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Biomedical subjects

D McCahon

Publications and source records attributed to D McCahon.

At least 19 recordsLinked to original sources
PubMed2005

Self management of oral anticoagulation: randomised trial.

OBJECTIVE: To determine the clinical effectiveness of self management compared with routine care in patients on long term oral anticoagulants. DESIGN: Multicentre open randomised controlled trial. SETTING: Midlands region of the UK. PARTICIPANTS: 617 patients aged over 18 and receiving warfarin randomised to intervention (n = 337) and routine care (n = from 2470 invited; 193/337 (57%) completed the 12 month intervention. INTERVENTION: Intervention patients used a point of care device to measure international normalised ratio twice a week and a simple dosing chart to interpret their dose of warfarin. MAIN OUTCOME MEASURE: Percentage of time spent within the therapeutic range of international normalised ratio. RESULTS: No significant differences were found in percentage of time in the therapeutic range between self management and routine care (70% v 68%). Self managed patients with poor control before the study showed an improvement in control that was not seen in the routine care group. Nine patients (2.8/100 patient years) had serious adverse events in the self managed group, compared with seven (2.7/100 patient years) in the routine care arm (chi2(df = 1) = 0.02, P = 0.89). CONCLUSION: With appropriate training, self management is safe and reliable for a sizeable proportion of patients receiving oral anticoagulation treatment. It may improve the time spent the therapeutic range for patients with initially poor control. Trial registration ISRCTN 19313375.

Administration, Oral↗
PubMed2004

Point of care testing for INR monitoring: where are we now?

Point of care (POC, or near patient) testing for measurement of the international normalized ratio (INR) has facilitated the devolution of service delivery from the traditional hospital outpatient setting. However it must be undertaken within the confines of safe practice involving quality control procedures. The evaluation of INR POC tests should be closely related to the clinical issues of management and, specifically, improving the quality of care. One benefit of POC testing is in the increased motivation that some practitioners feel, being able to perform diagnostic tests without sending samples to a laboratory. POC for INR testing within primary care eliminates the delay in waiting for the result to be processed by the hospital laboratory, and the subsequent delay in informing the patient of their dosing advice. This review describes the utilization of POC testing outside the laboratory setting to develop models of care for oral anticoagulation management.

Anticoagulants↗
PubMed1990

Sequence analysis of monoclonal antibody resistant mutants of type O foot and mouth disease virus: evidence for the involvement of the three surface exposed capsid proteins in four antigenic sites.

Sequence analysis of monoclonal antibody resistant mutants of type O foot and mouth disease virus has been performed. Distinct clusters of amino acid substitutions conferring resistance to neutralization at each of the four previously defined antigenic sites (McCahon et al., 1989, J. Gen. Virol. 70, 639-645) have been identified. One site corresponds to the well-known 140-160 region of VP1, a second site is also on VP1, one site is on VP2, and the fourth site is on VP3. All of the amino acid substitutions identified are located on the surface of the virus. Despite the differences in three-dimensional structure between FMDV and other picornaviruses the neutralizing antigenic sites occur in analogous positions on the capsid surface.

Animals↗
PubMed1989

Evidence for at least four antigenic sites on type O foot-and-mouth disease virus involved in neutralization; identification by single and multiple site monoclonal antibody-resistant mutants.

Neutralizing monoclonal antibodies raised against type O foot-and-mouth disease virus have been characterized on the basis of their reactivity with a panel of single site monoclonal antibody-resistant mutants which had defined three antigenic sites. Five antibodies neutralized all these mutants, but by selecting further single site mutants with one of these antibodies it was possible to define a fourth site involved in virus neutralization. Two monoclonal antibodies still neutralized these mutants and all multiple site resistant mutants. One multiple site resistant mutant was resistant to neutralization at each of four antigenic sites but was still efficiently neutralized by type O convalescent cattle sera. The relationship between sites recognized by different monoclonal antibodies generated in different laboratories is discussed.

Animals↗
PubMed1987

Epitopes on foot-and-mouth disease virus particles. I. Topology.

Monoclonal antibodies (MAb) against an O1 Suisse isolate of FMDV were used to identify epitopes on the virus particle and to determine their relative function. Six major antigenic sites containing one or more epitopes were identified using competition ELISA. An epitope relationship is proposed consisting of a trypsin-sensitive sequential site, termed B2/D9, from the codings for the MAb which reacted with it, which was associated with virus infectivity and is probably at or near to the cell-binding site of the virion; a trypsin-resistant, conformational site 1C6/4C9 MAb reaction at which also resulted in neutralization of virus infectivity; a second trypsin-resistant, conformational site 3C8, where again MAb reaction neutralised virus infectivity; a third trypsin-resistant, conformational site 6C3/2G5, at which MAb-dependent neutralisation of virus infectivity was inefficient; a site 3G4, the expression of which was impaired but not destroyed by trypsin treatment, and was not related to virus infectivity; an internal site A8, which appears to be a "12S subunit-specific" site. This work clearly demonstrates for the first time that both trypsin-sensitive and trypsin-resistant neutralisable (infectivity-associated) sites exist on the FMDV particle, and only one of these can be related to the sequential site used to formulate current FMDV peptide vaccines.

Antibodies, Monoclonal↗
PubMed1987

Neutralization of foot-and-mouth disease virus can be mediated through any of at least three separate antigenic sites.

Seven neutralizing monoclonal antibodies were used to characterize 30 escape mutants of a type O foot-and-mouth disease (FMD) virus (O1 Kaufbeuren) selected with the five most active antibodies. Three non-overlapping antigenic sites were found by ELISA and cross-neutralization studies. Within two of the sites the epitopes of two or more monoclonal antibodies overlapped. Two of the sites were conformation-dependent and could not be detected on virus subunits or isolated denatured polypeptides. The third site was less conformation-dependent since the appropriate monoclonal antibodies were able to bind to 12S subunits, isolated VP1 protein and a synthetic peptide containing residues 141 to 160 of VP1 in ELISA. Electrofocusing of mutants of that site showed a high frequency of electrophoretic alterations in VP1. The sequence of most or all of the VP1 coding region of 10 escape mutants of that site plus three parental isolates was determined by primer extension sequencing. At least five amino acids were found to be involved but in only one case (residue 148 of VP1) did a change at that residue produce complete resistance to neutralization. Partial resistance was produced by changes at residues 144, 154 or 208 of VP1 or another residue(s), as yet undefined, that is probably in one of the other capsid polypeptides. Thus the site defined by these mutants was made up of at least three regions, the region involving residues 144 to 154 of VP1, the region encompassing residue 208 from the COOH terminus of VP1, plus a region, probably of VP2 or VP3, encompassing the undefined residue(s).

Amino Acid Sequence↗
PubMed1985

Isolation and biochemical characterization of intertypic recombinants of foot-and-mouth disease virus.

Recombinants were isolated between two European serotypes (O and A) and between two of the most distantly related serotypes (O from Europe and SAT2 from Africa) using appropriate ts mutants in an infectious centre assay. The recombinants were characterised by electrofocusing of their induced proteins and by RNase-T1 fingerprinting of their RNA. The approximate location of the cross-over event in each recombinant was determined by sequencing the unique distinguishable O or A oligonucleotides and locating them within the known genome sequence. Nine different types of recombinant were identified from the two types of cross (O X A and O X SAT) and all had a single cross-over in the middle or 3' half of the genome, i.e. in the nonstructural coding region. Recombination between the most distantly related viruses (O X SAT2) appeared to occur at a lower frequency than recombination between serotypes of the same group (O X A). A higher incidence of recombinant proteins with unique pI was also observed in the O X SAT2 crosses.

Aphthovirus↗
PubMed1985

Multiple sites of recombination within the RNA genome of foot-and-mouth disease virus.

Recombinant foot-and-mouth disease viruses were isolated from cells infected with a mixture of temperature-sensitive (ts) mutants belonging to different subtype strains. In order to select for recombination events in many different regions of the genome, crosses were performed between various pairs of mutants, with ts mutations in different regions of the genome. ts+ progeny were analysed by electrofocusing virus-induced proteins and RNase T1 fingerprinting of their RNA. All but 5 out of 43 independent isolates, from nine crosses, proved to have recombinant RNA genomes. Maps of these genomes, based on a knowledge of the locations of the unique oligonucleotides, were constructed. Most could be interpreted as being the products of single genetic cross-overs, although three recombinants were formed by two cross-overs each. Cross-overs in at least twelve distinct regions of the genome were identified. This evidence of a large number of recombination sites suggests that RNA recombination in picornaviruses is a general, as opposed to a site-specific, phenomenon.

Aphthovirus↗
PubMed1985

Recombination and oligonucleotide analysis of guanidine-resistant foot-and-mouth disease virus mutants.

Guanidine resistance (gr) mutations of foot-and-mouth disease virus were mapped by recombining pairs of temperature-sensitive mutants belonging to different subtypes. In each cross, one parent possessed a gr mutation. Recombinants were isolated by selection at the nonpermissive temperature and assayed for the ability to grow in the presence of guanidine. From the progeny of three crosses, four different types of recombinant were distinguished on the basis of protein composition and RNA fingerprint. The sequences of the RNase T1-resistant oligonucleotides were determined and located in the full-length sequence of foot-and-mouth disease virus. The resulting maps show that (i) each recombinant was generated by a single genetic crossover, and (ii) both of the gr mutations studied were located within an internal 2.9-kilobase region which spans the P34 gene. This supports our hypothesis that guanidine inhibits the growth of foot-and-mouth disease virus by acting on nonstructural polypeptide P34. Additional evidence was provided by RNA fingerprinting gr mutants. In two of four cases the gr mutation was associated with a change in an oligonucleotide located near the 3' end of the P34 gene; in one of these the nucleotide substitution was identified.

Aphthovirus↗
PubMed1983

Four independent antigenic determinants on the capsid polypeptides of aphthovirus.

Four independent antigenic determinants in the virus capsid have been defined in radioimmunoassay tests using antisera prepared against isolated structural polypeptides VP1, 2 and 3. Only one determinant was detected on the intact particle and it was contained within VP1 (called the VP1-A determinant). Three determinants were found on the 12S subparticle, two contained within VP1 (VP1-A and VP1-B determinants) and one contained within VP2 (VP2 determinant). The fourth determinant was contained within VP3 (VP3 determinant) and could only be detected when the virus was disrupted to individual polypeptides. It is concluded that the VP1-A determinant is likely to be of epidemiological importance since (i) it was present on the intact virion, (ii) variation at this determinant was detected with heterologous field strains, (iii) it contained a determinant responsible for the induction of neutralizing antibodies and (iv) it was an antigenic component of the trypsin-sensitive region of VP1 which has been shown previously by several workers to be of critical importance in the immunogenicity of the virus.

Antibodies, Viral↗
PubMed1983

Location of an immunizing determinant within polypeptide VP1 of type O aphthovirus.

VP1 is the only structural polypeptide of aphthovirus able to stimulate the production of neutralizing antibody. The region of VP1 responsible for this activity was located by testing various proteolytic fragments of VP1 for their ability to compete for virus-specific antibodies in serum raised against the intact polypeptide. No antigenic activity could be detected in VP1 fragments isolated from trypsin-treated virus. Controlled digestion revealed that trypsin cleaved VP1 in four places in a preferred order, whereas chymotrypsin cut at a maximum of two sites. The initial cuts by the two proteases were made very close to each other, and in each case resulted in a greatly reduced affinity of the VP1 fragments for virus-specific antibodies in anti-VP1 serum. In contrast, aphthovirus was resistant to Staphylococcus aureus V8 protease, and treatment of isolated VP1 with this protease generated a peptide of mol. wt. 8500 which competed efficiently with virus for antiserum to VP1 and for an absorbed antiviral serum specific for trypsin-sensitive sites. The results indicate that these antisera interact specifically with aphthovirus at a single antigenic determinant located on VP1 approximately two-thirds of the way along the polypeptide sequence.

Amino Acid Sequence↗
PubMed1982

Recombination in RNA.

The aphthovirus genome consists of a single molecule of single-stranded RNA that encodes all the virus-induced proteins. We isolated recombinant aphthoviruses from cells simultaneously infected with temperature-sensitive mutants of two different subtype strains. Analysis of the proteins induced by 16 independently generated recombinants revealed two types of protein pattern, which were consistent with single genetic crossovers on the 5' side and 3' side, respectively, of the central P34-coding region. Recombinants invariably inherited all four coat proteins from the same parent, and novel recombinant proteins were not observed. RNAase T1 fingerprints of virus RNA, prepared from representatives of each recombinant type, confirmed the approximate crossover sites that had been deduced from the inheritance of proteins. These fingerprints provide molecular evidence of recombination at the level of RNA and demonstrate the potential of RNA recombination for producing genetic diversity among picornaviruses.

Aphthovirus↗
PubMed1982

Biochemical evidence of recombination within the unsegmented RNA genome of aphthovirus.

Four different pairs of temperature-sensitive mutants, derived from the same strain of aphthovirus, were crossed by using an infectious center recombination test. Each parental mutant carried an unselected marker affecting the isoelectric point of a virus-coded polypeptide; progeny of the crosses, able to grow at the nonpermissive temperature, were screened for these unselected markers. Polypeptide charge was shown to be a stable, inheritable character, and three of the four crosses yielded genetic recombinants that possessed the polypeptide marker from both parents. Peptide fingerprinting and high-resolution isoelectric focusing of the polypeptides ruled out the explantation that these viruses were generated by mutation.

Aphthovirus↗
PubMed1981

Temperature-sensitive RNA polymerase mutants of a picornavirus.

Temperature-sensitive (ts) RNA polymerase mutants of a picornavirus are reported. Two foot-and-mouth disease virus (FMDV) mutants designated ts 22 and ts 115 have been characterized. As judged by isoelectric focusing, both have charge alterations in P56a, the FMDV RNA polymerase protein. Virus RNA synthesis in cells infected with the mutants is severely impaired at the nonpermissive temperature. RNA polymerase purified from baby hamster kidney cells infected with these mutants exhibits a marked ts transcribing activity in vitro. Spontaneous revertants of both mutants have P56a polypeptides that are indistinguishable from the parental proteins on the basis of charge. The revertants regain the ability to synthesize virus RNA in vivo at the nonpermissive temperature. RNA polymerase purified from the revertants remains transcriptionally active at the nonpermissive temperature.

Animals↗
PubMed1981

A sensitive method for the detection and isolation of recombinants of foot-and-mouth disease virus.

Recombination between temperature-sensitive (ts) mutants of foot-and-mouth disease (FMD) virus was examined, using an infectious centre technique that was more sensitive (approx. 30-fold) than the conventional virus yield test. The test involved a brief incubation of the mixedly infected cells at the permissive temperature to allow recombination to occur followed by assay at the restrictive temperature to select for those cells in which recombination had occurred. With crosses involving widely separated mutations, as many as 28% of the infected cells produced presumptive recombinant plaques. Since each plaque was the result of an independent event, large numbers of different presumptive recombinants could be isolated for further study. Analysis of presumptive recombinant plaques from a variety of crosses showed that, in general, the virus produced had the properties expected of recombinants. An approximate correlation was found between genetic distance, as determined in the yield recombination test, and the percentage of recombinant infectious centres observed. The phenomenon was very sensitive to the balance between the input multiplicities of the two parent viruses and occurred very early in virus replication. The test has considerable potential for the study of genetic interactions in FMD virus, but it would be surprising if this potential was limited to picornaviruses.

Animals↗