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Results for “host manipulation”

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PubMed2001

A novel technique for removing Wolbachia infections from Aedes albopictus (Diptera: Culicidae).

Intracellular bacteria of the genus Wolbachia often behave as reproductive parasites by manipulating host reproduction to enhance the vertical transmission of infections. Wolbachia infections in Aedes albopictus (Skuse) cause a reproductive manipulation known as cytoplasmic incompatibility, which can reduce brood hatch. Because field populations of Ae. albopictus are naturally infected, studies of Wolbachia-induced effects on Ae. albopictus reproduction and fitness require that Wolbachia be artificially removed. Although simiple techniques for clearing Wolbachia infections from other host insects have been developed, removal of Wolbachia bacteria from Ae. abopictus is difficult. Here we describe an improved method for removing Wolbachia infections Ae. albopictus. This method differs from earlier techniques in that it relies upon the tetracycline treatment of adults instead of larvae. We demonstrate that tetracycline treatment of adult Ae. albopictus can predictably generate uninfected individuals, simplify the procedure required for Wolbachia removal, and reduce the level of inbreeding required to produce uninfected lines.

Aedes↗

PubMed2004

Heads or tails: host-parasite interactions in the Drosophila-Wolbachia system.

Wolbachia strains are endosymbiotic bacteria typically found in the reproductive tracts of arthropods. These bacteria manipulate host reproduction to ensure maternal transmission. They are usually transmitted vertically, so it has been predicted that they have evolved a mechanism to target the host's germ cells during development. Through cytological analysis we found that Wolbachia strains display various affinities for the germ line of Drosophila. Different Wolbachia strains show posterior, anterior, or cortical localization in Drosophila embryos, and this localization is congruent with the classification of the organisms based on the wsp (Wolbachia surface protein) gene sequence. This embryonic distribution pattern is established during early oogenesis and does not change until late stages of embryogenesis. The posterior and anterior localization of Wolbachia resembles that of oskar and bicoid mRNAs, respectively, which define the anterior-posterior axis in the Drosophila oocyte. By comparing the properties of a single Wolbachia strain in different host backgrounds and the properties of different Wolbachia strains in the same host background, we concluded that bacterial factors determine distribution, while bacterial density seems to be limited by the host. Possible implications concerning cytoplasmic incompatibility and evolution of strains are discussed.

Animals↗

PubMed2004

A secreted protein from the human hookworm necator americanus binds selectively to NK cells and induces IFN-gamma production.

Parasitic helminths induce chronic infections in their hosts although, with most human helminthiases, protective immunity gradually develops with age or exposure of the host. One exception is infection with the human hookworm, Necator americanus, where virtually no protection ensues over time. Such observations suggest these parasites have developed unique mechanisms to evade host immunity, leading us to investigate the role of the excretory/secretory (ES) products of adult N. americanus in manipulating host immune responses. Specifically, we found that a protein(s) from ES products of adult N. americanus bound selectively to mouse and human NK cells. Moreover, incubation of purified NK cells with N. americanus ES products stimulated the production of augmented (4- to 30-fold) levels of IFN-gamma. This augmentation was dependent on the presence of both IL-2 and IL-12 and was endotoxin-independent. This is the first report of a pathogen protein that binds exclusively to NK cells and the first report of a nematode-derived product that induces abundant levels of cytokines from NK cells. Such an interaction could provide a means of cross-regulating deleterious Th2 immune responses in the host, thereby contributing to the long-term survival of N. americanus.

Animals↗

PubMed1998

Interaction of viral proteins with host cell death machinery.

In recent years, intense research has been directed towards understanding molecular mechanisms involved in viral pathogenesis. It is now known that many viruses manipulate host defense mechanisms to prevent apoptosis in order to maximize viral replication. Towards the end of their replication cycle, certain viruses direct the synthesis of proteins that induce apoptosis or cell lysis thereby facilitating viral release from the cell. The present review summarizes the current understanding of interactions between viral proteins and the host cell death machinery.

Animals↗

PubMed2004

Decreased diversity but increased substitution rate in host mtDNA as a consequence of Wolbachia endosymbiont infection.

A substantial fraction of insects and other terrestrial arthropods are infected with parasitic, maternally transmitted endosymbiotic bacteria that manipulate host reproduction. In addition to imposing direct selection on the host to resist these effects, endosymbionts may also have indirect effects on the evolution of the mtDNA with which they are cotransmitted. Patterns of mtDNA diversity and evolution were examined in Drosophila recens, which is infected with the endosymbiont Wolbachia, and its uninfected sister species D. subquinaria. The level of mitochondrial, but not nuclear, DNA diversity is much lower in D. recens than in D. subquinaria, consistent with the hypothesized diversity-purging effects of an evolutionarily recent Wolbachia sweep. The d(N)/d(S) ratio in mtDNA is significantly greater in D. recens, suggesting that Muller's ratchet has brought about an increased rate of substitution of slightly deleterious mutations. The data also reveal elevated rates of synonymous substitutions in D. recens, suggesting that these sites may experience weak selection. These findings show that maternally transmitted endosymbionts can severely depress levels of mtDNA diversity within an infected host species, while accelerating the rate of divergence among mtDNA lineages in different species.

Animals↗

PubMed2005

A mouse model for S. typhimurium-induced enterocolitis.

Salmonella typhimurium has emerged as a model pathogen that manipulates host cells in a complex fashion, thus causing disease. In humans, S. typhimurium causes acute intestinal inflammation. Intriguingly, type III secreted virulence proteins have a central role in this process. At the cellular level, the functions of these factors are well characterized; at present, animal models are required for elucidating how these factors trigger inflammatory disease in vivo. Calf infection models have been employed successfully and, recently, a mouse model was identified: in streptomycin-pretreated mice, S. typhimurium causes acute colitis. This mouse model provides a new avenue for research into acute intestinal inflammation because it enables the manipulation and dissection of both the bacterial and host contributions to the disease in unsurpassed detail.

Animals↗

PubMed1999

Wolbachia pipientis: microbial manipulator of arthropod reproduction.

The alpha-proteobacterium Wolbachia pipientis is a very common cytoplasmic symbiont of insects, crustaceans, mites, and filarial nematodes. To enhance its transmission, W. pipientis has evolved a large scale of host manipulations: parthenogenesis induction, feminization, and male killing. W. pipientis's most common effect is a crossing incompatibility between infected males and uninfected females. Little is known about the genetics and biochemistry of these symbionts because of their fastidious requirements. The affinity of W. pipientis for the microtubules associated with the early divisions in eggs may explain some of their effects. Such inherited microorganisms are thought to have been major factors in the evolution of sex determination, eusociality, and speciation. W. pipientis isolates are also of interest as vectors for the modification of wild insect populations, in the improvement of parasitoid wasps in biological pest control, and as a new method for interfering with diseases caused by filarial nematodes.

Animals↗

PubMed2005

Host physiological condition regulates parasitic plant performance: Arceuthobium vaginatum subsp. cryptopodum on Pinus ponderosa.

Much research has focused on effects of plant parasites on host-plant physiology and growth, but little is known about effects of host physiological condition on parasite growth. Using the parasitic dwarf mistletoe Arceuthobium vaginatum subsp. cryptopodum (Viscaceae) and its host Pinus ponderosa, we investigated whether changes in host physiological condition influenced mistletoe shoot development in northern Arizona forests. We conducted two studies in two consecutive years and used forest thinning (i.e., competitive release) to manipulate host physiological condition. We removed dwarf mistletoe shoots in April, before the onset of the growing season, and measured the amount of regrowth in the first season after forest thinning (Study I: n=38 trees; Study II: n=35 trees). Thinning increased tree uptake of water and carbon in both studies, but had no effect on leaf N concentration or delta13C. Mistletoe shoot growth was greater on trees with high uptake of water and carbon in thinned stands than trees with low uptake in unthinned stands. These findings show that increased resource uptake by host trees increases resources to these heterotrophic dwarf mistletoes, and links mistletoe performance to changes in host physiological condition.

Arizona↗

PubMed2003

Variable male potential rate of reproduction: high male mating capacity as an adaptation to parasite-induced excess of females?

Numerous animals are known to harbour intracytoplasmic symbionts that gain transmission to a new host generation via female eggs and not male sperm. Bacteria of the genus Wolbachia are a typical example. They infect a large range of arthropod species and manipulate host reproduction in several ways. In terrestrial isopods (woodlice), Wolbachia are responsible for converting males into females (feminization (F)) in some species, or for infertility in certain host crosses in other species (cytoplasmic incompatibility (CI)). Wolbachia with the F phenotype impose a strong excess of females on their host populations, while Wolbachia expressing CI do not. Here, we test the possibility that male mating capacity (MC) is correlated with Wolbachia-induced phenotype. We show that males of isopod hosts harbouring F Wolbachia possess a strong MC (i.e. are able to mate with several females in a short time), while those of species harbouring CI Wolbachia possess a weaker MC. This pattern may be explained either by the selection of high MC following the increase in female-biased sex ratios, or because the F phenotype would lead to population extinction in species where MC is not sufficiently high. This last hypotheses is nevertheless more constrained by population structure.

Animals↗

PubMed2004

Review: CMV escapes!

Cytomegalovirus (CMV) is an opportunistic pathogen that establishes life-long latent infection without clinical disease in immunocompetent individuals, but can cause severe illness in newborns, transplant recipients, and patients with HIV. CMV has evolved complex molecular mechanisms to avoid host immune detection and destruction. Collectively these mechanisms have been termed "immunoevasion" or "escapology." Perhaps the most essential mechanism of virus survival within the host is latency, a form of reversible nonproductive infection of host cells by replication-competent virus. During periods of active virus replication, however, there are multiple strategies by which CMV evades host defenses. These include methods referred to as camouflage, which aid the virus in hiding from immune defenses, and those referred to as sabotage, whereby the virus disrupts or manipulates host inflammatory or immune responses. The ultimate pathogen survival strategy, host cell transformation, has been demonstrated in vitro for CMV, but to date has not been demonstrated in vivo. This review surveys the current literature on CMV immunoevasion and suggests a paradigm whereby CMV survives host defenses and contributes to atherogenesis.

Animals↗

PubMed1988

Synergy between subtherapeutic doses of cyclosporine and immunobiological manipulations in rat heart graft recipients.

Cyclosporine in combination with other chemical or biological immunosuppressive modalities has been useful in clinical and experimental organ transplantation. In these studies, the efficacy of adjunctive subtherapeutic doses of CsA given to immunologically enhanced heart graft recipients or to animals treated with an anti-IL-2 receptor monoclonal antibody (ART18) are described. Individually, the treatment entities are only partially effective. In rats undergoing active and passive enhancement alone, heart allograft survival was increased to 25 +/- 12 days in two-thirds, indefinitely in one-third. After ART18 treatment, grafts survive 21 +/- 1 days. Grafts are accepted permanently in animals receiving full-dose CsA (15 mg/kg X 7), but are rejected acutely (c. 7 days) when subtherapeutic doses (1.5 mg/kg X 7) are used. However, when subtherapeutic doses of CsA are given in combination with immunological enhancement or with interleukin-2-receptor-targeted therapy, graft survival increases dramatically, with permanent or markedly prolonged engraftment occurring in all instances. In the early phases of host unresponsiveness, both enhancement and IL-2R-targeted therapy, graft survival increases dramatically, with permanent or markedly prolonged engraftment occurring in all instances. In the early phases of host unresponsiveness, both enhancement and IL-2R-targeted therapy spare selectively T cells with suppressor activity in vivo; in enhanced animals, the W3/25+ subset is responsible for prolonged graft survival, the OX8+ fraction is responsible in ART18-treated animals and in CsA-treated animals. Both subpopulations show suppressor activity in the later stages of combination treatment. IL-3 production is increased significantly in these states of unresponsiveness, an observation also noted during maintenance CsA treatment; this seems to correlate with suppressor activity. Immunoperoxidase studies of the graft infiltrates emphasize the synergistic effects of combination treatments. Thus, subtherapeutic doses of CsA plus biologic host manipulations produce greatly increased graft survival by affecting selectively different host immune mechanisms.

Animals↗

PubMed2026

Wolbachia strain wLhui induces temperature-dependent incomplete cytoplasmic incompatibility in the invasive pest Liriomyza huidobrensis with biocontrol potential.

BACKGROUND: Wolbachia is a maternally inherited endosymbiont that manipulates host reproduction through cytoplasmic incompatibility (CI), offering promising opportunities for biocontrol of agricultural pests. The leaf-miner Liriomyza huidobrensis (Blanchard) is a globally invasive and highly polyphagous pest with a high incidence of Wolbachia infection; however, its reproductive effects remain poorly understood. Here, we investigated the reproductive manipulation induced by the Wolbachia strain wLhui using genomics analyses and crossing assays. RESULTS: wLhui localized primarily to the reproductive tissues of both female and male adults and maintained a 100% infection prevalence across three host generations under both low (15 and 20 °C) and moderate (25 °C) temperatures. Crossing assays showed that wLhui induced incomplete CI, reducing egg hatch by approximately 30% in incompatible crosses. Both CI strength (sh) and wLhui density varied with host rearing temperature. Genome sequencing revealed that wLhui (approximately 1.27 Mb) belongs to supergroup A and harbors two pairs of CI factor genes (cifA and cifB). These Cif proteins are classified as Type I and exhibit substantial phylogenetic and structural divergence. Expression of CifB-pair1 caused growth defects in yeast, suggesting that CifB-pair1 exhibits toxicity. However, no direct interaction between CifA and CifB was detected by yeast two-hybrid assays. CONCLUSIONS: These findings elucidate the role and molecular basis of wLhui-induced reproductive manipulation and highlight its potential for developing Wolbachia-based biocontrol strategies against leaf-miner pests. © 2026 Society of Chemical Industry.

Animals↗

PubMed2005

To replicate or not to replicate: achieving selective oncolytic virus replication in cancer cells through translational control.

To ensure that their mRNAs are translated and that the viral proteins necessary for assembling the next generation of infectious progeny are produced, viruses must effectively seize control of the translational machinery within their host cells. In many cases, the ability to productively engage host translational components can determine if a given cell type can support viral replication, illustrating the critical importance of this task in the viral life cycle. Failure to interface properly with the host translational apparatus can compromise the productive growth cycle, resulting in an abortive infection and radically restricting viral replication. Not only have viruses become facile at commandeering this machinery, they are also particularly adept at manipulating cellular translation control pathways for their own ends. In this review, the mechanisms by which numerous viruses manipulate host translational control circuits are discussed. Furthermore, particular attention is devoted to understanding how interfering with the ability of a virus to properly regulate translation in its host can be exploited to generate oncolytic strains that selectively replicate in cancer cells.

Eukaryotic Initiation Factor-2↗

PubMed2006

Type III effector proteins: doppelgangers of bacterial virulence.

Bacterial pathogens have co-evolved with their hosts in their ongoing quest for advantage in the resulting interaction. These intimate associations have resulted in remarkable adaptations of prokaryotic virulence proteins and their eukaryotic molecular targets. An important strategy used by microbial pathogens of animals to manipulate host cellular functions is structural mimicry of eukaryotic proteins. Recent evidence demonstrates that plant pathogens also use structural mimicry of host factors as a virulence strategy. Nearly all virulence proteins from phytopathogenic bacteria have eluded functional annotation on the basis of primary amino-acid sequence. Recent efforts to determine their three-dimensional structures are, however, revealing important clues about the mechanisms of bacterial virulence in plants.

Bacteria↗

PubMed2001

Inherited microorganisms, sex-specific virulence and reproductive parasitism.

Parasites show an amazing repertoire of adaptations, highlighted by complex life cycles that allow both survival in the host and transmission among hosts. However, there is one heterogeneous group of microorganisms whose adaptations are perhaps even more surprising: parthenogenesis induction, feminization of genetic males, killing of male hosts and sperm-mediated sterilization of uninfected eggs. The common feature of these microorganisms is their mode of transmission: inheritance from mother to offspring. Here, we present an introduction to hereditary symbiosis, focusing on microsporidia and bacteria that manipulate host reproduction in arthropods (reproductive parasites). We also discuss the implications of one of these microorganisms, Wolbachia, for the control of arthropod pests and vectors and for the therapy of filarial diseases. Finally, we discuss whether some parasites of vertebrates might show sex-specific virulence.

Animals↗

PubMed2004

Equal partnership: two trematode species, not one, manipulate the burrowing behaviour of the New Zealand cockle, Austrovenus stutchburyi.

Metacercariae of the trematode Curtuteria australis (Echinostomatidae) accumulate in the foot of the New Zealand cockle Austrovenus stutchburyi, severely impairing the cockle's ability to burrow under the sediments. This results in increased predation by birds on cockles, and thus enhanced transmission rates of the parasite to its bird definitive hosts. This host manipulation by the trematode is costly: fish regularly crop the tip of the foot of cockles stranded on the sediment surface, killing any metacercariae they ingest. A second, previously undetected trematode species (characterized by 23 collar spines) co-existing with C. australis, has been found in the foot of cockles in the Otago Harbour, South Island, New Zealand. The relative abundance of the two species varies among localities, with the identity of the numerically dominant species also changing from one locality to the next. Both C. australis and the new species have a strong preference for encysting in the tip of the cockle's foot, where their impact on the burrowing ability of the host is greatest, and where they both face the risk of cropping by fish. Results indicate that these two species are ecological equivalents, and their combined numbers determine how the cockle population is affected.

Animals↗

PubMed2006

WO bacteriophage transcription in Wolbachia-infected Culex pipiens.

Bacteriophages are commonly found in association with free-living bacteria, both as exogenic phages (virions) and as prophages integrated into the bacterial genome. In contrast, the observation of bacteriophages associated with obligate intracellular bacteria has been described infrequently. An exception is provided by Wolbachia endosymbionts, which harbor multiple phage elements that have been designated as WO phage. Wolbachia are maternally inherited bacteria that occur in the cytoplasm of many invertebrates, where they often manipulate host reproduction. Previously, the WO phage orf7 locus and ankyrin repeat-encoding genes have been observed to represent sources of genetic diversity between Wolbachia (wPip) strains infecting mosquitoes of the Culex pipiens complex and have been suggested as potential participants in the reproductive manipulations. We have characterized WO phage associated with multiple Wolbachia-infected Culex strains and an uninfected strain using electron microscopy and RT-PCR. For each strain, different developmental stages were examined for transcription of three WO phage orf7 genes. The results provide evidence for the presence of both actively transcribed virions and inactive prophages. Variable orf7 transcription patterns are observed in comparisons of differing Cx. pipiens strains. Variability includes both mosquito stage-specific and sexually dimorphic orf7 expression patterns. This report provides additional support for the hypothesis that bacteriophages play an important role in Wolbachia and host evolution.

Animals↗

PubMed2001

An unlikely partnership: parasites, concomitant immunity and host defence.

Concomitant immunity (CI) against macroparasites describes a state of effective anti-larval immunity coupled with persistent adult infection. Experimental studies indicate that immunologically concealed adult worms might promote anti-larval immunity via the release of cross-reactive antigens, thus creating a barrier against continual infection and restricting burden size within the host. CI offers an important potential benefit to established worms by preventing overcrowding within the host. Thus, CI may be interpreted as akin to vaccination; relatively long-lived adult worms 'vaccinate' their host with larval surface antigens and so benefit from reduced conspecific competition. The shared responsibility for host vaccination among adult worms leads to a problem of collective action. Here, we build on earlier analytical findings about the evolutionary forces that shape cooperation among parasites in order to produce a stochastic simulation model of macroparasite social evolution. First, we theoretically investigate a parasite adaptation hypothesis of CI and demonstrate its plausibility under defined conditions, despite the possibility of evolutionary 'cheats'. Then we derive a set of predictions for testing the hypothesis that CI is partly a host-manipulative parasite adaptation. Evidence in support of this model would present an unusual case of adaptive population regulation.

Animals↗