Pan-azole- and multi-fungicide-resistant Aspergillus fumigatus is widespread in the United States.

Aspergillus fumigatus is an important global fungal pathogen of humans. Azole drugs are among the most effective treatments for A. fumigatus infection. Azoles are also widely used in agriculture as fungicides against fungal pathogens of crops. Azole-resistant A. fumigatus has been increasing in Europe and Asia for two decades where clinical resistance is thought to be driven by agricultural use of azole fungicides. The most prevalent mechanisms of azole resistance in A. fumigatus are tandem repeats (TR) in the cyp51A promoter coupled with mutations in the coding region which result in resistance to multiple azole drugs (pan-azole resistance). Azole-resistant A. fumigatus has been isolated from patients in the United States (U.S.), but little is known about its environmental distribution. To better understand the distribution of azole-resistant A. fumigatus in the U.S., we collected isolates from agricultural sites in eight states and tested 202 isolates for sensitivity to azoles. We found azole-resistant A. fumigatus in agricultural environments in seven states showing that it is widespread in the U.S. We sequenced environmental isolates representing the range of U.S. sample sites and compared them with publicly available environmental worldwide isolates in phylogenetic, principal component, and ADMIXTURE analyses. We found worldwide isolates fell into three clades, and TR-based pan-azole resistance was largely in a single clade that was strongly associated with resistance to multiple agricultural fungicides. We also found high levels of gene flow indicating recombination between clades highlighting the potential for azole-resistance to continue spreading in the U.S.IMPORTANCEAspergillus fumigatus is a fungal pathogen of humans that causes over 250,000 invasive infections each year. It is found in soils, plant debris, and compost. Azoles are the first line of defense antifungal drugs against A. fumigatus. Azoles are also used as agricultural fungicides to combat other fungi that attack plants. Azole-resistant A. fumigatus has been a problem in Europe and Asia for 20 years and has recently been reported in patients in the United States (U.S.). Until this study, we did not know much about azole-resistant A. fumigatus in agricultural settings in the U.S. In this study, we isolated azole-resistant A. fumigatus from multiple states and compared it to isolates from around the world. We show that A. fumigatus which is resistant to azoles and to other strictly agricultural fungicides is widespread in the U.S.

Genetic characterization of the zoonotic parasite Ancylostoma caninum in the central and eastern United States.

Ancylostoma caninum is the most common nematode parasite of dogs in the United States. The present study aimed to describe the molecular epidemiology of A. caninum isolates from the central and eastern states of the United States using the partial mitochondrial cytochrome oxidase (cox1) gene and to compare them with those reported globally. We isolated eggs from faecal samples of dogs and characterized each isolate based on cox1 sequences. A total of 60 samples originating from Kansas, Iowa, New York, Florida and Massachusetts were included. 25 haplotypes were identified in the United States dataset with high haplotype diversity (0.904). Sequence data were compared to sequences from other world regions available in GenBank. Global haplotype analysis demonstrated 35 haplotypes with a haplotype diversity of 0.931. Phylogenetic and network analysis provide evidence for the existence of moderate geographical structuring of A. caninum haplotypes. Our results provide an updated summary of A. caninum haplotypes and data for neutral genetic markers with utility for tracking hookworm populations. Sequences have been deposited in GenBank (ON980650-ON980674). Further studies of isolates from other regions are essential to understand the genetic diversity of this parasite.

Molecular mechanisms for anthelmintic resistance in strongyle nematode parasites of veterinary importance.

Veterinarians rely on a relatively limited spectrum of anthelmintic agents to control nematode parasites in domestic animals. Unfortunately, anthelmintic resistance has been an emerging problem in veterinary medicine. In particular, resistance has emerged among the strongyles, a group of gastrointestinal nematodes that infect a variety of hosts that range from large herbivores to small companion animals. Over the last several decades, a great deal of research effort has been directed toward developing an understanding of the mechanisms conferring resistance against the three major groups of anthelmintics: macrocyclic lactones, benzimidazoles, and nicotinic agonists. Our understanding of anthelmintic resistance has been largely formed by determining the mechanism of action for each drug class and then evaluating drug-resistant nematode isolates for mutations or differences in expression of target genes. More recently, drug efflux pumps have been recognized for their potential contribution to anthelmintic resistance. In this mini-review, we summarize the evidence for mechanisms of resistance in strongyle nematodes.

Involvement of a putative intercellular signal-recognizing G protein-coupled receptor in the engulfment of Salmonella by the protozoan Tetrahymena.

In an effort to investigate the molecular basis of protozoa engulfment-mediated hypervirulence of Salmonella in cattle, we evaluated protozoan G protein-coupled receptors (GPCRs) as transducers of Salmonella engulfment by the model protozoan Tetrahymena. Our laboratory previously demonstrated that non-pathogenic protozoa (including Tetrahymena) engulf Salmonella and then exacerbate its virulence in cattle, but the mechanistic details of the phenomenon are not fully understood. GPCRs were investigated since these receptors facilitate phagocytosis of particulates by Tetrahymena, and a GPCR apparently modulates bacterial engulfment for the pathogenic protozoan Entamoeba histolytica. A database search identified three putative Tetrahymena GPCRs, based on sequence homologies and predicted transmembrane domains, that were the focus of this study. Salmonella engulfment by Tetrahymena was assessed in the presence of suramin, a non-specific GPCR inhibitor. Salmonella engulfment was also assessed in Tetrahymena in which expression of putative GPCRs was knocked-down using RNAi. A candidate GPCR was then expressed in a heterologous yeast expression system for further characterization. Our results revealed that Tetrahymena were less efficient at engulfing Salmonella in the presence of suramin. Engulfment was reduced concordantly with a reduction in the density of protozoa. RNAi-based studies revealed that knock-down of one the Tetrahymena GPCRs caused diminished engulfment of Salmonella. Tetrahymena lysates activated this receptor in the heterologous expression system. These data demonstrate that the Tetrahymena receptor is a putative GPCR that facilitates bacterial engulfment by Tetrahymena. Activation of the putative GPCR seemed to be related to protozoan cell density, suggesting that its cognate ligand is an intercellular signaling molecule.

Non-typhoidal Salmonella encephalopathy involving lipopolysaccharide in cattle.

This study assessed the involvement of lipopolysaccharide (LPS) in the non-typhoidal Salmonella encephalopathy (NTSE) caused by a unique isolate of Salmonella enterica serovar Saint-paul (SstpNPG). NTSE was prevented by genetic (deletion of murE) or pharmacologic (polymyxin) disruption of LPS on SstpNPG although the disruption of LPS did not deter brain penetration of the strain. This is the first study to demonstrate that LPS is involved in the manifestations of NTSE.

Identification and characterization of a pro-tumor necrosis factor-alpha-processing enzyme from the ADAM family of zinc metalloproteases.

Tumor necrosis factor-alpha (TNF) is initially expressed as a 26-kDa membrane-bound precusor protein (pro-TNF) that is shed proteolytically from the cell surface, releasing soluble 17-kDa TNF. We have identified human ADAM 10 (HuAD10) from THP-1 membrane extracts as a metalloprotease that specifically clips a peptide substrate spanning the authentic cleavage site between Ala76 and Val77 in pro-TNF. To confirm that HuAD10 has TNF processing activity, we cloned, expressed, and purified an active, truncated form of HuAD10. Characterization of recombinant HuAD10 (rHuAD10) suggests that this enzyme has many of the properties (i.e. substrate specificity, metalloprotease activity, cellular location) expected for a physiologically relevant TNF-processing enzyme.

Mechanisms of tumor necrosis factor-alpha (TNF-alpha) hyperalgesia.

Activation of immune cells by pathogens induces the release of a variety of proinflammatory cytokines, including IL-1 beta and TNF-alpha. Previous studies using IL-1 beta have demonstrated that this cytokine can alter brain function, resulting in a variety of 'illness responses' including increased sleep, decreased food intake, fever, etc. We have recently demonstrated that i.p. IL-1 beta also produces hyperalgesia and that this hyperalgesia (as well as most illness responses) is mediated via activation of subdiaphragmatic vagal afferents. The present series of studies were designed to provide an initial examination of the generality of proinflammatory cytokine-induced hyperalgesia by examining the effects of i.p. TNF-alpha on pain responsivity. These studies demonstrate that: (a) i.p. TNF-alpha produces dose-dependent hyperalgesia as measured by the tailflick test, (b) this hyperalgesia is mediated via the induced release of IL-1 beta, (c) hyperalgesia is mediated via activation of subdiaphragmatic vagal afferents, and (d) the effects of subdiaphragmatic vagotomy cannot be explained by a generalized depression of neural excitability.

Rabbit interleukin-1 receptor antagonist. Cloning, expression, functional characterization, and regulation during intestinal inflammation.

Genomic and cDNA clones for rabbit interleukin-1 receptor antagonist (IL-1ra) were isolate based on homology with the human, mouse, and rat IL-1ra gene. A partial genomic clone, obtained by screening a rabbit genomic library, contained coding sequences for the carboxyl-terminal 108 amino acids of rabbit IL-1ra. Two classes of cDNA for rabbit IL-1ra were obtained using RNA from inflamed rabbit colon tissue. One class of cDNA coded for a secreted form of IL-1ra, whereas the other coded for a putative intracellular form of rabbit IL-1ra. The latter form is similar to that isolated from human epithelial cells. A partially synthetic rabbit IL-1ra gene was constructed and expressed in Escherichia coli. The recombinant rabbit IL-1ra was purified to homogeneity by ion exchange chromatography. Its affinity was similar to that of human IL-1ra for the human and mouse type I IL-1 receptor. From the cDNA clone and the purified recombinant protein, specific probes were developed for measuring levels of rabbit IL-1ra mRNA and protein in normal and inflamed rabbit tissues. Unlike IL-1 alpha and IL-1 beta, IL-1RA mRNA and protein were present at detectable levels in normal rabbit colon. During the development of an experimental formalin-immune complex colitis, rabbit IL-1 alpha showed a dramatic increase in tissue levels, consistent with previous results; IL-1ra also increased 3-4-fold. Treatment of colitis rabbits with corticosteroids significantly suppressed neutrophil infiltration, corticosteroid treatment suppressed IL-1ra but not IL-1 alpha mRNA steady-state levels. Our observations demonstrate that IL-1 and IL-1ra synthesis is differentially regulated in healthy and inflamed intestinal tissue.

Human IL-1 receptor antagonist promoter. Cell type-specific activity and identification of regulatory regions.

To study the molecular mechanisms involved in transcriptional regulation of the human IL-1R antagonist (IL-1ra) we have isolated 1680-bp of 5'-flanking region DNA from the IL-1ra gene. This region of DNA was sequenced and cloned into the luciferase expression vector pA3Luc (pRA-1680.Luc) for use in gene transfer studies aimed at determining the cis-acting DNA elements required for IL-1ra expression. Sequence analysis of the IL-1ra promoter revealed a TATAA box at -26, with consensus sequences for possible NF-kB-, NFIL-1 beta A-, AP-1-, and CRE-binding sites located further upstream. When transfected into a variety of human and murine cell lines, the cloned IL-1ra promoter was preferentially active in those cell lines in which expression of the endogenous IL-1ra gene could be detected. The cloned promoter and the endogenous IL-1ra promoter utilized the same transcriptional start site. This promoter activity was LPS-inducible in the RAW 264.7 murine macrophage cell line. In the human monocytic cell line U937, IL-1ra promoter activity was inducible by LPS or PMA treatment, but the combination of LPS and PMA led to the greatest increase in promoter activity, identical to the pattern of expression of endogenous IL-1ra mRNA as detected by polymerase chain reaction analysis. A series of 5'-truncated promoter constructs having a common 3'-end at +27 were created to map potential cis-acting transcriptional elements important for full IL-1ra promoter activity. Removal of sequences between -294 and -148 led to a greater than 90% decrease in both unstimulated and LPS-induced promoter activity; further deletion to -85 led to an almost complete abrogation of promoter activity. These studies demonstrate that the cloned IL-1ra promoter behaves in a manner consistent with that of the endogenous gene. Two regions within the IL-1ra promoter are identified which are required for full promoter activity.

Interleukin 1 receptor antagonist is a member of the interleukin 1 gene family: evolution of a cytokine control mechanism.

Interleukin 1 receptor antagonist (IL-1ra) is a protein that binds to the IL-1 receptor and blocks the binding of both IL-1 alpha and -beta without inducing a signal of its own. Human IL-1ra has some sequence identity to human IL-1 beta, but the evolutionary relationship between these proteins has been unclear. We show that the genes for human, mouse, and rat IL-1ra are similar to the genes for IL-1 alpha and IL-1 beta in intron-exon organization, indicating that gene duplication events were important in the creation of this gene family. Furthermore, an analysis of sequence comparisons and mutation rates for IL-1 alpha, IL-1 beta, and IL-1ra suggests that the duplication giving rise to the IL-1ra gene was an early event in the evolution of the gene family. Comparisons between the mature sequences for IL-1ra, IL-1 alpha, and IL-1 beta suggest that IL-1ra has a beta-stranded structure like to IL-1 alpha and IL-1 beta, consistent with the three proteins being related. The N-terminal sequences of IL-1ra appear to be derived from a region of the genome different than those of IL-1 alpha and IL-1 beta, thus explaining their different modes of biosynthesis and suggesting an explanation for their different biological activities.

Expression of the secretory leukoprotease inhibitor gene in epithelial cells.

The secretory leukoprotease inhibitor (SLPI) gene codes for a 12-kD protein that within the lung protects the airway epithelium from neutrophil elastase. Screening of 228 alleles in 114 individuals for sequence differences by RNase protection of genomic DNA revealed no detectable polymorphisms in SLPI gene exons II-IV. SLPI gene expression in the lung was demonstrated by identifying SLPI mRNA transcripts in bronchial epithelial cells freshly isolated from normals. Cell lines derived from mucosal surfaces (HS-24 bronchial squamous cell carcinoma, HeLa cervical carcinoma) actively transcribe the SLPI gene and contain SLPI mRNA transcripts, while lung fibroblasts demonstrate no evidence of SLPI gene expression. SLPI mRNA transcripts appear to be relatively stable, with mRNA levels only mildly affected by inhibition of RNA synthesis. Chromatin DNA of HS-24 cells demonstrates two DNase I hypersensitivity sites within the 5' flanking region of exon I of the SLPI gene, whereas fibroblast chromatin has no DNase I accessible sites in the same region. Further analysis of the 5' flanking region demonstrated two contiguous transcription start sites, CAAT and TATA boxes, and several potential regions of known DNA binding proteins. Overall, the SLPI gene appears to be a relatively nonpolymorphic, stable gene that is constitutively expressed at specific tissue sites, but has the potential to be modulated at both the transcriptional and posttranscriptional levels.

A second tumor necrosis factor receptor gene product can shed a naturally occurring tumor necrosis factor inhibitor.

An inhibitor of tumor necrosis factor (TNF) has been isolated from the human histiocytic lymphoma cell line U-937 that is capable of inhibiting both TNF-alpha and TNF-beta. Protein sequencing has verified that it is distinct from a previously described TNF inhibitor that is a soluble fragment of a TNF receptor molecule (TNFrI). The cDNA sequence of this second TNF inhibitor clone suggests that it is also a soluble fragment of a TNF receptor. Expression of this cDNA sequence in COS-7 cells verified that it encodes a receptor for TNF-alpha (TNFrII) that can give rise to a soluble inhibitor of TNF-alpha, presumably through proteolytic cleavage. The extracellular domain of TNFrII has significant homology with that of TNFrI and these two receptors share a striking conservation of cysteine residue alignment with the extracellular domain of the nerve growth factor receptor. These three receptor molecules are therefore members of a family of polypeptide hormone receptors.

Primary structure and functional expression from complementary DNA of a human interleukin-1 receptor antagonist.

Human monocytes induced with adherent IgG secrete an interleukin-1 receptor antagonist which could be important for the in vivo regulation of IL-1 activity. A complementary DNA for this molecule has been isolated from a human monocyte library. Analysis of monocyte RNA indicates that the gene is transcriptionally regulated. The sequence of the receptor antagonist indicates that it is structurally similar to IL-1 beta. Expression of the cDNA in Escherichia coli yields IL-1 receptor antagonist activity.

Cloning, characterization, and expression of a human insulin-like growth factor binding protein.

Insulin-like growth factors (IGFs) bind to specific proteins present in extracellular fluids. One of these binding proteins (IGF-BP) was purified from human amniotic fluid and was shown to potentiate the effects of IGF-I in vitro (10). In these studies, a polyclonal antibody to this protein was used to isolate a cDNA clone from a human decidua library. This clone encodes a polypeptide of 25,832 daltons that includes the sequences of 9 tryptic peptides that had been prepared from the purified IGF-BP. The protein has 15 cysteines that are clustered at the amino and carboxy ends of the molecule. The protein has an RGD sequence near its C-terminus, which may account for its ability to attach to cells and to potentiate the biological actions of IGF-I.

A form of human basic fibroblast growth factor with an extended amino terminus.

The amino acid sequence of a human placental bFGF was determined by a combination of protein and cDNA sequencing. The placental bFGF consists of 157 amino acid residues with a calculated molecular weight of 17,464 and is highly homologous to bovine pituitary bFGF. The human protein contains an amino terminal extension when compared to the sequence established for bovine bFGF (Esch et al., 1985) and to the sequence of the predicted translation product based on human bFGF cDNA clones (Abraham et al., 1986).

Isolation and sequence of a human gene encoding a potent inhibitor of leukocyte proteases.

We report the isolation of the human gene encoding an inhibitor of neutrophil elastase and cathepsin G. We have sequenced the gene and a cDNA clone isolated from human parotid tissue. The protein encoded by this gene appears to contain two functional domains, one having a trypsin inhibitory site and the other an elastase inhibitory site. The two-domain structure of the protein is reflected in the organization of the gene, with each domain represented by a separate exon. We have also noted that the intervening sequence separating the trypsin-inhibitor-exon and the elastase-inhibitor-exon is flanked by eleven base-pair direct repeats, suggesting that this intron may have been generated by a transposition-type event.