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PubMed1990

Molecular basis for surface antigen size polymorphisms and conservation of a neutralization-sensitive epitope in Anaplasma marginale.

Anaplasmosis is one of several tick-borne diseases severely constraining cattle production and usage in many parts of the world. Cattle can be protected from anaplasmosis by immunization with major surface protein 1, a surface protein of Anaplasma marginale carrying a neutralization-sensitive epitope. Marked size polymorphisms exist among different isolates of A. marginale in the AmF105 subunit of major surface protein 1, yet all isolates still contain the neutralization-sensitive epitope. To clarify the basis for these observations, the mspl alpha gene encoding AmF105 was cloned from four isolates and sequenced. The encoded polypeptides share a high degree of overall homology between isolates but contain a domain with various numbers of tandemly repeated sequences and three regions of clustered amino acid substitutions outside the repeat domain. The polypeptide size differences are completely explained by the variations in the numbers of tandem repeat units. We have mapped the neutralization-sensitive epitope to a sequence that is present within each repeat unit. These results identify a basis for size polymorphisms of the surface polypeptide antigen concomitant with B-cell epitope conservation in rickettsiae.

Amino Acid Sequence↗
PubMed1999

Restriction of major surface protein 2 (MSP2) variants during tick transmission of the ehrlichia Anaplasma marginale.

Anaplasma marginale is an ehrlichial pathogen of cattle that establishes lifelong persistent infection. Persistence is characterized by rickettsemic cycles in which new A. marginale variant types, defined by the sequence of the expressed msp2 transcripts, emerge. The polymorphic msp2 transcripts encode structurally distinct MSP2 proteins and result in an antigenically diverse and continually changing A. marginale population within the blood. In this manuscript, we used sequence analysis of msp2 transcripts to show that a restricted repertoire of variant types, designated SGV1 and SGV2, is expressed within the tick salivary gland. The same SGV1 and SGV2 variant types were expressed in ticks regardless of the variant types expressed in the blood of infected cattle at the time of acquisition feeding by the ticks. Importantly, subsequent tick transmission to susceptible cattle resulted in acute rickettsemia composed of organisms expressing only the same SGV1 and SGV2 variant types. This indicates that the msp2 expressed by organisms within the tick salivary gland predicts the variant type responsible for acute rickettsemia and disease. This restriction of transmitted A. marginale variant types, in contrast to the marked diversity within persistently infected cattle, supports development of MSP2 vaccines to prevent acute rickettsemia in tick-transmitted infections.

Amino Acid Sequence↗
PubMed2003

Structurally distinct requirements for binding of P-selectin glycoprotein ligand-1 and sialyl Lewis x to Anaplasma phagocytophilum and P-selectin.

Colonization of neutrophils by the bacterium Anaplasma phagocytophilum causes the disease human granulocytic ehrlichiosis. The pathogen also infects mice, its natural host. Like binding of P-selectin, binding of A. phagocytophilum to human neutrophils requires expression of P-selectin glycoprotein ligand-1 (PSGL-1) and alpha1-3-fucosyltransferases that construct the glycan determinant sialyl Lewis x (sLex). Binding of A. phagocytophilum to murine neutrophils, however, requires expression of alpha1-3-fucosyltransferases but not PSGL-1. To further characterize the molecular features that A. phagocytophilum recognizes, we measured bacterial binding to microspheres bearing specific glycoconjugates or to cells expressing human PSGL-1 and particular glycosyltransferases. Like P-selectin, A. phagocytophilum bound to purified human PSGL-1 and to glycopeptides modeled after the N terminus of human PSGL-1 that presented sLex on an O-glycan. Unlike P-selectin, A. phagocytophilum bound to glycopeptides that contained sLex but lacked tyrosine sulfation or a specific core-2 orientation of sLex on the O-glycan. A. phagocytophilum bound only to glycopeptides that contained a short amino acid sequence found in the N-terminal region of human but not murine PSGL-1. Unlike P-selectin, A. phagocytophilum bound to cells expressing PSGL-1 in cooperation with sLex on both N-and O-glycans. Moreover, bacteria bound to microspheres coupled independently with glycopeptide lacking sLex and with sLex lacking peptide. These results demonstrate that, unlike P-selectin, A. phagocytophilum binds cooperatively to a nonsulfated N-terminal peptide in human PSGL-1 and to sLex expressed on PSGL-1 or other glycoproteins. Distinct bacterial adhesins may mediate these cooperative interactions.

Adhesins, Bacterial↗
PubMed2002

Superoxide anion production during Anaplasma phagocytophila infection.

Anaplasma phagocytophila persists within neutrophils and prevents the respiratory burst by inhibiting gp91(phox). Mutations in gp91(phox) result in chronic granulomatous disease (CGD), which is diagnosed by use of the nitroblue tetrazolium (NBT) and Fc-Oxyburst assays that examine whether cells produce O2-. This study assessed whether the NBT and Fc-Oxyburst assays could detect a respiratory burst during A. phagocytophila infection. O2- production was inhibited in HL-60 cells and neutrophils infected with A. phagocytophila. In a mouse model of A. phagocytophila infection, 15%+/-4% (mean+/-SD) of polymorphonuclear leukocytes from infected mice had an ineffective respiratory burst compared with 1%+/-1% (mean+/-SD) of the neutrophils from uninfected animals. A population of neutrophils that did not produce O2- was also detected in 2 patients with A. phagocytophila infection. These data demonstrate respiratory burst inhibition by A. phagocytophila in vivo and on an individual cell basis by use of assays designed to evaluate CGD.

Anaplasma↗
PubMed2003

Inability of a variant strain of Anaplasma phagocytophilum to infect mice.

Nymphal Ixodes scapularis ticks were collected from several sites in Rhode Island. Polymerase chain reaction and DNA sequencing were used to determine the presence and prevalence of Anaplasma phagocytophilum human agent (AP-ha) and a genetic variant not associated with human disease (AP-variant 1). The remaining ticks from each cohort were allowed to feed to repletion on either white-footed (Peromyscus leucopus) or DBA/2 (Mus musculus) mice. The engorged ticks and murine blood samples were evaluated for the presence of AP-ha and AP-variant 1. Although a high percentage of the infecting ticks harbored AP-variant 1, only AP-ha was amplified from the murine blood samples. Additional ticks were fed on immunocompromised SCID mice, and, again, only AP-ha was capable of establishing an infection, and only AP-ha could be detected by xenodiagnosis. These data suggest that AP-variant 1 cannot establish an infection in mice, and we propose that AP-variant 1 has an alternative natural reservoir, possibly white-tailed deer.

Anaplasma phagocytophilum↗
PubMed2004

Anaplasma phagocytophilum ligation to toll-like receptor (TLR) 2, but not to TLR4, activates macrophages for nuclear factor-kappa B nuclear translocation.

Anaplasma phagocytophilum is an obligate intracellular bacterium that infects neutrophils and causes human anaplasmosis (formerly human granulocytic ehrlichiosis). Interferon (IFN)- gamma causes immunopathology in A. phagocytophilum infection models. Plasma IFN- gamma levels are elevated 4 h after infection in experimentally infected mice, which indicates innate immunity and possible Toll-like receptors (TLRs). The ability of A. phagocytophilum to trigger proinflammatory responses via nuclear factor (NF)- kappa B was tested in TLR2- and TLR4-transfected cell lines and in primary murine macrophages devoid of TLR2 or TLR4. NF- kappa B was activated only through TLR2, which suggests its role in innate immune induction with A. phagocytophilum infections. The role of innate immunity in human anaplasmosis immunopathology requires more study.

Anaplasma phagocytophilum↗
PubMed2002

Characterization of the rRNA genes of Ehrlichia chaffeensis and Anaplasma phagocytophila.

The rRNA genes of Ehrlichia chaffeensis and Anaplasma phagocytophila have been analyzed. The 16S rRNA genes were previously characterized for both of these agents. Southern hybridization was used to show that there are single copies of both the 16S and 23S rRNA genes in the genomes of each organism, and that the 16S rRNA genes were upstream from the 23S rRNA genes by at least 16 and 11 Kb for E. chaffeensis and A. phagocytophila, respectively. PCR amplification and gene walking was used to sequence the 23S and 5S rRNA genes, and show that these genes are contiguous and are likely expressed as a single operon. The level of homology between the E. chaffeensis and A. phagocytophila 23S and 5S rRNA genes, and 23S-5S spacers, was 91.8, 81.5, and 40%, respectively. To confirm the hybridization data, genome walking was used to sequence downstream of the 16S rRNA genes, and although no tRNA genes were identified, open reading frames encoding homologues of the Escherichia coli succinate dehydrogenase, subunit C, were found in both E. chaffeensis and A. phagocytophila. Phylogenetic analysis using the 23S rRNA gene suggests that reorganization of the phylum Proteobacteria by division of the class Alphaproteobacteria into two separate subclasses, may be appropriate.

Amino Acid Sequence↗
PubMed2003

Characterization of the ftsZ gene from Ehrlichia chaffeensis, Anaplasma phagocytophilum, and Rickettsia rickettsii, and use as a differential PCR target.

Degenerate primers corresponding to highly conserved regions of previously characterized ftsZ genes were used to PCR amplify a portion of the ftsZ gene from the genomic DNA of Ehrlichia chaffeensis (ftsZ(Ech)), Anaplasma phagocytophilum (ftsZ(Ap)), and Rickettsia rickettsii (ftsZ(Rr)). Genome walking was then used to amplify the 5' and 3' termini of the genes. The DNA sequences of the resulting amplification products yielded open reading frames coding for proteins with molecular masses of 42.0, 45.7, and 48.3 kDa for A. phagocytophilum, E. chaffeensis, and R. rickettsii, respectively. These homologs are 20 to 70 amino acids longer than the FtsZ proteins characterized in bacteria such as Escherichia coli and Bacillus subtilis, but do not possess the large extended carboxyl-termini found in the FtsZ proteins of Bartonella, Rhizobium, and Agrobacterium species. The functional domains important for FtsZ activity are conserved within the ehrlichial and rickettsial FtsZ protein sequences. The R. rickettsii FtsZ sequence is highly homologous to the FtsZ protein previously described for Rickettsia prowazekii (89% identity), and identical to the FtsZ protein of Rickettsia conorii. The percent identity observed between the A. phagocytophilum and E. chaffeensis FtsZ proteins is only 79% and is particularly low in the carboxyl-terminal region (15.8% identity). Primers were designed to PCR amplify a portion of the variable carboxyl-terminal region of the ftsZ gene, and used to differentiate each agent based on the size of the amplicons: A. phagocytophilum, 278 bp; E. chaffeensis, 341 bp; and Rickettsia spp., 425 bp.

Amino Acid Sequence↗
PubMed2002

Comparison of the reservoir competence of medium-sized mammals and Peromyscus leucopus for Anaplasma phagocytophilum in Connecticut.

In the northeastern United States, Anaplasma phagocytophilum, the agent of human granulocytic ehrlichiosis (HGE), is transmitted by the tick vector Ixodes scapularis. The white-footed mouse Peromyscus leucopus is a competent reservoir for this agent, but the reservoir competence of non-Peromyscus hosts of I. scapularis has not been studied. Here, we report data confirming reservoir competence of medium-sized mammals for A. phagocytophilum. Raccoons, Virginia opossums, gray squirrels, and striped skunks were live-trapped in June-August of 1998-1999 at two locations in Connecticut. Captured animals were kept for several days at the laboratory in wire-mesh cages over water to allow naturally attached ticks to drop off. Samples of blood and serum were taken from each animal prior to its release at the site of capture. Engorged ticks collected from each animal were allowed to molt. Resulting I. scapularis nymphs and adults were tested for the presence of A. phagocytophilum DNA by polymerase chain reaction, as were the blood samples from the animals. A. phagocytophilum DNA was detected in the blood of >10% of the raccoons tested. Raccoons, opossums, squirrels, and skunks produced adult I. scapularis infected with the agent of HGE. Prevalence of infection was the highest in adult ticks fed as nymphs upon raccoons (23%) and the lowest in those fed upon skunks and opossums (5-7%). The agent was present in nymphal I. scapularis fed as larvae upon raccoons and squirrels, but not in ticks fed upon skunks or opossums. We also tested the ability of I. scapularis to transmit A. phagocytophilum to laboratory-reared white-footed mice after acquiring it from medium-sized mammals. Ticks that acquired the agent from raccoons and squirrels successfully transmitted it to mice. Thus, raccoons and gray squirrels are reservoir-competent for the agent of HGE-they become naturally infected, and are capable of transmitting the infection to feeding ticks.

Anaplasma phagocytophilum↗
PubMed2004

Transmission route efficacy and kinetics of Anaplasma phagocytophilum infection in white-footed mouse, Peromyscus leucopus.

Anaplasma phagocytophilum was used to infect Peromyscus leucopus mice by three routes of inoculation: infected tick infestation and intraperitoneal (IP) and subcutaneous (SQ) injection of infected tissue culture cells. A set of 12 mice were infected (four tick, four IP, and four SQ), and blood was drawn at 1, 3, 6, 9, 12, 15, 21, 28, 35, and 60 days post-infection and analyzed by use of a quantitative PCR assay to assess the level of infection. An additional set of 108 mice were infected (36 tick, 36 IP, 36 SQ) and euthanized at 1, 3, 6, 9, 12, 15, 21, 28, and 35 days post-infection (four mice/time point), and blood, spleen, bone marrow, and bladder tissue samples were analyzed. Tick infection generally produced the highest average levels of infection and peaked at 9 days post-infestation in blood, spleen, and bone marrow and at 6 days after infestation in the bladder. IP injection resulted in levels of infection that peaked on day 6 (spleen) or 12 (bladder, bone marrow, and blood). A. phagocytophilum injected SQ showed low levels of infection, and the day of peak infection varied. The average level of infection in the blood drawstressed mice was consistently higher and peaked earlier than infection in the non-stressed, euthanized mice. Xenodiagnosis was used to assay a third set of 12 mice (four tick, four IP, and four SQ) on days 7 and 14 post-infection and ticks fed on tick-infected mice showed the highest rate of PCR-positive test results at both time points (day 7, 22.2%; day 14, 17.3%). These data indicate that P. leucopus mice can be infected by tick infestation, IP injection, or SQ injection but that the kinetics and level of infection are quite variable among individual mice, may be influenced by the route of inoculation, and may be further altered by common laboratory procedures such as repeated collection of blood samples.

Anaplasma phagocytophilum↗
PubMed2006

Evaluation of white-tailed deer (Odocoileus virginianus) as natural sentinels for Anaplasma phagocytophilum.

Anaplasma phagocytophilum, the causative agent of human granulocytotropic anaplasmosis, can infect white-tailed deer (WTD; Odocoileus virginianus), and this species is a crucial host for adult Ixodes scapularis, the primary vector of A. phagocytophilum. The goal of this study was to determine the geographic distribution of A. phagocytophilum among WTD across a 19 state region and to evaluate the utility of WTD as natural sentinels. Serologic testing using the indirect fluorescent antibody (IFA) assay was conducted on WTD serum samples and molecular and xenodiagnostic tests were performed to confirm serologic results. The surveillance system was assessed through examination of vital attributes including WTD age and gender associations with serologic status, sample size adequacy for accurate infection status classification, and presence of the vector, I. scapularis. Six hundred thirty-three of 2,666 (24%) WTD in 17 states tested positive for antibodies (>or=128) when tested by IFA assay. Testing for p44 and/or 16S rRNA gene targets identified 73 (16%) PCR positive WTD among 458 animals tested, all of which originated from seropositive populations. Attempts to culture A. phagocytophilum from WTD were unsuccessful; however, xenodiagnostic mice inoculated with blood from 3 WTD became infected. Seroprevalence did not differ by deer age or gender; however, WTD<or=0.75 years old had a higher prevalence of PCR positivity. Using seroprevalence data, a sample size of 6-9 animals per population was projected to be adequate for identifying seropositive populations. The presence of I. scapularis was significantly associated with A. phagocytophilum antibodies in WTD. Collectively, the results of this study demonstrate that WTD would be suitable natural sentinels for this emerging zoonotic pathogen.

Age Distribution↗
PubMed2006

The root-vole Microtus oeconomus (Pallas, 1776): a new potential reservoir of Anaplasma phagocytophilum.

Anaplasma phagocytophilum infection is a recently emerged tick-borne zoonosis. The bacterium's reservoirs likely comprise cervids, some ruminants, rodents, and perhaps other small and intermediate-size mammals; the main vector in Europe is the Ixodes ricinus tick. The Białowieza Primeval Forest is an ecosystem with a known prevalence of tick-borne pathogens. We studied the root-vole Microtus oeconomus to evaluate the natural infection of A. phagocytophilum. Intragranulocytic bacterial clusters (morulae) were not seen, but the A. phagocytophilum-specific nested polymerase chain reaction (PCR) product, targeting the rrs gene, was detected in two out of 30 rodent samples (GenBank accession nos. DQ361024 and DQ361025). Twenty-six root vole (86.6%) hosted ticks, mainly Dermacentor reticulatus larvae and nymphs. Only two rodents were parasitazed by I. ricinus single larvae. These data show the presence of natural infection of A. phagocytophilum among the root-vole M. oeconomus in the Białowieza Primeval Forest ecosystem.

Anaplasma phagocytophilum↗
PubMed2006

Serosurveillance for Anaplasma phagocytophilum antibodies in white-tailed deer (Odocoileus virginianus) in Iowa, USA.

Cases of human granulocytic anaplasmosis have increased in number and are being identified in new geographic areas since its discovery in 1994. White-tailed deer (WTD) become infected with the causative agent, Anaplasma phagocytophilum, and serve as natural sentinels for this organism. In order to determine if A. phagocytophilum is present in the state of Iowa, sera collected from 628 WTD in 2004 from 13 sites and from 282 WTD in 1999 from a single, common site were tested by enzyme-linked immunosorbent assay and Western immunoblotting. A seroprevalence of 9.1% was found among the 2004 samples, and there was no change in seropositivity rates from 1999 to 2004 at the single, common site. As A. phagocytophilum is another tick-borne human pathogen to be identified in the state of Iowa, this study has important implications for health care providers.

Anaplasma phagocytophilum↗
PubMed2006

Sympatric Ixodes trianguliceps and Ixodes ricinus ticks feeding on field voles (Microtus agrestis): potential for increased risk of Anaplasma phagocytophilum in the United Kingdom?

The importance of wild rodents as reservoirs of zoonotic tick-borne pathogens is considered low in the United Kingdom because, in studies to date, those parasitized by exophilic Ixodes ricinus ticks carry almost exclusively larvae and thus have a minor role in transmission cycles. In a cross-sectional study, 11 (6.7%) of 163 field voles (Microtus agrestis) captured at field sites in Northern England were PCR-positive for Anaplasma phagocytophilum. The voles were found to act as hosts for both larval and nymphal I. ricinus and all stages of the nidicolous tick I. trianguliceps, and eight individuals were infested with ticks of both species at the same time. Two of 158 larval and one of 13 nymphal I. ricinus, as well as one of 14 larval and one of 15 nymphal I. trianguliceps collected from the rodents were PCR-positive. These findings suggest that habitats where field voles are abundant in the United Kingdom may pose a risk of A. phagocytophilum infection because (i) field voles, the most abundant terrestrial mammal in the United Kingdom, may be a competent reservoir; (ii) the field voles are hosts for both nymphal and larval ixodid ticks so they could support endemic cycles of A. phagocytophilum; and (iii) they are hosts for nidicolous I. trianguliceps, which may alone maintain endemic cycles, and exophilic I. ricinus ticks, which could act as a bridge vector and transmit infections to humans and domesticated animals.

Anaplasma phagocytophilum↗
PubMed2006

Use of real-time quantitative PCR targeting the msp2 protein gene to identify cryptic Anaplasma phagocytophilum infections in wildlife and domestic animals.

Anaplasma phagocytophilum is an emerging pathogen throughout much of the Holarctic, where Ixodes spp. tick vectors occur. This organism was expected to be present at study sites in Humboldt County, north-western California, based on the presence of appropriate tick vectors, seropositivity in sentinel hosts, and previously reported human infections. However, despite high seroprevalence suggesting circulating A. phagocytophilum, active infections in dogs and wildlife (including suspected reservoir species) were rare using published polymerase chain reaction (PCR) protocols. This finding was possible if the published PCR protocol lacked sensitivity for strains in the study areas. We report a new TaqMan-PCR (TM-PCR) assay targeting the msp2 gene that has greater sensitivity and specificity for diverse A. phagocytophilum strains from this region. The new assay detected as few as one plasmid copy and a range of genetically diverse strains of A. phagocytophilum. Specificity was confirmed by failure to amplify targets of closely related bacteria. Application of the TM-PCR to samples from northern California confirmed PCR-positivity in 94 woodrats (71%; n=134), three (4%; n=80) bears, and seven (7%; n=97) domestic dogs. The msp2 TM-PCR protocol appears to be more sensitive for use in assays of samples from parts of western North America and possibly in other regions where populations are genetically diverse or divergent from eastern United States strains of A. phagocytophilum.

Anaplasma phagocytophilum↗
PubMed2006

Co-detection of Bartonella henselae, Borrelia burgdorferi, and Anaplasma phagocytophilum in Ixodes pacificus ticks from California, USA.

Presence of Bartonella DNA was explored in 168 questing adult Ixodes pacificus ticks from Santa Cruz County, California. Bartonella henselae type I DNA was amplified from 11 ticks (6.55%); previously, two (1.19%) were found to be infected with Borrelia burgdorferi and five (2.98%) with Anaplasma phagocytophilum. Detection of B. henselae was not dependent on co-infection. The present study offers additional evidence that Ixodes spp. ticks may act as hosts and possibly vectors for B. henselae.

Anaplasma phagocytophilum↗
PubMed1992

Development of Anaplasma ovis (Rickettsiales: Anaplasmataceae) in male Dermacentor andersoni (Acari: Ixodidae) transferred from infected to susceptible sheep.

The development of Anaplasma ovis was studied in Dermacentor andersoni males transferred from infected to susceptible sheep. Laboratory-reared male D. andersoni were allowed to feed for 6 d on a sheep with ascending A. ovis parasitemia. The ticks were removed and held at room temperature in a humidity chamber for 6 d, after which they were allowed to feed on five susceptible sheep for 1, 3, 5, 7, or 9 d. Gut and salivary glands were collected from ticks during the 21-d experiment and examined with light and electron microscopy. Anaplasmosis developed in all susceptible sheep. Colonies of A. ovis were first observed in midgut epithelial cells on the 3rd d ticks fed on the infected sheep, and infection persisted in gut cells throughout the experiment. The first colonies contained one large organism that subsequently gave rise to many reticulated ones, which became electron dense over time. After ticks were transferred to susceptible sheep and began the second feeding, individual A. ovis organisms were found from days 3-9 in muscle cells on the hemocoel side of the gut basement membrane. However, colonies did not develop in these cells, and the host cells did not hypertrophy as did cells similarly infected with A. marginale. A final site of development of A. ovis was in salivary glands. Individual organisms were first seen in acinar cells on the first day that ticks fed on the second calves, and salivary gland infections persisted throughout the 9-d feeding period. Colonies of A. ovis developed in salivary gland acinar cells and organisms within these colonies were initially electron lucent but became electron dense. Multiple colonies often were observed within salivary gland cells and often contained organisms in various stages of development.

Anaplasma↗
PubMed1993

Detection of Anaplasma marginale (Rickettsiales: Anaplasmataceae) in secretagogue-induced oral secretions of Dermacentor andersoni (Acari: Ixodidae) with the polymerase chain reaction.

The polymerase chain reaction (PCR) was used to detect Anaplasma marginale in secretagogue-induced oral secretions of male and female Dermacentor andersoni Stiles exposed as nymphs or adults by feeding on infected calves. A 409-bp DNA fragment derived from the A. marginale (Florida isolate) msp1 beta gene was amplified with oligonucleotide primers BAP-2 (5'-GTATGGCACGTAGTCTTGGGATCA-3') and AL34S (5'-CAGCAGCAGCAAGACCTTCA-3'). The target DNA was amplified in oral secretions of female ticks exposed to A. marginale as adults and stimulated to secrete by injection of dopamine. Conversely, A. marginale was detected in saliva from prefed female ticks exposed as nymphs only after stimulation with a combination of dopamine, gamma-aminobutyric acid, pilocarpine, and theophylline. Saliva from ticks exposed as nymphs and stimulated with ergot alkaloids did not contain the A. marginale target DNA. Saliva collected after 11 d of feeding from dopamine-stimulated male ticks contained A. marginale DNA. The results indicate that A. marginale is present in tick saliva and suggest that the parasite can be transmitted to cattle via saliva of feeding ixodid ticks. The variable appearance of A. marginale in saliva, regardless of the method used to induce salivation, suggests that transmission of A. marginale may be affected by the physiological state of the tick.

Anaplasma↗