Immunization with adenoviral-vectored tick salivary gland proteins (SALPs) in a murine model of Lyme borreliosis.

Prior exposure of vertebrate hosts to tick salivary proteins can induce specific immunity to tick infestation, as well as affording protection against tick-transmitted Borrelia burgdorferi infection in the mammalian host. Vaccination using an adenovirus expression system to deliver 4 tick salivary proteins (Ad-Salps) derived from Ixodes scapularis, Salp15, Salp25A, Salp25D, and Isac, was explored. Results indicate that vaccination with tick salivary proteins in an adenoviral vector can be used to modulate a Th1 response in the host and partially control spirochete load in immunized mice after infected tick challenge.

Bioprocess and bioreactor: next generation technology for production of potential plant-based antidiabetic and antioxidant molecules.

Globally, diabetes and obesity are two of the most common metabolic diseases of the 21(st) century. Increasingly, not only adults but children and adolescents are being affected. New approaches are needed to prevent and treat these disorders and to reduce the impact of associated disease-related complications. Industrial-scale production using plant-root cultures can produce quantities and quality of inexpensive bioactive small molecules with nutraceutical and pharmaceutical properties. Using this approach, and targeting these diseases, a next generation approach to tackling this emerging global health crisis may be developed. Adventitious roots cultured in bioreactors under controlled and reproducible conditions have been shown effective for production of natural products. The liquid-phase airlift bioreactor in particular has been used successfully for culturing roots on an industrial-scale and thus may provide an economical production platform for expressing promising plant-based antidiabetic and antioxidant molecules. This review focuses on a next-generation, scalable, bioprocessing approach for adventitious and hairy root cultures that are a pesticide-free, seasonally-independent, plant-based source of three molecules that have shown promise for the therapeutic management of diabetes and obesity: corosolic acid, resveratrol and ginsenosides.

Kinetics of Borrelia burgdorferi infection in larvae of refractory and competent tick vectors.

The acquisition of Borrelia burgdorferi by the larvae of competent and refractory ixodid ticks was assessed by quantitative polymerase chain reaction (PCR). Larvae were fed on infected mice, and the spirochete loads were determined during feeding and up to 93 d postfeeding. Amblyomma americanum (L.) was refractory to B. burgdorferi infection, with almost no detection of spirochete DNA during or postfeeding. In contrast, Ixodes scapularis Say supported high loads of spirochetes (10(3)-10(4) per larva). In Dermacentor variabilis (Say), B. burgdorferi uptake was reduced, with an average of 16 spirochetes per larvae acquired after 4 d of feeding, representing 1/195 of the counts in I. scapularis. However, during the first day postfeeding, the spirochete growth rate in D. variabilis reached 0.076 generations per hour, 7.7 times greater than the highest growth rate detected in I. scapularis. D. variabilis supported intense spirochete growth up to the fourth day postinfection, when the counts increased to an average of 282 spirochetes per larvae or 1/8.5 of the I. scapularis counts 4 d postfeeding. The kinetics of spirochete growth was unstable in D. variabilis compared with I. scapularis, and transmission of B. burgdorferi by D. variabilis could not be demonstrated. A cofeeding experiment indicated that I. scapularis feeding increased A. americanum spirochete uptake. These collective results indicate suboptimal conditions for B. burgdorferi uptake and colonization within A. americanum or the presence of anti-Borrelia factor(s) in this nonpermissive tick species.

Capillary feeding of specific dsRNA induces silencing of the isac gene in nymphal Ixodes scapularis ticks.

Ixodes scapularis transmits several pathogens including Borrelia burgdorferi. Bioactive compounds in tick saliva support tick feeding and influence pathogen transmission to the mammalian host. These studies utilized oral delivery of dsRNA to silence an anticomplement gene (isac) in I. scapularis nymphs. Silencing of isac significantly reduced fed-tick weight compared to delivery of control lacZ dsRNA, and immunoblots specific for FlaB protein indicated a reduction in spirochete load in isac-silenced infected nymphs. SDS-PAGE demonstrated that isac gene silencing affected expression of a number of salivary and non-salivary gland proteins in ticks. Finally, multiple isac cDNA homologues were cloned, and these may represent a new gene family coexpressed during tick feeding. This work presents a novel oral delivery approach for specific gene silencing in I. scapularis nymphs and characterizes the effect of isac on blood-feeding in an attempt to block transmission of B. burgdorferi.

Differential infectivity of the Lyme disease spirochete Borrelia burgdorferi derived from Ixodes scapularis salivary glands and midgut.

Blood fed nymphal Ixodes scapularis Say infected with Borrelia burgdorferi were dissected to obtain salivary gland and midgut extracts. Extracts were inoculated into C3H/HeJ mice, and ear, heart, and bladder were cultured to determine comparative infectivity. Aliquots of extracts were then analyzed by quantitative polymerase chain reaction to determine the number of spirochetes inoculated into mice. A comparative median infectious dose (ID50) was determined for both salivary gland and midgut extract inoculations. Our data demonstrated a statistically significant difference (P < 0.002) in the ID50 derived from salivary gland (average = 18) versus midgut (average = 251) extracts needed to infect susceptible mice. A rationale for the differential infectivity of salivary and midgut derived spirochetes is discussed.

Borreliacidal activity of saliva of the tick Amblyomma americanum.

Amblyomma americanum (Linneaus) (Acari: Ixodidae), an important tick vector of human and animal disease, is not a competent vector of the bacterial agent of Lyme disease, Borrelia burgdorferi, although its range overlaps the geographical distribution of Lyme disease within the United States. A possible mechanism that could prevent acquisition of B. burgdorferi spirochetes from infected hosts is the toxic effect of A. americanum saliva on B. burgdorferi. The data presented here indicate that after 24 and 48 h of exposure to A. americanum saliva, significantly fewer B. burgdorferi were alive compared to treatment controls as assessed by spirochete motility under dark-field microscopy and resistance to the dead stain, propidium iodide. After 48 h, fewer than 13% of saliva-exposed B. burgdorferi were alive. In contrast, significantly more B. burgdorferi exposed to Ixodes scapularis (Acari: Ixodidae) saliva survived after 24 or 48 h compared to A. americanum saliva or treatment controls.

Sustained-release formulation of doxycycline hyclate for prophylaxis of tick bite infection in a murine model of Lyme borreliosis.

The prophylactic potential of a single injection of sustained-release doxycycline hyclate (Atridox) was compared to that of a single oral dose of doxycycline hyclate in a murine model of Lyme borreliosis. Prophylaxis, as measured by the lack of cultivable spirochetes and demonstrable pathology, was noted for 43% of orally treated mice; in contrast, the sustained-release doxycycline hyclate completely protected mice from infection and resultant pathology.

How much pilocarpine contaminates pilocarpine-induced tick saliva?

Pilocarpine is often applied or injected into ticks to induce salivation, and the resulting saliva used to test for various pharmacological, biochemical and immunological activities. To measure the amount of pilocarpine in pilocarpine-induced tick saliva, an HPLC-MS/MS method, based on capillary strong cation exchange chromatography online with an ion trap mass spectrometer, was used to measure pilocarpine in the pg to ng range. Results indicate large concentrations of pilocarpine in Ixodes scapularis Say and Amblyomma americanum (Linnaeus) (Acari: Ixodidae) saliva, ranging from 3 to 50 mm. Due to the known effects of pilocarpine on smooth muscle and immune cells, appropriate controls are proposed and discussed for proper interpretation of results using this saliva preparation.

A preliminary linkage map of the hard tick, Ixodes scapularis.

A linkage map of the Ixodes scapularis genome was constructed, based upon segregation amongst 127 loci. These included 84 random amplified polymorphic DNA (RAPD) markers, 32 Sequence-Tagged RAPD (STAR) markers, 5 cDNAs, and 5 microsatellites in 232 F1 intercross progeny from a single, field-collected P1 female. A preliminary linkage map of 616 cM was generated across 14 linkage groups with one marker every 10.8 cM. Assuming a genome size of approximately 109 bp, the relationship of physical to genetic distance was found to be approximately 300 kb/cM in the I. scapularis genome.

A preliminary linkage map of the tick, Ixodes scapularis.

A linkage map of the Ixodes scapularis genome was constructed based upon segregation amongst 127 loci. These included 84 random amplified polymorphic DNA (RAPD) markers, 32 Sequence-Tagged RAPD (STAR) markers, 5 cDNAs, and 5 microsatellites in 232 F1 intercross progeny from a single, field-collected P1 female. A preliminary linkage map of 616 cM was generated across 14 linkage groups with one marker every 10.8 cM. Assuming a genome size of approximately 10(9) bp, the relationship of physical to genetic distance is approximately 300 kb/cM in the I. scapularis genome.

Isolation and characterization of Borrelia parkeri in Ornithodoros parkeri (Ixodida: Argasidae) collected in Colorado.

This study describes the identification of Borrelia parkeri spirochetes in Colorado. Two isolates of B. parkeri (6230 and 6232) were recovered from Ornithodoros parkeri Cooley ticks collected at an inactive prairie dog town in Moffat County. Both isolates were partially characterized by sequencing and subsequent parsimony and neighbor-joining analyses of appropriate regions of the 16S ribosomal RNA, flagellin and P66 genes. Analyses of the 16S gene sequences from the Colorado isolates indicated that they were more closely related to B. parkeri and B. tucatae than to B. hermsii or the other species of Borrelia investigated in this study. Additional analyses of amino acid sequences for flagellin and P66, however, clearly demonstrated that isolates 6230 and 6232 were most closely related to B. parkeri. The possible significance of B. parkeri as an agent of human disease is discussed.

Resistance to Lyme disease in decorin-deficient mice.

Microbial adhesion to the host tissue represents an early, critical step in the pathogenesis of most infectious diseases. BORRELIA: burgdorferi, the causative agent of Lyme disease (LD), expresses two surface-exposed decorin-binding adhesins, DbpA and DbpB. A decorin-deficient (Dcn(-/-)) mouse was recently developed and found to have a relatively mild phenotype. We have now examined the process of experimental LD in Dcn(-/-) mice using both needle inoculation and tick transmission of spirochetes. When exposed to low doses of the infective agent, Dcn(-/-) mice had fewer Borrelia-positive cultures from most tissues analyzed than did Dcn(+/+) or Dcn(+/-) mice. When the infection dose was increased, similar differences were not observed in most tissues but were seen in bacterial colonization of joints and the extent of Borreila-induced arthritis. Quantitative PCR demonstrated that joints harvested from Dcn(-/-) mice had diminished Borrelia numbers compared with issues harvested from Dcn(+/+) controls. Histological examination also revealed a low incidence and severity of arthritis in Dcn(-/-) mice. Conversely, no differences in the numbers of Borreila-positive skin cultures were observed among the different genotypes regardless of the infection dose. These differences, which were observed regardless of genetic background of the mice (BALB/c or C3H/HeN) or method of infection, demonstrate the importance of decorin in the pathogenesis of LD.

Infection of Ixodes scapularis (Acari: Ixodidae) with Borrelia burgdorferi using a new artificial feeding technique.

To study interactions between Ixodes scapularis (Say) and Borrelia burgdorferi, an artificial feeding system was refined to allow controlled manipulation of single variables. The feeding system uses a mouse skin mounted on a water-jacketed glass membrane feeder. I. scapularis were infected using either BSK-H-cultured B. burgdorferi spirochetes or a B. burgdorferi-infected mouse skin as the source of spirochetes. Sixty-six percent of nymphs successfully fed to repletion using the artificial feeding systems with at least 75% of nymphs becoming infected with B. burgdorferi. Strain B31 B. burgdorferi spirochetes from passages 2-17 were equally infectious to nymphal ticks. At concentrations of one spirochete per microliter, 12% of nymphs acquired infection and 14 and 100 spirochetes per microliter resulted in 50 and 100% infection rates, respectively. Eighty-nine percent of nymphs fed by artificial feeding molted to the adult stage. When subsequently fed as adults, these I. scapularis successfully transmitted infectious B. burgdorferi spirochetes to mice.

Identification of an IL-2 binding protein in the saliva of the Lyme disease vector tick, Ixodes scapularis.

A potent inhibitor of mitogen-stimulated T cell proliferation exists in the saliva of several species of hard ticks, including the Lyme disease vector tick, Ixodes scapularis. Our characterization of this phenomenon has led to the identification of a possible mechanism for the T cell inhibitory activity of I. scapularis saliva. The T cell inhibitor can overcome stimulation of mouse spleen cells with anti-CD3 mAb; however, a direct and avid interaction with T cells does not appear to be necessary. Tick saliva inhibits a mouse IL-2 capture ELISA, suggesting that a soluble IL-2 binding factor is present in the saliva. This hypothesis was verified by using a direct binding assay in which plate-immobilized tick saliva was shown to bind both mouse and human IL-2. Elimination of the IL-2 binding capacity of saliva in the in vitro assays by trypsin digestion demonstrated that the IL-2 binding factor is a protein. These experiments comprise the first demonstration of the existence of such a secreted IL-2 binding protein from any parasite or pathogen. This arthropod salivary IL-2 binding capacity provides a simple mechanism for the suppression of T cell proliferation as well as for the activity of other immune effector cells that are responsive to IL-2 stimulation. Relevance of the tick T cell inhibitory activity to the human immune system is demonstrated by the ability of tick saliva to inhibit proliferation of human T cells and CTLL-2 cells grown in the presence of human IL-2.

An analysis of spirochete load, strain, and pathology in a model of tick-transmitted Lyme borreliosis.

Four laboratory-grown, low-passage isolates of Borrelia burgdorferi sensu stricto, B31, JD-1, 910255, and N40, were incorporated into Ixodes scapularis ticks to examine the pathogenesis of these isolates in mice after tick transmission. All isolates induced multifocal, lymphoid nodular cystitis, subacute, multifocal, necrotizing myocarditis, and a localized periostitis and arthritis of the femorotibial joint 6-18 weeks after tick infestation. In terms of the number of mice that demonstrated pathology in bladder, heart, and joint, the highest incidence of lesions occurred 12 weeks after tick bite. Utilizing the Taqman quantitative polymerase chain reaction (q-PCR) fluorogenic detection technology to amplify a conserved region of the flagellin gene, a trend was demonstrated between the number of spirochetes in tissue with duration of pathology. The q-PCR assay developed for this study was sensitive and could reliably measure as few as 1 to 10 spirochetes in the target tissues tested. A higher percentage of B31- and N40-infected mice (92 and 100%, respectively) developed myocarditis than JD-1- or 910255-infected mice (67 and 46%, respectively) 12 weeks after tick bite. The amount of spirochetal DNA that could be amplified for heart at this time point was not statistically different between isolates, indicating a difference in virulence between B31 and N40 relative to JD-1 and 910225. N40-infected mice demonstrated a significantly higher spirochete load (an average of 1.23 spirochetes/mg of tissue, p = 0.045) in femorotibial joints 18 weeks after infection, with 60% of these mice maintaining lesions compared with those infected with B31 (13%), JD-1 (25%), or 910255 (50%), which averaged <0.5 spirochetes/mg of tissue. This mouse model of Lyme borreliosis, including the ability to monitor lesion development and spirochete load, can facilitate the testing of therapeutic regimens for the later stages of tick-transmitted Lyme disease and help investigate aspects of the immunopathogenesis of lesion development.

Coinfection with Borrelia burgdorferi and the agent of human granulocytic ehrlichiosis suppresses IL-2 and IFN gamma production and promotes an IL-4 response in C3H/HeJ mice.

Previously we demonstrated that Borrelia burgdorferi transmission by Ixodes scapularis suppressed IL-2 and IFN gamma production and promoted IL-4 production in mice. The present studies were conducted to determine whether coinfection with the human granulocytic ehrlichiosis (HE) agent would promote a Th2 cytokine response in mice. Transmission to the spleen of the agent of human granulocytic ehrlichiosis (aoHGE) and B. burgdorferi occurred 4 and 7 days, respectively, after tick infestation. Coinfection synergized to suppress splenic IL-2 production 7-14 days after tick infestion. Transmission of B. burgdorferi or aoHGE alone significantly decreased splenic IFN gamma 4-7 days after tick infestation, while coinfection suppressed IFN gamma production 7-14 days after tick infestation. Splenic IL-4 production was significantly increased 4 days after coinfection, and by day 10, aoHGE plus B. burgdorferi induced greater splenic IL-4 (57.2 pg/ml, 348% of control values) than either organism transmitted alone (aoHGE, 22.7 pg/ml, B. burgdorferi, 25.1 pg/ml). Coinfection enhanced expansion of splenic T cells, CD4+ lymphocytes and B cells while decreasing CD8+ T cells. These data demonstrate that aoHGE and B. burgdorferi, when cotransmitted, suppress a systemic IL-2 and IFN gamma response, while strongly promoting systemic IL-4 production in the susceptible host. The antigen(s) responsible for this polarization are unknown and will be the subject of future studies.

Vector competence of Ixodes muris (Acari: Ixodidae) for Borrelia burgdorferi.

The vector competence of Ixodes muris (Bishopp & Smith) was determined for Borrelia burgdorferi, the etiologic agent of Lyme disease. Larval I. muris were fed on ICR outbred mice infected with the B-31 laboratory strain of B. burgdorferi. Replete larvae, at 5 d after feeding, were assayed for infection by culture in Barbour-Stoner-Kelly (BSK-H) media. Infection frequency in I. muris replete larvae was 66%. Resultant nymphs were fed on naive ICR outbred mice to determine the ability of I. muris to transmit infection. Infection frequency in fed nymphs declined to 38% and only 1/5 mice was positive for B. burgdorferi on ear biopsy culture. We demonstrated that I. muris is capable of acquiring and transmitting B. burgdorferi but is a relatively poor vector compared with I. scapularis (Say).

Transmission of the agent of human granulocytic ehrlichiosis by Ixodes spinipalpis ticks: evidence of an enzootic cycle of dual infection with Borrelia burgdorferi in Northern Colorado.

Previous work described an enzootic cycle of Borrelia burgdorferi sensu lato (hereafter referred to as B. burgdorferi) maintained by the rodent Neotoma mexicana and the tick Ixodes spinipalpis in northern Colorado. We investigated the incidence of coinfection among rodents with the agent of human granulocytic ehrlichiosis (aoHGE). aoHGE was detected in 23.5% of 119 rodent spleens examined. Biopsy results indicated that 78 (65.5%) of the 119 rodents were positive for B. burgdorferi, whereas 22 (78.5%) of the 28 animals that harbored aoHGE were also infected with B. burgdorferi. In 14 of 25 I. spinipalpis tick pools, aoHGE was detected by amplifying both the 16s rRNA and p44 gene of aoHGE. The ability of I. spinipalpis to transmit aoHGE was examined in C3H/HeJ mice. aoHGE was detected in their blood 5 days after I. spinipalpis infestation. This study confirms that both B. burgdorferi and aoHGE can be transmitted by I. spinipalpis ticks and that there is a high incidence of coinfection in rodents, predominantly Peromyscus maniculatus and N. mexicana, that inhabit the foothills of northern Colorado.

Geographic survey of vector ticks (Ixodes scapularis and Ixodes pacificus) for infection with the Lyme disease spirochete, Borrelia burgdorferi.

Populations of adult Ixodes scapularis and Ixodes pacificus, the two principal vectors of Lyme disease spirochetes in the United States, were collected from 17 sites in 12 states. Female ticks were fed on experimental rabbits; ticks and rabbits were subsequently examined for infection with Borrelia burgdorferi. Fourteen rabbits were exposed to I. scapularis ticks from the northeastern states of Connecticut, New York, New Jersey, and Maryland; all 14 rabbits became infected with B. burgdorferi. A total of 165/226 (73%) of these northeastern ticks was infected. Similarly, ticks from the midwestern states of Michigan, Wisconsin, and Minnesota transmitted infection to all three exposed rabbits; 29/51 (57%) of these midwestern I. scapularis were infected. In marked contrast, none of the 12 rabbits exposed to I. scapularis ticks from the southeastern states of South Carolina, Georgia, Florida, and Mississippi acquired infection with B. burgdorferi, and 0/284 (0%) of these ticks contained spirochetes. Four rabbits were exposed to I. pacificus collected from one location in California; 2/4 of these rabbits acquired infection and 2/57 (4%) of the I. pacificus were infected with B. burgdorferi. The antigenic profiles of all 58 strains tested were consistent with an identity of B. burgdorferi sensu lato. The availability of a human Lyme disease vaccine adds urgency to our efforts to calculate the ecological transmission risk throughout the United States, as an aid to the judicious use of such a vaccine.

Influence of outer surface protein A antibody on Borrelia burgdorferi within feeding ticks.

Borrelia burgdorferi, the spirochetal agent of Lyme disease, is transmitted by Ixodes ticks. When an infected nymphal tick feeds on a host, the bacteria increase in number within the tick, after which they invade the tick's salivary glands and infect the host. Antibodies directed against outer surface protein A (OspA) of B. burgdorferi kill spirochetes within feeding ticks and block transmission to the host. In the studies presented here, passive antibody transfer experiments were carried out to determine the OspA antibody titer required to block transmission to the rodent host. OspA antibody levels were determined by using a competitive enzyme-linked immunosorbent assay that measured antibody binding to a protective epitope defined by monoclonal antibody C3.78. The C3.78 OspA antibody titer (>213 microgram/ml) required to eradicate spirochetes from feeding ticks was considerably higher than the titer (>6 microgram/ml) required to block transmission to the host. Although spirochetes were not eradicated from ticks at lower antibody levels, the antibodies reduced the number of spirochetes within the feeding ticks and interfered with the ability of spirochetes to induce ospC and invade the salivary glands of the vector. OspA antibodies may directly interfere with the ability of B. burgdorferi to invade the salivary glands of the vector; alternately, OspA antibodies may lower the density of spirochetes within feeding ticks below a critical threshold required for initiating events linked to transmission.