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PubMed1992

[Host factors which influence the outcome of pneumonia in the elderly].

We examined 135 elderly patients with pneumonia to clarify the factors predicting on the outcomes of the elderly pneumonic patients. In the fatal cases respiratory symptoms such as cough and sputum, except for dyspnea were less frequent but pulmonary infiltrations on chest roentgenograms were more massive as compared with those in the survived cases. Thus, it was suggested that in the fatal cases the more advanced pneumonia had developed at the time when the diagnosis of pneumonia was made. The fatal cases showed hypoalbuminemia, hypocholesterolemia and hyponatlemia more frequently as compared with survived cases. Among these laboratory values, the decreased serum albumin concentration seemed to be most closely correlated with the fatal outcome of the elderly pneumonic patients. There were significant differences in the outcomes among three groups of the patients, those who were the prolonged bed-ridden, those with severe underlying diseases such as cancer and those treated as out-patients. The out patients showed the most favorable outcome and the prolonged bed-ridden patients the worst outcome. Approximately, 39% of the fatal cases were complicated with multiple organ failure. These results suggest that more important factors which affect the outcomes of pneumonia in the elderly may be not merely aging but the conditions of the host at onset of the disease.

Aged↗
PubMed2004

Host factors that affect Ty3 retrotransposition in Saccharomyces cerevisiae.

The retrovirus-like element Ty3 of Saccharomyces cerevisiae integrates at the transcription initiation region of RNA polymerase III. To identify host genes that affect transposition, a collection of insertion mutants was screened using a genetic assay in which insertion of Ty3 activates expression of a tRNA suppressor. Fifty-three loci were identified in this screen. Corresponding knockout mutants were tested for the ability to mobilize a galactose-inducible Ty3, marked with the HIS3 gene. Of 42 mutants tested, 22 had phenotypes similar to those displayed in the original assay. The proteins encoded by the defective genes are involved in chromatin dynamics, transcription, RNA processing, protein modification, cell cycle regulation, nuclear import, and unknown functions. These mutants were induced for Ty3 expression and assayed for Gag3p protein, integrase, cDNA, and Ty3 integration upstream of chromosomal tDNA(Val(AAC)) genes. Most mutants displayed differences from the wild type in one or more intermediates, although these were typically not as severe as the genetic defect. Because a relatively large number of genes affecting retrotransposition can be identified in yeast and because the majority of these genes have mammalian homologs, this approach provides an avenue for the identification of potential antiviral targets.

Adaptor Proteins, Signal Transducing↗
PubMed1988

Contribution of various host factors to resistance to experimentally induced bacterial endotoxemia in calves.

The reactions of 15 calves to IV administered bacterial lipopolysaccharide was investigated and was correlated with the capacity of 2 host defense mechanisms. The calves had a wide range of changes in clinical response, total WBC count, plasma lactate dehydrogenase (LD) activity, reaction to intradermally inoculated lipid A, and rectal temperature response. The early rectal temperature response of an individual calf was correlated with plasma LD activity, indicating a relationship between cell damage and fever. The concentration of antibody against lipid A at the time of lipopolysaccharide inoculation was negatively correlated with the rectal temperature changes recorded during endotoxemia, suggesting a protective ability of antibody. The capacity of a plasma inhibitor of lipopolysaccharide-mediated clotting of limulus amebocyte lysate was correlated with increases in plasma LD activity. Therefore, antibody to lipid A probably is involved in protection of cattle during endotoxemia, but the plasma lipopolysaccharide inhibitor actually may potentiate lipopolysaccharide toxicity.

Animals↗
PubMed2004

Microhomology-dependent end joining and repair of transposon-induced DNA hairpins by host factors in Saccharomyces cerevisiae.

The maize, cut-and-paste transposon Ac/Ds is mobile in Saccharomyces cerevisiae, and DNA sequences of repair products provide strong genetic evidence that hairpin intermediates form in host DNA during this transposition, similar to those formed for V(D)J coding joints in vertebrates. Both DNA strands must be broken for Ac/Ds to excise, suggesting that double-strand break (DSB) repair pathways should be involved in repair of excision sites. In the absence of homologous template, as expected, Ac excisions are repaired by nonhomologous end joining (NHEJ) that can involve microhomologies close to the broken ends. However, unlike repair of endonuclease-induced DSBs, repair of Ac excisions in the presence of homologous template occurs by gene conversion only about half the time, the remainder being NHEJ events. Analysis of transposition in mutant yeast suggests roles for the Mre11/Rad50 complex, SAE2, NEJ1, and the Ku complex in repair of excision sites. Separation-of-function alleles of MRE11 suggest that its endonuclease function is more important in this repair than either its exonuclease or Rad50-binding properties. In addition, the interstrand cross-link repair gene PSO2 plays a role in end joining hairpin ends that is not seen in repair of linearized plasmids and may be involved in positioning transposase cleavage at the transposon ends.

DNA↗
PubMed2004

Neurovirulence and host factors in flavivirus encephalitis--evidence from clinical epidemiology.

Japanese encephalitis virus (JEV) and West Nile virus (WNV) provide some of the most important examples of emerging zoonotic viral encephalitides. For these flaviviruses, only a small proportion of those infected develop clinical features, and these may range from a non-specific flu-like illness to a severe fatal meningoencephalitis, often with Parkinsonian features, or a poliomyelitis-like flaccid paralysis. The factors governing the clinical presentations, and outcome of flavivirus infections are poorly understood, but studies have looked at viral virulence determinants and the host immune response. Previous studies on JEV have suggested that the distribution of the four genotypes across Asia may relate to the differing clinical epidemiology (epidemic disease in the north, endemic disease in the south). However, new data based on the complete nucleotide sequence of a virus representing one of the oldest lineages, and phylogenetic analyses of all JEV strains for which genetic data are available, suggest that the distribution is best explained in terms of the virus' origin in the Indonesia-Malaysia region (where all genotypes have been found), and the spread of the more recent genotypes to new geographical areas. Clinical studies have shown that innate immunity, as manifested by interferon alpha levels, is important in JEV and other flaviviruses, but treatment with interferon alpha did not improve the outcome. A failure of the humoral immune response, is associated with death from encephalitis caused by JEV and WNV. Cellular immunity has been less well characterized, but CD8+ and CD4+ T cells are thought to be important.

Animals↗
PubMed1998

Cytokine kinetics and other host factors in response to pneumococcal pulmonary infection in mice.

There is a need for more insight into the pathogenesis of Streptococcus pneumoniae pneumonia, as the fatality rate associated with this disease remains high despite appropriate antibiotherapy. The host response to pneumococci was investigated after intranasal inoculation of CD1 mice with 10(7) log-phase CFU of bacteria. We identified five major pathogenesis steps from initial infection to death. In step 1 (0 to 4 h), there was ineffective phagocytosis by alveolar macrophages, with concurrent release of tumor necrosis factor alpha (TNF), interleukin-6 (IL-6), and nitric oxide (NO) in bronchoalveolar lavage (BAL) fluid, TNF, IL-6, and interleukin-1 alpha (IL-1) in lung tissues, and IL-6 in serum, which were associated with tachypnea and hemoconcentration. In step 2 (4 to 24 h), bacterial growth in alveoli and polymorphonuclear cell recruitment from bloodstream to lung tissue (high myeloperoxidase levels) to alveoli were associated with high release of all three cytokines and leukotriene B4 (LTB4) in tissue and BAL fluid, as well as transient spillover of IL-1 in serum. In step 3 (24 to 48 h), despite downregulation of TNF and IL-1 in BAL fluid and lungs, there was appearance of injury to alveolar ultrastructure, edema to interstitium, and increase in lung weight as well as regeneration of type II pneumocytes and increased secretion of surfactant; bacteria progressed from alveoli to tissue to blood, and body weight loss occurred. In step 4 (48 to 72 h), strong monocyte recruitment from blood to alveoli was associated with high NO release in tissue and BAL fluid, but there was also noticeable lymphocyte recruitment and leukopenia; bacteremia was associated with TNF and IL-6 release in blood and thrombocytopenia. In step 5 (72 to 96 h), severe airspace disorganization, lipid peroxidation (high malondialdehyde release in BAL fluid), and diffuse tissue damage coincided with high NO levels; there was further increase in lung weight and bacterial growth, loss in body weight, and high mortality rate. Delineation of the sequential steps that contribute to the pathogenesis of pneumococcal pneumonia may generate markers of evolution of disease and lead to better targeted intervention.

Animals↗
PubMed1975

Host factors in urinary infections.

To prevent the urologist from becoming simply a urinary tract mechanic we must develop more specific tests, perfect present tests and use these tests to elicit faulty mechanisms of host resistance of patients with urinary tract infections. We must then provide, from our research information, therapeutic measures to protect the faulty host from the inconvenience of recurrent significant bacteriuria and its sequelae.

Antibodies, Bacterial↗
PubMed1996

Human immunodeficiency virus-1 (HIV-1) gp120 superantigen-binding serum antibodies. A host factor in homosexual HIV-1 transmission.

HIV-1 gp120 is an immunoglobulin superantigen which can bind to preimmune serum Ig. We hypothesize that levels of such preimmune antibodies vary in the population and might affect host resistance or susceptibility to viral transmission. This study tests two predictions: (a) levels of preimmune anti-gpl20 Igs are a polymorphic trait; and, (b) these levels are correlated with resistance or susceptibility to HIV-1 transmission. The first prediction was confirmed in a longitudinal study of a low-risk seronegative population. In this group, levels of both endogenous anti-gpl20 IgM and IgG varied widely, but were characteristic and stable for each individual. The second prediction was addressed in a study of participants of the Multicenter AIDS Cohort Study, in which men "susceptible" and "resistant" to HIV infection were identified based on numbers of sexual partners and eventual seroconversion. Specimens consisted of archival sera obtained > 2 yr before seroconversion. Men in the susceptible population (low-risk seroconverters) were distinguished by low levels of anti-gpl20 IgG. We conclude that the level of preimmune anti-gpl20 IgG is a polymorphic population trait, and low levels are a potentially specific and significant factor in homosexual transmission of HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1981

The evolution of pulmonary cryptococcosis: clinical implications from a study of 41 patients with and without compromising host factors.

Over 14 years 41 patients were diagnosed as having pulmonary cryptococcosis. Cryptococcus neoformans remained localized to the lung in 12 cases and disseminated in the remaining 29. Thirty-four patients were compromised hosts. Disseminated disease developed in 28 of these 34, and four of these 28 patients with disseminated disease presented with concomitant pulmonary and meningeal infections. In all the remaining 24 central nervous system involvement developed 2 to 20 weeks after the finding of an abnormal chest roentgenogram. Seven patients were normal hosts, and in six of these cases disease remained localized to the lung. Four important conclusions were drawn from this study: pulmonary cryptococcosis is rarely considered in the differential diagnosis of an abnormal chest roentgenogram, thereby leading to missed diagnoses and therapeutic errors; the natural history of untreated pulmonary cryptococcosis in compromised hosts is extrapulmonic dissemination; compromised hosts with pulmonary cryptococcosis should receive antifungal therapy because of a high propensity for dissemination; and normal hosts in whom dissemination has been excluded generally do not need antifungal therapy.

Adolescent↗
PubMed1990

An analysis of the role of host factors in transcription antitermination in vitro by the Q protein of coliphage lambda.

We used two different approaches to study the requirement for Escherichia coli Nus factors for the activity of bacteriophage lambda late antiterminator Q. Using an in vitro coupled transcription-translation assay, based on Q-dependent synthesis of galactokinase from a pR'-tR'-galK template, we showed that mutations in the host nusB and nusE genes do not affect Q activity. A mutation in nusA (nusA1) only partially affects Q action at all temperatures tested. Defective Q function in the nusA1 mutant extract could be restored by the addition of pure NusA but not by excess Q. In a pure transcription system, measurement of the run-off transcript produced by Q-mediated suppression of tR' revealed that NusA is greatly stimulatory to Q activity, whereas NusB and S10, in the presence or absence of NusA, have no effect. Unidentified E. coli factor(s) present in an S30 extract efficiently suppress the natural pausing by RNA polymerase at +15, +16 of pR' without affecting Q activity. These results show that NusA is the only host protein that directly participates in Q function.

Bacterial Proteins↗
PubMed1996

A host factor that binds near the termini of hepatitis B virus pregenomic RNA.

The terminal regions of hepatitis B virus (HBV) pregenomic RNA (pgRNA) harbors sites governing many essential functions in the viral life cycle, including polyadenylation, translation, RNA encapsidation, and DNA synthesis. We have examined the binding of host proteins to a 170-nucleotide region from the 5' end of HBV pgRNA; a large portion of this region is duplicated at the 3' end of this terminally redundant RNA. By UV cross-linking labeled RNA to HepG2 cell extracts, we have identified a 65-kDa factor (p65) of nuclear origin which can specifically bind to this region. Two discrete binding sites were identified within this region; in vitro cross-competition experiments suggest that the same factor binds to both elements. One binding site (termed UBS) overlaps a portion of the highly conserved stem-loop structure (epsilon), while the other site (termed DBS) maps 35 nucleotides downstream of the hexanucleotide polyadenylation sequence. Both binding sites are highly pyrimidine rich and map to regions previously found to be important in the regulation of viral polyadenylation. However, functional analysis of mutant binding sites in vivo indicates that p65 is not involved in the polyadenylation of HBV pgRNA. Potential roles for the factor in viral replication in vivo are discussed.

Binding Sites↗
PubMedDate not supplied

Cumulative damage models of additional exposures and host factors.

Cumulative damage models represent a mathematically accurate conceptualized approach for the consideration of various problems of descriptive and analytical epidemiology. This study demonstrates the application of these models to situations where additional exposures, e.g., occupational exposures or smoking, overlay an always existing background exposure. Moreover, a way to incorporate host responses into the model is outlined, which is straightforward within this new approach, but has not been achieved by existing models to date. Based on empirical data, it is shown that some effects, which arise from additional exposures, can be understood as a kind of host response. This result contrasts with interpretations given by existing models and promises to open interesting discussion regarding which biological processes can be observed by epidemiological data.

Carcinogens↗
PubMed2000

Host factors influencing viral persistence.

With the aim of characterizing the antiviral immune response to a non-cytocidal virus, we studied the outcome of lymphocytic choriomeningitis virus infection in a number of gene knockout mouse strains. Two virus strains differing markedly in their capacity to spread and replicate inside the murine host were used. Our results reveal that very different outcomes may be observed depending on virus strain and immunocompetence of the host. Thus while CD4+ cells are not critical during the initial phase of virus control, infectious virus reappear in mice lacking CD4+ cells, B cells or CD40 ligand. Reappearance of virus is associated with impaired long-term CD8+ T-cell mediated immune surveillance, and the time to virus resurgence is inversely correlated to the replication rate of the virus. Our studies also reveal that interferon-gamma is a central cytokine, and depending on the rate of virus replication, mice lacking the ability to produce interferon-gamma may develop either a severe, mostly fatal, T-cell mediated wasting syndrome or a chronic infection characterized by long-term coexistence of antiviral cytotoxic T lymphocytes and infectious virus. Mathematical modelling indicates that these different outcomes may be explained in relatively simple mathematical terms. This suggests that modelling may be used as a means to predict critical host and virus parameters. Therefore, combining mathematical modelling with precise, quantitative, in vivo analyses looks to be a promising approach in addressing central quantitative issues in immunobiology.

Animals↗
PubMed2003

Immune reconstitution to cytomegalovirus after allogeneic hematopoietic stem cell transplantation: impact of host factors, drug therapy, and subclinical reactivation.

Reconstitution of cellular immunity by 3 months after hematopoietic stem cell transplantation (HSCT) is a critical determinant of the long-term success of the transplantation. We analyzed the factors affecting recovery of cytomegalovirus (CMV)-specific CD4+ and CD8+ function at 3 months after HSCT by univariate and multivariable analyses including source of stem cells (bone marrow vs peripheral blood stem cells [PBSCs]), age, sex, graft-versus-host disease (GVHD), steroid use, conditioning regimens, ganciclovir use, HLA matching, circulating CMV antigenemia, absolute CD4+ and CD8+ counts, and donor CMV serology. High-dose steroids and CD4+ count less than 100 x 10(9)/L were significant predictors of impaired CD4+ functional recovery in the multivariable analysis. High-dose steroids, bone marrow as a source of stem cells, and CD8+ count less than 50 x 10(9)/L were associated with impaired CD8+ function in the multivariable analysis. Steroids were found to impair both CD4+ and CD8+ function in a dose-dependent manner. In the absence of high-dose steroids, low-level subclinical CMV antigenemia was found to stimulate both CD4+ and CD8+ functional recovery in recipients of ganciclovir prophylaxis. There was no difference in immune reconstitution between those who received prophylactic ganciclovir versus antigenemia-guided pre-emptive therapy. Thus, absolute CD4+ and CD8+ counts less than 100 x 10(9)/L and 50 x 10(9)/L, respectively; bone marrow as the source of stem cells; and high-dose steroid use all predict delayed recovery of functional T-cell immunity at 3 months after transplantation. Subclinical CMV reactivation while on ganciclovir appears to be a potent stimulator of T-cell function. These findings have implications for vaccination and adoptive-immunotherapy strategies in this population.

Adolescent↗
PubMed1993

Host factors predisposing to anaerobic infections.

Factors that predispose to infection in general, of course, may predispose to infection with anaerobes. Included in this category are diabetes mellitus, neutropenia, hypogammaglobulinaemia, malignancy, splenectomy, collagen vascular disease, cytotoxic drug therapy, corticosteroid therapy and other immunosuppression. However, even with these situations there may be certain, more specific, associations: anaerobic cholecystitis and anaerobic osteomyelitis in diabetics, neutropenic colitis, and the increased incidence of local anaerobic infections associated with carcinoma of the lung, colon and uterus. Conditions that lead to decreased redox potential more specifically predispose to infection with anaerobes. Included in this category are obstruction and stasis, tissue anoxia, tissue destruction, vascular insufficiency, prior aerobic infection, burns, foreign body implantation, and calcium salts in a wound (in association with fractures). Other specific clinical situations that predispose to anaerobic infections include leukaemia; oral, gastrointestinal, and female pelvic surgery; trauma at other sites; childbirth; aspiration pneumonia; human and animal bites; and therapy with agents with poor activity against anaerobes (e.g. aminoglycosides, quinolones). AIDS patients appear to be predisposed to severe periodontal disease and its complications.

Bacteria, Anaerobic↗
PubMed2006

Exploring the role of insect host factors in the dynamics of Trypanosoma cruzi-Rhodnius prolixus interactions.

Members of the subfamily Triatominae, family Reduviidae, comprise a large number of insect species of which some are vectors of Trypanosoma cruzi, the causative agent of Chagas' disease. This article outlines research on the process of transformation and the dynamics of developmental stages of Trypanosoma cruzi in the triatomine insect hosts. Special attention is given to the interactions of parasites with gut molecules, and the gut environment, and with host developmental physiology and intestinal organization. The vector insect's permissiveness to Trypanosoma cruzi, which develops in the vector gut, largely depends on the host nutritional state, the parasite strain, trypanolytic compounds, digestive enzymes, lectins, resident bacteria in the gut and the endocrine system of the insect vector. Finally, the mechanisms of these interactions and their significance for Trypanosoma cruzi transmission are discussed.

Animals↗
PubMed1986

The influence of host factors on the outcome of a viral infection.

The clinician confronted with a patient that has an infectious disease, particularly one caused by a virus, faces a series of difficult problems: diagnostic confirmation of the infection, instituting appropriate therapy, duration of treatment, preventing secondary complications, and preventing transmission of the virus to susceptible animals. Yet, it is the complex relationship between the patient, as host to a pathogenic virus, the virus, and the environment that ultimately influences the clinical course of an infection. The ability to accurately prognose the outcome of any infection is, therefore, predicated on the clinician's awareness of biological and environmental variables that apply to the individual patient.

Aging↗