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Results for “host:pathogen interactions”

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PubMed2002

Microbial beta-glucosidases: cloning, properties, and applications.

Beta-glucosidases constitute a major group among glycosylhydrolase enzymes. Out of the 82 families classified under glycosylhydrolase category, these belong to family 1 and family 3 and catalyze the selective cleavage of glucosidic bonds. This function is pivotal in many crucial biological pathways, such as degradation of structural and storage polysaccharides, cellular signaling, oncogenesis, host-pathogen interactions, as well as in a number of biotechnological applications. In recent years, interest in these enzymes has gained momentum owing to their biosynthetic abilities. The enzymes exhibit utility in syntheses of diverse oligosaccharides, glycoconjugates, alkyl- and aminoglucosides. Attempts are being made to understand the structure-function relationship of these versatile biocatalysts. Earlier reviews described the sources and properties of microbial beta-glucosidases, yeast beta-glucosidases, thermostable fungal beta-glucosidase, and the physiological functions, characteristics, and catalytic action of native beta-glucosidases from various plant, animal, and microbial sources. Recent efforts have been directed towards molecular cloning, sequencing, mutagenesis, and crystallography of the enzymes. The aim of the present article is to describe the sources and properties of recombinant beta-glucosidases, their classification schemes based on similarity at the structural and molecular levels, elucidation of structure-function relationships, directed evolution of existing enzymes toward enhanced thermostability, substrate range, biosynthetic properties, and applications.

Biotechnology↗

PubMed2026

Mössbauer spectroscopy in drug discovery: revealing Fe- and Fe-S cluster dependent targets.

INTRODUCTION: Iron- and iron-sulfur cluster (Fe-S)-containing proteins are essential for diverse biological processes, including electron transfer, genome maintenance, metabolism, cellular signaling, and host-pathogen interactions. Despite their broad biological importance and growing links to human disease, Fe-S cluster-dependent proteins remain underexplored as therapeutic targets, largely because it is difficult to define their metal-dependent chemistry using conventional biochemical, spectroscopic, and structural approaches. AREAS COVERED: This review examines how Mössbauer spectroscopy can be integrated into workflows for metalloprotein characterization, target validation, and drug discovery. Using representative Fe-S cluster-containing proteins, the practical considerations for implementing Mössbauer spectroscopy are outlined, including 57Fe-enriched expression, sample preparation, and spectroscopic analysis. Two case studies of experimentally challenging viral Fe-S cluster proteins are then highlighted, the Hepatitis B virus X protein and the Porcine Reproductive and Respiratory Syndrome Virus Nsp1α protease, which demonstrate how direct characterization of metal cofactors can reveal previously unrecognized therapeutic avenues. Relevant literature published through March 2026 was identified using PubMed and Google Scholar with keywords related to Mössbauer spectroscopy, iron-sulfur proteins, viral metalloproteins, and drug discovery. EXPERT OPINION: As drug discovery increasingly seeks to exploit metal-dependent biology, Mössbauer spectroscopy will play an important role in identifying cryptic metalloproteins, defining their native states, and uncovering Fe- and Fe-S cluster-dependent targets. Mössbauer spectroscopy can also be complementary, and integrated with structural and AI-driven approaches to answer emerging challenges in medicinal chemistry.

Humans↗

PubMed2000

Micronutrients and infectious diseases: thoughts on integration of mechanistic approaches into micronutrient research.

Results of field and laboratory studies provide convincing evidence that micronutrient deficiencies contribute to the mortality and morbidity of infectious diseases. Despite encouraging results in large trials, understanding the mechanisms by which micronutrients contribute to the outcome of the encounter between an individual and an infectious agent requires additional hypothesis-driven research. Presumably, such understanding should lead to translational studies with targeted nutritional therapy. Although these mechanistic studies are varied and complex, they must be done systematically and should include examination of the mechanisms by which micronutrients affect host-pathogen interactions, development of appropriate animal models and reliable methods for the assessment of micronutrient levels, and translation of the results of basic research findings into clinical studies. Moving the frontiers of micronutrient research from the laboratory to the field will be challenging. However, sound scientific research should lead toward better human health.

Communicable Diseases↗

PubMed2001

Evidence for superantigen involvement in severe group a streptococcal tissue infections.

Host-pathogen interactions were studied in tissue biopsy samples from patients with severe invasive group A streptococcus (GAS) infections. Skin, subcutaneous tissue, and fascia biopsy samples were divided into clinical grade 1 (no evidence of inflammation [n=7]) or clinical grade 2 (inflamed tissue--erythema and edema including cellulitis, fasciitis, and necrotizing fasciitis [n=24]). In situ imaging demonstrated significantly higher bacterial load in biopsy samples of higher clinical grade (P<.05), and the bacterial load correlated with the in vivo expression of the superantigen streptococcal pyrogenic exotoxin F (P<.02). Increased expression of the interleukin-1 cytokines and significantly higher expression of tumor necrosis factor-beta, interferon-gamma, and the homing receptors CC chemokine receptor 5, CD44, and cutaneous lymphocyte-associated antigen (P<.002-.05) were observed in biopsy samples of higher clinical grade. Thus, the cytokine profile at the local site of infection mimics that of a typical superantigen cytokine response. The findings of this study demonstrate a critical role for superantigens and Th1 cytokines in GAS tissue infections.

Bacterial Proteins↗

PubMed2002

Epidemiological correlates of virulence genotype and phylogenetic background among Escherichia coli blood isolates from adults with diverse-source bacteremia.

Associations of virulence genotype and phylogenetic background with epidemiological factors (primary source of bacteremia, host compromise status, and hospital versus community origin) were assessed among 182 Escherichia coli blood isolates from adults with diverse-source bacteremia in comparison with fecal controls from the E. coli Reference collection. A continuum of virulence was found, from urinary and pulmonary source bacteremia isolates (high virulence), through "other" or unknown source bacteremia isolates (intermediate virulence), to fecal isolates (low virulence), with a corresponding graded phylogenetic distribution from predominantly group B2 to predominantly groups A and B1. Associations of bacterial traits with clinical factors varied considerably, depending on subgroup and statistical method. However, certain putative virulence genes (including several "nontraditional" markers, such as pathogenicity island-associated malX) repeatedly emerged as significant epidemiological predictors, which provided evidence of their possible relevance in host-pathogen interactions and hence as potential targets for preventive interventions against extraintestinal infections due to E. coli.

Adult↗

PubMed2004

Progress toward characterization of the group A Streptococcus metagenome: complete genome sequence of a macrolide-resistant serotype M6 strain.

We describe the genome sequence of a macrolide-resistant strain (MGAS10394) of serotype M6 group A Streptococcus (GAS). The genome is 1,900,156 bp in length, and 8 prophage-like elements or remnants compose 12.4% of the chromosome. A 8.3-kb prophage remnant encodes the SpeA4 variant of streptococcal pyrogenic exotoxin A. The genome of strain MGAS10394 contains a chimeric genetic element composed of prophage genes and a transposon encoding the mefA gene conferring macrolide resistance. This chimeric element also has a gene encoding a novel surface-exposed protein (designated "R6 protein"), with an LPKTG cell-anchor motif located at the carboxyterminus. Surface expression of this protein was confirmed by flow cytometry. Humans with GAS pharyngitis caused by serotype M6 strains had antibody against the R6 protein present in convalescent, but not acute, serum samples. Our studies add to the theme that GAS prophage-encoded extracellular proteins contribute to host-pathogen interactions in a strain-specific fashion.

Alleles↗

PubMed2004

Paradoxical inflammatory reaction during treatment of Cryptococcus neoformans var. gattii meningitis in an HIV-seronegative woman.

A human immunodeficiency virus (HIV)-seronegative woman was admitted to the hospital with postpartum onset Cryptococcus neoformans var. gattii meningitis and markedly increased intracranial pressure. A poor initial response to antifungal therapy was followed, 2 months after hospital admission, by severe acute meningeal and cerebral inflammation and clearance of yeast cells from cerebrospinal fluid. This first reported case of paradoxical inflammatory reaction to C. neoformans illustrates important aspects of the host-pathogen interaction and highlights possible effects of immunomodulatory therapies.

Adolescent↗

PubMed2005

Genome sequence of a serotype M28 strain of group a streptococcus: potential new insights into puerperal sepsis and bacterial disease specificity.

Puerperal sepsis, a major cause of death of young women in Europe in the 1800s, was due predominantly to the gram-positive pathogen group A Streptococcus. Studies conducted during past decades have shown that serotype M28 strains are the major group A Streptococcus organisms responsible for many of these infections. To begin to increase our understanding of their enrichment in puerperal sepsis, we sequenced the genome of a genetically representative strain. This strain has genes encoding a novel array of prophage virulence factors, cell-surface proteins, and other molecules likely to contribute to host-pathogen interactions. Importantly, genes for 7 inferred extracellular proteins are encoded by a 37.4-kb foreign DNA element that is shared with group B Streptococcus and is present in all serotype M28 strains. Proteins encoded by the 37.4-kb element were expressed extracellularly and in human infections. Acquisition of foreign genes has helped create a disease-specialist clone of this pathogen.

Antigens, Bacterial↗

PubMedDate not supplied

Histopathology of childhood pneumonia in developing countries.

Acute lower respiratory infection in children is a major cause of morbidity and mortality in developing countries. Viral and bacterial agents incite characteristic host responses at the level of the bronchi, bronchioles, alveolar walls, and air spaces that correlate with the clinical course. A systematic review of histopathologic features will enhance the understanding of the pathogenetic mechanisms and cofactors that influence the disease process, particularly how tissue injury may be influenced by nutritional status and access to antibiotics. Research priorities include immunologic assessment, micronutrient assays, and standardized autopsies in developing countries. DNA probes for organisms and immunocytochemical identification of cell markers in tissue promise a new era in microscopic visualization of pathogen-host interactions. International collaborative research between ministries of public health and medical universities must be encouraged as a means of providing technical assistance and of advancing new knowledge. Systematic standardized autopsy studies from multiple geographic areas may help define pathologic mechanisms, monitor the natural history of disease, and evaluate interventions in diverse populations.

Acute Disease↗

PubMed1993

Biological roles of oligosaccharides: all of the theories are correct.

Many different theories have been advanced concerning the biological roles of the oligosaccharide units of individual classes of glycoconjugates. Analysis of the evidence indicates that while all of these theories are correct, exceptions to each can also be found. The biological roles of oligosaccharides appear to span the spectrum from those that are trivial, to those that are crucial for the development, growth, function or survival of an organism. Some general principles emerge. First, it is difficult to predict a priori the functions a given oligosaccharide on a given glycoconjugate might be mediating, or their relative importance to the organism. Second, the same oligosaccharide sequence may mediate different functions at different locations within the same organism, or at different times in its ontogeny or life cycle. Third, the more specific and crucial biological roles of oligosaccharides are often mediated by unusual oligosaccharide sequences, unusual presentations of common terminal sequences, or by further modifications of the sugars themselves. However, such oligosaccharide sequences are also more likely to be targets for recognition by pathogenic toxins and microorganisms. As such, they are subject to more intra- and inter-species variation because of ongoing host-pathogen interactions during evolution. In the final analysis, the only common features of the varied functions of oligosaccharides are that they either mediate 'specific recognition' events or that they provide 'modulation' of biological processes. In so doing, they generate much of the functional diversity required for the development and differentiation of complex organisms, and for their interactions with other organisms in the environment.

Glycoconjugates↗

PubMed1997

Digalactosyl diacylglycerols, plant glycolipids rarely found in bacteria, are major membrane components of bacteroid forms of Bradyrhizobium japonicum.

The membrane lipids of free living and bacteroid forms of Bradyrhizobium japonicum, obtained from nodules occupied by both typed and untyped bacteria, were isolated and characterized by a combination of NMR spectroscopy, mass spectrometry, and other chemical and physical methods. These studies indicated that both the free living and bacteroid forms of this organism contain glycolipids almost exclusively of the type found in plant cells. In the bacteroid forms, there was a dramatic shift towards the synthesis of digalactosyl diacylglycerol as the major lipid. This glycolipid has rarely been found outside of the plant kingdom and photosynthetic bacteria, and its occurrence in the bacteroid form of a plant symbiont is therefore remarkable. The presence of plant cell and organelle contaminants in the bacteroid preparations was ruled out by scanning electron microscopy, Southern blot analyses for plant DNA using specific gene probes, and chemical analyses for plant marker steroids, steroid glycosides, and cerebrosides. Digalactosyl diacylglycerol is not found in the plasma membrane of plant cells (of which the peribacteroid membrane is an extension) but is thought to be restricted to plastids. This result follows our earlier finding that the other predominant plant glycolipid, sulfoquinivosyl diacylglycerol, is a membrane component of fast growing Rhizobia and is found even when cells are cultivated in free culture where there is no question of plant contamination. The near absence of these lipids in the membranes of bacteria outside of this special group of organisms and photosynthetic bacteria suggests that the trait could have been passed on through gene transfer from plants to the bacteria at some point during the development of their symbiotic relationship. In the case of digalactosyl diacylglycerol, there is also the possibility that some common biosynthetic intermediates are used by both the plant and the bacteria. This is a striking parallel with some host-pathogen interactions.

Carbohydrate Conformation↗

PubMed2006

Galectin-1: a small protein with major functions.

Galectins are a family of carbohydrate-binding proteins with an affinity for beta-galactosides. Galectin-1 (Gal-1) is differentially expressed by various normal and pathological tissues and appears to be functionally polyvalent, with a wide range of biological activity. The intracellular and extracellular activity of Gal-1 has been described. Evidence points to Gal-1 and its ligands as one of the master regulators of such immune responses as T-cell homeostasis and survival, T-cell immune disorders, inflammation and allergies as well as host-pathogen interactions. Gal-1 expression or overexpression in tumors and/or the tissue surrounding them must be considered as a sign of the malignant tumor progression that is often related to the long-range dissemination of tumoral cells (metastasis), to their dissemination into the surrounding normal tissue, and to tumor immune-escape. Gal-1 in its oxidized form plays a number of important roles in the regeneration of the central nervous system after injury. The targeted overexpression (or delivery) of Gal-1 should be considered as a method of choice for the treatment of some kinds of inflammation-related diseases, neurodegenerative pathologies and muscular dystrophies. In contrast, the targeted inhibition of Gal-1 expression is what should be developed for therapeutic applications against cancer progression. Gal-1 is thus a promising molecular target for the development of new and original therapeutic tools.

Amino Acid Sequence↗

PubMed2004

Positive selection on the human genome.

Positive selection has undoubtedly played a critical role in the evolution of Homo sapiens. Of the many phenotypic traits that define our species--notably the enormous brain, advanced cognitive abilities, complex vocal organs, bipedalism and opposable thumbs--most (if not all) are likely the product of strong positive selection. Many other aspects of human biology not necessarily related to the 'branding' of our species, such as host-pathogen interactions, reproduction, dietary adaptation and physical appearance, have also been the substrate of varying levels of positive selection. Comparative genetics/genomics studies in recent years have uncovered a growing list of genes that might have experienced positive selection during the evolution of human and/or primates. These genes offer valuable inroads into understanding the biological processes specific to humans, and the evolutionary forces that gave rise to them. Here, we present a comprehensive review of these genes, and their implications for human evolution.

Genome, Human↗

PubMed2026

Host life-history strategy is a critical determinant of virulent phage infection propensity.

Bacteriophages shape microbial communities through two major lifestyles: virulent (obligately lytic) and temperate (capable of lysogeny). Prevailing phage ecology frameworks focus on how environmental conditions, host density, and physiological state modulate infection modality. This perspective overlooks how host traits exert selective pressure on the distribution of virulent and temperate lifestyles across bacterial species, which limits understanding of phage ecology. To address this critical knowledge gap, we adopt a host-centric, trait-based perspective and use 5821 complete bacterial genomes to build a host life-history space predominantly defined by genome size, metabolic capacity, and growth rate potential. After mapping phage lifestyle association signals, prophage burden formed a continuous gradient across this space. Also, virulent phage association was positively correlated with prophage burden, revealing a nested structure of lifestyle signals. Functional trait analysis identified enrichment of resource-acquisition modules underlying both temperate and virulent associations. Overall, these findings indicate that phage lifestyle is significantly influenced by host life-history strategies, highlighting fast-growing, metabolically versatile hosts as favorable targets for virulent phage isolation and biocontrol applications.

Bacteriophages↗

PubMed2002

(n-3) Fatty acids and infectious disease resistance.

The current view of the manner in which (n-3) polyunsaturated fatty acids (PUFA) affect the immune system is centered on their ability to alter cytokine production and secondarily to diminish eicosanoid biosynthesis. The purpose of this article is to review the evidence that (n-3) PUFA affect host infectious disease resistance. Although there have been a few human clinical trials involving (n-3) PUFA and human infectious disease, the data are equivocal and the study designs confounded by the simultaneous inclusion of other immunonutrients (i.e., arginine and nucleotides) with the (n-3) PUFA. Thus, this review focuses on animal feeding trials that include an in vivo challenge of the host with a live infectious agent. Host survival and pathogen clearance are the most common end points measured in these studies. The data suggest that (n-3) PUFA can both improve and impair host resistance to a number of pathogens. However, the data are still quite limited in breadth and depth. For those pathogens for which data exist, the number of published studies in general does not exceed two or three. Emphasis is placed on defining important microbiological and immunological differences in various host-pathogen interactions that might help explain the incongruity in the findings published to date. The authors believe that direct examination of (n-3) PUFA on human infectious disease resistance is warranted.

Animals↗

PubMed2006

Sequence diversity at the proximal 14q32.1 SERPIN subcluster: evidence for natural selection favoring the pseudogenization of SERPINA2.

The superfamily of serine protease inhibitors (SERPINs) plays a key role in controlling the activity of proteinases in diverse biological processes. alpha1-antitrypsin (SERPINA1), the most studied member of this family, is encoded by a gene located within the proximal 14q32.1 SERPIN subcluster, together with the highly homologous alpha1-antitrypsin-like sequence (SERPINA2), which was previously proposed to be a pseudogene. Here, we performed a resequencing study encompassing both SERPINA1 and SERPINA2 as well as the adjacent gene coding for corticosteroid-binding globulin (SERPINA6) in samples from Europe and West Africa. In the African sample, we found that a common haplotype carrying a 2-kb deletion in the SERPINA2 gene is associated with remarkable long-range homozygozity as if it was quickly driven to high frequency by natural selection acting on an advantageous variant. An analysis of the HapMap Phase I data for the Yoruba sample confirmed that variation in this subcluster carries a strong signal of positive selection. We also show that the SERPINA2 gene is expressed and probably encodes a functional SERPIN. Finally, comparisons with orthologous sequences in nonhuman primates showed that SERPINA2 is present in some great apes, but in chimpanzees it was lost by a deletion event independent from that observed in humans. In agreement with the "less is more" hypothesis, we propose that loss of SERPINA2 is an ongoing process associated with a selective advantage during recent primate evolution, possibly because of a role in fertility or in host-pathogen interactions.

Africa↗

PubMed1994

Identifying differences in mRNA expression by representational difference analysis of cDNA.

Detection of differentially regulated genes has been severely hampered by technical limitations. In an effort to overcome these problems, the PCR-coupled subtractive process of representational difference analysis (RDA) [Lisitsyn, N. et al. (1993) Science 259, 946-951] has been adapted for use with cDNA. In a model system, RAG-1 and RAG-2, the genes responsible for activating V(D)J recombination, were identified in a genomic transfectant by cDNA RDA in a small fraction of the time taken by conventional means. The system was also modified to eliminate expected difference products to facilitate the identification of novel genes. Additional alterations to the conditions allowed isolation of differentially expressed fragments. Several caffeine up-regulated clones were obtained from the pre-B cell line 1-8, including IGF-1B, and a predicted homologue of the natural killer cell antigen, NKR-P1. The approach was found to be fast, extremely sensitive, reproducible, and predominantly lacked false positives. cDNA RDA has the capacity and adaptability to be applied to a wide range of biological problems, including the study of single gene disorders, characterization of mutant and complemented cell types, developmental or post-event expression time courses, and examination of pathogen-host interactions.

Animals↗

PubMed2004

Identification of genes with fast-evolving regions in microbial genomes.

Complete sequences of multiple strains of the same microbial species provide an invaluable source for studying the evolutionary dynamics between orthologous genes over a relatively short time scale. Usually the intensity of the selection pressure is inferred from a comparison between the nonsynonymous substitution rate and the synonymous substitution rate. In this paper, we propose an alternative method for detecting genes with one or more fast-evolving regions from pairwise comparisons of orthologous genes. Our method looks for regions with overrepresented nonsynonymous mutations along the alignment, and requires a higher nonsynonymous evolution rate in those regions than the neutral evolution rate. It identifies gene targets under intensive selection pressure that are not detected from the conventional rate comparison analysis. For those identified genes with known annotations, most of them have a clear role in processes such as bacterial defense and host-pathogen interactions. Gene sets reported from our method provide a measure of the phenotypic divergence between two closely related genomes.

Amino Acid Sequence↗