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Biomedical subjects

R S Tedder

Publications and source records attributed to R S Tedder.

At least 19 recordsLinked to original sources
PubMed1992

A microtitre format point mutation assay: application to the detection of drug resistance in human immunodeficiency virus type-1 infected patients treated with zidovudine.

An assay for the analysis of point mutations in DNA fragments amplified by the polymerase chain reaction is described. The method was applied to the analysis of mutations leading to single amino acid changes in the reverse transcriptase gene of human immunodeficiency virus type-1 that are associated with decreased sensitivity of the virus to the effects of the nucleoside analogue zidovudine. The assay uses a microtitre format allowing large numbers of clinical samples to be analysed, and is a quantitative assay giving information on the relative proportions of wild-type and mutant sequence at the point being analysed. The analysis of mutations in codons 67, 70, 215, and 219 of the RT gene in samples taken at various time points after the commencement of zidovudine therapy shows a high variability in the rate at which these mutations arise and in the proportions of wild-type and mutant sequences observed. The method we describe has wide application to the analysis of other point mutations in clinical or research studies.

Base Sequence↗
PubMed1992

Detection of herpesvirus DNA in the large intestine of patients with ulcerative colitis and Crohn's disease using the nested polymerase chain reaction.

The prevalence of herpesvirus DNA was examined in inflammatory bowel disease tissue. DNA was extracted from resection and biopsy specimens of the large intestine from patients with ulcerative colitis (n = 21), patients with Crohn's disease (n = 29), and patients with noninflammatory bowel disease (controls) (n = 21). The nested polymerase chain reaction was used to detect viral DNA using primer pairs specific for either cytomegalovirus (CMV), herpes simplex virus 1 (HSV1), human herpesvirus 6 (HHV6), varicella zoster virus (VZV), or Epstein Barr virus (EBV). HSV1 and VZV DNA were not detected in any of tissue samples. There was a high prevalence of CMV (81%), HHV6 (76%), and EBV (76%) DNA in ulcerative colitis tissue compared to Crohn's disease tissues (CMV 66%, HHV6 45%, EBV 55%). Control tissue had a relatively low frequency of CMV (29%) and EBV (19%) DNA but a prevalence of HHV6 DNA similar to that of ulcerative colitis (86%). However, the simultaneous presence of HHV6 and CMV and/or EBV DNA in ulcerative colitis tissue (76%) was much greater than in either Crohn's disease tissues (38%) or control tissue (29%) (P < 0.05). There was a low prevalence of CMV, HHV6, and EBV DNA in peripheral blood mononuclear cells from all patient groups. CMV and EBV are capable of reactivating HHV6: the high prevalence of coexistent HHV6 infection with either or both of these two viruses in ulcerative colitis tissue suggests that they may play a synergistic role in the pathogenesis of this disease.

Adolescent↗
PubMed1992

Diagnostic reagents for hepatitis C virus.

The development of diagnostic methods for hepatitis C virus is presented. Special attention is paid to the selection of antigenic markers, the type of assay selected and the interpretation of results. A few of the pitfalls and ambiguities of various assays are discussed and possible future methods are described.

Antigens, Viral↗
PubMed1991

Failure to deliver hepatitis B vaccine: confessions from a genitourinary medicine clinic.

OBJECTIVE: To audit hepatitis B immunisation of homosexual or bisexual men in a genitourinary medicine clinic. DESIGN: Retrospective case note review of all homosexual and bisexual men presenting to a genitourinary clinic as new patients during 12 months in 1988 and follow up review of notes to May 1990. SETTING: One department of genitourinary medicine, Middlesex Hospital. PATIENTS: 758 homosexual or bisexual men, of whom 207 started a course of hepatitis B vaccine in 1988. Case notes were unavailable for one patient. MAIN OUTCOME MEASURES: The proportion of patients screened for hepatitis B virus markers, the proportion of susceptible patients immunised, the proportion completing the vaccine course, and the proportion rendered immune. RESULTS: 25 men had been previously tested for hepatitis markers; of the 732 not previously tested, 440 (60.1%) were screened for hepatitis B markers. 207 (69%) of the 300 patients without hepatitis B serological markers started the vaccine course, and 141 (68%) completed it, with 75 (84%) of the 89 tested after immunisation being immune. An estimated 24% of susceptible new patients were rendered immune as a result of the immunisation policy. Patients who presented with a further episode of a sexually transmitted disease were more likely to have been screened (25% v 12%, p less than 0.0001) and immunised (31% v 18% p = 0.02); those known or found to be positive for HIV antibody were more likely to have been screened (23% v 14%, p = 0.047) but less likely to have been immunised (6% v 17%, p = 0.004). CONCLUSIONS: The major failure was that in not screening; failure to immunise patients found to be susceptible and failure of compliance with the vaccine course contributed. Non-response to the vaccine was of minor importance. Improvements in vaccine delivery are required. IMPLICATIONS: Other providers should be encouraged to review their performance.

Adult↗
PubMed1991

Hepatitis C virus: evidence for sexual transmission.

OBJECTIVE: To determined the prevalence of hepatitis C virus infection and associated risk factors in patients attending a genitourinary medicine clinic, as evidence for sexual transmission. DESIGN: Seroprevalence estimated by reactivity in an enzyme immunoassay for antibodies to C100 protein with supplementary testing with a recombinant immunoblot assay and an assay for hepatitis C virus RNA. SETTING: Outpatient genitourinary medicine clinic in central London. PATIENTS: The panel of 1046 serum samples was from 1074 consecutive patients attending the clinic during November and December 1987 and having blood taken for routine testing for syphilis. Before samples were anonymised demographic and risk factor information was extracted from the clinic notes. Samples had already been tested for antibody to HIV-I and antibody to hepatitis B core antigen. MAIN RESULTS: Significantly more homosexual subjects than heterosexual subjects were positive for hepatitis C antibody determined by enzyme immunoassay alone (19/275 (6.9%) v 8/771 (1.0%), odds ratio 7.14, p less than 0.0001) and also when reactive serum samples were also tested by recombinant immunoblot assay (6/270) (2.2%) v 3/770 (0.4%), odds ratio 5.88, p less than 0.02). There were also significant associations in patients positive for hepatitis C antibody with positivity for antibodies to HIV and to hepatitis B core antigen, lifetime number of sexually transmitted diseases (homosexual men only), and age (all groups combined). Most patients whose serum samples contained specific antibodies to hepatitis C virus were viraemic. CONCLUSIONS: The study provides strong evidence for the sexual transmission of hepatitis C virus. Assays derived from other gene products are desirable to investigate the specificity and sensitivity of the enzyme immunoassay for C100 antibody as a marker of hepatitis C virus infection.

Adolescent↗
PubMed1991

Effect of alpha-interferon therapy on hepatitis C viraemia in community-acquired chronic non-A, non-B hepatitis: a quantitative polymerase chain reaction study.

Sera from 30 patients with community-acquired, biopsy-proven chronic non-a,non-B hepatitis (NANBH) were tested for antibodies to the C100 protein of hepatitis C virus (HCV). The 20 patients who showed reactivity in this assay were followed prospectively for 6 months, during which time seven were treated with recombinant alpha-interferon. HCV RNA was detected by "nested" polymerase chain reaction (PCR) in 19 of the 20 anti-C100-positive sera taken at the onset of the study and also in five of the ten anti-C100-negative sera. Pretreatment viraemia levels ranged from 2 x 10(3) to 2 x 10(8) HCV genomes/ml. After 6 months of interferon, elevated serum alanine aminotransferase (ALT) levels had fallen to normal in four of the seven treated patients. In each case the response to interferon was accompanied by either a disappearance of or a decline (1 log to 8 log reduction) in viraemia. HCV genome titres in the three nonresponders and in the 13 untreated anti-C100-positive patients did not change significantly over this 6 month period. These findings confirm the aetiological role of HCV in community-acquired NANBH and suggest that quantitative PCR will become a valuable technique for monitoring the antiviral effect of interferon and other experimental treatments.

Adult↗
PubMed1991

Hepatitis C viraemia in adults with type 2 autoimmune hepatitis.

Sera from 14 patients with type 2 autoimmune hepatitis (anti-LKM1 positive) were investigated for evidence of hepatitis C virus (HCV) infection. Antibodies to HCV were detected in 13 patients by both commercial and "in-house" ELISAs and also by a second generation recombinant immunoblot assay. Nine of the 13 (69%) anti-HCV positive patients were shown to be viraemic by a polymerase chain reaction-based assay for serum HCV RNA. Neither anti-HCV nor serum HCV RNA were detected in any of 6 controls with primary biliary cirrhosis or in 39 healthy blood donors. These findings strongly suggest a role for HCV in the pathogenesis of type 2 autoimmune hepatitis.

Adolescent↗
PubMed1991

A comparison of four enzyme immunoassays for the simultaneous detection of HIV-1- and HIV-2-specific antibody.

The performance of four HIV 1 and 2 combined assays has been compared with current type-specific assays using three panels of sera. The first panel comprised single samples from 19 HIV-1-infected persons; the second panel comprised 19 sera from 16 HIV-2-infected persons. Samples from both these panels were titrated across interpolated end points of detectability. The third panel comprised sera from 5200 consecutive blood donors. The four combined assays, manufactured by Abbott Laboratories, Behring Laboratories, Diagnostics Pasteur and Wellcome Diagnostics Laboratories detected all anti-HIV-1 sera at high dilution; the immunometric assay from Wellcome was particularly proficient. All assays were broadly similar in their ability to detect sera from recently infected persons. The same assays were also effective in detecting anti-HIV 2 in sera both from seropositive individuals and from a single recently-infected person, though none was as sensitive as an inhouse competitive EIA. When used for donor screening the repeat reactive rates for donors negative for HIV 1 and 2 antibodies ranged between 1.80% for Elavia Mixt from Pasteur, 0.27% Abbott combined and 0.15% for the Wellcome combined assays.

Antibodies, Viral↗
PubMed1991

Monoclonal antibodies define linear and conformational epitopes of HIV-1 pol gene products.

Purified recombinant reverse transcriptase (RT) from human immunodeficiency virus type 1 (HIV-1) was used to raise 21 monoclonal antibodies with anti-RT specificities. The antibodies were characterized using Western blotting against native virus and recognized either the p66 or p66, p51 components of RT. Further immunoblotting using either cyanogen bromide fragmented RT or truncated mutants of RT along with cross-competition studies enabled the location of various immunogenic regions of RT to be identified. Three antibodies recognized a linear epitope in the N-terminal region (amino acids 128-176). Also, a neutralizing RT antibody recognized a conformational epitope in this region. Three monoclonals had epitopes mapped to linear sequences in the RNase H region at the C-terminus of the RT. Another neutralizing antibody, also requiring folding of the RT protein had its epitope more centrally located (231-353). Of the remaining 13 monoclonals, 7 were roughly located in the C-terminal region and required folding of the protein for epitope recognition and only three of the remaining six could be mapped to conformational epitopes in N-terminal and central regions of the RT. None of the antibodies tested recognized HIV-2 RT products p68 and p55 in Western blot.

Animals↗
PubMed1991

Expression of HIV-1 in the cerebrospinal fluid detected by the polymerase chain reaction and its correlation with central nervous system disease.

The polymerase chain reaction (PCR) was used to detect HIV-1 sequences (gag, pol, and env) in the cerebrospinal fluid (CSF) and serum samples from 53 HIV-1-positive patients and the results correlated with clinical evidence of neurological disease. Twenty-three out of 24 patients with neurological disease had HIV-1-specific sequences in CSF compared with four out of 20 asymptomatic patients who had no evidence of neurological involvement. The detection of HIV RNA sequences by PCR in the CSF of HIV-positive patients may provide early, rapid and direct evidence of neurological involvement in asymptomatic subjects.

Adult↗
PubMed1991

Hepatitis C antibody profile and viraemia prevalence in adults with severe haemophilia.

Sera from 21 patients who had received large amounts of unheated factor VIII concentrate were tested for antibodies to the hepatitis C virus (HCV) by both commercial (Ortho C100) and 'in house' ELISAs. 'In house' assays utilized recombinant structural (core) or non-structural (replicase) HCV proteins generated by a baculovirus expression system. Antibodies to HCV were detected in 100% of the sera by the core protein based ELISA but in only 62% and 19% by the C100 and replicase based ELISAs, respectively. Hepatitis C viraemia was demonstrated in 90% of the patients by in vitro amplification of the 5' non-coding region of the HCV genome. Amplification with primer sets from two other regions of the genome proved less efficient at detecting viraemia. We conclude that the prevalence of hepatitis C infection in haemophiliacs may have been underestimated previously and that almost all HCV-infected patients have evidence of on-going viral replication.

Adult↗
PubMed1990

Demonstration of viraemia patterns in haemophiliacs treated with hepatitis-C-virus-contaminated factor VIII concentrates.

Sequential serum samples from previously untreated haemophiliacs in whom non-A, non-B hepatitis (NANBH) developed after they received factor VIII concentrate contaminated with hepatitis C virus (HCV) were tested by a commercial assay for the presence of antibodies to the C100 protein of HCV (anti-C100) and by "nested" PCR for the presence of HCV RNA sequences. Three temporal patterns of viraemia were observed: transient viraemia in acute resolving NANBH; viraemia lasting for several years in chronic NANBH; and intermittent viraemia in chronic NANBH, with an initial transient phase followed by recurrence after many months. In three of five cases the initial detection of serum HCV RNA was made before the onset of liver function test abnormality, many weeks or months before anti-C100 seroconversion. Diagnosis of acute HCV infection may therefore be possible much earlier by PCR than by existing serological techniques, but the timing of samples may be critical.

Acute Disease↗
PubMed1990

Adult T-cell leukaemia/lymphoma in Brazil and its relation to HTLV-I.

In a series of fourteen patients with adult T-cell lymphoma-leukaemia (ATLL) in Brazil the main features were lymphadenopathy, hepatosplenomegaly, hypercalcaemia, and high leucocyte counts, with abnormal lymphoid cells which had irregular nuclei. The series included the youngest patient with ATLL so far (18 months). Analysis with monoclonal antibodies showed a mature T-cell phenotype (CD4+, CD8-). Antibodies to HTLV-I and/or integration of HTLV-I proviral DNA were found in eleven patients. In the other three HTLV-I DNA could not be demonstrated even by means of the polymerase chain reaction; they therefore had HTLV-I-negative ATLL. This report of ATLL in Brazil corroborates serological reports that HTLV-I may be endemic in some parts of that country. Follow-up studies are required to identify precisely the main route of transmission of HTLV-I in South America and the risk factors for the development of ATLL in carriers.

Adult↗