SEARCH · PubMed Health

Results for “host factor”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20Linked to original sources

PubMed2006

[Identification of the novel host factor that interacts with HIV-1 integrase and analysis of the expression profile of the interactor in vivo].

Human immunodeficiency virus type 1 (HIV-1) is one of the lentiviruses, and unlike other retroviruses, HIV-1 is capable of infecting not only dividing cells but also non-dividing cells. It has been strongly suggested that this property is due to the viral mechanism which facilitates the integration of the viral genome cDNA into the host chromosome more efficiently than other retroviruses. HIV-1 integrase (IN) is a viral protein which catalyzes insertion of the viral genome cDNA into the host cell chromosome. However, it has been suggested that HIV-1 IN also plays putative roles at the steps prior to integration such as uncoating, reverse transcription and nuclear transport of the viral cDNA. In this study, we tried to identify the novel host factor which interacted with HIV-1 IN using two different kinds of yeast two hybrid methods: the conventional yeast two hybrid method and the mating method. First, the full-length cDNA fragment of HIV-1 IN was amplified using polymerase chain reaction (PCR), and the amplified products were ligated into pGBT 9 vector as bait. Plasmid vectors expressing human lymphocytes cDNA library and HeLa cDNA library were used as prey plasmid in the conventional yeast two hybrid method and the mating method, respectively. These plasmids were transformed into the corresponding yeast strain cells, and several positive clones were isolated. As a result, a known gene product was identified as a candidate. Further analysis revealed that this protein was expressed in HeLa, 293 T cells, primary macrophages and activated T lymphocytes, and that suppression of this protein expression affected HIV-1 replication.

Cyclic AMP Response Element-Binding Protein↗

PubMed2001

Exploitation of host factors for efficient infection by Shigella.

Shigellosis is a worldwide endemic ulcerating disease of the large intestine caused by enteroinvasive bacteria. Shigella takes the route via M-cells and macrophages to access the basolateral pole of enterocytes. After invasion of and cell-to-cell spread within the epithelial cell layer, the bacterium multiplies within the cytoplasm of enterocytes. Induced by a limited number of bacterial effector proteins, Shigella makes use of established signaling pathways of the host cell to achieve internalization, transcytosis, apoptosis or cell-to-cell spread. This review addresses the host factors required for efficient infection focusing on Shigella-induced cytoskeletal rearrangements and associated signaling.

Colon↗

PubMed2002

Identification of significant host factors for HIV dynamics modelled by non-linear mixed-effects models.

Non-linear mixed-effects models are powerful tools for modelling HIV viral dynamics. In AIDS clinical trials, the viral load measurements for each subject are often sparse. In such cases, linearization procedures are usually used for inferences. Under such linearization procedures, however, standard covariate selection methods based on the approximate likelihood, such as the likelihood ratio test, may not be reliable. In order to identify significant host factors for HIV dynamics, in this paper we consider two alternative approaches for covariate selection: one is based on individual non-linear least square estimates and the other is based on individual empirical Bayes estimates. Our simulation study shows that, if the within-individual data are sparse and the between-individual variation is large, the two alternative covariate selection methods are more reliable than the likelihood ratio test, and the more powerful method based on individual empirical Bayes estimates is especially preferable. We also consider the missing data in covariates. The commonly used missing data methods may lead to misleading results. We recommend a multiple imputation method to handle missing covariates. A real data set from an AIDS clinical trial is analysed based on various covariate selection methods and missing data methods.

Acquired Immunodeficiency Syndrome↗

PubMedDate not supplied

Host factors and genetic susceptibility: a paradigm of the conundrum of pesticide exposure and cancer associations.

Millions of people are exposed to pesticides in non-trivial ways though their work, their leisure and their home environment. Women and children are understudied populations. The mode and types of pesticides to which women and children are exposed are often different from exposures experienced by men. A relatively small proportion of exposed individuals develop the uncommon cancers that have been associated with exposure to specific pesticides. Host factors, including such variables as gender, age at exposure, previous personal and family history, medical history, and genetic susceptibility have been implicated as explanations. The challenges of designing and implementing studies of pesticide exposure and cancer are examined with a special focus on the complexities of studying the environmental and occupational exposure of women to pesticides of varying toxicity using gender-appropriate methodology.

Environmental Exposure↗

PubMed2003

Methodologies to examine the importance of host factors in bioavailability of metals.

Bioavailability provides a link between intrinsic toxicity and the ability to produce that toxic effect in an organism. Biomonitoring tools are essential to assess the health of ecosystems and their component parts, including humans. While field and laboratory data are available, two critical issues to our understanding of bioavailability are often missing: 1) knowing the relationship between dose and tissue concentrations, and 2) species extrapolations. Understanding of high to low dose extrapolation is also critical. Methods to understand the importance of host factors in bioavailability of metals must assess gender, age, nutritional status, individual variability, temporal changes, and critical habitat effects. Methods to examine these variables include correlational, observational, experimental, epidemiological, and modeling studies, or a combination of these. Data gaps include developing more representative studies of human and animal populations, better analytical tools for rapid determination of metal content in the field, improved analytical characterization of metal bioavailability, and concurrent studies of different metals.

Animals↗

PubMed1997

Involvement of host factors in transcription from baculovirus very late promoters -- a review.

The baculovirus expression vector system has emerged as the system of choice for the expression of a number of heterologous genes of both prokaryotic and eukaryotic origin. This system utilizes the baculovirus very late, hyperactive polyhedrin and p10 promoters to drive the transcription of foreign genes. Regulation of transcription from these promoters is presently not well understood even though a number of viral gene products that may be important for transcription have been identified. Fresh insight into host-virus interactions during baculovirus pathogenesis is now offered by the identification of insect host factors that interact with transcriptionally essential motifs of these promoters as well as cis-acting enhancer-like elements upstream from the promoter.

Base Sequence↗

PubMed2002

Nimesulide and hepatic adverse effects: roles of reactive metabolites and host factors.

Nimesulide, similar to other nonsteroidal anti-inflammatory drugs (NSAIDs), has been associated with rare and unpredictable but serious hepatic adverse reactions. The low incidence (about 0.1 case per 100,000 treated patients, no more than with most other NSAIDs), estimated from the total number of reported cases relative to the unit sales, plus the fact that the time to onset of liver reactions varied from several days to almost 1 year, suggest that the rare cases of liver injury may be caused by a metabolic idiosyncrasy. This implies that multiple individual host factors affect the toxic potential of nimesulide and/or its metabolites. At the molecular level, reductive bioactivation of the aromatic nitro group might cause oxidoreductive stress and induce covalent binding of, reactive intermediates to proteins. Nimesulide can cause toxicity to mitochondria in vitro, although it is unlikely that the high concentrations required are therapeutically relevant. The mitochondrial toxicity at these supratherapeutic concentrations of nimesulide is characterised by uncoupling of oxidative phosphorylation and opening of the membrane permeability transition pore. Because severe hepatic damage is very rare, and because normally reactive metabolites are readily inactivated or their deleterious effects antagonised, perhaps genetically or environmentally determined alterations in these pathways account for the rare individual susceptibility.

Biotransformation↗

PubMed1991

Role of integration host factor in the regulation of the glnHp2 promoter of Escherichia coli.

The glnHPQ operon of Escherichia coli encodes components of the high-affinity glutamine transport system. One of the two promoters of this operon, glnHp2, is responsible for expression of the operon under nitrogen-limiting conditions. The general nitrogen regulatory protein (NRI) binds to two overlapping sites centered at -109 and -122 from the transcription start site and, when phosphorylated, activates transcription of glnHp2 by catalyzing isomerization of the closed sigma 54-RNA polymerase promoter complex to an open complex. The DNA-bending protein integration host factor (IHF) binds to a site immediately upstream of glnHp2 and enhances the activation of open complex formation by NRI phosphate. The NRI-binding sites can be moved several hundred base pairs further upstream without altering the ability of NRI phosphate to activate open complex formation. We propose that the IHF-induced bend can facilitate or obstruct the interaction between NRI phosphate and the closed complex depending on the relative positions of NRI phosphate and sigma 54-RNA polymerase on the DNA.

Bacterial Proteins↗

PubMed1999

Ephelides are more related to pigmentary constitutional host factors than solar lentigines.

Ephelides and solar lentigines are benign pigmented spots, which are currently associated with an increased risk of skin cancer. These two pigmented spots are known to be discriminated by their clinical, histological, and electron microscopic characteristics, even though occasional misclassification can occur because of their similarity. It has also been questioned whether these spots are not one and the same. In this study, we have attempted to differentiate between these two pigmented spots with the use of a standardized protocol for clinical examinations on 272 healthy volunteers, paying particular consideration to their pigmentary and constitutional host factors. We found that solar lentigines 1) are more prevalent than ephelides, 2) increase in prevalence and number with higher age, and 3) are most prevalent on the trunk and occur more frequently in males than in females. A trend is also observed whereby ephelides 1) loose their prevalence with age, 2) become equally distributed on the face, arms, and trunk, and 3) occur more frequently in females. An intimate association of ephelides, but not solar lentigines, has been found with hair color and skin type. All of these findings are in agreement with most of those reported in the literature, supporting the view that ephelides and solar lentigines are different types of pigmented lesions.

Adult↗

PubMed1995

Host factors LR1 and Sp1 regulate the Fp promoter of Epstein-Barr virus.

The Epstein-Barr virus EBNA-1 gene product is essential for latent replication of the virus. In transformed cells characterized by the most restricted patterns of viral latent gene expression, EBNA-1 transcription is driven from the Fp promoter. We have used genetic and biochemical techniques to study the promoter-proximal elements that regulate Fp expression in B cells. We show that a 114-bp fragment of DNA spanning the Fp "TATA" box functions as a remarkably active transcriptional regulatory element in B cells. Two host factors, Sp1 and LR1, regulate Fp transcription from the promoter-proximal region. Sp1 binds a single site just downstream of the TATA box, and LR1 binds two sites just upstream of the TATA box. Transcripts from both the viral genome and the minimal promoter initiate at the same unique site, and one function of LR1 at Fp is to direct initiation to this unique start site. In contrast to Sp1, which is ubiquitous, LR1 is present only in activated B cells and may contribute to cell-type-specific transformation by Epstein-Barr virus.

Antigens, Viral↗

PubMed2005

Expression of a viral polymerase-bound host factor turns human cell lines permissive to a plant- and insect-infecting virus.

Tospoviruses are the only plant-infecting members of the Bunyaviridae family of ambisense ssRNA viruses. Tomato spotted wilt tospovirus (TSWV), the type-member, also causes mild infection on its main insect vector, Frankliniella occidentalis. Herein, we identified an F. occidentalis putative transcription factor (FoTF) that binds to the TSWV RNA-dependent RNA polymerase and to viral RNA. Using in vitro RNA synthesis assays, we show that addition of purified FoTF improves viral replication, but not transcription. Expression of FoTF deletion mutants, unable to bind the RNA-dependent RNA polymerase or viral RNA, blocks TSWV replication in F. occidentalis cells. Finally, expression of FoTF wild-type turns human cell lines permissive to TSWV replication. These data indicate that FoTF is a host factor required for TSWV replication in vitro and in vivo, provide an experimental system that could be used to compare molecular defense mechanisms in plant, insect, and human cells against the same pathogen (TSWV), and could lead to a better understanding of evolutionary processes of ambisense RNA viruses.

Animals↗

PubMedDate not supplied

Host factors in lung cancer risk: a review of interdisciplinary studies.

Host-specific factors influence risk for lung cancer. A few case-control and family studies of lung cancer susceptibility allowed for known lung cancer carcinogens and showed strong familial clustering with some evidence for a codominantly acting major gene. Cytochrome P-450 enzymes (e.g., CYP1A1) activate many carcinogens in tobacco smoke but have shown inconsistent associations with risk for lung cancer. Case-control studies that assess the effects of CYPIID6 on lung cancer risk have consistently shown a mildly decreased risk for lung cancer among poor metabolizers. Cell surface markers have shown little relation to risk for lung cancer. Studies involving DNA or hemoglobin adducts, sister chromatid exchange, or oncogene activation only indirectly measure host-specific risk, and these assays have suffered from poor reproducibility and high cost. We describe epidemiological designs to assess specific genetic factors that may alter lung cancer risk.

Biomarkers↗

PubMed2001

New insights into host factor requirements for prokaryotic beta-recombinase-mediated reactions in mammalian cells.

The prokaryotic beta-recombinase catalyzes site-specific recombination between two directly oriented minimal six sites in mammalian cells, both on episomic and chromatin-integrated substrates. Using a specific recombination activated gene expression system, we report the site-specific recombination activity of an enhanced green fluorescent protein (EGFP) fused version of beta-recombinase (beta-EGFP). This allows expression of active beta-recombinase detectable in vivo and in fixed cells by fluorescence microscopy. In addition, cellular viability is compatible with a substantial level of expression of the beta-EGFP protein. Using fluorescence-activated cell sorting, we have been able to enrich cell populations expressing this fusion protein. Application of this strategy has allowed us to study in more depth the host factor requirements for this system. Previous work showed that eukaryotic HMG1 protein was necessary and sufficient to help beta-recombinase activity in vitro. The influence of ectopic expression of HMG1 protein in the recombination process has been analyzed, indicating that HMG1 overexpression does not lead to a significant increase on the efficiency of beta-recombinase-mediated recombination both on episomal substrates and chromatin-associated targets. In addition, beta-recombinase-mediated recombination has been demonstrated in HMG1 deficient cells at the same levels as in wild type cells. These data demonstrate the existence of cellular factors different from HMG-1 that can act as helpers for beta-recombinase activity in the eukaryotic environment.

3T3 Cells↗

PubMed1986

Microbial and host factors that influence adherence of Escherichia coli to kidney epithelium.

The adherence of Escherichia coli 06K13H1 to punch biopsy specimens of rabbit renal pelvic tissue and isolated epithelial cells was examined quantitatively. Organisms with pili adhered readily to kidney tissue, whereas organisms without pili (nonpiliated or grown in glucose-containing media) had significantly less adherence. Adherence was inhibited by antibody to pili antigen but not by mannose (a determinant of adherence to buccal mucosal cells). Studies were done to evaluate adherence under conditions operative in the renal medulla. The combination of hypertonic salt or urea solutions in acid pH interfered with adherence of the mannose-resistant strain. In additional studies of kidneys from humans, a similar effect of antipili serum and mannose was seen. These studies provide further evidence that pili are important in the initiation of upper urinary tract infection and define host factors that may inhibit initiation of infection.

Adhesiveness↗

PubMed1991

Role of host factors in the regulation of the enterotoxin B gene.

The levels of staphylococcal enterotoxin B (SEB) produced by various naturally occurring toxinogenic strains of Staphylococcus aureus are highly variable. The SEB gene (seb) from a high-producer strain, S6, has previously been cloned and characterized. Cloning and nucleotide sequence analysis of the upstream region of the seb gene from DU4916 and COL (medium- and low-level toxin-producer strains, respectively) showed that their sequence was identical to that of the seb gene from strain S6. Strains carrying the cloned seb gene from DU4916 and COL produced similar levels of SEB protein and mRNA to those produced by strains carrying the cloned seb gene from strain S6. An RNA encoded by the delta-lysin gene (hld) has been shown to regulate the genes for a number of extracellular proteins, including SEB. Northern (RNA) blot analysis showed that variable levels of hld RNA were present in various SEB-producer strains, with the order being S6 greater than DU4916 greater than COL. Our results suggest that differences in host factor(s), including the hld RNA, are responsible for the production of different amounts of SEB by many naturally occurring strains.

Blotting, Southern↗

PubMed1986

Screening for the influence of host factors on warfarin clearance using a single dose single sample procedure.

A single dose, single sample procedure for estimating warfarin clearance for screening purposes was evaluated. Single sample estimates of warfarin clearance, CL/F, were closest to actual values for warfarin clearance, CL/F, calculated from multiple sample data when the sample was collected 120 h after warfarin ingestion. An apparent volume of distribution, V/F, of 0.17 l/kg was used in calculating CL/F. After a single dose of warfarin single sample values of CL/F averaged 0.243 l/h +/- 0.042 (N = 12) which compared well with a multiple sample-based value of CL/F which was 0.243 l/h +/- 0.046 (N = 12). When an erythromycin pretreatment was started before warfarin ingestion and continued throughout the period of warfarin elimination CL/F decreased to 0.208 l/h +/- 0.047 while CL/F decreased to 0.210 l/h +/- 0.061. Mean prediction error for CL/F relative to CL/F was -0.001 l/h with a 95% confidence interval of -0.010 to 0.009 l/h. Warfarin is a drug with pharmacokinetic characteristics enabling it to be used in a single dose single sample procedure in screening for host factor influences on its clearance.

Adult↗

PubMed1999

Influence of shift work and host factors on endotoxin-related acute peak flow changes.

There is limited knowledge about which internal and external factors influence respiratory effects of occupational endotoxin exposure. Relationships between endotoxin exposure, work-related respiratory symptoms, and acute peak flow changes were studied in 97 shift workers in the potato processing industry. For each worker, across-shift peak flow changes were determined for morning, afternoon, and night shifts. A higher endotoxin exposure was associated with an increased prevalence of work-related symptoms, a smaller peak expiratory flow (PEF) increase across the morning shift, and a larger PEF decrease across afternoon and night shifts. The largest effects occurred during the afternoon shift. No consistent differences between smokers and nonsmokers, and between atopics and nonatopics were observed. We conclude that endotoxin exposure in the potato processing industry is related to across-shift peak flow changes and the occurrence of work-related respiratory symptoms. The host factors smoking and atopy are not important confounding or effect-modifying factors in these relationships. In respiratory health studies among shift workers, it is important to investigate all work shifts before drawing definitive conclusions about exposure-response relationships.

Adult↗

PubMed1990

Uveal melanoma in relation to ultraviolet light exposure and host factors.

We conducted a case-control interview study among 1277 subjects (407 patients, 870 controls selected by using random digit dial) in 11 western United States to determine whether uveal melanoma and cutaneous melanoma shared common risk factors. After adjustment for other factors, the risk of uveal melanoma was increased for those with green, gray, or hazel eyes [relative risk (RR) = 2.5, P less than 0.001] or blue eyes (RR = 2.2, P less than 0.001) when compared to brown. A tendency to sunburn after 0.5 h midday summer sun exposure increased risk for uveal melanoma (burn with tanning RR = 1.5, P = 0.02; burn with little tanning RR = 1.8, P less than 0.001; burn with no tanning RR = 1.7, P = 0.002); as did exposure to UV or black lights (RR = 3.7, P = 0.003); and welding burn, sunburn of the eye, or snow blindness (RR = 7.2, P less than 0.001). An association with uveal melanoma was also noted with an increasing number of large nevi (P = 0.04 for trend), although the individual risk estimates were not remarkable. These data suggest that host factors and exposure to UV light are risk factors for uveal melanoma.

Adult↗