40 candidate genes, a putative acidic chitinase (Ach), to understand its role(s) and significance in regulating tick feeding physiology. This research has shown that A. americanum expresses two putative AamAch isoforms [long (L) and short (S)], both of which are classified into the glycosyl hydrolase 18 (GH-18) family. Members of the GH-18 are involved in regulating multiple functions including nutrition processes in bacteria, morphogenesis in yeast and fungi, pathogen attack in plants, molting in insects, and inflammation and tissue remodeling in mammals. Spatial and temporal mRNA transcript analyses show that putative AamAch-L and AamAch-S are ubiquitously expressed, with highest transcript abundance post-attachment observed at 72h in all tissues, and at 96h in the salivary gland. Pichia pastoris-expressed recombinant AamAch-L was glycosylated, consistent with molecular analysis that predicted N- and O-linked glycosylation sites. Substrate hydrolysis analysis indicated that rAamAch-L does not apparently have chitinase activity. RNAi mediated silencing of AamAch mRNA apparently caused loosening or weakening of the tick cement plug at the feeding site. Animals injected with AamAch-dsRNA bled around mouthparts, and were loosely attached on its rabbit host in that they easily detached with a light touch. The putative AamAch is therefore potentially involved in mediating tick attachment onto host skin. This thesis research advances our knowledge on the understanding of the molecular basis of tick feeding physiology and provides new information on the diverse physiological role of acidic chitinase-like proteins.
The Biological and Molecular Analysis of a Tick-Encoded Serine Protease Inhibitor (S6) and its Role in the Feeding Cycle of the Lone Star Tick, Amblyomma americanum (L) (Acari: ixodidae)
(2011-10-21) Chalaire, Katelyn Cox; Mulenga, Albert; Pietrantonio, Patricia V.; Snowden, Karen
Serine protease inhibitors (serpins) are a large superfamily of proteins that regulate critical proteolytic pathways by inhibiting serine proteases. Tick-encoded serpins are thought to play a vital role in the feeding process. To determine the relationship of Amblyomma americanum serpin 6 (S6) to tick feeding regulation, this study attempted to define the biological significance of this molecule through transcription and protein expression profiles, biochemical characterization of recombinant s6 (rS6), and the effects of in vivo post-transcriptional gene silencing on blood meal acquisition and fecundity. Transcriptional analysis revealed that S6 mRNA is ubiquitously expressed in unfed and partially fed ticks through the initial 5 days of the feeding period. S6 mRNA abundance in dissected tick organs showed a 3.7, 3.4, and 1.7- fold upregulation from 24 h to 96 h in the salivary gland (SG), midgut (MG) and the carcass (CA) remnant after removal of SG, MG respectively before downregulating at 120 h. Native S6 protein is downregulated in response to tick feeding, with correlation between transcription and protein expression profiles only consistent from the unfed to 48 h. Similarly, S6 protein expression in dissected female tick tissues is reduced as feeding progresses, with S6 being identified in SG, MG, ovary (OV), and CA from 24 h until 72 h. Biochemical characterization of S6 was not achieved, as rS6 did not form an irreversible complex when incubated with chymotrypsin or trypsin. Although complete silencing of S6 and S6/S17 mRNA was achieved, post-transcriptional gene knockdown had no effect on tick feeding efficiency or fecundity. These findings have been discussed in regards to the development of a vaccine against A. americanum and necessary future studies have been suggested for further characterization and assessment of biological significance.
Comparison of host-, herd-, and environmental-factors associated with serpositivity to neospora caninum among adult beef and dairy cattle in alberta
(2009-05-15) Dietz, Mark Colton; Scott, H. Morgan; Norby, Bo; Snowden, Karen
This study represents an analysis of serological and risk factor data collected previously in Alberta, Canada, involving neosporosis in beef and dairy cattle. The causative agent of neosporosis, Neospora caninum (NC), is a single-celled, apicomplexan protozoan parasite in which domesticated dogs have been identified as the definitive host. The primary economic impact involves beef and dairy cattle due to associated abortions and neonatal mortality. The data used in this study were collected for cattle in both dairy and beef herds in an identical manner permitting a direct comparison of host-, herd-, and environmental risk factors for neosporosis among beef and dairy cattle using descriptive statistical methods and the construction of multivariable models. The outcome assessed in the multivariable models was cow-level seropositivity for antibodies to N. caninum. Individual-level fixed, herd-level fixed, and random effects were evaluated with respect to the outcome. In the final multivariable models, there were few statistically significant potential risk factors identified. In the beef multivariable model, the significant explanatory factors were related to acreage of farm, site of calving, and pH of soil. Among the potential risk factors identified in the three multivariable models it appeared seropositivity to NC among beef cattle is more related to environmental conditions; on the other hand, it seems that seropositivity to NC in dairy cattle pertains to associated management factors. In the future, longitudinal studies are needed to explore the validity of the current knowledge regarding N. caninum by investigating potential risk factors that have been identified due to the fact that crosssectional studies can not prove association.
Cryptosporidium parvum: enhancing our understanding of its unique fatty acid metabolism and the elucidation of putative new inhibitors
(Texas A&M University, 2008-10-10) Fritzler, Jason Michael; Zhu, Guan; Derr, James; Snowden, Karen; Tian, Yanan
Cryptosporidium parvum is widely known for outbreaks within the immunocompetent population, as well its sometimes excruciating effects as an opportunistic agent in AIDS patients. Our understanding of the biology and host-parasite interactions of this parasitic protist is increasing at a rapid rate due to recent molecular and genetic advances. The topic of our research is in the area of C. parvum fatty acid metabolism, which is highly streamlined in this parasite. In addition to a type I fatty acid synthase (CpFAS1), C. parvum also possesses an enormous type I polyketide synthase (CpPKS1). Because of the size of this megasynthase, functional characterization of the complete enzyme is not possible. We have isolated and characterized the loading unit of CpPKS1 which contains an acyl-[acyl carrier protein (ACP)] ligase (AL) and an ACP. This unit is responsible for the overall substrate selection and initiation of polyketide production. Our data show that CpPKS1 prefers long-chain fatty acids with the highest specificity for arachidic acid (C20). Thus, the final polyketide product could contain as many as 34 carbons. Additionally, C. parvum possesses only a single fatty acid elongase. This family of enzymes serves a mechanism similar to FAS, and many have been found to be involved in de novo fatty acid synthesis in other organisms. After expressing this membrane protein in human cells, we have determined that it too prefers long-chain fatty acyl-CoAs which undergo only one round of elongation. This is in contrast to members of this enzyme family in other organisms that can initiate de novo synthesis from two- or four-carbon fatty acids via several rounds of elongation. Our lab has previously characterized the unique acyl-CoA binding protein (CpACBP1) from C. parvum. Molecular and biochemical data suggested that this enzyme may serve as a viable drug target. We have screened a library of known (and somewhat common) compounds against CpACBP1, and have isolated several potential compounds to be further examined for their ability to inhibit the growth of C. parvum.
Epidemiology and molecular typing of Trypanosoma cruzi in naturally-infected hound dogs and associated triatomine vectors in Texas, USA
(PLoS Neglected Tropical Diseases, 2017) Curtis-Robles, Rachel; Snowden, Karen; Dominguez, Brandon; Dinges, Lewis; Rodgers, Sandy; Mays, Glennon; Hamer, Sarah
Functional characterization of acyl-CoA binding protein (ACBP) and oxysterol binding protein-related proteins (ORPS) from Cryptosporidium parvum
(2009-05-15) Zeng, Bin; Zhu, guan; Derr, James; Snowden, Karen; Tian, Yanan
From opportunistic protist Cryptosporidium parvum we identified and functionally assayed a fatty acyl-CoA-binding protein (ACBP) gene. The CpACBP1 gene encodes a protein of 268 aa that is three times larger than typical ~10 KD ACBPs of humans and animals. Sequence analysis indicated that the CpACBP1 protein consists of an N-terminal ACBP domain (approximately 90 aa) and a C-terminal ankyrin repeat sequence (approximately 170 aa). The entire CpACBP1 open reading fragment (ORF) was engineered into a maltose-binding protein fusion system and expressed as a recombinant protein for functional analysis. Acyl-CoA-binding assays clearly revealed that the preferred binding substrate for CpACBP1 is palmitoyl-CoA. RT-PCR, Western blotting and immunolabelling analyses clearly showed that the CpACBP1 gene is mainly expressed during the intracellular developmental stages and that the level increases during parasite development. Immunofluorescence microscopy showed that CpACBP1 is associated with the parasitophorous vacuole membrane (PVM), which implies that this protein may be involved in lipid remodelling in the PVM, or in the transport of fatty acids across the membrane. We also identified two distinct oxysterol binding protein (OSBP)-related proteins (ORPs) from this parasite (CpORP1 and CpORP2). The short-type CpOPR1 contains only a ligand binding (LB) domain, while the long-type CpORP2 contains Pleckstrin homology (PH) and LB domains. Lipid-protein overlay assays using recombinant proteins revealed that CpORP1 and CpORP2 could specifically bind to phosphatidic acid (PA), various phosphatidylinositol phosphates (PIPs), and sulfatide, but not to other types of lipids with simple heads. Cholesterol was not a ligand for these two proteins. CpOPR1 was found mainly on the parasitophorous vacuole membrane (PVM), suggesting that CpORP1 is probably involved in the lipid transport across this unique membrane barrier between parasites and host intestinal lumen. Although Cryptosporidium has two ORPs, other apicomplexans, including Plasmodium, Toxoplasma, and Eimeria, possess only a single long-type ORP, suggesting that this family of proteins may play different roles among apicomplexans.
Heterobilharzia americana in Dogs: Characterizing Clinical Infection, Evaluating Diagnostic Test Performance, and Exploring Novel Methods of Diagnosis
(2017-07-31) Rodriguez, Jessica Yvonne; Snowden, Karen; Budke, Christine; Criscione, Charles; Lewis, Barbara
Heterobilharzia americana is a waterborne trematode parasite (Family: Schistosomatidae) of dogs. More complete information regarding clinical, geographic, and diagnostic aspects of this parasite is needed to aid in more effective awareness and diagnosis. A total of 238 cases diagnosed through the Texas A&M Veterinary Medical Diagnostic Laboratory, Texas A&M Veterinary Medical Teaching Hospital, Texas A&M Diagnostic Parasitology Service, and Texas A&M Gastrointestinal Laboratory were reviewed. Cases were distributed primarily in the eastern region of Texas. Clinical signs were diarrhea (67%), weight loss (38%), anorexia/hyporexia (27%), vomiting (22%), hematochezia (20%), lethargy (17%), and polyuria/polydipsia (6%). H. americana was attributed to death in 20 of 39 necropsy cases. Trematode eggs were identified histologically in the small intestine (84%), liver (84%), large intestine (39%), pancreas (35%), lung (9%), lymph node (8%), and spleen (4%). A total of 69 dogs were enrolled in a diagnostic methods comparison study. Relative test sensitivities were 50% (29.1-70.9) for fecal saline sedimentation, 58.3% (36.6-77.9) for PCR of fresh feces, and 95.8% (78.9-99.9) for PCR of fecal sediment. PCR of fresh feces was no more sensitive than fecal saline sedimentation. Circulating anodic antigen was detected in the serum of 8 dogs using the Schistosoma mansoni point-of-care assay (POC-CAA). Circulating cathodic antigen was detected in urine of 7 dogs using the POC-CCA test. Next generation sequencing technology and the Galaxy-based RepeatExplorer computation pipeline were used to discover highly repetitive DNA sequences in the H. americana genome. A novel probe-based real-time PCR diagnostic assay targeting these highly repetitive sequences was developed. No DNA amplification was detected when testing DNA of common parasites indicating that the assay is highly specific. The real-time assay detected 9 samples as positive that were negative by conventional PCR targeting a segment of the 18S ribosomal DNA. Increased awareness of H. americana by veterinarians is crucial for a timely diagnosis. Promising methods to increase test sensitivity include sample concentration before DNA extraction, and using highly repetitive DNA targets in a real-time PCR assay. Circulating antigens were detected in some dogs; however, more sensitive test modalities should be developed in order to make circulating antigens accurate diagnostic targets.
Immunolocalization and in vivo Functional Analysis by RNAi of the Aedes Kinin Receptor in Female Mosquitoes of Aedes aegypti (L.) (Diptera, Culicidae)
(2012-02-14) Kersch, Cymon; Pietrantonio, Patricia V.; Mulenga, Albert; Snowden, Karen
The evolution of the blood feeding adaptation has required precise coordination of multiple physiological processes in the insect, such as reproduction, behavior, digestion and diuresis. These processes are under careful synchronous hormonal control. For rapid excretion, multiple diuretic hormones are known. Although originally described based on their ability to stimulate hindgut contractions, the Aedes kinins have been shown to stimulate fluid secretion in female mosquitoes of Aedes aegypti. Aedes kinins are leucokinin-like neuropeptides released from neurosecretory cells in the brain and abdominal ganglia. They act by binding to the Aedes kinin receptor, a G proteincoupled receptor (GPCR). The Aedes kinin receptor has been cloned, sequenced, functionally characterized, and immunolocalized to stellate cells in the Malpighian tubules of Ae. aegypti. In addition to their myotropic and diuretic roles, leucokinin-like peptides and/or their receptors have been also been discovered in the nervous, digestive, and reproductive systems of other arthropod species. Therefore, the Aedes kinins have the potential to function in several simultaneous physiological processes that are stimulated by blood feeding. This thesis aims to understand better their role in the whole mosquito by investigating the Aedes kinin receptor's global expression as well as its in vivo contribution to post-prandial diuresis. Presence of the Aedes kinin receptor was investigated in the head, posterior midgut (stomach), hindgut, ovaries, and Malpighian tubules of both non blood-fed and blood-fed females by western blot using anti-receptor antibodies. The receptor was then immunolocalized in the posterior midgut and rectum. Finally, RNAi was employed to knock down kinin receptor expression, followed by measurement of in vivo urine excretion post blood feeding in a precision humidity chamber. Transcript and protein knockdown were confirmed by qPCR and immunohistochemistry, respectively. Results indicate widespread expression of the Aedes kinin receptor protein in organs novel for hematophagous insects and demonstrate the receptor's fundamental role in rapid diuresis. These findings strongly point to the Aedes kinins as integrative signaling molecules that could coordinate multiple physiological systems. The Aedes kinins could therefore have contributed to the success of the blood feeding adapation in mosquitoes.
Interaction of Gulf Coast tick, Amblyomma maculatum Koch, nymphs on cattle
(Texas A&M University, 2006-10-30) Wexler, Aaron; Teel, Pete D.; Longnecker, Michael; Olson, Jimmy; Snowden, Karen
Concern over the vector potential of the Gulf Coast tick, Amblyomma maculatum Koch, with the pathogen Ehrlichia ruminantium Dumler, causative agent of the disease heartwater, has increased the need for fundamental knowledge of tick ecology and behavior, specifically immature tick biology. Texas strain A. maculatum adult male ticks, known to emit attraction-aggregation-attachment pheromone (AAAP), were used to artificially simulate immature tick interaction with adults, in forced environments, on cattle. Artificial areas were grouped by treatment level, which were 1) aggregating, attached adult males, 2) aggregating attached adult females or 3) an empty area with no adults, as a control. Immature ticks were noted to be 6 times more likely to be aggregating in the AAAP treatment area when adult males were present. In the presences of either adult female ticks or no ticks at all, immature ticks were found to be attaching at random within the given area were they where permitted to feed. A second correlation of mortality was noted among immature ticks in the presence of AAAP emitting adult male ticks. In the permitted area where immature ticks could attach and feed, immature ticks were twice as likely to have survived to engorgement if adult male ticks were present in the area as well (53%). There was no difference in the survival rate among immature ticks if adult females were present or no adults at all, 26% and 21%, respectively. The study demonstrated that a significant attraction existed between immature ticks and attached adult males emitting AAAP.
Localization and partial immunological characterization of Fasciola hepatica Thioredoxin
(Texas A&M University, 2005-02-17) McKown, Richard Dwayne; Rice-Ficht, Allison; Craig, Thomas; Snowden, Karen; Teel, Pete
This study reports the localization and partial characterization of thioredoxin from the parasitic trematode Fasciola hepatica. Snails (Pseudosuccinia columella) were raised in culture and infected with F. hepatica so that Western blotting and immunohistochemical techniques could be utilized to determine the presence of thioredoxin in different stages of the parasite’s development. The results of these experiments showed that thioredoxin was present in the tegument, gut epithelium, excretory canal epithelium and sperm, of the adult parasite as well as in the tegument and gut of the redia and cercaria intermediate stages. In situ hybridization was used to determine the localization and possible differential mRNA expression of two different F. hepatica thioredoxin isotypes (Fh2020.A and Fh2020.SL) in the adult parasite. The in situ hybridization results showed that both isotypes are expressed in the tegument and gut epithelium. Fh2020.A stains with a greater intensity possibly demonstrating a difference in the amount of expression between the two isotypes. Recombinant F. hepatica thioredoxin expressed in bacteria using the pMAL™ Protein Fusion and Expression System was used to test its affects on the production of super oxide anion by murine peritoneal macrophages, bovine monocyte-derived macrophages and bovine whole blood neutrophils, and nitric oxide production by mouse peritoneal macrophages and bovine monocyte-derived macrophages. The results of the cellular assays were not definitive due to the fact that the maltose binding protein (MBP) moiety of the recombinant thioredoxin, when tested alone, increased production of nitric oxide by bovine monocyte-derived macrophages. Consequently, since the MBP could not be effectively separated from the thioredoxin portion of the recombinant, allowing the thioredoxin affects to be tested independently, no true conclusions regarding its affects on the host immune cells tested could be drawn. This is the first report of the localization of thioredoxin in both the adult F. hepatica as well as in specific intermediate stages of the parasite. These studies demonstrate the possible affects that a protein tag can have on experimental results and demonstrate how such data may be interpreted when a non-cleaved recombinant protein is used in cellular or other assays when compared to native or cleaved recombinant proteins.
Molecular Mechanisms Through Which Ticks Evade Host Defense
(2017-12-07) Bakshi, Mariam; Mulenga, Albert; Mwangi, Waithaka; Snowden, Karen; Pietrantonio, Patricia
Ticks seriously affect mammals and immunization of host is considered as sustainable option for their management. Identification and validation of protective molecules are major challenges in developing vaccines against ticks. Based on understanding tick saliva-host interaction, efforts have been dedicated to tick control to diminish their deleterious effects. By utilization of tick saliva proteins previously identified by cDNA phage display library, transcriptomic and immune-proteomic studies, current study focuses on investigation of roles of 15 selected Amblyomma americanum and Ixodes scapularis recombinant tick saliva proteins (rTSPs) on host macrophage function. The effect of rTSPs on macrophage secretion of pro- and anti-inflammatory cytokines (TNF-, IL-1, IL-6, IL-10, TGF-β) was investigated. Moreover, the functional role was examined by in vivo paw edema assay, cytokine and chemokine analysis. In vitro and in vivo investigations show that five Amblyomma americanum rTSPs, AamIGFBP (Insulin like growth factor binding proteins) rP-1, AamIGFBP-rP6 Short (S) and AamIGFBP-rP6 Long (L), Serine protease inhibitor (serpin) 8 (AAS8) and AamTCI (tick carboxypeptidase inhibitor), out of 15 are pro-inflammatory (PI) rTSPs as revealed by expression of pro-inflammatory costimulatory markers, cytokines, chemokines and signaling molecules. Interestingly, the two rTSPs serpins, AAS27 and AAS41, are anti-inflammatory (AI) rTSPs and appear to reverse the expression of costimulatory markers and cytokines induced by LPS and PI-rTSPs. Results indicate that PI- and AI-rTSPs function in host evasion and thus may serve as potential candidate for anti-tick vaccination.
Novel Intraosseous Device Performance and Longevity in a Goat Model (Capra hircus)
(2012-02-14) Jackson, Erin Elizabeth; Snowden, Karen; Gresham, Vincent; Mouneimne, Barhoumi
Two studies were performed to assess the function and longevity of a novel intraosseous (IO) catheter device. For the initial study, nine animals were assigned to three study groups. The first group received a 25 mm intraosseous device within the proximal humerus, the second group within the proximal tibia, and standard jugular catheters were placed in the final control group. Serial aerobic and anaerobic blood cultures were collected from jugular veins at day zero, then every third day while devices remained in use. Radiographs were obtained immediately after placement and again after removal of all IO devices. Goats were observed for overall clinical condition and lameness associated with catheter sites, and catheters were evaluated for patency and proper positioning. IO devices in the tibia remained in for less time than those in the humerus. Blood cultures in this study showed growth of Bacillus, Staphylococcus, and one colony within the genera Brachyacterium or novel Dermabacteraceae. Catheters also showed growth of Bacillus, as well as a single colony of Micromonospora chalcea. No animals in either IO group exhibited radiographic evidence of resulting damage or structural change within surrounding bone. In study two, eighteen goats were assigned to two study groups (25 mm intraosseous device within the wing of the ilium, or 45 mm catheter in the proximal humerus). Blood for serial aerobic and anaerobic blood cultures and CBC were collected from jugular veins at day zero, then every second day thereafter while devices remained in use. All clinical monitoring and removal criteria were identical to study one. Catheters in the ilium remained in significantly less time than those in the humerus. Several animals in the proximal humerus group demonstrated moderate lameness following removal. One goat developed an abscess near the insertion site and showed radiographic evidence of periosteal bone growth. Serial cultures showed growth of Bacillus, Streptococcus, Staphylococcus, and Enterococcus. Bloodwork indicated mild elevations of white blood cells from baseline in some cases. Our study indicated that catheters may remain safely in place for greater than 24 hours, but that animals should be closely monitored for negative side-effects for several days during the post-removal period.
Pathophysiology and transmission of Thelohania solenopsae in the red imported fire ants, Solenopsis invicta
(Texas A&M University, 2005-11-01) Chen, Johnny Shou-Chung; Vinson, S. B.; Cotes, Craig; Mitchell, Forrest; Sauer, Helmut; Snowden, Karen
Thelohania solenopsae are intracellular pathogens found in the red imported fire ant, Solenopsis invicta. These pathogens cause detrimental effects to their fire ant hosts. The present study revealed that the midgut and the meconium materials from pupating fourth instar larvae were possible vehicles for the horizontal transmission of the disease. The pathogen was further found to cause a reduction of humeral proteins. In SDS-PAGE stained with silver, several proteins were observed only in controls but not in infected fire ant queens. Different queens were found to have variable proteins reduced due to infection of this pathogen. Furthermore, vitellogenin titers were found to be significantly reduced in infected fire ant queens, although the infection rates of the fat body cells was found to be less than 20%. Finally, although the pathogens did not directly induce apoptosis in infected cells, there were more infected cells undergoing apoptosis than uninfected cells. There was no evidence to support the idea that infected fat body cells became more resistant to apoptosis inducers.
Understanding the Complexity of Ixodes Scapularis and Amblyomma Americanum Tick Feeding Through Proteomics for a Multi-Antigen Vaccine Design
(2019-06-13) Kim, Tae Kwon; Mulenga, Albert; Adams, Leslie G; Snowden, Karen; Mwangi, Waithaka; Skare, Jon
Tick saliva proteins facilitate feeding success and transmission of tick-borne disease agents by ticks, and thus, they might serve as effective antigens for a tick vaccine. This dissertation for the first-time identifies saliva proteins that are secreted every 24 h during tick-feeding of two distantly-related and most medically important ticks species in the United States, Ixodes scapularis and Amblyomma americanum. Data in this dissertation reveal that tick feeding is a complex system that is dynamically changing in response to the host defenses. Understanding biological functional roles of tick saliva proteins is critical to developing novel methods to prevent tick-borne disease infections. Therefore, the second part of this dissertation defines the functional roles of three serine protease inhibitors (serpins: AAS19, AAS41 and AAS46), which are thought to control serine proteases that mediate host defense mechanisms. While these serpins are secreted into the host during feeding and are immunogenic, only AAS19 and AAS41 were functionally active, having anti-hemostatic or anti-inflammatory properties, respectively. The finding that despite being 97% identical to AAS41, AAS46 is apparently not an efficient inhibitor provides insights into how the tick might evade host defenses: it is possible that ticks secrete AAS46 as an immune decoy to protect the functional AAS41 from immune attack. Finally, information generated from this dissertation was utilized to formulate a cocktail anti-tick vaccine that included 13 recombinant tick saliva proteins. Although these antigens elicited an immune response in immunized cattle, they did not protect cattle against primary tick infestations; however, immunization enhanced the naturally acquired immunity against tick feeding that is elicited by repeated infestation. This dissertation contributes to a better understanding of the molecular basis of tick-feeding physiology, which is the needed first step before novel tick control methods can be developed. Results from this dissertation have contributed to our understanding of the molecular basis of tick feeding physiology and will serve as foundation to formulate an effective tick-antigen based vaccine to prevent tick-borne disease transmission.

Browsing by Author "Snowden, Karen"

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