Molecular cloning and characterization of the human double-stranded RNA-activated protein kinase induced by interferon

The double-stranded (ds) RNA-activated protein kinase from human cells is a 68 kd protein (p68 kinase) induced by interferon. On activation by dsRNA in the presence of ATP, the kinase becomes autophosphorylated and can catalyze the phosphorylation of the alpha subunit of eIF2, which leads to an inhibition of the initiation of protein synthesis. Here we report the molecular cloning and characterization of several related cDNAs from which can be deduced the full-length p68 kinase sequence. All of the cDNAs identify a 2.5 kb RNA that is strongly induced by interferon. The deduced amino acid sequence of the p68 kinase predicts a protein of 550 amino acids containing all of the conserved domains specific for members of the protein kinase family, including the catalytic domain characteristic of serine/threonine kinases. In vitro translation of a reconstructed full-length p68 kinase cDNA yields a protein of 68 kd that binds dsRNA, is recognized by a monoclonal antibody raised against the native p68 kinase, and is autophosphorylated.

Tipranavir (PNU-140690): a potent, orally bioavailable nonpeptidic HIV protease inhibitor of the 5,6-dihydro-4-hydroxy-2-pyrone sulfonamide class

A broad screening program previously identified phenprocoumon (1) as a small molecule template for inhibition of HIV protease. Subsequent modification of this lead through iterative cycles of structure-based design led to the activity enhancements of pyrone and dihydropyrone ring systems (II and V) and amide-based substitution (III). Incorporation of sulfonamide substitution within the dihydropyrone template provided a series of highly potent HIV protease inhibitors, with structure-activity relationships described in this paper. Crystallographic studies provided further information on important binding interactions responsible for high enzymatic binding. These studies culminated in compound VI, which inhibits HIV protease with a Ki value of 8 pM and shows an IC90 value of 100 nM in antiviral cell culture. Clinical trials of this compound (PNU-140690, Tipranavir) for treatment of HIV infection are currently underway.

Constitutive expression of human double-stranded RNA-activated p68 kinase in murine cells mediates phosphorylation of eukaryotic initiation factor 2 and partial resistance to encephalomyocarditis virus growth

The cDNA encoding interferon-induced human double-stranded RNA-activated p68 kinase was expressed in murine NIH 3T3 cells by using the pcDNA1/neo vector. Several stable clones were selected which expressed either the wild-type kinase or an inactive mutant possessing a single amino acid substitution in the invariant lysine 296 in the catalytic domain II. The transfected wild-type kinase showed properties similar to those of the natural kinase, such as subcellular ribosomal localization and dependence on double-stranded RNA for autophosphorylation. Upon infection with encephalomyocarditis virus (EMCV), wild-type- but not mutant-expressing clones were found to partially resist virus growth. Such natural antiviral activity was virus specific, since no inhibition was observed in the case of vesicular stomatitis virus infection. In accord with EMCV inhibition, the wild-type p68 kinase was found to be highly phosphorylated during infection. Furthermore, its natural substrate, the small subunit of protein synthesis initiation factor eIF2, was phosphorylated. These results demonstrate that p68 kinase is activated during EMCV infection, leading to reduced virus production.

Identification of double-stranded RNA-binding domains in the interferon-induced double-stranded RNA-activated p68 kinase

The double-stranded RNA (dsRNA)-binding domain of the human p68 kinase has been localized to the N-terminal half of the enzyme by using progressive deletion analysis and in vitro binding assays. To further define the domains responsible for binding to dsRNA, we cloned the mouse dsRNA-activated p65 kinase and used sequence alignment to identify conserved domains in the N-terminal region. Deletions in either of two 12-amino-acid-long and arginine- or lysine-rich regions abrogated binding to dsRNA. Moreover, in an in vivo growth inhibition assay in the yeast Saccharomyces cerevisiae, these mutants failed to exhibit a slow-growth phenotype.

Human STX polysialyltransferase forms the embryonic form of the neural cell adhesion molecule. Tissue-specific expression, neurite outgrowth, and chromosomal localization in comparison with another polysialyltransferase, PST

PST and STX are polysialyltransferases that form polysialic acid in the neural cell adhesion molecule (N-CAM), although it is not known why these two polysialyltransferases exist. In the present study, we have first isolated cDNA encoding human STX, which includes 5'-untranslated sequence. Northern blot analysis, using this cDNA and PST cDNA previously isolated by us, demonstrated that PST and STX are expressed in different fetal and adult tissues. STX is primarily expressed in embryonic tissues, but only modestly in adult heart, brain, and thymus. PST, on the other hand, is continuously expressed in adult heart, brain, thymus, spleen, small and large intestines, and peripheral blood leukocytes. In various parts of adult brain, the relative amount of PST and STX appears to be substantially different depending on the regions. The analysis by in situ hybridization of mouse adult brain, however, suggests that polysialic acid in the hippocampal formation is synthesized by both STX and PST. HeLa cells doubly transfected with the isolated STX cDNA and N-CAM cDNA supported neurite outgrowth much better than HeLa cells expressing N-CAM alone. However, polysialic acid synthesized by PST appears to be a better substratum than that synthesized by STX. Moreover, the genes for PST and STX were found to reside at chromosome 5, band p21 and chromosome 15, band q26, respectively. These results, taken together, strongly suggest that PST and STX are expressed distinctly in tissue-specific and cell-specific manners and that they apparently have distinct roles in development and organogenesis.

Antiviral activity of the dihydropyrone PNU-140690, a new nonpeptidic human immunodeficiency virus protease inhibitor

PNU-140690 is a member of a new class of nonpeptidic human immunodeficiency virus (HIV) protease inhibitors (sulfonamide-containing 5,6-dihydro-4-hydroxy-2-pyrones) discovered by structure-based design. PNU-140690 has excellent potency against a variety of HIV type 1 (HIV-1) laboratory strains and clinical isolates, including those resistant to the reverse transcriptase inhibitors zidovudine or delavirdine. When combined with either zidovudine or delavirdine, PNU-140690 contributes to synergistic antiviral activity. PNU-140690 is also highly active against HIV-1 variants resistant to peptidomimetic protease inhibitors, underscoring the structural distinctions between PNU-140690 and substrate analog protease inhibitors. PNU-140690 retains good antiviral activity in vitro in the presence of human plasma proteins, and preclinical pharmacokinetic studies revealed good oral bioavailability. Accordingly, PNU-140690 is a candidate for clinical evaluation.

Structure-based design of novel HIV protease inhibitors: carboxamide-containing 4-hydroxycoumarins and 4-hydroxy-2-pyrones as potent nonpeptidic inhibitors

The low oral bioavailability and rapid biliary excretion of peptide-derived HIV protease inhibitors have limited their utility as potential therapeutic agents. Our broad screening program to discover nonpeptidic HIV protease inhibitors had previously identified compound II (phenprocoumon, K(i) = 1 muM) as a lead template. Crystal structures of HIV protease complexes containing the peptide-derived inhibitor I (1-(naphthoxyacetyl)-L-histidyl-5(S)-amino-6-cyclohexyl-3 (R),4(R)-dihydroxy-2(R)-isopropylhexanoyl-L-isoleucine N-(2-pyridylmethyl)amide) and nonpeptidic inhibitors, such as phenprocoumon (compound II), provided a rational basis for the structure-based design of more active analogues. This investigation reports on the important finding of a carboxamide functionally appropriately added to the 4-hydroxycoumarin and the 4-hydroxy-2-pyrone templates which resulted in a new promising series of nonpeptidic HIV protease inhibitors with improved enzyme-binding affinity. The most active diastereomer of the carboxamide-containing compound XXIV inhibited HIV-1 protease with a K(i) value of 0.0014 muM. This research provides a new design direction for the discovery of more potent HIV protease inhibitors as potential therapeutic agents for the treatment of HIV infection.

Structure-based design of novel HIV protease inhibitors: sulfonamide-containing 4-hydroxycoumarins and 4-hydroxy-2-pyrones as potent non-peptidic inhibitors

The low oral bioavailability and rapid biliary excretion of peptide-derived HIV protease inhibitors have limited their utility as potential therapeutic agents. Our broad screening program to discover non-peptidic HIV protease inhibitors previously identified compound I (phenprocoumon, Ki = 1 microM) as a lead template. Structure-based design of potent non-peptidic inhibitors, utilizing crystal structures of HIV protease/inhibitor complexes, provided a rational basis for the previously reported carboxamide-containing 4-hydroxycoumarins and 4-hydroxy-2-pyrones. The amino acid containing compound V (Ki = 4 nM) provided an example of a promising new series of HIV protease inhibitors with significantly improved enzymatic binding affinity. In this report, further structure-activity relationship studies, in which the carboxamide is replaced by a sulfonamide functionality, led to the identification of another series of nonamino acid containing promising inhibitors with significantly enhanced enzyme binding affinity and in vitro antiviral activity. The most active diastereomer of the sulfonamide-containing pyrone XVIII (Ki = 0.5 nM) shows improved antiviral activity (IC50 = 0.6 nM) and represents an example of a new design direction for the discovery of more potent non-peptidic HIV protease inhibitors as potential therapeutic agents for the treatment of HIV infection.

Bone marrow transplantation for Maroteaux-Lamy syndrome (MPS VI): long-term follow-up

We describe the results of bone marrow transplantation (BMT) in four patients with mucopolysaccharidosis type VI (MPS VI, McKusick 253200)--Maroteaux-Lamy disease. The indications for transplantation were cardiomyopathy in three patients and severe obstructive sleep apnoea in one. The follow-up period ranges between 1 and 9 years, and three of the patients are at mainstream schools. In all of the patients the facial features have become less coarse and the cardiac manifestations have improved or remained stable. However, skeletal changes have persisted or even progressed, although posture and joint mobility have improved and all the patients have remained ambulatory and active. BMT appears to prolong survival and improve the quality of life in MPS VI patients, but careful selection of patients is essential.

Neonatal diabetes, with hypoplastic pancreas, intestinal atresia and gall bladder hypoplasia: search for the aetiology of a new autosomal recessive syndrome

AIMS/HYPOTHESIS

Neonatal diabetes is a rare disease with several identified molecular aetiologies. Despite associations with other malformations, neonatal diabetes with intestinal and biliary anomalies has not been described. The current study aims to describe a new syndrome, and to examine a possible link with one of three genes known to cause neonatal diabetes.

METHODS

Five clinical cases are described. Immunohistochemical staining for pancreatic islet hormones was performed on three of the infants. DNA from one infant was analysed for abnormalities of the PLAGL-1 (ZAC), glucokinase and PDX-1 (IPF-1) genes.

RESULTS

Five infants (two sibling pairs from two families, and an isolated case) presented with neonatal diabetes, hypoplastic or annular pancreas, jejunal atresia, duodenal atresia and gall bladder aplasia or hypoaplasia. One sibling pair was born to consanguineous parents. One patient with a milder form is surviving free of insulin. Four children died in the first year of life despite aggressive medical management. Pancreatic immunohistochemistry revealed few scattered chromogranin-A-positive cell clusters but complete absence of insulin, glucagon and somatostatin. Exocrine histology was variable. In one case from the consanguineous family, molecular analysis showed no duplication or uniparental isodisomy of PLAGL-1 at 6q24, no contiguous gene deletion involving the glucokinase gene, and no mutation in the coding sequences or splice sites of PDX-1.

CONCLUSIONS/INTERPRETATION

This combination of multiple congenital abnormalities has not been previously described and probably represents a new autosomal recessive syndrome involving a genetic abnormality that interferes with normal islet development and whose aetiology is as yet unknown.

Structure-based design of HIV protease inhibitors: 5,6-dihydro-4-hydroxy-2-pyrones as effective, nonpeptidic inhibitors

From a broad screening program, the 4-hydroxycoumarin phenprocoumon (I) was previously identified as a lead template with HIV protease inhibitory activity. The crystal structure of phenprocoumon/HIV protease complex initiated a structure-based design effort that initially identified the 4-hydroxy-2-pyrone U-96988 (II) as a first-generation clinical candidate for the potential treatment of HIV infection. Based upon the crystal structure of the 4-hydroxy-2-pyrone III/HIV protease complex, a series of analogues incorporating a 5,6-dihydro-4-hydroxy-2-pyrone template were studied. It was recognized that in addition to having the required pharmacophore (the 4-hydroxy group with hydrogen-bonding interaction with the two catalytic aspartic acid residues and the lactone moiety replacing the ubiquitous water molecule in the active site), these 5,6-dihydro-4-hydroxy-2-pyrones incorporated side chains at the C-6 position that appropriately extended into the S1' and S2' subsites of the enzyme active site. The crystal structures of a number of representative 5,6-dihydro-4-hydroxy-2-pyrones complexed with the HIV protease were also determined to provide better understanding of the interaction between the enzyme and these inhibitors to aid the structure-based drug design effort. The crystal structures of the ligands in the enzyme active site did not always agree with the conformations expected from experience with previous pyrone inhibitors. This is likely due to the increased flexibility of the dihydropyrone ring. From this study, compound XIX exhibited reasonably high enzyme inhibitory activity (Ki = 15 nM) and showed antiviral activity (IC50 = 5 microM) in the cell-culture assay. This result provided a research direction which led to the discovery of active 5,6-dihydro-4-hydroxy-2-pyrones as potential agents for the treatment of HIV infection.

Functional expression and RNA binding analysis of the interferon-induced, double-stranded RNA-activated, 68,000-Mr protein kinase in a cell-free system

Eukaryotic viruses have devised numerous strategies to downregulate activity of the interferon-induced, double-stranded (dsRNA)-activated protein kinase (referred to as p68 on the basis of its Mr of 68,000 in human cells). Viruses must exert this control to avoid extensive phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF-2) by p68 and the resultant negative effects on protein synthesis initiation. To begin to define the molecular mechanisms underlying this regulation, we optimized expression of p68 in an in vitro transcription-translation system utilizing the full-length cDNA clone. The in vitro-expressed kinase was autophosphorylated in response to dsRNAs and heparin in a manner similar to that for the native p68 provided that the kinase inhibitor, 2-aminopurine, was present during the in vitro translation reaction. Further, the activated kinase efficiently phosphorylated its natural substrate, the alpha subunit of eIF-2. Binding experiments revealed that the expressed kinase complexed with the dsRNA activator, reovirus dsRNA, as well as the adenovirus-encoded inhibitor, VAI RNA. Interestingly, both the reovirus RNAs and VAI RNA also complexed with protein kinase molecules that lacked the carboxyl terminus and all catalytic domains. Deletion analysis confirmed that the p68 amino terminus contained critical determinants for reovirus dsRNA and VAI RNA binding. Further, reovirus dsRNA efficiently bound to, but failed to activate, p68 kinase molecules containing a single amino acid substitution in the invariant lysine 295 present in catalytic domain II. Taken together, these data demonstrate that this expression system permits a detailed mutagenic analysis of the regions of p68 required for interaction with virus-encoded activators and repressors.

Comparative studies on the biokinetics of Cd, Cr, and Zn in the green mussel Perna viridis and the Manila clam Ruditapes philippinarum

A kinetic approach was employed to determine the rates of metal uptake (Cd, Cr and Zn) from the dissolved phase and the rate constants of metal depuration in the mussel Perna viridis and the clam Ruditapes philippinarum. The effects of ambient metal concentration, salinity, and body size on the metal influx rate were examined. A linear positive relationship was observed between the metal influx rate and the metal concentration in ambient seawater. There was some evidence that Zn uptake was regulated by the bivalves in response to an increase in ambient Zn concentration. The uptake rate constant was highest for Zn and lowest for Cr in both bivalves, and was higher in mussels than in clams. The metal influx rate decreased by 1.6-1.8 times for the three metals when the salinity was increased from 15 ppt to 30 ppt. However, the effect of salinity on Zn influx in mussels was not statistically significant. A negative relationship of Cd and Zn influx rates with tissue dry weight was also found in both bivalves. Cr uptake in mussels was not significantly correlated with body size, but its uptake in clams was significantly correlated with body size. Metal concentration in ambient seawater appeared to be the most determining factor on metal uptake from the dissolved phase in both bivalves. The efflux rate constants of the three metals were within the range of 0.01-0.03 d-1, and were comparable between the mussels and the clams. Using a simple bioenergetic-based kinetic model, it was shown that both dissolved uptake and food ingestion can contribute to metal accumulation in the bivalves. However, Zn accumulation in the clam R. philippinarum was dominated by uptake from food ingestion. Metal partitioning in ingested food was found to be critical in affecting the relative importance of metal uptake from the dissolved phase and food source, primarily because of the large variability of this parameter in natural environments.

The pathogenesis of nephritis in chickens induced by infectious bronchitis virus

Nephritis in chickens caused by infectious bronchitis virus (IBV) was studied by virological, histological and electron microscopical methods. The T strain of the virus caused only mild respiratory signs in both Rhode Island Red (RIR) and White Leghorn (WL) breeds; the 50 per cent mortality induced was due to acute nephritis. All the infected birds developed high titres of antibody to IBV for up to 30 weeks. In spite of the persistence of antibody, about 35 per cent of the RIR developed chronic progressive nephritis. The histology showed varying degrees of pathological changes in the tubules, with relatively unaffected glomeruli. Foci of mononuclear cell infiltration were prominent in the cortex and medulla, particularly in chronic nephritis. Cytoplasmic IBV immunofluorescence was found in all segments of the tubules, but not in the glomeruli. There was no evidence of virus replication in the caecal tonsil and bursa of Fabricius. Evidence of extensive coronavirus replication was found in the cells of the tubules. A large number of viral inclusion bodies as seen containing dark smooth particles 120 nm in diameter within a single membrane. Virus was readily recovered from the kidneys as well as faeces of birds with acute and chronic nephritis. It is concluded that direct virus-induced cell lysis is the primary cause of IBV nephritis. In addition, about 50 per cent of the chronically infected birds also developed brush-border auto-antibody.

Structure-based design of nonpeptidic HIV protease inhibitors: the sulfonamide-substituted cyclooctylpyramones

Recently, cyclooctylpyranone derivatives with m-carboxamide substituents (e.g. 2c) were identified as potent, nonpeptidic HIV protease inhibitors, but these compounds lacked significant antiviral activity in cell culture. Substitution of a sulfonamide group at the meta position, however, produces compounds with excellent HIV protease binding affinity and antiviral activity. Guided by an iterative structure-based drug design process, we have prepared and evaluated a number of these derivatives, which are readily available via a seven-step synthesis. A few of the most potent compounds were further evaluated for such characteristics as pharmacokinetics and toxicity in rats and dogs. From this work, the p-cyanophenyl sulfonamide derivative 35k emerged as a promising inhibitor, was selected for further development, and entered phase I clinical trials.

Identification of Arcobacter cryaerophilus isolated from a traffic accident victim with bacteremia by 16S ribosomal RNA gene sequencing

Traditional ways of identifying slow growing bacteria is slow and often difficult. In this study, a small, Gram-negative, facultative anaerobic, slow growing bacillus was isolated from the blood culture of a 7-year old traffic accident victim. The bacterium was non-hemolytic, catalase and oxidase positive. An attempt to use the Vitek system (GNI+) and the API system (20NE) to identify the strain was unsuccessful as the growth controls showed negative results. 16S ribosomal RNA gene sequencing showed that there was 1 base difference between the isolate and Arcobacter cryaerophilus (GenBank Accession no. U25805), 1 base difference between the isolate and A. cryaerophilus (GenBank Accession no. U34387), 10 base differences between the isolate and A. cryaerophilus (GenBank Accession no. L14624), 34 base differences between the isolate and A. butzleri (GenBank Accession no. U34386), 34 base differences between the isolate and A. butzleri (GenBank Accession no. U34387), and 38 base differences between the isolate and A. butzleri (GenBank Accession no. L14626), indicating that the isolate most closely resembled a strain of A. cryaerophilus. Identification of the isolate in our case by conventional methods was difficult, as the absence of a curved morphology has made it confused with other Gram-negative non-fermentative bacteria, and the slow growth rate has made it unidentifiable by both the Vitek and API systems. Although the exact source of infection and route of transmission in our case remains elusive, we speculate that the bacteria were transmitted through the respiratory tract while the boy was suffocated in the mud. The present report represents an example of showing the usefulness of 16S rRNA gene sequencing for identification of slow growing bacteria.

Gastric bypass in Type 2 diabetes with BMI < 30: weight and weight loss have a major influence on outcomes

AIM

To assess factors influencing glycaemic control following gastric bypass surgery in patients with Type 2 diabetes and BMI< 30 kg/m(2) .

METHODS

Prospective longitudinal study of 103 patients with inadequate glycaemic control who underwent gastric bypass surgery at Soonchunhyang University, Seoul, Korea (n = 66) and Min-Sheng General Hospital, Taipei, Taiwan (n = 37). Procedures were performed August 2009 to January 2011. Key outcome measures were excellent glycaemic control of Type 2 diabetes defined as HbA1c < 42 mmol/mol (≤6%); inadequate response defined as HbA1c > 53 mmol/mol (> 7%). Analysis was conducted using binary logistic regression, and cut-points obtained from receiver operator characteristics.

RESULTS

Excellent glycaemic control was achieved in 31 (30%) at 1 year. Diabetes duration of < 7 years and BMI > 27 kg/m(2) provided independent predictors and useful cut-points. Likelihood of excellent glycaemic control for an individual could be estimated using loge (Odds) = -6.7 + (0.26 × BMI) + (-1.2 × diabetes duration). Baseline BMI of < 27 kg/m(2) and baseline C-peptide of < 2.0ng/ml, best predicted a poor glycaemic response. In those with favourable baseline characteristics percentage weight loss (%WL) had a dominant influence on glycaemic outcomes. Baseline C-peptide (> 2.4 ng/ml) and subsequent percentage weight loss (> 16%) were associated with excellent glycaemic control. Higher BMI was associated with greater percentage weight loss.

CONCLUSION

In patients with Type 2 diabetes and BMI < 30 kg/m(2) , glycaemic response to gastric bypass is predicted by higher baseline BMI, shorter disease duration and higher fasting C-peptide. Post-surgery weight loss has a dominant effect. Baseline BMI and weight loss have a major influence on outcomes.

Bisheteroarylpiperazine reverse transcriptase inhibitor in combination with 3'-azido-3'-deoxythymidine or 2',3'-dideoxycytidine synergistically inhibits human immunodeficiency virus type 1 replication in vitro

Bisheteroarylpiperazine compounds are nonnucleoside reverse transcriptase inhibitors of human immunodeficiency virus type 1 (HIV-1). To provide a rationale for combination therapy with a second-generation bisheteroarylpiperazine, we investigated the effect of U-90152 in combination with 3'-azido-3'-deoxythymidine (AZT) or 2',3'-dideoxycytidine (ddC). HIV-1-infected cells were cultured in the presence of test compounds, and drug effects on p24 core antigen production were measured by an enzyme-linked immunosorbent assay. In a CD4+ T-cell line (H9) infected with HIV-1IIIB, the 50% effective concentrations for U-90152, AZT, and ddC were 6.0, 80.4, and 31.8 nM, respectively. In human peripheral blood mononuclear cells infected with the molecularly cloned clinical isolate HIV-1JRCSF, the 50% effective concentrations for U-90152, AZT, and ddC were 5.3, 5.9, and 25.0 nM, respectively. Over a range of drug concentrations (U-90152 and AZT at 0.3, 1, 3, 10, and 30 nM; ddC at 3, 10, 30, and 100 nM), U-90152 in combination with AZT or ddC synergistically inhibited the replication of a laboratory-adapted strain and a clinical isolate of HIV-1.

The functional similarity and structural diversity of human and cartilaginous fish hemoglobins

Although many descriptions of adaptive molecular evolution of vertebrate hemoglobins (Hb) can be found in physiological text books, they are based mainly on changes of the primary structure and place more emphasis on conservation than alterations at the functional site. Sequence analysis alone, however, does not reveal much about the evolution of new functions in proteins. It was found recently that there are many functionally important structural differences between human and a ray (Dasyatis akajei) Hb even where sequence is conserved between the two. We have solved the structures of the deoxy and CO forms of a second cartilaginous fish (a shark, Mustelus griseus) Hb, and compared it with structures of human Hb, two bony fish Hbs and the ray Hb in order to understand more about how vertebrate Hbs have functionally evolved by the selection of random amino acid substitutions. The sequence identity of cartilaginous fish Hb and human Hb is a little less than 40 %, with many functionally important amino acid replacements. Wider substitutions than usually considered as neutral have been accepted in the course of molecular evolution of Hb. As with the ray Hb, the shark Hb shows functionally important structural differences from human Hb that involve amino acid substitutions and shifts of preserved amino acid residues induced by substitutions in other parts of the molecule. Most importantly, beta E11Val in deoxy human Hb, which overlaps the ligand binding site and is considered to play a key role in controlling the oxygen affinity, moves away about 1 A in both the shark and ray Hbs. Thus adaptive molecular evolution is feasible as a result of both functionally significant mutations and deviations of preserved amino acid residues induced by other amino acid substitutions.

Prophylactic administration of interleukin-2 protects mice from lethal challenge with gram-negative bacteria

Prophylactic administration of recombinant human interleukin-2 (IL-2) in mice enhanced survival and produced complete recovery from an otherwise lethal acute bacterial infection. IL-2 was administered as a single intraperitoneal or intravenous bolus dose to CDI mice 18 h before challenge with a lethal dose of a clinical isolate of Escherichia coli type O2 (minimal 100% lethal dose, 6 X 10(7) CFU per mouse). At IL-2 dosages of 7 X 10(6) U/kg, 90% of treated CDI mice survived as compared to 0% for the excipient buffer control animals (P less than 0.001). This protective effect was also demonstrable in immune-deficient beige mice. The IL-2 effect was dose dependent; protection was consistently observed in mice pretreated with IL-2 at doses ranging from 1.8 X 10(6) to 7 X 10(6) U/kg. However, at 3.5 X 10(5) U/kg the protective effect was more variable. The route of administration of IL-2 was shown to play an important role; when IL-2 and challenge bacteria were given by the same route (either intravenously or intraperitoneally), protection was readily observable, but when IL-2 and challenge bacteria were given by different routes, little or no protective effect was observed. The protective effect was fully inducible as early as 1 h after IL-2 administration and was effective against various strains of gram-negative bacteria, indicating that the probable mode of action represents control of the establishment of infection by increased activity of the nonspecific host defense mechanisms. The IL-2 effect was abrogated by the administration of carrageenan, suggesting a possible role of macrophages. These data demonstrate that IL-2 may be a potentially useful adjunct for the prophylaxis of bacterial infections in both clinical and veterinary medicine.

Cycloalkylpyranones and cycloalkyldihydropyrones as HIV protease inhibitors: exploring the impact of ring size on structure-activity relationships

Previously, 3-substituted cycloalkylpyranones, such as 2d, have proven to be effective inhibitors of HIV protease. In an initial series of 3-(1-phenylpropyl) derivatives with various cycloalkyl ring sizes, the cyclooctyl analog was the most potent. We became interested in exploring the influence of other structural changes, such as substitution on the phenyl ring and saturation of the 5,6-double bond, on the cycloalkyl ring size structure-activity relationship (SAR). Saturation of the 5,6-double bond in the pyrone ring significantly impacts the SAR, altering the optimal ring size from eight to six. Substitution of a sulfonamide at the meta position of the phenyl ring dramatically increases the potency of these inhibitors, but it does not change the optimal ring size in either the cycloalkylpyranone or the cycloalkyldihydropyrone series. This work has led to the identification of compounds with superb binding affinity for the HIV protease (Ki values in the 10-50 pM range). In addition, the cycloalkyldihydropyrones showed excellent antiviral activity in cell culture, with ED50 values as low as 1 microM.

Effect of oestrogen and 1,25-dihydroxycholecalciferol on 25-hydroxycholecalciferol metabolism in primary chick kidney-cell cultures

Primary cultures of chick kidney cells convert 25-hydroxycholecalciferol into more-polar metabolites. Cells from vitamin D-deficient chicks have high 25-hydroxycholecalciferol 1 alpha-hydroxylase (1 alpha-hydroxylase) activity, but no 25-hydroxycholecalciferol 24-hydroxylase (24-hydroxylase) activity. Physiological concentrations of 1,25-dihydroxycholeclaciferol suppress 1 alpha-hydroxylase and induce 24-hydroxylase activity. The inhibition of 1 alpha-hydroxylase preceded the induction of 24-hydroxylase. In contrast, oestradiol-17 beta had no effect on the activity of either hydroxylase under a variety of experimental conditions. These results clearly demonstrate that 1,25-dihydroxycholecalciferol, but not oestrogen, acts directly on the kidney cells to regulate the metabolism of 25-hydroxycholecalciferol.