Apparent Host Research Articles

Performances of hybrid high-entropy high-Cr cast irons during sliding wear and air-jet solid-particle erosion

The so-called high-entropy alloys have attracted increasing interest. An originally defined high-entropy alloy contains more than five elements without an apparent host element, and each element has its concentration in the range of 5–35%. This concept challenges the conventional principle used in developing alloys. High-entropy alloys are usually nanostructured and show high strength, excellent resistance to high-temperature creep, and high resistances to wear. Using this concept, the authors previously modified high-Cr cast irons (HCCIs) by adding mixtures of various carbide-forming elements, and noticed that such tailored HCCIs possessed high sliding wear resistance but performed less impressively when impact force was involved. Based on these observations, we modified the high-entropy concept and tailored a commercial white cast iron as a base alloy, Fe–27Cr–2.5C–0.8Si, by alloying with a small amount of B, V, Nb, and W to form several new alloys or hybrid HCCIs. Hardness and toughness of the alloys were measured. Compared to the base alloy, these alloys showed much higher sliding wear resistances. However, air-jet solid-particle erosion tests showed that the performance of these modified alloys was similar to that of the base alloy during high-speed solid-particle erosion, indicating that high-entropy alloys possess significantly enhanced sliding wear resistance due to elevated hardness but may not be very effective in resisting erosion when impact force is involved, which is limited by their reduced toughness. The advantages and disadvantages of high-entropy alloys are generally discussed.

Species of Mycosphaerellaceae and Teratosphaeriaceae on native Myrtaceae in Uruguay: evidence of fungal host jumps

Mycosphaerella species are well-known causal agents of leaf diseases on many economically and ecologically important plant species. In Uruguay, a relatively large number of Mycosphaerellaceae and Teratosphaeriaceae are found on Eucalyptus, but nothing is known of these fungi on native Myrtaceae. The aim of this study was to identify Mycosphaerellaceae and Teratosphaeriaceae species associated with leaf diseases on native Myrtaceae in Uruguay and to consider whether host jumps by the pathogen from introduced Eucalyptus to native Myrtaceae have occurred. Several native forests throughout the country were surveyed with special attention given to those located close to Eucalyptus plantations. Five species belonging to the Mycosphaerellaceae and Teratosphaeriaceae clades were found on native Myrtaceous trees and three of these had previously been reported on Eucalyptus in Uruguay. Those occurring both on Eucalyptus and native Myrtaceae included Pallidocercospora heimii, Pseudocercospora norchiensis, and Teratosphaeria aurantia. In addition, Mycosphaerella yunnanensis, a species known to occur on Eucalyptus but not previously recorded in Uruguay, was found on leaves of two native Myrtaceous hosts. Because most of these species occur on Eucalyptus in countries other than Uruguay, it appears that they were introduced in this country and have adapted to be able to infect native Myrtaceae. These apparent host jumps have the potential to result in serious disease problems and they should be carefully monitored.

Genetic Predictions of Prion Disease Susceptibility in Carnivore Species Based on Variability of the Prion Gene Coding Region

Mammalian species vary widely in their apparent susceptibility to prion diseases. For example, several felid species developed prion disease (feline spongiform encephalopathy or FSE) during the bovine spongiform encephalopathy (BSE) epidemic in the United Kingdom, whereas no canine BSE cases were detected. Whether either of these or other groups of carnivore species can contract other prion diseases (e.g. chronic wasting disease or CWD) remains an open question. Variation in the host-encoded prion protein (PrPC) largely explains observed disease susceptibility patterns within ruminant species, and may explain interspecies differences in susceptibility as well. We sequenced and compared the open reading frame of the PRNP gene encoding PrPC protein from 609 animal samples comprising 29 species from 22 genera of the Order Carnivora; amongst these samples were 15 FSE cases. Our analysis revealed that FSE cases did not encode an identifiable disease-associated PrP polymorphism. However, all canid PrPs contained aspartic acid or glutamic acid at codon 163 which we propose provides a genetic basis for observed susceptibility differences between canids and felids. Among other carnivores studied, wolverine (Gulo gulo) and pine marten (Martes martes) were the only non-canid species to also express PrP-Asp163, which may impact on their prion diseases susceptibility. Populations of black bear (Ursus americanus) and mountain lion (Puma concolor) from Colorado showed little genetic variation in the PrP protein and no variants likely to be highly resistant to prions in general, suggesting that strain differences between BSE and CWD prions also may contribute to the limited apparent host range of the latter.

From Asian curiosity to eruptive American pest: Megacopta cribraria (Hemiptera: Plataspidae) and prospects for its biological control

The kudzu bug or bean plataspid, Megacopta cribraria (Fabricius), is native to Asia where it appears to be widely distributed (although the taxonomy is not entirely clear), but is infrequently a pest of legumes. This bug appeared in 2009 in the southeastern United States, where it is closely associated with kudzu, Pueraria montana Lour. [Merr.] variety lobata [Willd.] Maesen & S. Almeida. However, the insect has become a consistent economic pest of soybeans, Glycine max (L.) Merr., and some other leguminous crops in areas where large numbers can build in kudzu, in addition to being a considerable nuisance in urban landscapes where kudzu occurs. The insect has remarkable capacity for movement and has spread rapidly from nine Georgia counties in 2009 to seven states in 2012. Despite being a nuisance in urban areas and a crop pest, high populations of the bug also reduce the biomass of kudzu, which is itself a seriously problematic invasive weed, complicating the status of M. cribraria in its expanded range. Extant predators and a pathogen in the US have been observed attacking kudzu bugs in the laboratory and field, but no parasitism of eggs or nymphs has been observed to date. A single record of parasitism of an adult kudzu bug by a tachinid fly is known from the US, but no other adult parasitism has been observed in the US or elsewhere. Extant enemies may eventually significantly reduce the bug’s populations, but at present native enemies appear to be insufficient for the task, and exotic enemies from the kudzu bug’s native range may offer the best possibility for effective biological control in the US. Based on the available literature, the best option for an importation biological control program appears to be the platygastrid egg parasitoid Paratelenomus saccharalis (Dodd) because of its apparent host specificity, intimate biological linkages with M. cribraria, and wide geographic distribution in the Eastern Hemisphere. Other natural enemies may eventually emerge as good candidates for importation, but at present P. saccharalis appears to be the most promising.

Evidence that Cryptosporidium parvum populations are panmictic and unstructured in the Upper Midwest of the United States.

Cryptosporidium parvum is a zoonotic protozoan parasite that causes cryptosporidiosis, an infectious diarrheal disease primarily affecting humans and neonatal ruminants. Understanding the transmission dynamics of C. parvum, particularly the specific contributions of zoonotic and anthroponotic transmission, is critical to the control of this pathogen. This study used a population genetics approach to better understand the transmission of C. parvum in the Upper Midwest United States. A total of 254 C. parvum isolates from cases of human cryptosporidiosis in Minnesota and Wisconsin and diarrheic calves in Minnesota, Wisconsin, and North Dakota were genotyped at eight polymorphic loci. Isolates with a complete profile from all eight loci (n = 212) were used to derive a multilocus genotype (MLT), which was used in population genetic analyses. Among the 94 MLTs identified, 60 were represented by a single isolate. Approximately 20% of isolates belonged to MLT 2, a group that included both human and cattle isolates. Population analyses revealed a predominantly panmictic population with no apparent geographic or host substructuring.

Taxonomy of two host specialized Phakopsora populations on Meliosma in Japan

Phakopsora meliosmae, a macrocyclic autoecious rust fungus, is reported to occur on several Meliosma species widely distributed in Asia. Despite the apparent broad host range, a recent molecular phylogenetic study indicated that two rust populations on Meliosma myriantha and Meliosma tenuis respectively in Japan were biologically distinct. To clarify the biological and taxonomic relationships of these populations, cross inoculations and comparative morphological examinations were carried out. Cross inoculations using basidiospores and aeciospores confirmed the macrocyclic, autoecious nature of the life cycle in both rust populations and showed that the two populations were distinct in their host specificity. Furthermore, they were found to be distinct in the structure of the aecial peridium surface, the size and wall thickness of uredinial paraphyses, and the urediniospore size and shape. Consequently, the fungal population on M. tenuis is taxonomically separated from P. meliosmae originally proposed for the fungus on M. myriantha. A new name, Phakopsora orientalis, is proposed for the fungus on M. tenuis.

Host-parasite associations and host-specificity in haemoparasites of reed bed passerines

The host specificity and host sharing of avian haemoparasites (genera Haemoproteus and Plasmodium) is still poorly known, although they infect a large proportion of several studied bird populations. This study used molecular techniques to detect haemoparasites in marsh warblers and in other passerines that feed in reed beds, at 4 sites in Portugal. The host-specificity of the parasite lineages was analysed and compared with other cases described in the literature to assess whether apparent host specificity changes according to the studied system. Nine lineages of Haemoproteus and 15 of Plasmodium were found, of which only 10 Plasmodium were proven to have local transmission. Each lineage was confined to a distinct set of host species. The distribution of parasites in the host species was non-nested, meaning that specialist lineages did not always share hosts with generalists. The most prevalent lineages were those with a wider host range, indicating that the ability to infect more hosts will enhance a parasite's prevalence in its entire host range. We also found that in our areas, a specialist parasite (H. MW1) appears to have a more generalist character than described in the literature, suggesting that a parasite's apparent specialization can depend on the type of host species sampled.

Preparing for the Arthropocalypse

In May, 2011, the normally staid Centers for Disease Control and Prevention issued detailed instructions for surviving a zombie apocalypse: http://tinyurl. com/66ojena. The post, written by Assistant Surgeon General Ali Khan, outlined the steps to be taken in the event of an outbreak of “flesh-eating zombies,” which included, among other things, assembling an emergency preparedness kit that includes first aid supplies, a battery-powered radio, and, of course, duct tape. The instructions were part of a tongue-in-cheek campaign inspired by inquiries to the agency about whether radiation in the wake of the Fukushima tsunami and nuclear reactor disaster might spawn a zombie outbreak (inasmuch as radiation is supposed to cause zombification, along with viruses, black magic, “zombie powder,” bath salts, and many other things). The CDC officials took advantage of the situation to promote general rules of preparedness for the American public; spokesperson Dave Daigle explained to Fox News that “People are really dialed in on zombies” (http:// tinyurl.com/669tkdj). There’s no denying the zombie Zeitgeist; pop culture seems to be saturated with brain-eating undead. This cultural phenomenon is most conspicuously manifested at the local movie multiplex. An examination of zombie movies through time, made conveniently easy to calculate thanks to the Web site Zombie Zone News (http://tinyurl.com/ cmcjjh4), reveals an unsettling trend. In the two decades between 1932 (the release of White Zombie) and 1952 (when Zombies of the Stratosphere was the only zombierelated release), there were only 15 zombie movies. From 1952 to 1972, that number had risen to 47, and between 1972 and 1992, the number ballooned to 193. Between 1992 and 2010, the number skyrocketed to 473 (in fact, there were 45 in 2010 alone). It’s amazing that there’s room at any multiplex these days for non-zombie movies. Why was I visiting the Zombie Zone News Web site? Because the site offers a link for people to invest in zombie research, (“How much would YOU pay for the information that could save your life when the zombies come? Is a wooden baseball bat really better for skull cracking than aluminum? How effective is a bear trap, a katana, or an axe?”). I stumbled across the site while attempting to document what I perceived to be a conspicuous increase in references to zombies in the scientific literature. I was induced to delve into zombie science by a recent spate of stories about the discovery of an apparent host switch by Apocephalus borealis, a parasitic phorid fly associated primarily with bumble bees, to Apis mellifera, the western honey bee (Core et al. 2012). It’s no surprise to entomologists that phorid fly parasitoids eat brains, but this lifestyle and host shift proved irresistible to science journalists, who gleefully picked up the story, reporting details such as the fact that after infestation, “...the bee starts exhibiting strange behavior and acts, well, like a zombie. It moves in increasingly erratic circles and becomes drawn to bright lights” (http://tinyurl.com/ d2c3236). The scientists who had reported the finding capitalized on zombie-philia by recruiting citizen-scientist “zombie bee hunters” to report incidences of phorid parasitism of honey bees through a Web site called (naturally) zombeewatch.org. Actually, as far as I can tell, the word “zombie” appears only once in Core et al. (2012): in the bibliography, in the title of an article about Pseudacteon tricuspis, a phorid parasite of fire ants (Solenopsis invicta) (Henne and Johnson 2007). But make no mistake—zombie references are increasing exponentially in the scientific literature. From 1973, when Legaultd (1973) published a paper titled “Zombie bacteria,” the annual count of papers with “zombie” in the title climbed to 38 in 2011, and the trend does not seem to be abating. The most frequently cited zombie science paper (n = 39) belongs to Foster et al. (2000) and is titled “Do hornets have zombie workers?” The authors describe the absence of worker oviposition despite the lack of queen aggression or oophagy (raising the possibility that Vespa crabro queens “exert indirect pheromonal control to cause the worker’s acquiescent zombie-like behaviour”). Although the authors reported “workers mauling each other,” no brain-eating (a seemingly defining zombie characteristic) was observed. Zombies are not the only undead capturing attention of late; vampires have gained a lot of traction in recent years. Yes, there’s a Web site, Vampire Rave (http://tinyurl. com/6hl7mba), that indexes 682 vampire movies (including, most recently, the wildly successful Twilight franchise). A cursory review of the site reveals that pop culture today is awash in bloodsucking creatures of the night (particularly primetime hours, The Zom-bees Survival Kit

Iron Deprivation Suppresses Hepatocellular Carcinoma Growth in Experimental Studies

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related death, and iron overload is a significant risk factor in the development of HCC. In this study, we investigated the potential application of depriving iron by a novel iron chelator, thiosemicarbazone-24 (TSC24), in HCC treatment. Two HCC cell lines and HFE knockout (HFE(-/-)) mice were used to determine iron chelation efficiency of TSC24. The anticancer effects of TSC24 on HCC were analyzed in vitro and in athymic xenograft mouse models. Treatment with TSC24 significantly decreased the cellular iron concentration in hepatoma cells and the serum iron concentration in HFE(-/-) mice by blocking iron uptake and interfering with normal regulation of iron levels. Moreover, the viability of HCC cell lines was reduced by TSC24. Confirming the mechanism of the agent, this decrease in viability could be partially rescued by addition of exogenous iron. TSC24 also suppressed tumor growth in athymic mice bearing human HCC xenografts in a concentration-dependent manner, without apparent toxicity in parallel with a decrease in the serum iron level. Further studies revealed that TSC24 efficiently triggered cell-cycle arrest and apoptosis in Hep3B and HepG2 cell lines. TSC24 is a potent iron chelator that suppresses human HCC tumor growth by disrupting iron homeostasis, reducing available iron, and triggering cell-cycle arrest and apoptosis, without apparent host toxicity at effective doses. Thus, TSC24 shows great potential for the treatment of HCC.

Cortinarius callimorphus, a new species from northern California

Described is Cortinarius callimorphus, a new species in subgenus Phlegmacium from the coastal woods of northern California, with Sitka spruce to its apparent primary host associate. Cortinarius callimorphus, which resembles other members of sect. Multiformes , stands out because of its citriform spores. Its closest known relative is C. polymorphus from Europe.

Suboptimal Activation of Antigen-Specific CD4+ Effector Cells Enables Persistence of M. tuberculosis In Vivo

Adaptive immunity to Mycobacterium tuberculosis controls progressive bacterial growth and disease but does not eradicate infection. Among CD4+ T cells in the lungs of M. tuberculosis-infected mice, we observed that few produced IFN-γ without ex vivo restimulation. Therefore, we hypothesized that one mechanism whereby M. tuberculosis avoids elimination is by limiting activation of CD4+ effector T cells at the site of infection in the lungs. To test this hypothesis, we adoptively transferred Th1-polarized CD4+ effector T cells specific for M. tuberculosis Ag85B peptide 25 (P25TCRTh1 cells), which trafficked to the lungs of infected mice and exhibited antigen-dependent IFN-γ production. During the early phase of infection, ∼10% of P25TCRTh1 cells produced IFN-γ in vivo; this declined to <1% as infection progressed to chronic phase. Bacterial downregulation of fbpB (encoding Ag85B) contributed to the decrease in effector T cell activation in the lungs, as a strain of M. tuberculosis engineered to express fbpB in the chronic phase stimulated P25TCRTh1 effector cells at higher frequencies in vivo, and this resulted in CD4+ T cell-dependent reduction of lung bacterial burdens and prolonged survival of mice. Administration of synthetic peptide 25 alone also increased activation of endogenous antigen-specific effector cells and reduced the bacterial burden in the lungs without apparent host toxicity. These results indicate that CD4+ effector T cells are activated at suboptimal frequencies in tuberculosis, and that increasing effector T cell activation in the lungs by providing one or more epitope peptides may be a successful strategy for TB therapy.

Phylogenomics and molecular evolution of foot-and-mouth disease virus.

This report describes the use of Bayesian methods to analyze polyprotein coding region sequences (n = 217) obtained from GenBank to define the genome-wide phylogeny of foot and mouth disease virus (FMDV). The results strongly supported the monophyly of five FMDV serotypes, O, A, Asia 1, C, and SAT 3, while sequences for the two remaining FMDV serotypes, SAT 1 and SAT 2 did not separate into entirely distinct clades. The phylogenomic tree revealed three sister-group relationships, serotype O + Asia 1, A + C, and SAT 1 + 3 + 2, with a new branching pattern: {[(O, Asia 1), (A, C)], (SAT 1, 2, 3)}. Within each serotype, there was no apparent periodic, geographic, or host species influence on the evolution of global FMDVs. Analysis of the polyprotein coding region of these sequences provided evidence for the influence of purifying selection on the evolution of FMDV. Using a Bayesian coalescent approach, the evolutionary rate of FMDV isolates that circulated during the years 1932-2007 was estimated to be 1.46 × 10(-3) substitutions/site/year, and the most recent common ancestor of the virus existed approximately 481 years ago. Bayesian skyline plot revealed a population expansion in the early 20(th) century that was followed by a rapid decline in population size from the late 20(th) century to the present day. These findings provide new insights into the mechanisms that impact on the evolution of this important livestock pathogen.

The mouse "xenotropic" gammaretroviruses and their XPR1 receptor

The xenotropic/polytropic subgroup of mouse leukemia viruses (MLVs) all rely on the XPR1 receptor for entry, but these viruses vary in tropism, distribution among wild and laboratory mice, pathogenicity, strategies used for transmission, and sensitivity to host restriction factors. Most, but not all, isolates have typical xenotropic or polytropic host range, and these two MLV tropism types have now been detected in humans as viral sequences or as infectious virus, termed XMRV, or xenotropic murine leukemia virus-related virus. The mouse xenotropic MLVs (X-MLVs) were originally defined by their inability to infect cells of their natural mouse hosts. It is now clear, however, that X-MLVs actually have the broadest host range of the MLVs. Nearly all nonrodent mammals are susceptible to X-MLVs, and all species of wild mice and several common strains of laboratory mice are X-MLV susceptible. The polytropic MLVs, named for their apparent broad host range, show a more limited host range than the X-MLVs in that they fail to infect cells of many mouse species as well as many nonrodent mammals. The co-evolution of these viruses with their receptor and other host factors that affect their replication has produced a heterogeneous group of viruses capable of inducing various diseases, as well as endogenized viral genomes, some of which have been domesticated by their hosts to serve in antiviral defense.

Detection of multiple Bartonella species in digestive and reproductive tissues of fleas collected from sympatric mammals

At least 12 species in the genus Bartonella are zoonotic pathogens that may be transmitted among mammalian hosts by fleas or other arthropods. Apparent host specificity by some Bartonella species to mammalian hosts has been observed, and the detection of multiple Bartonella species in mammalian fleas suggests that fleas take bloodmeals from a variety of host species. However, many flea species are observed to parasitize a narrow host range. Therefore, we suspect that fleas may acquire Bartonella by a mechanism other than ingesting infectious blood. We found that detection of multiple Bartonella genotypes and species is apparently common in fleas and that the majority of fleas tested (5/9) carried Bartonella species atypical of their hosts. We also detected Bartonella DNA in flea reproductive tissues, suggesting that vertical transmission of this organism in vectors is possible, potentially leading to the accumulation of Bartonella diversity over time within fleas.

Autologous Human T Cells and Allogeneic Antigen-Presenting Cells Permit Effective Adoptive Transfer of B-CLL Cells Into Immune Deficient Mice.

Abstract 2326Poster Board II-303B-cell type chronic lymphocytic leukemia (B-CLL), an incurable disease of unknown etiology, results from the clonal expansion of a CD5+CD19+ B lymphocyte. Progress into defining the cell of origin of the disease and identifying a stem cell reservoir has been impeded because of the lack of a reproducible model for growing B-CLL cells in vivo. At least one possible cause for this is the murine microenvironment's inability to support B-CLL survival and proliferation. To overcome this barrier, we reconstituted NOD/SCID/γnull mice by intrabone (ib) or intravenous (iv) injection of 1 × 105 CD34+ cord blood cells along with ∼106 bone marrow-derived human mesenchymal stem cells (hMSCs) by ib injection. After human cellular engraftment, a total of 108 CFSE-labeled PBMCs from individual B-CLL patients were injected into the same bones or iv. Every two weeks thereafter, blood from the mice was examined for the presence of cells bearing CFSE, human CD45, and various human lineage markers by flow cytometry. In the presence of a human hematopoietic microenvironment derived from hHSCs, CFSE+CD5+CD19+ cells were readily detected in the blood of mice and many of these leukemic cells underwent at least 6 cell doublings. In contrast, the numbers of leukemic cells circulating in the blood of mice reconstituted with hMSCs without CD34+ cells was much less and these failed to proliferate. Thus, hMSCs were not essential in the model. Moreover, the percentage of leukemic cells expressing CD38 in the CFSE+CD5+CD19+ cell fraction was similar to that in the donor patient inoculum only in the mice in which B-CLL cell proliferation occurred. The percentage and intensity of CD38-expressing B-CLL cells was higher in the spleen and bone marrow (BM), far exceeding that in the blood and peritoneum. Of note, B-CLL cells formed follicular structures in the spleen that contained larger B cells expressing the same Ig H and Ig L chains as the CLL MNCs. CLL cells from these spleens exhibited the same IGHV/D/J rearrangement as in the donor leukemic cells, indicating their leukemic origin. These follicular structures are reminiscent of proliferation centers/pseudofollicles seen in patient lymph nodes and BM, in that they contained leukemic B cells of intermediate and large size. Finally, B-CLL cells adoptively transferred into these mice exhibit kinetics similar to those observed in patients in vivo, with birth rates calculated from CFSE-dilution data of (X-Y% per day). Robust T-cell expansion occurred in mice receiving CD34+ cells and occasionally in mice (10-20%) not receiving hCD34+ cells. Based on detailed SNP analyses, the expanded T cells were of B-CLL patient origin and not from hCD34+ cells. Notably when T cells were eliminated by injecting an anti-CD3 mAb (OKT3), B-CLL cell proliferation was inhibited. These latter two findings clearly indicate a need for autologous T lymphocytes in the successful adoptive transfer of B-CLL cells in this model and also highlight the fact that another cell type, derived from the normal allogeneic CD34+ cells, is needed. Because CD34+ cells could be substituted for by mature allogeneic monocytes or B lymphocytes from the blood of normal individuals, antigen-presenting cells may be the key cells that develop from the normal hHSCs. This would suggest that an allogeneic mixed lymphocyte reaction is needed for successful B-CLL cell survival and proliferation. This is consistent with finding that most of the mice with significant T-cell overexpansion died within 6 weeks of B-CLL cell injection from apparent graft vs. host disease. Finally, preliminary data using Rituxan (anti-CD20 mAb) to eliminate B-CLL cells from recipient mice suggest that this model is a good tool to perform pre-clinical studies on the efficacy of action of novel therapeutics. In summary, these studies indicate that allogeneic human antigen-presenting cells and autologous human T cells permit adoptive xenogeneic transfer and clonal expansion of B-CLL cells in immune deficient mice. This model will be useful in discovering and understanding non-genetic factors promoting B-CLL expansion because it recapitulates several features of human B-CLL. Finally, the model may help in the study of the basic biology of this disease, such as if leukemic stem cells exist, and also in conducting pre-clinical tests on possible new therapeutics. Disclosures:No relevant conflicts of interest to declare.

Human leukocyte antigen‐DRB1*1101 correlates with less severe hepatitis in Taiwanese male carriers of hepatitis B virus

Human leukocyte antigen (HLA) class II molecules are associated with host immune responses against hepatitis B virus infection. Male gender is the apparent host factor when someone encounters with the severity of hepatitis. The aim of this study was to investigate the association of the most polymorphic HLA class II allele, human leukocyte antigen-DRB1, with the severity of hepatitis in male carriers of hepatitis B virus. In this prospective cohort study, a total of 204 carriers of hepatitis B virus (131 men and 73 women) who have been followed-up for more than 1 year at the outpatient clinic of a university hospital were collected consecutively. Fifty carriers of hepatitis B virus (group I) with alanine aminotransferase <2x upper limit of normal (mean follow-up 83.6 months) were compared with 154 chronic hepatitis B patients (group II) with alanine aminotransferase >/=2x upper limit of normal (mean follow-up 81.3 months). Alleles of HLA-DRB1 were typed by the polymerase chain reaction-sequence specific oligonucleotide probe hybridization and genotypes of hepatitis B virus by melting curve analysis. HLA-DRB1*1101 was found in 18% of group I versus 8% of group II in male carriers (OR 0.23, P = 0.020, after adjustment for age) and 4% versus 9.4% in female carriers (P = 0.094). In male carriers harboring DRB1*1101, the distribution of hepatitis B viral genotype was comparable between the two groups. HLA-DRB1*1101 correlates with less severe hepatitis in Taiwanese male carriers of hepatitis B virus.

GENOTYPIC VARIATION AND THE ROLE OF DEFENSIVE ENDOSYMBIONTS IN AN ALL-PARTHENOGENETIC HOST-PARASITOID INTERACTION

Models of host-parasite coevolution predict pronounced genetic dynamics if resistance and infectivity are genotype-specific or associated with costs, and if selection is fueled by sufficient genetic variation. We addressed these assumptions in the black bean aphid, Aphis fabae, and its parasitoid Lysiphlebus fabarum. Parasitoid genotypes differed in infectivity and host clones exhibited huge variation for susceptibility. This variation occurred at two levels. Clones harboring Hamiltonella defensa, a bacterial endosymbiont known to protect pea aphids against parasitoids, enjoyed greatly reduced susceptibility, yet clones without H. defensa also exhibited significant variation. Although there was no evidence for genotype-specificity in the H. defensa-free clones' interaction with parasitoids, we found such evidence in clones containing the bacterium. This suggests that parasitoid genotypes differ in their ability to overcome H. defensa, resulting in an apparent host x parasitoid genotype interaction that may in fact be due to an underlying symbiont x parasitoid genotype interaction. Aphid susceptibility to parasitoids correlated negatively with fecundity and rate of increase, due to H. defensa-bearing clones being more fecund on average. Hence, possessing symbionts may also be favorable in the absence of parasitoids, which raises the question why H. defensa does not go to fixation and highlights the need to develop new models to understand the dynamics of endosymbiont-mediated coevolution.

First report of microsporidiosis in fairy shrimp Branchinella thailandensis (Sanoamuang, Saengphan and Murugan, 2002)

The diagnosis of microsporidia infestation in the muscle of the fairy shrimp ( Branchinella thailandensis [Sanoamuang, L., Saengphan, N., Murugan, G., 2002. First record of the family Thamnocephalidae, (Crustacea, Anostraca) from Southeast Asia and description of a new species of Branchinella. Hydrobiologia 486, 63–69.]) culture was examined by optical microscopy and transmission electron microscopy. The clinical sign of microsporidiosis in fairy shrimp was white tubular masses in the muscle tissue. There was no apparent host encapsulation or xenoma formation within the muscle fibers. Spores of this parasite were uninucleate. The length of the spores was about 2.829–3.269 (3.086) µm and the width was about 1.686–2.857 (1.850) µm. The polar filament had 12–13 coils, arranged in a single row at the posterior end of the spore. Based on the gross pathology, morphology, histopathology and ultrastructure of the spore, we suggest that this parasite is a species of Pleistophora sp. Although this disease was not acute, the fairy shrimp showed continuous mortality. Secondary bacterial infections occurred frequently in infected fairy shrimp. Fairy shrimp died within one to five days of contracting a bacterial infection. Finally, microsporidiosis affected the productivity of the fairy shrimp culture. Prophylaxis was performed by treating underground water that might be contaminated with this microspore before use in culture.

Competitor‐free space mediates non‐target impact of an introduced biological control agent

Abstract 1. Enemy‐free space has been shown to mediate host shifts in herbivores, but this has not previously been documented in parasitoids. Also, natural enemies shown to maintain host shifts have always been from higher trophic levels, rather than competitors.2. In Hawaii, an Australian parasitoid (Diachasmimorpha tryoni) of medflies that loses competition contests to a subsequently introduced Asian parasitoid (Fopius arisanus) has shifted its realised host range to attack non‐target gall flies on lantana.3. The present study demonstrates experimentally that D. tryoni reproduction is: (i) lower on medflies in coffee when F. arisanus is present than when it is absent; (ii) higher in gall flies on lantana than on medflies in coffee, when F. arisanus is present; and (iii) higher in medflies on coffee than in gall flies on lantana, when F. arisanus is absent. This meets Berdegue et al.’s (Ecological Entomology, 21, 203–217, 1996) three conditions to confirm the importance of enemy‐free space.4. In the field, F. arisanus is abundant on medflies, whereas D. tryoni is rare on medflies, but is the dominant parasitoid of lantana gall flies.5. Competitor‐free space is thus shown to be a key mechanism maintaining an apparent host shift by an introduced biocontrol agent onto a non‐target species.

Characterization of 'Candidatus Neoehrlichia lotoris' (family Anaplasmataceae) from raccoons (Procyon lotor)

Recently, a novel ehrlichial organism was isolated from a raccoon (Procyon lotor) and the isolate (RAC413) was infectious to two naïve raccoons but not laboratory mice, rats or rabbits. In this study, amplification and sequencing of four gene targets (16S rRNA gene, groESL, gltA and rpoB) confirmed that the novel ehrlichial organism was a member of the family Anaplasmataceae and was most closely related to, but distinct from, 'Candidatus Neoehrlichia mikurensis' TK4456(R) and IS58. RAC413 shared the highest sequence similarity with members of the genus Ehrlichia (94.2-95.1, 80.9-83.1, 67.9-71.9 and 39.9-40.7 % similarity for the 16S rRNA gene, groESL, gltA and rpoB, respectively). No sequence variation in three sequences (16S rRNA gene, groESL and gltA) was observed between the RAC413 isolate and five additional sequences amplified from blood of naturally infected raccoons from several geographically isolated populations in the south-eastern USA. Serum samples from four experimentally infected raccoons did not react to Ehrlichia canis, Ehrlichia chaffeensis, Anaplasma marginale or Anaplasma phagocytophilum antigens in an immunofluorescence assay or an Ehrlichia ewingii peptide in an ELISA format. On the basis of the distinctive molecular and serological characteristics and apparent host specificity of this ehrlichial organism, it is proposed that this organism be designated 'Candidatus Neoehrlichia lotoris' (reference strain RAC413).