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Biomedical subjects

C J Burrell

Publications and source records attributed to C J Burrell.

At least 37 records · Page 2Linked to original sources
PubMed1998

Protective efficacy of DNA vaccines against duck hepatitis B virus infection.

The efficacy of DNA vaccines encoding the duck hepatitis B virus (DHBV) pre-S/S and S proteins were tested in Pekin ducks. Plasmid pcDNA I/Amp DNA containing the DHBV pre-S/S or S genes was injected intramuscularly three times, at 3-week intervals. All pre-S/S and S-vaccinated ducks developed total anti-DHBs and specific anti-S antibodies with similar titers reaching 1/10,000 to 1/50,000 and 1/2,500 to 1/4,000, respectively, after the third vaccination. However, following virus challenge, significant differences in the rate of virus removal from the bloodstream and the presence of virus replication in the liver were found between the groups. In three of four S-vaccinated ducks, 90% of the inoculum was removed between <5 and 15 min postchallenge (p.c.) and no virus replication was detected in the liver at 4 days p.c. In contrast, in all four pre-S/S-vaccinated ducks, 90% of the inoculum was removed between 60 and 90 min p.c. and DHBsAg was detected in 10 to 40% of hepatocytes. Anti-S serum abolished virus infectivity when preincubated with DHBV before inoculation into 1-day-old ducklings and primary duck hepatocyte cultures, while anti-pre-S/S serum showed very limited capacity to neutralize virus infectivity in these two systems. Thus, although both DNA vaccines induced high titers of anti-DHBs antibodies, anti-S antibodies induced by the S-DNA construct were highly effective in neutralizing virus infectivity while similar levels of anti-S induced by the pre-S/S-DNA construct conferred only very limited protection. This phenomenon requires further clarification, particularly in light of the development of newer HBV vaccines containing pre-S proteins and a possible discrepancy between anti-HBs titers and protective efficacy.

Animals↗
PubMed1998

Anomalous origin of the left coronary artery from the pulmonary artery: natural history and normal pregnancies.

Two female patients are described with anomalous origin of the left coronary artery arising from the pulmonary artery who sustained an anterolateral myocardial infarction in infancy. Neither patient received surgical treatment although both have lived to middle age with minimal cardiovascular problems and have had uncomplicated pregnancies. Good exercise tolerance and long term survival may be possible even without surgery for patients with this anomaly.

Adult↗
PubMed1997

AZT blocks down-regulation of IL-2 and IFN-gamma gene expression in HIV acutely infected cells.

HIV infection causes dysregulation of cytokine gene expression in CD4+ T cells of the infected host. Azidothymidine (AZT) inhibits HIV replication by blocking reverse transcription. Using a one-stop cell-to-cell HIV infection model, we have investigated the expression of several key cytokines in HIV infected T cells in the absence or presence of AZT treatment. Acute HIV infection of T cells resulted in dramatic down regulation of the expression of IL-2 and INF-gamma mRNA. While beta-actin mRNA levels remained constant in both AZT-free and AZT treated cultures after HIV infection, it was found that AZT blocked the down regulation of IL-2 mRNA and INF-gamma mRNA in CD4+ T cells acutely infected with HIV.

CD4-Positive T-Lymphocytes↗
PubMed1997

Successful external cardioversion for ventricular tachycardia using 2 Joules.

We present a patient with recurrent sustained monomorphic ventricular tachycardia following myocardial infarction, refractory to drug therapy. He has been reluctant to have an implantable cardioverter-defibrillator, but responds to very low energy transthoracic direct current cardioversion administered via external pacing electrodes under sedation. The use of very low energies may avoid shock-induced myocardial damage in patients with recurrent ventricular tachycardia.

Bundle-Branch Block↗
PubMed1997

Enhancement or inhibition of HIV-1 replication by intracellular expression of sense or antisense RNA targeted at different intermediates of reverse transcription.

OBJECTIVES: To construct retroviral vectors expressing sense or antisense RNA targeted at HIV reverse transcription intermediates, and to test the anti-HIV properties of these constructs in transduced T cells. DESIGN: Five double-copy retroviral vectors were constructed, in which the expression of the sense or antisense RNA corresponding to HIV minus- or plus-strand strong-stop DNA was driven by the human tRNA(met) promoter. METHOD: The templates for the sense or antisense RNA were polymerase chain reaction-cloned from HIV pNL43 into a murine leukaemia virus-based vector and corresponding defective virions were packaged in PA317 cells. Human Jurkat T cells transduced with these vectors were challenged with HIV and monitored for viral RNA, viral DNA and p24 production for 23 weeks. RESULTS: Intracellular expression of HIV sense RU5 sequences (RNA complementary to minus-strand strong-stop DNA) enhanced HIV replication in T cells. Expression of HIV sense or antisense U3RU5 sequences (identical or complementary to plus-strand strong-stop DNA) conferred long-term inhibition of HIV replication, despite continuous presence of viral challenge in the transduced cell cultures. CONCLUSION: Plus-strand strong-stop DNA as an intermediate in the early process of viral reverse transcription can be explored as an additional target for anti-HIV gene therapy.

Cell Line↗
PubMed1997

Kinetics of viral RNA synthesis following cell-to-cell transmission of human immunodeficiency virus type 1.

The temporal appearance and levels of human immunodeficiency virus type 1 (HIV-1) tat, rev, nef, env and gag mRNA species were examined using a synchronized, one-step, cell-to-cell HIV-1 infection model involving HUT-78 cells and HIV- 1 persistently infected H3B cells. Individual mRNAs were quantified by RT-PCR using RNA standards transcribed in vitro from cDNA clones. Consistent with an infection that produces high yields of virus, significant levels of env and gag mRNAs were detected in the cytoplasm of infected cells late in the infection cycle. However, at no time after infection did levels of tat, rev and nef mRNA, which encode the regulatory proteins of HIV-1, exceed their levels present in the persistently infected virus donor H3B cells. The absence of early phase induction of these mRNAs is in contrast to what is observed in cell-free HIV-1 infections or in PMA-stimulated HIV-1 chronically infected cell lines. Our results suggest that tat and rev mRNAs are already present in the cytoplasm of the persistently infected virus donor cells at levels sufficient for initiation and establishment of a highly productive infection in HIV-1 fusion-mediated infected cells. Thus, lack of sufficient Tat and Rev proteins is not likely to be the limiting factor for virus production in H3B cells, nor is increased production of these proteins likely to be the cause of the increased virus production seen following cell-to-cell transmission.

Cell Line↗
PubMed1996

Kinetics of duck hepatitis B virus infection following low dose virus inoculation: one virus DNA genome is infectious in neonatal ducks.

Using pooled serum from congenitally duck hepatitis B virus (DHBV)-infected ducks as inoculum, we examined the effect of virus dose on the incubation period of infection and on the patterns of spread of virus infection in the liver. The pooled serum inoculum contained 9.5 x 10(9) DHBV genomes per milliliter and had an infectivity titre (ID50) in newly hatched ducks of 1.5 x 10(10) per milliliter with a 95% confidence interval of 3.0 x 10(9) to 6.3 x 10(10) ID50/ml, indicating the equivalence between one DHBV genome and one infectious unit within the limits of the assays. The incubation period of infection was inversely related to the dose of inoculum and the onset of viraemia ranged from Day 6 with the highest dose to Day 14 or 29 with the lowest dose inoculum. To study the spread of virus infection from a low percentage of initially infected cells we inoculated newly hatched ducks intravenously with sufficient DHBV (1.5 x 10(3) ID50) to infect only approximately 0.0001% of total liver cells. DHBV infection first reached detectable levels on Day 4 postinoculation (p.i.) and was detected in approximately 0.035% of hepatocytes, most of which occurred as single cells or pairs of cells, indicating that a number of rounds of infection had occurred with the spread of virus both to adjoining cells, i.e., by cell-to-cell spread, and to cells located in other parts of the liver lobule. Despite some bird-to-bird variation in timing, the percentage of infected hepatocytes increased exponentially with a mean doubling time of 16 hr from Day 4 to Day 14 p.i., by which time replication was seen in > 95% of hepatocytes. This rapid dissemination from a small number of infected hepatocytes suggests that, in neonatal ducks, there are no major delays in virus replication within the liver, that any innate and adaptive defence mechanisms operating during the first 10 to 14 days of infection are insufficient to contain virus spread, and that even a small number of infected hepatocytes produce enough progeny to rapidly infect the remaining hepatocytes.

Age Factors↗
PubMed1995

Lack of evidence for significant hepatitis B transmission in Australian Rules footballers.

OBJECTIVE: To determine the prevalence of markers of past hepatitis B infection among participants in Australian Rules football, to estimate the potential exposure of Australians to hepatitis B virus (HBV) in contact sport. DESIGN AND SETTING: A point prevalence survey for antibody to hepatitis B surface antigen (anti-HBs) and core antigen (anti-HBc), supported by a questionnaire used to determine the history of risk and exposure, in South Australian National Football League (SANFL) players supervised at club level by general practitioners and sports medicine specialists. PARTICIPANTS: Of 245 players from seven clubs, 49 were excluded from the study because they had been previously vaccinated. Of 196 eligible participants, 117 submitted blood samples and, of these, 85 returned questionnaires. RESULTS: One player was positive for anti-HBc (a prevalence rate of 0.85%). This individual and three anti-HBc-negative players were positive for anti-HBs in the absence of a history of vaccination. We could not ascertain whether these additional three players had been previously infected, or vaccinated without this fact having been recorded on the questionnaires. No single behavioural factor correlated with positive anti-HBs results. CONCLUSIONS: The prevalence of markers of past hepatitis B infection in SANFL football players was no different to that in blood donors of the same age group from the same city. There was no evidence for any additional HBV transmission due to participation in football over that in the blood donor population. Vaccination of footballers and people engaged in similar sports is of benefit in conferring protection on the individual, but would be unlikely to make a significant public health impact on community rates of HBV infection.

Adolescent↗
PubMed1995

Stepwise analysis of reverse transcription in a cell-to-cell human immunodeficiency virus infection model: kinetics and implications.

We have investigated the kinetics of human immunodeficiency virus (HIV) reverse transcription in infected T cells, using a synchronized, one-step, cell-to-cell infection model and quantitative PCR assays for the different DNA intermediate structures that are found sequentially during reverse transcription. Different efficiencies that might arise from the use of different primers and other PCR conditions were normalized by conversion of each PCR product signal to copy numbers by comparing with standards. After an initial lag period, the minus-strand strong-stop viral DNA was detected first. This was followed by the post-transfer newly extended minus-strand viral DNA and then by the plus-strand strong-stop DNA and fully extended minus-strand DNA. Kinetic data indicated that, once reverse transcription was initiated, the HIV reverse transcriptase synthesized minus-strand DNA at a rate of 150-180 bases/min, and that the first template transfer and the initiation of the plus-strand DNA synthesis imposed specific time delays. In contrast, minus-strand viral DNA synthesized after the second template transfer appeared at a time point very close to the time of the appearance of the last piece of DNA synthesized just before the second template switch, suggesting that the second switch occurred very rapidly. Taken together, our results define more accurately than was previously possible the rates of several of the steps in HIV reverse transcription in infected T cell lines and indicate different mechanisms for the two distinct template switches during retrovirus reverse transcription.

Cell Communication↗
PubMed1994

Routine diagnosis of seven respiratory viruses and Mycoplasma pneumoniae by enzyme immunoassay.

A composite EIA, using 8-well microstrips, was used for the rapid detection of seven respiratory viruses and M. pneumoniae. The viruses included influenza A and B, parainfluenza 1, 2 and 3, adenovirus and respiratory syncytial virus. During the 61 month period--June 1988 to June 1993--17326 respiratory specimens, submitted from three states, were tested by this EIA. The specimens were mainly from a paediatric population (hospitals and private physicians). RSV was the predominant virus detected, followed by adenovirus, parainfluenza 3, M. pneumoniae, influenza A, parainfluenza 2, influenza B and parainfluenza 1. The use of blocking antibodies confirmed the identification of the agents, in particular with samples showing absorbance values greater than the cutoff with more than one infectious agent. Different methods for processing specimens in order to obtain a uniform suspension, and interpretation of non-specific reactions, are discussed. The assays showed an average sensitivity of 85% and specificity of 99%, compared to virus culture. This EIA system provided an efficient method for the rapid diagnosis of viral and mycoplasmal infections in a busy diagnostic laboratory.

Humans↗
PubMed1994

Initiation of reverse transcription during cell-to-cell transmission of human immunodeficiency virus infection uses pre-existing reverse transcriptase.

H3B cells, a laboratory clone of H9 cells persistently infected with the HTLV-IIIB strain of human immunodeficiency virus (HIV), contained significant levels of cell-associated reverse transcriptase (RT) activity measured by in vitro assays using either exogenous or endogenous templates. The cell-associated RT activity detected using exogenous template was almost wholly in a soluble (non-sedimentable) form whereas endogenous activity sedimented as a particulate structure associated with viral RNA. Despite this, H3B cells did not contain episomal HIV DNA detectable by Southern blot, indicating that in vivo reverse transcription was not occurring to any significant extent in these cells. However, when susceptible HUT 78 cells were infected by co-cultivation with H3B cells, dramatic synthesis of episomal HIV DNA occurred. Concurrently with this de novo initiation of reverse transcription, however, we found no detectable change in intracellular levels or cleavage profiles of immunoprecipitable RT polypeptides. Finally, actinomycin D pre-treatment of H3B cells to prevent de novo transcription from donor cell proviral DNA after co-cultivation did not affect the initiation of in vivo reverse transcription following cell-to-cell HIV infection. These results demonstrated that cells persistently infected with HIV contained significant fully cleaved cell-associated RT in a form that was active in vitro but not in vivo and that following cell-to-cell transmission of HIV infection to susceptible cells, de novo reverse transcription was initiated without detectable evidence of further synthesis or proteolytic processing of HIV RT. The nature of this initiation process requires further study.

Biological Transport↗
PubMed1993

Double-stranded strong-stop DNA and the second template switch in human immunodeficiency virus (HIV) DNA synthesis.

Synthesis of unintegrated retroviral DNA via reverse transcription is thought to involve two separate template switches. Minus-strand strong-stop DNA, a major product of in vitro reactions using detergent-treated virions, is synthesized prior to the first template switch. Plus-strand strong-stop DNA, which is found base-paired to near full-length minus-strand DNA in infected cells, is believed to be synthesized before the second template switch. Using a synchronized, one-step HIV infection model, we report here the detection in acutely infected cells of a novel double-stranded strong-stop HIV DNA with a discrete length of approximately 650 base pairs, commencing at or near the left hand end of the right-hand U3 region of the HIV long terminal repeat. The plus-strand of this double-stranded strong-stop DNA possesses the primer binding site sequence and appears to be synthesized prior to the completion of the synthesis of its complementary minus-strand. In contrast, the minus-strand of the double-stranded strong-stop DNA lacks the primer binding site sequence after RNaseH digestion. We propose that a transient free plus-strand strong-stop DNA is released from its template by displacement synthesis and subsequently used as template for the synthesis of its complementary minus-strand. The proposed transient free plus-strand strong-stop DNA may also mediate the second template switch.

Base Sequence↗
PubMed1992

High prevalence of human papillomavirus transcripts in all grades of cervical intraepithelial glandular neoplasia.

Cervical biopsy specimens containing cervical intraepithelial glandular neoplasia (CIGN) were examined for the presence of human papillomavirus (HPV) RNA transcripts by in situ hybridization with iodine 125-labeled riboprobes. HPV RNA was detectable in 95.2% of biopsy specimens. HPV 16 RNA was present in 12, HPV 18 in 27, and both in 1 of the 42 cases examined. Among HPV-positive cases, HPV RNA was detectable in all grades of CIGN and, in three cases, in glands displaying only minimal nuclear abnormality insufficient for a diagnosis of CIGN. Patients with HPV RNA-positive CIGN were younger than those with negative findings for HPV, and patients with less severe grades of CIGN showed a trend toward a younger age of presentation than patients with severe glandular lesions. Increasing grades of CIGN may reflect progressive stages in the development of cervical adenocarcinoma, and this progression may closely involve HPV gene expression from its earliest stages.

Adult↗
PubMed1992

Hepatitis B virus markers in children and staff in Northern Territory schools.

OBJECTIVE: To measure the prevalence of hepatitis B virus (HBV) infection in children and staff at Northern Territory schools. DESIGN: Children in Years 5-7 in 24 selected primary schools were invited, with parental consent, to provide demographic and ethnic details, and a capillary blood sample for tests for hepatitis B surface antigen (HBsAg) and antibody to hepatitis B surface antigen (anti-HBs). School staff participated on a similar basis. PARTICIPANTS: 1104 children, comprising 556 from ethnic groups (originating from the United Kingdom, Ireland and northern Europe) previously reported as "low HBV prevalence", 439 Aboriginal Australians, and 109 from "other" ethnic groups (originating from Asia, the Pacific, the Middle East and southern Europe); and 209 school staff, comprising 180 from "low HBV prevalence" ethnic groups, and 29 from Aboriginal and other ethnic groups. RESULTS: Prior HBV infection (i.e. serum positive for HBsAg or anti-HBs) was detected in 28.7% of children (46.9% of 439 Aborigines; 13.7% of the 556 children from the "low prevalence" groups and 32.1% of the 109 from the "other" groups). HBsAg was detected in 8.2% of Aboriginal children, in 0.36% of those from "low prevalence" groups, and in 1.8% of those from the "other" groups. Aboriginal children in rural schools had the highest prevalence of HBV: 5.4% were positive for both HBsAg and anti-HBs, and an additional 9.8% were positive for HBsAg alone. In urban schools, the prevalence was highest in the "other" ethnic groups. For school staff, the prevalence of HBV infection was 12.8% for those from "low prevalence" ethnic groups, and 37.9% for those from all remaining groups (including Aborigines). CONCLUSION: In the Northern Territory the prevalence of past HBV infection is high in children and school staff from ethnic groups previously known to be at higher risk of HBV infection. For students and staff from ethnic backgrounds expected to be at low risk, HBV prevalence is greater than in individuals from similar backgrounds in other parts of Australia. HBV vaccination is now offered to all infants in the Northern Territory. These results also provide a rationale for the more widespread use of HBV vaccine in other situations where significant HBV transmission might occur.

Child↗
PubMed1992

Intracellular factors, but not virus receptor levels, influence the age-related outcome of DHBV infection of ducks.

Previous serological studies of experimental infection with duck hepatitis B virus (DHBV) have shown that the outcome of infection depends largely on the age of the duck at the time of inoculation. To examine the hypothesis that decreased susceptibility with increased age might be due to the loss of the virus receptor on hepatocyte membranes in adult ducks, we performed receptor binding studies using intact serum-derived DHBV virions and purified liver plasma membranes from both young ducklings and adult ducks. These studies showed that (1) DHBV was able to bind specifically to duck liver plasma membranes but not to internal membranes; (2) this binding could be inhibited by a monoclonal antibody to DHBV preS, a corresponding region in hepatitis B virus that binds to human hepatocytes; and (3) there was no significant difference in the receptor binding ability between plasma membranes from ducklings and from adult ducks. Since hepatocytes in the neonatal ducks are actively dividing, in contrast to the situation in adult ducks, we examined the effect of partial hepatectomy on DHBV-carrier ducks. A sharp increase was noted in the level of DHBV in the serum after partial hepatectomy suggesting that DHBV replication was enhanced in dividing hepatocytes. Thus the age-related difference in susceptibility of ducks to DHBV infection is not due to loss of the receptor but may be related to an intracellular event associated with cell division.

Aging↗