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Biomedical subjects

A J Hay

Publications and source records attributed to A J Hay.

At least 55 records · Page 3Linked to original sources
PubMed1991

Structural characteristics of the M2 protein of influenza A viruses: evidence that it forms a tetrameric channel.

The evidence presented shows that the M2 protein of influenza A viruses exists in infected cells as a homotetramer composed of two disulfide-linked dimers held together by noncovalent interactions. The amphiphilic nature of the transmembrane alpha-helical domain is consistent with the protein forming a transmembrane channel with which amantadine, the specific anti-influenza A drug, interacts. Together these features provide a structural basis for the hypothesis that M2 has a proton translocation function capable of regulating the pH of vesicles of the trans-Golgi network, a role important in promoting the correct maturation of the hemagglutinin glycoprotein.

Animals↗
PubMed1991

Virulence of rimantadine-resistant human influenza A (H3N2) viruses in ferrets.

The influence of rimantadine-resistance mutations on the virulence of human H3N2 viruses in ferrets was examined. The similarities in virulence of the drug-resistant mutants with single amino acid substitutions at three different locations, 27, 30, and 31, within the M2 sequence and their corresponding sensitive wild-type isolates contrasted with differences in virulence between the three pairs of viruses. These data provide further evidence that rimantadine-resistant viruses that emerge during treatment of patients with the drug are unaltered both in their growth characteristics and virulence.

Animals↗
PubMed1991

The specific inhibition of influenza A virus maturation by amantadine: an electron microscopic examination.

Amantadine specifically inhibits the release of virus particles from cells infected with the Rostock (H7N1) strain of influenza A virus, apparently as a consequence of a membrane protein M2-mediated conversion of haemagglutinin (HA) to its low pH conformation. Electron microscopic observations, together with immunogold labelling, showed that amantadine action does not alter the distribution of HA on the cell surface nor does it prevent the formation of budding virus particles. It was not possible, however, to discern whether low pH HA inhibited the final stage in virus maturation, i.e. pinching off, or simply prevented release of fully formed particles.

Amantadine↗
PubMed1991

Recovery of drug-resistant influenza A virus during therapeutic use of rimantadine.

The therapeutic activity of rimantadine and its relationship to the shedding of drug-resistant influenza A virus were assessed in two randomized, double-blind, placebo-controlled trials involving patients with laboratory-documented influenza A virus (H3N2 subtype) illness of 2 days' duration or less. In a family-based study, rimantadine treatment for 10 days (24 children and adults) was associated with significant decreases in the number of days to a 50% reduction in symptoms (mean difference, 2.5 days), days of fever (1.6 days), and days of restricted activity (1.5 days) compared with the results obtained with placebo-treated patients (32 children and adults). Drug-resistant virus was recovered from eight (33%) of the rimantadine recipients on day 5. No differences in patient demographics or illness severity at the time of enrollment in the study were apparent between those who shed resistant virus and those who did not. Illness resolution tended to be slower in those who shed resistant virus compared with that in those who did not. In a study of adults treated for 5 days (six treated with rimantadine, six treated with placebo), resistant virus was recovered in three rimantadine recipients by day 3 of treatment. The results indicate that drug-resistant influenza A virus (H3N2) can be recovered from rimantadine-treated children and adults as early as 2 days after starting treatment, but that rimantadine retains a net therapeutic benefit compared with that of placebo.

Adolescent↗
PubMed1990

Study of the mode of action and site-specificity of the endo-(1----4)-beta-D-glucanases of the fungus Penicillium pinophilum with normal, 1-3H-labelled, reduced and chromogenic cello-oligosaccharides.

The modes of action of the five major endo-(1----4)-beta-D-glucanases (I, II, III, IV and V) purified from Penicillium pinophilum cellulase were compared by h.p.l.c. analysis, with normal, 1-3H-labelled and reduced cello-oligosaccharides and 4-methylumbelliferyl glycosides as substrates. Significant differences were observed in the preferred site of cleavage even when substrates with the same number of glycosidic bonds were compared. Thus, although endoglucanase I was unable to attack normal cello-oligosaccharides shorter than degree of polymerization 6, it hydrolysed reduced cellopentaose to yield cellotriose and cellobi-itol, and it produced cellotriose and 4-methylumbelliferyl glucoside from 4-methylumbelliferyl cellotetraoside. Endoglucanase IV hydrolysed [1-3H]cellotriose but did not attack either cellotri-itol or 4-methylumbelliferyl cellobioside. These and other anomalous results indicated clearly that modification of the reducing glycosyl residue on the cello-oligosaccharides induces in an apparent change in the mode of action of the endoglucanases. It is suggested that, although cello-oligosaccharide derivatives are useful for differentiating and classifying endoglucanases, conclusions on the mechanism of cellulase action resulting from these measurements should be treated cautiously. Unequivocal information on the mode of endoglucanase action on cello-oligosaccharides was obtained with radiolabelled cello-oligosaccharides of degree of polymerization 3 to 5. Indications that transglycosylation was a property of the endoglucanases were particularly evident with the 4-methylumbelliferyl cello-oligosaccharides. Turnover numbers for hydrolysis of the umbelliferyl cello-oligosaccharides were calculated, and these, along with the other analytical data collected on the products of hydrolysis of the normal, reduced and radiolabelled cello-oligosaccharides, suggested that the various endoglucanases had different roles to play in the overall hydrolysis of cellulose to sugars small enough to be transported through the cell membrane.

Bacterial Proteins↗
PubMed1990

Specific structural alteration of the influenza haemagglutinin by amantadine.

Amantadine hydrochloride specifically blocks the release of virus particles from H7 influenza virus infected cells. This appears to be the direct consequence of an amantadine induced change in the haemagglutinin (HA) to its low pH conformation. The effect is indirect and mediated via interaction of the drug with the M2 protein since mutants altered in this component alone are insensitive to amantadine. The timing of drug action, some 15-20 min after synthesis, and its coincidence with proteolytic cleavage indicates that the modifications to HA occur late during transport but prior to insertion into the plasma membrane. Reversal by mM concentrations of amines and 0.1 microM monensin indicates that amantadine action causes a reduction in intravesicular pH which triggers the conformational change in HA. We conclude, therefore, that the function of M2 inhibited by amantadine is involved in counteracting the acidity of vesicular compartments of the exocytic pathway in infected cells and is important in protecting the structural integrity of the acid-sensitive glycoprotein.

Amantadine↗
PubMed1990

Palmitoylation of the influenza A virus M2 protein.

The M2 proteins of a variety of influenza A viruses of different subtypes were shown to possess associated palmitate. Susceptibility to removal by reduction or treatment with hydroxylamine is consistent with attachment via a thioester linkage to cysteine. The absence of the acyl group from the M2 proteins of several equine viruses of the H3N8 subtype correlates with the replacement of cysteine 50 with phenylalanine and points to this as the site of palmitate attachment.

Amino Acid Sequence↗
PubMed1990

Anti-influenza virus activity of the compound LY253963.

The compound LY253963 (1,3,4-thiadiazol-2-ylcyanamide) inhibited the in vitro replication of representative influenza A and B viruses in Madin-Darby canine kidney (MDCK) cells at concentrations of 1-3.2 micrograms/ml. The yield of an influenza A (H3N2) virus in primary rhesus monkey kidney (RMK) cells was inhibited at 0.1-0.3 micrograms/ml. However, similar concentrations were inhibitory for the growth of uninfected MCDK or RMK cells. Combination drug studies generally found indifferent interactions between LY253963 and ribavirin or rimantadine. In timing of additional studies, hemagglutinin expression was inhibited to the greatest extent when LY253963 exposure was begun at least 8 h before viral infection, which suggested either slow uptake or intracellular metabolism of LY253963 to an active form. Virus-specific protein synthesis was inhibited to a greater extent by ribavirin 10 micrograms/ml or rimantadine 1 microgram/ml than by LY253963 10 micrograms/ml. No drug-resistant mutants were detected during serial passage of an influenza A (H3N2) virus in the presence of LY253963 1-16 micrograms/ml. In summary, we found that LY253963 inhibited influenza A and B virus replication in several cell types, but that it was associated with cytostatic effects at low concentrations. These studies failed to identify a selective anti-influenza action.

Antiviral Agents↗
PubMed1989

Emergence and apparent transmission of rimantadine-resistant influenza A virus in families.

To determine whether rimantadine can protect family members from acquiring influenza A viral illness and to assess the possible selection of drug-resistant strains of virus, we conducted a randomized, double-blind, placebo-controlled study in three communities during two influenza seasons. When influenza A occurred in a family, the members (including the index patient) were given either rimantadine (adult oral dose, 200 mg per day) or placebo for 10 days. The presence of illness was monitored by daily recording of symptoms and temperature measurements; infection was determined by isolation of the virus and by serologic studies. Among households with documented influenza A infections, symptomatic illness occurred in one or more contacts in 10 of 28 families treated with rimantadine and in 10 of 209 families treated with placebo. Asymptomatic secondary influenza A infections were found in five families assigned to receive rimantadine and in four families assigned to receive placebo. Rimantadine-resistant strains of influenza A virus (H3N2 subtype) with mutations consisting of single amino acid changes in the M2 protein (residue 27, 30, or 31) were recovered from eight index patients and five contacts treated with rimantadine. There was apparent transmission of drug-resistant strains of virus in six contacts with secondary illnesses in five families. We conclude that when index patients are treated concurrently, rimantadine is ineffective in protecting household members from influenza A infection. If rimantadine is used for both treatment and postexposure prophylaxis in families, rapid selection and apparent transmission of drug-resistant influenza A viruses can occur.

Adamantane↗
PubMed1988

Soluble lignin-carbohydrate complexes from sheep rumen fluid: their composition and structural features.

Lignin-carbohydrate complexes, isolated from cell-free rumen fluid of sheep, consisted of polyphenolic material in association with carbohydrate (5.5%) and protein (1.8%). No separation of carbohydrate from the other components could be effected. The complexes showed a bimodal distribution of molecular size with the higher-molecular-weight fraction richer in carbohydrate. Methylation analysis indicated a wide range of linkages and a high proportion of terminal sugars. Reducing sugars were found in the complexes, particularly in the low-molecular-weight fraction (approximately 25%), suggesting that ether linkages to the phenolics were also present.

Animals↗
PubMed1988

Genetic basis of resistance to rimantadine emerging during treatment of influenza virus infection.

The emergence of influenza A viruses which had acquired resistance to rimantadine during a clinical trial (C. B. Hall, R. Dolin, C. L. Gala, D. M. Markovitz, Y. Q. Zhang, P. H. Madore, F. A. Disney, W. B. Talpey, J. L. Green, A. B. Francis, and M. E. Pichichero, Pediatrics 80:275-282, 1987) provided the opportunity to determine the genetic basis of this phenomenon. Analysis of reassortant viruses generated with a resistant clinical isolate (H3N2) and the susceptible influenza A/Singapore/57 (H2N2) virus indicated that RNA segment 7 coding for matrix and M2 proteins conferred the resistant phenotype. Resistant viruses isolated from seven patients each contained a single change in the nucleotide sequence coding for the M2 protein which resulted in substitutions in amino acid 30 (two viruses) or 31 (five viruses) in the transmembrane domain of the molecule. These changes occurred in locations identified in influenza viruses selected for resistance to amantadine in tissue culture and indicate a common mechanism of action of the two compounds in cell culture and during chemotherapeutic use.

Adamantane↗
PubMed1986

Molecular basis of resistance of influenza A viruses to amantadine.

Amantadine (1-aminoadamantane hydrochloride) is effective in the prophylaxis and treatment of influenza A infection. In tissue culture this selective, strain-specific antiviral inhibits either the initiation of infection or virus assembly. The basis of these actions is similar and both the haemagglutinin and M2 proteins are implicated suggesting that amantadine interferes with their functions or the interactions between these two virus proteins. Mutations which confer resistance to amantadine are restricted to four amino acids within a hydrophobic sequence of M2 indicating that the primary target of drug action is the membrane-associated portion of this molecule.

Amantadine↗
PubMed1985

The molecular basis of the specific anti-influenza action of amantadine.

Amantadine (1-aminoadamantane hydrochloride) is effective in the prophylaxis and treatment of influenza A infections. In tissue culture this selective, strain-specific antiviral activity occurs at relatively low concentrations (5 microM or less), which inhibit either the initiation of infection or virus assembly. The data reported here demonstrate that the basis of these actions is similar and resides in the virus-coded M2 membrane protein, the product of a spliced transcript of RNA segment 7. Mutations which confer resistance to amantadine are restricted to four amino acids within a hydrophobic sequence, indicating that the drug is targetted against the putative membrane-associated portion of the molecule. The influence of the virus haemagglutinin on the amantadine sensitivity of virus strains implies that the drug may interfere with interactions between these two virus proteins.

Amantadine↗
PubMed1985

Fusion mutants of the influenza virus hemagglutinin glycoprotein.

The influenza virus hemagglutinin (HA) mediates viral entry into cells by a low pH induced membrane-fusion event in endosomal vesicles. Mutant viruses with altered pH dependence for both hemolysis and the HA conformational change required for fusion were selected for their ability to grow in cells treated with amantadine hydrochloride, which raises the endosomal pH. The amino acid sequence and three-dimensional location of 19 substitutions on the HA are reported. The mutations fall into two groups, one that results in the destabilization of the pH 7.0 location of the hydrophobic N-terminal HA2 peptide, and a second that results in the alteration of intersubunit contacts, suggesting a large distortion or disruption of these contacts in the "fusion-active" conformation.

Amantadine↗