1,720,962 research outputs found
An investigation of hepatitis B virus in antenatal women tested for human immunodeficiency virus, in the Western Cape Province of South Africa
Get PDFThesis (MScMedSc)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Hepatitis B virus (HBV) immunisation protocols in much of Africa are based on data from the pre-human immunodeficiency virus (pre-HIV) era that indicated that HBV transmission occurs predominantly horizontally between siblings and play-mates rather than vertically from mother to child. The immunosuppression associated with HIV infection however may release HBV from immune control resulting in higher HBV viral loads, which may increase the risk of perinatal mother to child transmission of HBV. The aim of this study was to determine the prevalence and characteristics of chronic HBV infection in HIV-infected pregnant women compared to HIV-uninfected pregnant women in the Western Cape province of South Africa.
Ethical approval was obtained to conduct a retrospective, matched case-control, unlinked anonymous study using residual plasma samples from the 9355 pregnant women included in the Western Cape's 2008 National HIV and Syphilis Antenatal Survey. Samples were tested for HBsAg on the AxSYM (Abbott, Chicago, IL) and confirmed by neutralization. Confirmed HBsAg-positive samples were tested for HBeAg, anti-HBe and anti-HD (Diasorin, Saluggia, Italy) and had HBV viral load and genotyping done. In addition, HBsAg-negative samples were tested for anti-HBc.
Samples from 1549 HIV-infected pregnant women were included and matched to the same number of samples from age- and race-matched HIV-uninfected women. Median age of 26 years, parity and education were similar in the two groups. The prevalence of HBsAg was 3.4% for the HIV-infected group and 2.9% for the HIV-uninfected group. HBV DNA loads of greater than 104 IU/ml were detected in 32.1% of HBsAg-positive, HIV/HBV co-infected women, and in 14.3% HBsAg positive, HBV mono-infected women. Among the HIV-infected group 18.9% of HBsAg-positive were HBeAg positive, with a median viral load of 7.93 log10 IU/ml; whilst 15.5% HIV-uninfected women were positive for HBeAg with a median viral load of 6.07 log10 IU/ml. Genotype A was seen in 92.6% of the isolates while 7.4% of the isolates were genotype D. Serum total anti-HBc antibodies that are a marker of past infection were detected in 42.2% of HIV-infected and in 24.1% of HIV-uninfected women that were negative for HBsAg. No positive sample for anti-HD was seen among all HBsAg-positive samples. This data indicates that there is increased exposure to HBV in HIV-infected pregnant women than in HIV-uninfected women and that a greater proportion of HIV-infected pregnant women compared to HBV mono-infected pregnant women may be at increased risk of transmitting HBV to their infants. Further studies are needed to determine the rate of vertical transmission of HBV in the HIV era.AFRIKAANSE OPSOMMING: Hepatitis B virus (HBV) immunisasie protokolle vir meeste dele van Afrika is gebaseer op data versamel in die era voor MIV. Die data dui aan dat HBV oordrag hoofsaaklik deur horisontale transmissie tussen broers, susters en speelmaats eerder as vertikale transmissie van moeder na kind plaasvind. Die onderdrukking van die immuunstelsel as gevolg van MIV infeksie kan egter lei tot 'n verhoogde risiko van perinatale HBV oordrag van moeder na kind. Die doel van hierdie studie was om die voorkoms en karakter van chroniese HBV infeksie in MIV-positiewe swanger vroue te vergelyk met die van MIV-negatiewe swanger vroue.
Etiese goedkeuring is verkry om 'n retrospektiewe, deursnee-, ongekoppelde anonieme studie uit te voer wat gebruik maak van oorblywende plasma monsters van 9355 swanger vroue wat ingesluit is in die Wes-Kaap 2008 Nasionale MIV en Sifilis Voorgeboortelike Opname. Die monsters was getoets vir HBsAg antiliggame (AxSYM, Abbott, Chicago, IL) en bevestig deur neutralisasie toetse. Positiewe monsters was getoets vir HBeAg en anti-HBe (Diasorin, Saluggia, Italië). HBV viruslading en genotipering was ook op HBsAg positiewe monsters gedoen. Die HBsAg negatiewe monsters was getoets vir die teenwoordigheid van anti-HBc.
Monsters van 1549 MIV-positiewe swanger vroue was ingesluit in die studie. Dieselfde aantal monsters van MIV-negatiewe vroue, met ooreenstemende ouderdom en etnisiteit, was ingesluit as kontroles. Die gemiddelde ouderdom van albei groepe was 26 jaar. Pariteit en opvoeding was dieselfde in albei groepe. Die voorkomssyfer van HbsAg was 3.4% in die MIV-positiewe groep en 2.8% in die MIV-negatiewe groep. HBV DNS ladings van meer as 104 IU/ml was waargeneem in 32.1% van die MIV-mede-geinfekteerde vroue en in 14.3% van die MIV-negatiewe groep. In die MIV-positiewe groep was 18.9% vroue HBeAg positief, met 'n gemiddelde virale lading van 7.93 log10 IU/ml, terwyl 15.5% MIV-negatiewe vroue positief was vir HBeAg met 'n gemiddelde virale lading van 6.07 log10 IU/ml. In ons studie was 92.6% van die monsters genotipe A en 7.4% genotipe D. Toatale anti-HBc antiliggame, 'n merker van vorige infeksie, was gevind in 42.2% van MIV-mede-geïnfekteerde vroue en 24.1% van MIV-negatiewe vroue wat negatief was vir HBsAg antiliggame.
Data van ons studie dui op 'n verhoogde risiko vir vertikale HBV transmissie van MIV-positiewe moeders na hul babas. Verdere studies word benodig om vas te stel of vertikale transmissie van HBV van MIV-positiewe vroue na hul babas plaasvind.Wellcome TrustPoliomyelitis Research Foundatio
Hepatitis B virus-associated hepatocellular carcinoma in South Africa: epidemiology and impact of HIV-1 co-infection and immune dysregulation
Get PDFThesis (PhD)--Stellenbosch University, 2016ENGLISH ABSTRACT : Co-infection with the human immunodeficiency virus (HIV) negatively impacts the natural progression of hepatitis B virus (HBV) infection, including causing rapid progression to liver fibrosis and hepatocellular carcinoma (HCC). In sub-Saharan Africa the overlap between high HIV and HBV prevalence may increase the incidence of HCC. The aim of this study was to investigate the effect of HIV co-infection on presentation of HCC among HBV-infected patients. Since HCC is thought to be driven by ongoing severe inflammation, the study also evaluated the association between the expression of markers of immune activation/exhaustion and liver inflammation in patients with chronic hepatitis B (CHB) to determine if the risk of hepatofibrosis is increased by exposure to gut microbial products and compared HIV-infected patients with HBV-infected and HIV-HBV co-infected patients.
Ethical approval was obtained to conduct two sub-studies. The first sub-study (HCC Epidemiology Study) involved recruitment of patients diagnosed with HCC at oncology units of selected teaching hospitals in South Africa. A total of 107 HCC cases were recruited between December 2012 and October 2015. Demographic, laboratory and clinical data together with blood specimens were collected. Patients were tested for HBV, hepatitis C virus (HCV) and HIV. Molecular characterization of HBV and HCV was also performed. For the second sub-study (Liver Fibrosis and Immune Markers Study), 46 HBV/HIV co-infected; 47 HBV monoinfected; 39 HIV monoinfected and; 39 HIV-/HBV-uninfected controls were recruited following informed consent. All HIV-infected patients had been on highly active antiretroviral therapy (HAART) for ≥3 months. Liver stiffness measurements were taken using the Fibroscan 402. Cell-based immunomarkers of activation/exhaustion were measured using flow cytometry of fresh whole blood. Soluble serum/plasma immunomarkers were measured using ELISA and Luminex. HIV and HBV viral loads and genotyping of HBV were performed.
Of 107 cases in the HCC Epidemiology study, 83 (78%) were male and 68/106 (64%, 95% CI: 59-77) were positive for HBsAg. HIV seropositivity was seen in 22/100 (22%, 95% CI: 14-30) of all HCC cases. Among HBsAg-positive HCC cases, 19/66 (29%, 95% CI: 18-40) were HIV-infected compared to only 3/34 (9%) among those that were HBsAg-negative, p=0.04. The proportion of females among the HBV/HIV co-infected HCC cases 6/18 (33%, 95% CI: 11-55) was significantly higher compared to those that were HBV-mono-infected 6/47 (13%, 95% CI: 3-23), p=0.005. HIV/HBV co-infected females presented younger, at mean age 36.8 years (95% CI: 32.2-41.5) compared to 50.5 years (95% CI: 30.2-70.8) in HBV-mono-infected women, p=0.09. Males continue to be disproportionally affected with HCC. There is a trend towards younger age at diagnosis of HCC among HIV-positive compared to HIV-negative women.
The Liver Fibrosis and Immune Markers Study showed a high percentage of CD8+ T lymphocytes from co-infected subjects expressing HLA-DR/CD38 and PD-1 (p<0.05). Soluble CD14 and IP-10 were also significantly elevated in plasma of co-infected patients. Co-infected subjects exhibited delayed immune recovery with lower CD4/CD8 T cell ratio; CD4 cell counts and frequent HIV viremia compared to HIV mono-infected participants (p<0.05). The HBV mono-infected group had the highest proportion of participants with moderate/advanced liver fibrosis measured by Fibroscan, together with highest plasma concentrations of most of the cytokines measured. The results showed positive correlation between HIV and HBV viral replication and liver fibrosis. The results suggest that there is persistent T-lymphocyte dysregulation and delayed immune recovery in ART-experienced HBV/HIV co-infected patients. However this does not appear to be associated with severity of liver fibrosis in this cohort. HAART used in HIV is also effective against HBV and may therefore have led to control of viral replication leading to better fibrosis scores compared to the HBV mono-infected patients. Moderate/advanced liver fibrosis in HBV-mono-infection may well be an indicator of poor access to HBV screening and treatment.AFRIKAANSE OPSOMMING : Geen Afrikaanse opsomming geskikbaar nieDoctora
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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