Proteome characterization of the culture supernatant of Mycobacterium bovis in different growth stages

This study aimed to identify proteins secreted by Mycobacterium bovis into culture medium at different stages of bacterial growth. A field strain of M. bovis was grown in Middlebrook 7H9 media and culture supernatant was collected at three-time points representing three different phases of growth (early exponential, late exponential, and stationary phases). Supernatants were double filtered, digested by trypsin and analyzed by LC-MS/MS. The study found 15, 21, and 16 proteins in early, mid and late growth phases, respectively. In total, 22 proteins were identified, 18 of which were reported or predicted to have a cell wall or extracellular localization. To our knowledge, this is the first study to identify proteins secreted into the culture medium by a field strain of M. bovis in three different stages of growth. The dataset generated here provides candidate proteins with the potential for the development of serological diagnostic reagents or vaccine for bovine tuberculosis. Data are available via ProteomeXchange with identifier PXD017817.

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Identifying extracellular proteins produced by M. bovis using mass spectrometry.

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Culture supernatant proteins secreted in three different stages of bacterial growth.

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Proteins were secreted from live bacteria and heat-killing was omitted.

Dysregulation of Ephrin receptor and PPAR signaling pathways in neural progenitor cells infected by Zika virus

Zika virus (ZIKV) infection is a serious public threat with cases reported in about 70 countries and territories. One of the most serious consequences of ZIKV infection is congenital microcephaly in babies. Congenital microcephaly has been suggested to result from infection of neural progenitor cells (NPCs) in the developing fetal brain. However, the molecular and cellular mechanisms underlying microcephaly development remains to be fully elucidated. In this study, we employed quantitative proteomics to determine protein expression profile that occur during viral replication in NPCs. Bioinformatics analysis of the protein expression changes resulted in the identification of a wide range of cell signaling pathways. Specifically, pathways involved in neurogenesis and embryonic development were markedly altered, along with those associated with cell cycle, apoptosis, lipid metabolism and oxidative stress. Notably, the differential regulation of Ephrin Receptor and PPAR signaling pathways, as revealed by quantitative proteomics and validated by qPCR array, underscores the need to explore these pathways in disease development. Collectively, these results indicate that ZIKV-induced pathogenesis involves complex virus-host reactions; the findings reported here could help shed light on the mechanisms underlying ZIKV-induced microcephaly and ZIKV replication in NPCs.

A comprehensive proteomics profiling identifies NRP1 as a novel identity marker of human bone marrow mesenchymal stromal cell-derived small extracellular vesicles

BACKGROUND

Clinical applications have shown extracellular vesicles (EVs) to be a major paracrine effector in therapeutic responses produced by human mesenchymal stromal/stem cells (hMSCs). As the regenerative capacity of EVs is mainly ascribed to the transfer of proteins and RNA composing its cargo, and to the activity attributed by the protein surface markers, we sought to profile the protein composition of small EVs released from hMSCs to identify hMSC-EV biomarkers with potential clinical relevance.

METHODS

Small EVs were produced and qualified from five human bone marrow MSC donors at low passage following a 48-h culture in exosome-depleted medium further processed by steps of centrifugation, filtration, and precipitation. Quantitative proteomic analysis comparing the protein profile of the EVs released from hMSCs and their parental cell was conducted using tandem mass tag labeling combined to mass spectrometry (LC-MS/MS) to identify enriched EV protein markers.

RESULTS

Nanoparticle tracking analysis showed no differences in the EV concentration and size among the five hMSC donors (1.83 × 1010 ± 3.23 × 109/mL), with the mode particle size measuring at 109.3 ± 5.7 nm. Transmission electron microscopy confirmed the presence of nanovesicles with bilayer membranes. Flow cytometric analysis identified commonly found exosomal (CD63/CD81) and hMSC (CD105/CD44/CD146) markers from released EVs in addition to surface mediators of migration (CD29 and MCSP). Quantitative proteomic identified 270 proteins significantly enriched by at least twofold in EVs released from hMSCs as compared to parental hMSCs, where neuropilin 1 (NRP1) was identified among 21 membrane-bound proteins regulating the migration and invasion of cells, as well as chemotaxis and vasculogenesis. Validation by western blot of multiple batches of EVs confirmed consistent enrichment of NRP1 in the nanovesicles released from all five hMSC donors.

CONCLUSION

The identification and verification of NRP1 as a novel enriched surface marker from multiple batches of EVs derived from multiple hMSC donors may serve as a biomarker for the assessment and measurement of EVs for therapeutic uses.

PD-1 of Sigmodon hispidus: Gene identification, characterization and preliminary evaluation of expression in inactivated RSV vaccine-induced enhanced respiratory disease

Sigmodon hispidus or cotton rat is an excellent animal model for studying human infections of respiratory viruses including respiratory syncytial virus (RSV), which is the leading cause of hospitalization in infants and causes high rates of infection in the elderly and immunocompromised patient populations. Despite several decades of research, no vaccine has been licensed whereas inactivated vaccines have been shown to induce severe adverse reaction in a clinical trial, with other forms of RSV vaccine also found to induce enhanced disease in preclinical animal studies. While arguably the cotton rat is the best small animal model for evaluation of RSV vaccines and antivirals, many important genes of the immune system remain to be isolated. Programmed cell death-1 (PD-1) plays an integral role in regulating many aspects of immunity by inducing suppressive signals. In this study, we report the isolation of mRNA encoding the cotton rat PD-1 (crPD-1) and characterization of the PD-1 protein. crPD-1 bound to its cognate ligand on dendritic cells and effectively suppressed cytokine secretion. Moreover, using the newly acquired gene sequence, we observed a decreased level of crPD-1 levels in cotton rats with enhanced respiratory disease induced by inactivated RSV vaccine, unraveling a new facet of vaccine-induced disease.

Targeting CD40 enhances antibody- and CD8-mediated protection against respiratory syncytial virus infection

Respiratory Syncytial Virus (RSV) infects almost all children under the age of one and is the leading cause of hospitalization among infants. It also causes high rates of infection in the elderly and immunocompromised patient populations. Despite several decades of research with dozens of candidate vaccines being vigorously evaluated in pre-clinical and clinical studies, there is no licensed vaccine available to date. A clinical trial conducted in the early 1960s testing a formaldehyde-inactivated RSV (FIRSV) vaccine resulted in enhanced respiratory disease, following subsequent RSV infection, leading to hospitalization of 80% of the participants and 2 deaths. Since then, other forms of RSV vaccine have also been found to induce enhanced disease in preclinical animal studies. Here, we aimed to develop a vaccine that can effectively protect mice from RSV infection and help identify facets of FIRSV-induced enhanced disease. In this study, BALB/c mice were immunized with an adenoviral vector containing the RSV fusion protein (F) fused with CD40 ligand where the CD40 ligand serves two vital functions as a molecular adjuvant and an antigen-targeting molecule. In contrast to the FIRSV vaccine, the vectored vaccine effectively protected animals against RSV without inducing enhanced respiratory disease. This protection involved a robust induction of neutralizing antibodies and memory CD8 T cells, which were not observed in the FIRSV group. Finally, the vectored vaccine was able to elicit long-lasting protection against RSV, which was mediated by increased levels of effector memory CD8 T cell 3 months post-vaccination.

Unveiling Integrated Functional Pathways Leading to Enhanced Respiratory Disease Associated With Inactivated Respiratory Syncytial Viral Vaccine

Respiratory syncytial virus (RSV) infection is a severe threat to young children and the elderly. Despite decades of research, no vaccine has been approved. Notably, instead of affording protection, a formalin-inactivated RSV vaccine induced severe respiratory disease including deaths in vaccinated children in a 1960s clinical trial; however, recent studies indicate that other forms of experimental vaccines can also induce pulmonary pathology in pre-clinical studies. These findings suggest that multiple factors/pathways could be involved in the development of enhanced respiratory diseases. Clearly, a better understanding of the mechanisms underlying such adverse reactions is critically important for the development of safe and efficacious vaccines against RSV infection, given the exponential growth of RSV vaccine clinical trials in recent years. By employing an integrated systems biology approach in a pre-clinical cotton rat model, we unraveled a complex network of pulmonary canonical pathways leading to disease development in vaccinated animals upon subsequent RSV infections. Cytokines including IL-1, IL-6 GRO/IL-8, and IL-17 in conjunction with mobilized pulmonary inflammatory cells could play important roles in disease development, which involved a wide range of host responses including exacerbated pulmonary inflammation, oxidative stress, hyperreactivity, and homeostatic imbalance between coagulation and fibrinolysis. Moreover, the observed elevated levels of MyD88 implicate the involvement of this critical signal transduction module as the central node of the inflammatory pathways leading to exacerbated pulmonary pathology. Finally, the immunopathological consequences of inactivated vaccine immunization and subsequent RSV exposure were further substantiated by histological analyses of these key proteins along with inflammatory cytokines, while hypercoagulation was supported by increased pulmonary fibrinogen/fibrin accompanied by reduced levels of plasma D-dimers. Enhanced respiratory disease associated with inactivated RSV vaccine involves a complex network of host responses, resulting in significant pulmonary lesions and clinical manifestations such as tachypnea and airway obstruction. The mechanistic insight into the convergence of different signal pathways and identification of biomarkers could help facilitate the development of safe and effective RSV vaccine and formulation of new targeted interventions.

Targeting CD40 enhances antibody- and CD8-mediated protection against respiratory syncytial virus infection

Respiratory Syncytial Virus (RSV) infects almost all children under the age of one and is the leading cause of hospitalization among infants. Despite several decades of research with dozens of candidate vaccines being vigorously evaluated in pre-clinical and clinical studies, there is no licensed vaccine available to date. Here, the RSV fusion protein (F) was fused with CD40 ligand and delivered by an adenoviral vector into BALB/c mice where the CD40 ligand serves two vital functions as a molecular adjuvant and an antigen-targeting molecule. In contrast to a formaldehyde-inactivated vaccine, the vectored vaccine effectively protected animals against RSV without inducing enhanced respiratory disease. This protection involved a robust induction of neutralizing antibodies and memory CD8 T cells, which were not observed in the inactivated vaccine group. Finally, the vectored vaccine was able to elicit long-lasting protection against RSV, one of the most challenging issues in RSV vaccine development. Further studies indicate that the long lasting protection elicited by the CD40 ligand targeted vaccine was mediated by increased levels of effector memory CD8 T cell 3 months post-vaccination.

Apolipoprotein A-IV binds αIIbβ3 integrin and inhibits thrombosis

Platelet αIIbβ3 integrin and its ligands are essential for thrombosis and hemostasis, and play key roles in myocardial infarction and stroke. Here we show that apolipoprotein A-IV (apoA-IV) can be isolated from human blood plasma using platelet β3 integrin-coated beads. Binding of apoA-IV to platelets requires activation of αIIbβ3 integrin, and the direct apoA-IV-αIIbβ3 interaction can be detected using a single-molecule Biomembrane Force Probe. We identify that aspartic acids 5 and 13 at the N-terminus of apoA-IV are required for binding to αIIbβ3 integrin, which is additionally modulated by apoA-IV C-terminus via intra-molecular interactions. ApoA-IV inhibits platelet aggregation and postprandial platelet hyperactivity. Human apoA-IV plasma levels show a circadian rhythm that negatively correlates with platelet aggregation and cardiovascular events. Thus, we identify apoA-IV as a novel ligand of αIIbβ3 integrin and an endogenous inhibitor of thrombosis, establishing a link between lipoprotein metabolism and cardiovascular diseases.

Activation of integrin αIIbβ3 at the surface of platelets is required for their aggregation and for thrombus formation. Here Xu et al. identify apolipoprotein A-IV as a novel ligand for platelet αIIbβ3 integrin, and find it inhibits platelet aggregation and thrombosis.

Characterizing the surface-exposed proteome of Planococcus halocryophilus during cryophilic growth

Planococcus halocryophilus OR1 is a bacterial isolate capable of growth at temperatures ranging from -15 to +37 °C. During sub-zero (cryophilic) growth, nodular features appear on its cell surface; however, the biochemical compositions of these features as well as any cold-adaptive benefits they may offer are not understood. This study aimed to identify differences in the cell surface proteome (surfaceome) of P. halocryophilus cells grown under optimal (24 °C, no added salt), low- and mid-salt (5 and 12 % NaCl, respectively) at 24 °C, and low- and mid-salt sub-zero (5 % NaCl at -5 °C and 12 % NaCl at -10 °C) culture conditions, for the purpose of gaining insight into cold-adapted proteomic traits at the cell surface. Mid-log cells were harvested, treated briefly with trypsin and the resultant peptides were purified followed by identification by LC-MS/MS analysis. One hundred and forty-four proteins were subsequently identified in at least one culture condition. Statistically significant differences in amino acid usage, a known indicator of cold adaptation, were identified through in silico analysis. Two proteins with roles in peptidoglycan (PG) metabolism, an N-acetyl-L-alanine amidase and a multimodular transpeptidase-transglycosylase, were detected, though each was only detected under optimal conditions, indicating that high-salt and high-cold stress each affect PG metabolism. Two iron transport-binding proteins, associated with two different iron transport strategies, were identified, indicating that P. halocryophilus uses a different iron acquisition strategy at very low temperatures. Here we present the first set of data that describes bacterial adaptations at the cellular surface that occur as a cryophilic bacterium is transitioned from optimal to near-inhibitory sub-zero culture conditions.

Abstract 225: Apolipoprotein A-IV Is a ß3 Integrin Ligand and an Endogenous Inhibitor of Platelets: Novel Mechanisms of Prevention and Treatment for Atherothrombosis

Apolipoprotein A-IV (apoA-IV) is a lipid binding protein secreted by the intestine during dietary lipid absorption. Several clinical studies in different ethnic populations have demonstrated that apoA-IV levels inversely correlate with cardiovascular diseases. However, the roles of apoA-IV in platelet aggregation and atherothrombosis are completely unknown.

Here we isolated apoA-IV from plasma with beads coated with human platelet β3 integrin. Using a biomembrane force probe that detects single-molecule interactions, we clearly demonstrated that apoA-IV specifically binds to purified αIIbβ3 on beads and native αIIbβ3 on platelets or Chinese hamster ovary cells. ApoA-IV and αIIbβ3 interaction could be blocked by a monoclonal antibody against β 3 integrin, M1. Importantly, recombinant apoA-IV can competitively block fibrinogen-αIIbβ3 interaction, and specifically inhibited human and mouse platelet aggregation. Consistently, platelet aggregation was enhanced in mice lacking apoA-IV following stimulation with various agonists. In ex vivo perfusion chambers, apoA-IV inhibited human and mouse thrombus growth and dissolved pre-formed thrombi, while absence of apoA-IV enhanced ex vivo thrombosis under both low and high shear stresses. Furthermore, in vivo intravital microscopy models revealed that FeCl 3 - and laser-induced thrombosis were enhanced in mice lacking apoA-IV, while transfusion of human or mouse recombinant apoA-IV significantly attenuated this process. To further identify the potential binding sites of apoA-IV for platelet αIIbβ3 integrin, we deleted apoA-IV N-terminal 38 amino acids and/or the C-terminal 41 amino acids. We observed that deletion of the N-terminus abrogated platelet-inhibitory function. Interestingly, we found that mutation of either of two highly conserved aspartic acid (D) residues at positions 5 and 13 abolished or reduced the inhibitory function of apoA-IV, suggesting that D5 and/or D13 participate in a direct protein-protein interaction between apoA-IV and αIIbβ3 integrin.

Thus, apoA-IV is identified as a novel endogenous inhibitor of thrombosis and represents a novel link between lipoprotein metabolism and platelet function, both of which play critical roles in cardiovascular diseases.

SARS coronavirus: unusual lability of the nucleocapsid protein

The severe acute respiratory syndrome (SARS) is a contagious disease that killed hundreds and sickened thousands of people worldwide between November 2002 and July 2003. The nucleocapsid (N) protein of the coronavirus responsible for this disease plays a critical role in viral assembly and maturation and is of particular interest because of its potential as an antiviral target or vaccine candidate. Refolding of SARS N-protein during production and purification showed the presence of two additional protein bands by SDS-PAGE. Mass spectroscopy (MALDI, SELDI, and LC/MS) confirmed that the bands are proteolytic products of N-protein and the cleavage sites are four SR motifs in the serine-arginine-rich region-sites not suggestive of any known protease. Furthermore, results of subsequent testing for contaminating protease(s) were negative: cleavage appears to be due to inherent instability and/or autolysis. The importance of N-protein proteolysis to viral life cycle and thus to possible treatment directions are discussed.

A novel cross-linked RNase A dimer with enhanced enzymatic properties

A new cross-linked ribonuclease A (RNase A) dimer composed of monomeric units covalently linked by a single amide bond between the side-chains of Lys(66) and Glu(9) is described. The dimer was prepared in the absence of water by incubating a lyophilized preparation of RNase, sealed under vacuum, in an oven at 85 degrees C. It was determined that the in vacuo procedure does not induce any significant conformational changes to the overall structure of RNase A, yet the amide cross-link has an increased acid lability, indicating that it is exposed and conformationally strained. Examination of X-ray crystallographic structures indicates that Lys(66) and Glu(9) are not close enough for the in vacuo dimer to adopt any of the known domain-swapped conformations. Therefore, the in vacuo RNase A dimer appears to be a novel dimeric structure. The in vacuo RNase A dimer also exhibits a twofold increase in activity over monomeric RNase A on a per monomer basis. This doubling of enzymatic activity was shown using dsRNA and ssRNA as substrates. In addition to this enhanced ability to degrade RNA, the dimer is not inhibited by the cellular ribonuclease inhibitor protein (cRI).

Detection of residual pertussis toxin in vaccines using a modified ribosylation assay

Pertussis toxin (PTx) in its detoxified form is an important component of both whole cell and acellular pertussis vaccines (ACVs). For safety reasons, it is imperative to ensure that the quantity of residual PTx in vaccines does not exceed permissible levels. The majority of the toxic effects of PTx have been attributed to the consequences of PTx-catalyzed ribosylation of the alpha-subunits of signal-transducing guanine-nucleotide-binding proteins. In this report PTx ribosylation activity was determined by an improved enzymatic-high performance liquid chromatography coupled assay using a fluorescein labeled Galpha(i3)C20 peptide. The effect of aluminum salts and other vaccine components on the assay system were also studied. The enzymatic assay system was shown to be a convenient, sensitive method and correlate well with the toxicity observed in vivo by the histamine sensitization assay. This method forms the basis of a new assay which could replace the unsatisfactory animal test currently used in pertussis vaccines control.

Covalent cross-linking of proteins without chemical reagents

A facile method for the formation of zero-length covalent cross-links between protein molecules in the lyophilized state without the use of chemical reagents has been developed. The cross-linking process is performed by simply sealing lyophilized protein under vacuum in a glass vessel and heating at 85 degrees C for 24 h. Under these conditions, approximately one-third of the total protein present becomes cross-linked, and dimer is the major product. Chemical and mass spectroscopic evidence obtained shows that zero-length cross-links are formed as a result of the condensation of interacting ammonium and carboxylate groups to form amide bonds between adjacent molecules. For the protein examined in the most detail, RNase A, the cross-linked dimer has only one amide cross-link and retains the enzymatic activity of the monomer. The in vacuo cross-linking procedure appears to be general in its applicability because five different proteins tested gave substantial cross-linking, and co-lyophilization of lysozyme and RNase A also gave a heterogeneous covalently cross-linked dimer.

Identification of a new plasmid-encoded sec-dependent bacteriocin produced by Listeria innocua 743

Listeria innocua 743 produces an inhibitory activity demonstrating broad-spectrum inhibition of Listeria monocytogenes isolates. Gel-electrophoretic analysis of culture supernatants indicated that two inhibitors with different molecular weights were produced by this strain. Insertion of Tn917 into a 2.9 Kb plasmid (pHC743) generated mutants with either an impaired ability or a loss in ability to produce one of the inhibitors. Sequence analysis of the transposon insertion regions revealed the presence of two continuous open reading frames, the first encoding a new pediocin-like bacteriocin (lisA) and the second encoding a protein homologous with genes involved in immunity toward other bacteriocins (lisB). Translation of the bacteriocin gene (lisA) initiates from a noncanonical start codon and encodes a 71-amino-acid prebacteriocin which lacked the double glycine leader peptidase processing site common in other type II bacteriocins. Alignment of the sequence with the processed N termini of related bacteriocins suggests that the mature bacteriocin consists of 43 amino acids, with a predicted molecular mass of 4,484 Da. Mutants containing insertions into lisA were sensitive to the inhibitor, indicating that lisAB forms a single operon and that lisB represents the immunity protein. Cloning of an amplicon containing the lisAB operon into Escherichia coli resulted in expression and export of the bacteriocin. This finding confirms that the phenotype is dependent on the structural and immunity gene only and that export of this bacteriocin is sec dependent. This is the first confirmation of bacteriocin production in a Listeria spp., and it is of interest that this bacteriocin is closely related to the pediocin family of bacteriocins produced by lactic acid bacteria.

A quantitative analysis for the ADP-ribosylation activity of pertussis toxin: an enzymatic-HPLC coupled assay applicable to formulated whole cell and acellular pertussis vaccine products

The majority of the biological effects of pertussis toxin (PT) are the result of a toxin-catalyzed transfer of an adenosine diphosphate-ribose (ADP-ribose) moiety from NAD(+)to the alpha-subunits of a subset of signal-transducing guanine-nucleotide-binding proteins (G-proteins). This generally leads to an uncoupling of the modified G-protein from the corresponding receptor and the loss of effector regulation. This assay is based on the PT S1 subunit enzymatic transfer of ADP-ribose from NAD to the cysteine moiety of a fluorescent tagged synthetic peptide homologous to the 20 amino acid residue carboxyl-terminal sequence of the alpha-subunit of the G(i3)protein. The tagged peptide and the ADP-ribosylated product were characterized by HPLC/MS and MS/MS for structure confirmation. Quantitation of this characterized ADP-ribosylated fluorescently tagged peptide was by HPLC fluorescence using Standard Addition methodology. The assay was linear over a five hr incubation period at 20 degrees C at PT concentrations between 0.0625 and 4.0 microg/ml and the sensitivity of the assay could be increased several fold by increasing the incubation time to 24 h. Purified S1 subunit of PT exhibited 68.1+/-10.1% of the activity of the intact toxin on a molar basis, whereas the pertussis toxin B oligomer, the genetically engineered toxoid, (PT-9K/129G), and several of the other components of the Bordetella pertussis organism possessed little (<0.6%) or no detectable ribosylation activity. Commonly used pertussis vaccine reference materials, US PV Lot #11, BRP PV 66/303, and BRP PV 88/522, were assayed by this method against Bordetella pertussis Toxin Standard 90/518 and demonstrated to contain, respectively, 0.323+/-0.007, 0.682+/-0.045, and 0.757+/-0.006 microg PT/ml (Mean+/-SEM) or in terms of microg/vial: 3.63, 4.09 and 4.54, respectively. A survey of several multivalent pertussis vaccine products formulated with both whole cell as well as acellular components indicated that products possessed a wide range of ribosylation activities. The pertussis toxin S1 subunit catalyzed ADP- ribosylation of the FAC-Galpha(i3)C20 peptide substrate and its subsequent quantitation by HPLC was demonstrated to be a sensitive and quantitative method for measuring intrinsic pertussis toxin activity. This methodology not only has the potential to be an alternative physicochemical method to replace existing bioassay methodology, but has the added advantage of being a universal method applicable to the assay of pertussis toxin in both whole cell and acellular vaccines as well as bulk and final formulated vaccine products. Acceptance of this method by regulatory agencies and industry as a credible alternative to existing methods would, however, require validation in an international collaborative study against the widely accepted bioassay methods.

Terfenadine metabolism in human liver. In vitro inhibition by macrolide antibiotics and azole antifungals

To determine whether the clinical adverse interactions of terfenadine with azole antifungals and macrolide antibiotics may be related to inhibition of terfenadine biotransformation, an in vitro system was developed to follow the metabolism of terfenadine by rat liver S9 or human liver microsomes. When test compounds were coincubated with terfenadine, the metabolites formed and unchanged terfenadine was quantitatively analyzed by HPLC. Five metabolites of terfenadine were formed by rat liver S9: predominantly alcohol metabolite (III), with four minor metabolites--azacyclonol (I), acid metabolite (II), an unidentified metabolite (IV), and a new ketone metabolite (V). By human liver microsomes, two major metabolites were formed: azacyclonol (I) and alcohol metabolite (III). Ketoconazole, fluconazole, itraconazole, erythromycin, clarithromycin, and troleandomycin potently inhibited terfenadine metabolism by human liver (IC50 = 4-10 microM), but inhibition by rat liver was weaker (IC50 = 87-218 microM) and 18% maximally for troleandomycin. Other CYP3A substrates (cyclosporin A, naringenin, and midazolam) also demonstrated potent inhibition of terfenadine biotransformation in human liver microsomes (IC50 = 17-24 microM). Substrates of other P450 families [sparteine (CYP2D6), caffeine (CYP1A), and diclofenac (CYP2C)] only very weakly inhibited terfenadine metabolism. Dixon plot analyses for human liver revealed competitive/reversible inhibition by the azole antifungals and macrolide antibiotics of azacyclonol and alcohol metabolite formations.(ABSTRACT TRUNCATED AT 250 WORDS)