pncA and bptA are not sufficient to complement Ixodes scapularis colonization and persistence by Borrelia burgdorferi in a linear plasmid lp25-deficient background.

The complex segmented genome of Borrelia burgdorferi is comprised of a linear chromosome along with numerous linear and circular plasmids essential for tick and/or mammalian infectivity. The pathogenic necessity for specific borrelial plasmids has been identified; most notably, infections of the tick vector and mammalian host both require linear plasmid 25 (lp25). Genes carried on lp25, specifically bptA and pncA, are postulated to play a role for B. burgdorferi to infect and persist in Ixodes ticks. In this study, we complemented an lp25-deficient borrelial strain with pncA alone or pncA accompanied by bptA to evaluate the ability of the complemented strains to restore larval colonization and persistence through transstadial transmission relative to that of wild-type B. burgdorferi. The acquisition of the complemented strains by tick larvae from infected mice and/or the survival of these strains was significantly decreased when assayed by cultivation and quantitative PCR (qPCR). Only 10% of the pncA-complemented strain organisms were found by culture to survive 17 days following larval feeding, while 45% of the pncA- and bptA-complemented strain organisms survived, with similar results by PCR. However, neither of the complemented B. burgdorferi strains was capable of persisting through the molt to the nymphal stage as analyzed by culture. qPCR analyses of unfed nymphs detected B. burgdorferi genomes in several nymphs at low copy numbers, likely indicating the presence of DNA from dead or dying cells. Overall, the data indicate that pncA and bptA cannot independently support infection, suggesting that lp25 carries additional gene(s) or regulatory elements critical for B. burgdorferi survival and pathogenesis in the Ixodes vector.

Borrelia miyamotoi BipA-like protein, BipM, is a candidate serodiagnostic antigen distinguishing between Lyme disease and relapsing fever Borrelia infections.

A Borrelia miyamotoi gene with partial homology to bipA of relapsing fever spirochetes Borrelia hermsii and Borrelia turicatae was identified by a GenBank basic alignment search analysis. We hypothesized that this gene product may be an immunogenic antigen as described for other relapsing fever Borrelia (RFB) and could serve as a serological marker for B. miyamotoi infections. The B. miyamotoi gene was a truncated version about half the size of the B. hermsii and B. turicatae bipA with a coding sequence of 894 base pairs. The gene product had a calculated molecular size of 32.7 kDa (including the signal peptide). Amino acid alignments with B. hermsii and B. turicatae BipA proteins and with other B. miyamotoi isolates showed conservation at the carboxyl end. We cloned the B. miyamotoi bipA-like gene (herein named bipM) and generated recombinant protein for serological characterization and for antiserum production. Protease protection analysis demonstrated that BipM was surface exposed. Serologic analyses using anti-B. miyamotoi serum samples from tick bite-infected and needle inoculated mice showed 94 % positivity against BipM. The 4 BipM negative serum samples were blotted against another B. miyamotoi antigen, BmaA, and two of them were seropositive resulting in 97 % positivity with both antigens. Serum samples from B. burgdorferi sensu stricto (s.s.)-infected mice were non-reactive against rBipM by immunoblot. Serum samples from Lyme disease patients were also serologically negative against BipM except for 1 sample which may have indicated a possible co-infection. A recently published study demonstrated that B. miyamotoi BipM was non-reactive against serum samples from B. hermsii, Borrelia parkeri, and B. turicatae infected animals. These results show that BipM has potential for a B. miyamotoi-infection specific and sensitive serodiagnostic to differentiate between Lyme disease and various RFB infections.

Borrelia burgdorferi bba66 gene inactivation results in attenuated mouse infection by tick transmission.

The impact of the Borrelia burgdorferi surface-localized immunogenic lipoprotein BBA66 on vector and host infection was evaluated by inactivating the encoding gene, bba66, and characterizing the mutant phenotype throughout the natural mouse-tick-mouse cycle. The BBA66-deficient mutant isolate, Bb(ΔA66), remained infectious in mice by needle inoculation of cultured organisms, but differences in spirochete burden and pathology in the tibiotarsal joint were observed relative to the parental wild-type (WT) strain. Ixodes scapularis larvae successfully acquired Bb(ΔA66) following feeding on infected mice, and the organisms persisted in these ticks through the molt to nymphs. A series of tick transmission experiments (n = 7) demonstrated that the ability of Bb(ΔA66)-infected nymphs to infect laboratory mice was significantly impaired compared to that of mice fed upon by WT-infected ticks. trans-complementation of Bb(ΔA66) with an intact copy of bba66 restored the WT infectious phenotype in mice via tick transmission. These results suggest a role for BBA66 in facilitating B. burgdorferi dissemination and transmission from the tick vector to the mammalian host as part of the disease process for Lyme borreliosis.

Evaluation of Immunocompetent Mouse Models for Borrelia miyamotoi Infection.

Borrelia miyamotoi is a relapsing fever spirochete that is harbored by Ixodes spp. ticks and is virtually uncharacterized, compared to other relapsing fever Borrelia vectored by Ornithodoros spp. ticks. There is not an immunocompetent mouse model for studying B. miyamotoi infection in vivo or for transmission in the vector-host cycle. Our goal was to evaluate B. miyamotoi infections in multiple mouse breeds/strains as a prelude to the ascertainment of the best experimental infection model. Two B. miyamotoi strains, namely, LB-2001 and CT13-2396, as well as three mouse models, namely, CD-1, C3H/HeJ, and BALB/c, were evaluated. We were unable to observe B. miyamotoi LB-2001 spirochetes in the blood via darkfield microscopy or to detect DNA via real-time PCR post needle inoculation in the CD-1 and C3H/HeJ mice. However, LB-2001 DNA was detected via real-time PCR in the blood of the BALB/c mice after needle inoculation, although spirochetes were not observed via microscopy. CD-1, C3H/HeJ, and BALB/c mice generated an antibody response to B. miyamotoi LB-2001 following needle inoculation, but established infections were not detected, and the I. scapularis larvae failed to acquire spirochetes from the exposed CD-1 mice. In contrast, B. miyamotoi CT13-2396 was visualized in the blood of the CD-1 and C3H/HeJ mice via darkfield microscopy and detected by real-time PCR post needle inoculation. Both mouse strains seroconverted. However, no established infection was detected in the mouse organs, and the I. scapularis larvae failed to acquire Borrelia after feeding on CT13-2396 exposed CD-1 or C3H/HeJ mice. These findings underscore the challenges in establishing an experimental B. miyamotoi infection model in immunocompetent laboratory mice. IMPORTANCE Borrelia miyamotoi is a causative agent of hard tick relapsing fever, was first identified in the early 1990s, and was characterized as a human pathogen in 2011. Unlike other relapsing fever Borrelia species, B. miyamotoi spread by means of Ixodes ticks. The relatively recent recognition of this human pathogen means that B. miyamotoi is virtually uncharacterized, compared to other Borrelia species. Currently there is no standard mouse-tick model with which to study the interactions of the pathogen within its vector and hosts. We evaluated two B. miyamotoi isolates and three immunocompetent mouse models to identify an appropriate model with which to study tick-host-pathogen interactions. With the increased prevalence of human exposure to Ixodes ticks, having an appropriate model with which to study B. miyamotoi will be critical for the future development of diagnostics and intervention strategies.

Analysis of variable major protein antigenic variation in the relapsing fever spirochete, Borrelia miyamotoi, in response to polyclonal antibody selection pressure.

Borrelia miyamotoi is a tick-transmitted spirochete that is genetically grouped with relapsing fever Borrelia and possesses multiple archived pseudogenes that encode variable major proteins (Vmps). Vmps are divided into two groups based on molecular size; variable large proteins (Vlps) and variable small proteins (Vsps). Relapsing fever Borrelia undergo Vmp gene conversion at a single expression locus to generate new serotypes by antigenic switching which is the basis for immune evasion that causes relapsing fever in patients. This study focused on B. miyamotoi vmp expression when spirochetes were subjected to antibody killing selection pressure. We incubated a low passage parent strain with mouse anti-B. miyamotoi polyclonal antiserum which killed the majority population, however, antibody-resistant reisolates were recovered. PCR analysis of the gene expression locus in the reisolates showed vsp1 was replaced by Vlp-encoded genes. Gel electrophoresis protein profiles and immunoblots of the reisolates revealed additional Vlps indicating that new serotype populations were selected by antibody pressure. Sequencing of amplicons from the expression locus of the reisolates confirmed the presence of a predominant majority serotype population with minority variants. These findings confirm previous work demonstrating gene conversion in B. miyamotoi and that multiple serotype populations expressing different vmps arise when subjected to antibody selection. The findings also provide evidence for spontaneous serotype variation emerging from culture growth in the absence of antibody pressure. Validation and determination of the type, number, and frequency of serotype variants that arise during animal infections await further investigations.

A serological assay to detect and differentiate rodent exposure to soft tick and hard tick relapsing fever infections in the United States.

Human cases of relapsing fever (RF) in North America are caused primarily by Borrelia hermsii and Borrelia turicatae, which are spread by argasid (soft) ticks, and by Borrelia miyamotoi, which is transmitted by ixodid (hard) ticks. In some regions of the United States, the ranges of the hard and soft tick RF species are known to overlap; in many areas, recorded ranges of RF spirochetes overlap with Lyme disease (LD) group Borrelia spirochetes. Identification of RF clusters or cases detected in unusual geographic localities might prompt public health agencies to investigate environmental exposures, enabling prevention of additional cases through locally targeted mitigation. However, exposure risks and mitigation strategies differ among hard and soft tick RF, prompting a need for additional diagnostic strategies that differentiate hard tick from soft tick RF. We evaluated the ability of new and previously described recombinant antigens in serological assays to differentiate among prior exposures in mice to LD, soft or hard tick RF spirochetes. We extracted whole-cell protein lysates from RF Borrelia cultures and synthesized six recombinant RF antigens (Borrelia immunogenic protein A (BipA) derived from four species of RF Borrelia, glycerophosphodiester phosphodiesterase (GlpQ), and Borrelia miyamotoi membrane antigen A (BmaA)) to detect reactivity in laboratory derived (Peromyscus sp. and Mus sp.) mouse serum infected with RF and LD Borrelia species. Among 44 Borrelia exposed mouse samples tested, all five mice exposed to LD spirochetes were correctly differentiated from the 39 mice exposed to RF Borrelia using the recombinant targets. Of the 39 mice exposed to RF spirochetes, 28 were accurately categorized to species of exposure (71%). Segregation among soft tick RF species (Borrelia hermsii, Borrelia parkeri and Borrelia turicatae) was inadequate (58%) owing to observed cross-reactivity among recombinant BipA protein targets. However, among the 28 samples accurately separated to species, all were accurately assigned to soft tick or hard tick RF type. Although not adequately specific to accurately categorize exposure to soft tick RF species, the recombinant BipA protein targets from soft and hard tick RF species show utility in accurately discriminating mouse exposures to LD or RF Borrelia, and accurately segregate hard tick from soft tick RF Borrelia exposure.

Modification of the multiplex plasmid PCR assay for Borrelia miyamotoi strain LB-2001 based on the complete genome sequence reflecting genomic rearrangements differing from strain CT13-2396.

The genome of Borrelia spp. consists of an approximate 1 megabase chromosome and multiple linear and circular plasmids. We previously described a multiplex PCR assay to detect plasmids in the North American Borrelia miyamotoi strains LB-2001 and CT13-2396. The primer pair sets specific for each plasmid were derived from the genome sequence for B. miyamotoi strain CT13-2396, because the LB-2001 complete sequence had not been generated. The recent completion of the LB-2001 genome sequence revealed a distinct number of plasmids (n = 12) that differed from CT13-2396 (n = 14). Notable was a 97-kilobase plasmid in LB-2001, not present in CT13-2396, that appeared to be a rearrangement of the circular plasmids of strain CT13-2396. Strain LB-2001 contained two plasmids, cp30-2 and cp24, that were not annotated for strain CT13-2396. Therefore, we re-evaluated the original CT13-2396-derived multiplex PCR primer pairs and determined their location in the LB-2001 plasmids. We modified the original multiplex plasmid PCR assay for strain LB-2001 to include cp30-2 and cp24. We also determined which LB-2001 plasmids corresponded to the amplicons generated from the original CT13-2396 primer sets. These observations provide a more precise plasmid profile based on the multiplex PCR assay and reflect the complexity of gene rearrangements that occur in B. miyamotoi strains isolated from the same geographic region.

A transwell assay method to evaluate Borrelia burgdorferi sensu stricto migratory chemoattraction toward tick saliva proteins.

We developed a transwell assay to quantify migration of the Lyme disease agent, Borrelia burgdorferi sensu stricto (s.s.), toward Ixodes scapularis salivary gland proteins. The assay was designed to assess B. burgdorferi s.s. migration upward against gravity through a transwell polycarbonate membrane overlaid with 6% gelatin. Borreliae that channeled into the upper transwell chamber in response to test proteins were enumerated by flow cytometry. The transwell assay measured chemoattractant activity for B. burgdorferi s.s. from salivary gland extract (SGE) harvested from nymphal ticks during bloodmeal engorgement on mice 42 h post-attachment and saliva collected from adult ticks. Additionally, SGE protein fractions separated by size exclusion chromatography demonstrated various levels of chemoattractant activity in the transwell assay. Sialostatin L, and Salp-like proteins 9 and 11 were identified by mass spectrometry in SGE fractions that exhibited elevated activity. Recombinant forms of these proteins were tested in the transwell assay and showed positive chemoattractant properties compared to controls and another tick protein, S15A. These results were reproducible providing evidence that the transwell assay is a useful method for continuing investigations to find tick saliva components instrumental in driving B. burgdorferi s.s. chemotaxis.

Borrelia miyamotoi strain LB-2001 retains plasmids and infectious phenotype throughout continuous culture passages as evaluated by multiplex PCR.

Borrelia miyamotoi is a tick-borne spirochete of the relapsing fever borrelia group and an emerging pathogen of public health significance. The genomes of relapsing fever borreliae and Lyme disease borreliae consist of multiple linear and circular plasmids in addition to the chromosome. Previous work with B. burgdorferi sensu lato found diminished infectivity upon continuous in vitro culture passage that was attributable to plasmid loss. The effect of long-term culture passage on B. miyamotoi is not known. We generated a series of plasmid-specific primer sets and developed a multiplex PCR assay to detect the 14 known plasmids of B. miyamotoi North American strains LB-2001 and CT13-2396. We assessed the plasmid content of B. miyamotoi LB-2001 over 64 culture passages spanning 15 months and determined that strain LB-2001 retained all plasmids upon prolonged in vitro cultivation and remained infectious in mice. We also found that strain LB-2001 lacks plasmid lp20-1 which is present in strain CT13-2396. These results suggest that B. miyamotoi remains genetically stable when cultured and passaged in vitro.

Characterization of a Borrelia miyamotoi membrane antigen (BmaA) for serodiagnosis of Borrelia miyamotoi disease.

Borrelia miyamotoi is a tick-borne pathogen that causes Borrelia miyamotoi disease (BMD), an emerging infectious disease of increasing public health significance. B. miyamotoi is transmitted by the same tick vector (Ixodes spp.) as B. burgdorferi sensu lato (s.l.), the causative agent of Lyme disease, therefore laboratory assays to differentiate BMD from Lyme disease are needed to avoid misdiagnoses and for disease confirmation. We previously performed a global immunoproteomic analysis of the murine host antibody response against B. miyamotoi infection to discover antigens that could serologically distinguish the two infections. An initial assessment identified a putative lipoprotein antigen, here termed BmaA, as a promising candidate to augment current research-based serological assays. In this study, we show that BmaA is an outer surface-associated protein by its susceptibility to protease digestion. Synthesis of BmaA in culture was independent of temperature at either 23 °C or 34 °C. The BmaA gene is present in two identical loci harbored on separate plasmids in North American strains LB-2001 and CT13-2396. bmaA-like sequences are present in other B. miyamotoi strains and relapsing fever borrelia as multicopy genes and as paralogous or orthologous gene families. IgM and IgG antibodies in pooled serum from BMD patients reacted with native BmaA fractionated by 2-dimensional gel electrophoresis and identified by mass spectrometry. IgG against recombinant BmaA was detected in 4 of 5 BMD patient serum samples as compared with 1 of 23 serum samples collected from patients with various stages of Lyme disease. Human anti-B. turicatae serum did not seroreact with recombinant BmaA suggesting a role as a species-specific diagnostic antigen. These results demonstrated that BmaA elicits a human host antibody response during B. miyamotoi infection but not in a tested group of B. burgdorferi-infected Lyme disease patients, thereby providing a potentially useful addition for developing BMD serodiagnostic tests.

Evaluation of Patient IgM and IgG Reactivity Against Multiple Antigens for Improvement of Serodiagnostic Testing for Early Lyme Disease.

Serologic testing is the standard for laboratory diagnosis and confirmation of Lyme disease. Serodiagnostic assays to detect antibodies against Borrelia burgdorferi, the agent of Lyme borreliosis, are used for detection of infection. However, serologic testing within the first month of infection is less sensitive as patients' antibody responses continue to develop. Previously, we screened several B. burgdorferi in vivo expressed antigens for candidates that elicit early antibody responses in patients with Stage 1 and 2 Lyme disease. We evaluated patient IgM seroreactivity against 6 antigens and found an increase in sensitivity without compromising specificity when compared to current IgM second-tier immunoblot scoring. In this study, we continued the evaluation using a multi-antigen panel to measure IgM plus IgG seroreactivity in these early Lyme disease patients' serum samples. Using two statistical methods for calculating positivity cutoff values, sensitivity was 70 and 84-87%, for early acute and early convalescent Lyme disease patients, respectively. Specificity was 98-100% for healthy non-endemic control patients, and 96-100% for healthy endemic controls depending on the statistical analysis. We conclude that improved serologic testing for early Lyme disease may be achieved by the addition of multiple borrelial antigens that elicit IgM and IgG antibodies early in infection.

Evaluation of in vivo expressed Borrelia burgdorferi antigens for improved IgM serodiagnosis of early Lyme disease.

Improved serologic tests are needed for accurate diagnosis and proper treatment of early stage Lyme disease. We evaluated the 3 antigens currently used for 2-tiered IgM immunoblot testing (FlaB, OspC, and BmpA) in combination with 3 additional antigens (BBA65, BBA70, and BBA73) and measured the sensitivity and specificity against a serum repository of positive and negative controls. Using 3 statistical methods for positivity cutoff determinations and scoring criteria, we found increased sensitivities for early Lyme disease when 2 of 6 antigens were positive as compared with the 2 of 3 antigen IgM criteria currently used for second-tier immunoblot scoring. Specificities for negative controls were comparable or superior to using 2 of 3 antigens. These results indicate that IgM sensitivity and specificity of serological testing for Lyme disease in the early stages of illness can be improved by employing antigens that target the initial host antibody responses.

Immunization of mice with Borrelia burgdorferi lp54 gene encoded recombinant proteins does not provide protection against tick transmitted infectious challenge.

The Borrelia burgdorferi outer surface membrane proteins BBA65, BBA66, BBA69, BBA70, and BBA73 were tested for their ability to confer protection against B. burgdorferi infection challenge. Mice were immunized with recombinant forms of the proteins singly or in combinations. Following initial protein inoculation and booster injections, seroconversion was confirmed prior to B. burgdorferi challenge by tick bite. Despite mice having high antibody titers for each antigen, no significant protections against the challenge infections were observed. These results demonstrate that these recombinant proteins were not protective and reflects the challenges confronted to identify effective novel vaccine candidates for Lyme disease.

Evaluation of Selected Borrelia burgdorferi lp54 Plasmid-Encoded Gene Products Expressed during Mammalian Infection as Antigens To Improve Serodiagnostic Testing for Early Lyme Disease.

Laboratory testing for the diagnosis of Lyme disease is performed primarily by serologic assays and is accurate for detection beyond the acute stage of the infection. Serodiagnostic assays to detect the early stages of infection, however, are limited in their sensitivity, and improvement is warranted. We analyzed a series of Borrelia burgdorferi proteins known to be induced within feeding ticks and/or during mammalian infection for their utility as serodiagnostic markers against a comprehensive panel of Lyme disease patient serum samples. The antigens were assayed for IgM and IgG reactivity in line immunoblots and separately by enzyme-linked immunosorbent assay (ELISA), with a focus on reactivity against early Lyme disease with erythema migrans (EM), early disseminated Lyme neuroborreliosis, and early Lyme carditis patient serum samples. By IgM immunoblotting, we found that recombinant proteins BBA65, BBA70, and BBA73 reacted with early Lyme EM samples at levels comparable to those of the OspC antigen used in the current IgM blotting criteria. Additionally, these proteins reacted with serum samples from patients with early neuroborreliosis and early carditis, suggesting value in detecting early stages of this disease progression. We also found serological reactivity against recombinant proteins BBA69 and BBA73 with early-Lyme-disease samples using IgG immunoblotting and ELISA. Significantly, some samples that had been scored negative by the Centers for Disease Control and Prevention-recommended 2-tiered testing algorithm demonstrated positive reactivity to one or more of the antigens by IgM/IgG immunoblot and ELISA. These results suggest that incorporating additional in vivo-expressed antigens into the current IgM/IgG immunoblotting tier in a recombinant protein platform assay may improve the performance of early-Lyme-disease serologic testing.

Evaluation of the Borrelia burgdorferi BBA64 protein as a protective immunogen in mice.

The Borrelia burgdorferi bba64 gene product is a surface-localized lipoprotein synthesized within mammalian and tick hosts and is involved in vector transmission of disease. These properties suggest that BBA64 may be a vaccine candidate against Lyme borreliosis. In this study, protective immunity against B. burgdorferi challenge was assessed in mice immunized with the BBA64 protein. Mice developed a high-titer antibody response following immunization with soluble recombinant BBA64 but were not protected when challenged by needle inoculation of culture-grown spirochetes. Likewise, mice passively immunized with an anti-BBA64 monoclonal antibody were not protected against needle-inoculated organisms. BBA64-immunized mice were subjected to B. burgdorferi challenge by the natural route of a tick bite, but these trials did not demonstrate significant protective immunity in either outbred or inbred strains of mice. Lipidated recombinant BBA64 produced in Escherichia coli was assessed for possible improved elicitation of a protective immune response. Although inoculation with this antigen produced a high-titer antibody response, the lipidated BBA64 also was unsuccessful in protecting mice from B. burgdorferi challenge by tick bites. Anti-BBA64 antibodies raised in rats eradicated the organisms, as evidenced by in vitro borreliacidal assays, thus demonstrating the potential for BBA64 to be effective as a protective immunogen. However, passive immunization with the same monospecific rat anti-BBA64 polyclonal serum failed to provide protection against tick bite-administered challenge. These results reveal the challenges faced in not only identifying B. burgdorferi proteins with potential protective capability but also in producing recombinant antigens conducive to preventive therapies against Lyme borreliosis.

Borrelia burgdorferi visualized in Ixodes scapularis tick excrement by immunofluorescence.

The enzootic cycle of Borrelia burgdorferi, the etiologic agent of Lyme disease, involves Ixodes spp. ticks and vertebrates. Resident tick Borrelia, harbored inside the midgut, are eventually expelled with the tick's saliva into the vertebrate host when a tick consumes a blood meal. During this 4- to 5-day feeding period I. scapularis will defecate onto the host's skin. Previously we detected borrelial DNA in tick feces throughout engorgement. In this study we report the microscopic examination for B. burgdorferi in nymphal excrement. Using immunofluorescence assays, we observed Borrelia in all mouse skin and capsule fecal swabs tested, although we could not culture the spirochetes. These results update our previous analysis by revealing that spirochetes can also be visualized in tick excrement. Furthermore, the results emphasize that borrelial contamination by defecation is a possibility, and that caution should be exercised by researchers investigating pathogen/host/vector interactions. The biological significance of the presence of non-culturable Borrelia in tick feces during engorgement is unclear.

Cloning, partial purification and in vivo developmental profile of expression of the juvenile hormone epoxide hydrolase of Ctenocephalides felis.

cDNAs encoding two different epoxide hydrolases (nCfEH1 and nCfEH2) were cloned from a cDNA library prepared from the wandering larval stage of the cat flea, Ctenocephalides felis. Predicted translations of the open reading frames indicated the clones encoded proteins of 464 (CfEH1) and 465 (CfEH2) amino acids. These proteins have a predicted molecular weight of 53 kDa and a putative 22 amino acid N-terminal hydrophobic membrane anchor. The amino acid sequences are 77% identical, and both are homologous to previously isolated epoxide hydrolases from Manduca sexta, Trichoplusia ni, and Rattus norvegicus. Purification of native juvenile hormone epoxide hydrolase (JHEH) from unfed adult cat fleas generated a partially pure protein that hydrolyzed juvenile hormone III to juvenile hormone III-diol. The amino terminal sequence of this;50-kDa protein is identical to the deduced amino terminus of the protein encoded by the nCfEH1 clone. Affinity-purified rabbit polyclonal antibodies raised against Escherichia coli-expressed HisCfEH1 recognized a approximately 50-kDa protein present in the partially purified fraction containing JHEH activity. Immunohistochemistry experiments using the same affinity-purified rabbit polyclonal antibodies localized the epoxide hydrolase in developing oocytes, fat body, and midgut epithelium of the adult flea. The presence of JHEH in various flea life stages and tissues was assessed by Northern blot and enzymatic activity assays. JHEH mRNA expression remained relatively constant throughout the different flea larval stages and was slightly elevated in the unfed adult flea. JHEH enzymatic activity was highest in the late larval, pupal, and adult stages. In all stages and tissues examined, JHEH activity was significantly lower than juvenile hormone esterase (JHE) activity, the other enzyme responsible for JH catalysis.

Evaluation of a recombinant salivary gland protein (thrombostasin) as a vaccine candidate to disrupt blood-feeding by horn flies.

The potential for controlling blood-feeding by the cattle pest, Haematobia irritans irritans (horn fly), was tested by vaccination against thrombostasin (TS), an inhibitor of mammalian thrombin that is released into skin during horn fly blood-feeding. The increase in blood meal size that occurred for flies feeding on sensitized non-vaccinated hosts was blocked and egg development in female flies was delayed when horn flies fed on rabbits and cattle immunized with recombinant TS. This demonstration of the impact of disrupting TS action by vaccination provides a novel approach toward control of this veterinary pest and offers a paradigm for limiting blood-feeding in other medically-important insect species.