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At least 307 records · Page 17Linked to original sources
PubMed1999

Human immunodeficiency virus type 1 (HIV-1) Vpr functions as an immediate-early protein during HIV-1 infection.

Human immunodeficiency virus type 1 (HIV-1) Vpr is a virion-associated protein which facilitates HIV-1 infection of nondividing cells by contributing to the nuclear transport of the preintegration complex (PIC). Vpr was also shown to induce a cell cycle G2 arrest in infected proliferating cells that optimizes HIV-1 long terminal repeat (LTR)-directed gene expression and viral production. However, it is unclear whether this activity is mediated primarily early by virion-associated Vpr or alternatively late during infection when Vpr is de novo expressed. We report here that in the absence of de novo expression, virion-associated Vpr induces a transient G2 arrest that can subsequently lead to cell killing by apoptosis. Interestingly, the induction of both cell cycle G2 arrest and apoptosis by virion-associated Vpr requires viral entry but not viral replication, since reverse transcriptase and protease inhibitor treatments do not prevent these Vpr effects. These results raise the possibility that in vivo both infectious and noninfectious viruses contribute to the dysfunction and killing of CD4(+) cells. In addition, our results reveal that virion-associated Vpr stimulates viral replication in proliferating cells after establishing a cell cycle G2 arrest by increasing LTR-directed gene expression. Importantly, this Vpr-mediated LTR activation appears to be a requirement for subsequent optimal Tat transactivation. Taken together, these results strongly suggest that in addition to participating in the HIV PIC nuclear transport in nondividing cells, virion-associated Vpr activates HIV-1 LTR-directed gene expression by manipulating the host cell cycle. From this, we conclude that Vpr functions as an immediate-early protein during HIV-1 infection.

Anti-HIV Agents↗
PubMed2006

Evolution of plant pathogenicity in Streptomyces.

Among the multitude of soil-inhabiting, saprophytic Streptomyces species are a growing number of plant pathogens that cause economically important diseases, including potato scab. Streptomyces scabies is the dominant pathogenic species worldwide, but is only one of many that cause very similar disease symptoms on plants. Molecular genetic analysis is beginning to identify the mechanisms used by plant pathogenic species to manipulate their hosts. The nitrated dipeptide phytotoxin, thaxtomin, inhibits cellulose biosynthesis in expanding plant tissues, stimulates Ca2+ spiking, and causes cell death. A secreted necrogenic protein, Nec1, contributes to virulence on diverse plant species. The thaxtomin biosynthetic genes and nec1 lie on a large mobilizable PAI, along with other putative virulence genes including a cytokinin biosynthetic pathway and a saponinase homolog. The PAI is mobilized during conjugation and site-specifically inserts in the linear chromosome of recipient species, accounting for the emergence of new pathogens in agricultural systems. The recently available genome sequence of S. scabies will accelerate research on host-pathogen interactions.

Biological Evolution↗
PubMed2005

Inflammation in the genesis and perpetuation of cancer: summary and recommendations from a national cancer institute-sponsored meeting.

The Inflammation and Cancer Think Tank Meeting was organized by the National Cancer Institute with the purpose of identifying research advances, gaps, and opportunities for the study and clinical application of the role of inflammation on tumorigenesis. The format of this meeting consisted of brief presentations that focused on concepts, with extensive discussion periods to allow participants to identify issues and barriers limiting progress in this area. The strong relationship between inflammation and cancer in the gastrointestinal tract prompted several presentations that were focused on carcinogenesis within this organ system; however, many of the same immune mediators that influence esophageal, gastric, and colorectal carcinoma were also shown to influence inflammation-related malignancies at other anatomic sites. This article summarizes the findings of this Think Tank Meeting, which highlight the intimate relationship between malignant cells and their inflammatory microenvironment and specifically address opportunities to manipulate the host immune response and therefore intervene at different points along the tumorigenic cascade.

Animals↗
PubMed2005

Nitric oxide production is regulated by fever-range thermal stimulation of murine macrophages.

As macrophages are often called to function at times of elevated ambient temperature (e.g., during local inflammation or systemic fever), it is possible that their production of critical effector molecules, such as nitric oxide (NO) or inducible NO synthase (iNOS), is sensitive to physiological changes in temperature. To test this possibility, the threshold requirements for production of NO and iNOS in murine peritoneal macrophages maintained under normothermic conditions (37 degrees C) or following mild (fever-range) hyperthermia (39.5 degrees C) were compared. We found that hyperthermia alone had no observable effect on basal NO production or iNOS protein or message. However, although interferon (IFN)-gamma and lipopolysaccharide (LPS) were needed to induce NO at 37 degrees C, we observed that addition of only LPS was sufficient for production of NO if there were a pretreatment at 39.5 degrees C. Further, if IFN-gamma and LPS were given after thermal exposure, a substantial increase in NO and iNOS was observed over that seen using cells kept at normothermic conditions. Macrophages isolated from mice lacking heat shock factor-1 did not attenuate the ability of mild thermal stress to modulate NO production. Reverse transcriptase-polymerase chain reaction data revealed that thermal regulation of iNOS expression is not entirely at the transcriptional level, suggesting possible points of post-transcriptional thermal sensitivity. These data support the concept that altering the thermal microenvironment is an important means by which the host can manipulate macrophage responses. Increases in temperature (e.g., during fever) may function to lower the activation threshold needed for production of effector molecules in times of infection.

Animals↗
PubMed2025

Induction of tunnelling nanotube-like structures by influenza A viruses requires the onset of apoptosis.

As well as spreading through virions, influenza A viruses (IAVs) can evade antiviral drugs and neutralising antibodies by spreading directly from cell to cell. In cell culture this can occur by the induction of intercellular membrane connections known as tunnelling nanotube-like structures (TLSs), which are capable of trafficking the viral genome between cells. Here, we showed that TLSs are formed by IAV infected cells in vivo, and then used in vitro models to ask how IAVs induce their formation. We found that TLS formation is not induced by cytokine signalling from infected to uninfected cells, but induction does require intracellular IAV replication. IAV replication can form filamentous virions which have structural similarities to TLSs, but we found that TLS induction is independent of virion morphology. We therefore looked at the intracellular responses to infection and found that the induction of TLSs correlated with the induction of apoptosis. Furthermore, the ability of IAVs to drive TLS formation can be modulated by chemically inhibiting, or inducing apoptosis. Finally, we found that inhibiting apoptosis, which prevents IAVs from inducing TLSs, lead to a significant reduction in the ability of IAVs to directly spread between cells. Our results, which suggest that IAVs can control their ability to spread directly from cell to cell by driving infected cells into apoptosis, identifies a new way in which a virus can manipulate its host to evade antiviral immune responses.

Apoptosis↗
PubMed2001

Cytomegalovirus and the aging population.

Human cytomegalovirus (HCMV) has the largest genome of any virus known to infect man. The virus has evolved many strategies to manipulate the host immune systems and so can remain latent and evade important immune responses. The human host mounts a substantial immune response against the virus, with up to 1% of the virus-specific CD8+ T cells being directed against specific epitopes. Acquisition of HCMV occurs progressively from an early age, and in developed countries the overall seroprevalence is approximately 60%. In contrast, specific communities such as gay men, lower socioeconomic groups and people residing in developing countries have seroprevalence rates that can exceed 90%. It is a widely held belief that successful control of viral infections decreases with increasing age because of a reduction in the capacity of the immune system. Studies in aging populations have shown a specific expansion of the CD8+, CD28- and CD57+ subset of cells in patients who are HCMV-seropositive. Prior infection with HCMV has also been associated with a significantly increased number of CD4+ and CD8+ lymphocytes, as well as cells expressing CD56 and HLA-DR. Thus, HCMV infection can cause substantial perturbations in T cell subsets and these effects persist in the aging population. In the context of solid organ transplantation, older age of both recipients and donors may serve to increase the frequency of donor-positive recipient-positive (D+R+) transplants, which have only a moderate risk of HCMV disease. In the context of HIV infection, age has been a dominant risk factor for progression to AIDS and death. At present, it does not appear that this can be explained by lack of immune control of HCMV in the aging population, although studies have identified prior HCMV infection as a risk factor for AIDS and death independent of age. We await further investigations to determine whether the immune control of HCMV in the elderly patient is as effective as in the younger adult, and whether this is linked to pathological consequences.

Age Factors↗
PubMed2005

Antigen-presenting cells 8015 (Provenge) in patients with androgen-dependent, biochemically relapsed prostate cancer.

BACKGROUND: Antigen-presenting cells 8015 (APC8015; Provenge) is an immunotherapeutic product designed to initiate a T-cell-mediated immune response against prostatic acid phosphatase, an antigen overexpressed in 95% of prostate cancer cells. In phase I/II trials, APC8015 has shown immunologic and clinical responses in patients with androgen-independent prostate cancer. This phase II trial was conducted to assess the prostate-specific antigen (PSA)-modulating effects of APC8015 in patients with androgen-dependent prostate cancer (ADPC) with biochemical progression. PATIENTS AND METHODS: Patients with nonmetastatic recurrent disease as manifested by increasing PSA levels (0.4-6.0 ng/mL) and who had undergone previous definitive surgical or radiation therapy were enrolled. Therapy consisted of APC8015 infusion on weeks 0, 2, and 4 (ie, 3 infusions). Prostate-specific antigen was measured at baseline and monthly until disease progression, defined as a doubling of the baseline or nadir PSA value (whichever was lower) to > or = 4 ng/mL or development of distant metastases. RESULTS: Thirteen of 18 patients demonstrated an increase in PSA doubling time (PSADT), with a median increase of 62% (4.9 months before treatment vs. 7.9 months after treatment; P = 0.09; signed-rank test). CONCLUSION: Therapy was well tolerated. APC8015 as single-agent immunotherapy for patients with ADPC and biochemical progression did not result in > or = 50% decrease in PSA from baseline levels but did appear to modulate PSADT in some patients. Further manipulations of host immunity may be required to achieve a significant antitumor effect.

Adenocarcinoma↗
PubMed2005

Vascularization of melanoma by mobilization and remodeling of preexisting latent vessels to patency.

Tumors must manipulate the host vasculature to provide a blood supply adequate for their proliferation. Although tumors may arise as avascular masses, there is increasing evidence that some tumors begin to proliferate by first co-opting preexisting host blood vessels. By fluorescent vascular imaging, we provide evidence that the vasculature in orthotopically implanted melanoma arises from a preexisting red cell-deficient vascular network that remodels to patency to accommodate the requirements of the expanding tumor mass. Topical application of vascular endothelial growth factor to vascular beds generated immediate and robust vascular transitions that were morphologically similar to tumor-induced transitions. N(phi)-nitro-L-arginine, a nitric oxide inhibitor, significantly inhibited the growth of a syngeneic K1735M2 melanoma by reducing blood supply to the tumor by a mechanism independent of endothelial cell proliferation. These findings suggest that tumor-induced remodeling of red cell-deficient vessels to patency contributes to tumor vascularization and growth.

Animals↗
PubMedDate not supplied

Cancer immunotherapy with low-dose interleukin-2 subcutaneous administration: potential efficacy in most solid tumor histotypes by a concomitant treatment with the pineal hormone melatonin.

The antitumor efficacy of IL-2 is limited to renal cancer and melanoma. Several cytokines have been associated with IL-2 in an attempt to improve its activity, without, however, any clear benefit. Recent experimental and clinical studies have suggested the possibility to manipulate the host biological response by immunomodulating neurohormones, such as the pineal hormone melatonin (MLT). On the bases of these considerations, we have designed a neuroimmunotherapeutic protocol with low-dose IL-2 subcutaneous therapy (3 million IU/day for 6 days/week for 4 weeks) plus MLT (40 mg/day orally, starting 7 days before IL-2) in advanced solid neoplasms other than renal cancer and melanoma, which are generally resistant to IL-2 alone. The study included 82 patients, 72 of whom showed distant organ metastases. Tumor histotypes were, as follows: non-small cell lung cancer: 19; hepatocarcinoma: 16; colon cancer: 15; gastric cancer: 11; cancer of pancreas: 11; breast cancer: 6; miscellaneous: 4. Objective tumor regression were achieved in 17/82 (21%) patients, consisting of CR in 4 (liver: 2; pancreas: 1; stomach: 1) and PR in 13 (lung: 4; liver: 4; stomach: 2; pancreas: 1; breast: 1; colon: 1). The median duration of response was 8+ months. A stabilization of disease was obtained in 30 patients, while the other 35 patients progressed. The lack of progression was associated with a significantly higher increase in lymphocyte and eosinophil mean number and with a significantly lower increase in neopterin mean levels. The treatment was well tolerated in all patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Microbial parasites versus developing T cells: an evolutionary 'arms race' with implications for the timing of thymic involution and HIV pathogenesis.

The thymus attempts to ensure that T cells which emerge from it are able to discriminate self from nonself. As such, it is a potential 'backdoor' through which microbial parasites can enter, manipulate the host into perceiving them as 'self', and thereby avoid immune surveillance. It is proposed that the host has evolved to overcome this parasitic strategy by rapidly producing large numbers of long-lived T cells very early in life (closing the backdoor), before the developing individual has significant contact with infectious organisms, and while still under the protection of its mother's intact immune system. Hence the capacity of the thymus to function efficiently early in the lifespan would have been strongly favored by natural selection. It is well established in evolutionary biology that strong selection favoring enhanced early function easily accommodates, through pleiotropy, the accumulation of later occurring negative effects, and it is through this process that thymic involution and subsequent immune system senescence may have evolved. Once a large pool of competent T cells has been produced, even those microbes capable of contaminating the thymus usually can be eliminated, or at least contained. However, microbes that both destroy peripheral T cells (particularly peripheral T cells that are activated against them), and contaminate the thymus (leading to deletion of potential replacements of the destroyed peripheral cells), may be able to eventually overcome the immune system, thus producing disease after a long period of apparent latency. Human immunodeficiency virus, which is initially well controlled by the immune system, may become unleashed via this process.

Adult↗
PubMed2005

Metabolic biotinylation of lentiviral pseudotypes for scalable paramagnetic microparticle-dependent manipulation.

Nonviral, host-derived proteins on lentiviral vector surfaces can have a profound effect on the vector's biology as they can both promote infection and provide resistance to complement inactivation. We have exploited this to engineer a specific posttranslational modification of a "nonenvelope," virally associated protein. The bacterial biotin ligase (BirA) and a modified human DeltaLNGFR have been introduced into HEK293T cells and their protein products directed to the lumen of the endoplasmic reticulum. The BirA then couples biotin to an acceptor peptide that has been fused to the DeltaLNGFR. This results in the covalent linkage of biotin to the extracellular domain of the DeltaLNGFR expressed on the cell surface. Lentiviral vectors from these cells are metabolically labeled with biotin in the presence of free biotin. These biotinylated lentiviral vectors have a high affinity for streptavidin paramagnetic particles and, once captured, are easily manipulated in vitro. This is illustrated by the concentration of lentiviral vectors pseudotyped with either the VSV-G or an amphotropic envelope in excess of 4500-fold. This new cell line has the potential for widespread application to envelope pseudotypes compatible with lentiviral vector production.

Biotin↗
PubMed1975

In vivo interactions between murine leukemia and sarcoma viruses.

Experiments have been performed with the aim of elucidating the nature and the extent of the in vivo interactions between murine leukemia viruses (MuLVs) and murine sarcoma virus (MSV). BALB/c and CBA mice, injected neonatally with Graffi or passage A Gross viruses (MuLV-Gi, MuLV-G), have been inoculated as young adults with murine sarcoma virus, Moloney strain (MSV-M). A higher percentage of nonregressing sarcomas appeared in these animals, sometimes accompanied simultaneously by leukemia. The immune reactivity of mice receiving MuLV-Gi at birth was found to be significantly depressed when evaluated by the hemolytic palque-forming cell (PFC) technique. However, in mice infected with MuLV-Gi and MSV-M the number of PFC ranged within the control values or slightly increased. The potentiation of MSV-M oncogenicity following infection with MuLV was studied in a more natural situation. Adult AKR mice, known to release endogenous MuLV continuously, were injected with MSV-M. The incidence of induced sarcomas was similar to that observed in control BALB/c mice inoculated with MSV-M. Moreover, tumors developed with a very long latent period. On the other hand, the great majority of tumors showed no regression and ultimately killed the host. Additional experiments, making use of immunologic manipulation of the host and Fl hybrids, suggest that the relative resistance to MSV-M oncogenesis in AKR mice is influenced by genetic and immunologic factors. MSV recovered from MSV-M-induced tumors in AKR and C58 mice was typed by highly specific mouse antisera. The results clearly showed that formation of a new MSV pseudotype occurred in vivo, the endogenous Gross virus acting as helper.

AKR murine leukemia virus↗
PubMed1995

Blood-feeding behavior of dengue-2 virus-infected Aedes aegypti.

This study was designed to determine if infection of Aedes aegypti with dengue-2 virus affects the ability of the mosquito to efficiently locate and imbibe blood from an uninfected host. Previous studies suggest that some parasites manipulate their arthropod host to increase the probability of transmission by interfering with blood-feeding efficiency. We found no evidence that dengue-2 virus infection by intrathoracic inoculation impaired the blood-feeding efficiency of Ae. aegypti. We speculate that natural selection has not favored the evolution of dengue viruses that increase vector probing time because uninfected Ae. aegypti take multiple blood meals during each gonotrophic cycle and further increases in vector probing would not significantly increase virus fitness.

Aedes↗
PubMed2003

Tailoring host immune responses to Listeria by manipulation of virulence genes -- the interface between innate and acquired immunity.

Although attenuated strains of microbial pathogens have triggered vaccine development from its origin, the role of virulence factors in determining host immunity has remained largely unexplored. Using the murine listeriosis model, we investigated whether the induction and expansion of protective and inflammatory T cell responses may be modified by selective manipulation of virulence genes. We intentionally deleted specific genes of Listeria monocytogenes, including those encoding the positive regulatory factor (prfA), hemolysin (hly), the actin nucleator (actA), and phospholipase B (plcB). The resulting strains showed decisive differences in their immunogenic properties. In particular, we identified a double-deletion mutant that retained Listeria's profound ability to induce protective CD8(+) T cells, but that is strongly attenuated and exhibits a significantly reduced ability to induce CD4(+) T cell-mediated inflammation. We conclude that this mutant, L. monocytogenes DeltaactADeltaplcB, is at present the most promising mutant for a bacterial vaccine vector and is able to safely induce potent CD8(+) T cell-mediated immunity.

Animals↗
PubMed2004

Modulation of the immune system by Listeria monocytogenes-mediated gene transfer into mammalian cells.

In this study, we established a method for Listeria monocytogenes(Lm)-mediated gene transfer into mammalian cells to manipulate the immune response of the host during infection by pathogens. We used the Lm-mediated gene transfer method in an in vivo study to manipulate host immune responses against Leishmania major(L. major )-infection. The injection of Lm modulated the susceptible host into a resistant state against L. major-infection. A more efficient protective effect was obtained with the injection of IL-12-cDNA containing Lm, and the protective effect was stronger than that of the resistant strain. The protective mechanism of Lm-injection against L. major-infection observed here appeared to be a result of the activation of the local immune system by the Lm-mediated gene transfer method. The present study is the first demonstration that a gene introduced into a host by Lm works to modulate the murine host immune response against infections in vivo. Since this system strongly induces Th1 responses and suppresses Th2 responses in infected hosts, the system can be used for controlling infectious diseases and for protection against allergic responses in the future.

Animals↗
PubMed2003

A bacterial symbiont in the Bacteroidetes induces cytoplasmic incompatibility in the parasitoid wasp Encarsia pergandiella.

Vertically transmitted symbionts of arthropods have been implicated in several reproductive manipulations of their hosts. These include cytoplasmic incompatibility (CI), parthenogenesis induction in haplodiploid species (PI), feminization and male killing. One symbiont lineage in the alpha-Proteobacteria, Wolbachia, is the only bacterium known to cause all of these effects, and has been thought to be unique in causing CI, in which the fecundity of uninfected females is reduced after mating with infected males. Here, we provide evidence that an undescribed symbiont in the Bacteroidetes group causes CI in a sexual population of the parasitic wasp Encarsia pergandiella. Wasps were crossed in all four possible combinations of infected and uninfected individuals. In the cross predicted to be incompatible, infected (I) males x uninfected (U) females, progeny production was severely reduced, with these females producing only 12.6% of the number of progeny in other crosses. The incompatibility observed in this haplodiploid species was the female mortality type; dissections showed that most progeny from the incompatible cross died as eggs. The 16S rDNA sequence of this symbiont is 99% identical to a parthenogenesis-inducing symbiont in other Encarsia, and 96% identical to a feminizing symbiont in haplodiploid Brevipalpus mites. Thus, this recently discovered symbiont lineage is capable of inducing three of the four principal manipulations of host reproduction known to be caused by Wolbachia.

Animals↗
PubMed2003

EST mining and functional expression assays identify extracellular effector proteins from the plant pathogen Phytophthora.

Plant pathogenic microbes have the remarkable ability to manipulate biochemical, physiological, and morphological processes in their host plants. These manipulations are achieved through a diverse array of effector molecules that can either promote infection or trigger defense responses. We describe a general functional genomics approach aimed at identifying extracellular effector proteins from plant pathogenic microorganisms by combining data mining of expressed sequence tags (ESTs) with virus-based high-throughput functional expression assays in plants. PexFinder, an algorithm for automated identification of extracellular proteins from EST data sets, was developed and applied to 2147 ESTs from the oomycete plant pathogen Phytophthora infestans. The program identified 261 ESTs (12.2%) corresponding to a set of 142 nonredundant Pex (Phytophthora extracellular protein) cDNAs. Of these, 78 (55%) Pex cDNAs were novel with no significant matches in public databases. Validation of PexFinder was performed using proteomic analysis of secreted protein of P. infestans. To identify which of the Pex cDNAs encode effector proteins that manipulate plant processes, high-throughput functional expression assays in plants were performed on 63 of the identified cDNAs using an Agrobacterium tumefaciens binary vector carrying the potato virus X (PVX) genome. This led to the discovery of two novel necrosis-inducing cDNAs, crn1 and crn2, encoding extracellular proteins that belong to a large and complex protein family in Phytophthora. Further characterization of the crn genes indicated that they are both expressed in P. infestans during colonization of the host plant tomato and that crn2 induced defense-response genes in tomato. Our results indicate that combining data mining using PexFinder with PVX-based functional assays can facilitate the discovery of novel pathogen effector proteins. In principle, this strategy can be applied to a variety of eukaryotic plant pathogens, including oomycetes, fungi, and nematodes.

Algal Proteins↗