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Biomedical subjects

S F Lyons

Publications and source records attributed to S F Lyons.

At least 19 recordsLinked to original sources
PubMed1999

Restriction fragment length polymorphism analysis for rapid gag subtype determination of human immunodeficiency virus type 1 in South Africa.

A rapid method for identification of human immunodeficiency virus Type 1 (HIV-1) gag subtypes was developed based on restriction fragment length polymorphism (RFLP) analysis of 400 or 650 bp long polymerase chain reaction (PCR) fragments encompassing the start of the p17 (400 bp) and part of the p24 (650bp) regions. The consensus sequences of subtypes A-D, the only subtypes identified in South Africa, were analyzed to detect restriction endonucleases which generate unique patterns for each subtype. Four restriction endonucleases were identified: AluI, AccI, SwaI and XmnI. Digestion of a 400 bp fragment with AluI allowed identification of subtype C. Samples not identified were then reamplified, and a 650 bp fragment digested with AccI to identify subtype B, followed by SwaI and XmnI to distinguish between subtypes A and D. This strategy was applied to 87 samples previously subtyped by either sequence analysis of the gag p17 region (n = 33); or heteroduplex mobility assay (HMA) based on the env gene (n = 75); or both (n = 21). Out of the 87 samples, RFLP identified two samples as subtype A, 28 as subtype B, 56 as subtype C and one as a subtype D virus. No discrepancies were found between RFLP gag subtypes and gag sequence subtypes demonstrating the reliability of this method. There was also no discordance between gag RFLP subtypes and env HMA subtypes, suggesting that there were no recombinant viruses detected relating to the genomic regions analyzed. RFLP is an effective technique for the rapid screening in an HIV epidemic of limited diversity, such as in South Africa.

DNA, Viral↗
PubMed1998

High human immunodeficiency virus type 1 RNA load in the cerebrospinal fluid from patients with lymphocytic meningitis.

Thirty-seven matched cerebrospinal fluid (CSF) and plasma samples from 34 human immunodeficiency virus type 1 (HIV-1)-infected patients with suspected meningitis were analyzed for levels of HIV-1 RNA and markers of inflammation. Patients with tuberculous (n = 9) or cryptococcal (n = 6) meningitis had the highest CSF virus loads, which in many cases exceeded the levels in plasma, compared with patients with meningococcal meningitis (n = 3), aseptic meningitis (n = 8), tuberculoma (n = 2), or AIDS dementia complex (n = 4) or with normal lumbar punctures (n = 3). CSF virus load correlated significantly with the number of infiltrating lymphocytes (r = .60, P < .001) but not with plasma virus load, the levels of beta2-microglobulin in the CSF, or the integrity of the blood-brain barrier. These data suggest significant intrathecal HIV-1 replication in patients with lymphocytic meningeal infections such as tuberculous and cryptococcal meningitis.

AIDS Dementia Complex↗
PubMed1998

The roles of human viruses in the pathogenesis of lymphoma.

There are two families of viruses that contribute to lymphomagenesis in humans: herpesviruses and retroviruses. The two herpesviruses are the Epstein-Barr virus (EBV) and human herpesvirus-8 (HHV-8). EBV is an extremely well-characterized transforming agent: nine viral proteins contribute to transformation in vitro. In contrast, in vivo, the pattern of EBV gene expression varies with different types of malignancies. EBV is associated with endemic Burkitt's lymphoma, acquired immune deficiency syndrome (AIDS)-related lymphoma, post-transplantation lymphoproliferative disease, Hodgkin's disease (HD), and rare T-cell lymphomas. We have summarized studies on the different patterns of viral gene expression and signaling in different EBV-related malignancies, which have begun to reveal how EBV variably contributes to the malignant phenotype in different diseases. HHV-8 is associated with primary effusion lymphomas in patients with AIDS, and the rapidly accumulating information on this virus is summarized. Human T-cell leukemia virus-1 (HTLV-1) is a retrovirus which is the causative agent of adult T-cell leukemia/lymphoma (ATL). The specific mechanism of HTLV-1-mediated T-cell transformation is unclear, but the effects of HTLV-1 on interleukin-2 signaling are reviewed.

Herpesvirus 4, Human↗
PubMed1997

Evaluation of the MUREX*ICE HIV-1.O.2 capture enzyme immunoassay for early identification of HIV-1 seroreverting infants in a developing country.

BACKGROUND: A simple, inexpensive serological assay is required for the early determination of HIV infection status among infants born to HIV-1-seropositive women in developing countries. OBJECTIVES: To evaluate the use of a commercially available capture enzyme immunoassay (EIA), the MUREX*ICE HIV-1.O.2, for the early identification of seroreverting, uninfected infants. STUDY DESIGN: Infants with a clearly defined HIV-1 infection status, as determined by polymerase chain reaction results and/or seroreactivity at 18 months, were tested for antibodies to HIV. The time to seroreversion using the capture EIA was compared with the results obtained using an indirect assay, the GENELAVIA MIXT EIA. RESULTS: Seroreverting infants were identified earlier with the capture than the indirect EIA; all of the uninfected infants were seronegative at 12 months with the capture EIA while 100% seroreversion was only seen at 18 months with the indirect EIA. CONCLUSIONS: In general, the capture EIA identified seroreverting infants 3-6 months earlier than the indirect EIA. However, caution must be exercised in interpreting seroreactivity in a breast-fed population where HIV infection may occur in a child who has previously seroreverted.

Africa↗
PubMed1996

The use of cultured Schwann cells in nerve repair in a rabbit hind-limb model.

A 3-cm peripheral nerve gap in a rabbit hind-limb model was repaired by using a polyglycolic acid (PGA) conduit filled with a gelatin/Schwann-cell suspension. Postoperative nerve function after 16 weeks, as measured by isometric twitch and tetanic muscle strengths, and nerve conduction velocities, failed to demonstrate a statistically significant difference, compared to a control group in which the nerve gap was reconstructed by using a PGA conduit filled with gelatin only. The 3-cm gap in the described model may not have been long enough to show a significant difference between the two groups. Alternatively, the transferred cultured Schwann cells may have been functionally inactive.

Animals↗
PubMed1996

Hyperbaric oxygen and cyclosporine as a combined treatment regimen to prevent skin allograft rejection in immunohistoincompatible mice.

Several previous studies reported various immunosuppressive effects of hyperbaric oxygen on nonspecific and specific cell-mediated reactions. A highly immunogenic skin allograft mouse model was used to evaluate the clinical relevance of the previously described immunosuppressive effects of hyperbaric oxygen. A 1.5 x 2.0-cm full-thickness skin allograft was cross-grafted between paired immunohistoincompatible mouse strains (N = 40, C57BL/6 and BALB/c female mice) that were randomly assigned to four groups receiving (1) no treatment (controls), (2) cyclosporine 1 mg per kilogram intraperitoneally daily, (3) cyclosporine plus a low-dose hyperbaric oxygen treatment (two treatments per day, once a week), and (4) cyclosporine plus a high-dose hyperbaric oxygen treatment (two treatments per day, three times a week) following surgery (N = 32). Allograft samples were taken from each group at day 9 after cross-grafting (N = 8). Skin allograft rejection was significantly delayed in all treatment groups compared to controls. No difference was found between animals who received cyclosporine only and the combined treatment regimen including low-dose hyperbaric oxygen. High-dose hyperbaric oxygen treatment in combination with cyclosporine substantially prolonged skin allograft survival compared to other treatments. These findings were histologically confirmed. We conclude that hyperbaric oxygen treatment as an adjunct to standard immunosuppressive therapy may only be advantageous if frequently applied.

Animals↗
PubMed1996

Identification of cell subsets expressing intracytoplasmic cytokines within HIV-1-infected lymph nodes.

OBJECTIVE: To describe the endogenous cytokine profile of HIV-1-infected lymph nodes (LN) and to identify the phenotype of individual cells expressing intracytoplasmic cytokines. DESIGN AND METHODS: Whole LN biopsies were collected from three HIV-seronegative controls and four HIV-1-positive individuals with persistent generalized lymphadenopathy. Three had established infection (Centers for Disease Control and Prevention 1993 criteria, stages A2, C1 and C3) and one was undergoing seroconversion illness. A combination of three methods was used to assess the impact of HIV-1 on LN architecture and endogenous cytokine expression. Immunocytochemistry was used to locate follicular dendritic cells (FDC), interdigitating cells and T and B cells. Reverse transcriptase-polymerase chain reaction was used to assess mRNA for interleukin (IL)-1 beta, IL-2, IL-4, IL-6, IL-10, tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma in collagenase-digested LN cells. Three-colour flow cytometry was used to identify intracytoplasmic cytokine expression within cell subsets. RESULTS: Germinal center (GC) hyperplasia was observed in LN from two patients with established HIV-1 infection, and the third, coinfected with Mycobacterium tuberculosis, showed extensive necrosis. In the patient undergoing seroconversion, there was an extensive FDC network within the expanded and confluent GC which covered expansive areas of the LN. There was varied expression of IL-1 beta, IL-4, IL-6, IL-10 and TNF-alpha mRNA from the four HIV-1-infected LN and the patient undergoing seroconversion showed evidence for a mixed cytokine profile, which also included IL-2 and IFN-gamma. Flow cytometry revealed intracytoplasmic IL-1 beta protein restricted to cells expressing CD19, CD21 and CD38 antigens. CONCLUSIONS: Cytokines were detected in freshly isolated HIV-1-infected LN cells without requiring an exogenous stimulus. Seroconversion was associated with an expanded FDC network within enlarged GC, bounded by defined mantle zones containing B cells. There was diverse cytokine mRNA expression and IL-1 beta protein was restricted to cells expressing B-cell-associated antigens.

Adult↗
PubMed1995

Skin allograft rejection and hyperbaric oxygen treatment in immune-histoincompatible mice.

The effect of hyperbaric oxygen (HBO) as an immunosuppressive agent was evaluated by using a highly immunogenic skin allograft mouse model. Immune-histoincompatible female C57BL/6 and BALB/c mice (N = 30) were randomly assigned to three groups receiving no treatment (control group), low dose HBO treatment (two treatments once a week), and intermediate HBO treatment (two treatments 3 times/wk) 1 wk before and 2 wk after transplantation of a 1.5 x 2 cm full thickness skin allograft from the back. Rejection was observed a Day 7 and was completed 14 days after surgery in controls. Low dose and intermediate HBO treatment delayed skin allograft rejection, which was histologically confirmed.

Animals↗
PubMed1993

Evaluation of rapid enzyme immunobinding assays for the detection of antibodies to HIV-1.

Three rapid enzyme immunobinding assays, Abbott's TestPack HIV-1/HIV-2, Clonatec's Rapid HIV1/HIV2 AB and the DuPont HIVCHEK 1 + 2, were evaluated using a panel of 20 selected sera with Western blot-proven reactivity to at least one envelope glycoprotein of HIV-1. The Abbott assay had the highest sensitivity and detected 18 of the 20 sera with no indeterminates (i.e. specimens with high background coloration which interferes with interpretation of the assay). Both the Clonatec and DuPont rapid assays correctly identified 12 sera as HIV-1 antibody-positive; the former produced 5 false-negatives and 3 indeterminates and the latter 7 false-negatives and 1 indeterminate. The majority of the sera used in the evaluation showed evidence of early sero-conversion as many had low absorbance ratios in a screening enzyme immunosorbent assay. Although they represent only a small portion of clinical specimens, they point to the need for careful evaluation of new methodologies, using appropriate, well-characterised sera, before such techniques are accepted for general use.

Evaluation Studies as Topic↗
PubMed1990

Considerations on the further expansion of the AIDS epidemic in South Africa--1990.

An epidemiological composite of the human immunodeficiency virus (HIV) epidemic in South Africa was constructed from reported acquired immunodeficiency syndrome (AIDS) figures, blood donor seroprevalence data and a family of active surveillance studies in the Johannesburg area. Of great concern is the extensive and continuing silent spread of HIV in the urban black population, manifested by doubling times in male and female sexually transmitted disease (STD) clinic attenders of 10.67 and 9.78 months respectively, a doubling time in female family planning (FP) attenders of 6.55 months, and HIV infection rates of 1:56, 1:37 and 1:91, respectively. These data suggest a spread of infection far more extensive than the relatively lower AIDS figures. However, seroprevalence figures in municipal employees of mainly rural origin were considerably lower, only 1:1,250 in black men and none in women, but regular movements between urban and rural areas could well introduce and amplify infection in rural areas. A complete epidemiological picture of HIV can only be attained by employing both the above approach of the family of surveys complemented by a nationwide seroprevalence study to assess HIV penetration into the general 'background' population. Educational interventions should now be particularly targeted to the major risk groups in the urban black heterosexual community.

Acquired Immunodeficiency Syndrome↗