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Biomedical subjects

D J Rowlands

Publications and source records attributed to D J Rowlands.

At least 37 records · Page 2Linked to original sources
PubMed1994

A comparison of early mortality and morbidity after single and bilateral internal mammary artery grafting with the free right internal mammary artery.

OBJECTIVE: To compare differences in early mortality and morbidity in patients receiving a single internal mammary artery graft (SIMA) with those receiving bilateral internal mammary artery grafts (BIMA) with a free right internal mammary artery (RIMA). DESIGN: Retrospective analysis of 150 patients undergoing BIMA grafting between 1989-1992 who were carefully matched with 150 patients undergoing SIMA grafting between 1987-1992 for known cardiovascular risk factors, extent of coronary disease, left ventricular function, and number of coronary grafts. Operative variables noted included aortic cross clamp time and bypass time. Postoperative cardiac, respiratory, and wound complications were also noted. RESULTS: Operative mortality was 2% in the SIMA group and 1.3% in the BIMA group (NS). Other than the prevalence of ventricular arrhythmias (P = 0.025), which were more common in the BIMA group, there were no significant differences between the two groups in terms of postoperative morbidity. At median (interquartile range) follow up of 27.94(0.86) and 23.94(0.74) months for the SIMA and BIMA groups respectively there were no deaths. 87% of the SIMA group and 91% of the BIMA group were free of symptoms at follow up. CONCLUSIONS: The earlier fears regarding increased early mortality and morbidity after BIMA surgery were not confirmed by this study. All patients receiving both mammary arteries had a free rather than pedicle right internal mammary graft. The early mortality and morbidity reported here compares favourably with previous reports on the use of a pedicle graft.

Adult↗
PubMed1993

Antigen processing and presentation of human rhinovirus to CD4 T cells is facilitated by binding to cellular receptors for virus.

Human rhinovirus serotypes (HRV) fall into two distinct groups, major and minor, by virtue of their cell receptor-binding ability. In this study minor receptor-binding group viruses are demonstrated to bind directly to cells of the murine immune system, including lymphoid dendritic cells which act as antigen-presenting cells, although they do not produce a productive infection in murine cells. This binding is specific and can be blocked by other serotypes of minor-group HRV. Pre-treatment of HRV 1A, a minor-group virus, with HRV 1A-specific antibodies inhibited the cellular proliferation of murine virus primed T helper cells, whereas antibody treatment of HRV 15, a non-binding major serotype, gave no inhibition. The cell binding ability of minor-group HRV played a role in the overall immunogenicity of this virus group, which was shown to be enhanced compared to the immunogenicity of major-group viruses in mice.

Adjuvants, Immunologic↗
PubMed1993

Epitope analysis of the T cell response to a complex antigen: proliferative responses to human rhinovirus capsids.

Understanding the factors which regulate the repertoire of a T cell response is important when selecting T helper cell epitopes for inclusion in synthetic viral vaccines. In this study we have examined the T cell response to human rhinovirus (HRV) type 1 A in a mouse model system, using a comprehensive set of synthetic peptides which span all four of the proteins which make up the HRV capsid. This constitutes the first study to use a set of peptides covering the entire sequence of all structural proteins of any virus. This study identifies the major proliferative (CD4) T cell epitopes within the minor receptor group HRV 1 A, and analyzes these epitopes with relation to their location within the three-dimensional structure of the virus. The proliferative response to HRV is highly selective, with strong responses to only a very small number of epitopes, many of which are grouped together within restricted areas of the primary structure of the HRV proteins. The repertoire of the response is almost entirely specific to the major histocompatibility complex haplotype of the host. The major T cell epitopes are spatially distinct from the sites of the major antibody recognition sites, and are buried within the viral capsid. In striking contrast to the antibody responses, the T cell responses are highly cross-reactive against a wide variety of viral serotypes.

Amino Acid Sequence↗
PubMed1993

The nature and spatial distribution of amino acid substitutions conferring resistance to neutralizing monoclonal antibodies in human rhinovirus type 2.

A total of 38 neutralization escape mutant viruses have been selected from a cloned stock of human rhinovirus serotype 2 (HRV-2), using either of two monoclonal antibodies (MAbs) which recognize overlapping epitopes as judged by competition binding. The mutant viruses were analysed for their sensitivity to a panel of antiviral MAbs by antibody binding and virus neutralization assays. The position and nature of the selected mutations was determined by sequencing of the virus RNAs, and the location of the substituted amino acids on the three-dimensional structure of the virus predicted from the co-ordinates determined for the closely related HRV-1A. Escape from neutralization could be attributed to single amino acid substitutions in all but one case, which had a deletion of four amino acids. In all cases in which the same mutation was found more than once, these mutations were transitions. The ratio of transition to transversion mutations was about 5:1 overall or about 1.7:1 if only unique substitutions are considered. Each antibody selected for a discrete cluster of mutations and the area of these clusters was considerably less than that determined to be in contact with antibodies from X-ray crystallographic analyses of antibody/protein complexes. One mutation did not occur within the cluster of others selected with the same antibody. This substitution occurred at the base of a small loop and may cause conformational changes at the virus surface.

Amino Acids↗
PubMed1993

Characterization of monoclonal antibodies raised against a synthetic peptide capable of inducing a neutralizing response to human rhinovirus type 2.

Synthetic peptides incorporating the derived amino acid sequence of VP2 residues 156 to 170 of human rhinovirus type 2 (HRV2) have previously been shown to elicit antibodies that neutralize virus infectivity. The proportion of virus-reactive antibodies present in polyclonal antisera to these peptides is, however, very low. Moreover, neutralization titrations of such antisera correlate poorly with other assays of either anti-virus or anti-peptide activity, suggesting the presence of antibodies with different specificities. To investigate these findings further, we produced a panel of monoclonal antibodies (MAbs) to VP2 peptides of residues 156 to 170 and characterized their reactions with a range of antigens in ELISA, precipitation and neutralization titrations. All the MAbs obtained recognized the homologous peptide, but could be divided into four main reaction groups according to their specificity for viral antigens. Antibodies in the first group recognized and neutralized native virus, apparently by preventing attachment to cells. A second group of MAbs bound to intact particles with similar affinities to the first group, but failed to neutralize infectivity. Antibodies in the third group recognized virus only after capsid distortions incurred by heating or by previous reaction with polyclonal antibodies. The fourth group comprised MAbs that were mainly peptide-specific. Some possible applications of anti-peptide MAbs to improving the design of peptide immunogens are considered.

Amino Acid Sequence↗
PubMed1993

The role of coronary angioplasty in the management of coronary artery disease.

Coronary angioplasty is well established as a treatment modality for coronary artery disease. Clinical experience leaves no doubt that it can be very effective in relieving symptoms in patients with unstable angina and with chronic stable angina. There are, at present, no controlled trials to demonstrate its efficacy, though several are under way. In straightforward cases the initial success rate is about 90%, but for each lesion dilated, there is about a 30% chance of significant re-stenosis. Re-stenosis (which is the main chronic complication) usually occurs early--often within a few weeks of the procedure--and it rarely develops later than six months after the procedure. Acute closure of the dilated artery (usually within an hour or two of procedure) is the most feared acute complication and is the main factor contributing to the 0.2% acute mortality rate and to the 1-5% risk of emergency coronary artery bypass grafting. The procedural risk does not increase progressively with serial interventions (in contrast to coronary artery surgery). Furthermore, angioplasty is often undertaken following surgery when stenoses have developed within the grafts, at the graft-vessel anastomosis, in the native vessels distal to the graft insertion or in native ungrafted vessels. Angioplasty is less costly than coronary surgery, although the 30% re-stenosis rate implies a requirement for additional interventions as a result of which the cost differential is not as great it initially appears.

Angioplasty, Balloon, Coronary↗
PubMed1992

How can peptide vaccines work?

Peptide antigens frequently induce antibodies which recognise the denatured form of a protein from which their sequences are derived. However, the ability to induce antibodies which crossreact with the native, fully folded form of the protein is less commonly observed. Although there is a growing number of examples in which this is the case, the ability to predict peptides having this property is extremely limited. Given the large surface areas involved in antibody/antigen interaction it is surprising that peptides could ever induce antibodies which would recognise the native protein well enough to have biological activity, such as the neutralization of infectivity. A mechanism is proposed to explain such observations which is compatible with many of the properties of antipeptide antibodies.

Antibodies, Viral↗
PubMed1992

Comparison between in vitro neutralization titres and in vivo protection against homologous and heterologous challenge induced by vaccines prepared from two serologically distinct variants of foot-and-mouth disease virus, serotype A22.

Guinea-pigs were challenged with homologous or heterologous strains of foot-and-mouth disease virus (FMDV) following vaccination with baby hamster kidney (BHK) monolayer cell-adapted or BHK suspension cell-adapted strains of FMDV serotype A22 Iraq 24/64. The protection afforded by these vaccines was analysed as a function of antigen dose and the in vitro serum virus neutralization titres achieved. The results show that the level of neutralizing antibody induced that afforded 50% protection was similar for both vaccines in homologous or heterologous challenge situations. However, although the dose of antigen required to achieve this titre against homologous virus was similar for the two vaccines, approximately 20-fold more of the suspension cell-adapted virus was required to elicit a protective titre against heterologous challenge compared to the dose of monolayer cell-adapted virus required. A synthetic peptide representing the amino acid sequence 135 to 167 of VP1, which is identical in the A22 Iraq 24/64 variant viruses, was shown to induce protection against both homologous and heterologous virus challenge.

Animals↗
PubMed1991

Foreign epitopes in immunodominant regions of hepatitis B core particles are highly immunogenic and conformationally restricted.

The presentation of heterologous amino acid sequences on the surface of hepatitis B core antigen (HBcAg) particles has been studied using a defined linear neutralization site from human rhinovirus (HRV). Previous work has shown that fusion particles, in which the HRV peptide sequence is linked to the amino terminus of the HBcAg protein, induce excellent immune responses in experimental animals. Using predictive models of HBcAg particulate structure and the approximate location of the major immunogenic regions we have designed and constructed bacterial expression vectors which direct synthesis of chimeric particles in which heterologous sequences are presented within an immunodominant area on the particle. Immunological responses to the heterologous peptide sequence are improved by at least tenfold when compared with amino terminal fusions of the same peptide sequence to HBcAg. Moreover, the restriction placed on the heterologous peptide by its linkage at both ends within the HBcAg protein results in a more constrained structure. In the case of the rhinovirus peptide sequence this results in an antigenic conformation more closely resembling that on the native virus particle. Such a system lends itself well as a general approach to the induction of high titre antibodies against defined epitopes.

Amino Acid Sequence↗
PubMed1991

Proliferative responses of T cells primed against human rhinovirus to other rhinovirus serotypes.

Lymphocytes from mice immunized with human rhinovirus (HRV) serotypes 1A or 15 proliferated in vitro in response to HRV and the activated cells were shown to be helper T (Th) cells. Lymphocytes from mice primed with HRV-1A responded to seven of eight heterologous virus serotypes, the responses to other minor cell receptor group viruses being greater than to those belonging to the major cell receptor group. A similar bias was seen with cells from mice primed with HRV-15 in that they responded preferentially to other major receptor group viruses. This pattern of cross-serotype recognition was shown to be similar in three inbred mouse strains and was not dependent upon the major histocompatibility complex haplotype. These results have revealed that there are determinants within the viral proteins of a number of serotypes of HRV that are recognized by Th cells primed against a single HRV serotype. Thus, at the level of Th cell recognition of HRV, a cross-serotype reactivity is seen which is not reflected in the B cell antibody response to virus, which is generally highly serotype-specific.

Animals↗
PubMed1991

In vitro translation of hepatitis A virus subgenomic RNA transcripts.

A subgenomic cDNA clone from hepatitis A virus strain HM175, composed of the last eight nucleotides of the 5' non-translated region and the first 2248 nucleotides of the coding sequence (P1 region), was inserted into a vector under the control of the T7 promoter. Restriction enzyme digestion at sites within the structural region and subsequent transcription in vitro yielded RNA products which were translated efficiently in rabbit reticulocyte lysates to produce proteins of the predicted sizes. The translation products were specifically precipitated with antipeptide antisera; these reactions were not affected by denaturation of the antigens by boiling in 1% SDS. The translated proteins were also precipitated by antivirion antisera, but recognition was totally abolished following denaturation. Thus antivirion antisera recognized conformation-dependent epitopes expressed on the translated products exclusively.

Autoradiography↗
PubMed1991

Parameters influencing the attachment of hepatitis A virus to a variety of continuous cell lines.

We have investigated the interactions of purified radiolabelled hepatitis A virus (HAV) with a variety of continuous cell lines. Virus labelled either in vitro with radiolabelled iodine or in vivo with radiolabelled uridine bound to cells with similar efficiency. Attachment to BS-C-1 cells was calcium ion-dependent and this correlated with infectivity assay results. The cell tropism of HAV attachment was examined using cell suspensions and confluent cell monolayers at both 4 degrees C and 37 degrees C. The maximum level of attachment was observed at 4 degrees C with cells in suspension, but was severely inhibited by 2% foetal calf serum; these results again correlated with infectivity assays. The components of serum which inhibit attachment have been characterized by gel filtration chromatography, sucrose density gradient analysis, immunoprecipitation and Western blotting. The data show that such components are of high Mr and that the serum glycoprotein, alpha 2-macroglobulin, can partly mimic the inhibitory effect of whole serum.

Adsorption↗
PubMed1991

A CD strategy for the study of polypeptide folding/unfolding. A synthetic foot-and-mouth disease virus immunogenic peptide.

The circular dichroism spectrum of the 20-residue immunogenic peptide from the foot-and-mouth disease virus (VP1; 141-160 of serotype A, subtype 12) was solvent- and temperature-dependent. Careful solvent titration revealed two isodichroic points and plateaux consistent with stepwise unfolding of specific stable conformations. Variable temperature studies in cryogenic solvents and urea perturbation were consistent with the existence of three conformational moieties, the left-handed extended helix, the alpha-helix, and the 3(10) helix. The number of residues in each helix was confirmed by CD spectral simulations. The strategy described here can be used to determine the components of a conformational equilibrium and their statistical weights, to study peptide folding and unfolding and to determine the bioactive conformation(s) of linear peptides. The conclusions were supported by 2D-NMR studies. A new mechanism for the stabilization of left-handed extended helices and destabilization of alpha-helices by urea is proposed. The structure of the peptide as resolved by CD spectroscopy is of particular significance since the conformation of this antigenic sequence in situ has so far not been solved by X-ray crystallography.

Amino Acid Sequence↗
PubMed1990

Immunological properties of hepatitis B core antigen fusion proteins.

The immunogenicity of a 19 amino acid peptide from foot-and-mouth disease virus has previously been shown to approach that of the inactivated virus from which it was derived after multimeric particulate presentation as an N-terminal fusion with hepatitis B core antigen. In this report we demonstrate that rhinovirus peptide-hepatitis B core antigen fusion proteins are 10-fold more immunogenic than peptide coupled to keyhole limpet hemocyanin and 100-fold more immunogenic than uncoupled peptide with an added helper T-cell epitope. The fusion proteins can be readily administered without adjuvant or with adjuvants acceptable for human and veterinary application and can elicit a response after nasal or oral dosing. The fusion proteins can also act as T-cell-independent antigens. These properties provide further support for their suitability as presentation systems for "foreign" epitopes in the development of vaccines.

Adjuvants, Immunologic↗
PubMed1990

Presentation and immunogenicity of viral epitopes on the surface of hybrid hepatitis B virus core particles produced in bacteria.

We recently reported the enhanced immunogenicity of a peptide epitope when it was presented as a fusion protein with hepatitis B core antigen. In those experiments the fusion protein was expressed in vaccinia virus. We have now refined the system so that large amounts of highly immunogenic particles can be produced using a simple bacterial expression system. We describe the expression of three different viral epitopes as chimeric particles that induce good antibody responses to each epitope after one dose of low amounts of antigen. Finally we demonstrate that the immunogenicity is a reflection of both T helper cell sites within the core protein and also the particulate nature of the immunogens.

Amino Acid Sequence↗
PubMed1990

Neutralizing antibodies to all seven serotypes of foot-and-mouth disease virus elicited by synthetic peptides.

Uncoupled peptides from all seven serotypes of foot-and-mouth disease virus (FMDV) protein VP1 have been used to elicit neutralizing antibody responses in guinea-pigs. The responses were largely serotype specific, although some significant cross-neutralization was observed. Dimeric tandem peptides have also been used to simultaneously elicit neutralizing antibodies to two different FMDV serotypes. The possible existence of structural features common to the B-cell neutralization sites or the guinea-pig helper T-cell sites within all seven peptides are analysed and discussed.

Amino Acid Sequence↗