Structural analysis of a p44/msp2 expression site of Anaplasma phagocytophilum in naturally infected ticks in Japan

Strains of Anaplasma phagocytophilum from horses in Ohio are related to isolates from humans in the northeastern USA

IMPORTANCE

The tick-borne obligatory intracellular bacterium Anaplasma phagocytophilum infects humans as well as domesticated and wild animals, causing a febrile disease collectively called granulocytic anaplasmosis. The epidemiology and the host species specificity and zoonotic potential of A. phagocytophilum strains remain unclear. In this study, ankA (encoding ankyrin A) and p44 gene sequences of A. phagocytophilum were determined in clinical specimens from horses in Ohio and compared with those found in A. phagocytophilum strains from various hosts and geographic regions. With increasing numbers of seropositive horses, the study points out the unrecognized prevalence and uncharacterized strains of A. phagocytophilum infection in horses and the importance of A. phagocytophilum molecular testing for the prevention of equine and human granulocytic anaplasmosis.

Altered gene expression profile of Wolbachia pipientis wAlbB strain following transinfection from its native host Aedes albopictus to Aedes aegypti cells

Wolbachia is an obligate intracellular bacterial symbiont prevalent among arthropods and nematodes. To survive and reproduce, Wolbachia interacts with and modifies host subcellular structures, while sensing and responding to changes within the cellular environment. In mutualistic associations, Wolbachia may provision the host with metabolites, or help to maintain the chemical homeostasis of the host cell. Some strains can rapidly invade insect populations by manipulating host reproductive biology, while also preventing viral replication, allowing their use in vector control of arthropod-borne viruses. The Aedes albopictus-derived strain wAlbB is promising in this regard. When transinfected into the Yellow fever mosquito, Aedes aegypti, wAlbB reaches high frequencies within wild populations, and strongly inhibits viral transmission. Despite its obvious potential, much is still unknown about the molecular interactions between Wolbachia and host that enable its use in vector control. Furthermore, most Wolbachia transinfection research to date has focused on host effects. In the current study, we used a cell line model to explore the effect of transinfection of wAlbB from Ae. albopictus to Ae. aegypti. Using RNA sequencing, we show that several genes associated with host-symbiont interactions were downregulated by transinfection, with the greatest downregulation exhibited by prophage-associated genes.

Molecular Detection and Characterization of p44/msp2 Multigene Family of Anaplasma phagocytophilum from Haemaphysalis longicornis in Mie Prefecture, Japan

Anaplasma phagocytophilum is an obligate intracellular bacterium that causes human granulocytic anaplasmosis (HGA), an emerging tick-borne infectious disease. This bacterium expresses various 44-kDa major outer membrane proteins encoded by the p44/msp2 multigene family to avoid the host immune system. We previously detected A. phagocytophilum p44/msp2 from the tick Haemaphysalis longicornis in Mie Prefecture, Japan in 2008. In this study, we further investigated a total of 483 H. longicornis ticks (220 adults and 263 nymphs) collected from the Mie Prefecture by PCR targeting p44/msp2 to characterize the p44/msp2 multigene family of A. phagocytophilum. Six of the 483 ticks tested were PCR-positive for A. phagocytophilum p44/msp2, and these positive individuals were at the nymph stage of the tick life cycle. Cloning, sequencing, and phylogenetic analyses of the amplicons revealed that the 11 p44/msp2 clones obtained from the positive ticks shared a 54.9%-99.3% amino acid sequence similarity with the 27 previously identified clones from HGA patients in Japan. In particular, 6 p44/msp2 clones displayed the highest similarities (97.2%-99.3%) with 3 previously identified clones (FJ417343, FJ417345, FJ417357). Thus, the data from this study provide important public health information regarding A. phagocytophilum infection transmitted by H. longicornis ticks, especially at the nymph stage.

Equine Granulocytic Anaplasmosis 28 years later

Equine granulocytic anaplasmosis (EGA) is an important tick borne disease of equines that is caused by Anaplasma phagocytophilum (A. phagocytophilum). The etiological agent has veterinary as well as public health importance because of its zoonotic nature. A. phagocytophilum causes an acute illness in equines with loss of appetite, lethargy, hemorrhages and lameness. Clinically, EGA is diagnosed upon examination of morulae within neutrophils especially granulocytes in the blood. The best diagnostic tool for the detection of EGA is Polymerase chain reaction (PCR). Previous studies suggested that EGA is a self-limiting disease and tetracycline therapy is considered as a best treatment regimen. There is no comprehensive summary on the occurrence and distribution of the infection at global level. Therefore, we intended to provide a comprehensive summary on the prevalence and epidemiology of EGA in different areas of the world. It includes mapping the global distribution of EGA in different areas of the world to identify the endemic regions which may be a source of potential disease outbreak. For this purpose, the published data from 1990 to 2018 on EGA was reviewed and collected by electronic literature search of five databases including Google, Google Scholar, Science Direct, PubMed and Web of Science.

Anaplasma species of veterinary importance in Japan

Anaplasma species of the family Anaplasmataceae, order Rickettsiales are tick-borne organisms that can cause disease in animals and humans. In Japan, all recognized species of Anaplasma (except for Anaplasma ovis) and a potentially novel Anaplasma sp. closely related to Anaplasma phagocytophilum have been reported. Most of these detected tick-borne pathogens are believed to be lowly pathogenic in animals in Japan although the zoonotic A. phagocytophilum has recently been reported to cause clinical signs in a dog and in humans. This review documents the studies and reports about Anaplasma spp. in Japan.

Alpha proteobacteria of genusAnaplasma(Rickettsiales: Anaplasmataceae): Epidemiology and characteristics ofAnaplasmaspecies related to veterinary and public health importance

TheAnaplasmaspecies are important globally distributed tick-transmitted bacteria of veterinary and public health importance. These pathogens, cause anaplasmosis in domestic and wild animal species including humans.Rhipicephalus, Ixodes, DermacentorandAmblyommagenera of ticks are the important vectors ofAnaplasma.Acute anaplasmosis is usually diagnosed upon blood smear examination followed by antibodies and nucleic acid detection. All age groups are susceptible but prevalence increases with age. Serological cross-reactivity is one of the important issues amongAnaplasmaspecies. They co-exist and concurrent infections occur in animals and ticks in same geographic area. These are closely related bacteria and share various common attributes which should be considered while developing vaccines and diagnostic assays. Movement of susceptible animals from non-endemic to endemic regions is the major risk factor of bovine/ovine anaplasmosis and tick-borne fever. Tetracyclines are currently available drugs for clearance of infection and treatment in humans and animals. Worldwide vaccine is not yet available. Identification, elimination of reservoirs, vector control (chemical and biological), endemic stability, habitat modification, rearing of tick resistant breeds, chemotherapy and tick vaccination are major control measures of animal anaplasmosis. Identification of reservoirs and minimizing the high-risk tick exposure activities are important control strategies for human granulocytic anaplasmosis.

Anaplasma marginale and Anaplasma phagocytophilum: Rickettsiales pathogens of veterinary and public health significance

Anaplasma marginale and Anaplasma phagocytophilum are the most important tick-borne bacteria of veterinary and public health significance in the family Anaplasmataceae. The objective of current review is to provide knowledge on ecology and epidemiology of A. phagocytophilum and compare major similarities and differences of A. marginale and A. phagocytophilum. Bovine anaplasmosis is globally distributed tick-borne disease of livestock with great economic importance in cattle industry. A. phagocytophilum, a cosmopolitan zoonotic tick transmitted pathogen of wide mammalian hosts. The infection in domestic animals is generally referred as tick-borne fever. Concurrent infections exist in ticks, domestic and wild animals in same geographic area. All age groups are susceptible, but the prevalence increases with age. Movement of susceptible domestic animals from tick free non-endemic regions to disease endemic regions is the major risk factor of bovine anaplasmosis and tick-borne fever. Recreational activities or any other high-risk tick exposure habits as well as blood transfusion are important risk factors of human granulocytic anaplasmosis. After infection, individuals remain life-long carriers. Clinical anaplasmosis is usually diagnosed upon examination of stained blood smears. Generally, detection of serum antibodies followed by molecular diagnosis is usually recommended. There are problems of sensitivity and cross-reactivity with both the Anaplasma species during serological tests. Tetracyclines are the drugs of choice for treatment and elimination of anaplasmosis in animals and humans. Universal vaccine is not available for either A. marginale or A. phagocytophilum, effective against geographically diverse strains. Major control measures for bovine anaplasmosis and tick-borne fever include rearing of tick-resistant breeds, endemic stability, breeding Anaplasma-free herds, identification of regional vectors, domestic/wild reservoirs and control, habitat modification, biological control, chemotherapy, and vaccinations (anaplasmosis and/or tick vaccination). Minimizing the tick exposure activities, identification and control of reservoirs are important control measures for human granulocytic anaplasmosis.

Investigation of tick-borne bacteria (Rickettsia spp., Anaplasma spp., Ehrlichia spp. and Borrelia spp.) in ticks collected from Andean tapirs, cattle and vegetation from a protected area in Ecuador

Background

Ixodid ticks play an important role in the transmission and ecology of infectious diseases. Information about the circulation of tick-borne bacteria in ticks is lacking in Ecuador. Our aims were to investigate the tick species that parasitize Andean tapirs and cattle, and those present in the vegetation from the buffer zone of the Antisana Ecological Reserve and Cayambe-Coca National Park (Ecuador), and to investigate the presence of tick-borne bacteria.

Methods

Tick species were identified based on morphologic and genetic criteria. Detection of tick-borne bacteria belonging to Rickettsia, Anaplasma, Ehrlichia and Borrelia genera was performed by PCRs.

Results

Our ticks included 91 Amblyomma multipunctum, 4 Amblyomma spp., 60 Rhipicephalus microplus, 5 Ixodes spp. and 1 Ixodes boliviensis. A potential Candidatus Rickettsia species closest to Rickettsia monacensis and Rickettsia tamurae (designated Rickettsia sp. 12G1) was detected in 3 R. microplus (3/57, 5.3%). In addition, Anaplasma spp., assigned at least to Anaplasma phagocytophilum (or closely related genotypes) and Anaplasma marginale, were found in 2 A. multipunctum (2/87, 2.3%) and 13 R. microplus (13/57, 22.8%).

Conclusions

This is the first description of Rickettsia sp. in ticks from Ecuador, and the analyses of sequences suggest the presence of a potential novel Rickettsia species. Ecuadorian ticks from Andear tapirs, cattle and vegetation belonging to Amblyomma and Rhipicephalus genera were infected with Anaplasmataceae. Ehrlichia spp. and Borrelia burgdorferi sensu lato were not found in any ticks.

Reprolysin metalloproteases from Ixodes persulcatus, Rhipicephalus sanguineus and Rhipicephalus microplus ticks

Metalloproteases (MPs) have been considered essential for blood feeding and other physiological functions in several hematophagous animals, including ticks. We report the characterization of MP sequences of three important ticks from Asia, Africa and America: Ixodes persulcatus (Ip-MPs), Rhipicephalus sanguineus (Rs-MPs) and R. microplus (BrRm-MPs). Amino acid sequence identity between R. microplus and R. sanguineus MPs ranged from 76 to 100 %, and identities among I. persulcatus, I. ricinus and I. scapularis MP sequences ranged from 88 to 97 %. This high sequence identity and typical functional motifs show that all sequences are MPs. The presence of a zinc binding site, a Met-turn and cysteine rich domain at the C-terminal region indicates that these proteins belong to the reproplysin family of MPs. Differences in amino acid sequences of BrRm-MP1, BrRm-MP2, BrRm-MP4 and BrRm-MP5 (from Porto Alegre strain ticks) were 6, 2, 7 and 5 %, respectively, when compared with sequences deposited in GenBank for the same genes from other R. microplus isolates. Analyses of MPs predicted that they have various highly antigenic regions. Semi-quantitative RT-PCR analysis revealed the presence of transcripts in salivary glands of partially and fully fed female ticks. None of these transcripts were observed in males (except BrRm-MP4) and eggs. These enzymes may be functional components required during tick feeding to manipulate host defenses and support tick hematophagy.

Molecular characterization of Msp2/P44 of Anaplasma phagocytophilum isolated from infected patients and Haemaphysalis longicornis in Laizhou Bay, Shandong Province, China

Molecular characterization of the MSP2/P44 protein of Anaplasma phagocytophilum may determine not only if the bacterium is capable of invading hosts but also whether it generates antigenic variation for the purpose of escaping the host immune response, resulting in various pathologic injuries and serious clinical outcomes. Chinese anaplasmosis patients usually present with serious manifestations, and the fatality rate is as high as 26.5%. In this study, we amplified, cloned and sequenced the msp2/p44 genes of three Chinese A. phagocytophilum isolates from Laizhou Bay, Shandong Province, where human granulocytic anaplasmosis (HGA) patients present severe clinical manifestations, and analyzed their genetic characterization and structural features. We also compared them with the HZ and Webster A. phagocytophilum strains. The sequences for both strains are available in GenBank. Analyses indicated that Chinese A. phagocytophilum isolates were significantly different from the HZ and Webster strains in terms of nucleotide sequences, amino acid sequences and protein secondary and tertiary structures. Moreover, the number of immunologic B-cell epitopes (19) of the MSP2 protein of the Chinese isolates was higher than that of the A. phagocytophilum strains HZ (16) and Webster (9). This genetic diversity of the MSP2/P44 protein of Chinese A. phagocytophilum isolates might be relevant and might have serious clinical outcomes. This observation could provide a clue to further understand the pathogenesis of Chinese A. phagocytophilum.

Anaplasma phagocytophilum--a widespread multi-host pathogen with highly adaptive strategies

The bacterium Anaplasma phagocytophilum has for decades been known to cause the disease tick-borne fever (TBF) in domestic ruminants in Ixodes ricinus-infested areas in northern Europe. In recent years, the bacterium has been found associated with Ixodes-tick species more or less worldwide on the northern hemisphere. A. phagocytophilum has a broad host range and may cause severe disease in several mammalian species, including humans. However, the clinical symptoms vary from subclinical to fatal conditions, and considerable underreporting of clinical incidents is suspected in both human and veterinary medicine. Several variants of A. phagocytophilum have been genetically characterized. Identification and stratification into phylogenetic subfamilies has been based on cell culturing, experimental infections, PCR, and sequencing techniques. However, few genome sequences have been completed so far, thus observations on biological, ecological, and pathological differences between genotypes of the bacterium, have yet to be elucidated by molecular and experimental infection studies. The natural transmission cycles of various A. phagocytophilum variants, the involvement of their respective hosts and vectors involved, in particular the zoonotic potential, have to be unraveled. A. phagocytophilum is able to persist between seasons of tick activity in several mammalian species and movement of hosts and infected ticks on migrating animals or birds may spread the bacterium. In the present review, we focus on the ecology and epidemiology of A. phagocytophilum, especially the role of wildlife in contribution to the spread and sustainability of the infection in domestic livestock and humans.

Human granulocytic Anaplasmosis, Japan

We retrospectively confirmed 2 cases of human Anaplasma phagocytophilum infection. Patient blood samples contained unique p44/msp2 for the pathogen, and antibodies bound to A. phagocytophilum antigens propagated in THP-1 rather than HL60 cells. Unless both cell lines are used for serodiagnosis of rickettsiosis-like infections, cases of human granulocytic anaplasmosis could go undetected.

Specific molecular detection of Anaplasma sp. closely related to Anaplasma phagocytophilum in ixodid ticks and cattle in a pastureland in Hokkaido, Japan

Recent molecular analyses of the Anaplasma sp. closely related to Anaplasma phagocytophilum (previously believed to be A. phagocytophilum) in Japan have clarified its distinct phylogenetic position. PCR methods relying on 16S rRNA- and P44/MSP2-based primers designed to detect this species have low sensitivity and specificity. In this study, a highly sensitive and specific nested PCR method using newly designed primers based on heat-shock operon gene (groEL) was developed to detect this species. The method was later used in an epidemiological study testing DNA samples from 85 Ixodid ticks (collected by flagging) and 50 cattle from the same pastureland in Nakaosobetsu, Hokkaido, Japan. Results revealed prevalence rates of 2.4% (2 of 85) in ticks and 2% (1 of 50) in cattle. The present study also reported the first molecular detection of the Anaplasma sp. closely related to A. phagocytophilum in Japan in H. douglasii, and established a new reliable PCR method that detects this Anaplasma sp. closely related to A. phagocytophilum in Japan.

Dual presence of Anaplasma phagocytophilum and its closely related Anaplasma sp. in ixodid ticks in Hokkaido, Japan, and their specific molecular detection

Anaplasma phagocytophilum causes human granulocytic anaplasmosis (HGA) and tick-borne fever in ruminants. A closely related and potentially novel Anaplasma sp. in Japan was recently characterized. The aims of the study were to provide molecular evidence for the presence of these 2 species in Japan, and to develop a reliable PCR method based on the nucleotide differences within the citrate synthase (gltA) gene. DNA samples from 182 ixodid ticks (134 Ixodes persulcatus, 35 Haemaphysalis douglasii and 13 I. ovatus) collected from 2 sites in Hokkaido, Japan, were screened for A. phagocytophilum and its closely related Anaplasma sp. (herein designated as Anaplasma sp. Japan) using 16S rRNA PCR, revealing a combined prevalence rate of 27.5% (50 samples). The positive samples were then used to evaluate a newly developed gltA-based nested PCR method. Selected positive samples were further characterized using the groEL gene for confirmation and phylogenetic analyses. Two groups of sequence results were obtained: those that had closer identities with (1) A. phagocytophilum (99.5-99.6% for 16S rRNA, 97.5% for gltA and 98.4% for groEL), and those that had closer identities with (2) Anaplasma sp. closely related to A. phagocytophilum in Japan (99.3% for 16S rRNA, 96.4-98.7% for gltA and 97.5-97.9% for groEL). The present study confirmed the distinct presence of A. phagocytophilum and its closely related Anaplasma sp. in Japan, and developed a new PCR detection method based on gltA that can distinguish the 2 organisms.

Mechanisms of obligatory intracellular infection with Anaplasma phagocytophilum

Anaplasma phagocytophilum persists in nature by cycling between mammals and ticks. Human infection by the bite of an infected tick leads to a potentially fatal emerging disease called human granulocytic anaplasmosis. A. phagocytophilum is an obligatory intracellular bacterium that replicates inside mammalian granulocytes and the salivary gland and midgut cells of ticks. A. phagocytophilum evolved the remarkable ability to hijack the regulatory system of host cells. A. phagocytophilum alters vesicular traffic to create an intracellular membrane-bound compartment that allows replication in seclusion from lysosomes. The bacterium downregulates or actively inhibits a number of innate immune responses of mammalian host cells, and it upregulates cellular cholesterol uptake to acquire cholesterol for survival. It also upregulates several genes critical for the infection of ticks, and it prolongs tick survival at freezing temperatures. Several host factors that exacerbate infection have been identified, including interleukin-8 (IL-8) and cholesterol. Host factors that overcome infection include IL-12 and gamma interferon (IFN-γ). Two bacterial type IV secretion effectors and several bacterial proteins that associate with inclusion membranes have been identified. An understanding of the molecular mechanisms underlying A. phagocytophilum infection will foster the development of creative ideas to prevent or treat this emerging tick-borne disease.

Molecular identification and expression analysis of lipocalins from blood feeding taiga tick, Ixodes persulcatus Schulze

Lipocalins have been known for their several biological activities in blood-sucking arthropods. Recently, the identification and characterization of lipocalins from Ixodes ricinus (LIRs) have been reported and functions of lipocalins are well documented. In this study, we have characterized four Ixodes persulcatus lipocalins that were discovered while analyzing I. persulcatus tick salivary gland EST library. We show that the four I. persulcatus lipocalins, here after named LIPERs (lipocalin from I. persulcatus) are 28.8-94.4% identical to LIRs from I. ricinus. Reverse transcriptase-PCR analysis revealed that lipocalin genes were expressed specifically in the salivary glands throughout life cycle stages of the ticks and were up-regulated by blood feeding. The specific expressions were also confirmed by Western blotting analysis. Furthermore, to investigate whether native lipocalins are secreted into the host during tick feeding, the reactivity of anti-serum raised against saliva of adult ticks to recombinant lipocalins was tested by Western blotting. The lipocalins are potentially secreted into the host during tick feeding as revealed by specific reactivity of recombinant lipocalins with mouse antibodies to I. persulcatus tick saliva. Preliminary vaccination of mice with recombinant lipocalins elicited that period to reach engorgement was significantly delayed and the engorgement weight was significantly reduced as compared to the control. Further elucidation of the biological functions of LIPERs are required to fully understand the pathways involved in the modulation of host immune responses.

A towards-multidimensional screening approach to predict candidate genes of rheumatoid arthritis based on SNP, structural and functional annotations

BACKGROUND

According to the Genetic Analysis Workshops (GAW), hundreds of thousands of SNPs have been tested for association with rheumatoid arthritis. Traditional genome-wide association studies (GWAS) have been developed to identify susceptibility genes using a "most significant SNPs/genes" model. However, many minor- or modest-risk genes are likely to be missed after adjustment of multiple testing. This screening process uses a strict selection of statistical thresholds that aim to identify susceptibility genes based only on statistical model, without considering multi-dimensional biological similarities in sequence arrangement, crystal structure, or functional categories/biological pathways between candidate and known disease genes.

METHODS

Multidimensional screening approaches combined with traditional statistical genetics methods can consider multiple biological backgrounds of genetic mutation, structural, and functional annotations. Here we introduce a newly developed multidimensional screening approach for rheumatoid arthritis candidate genes that considers all SNPs with nominal evidence of Bayesian association (BFLn > 0), and structural and functional similarities of corresponding genes or proteins.

RESULTS

Our multidimensional screening approach extracted all risk genes (BFLn > 0) by odd ratios of hypothesis H1 to H0, and determined whether a particular group of genes shared underlying biological similarities with known disease genes. Using this method, we found 6614 risk SNPs in our Bayesian screen result set. Finally, we identified 146 likely causal genes for rheumatoid arthritis, including CD4, FGFR1, and KDR, which have been reported as high risk factors by recent studies. We must denote that 790 (96.1%) of genes identified by GWAS could not easily be classified into related functional categories or biological processes associated with the disease, while our candidate genes shared underlying biological similarities (e.g. were in the same pathway or GO term) and contributed to disease etiology, but where common variations in each of these genes make modest contributions to disease risk. We also found 6141 risk SNPs that were too minor to be detected by conventional approaches, and associations between 58 candidate genes and rheumatoid arthritis were verified by literature retrieved from the NCBI PubMed module.

CONCLUSIONS

Our proposed approach to the analysis of GAW16 data for rheumatoid arthritis was based on an underlying biological similarities-based method applied to candidate and known disease genes. Application of our method could identify likely causal candidate disease genes of rheumatoid arthritis, and could yield biological insights that not detected when focusing only on genes that give the strongest evidence by multiple testing. We hope that our proposed method complements the "most significant SNPs/genes" model, and provides additional insights into the pathogenesis of rheumatoid arthritis and other diseases, when searching datasets for hundreds of genetic variances.