The use of mathematical models in studying disease epidemics can be diverse, from the focused study of the role of a single determinant of the epidemic, or to the overall estimation of morbidity and mortality. In using simple deterministic models, a balance is struck between biological and social complexities, and the high data input demands of mathematical models. This thesis aims to apply the use of deterministic mathematical models to the studies of HIV and hepatitis C epidemiology in the Asia-Pacific region. In Australia, about 85% of reported HIV cases are among homosexual men. Casual homosexual partnerships made up 40% of incident HIV cases in 1995 increasing to 65% in 2004. In the state of New South Wales, it was estimated that over 7,500 people were living with HIV/AIDS in 2005, increasing to over 10,000 by 2016 with existing levels of intervention. Intervention measures were estimated to have prevented some 44,500 cases, the majority being among injecting drug users through the Needle and Syringe Programmes. Models for the HIV epidemics in developing countries were also developed incorporating multiple routes of HIV transmission. For Papua New Guinea, it was estimated 64,000 people were living with HIV/AIDS in 2005, rising to over 500,000 by 2025 with current levels of intervention. High levels of interventions, in particular increased condom use, will be required to achieve a stabilisation or reduction in HIV prevalence. In East Timor, the HIV epidemic is still in the early stages with 138 people estimated to be living with HIV/AIDS, rising to 5,000 by 2025 with minimal intervention. For HCV, models of the epidemic in Australia showed HCV incidence peaking in 1999, followed by a decline reaching 9,700 incident cases in 2005. Of 197,000 estimated chronic HCV cases in 2005, 58% had stage F 0/1 liver disease, 15% F 2/3 liver disease, and 2% HCV-related cirrhosis. Models estimated 210 and 105 people developed HCV-related liver failure and hepatocellular carcinoma, respectively. Comparisons of modelled HCV long-term sequelae projections with linkage data showed relatively good agreement, despite discrepancies in liver-related deaths. To decrease the number of chronic HCV, at least a tripling of treatment coverage would be required. These models provide estimates of the current levels of epidemics as well as projections of future scenarios under different intervention strategies, which have an important role in the planning of strategies, as well as assessment of previous epidemic conditions.

Thesis (Ph. D.)--University of Sydney, 2009. / Title from title screen (viewed 31 March 2009). Submitted in fulfilment of the of the requirements for the degree of Doctor of Philosophy to the Discipline of Medicine, Faculty of Medicine. Degree awarded 2009; thesis submitted 2008. Includes bibliographical references. Also available in print form.

Thesis (Ph. D., Geography)--University of Idaho, December 2008. / Major professor: Harley Johansen. Includes bibliographical references (leaves 193-202). Also available online (PDF file) by subscription or by purchasing the individual file.

Thesis (M.A.)--State University of New York at Binghamton, Dept. of Anthropology, 2006. / Includes bibliographical references.

Magister Legum - LLM

Thesis (MScMedSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Introduction: Chronic HIV-1 infection is characterized by immune activation and dysregulation of immune homeostasis, which impacts on multiple immune cell types. The B-cell compartment, which plays an important role in the producing neutralizing antibodies, is also dysregulated in HIV- 1 infection. In this study we investigated peripheral blood B-cell subset distribution, and changes in expression of cellular activation, inhibition, and apoptosis signaling markers in both untreated chronic HIV-1 infected individuals and healthy uninfected controls. The neuropeptide immune modulator, vasoactive intestinal peptide (VIP) is known to selectively down-regulate activation of CD4+ T-cells in various disease settings including HIV-1, however to our knowledge, no studies have investigated the effect of VIP inhibition on B-cell activation. Materials & Methods: A total of 21 HIV+ve (CD4 count >250 cells/µl), and 19 HIV-ve individuals were recruited from the Emavundleni voluntary testing and counseling clinic in Crossroads, Western Province, South Africa. Whole blood was stained to distinguish B-cell subsets (activated memory (AM: CD21-CD27+), resting memory (RM: CD21+CD27+), mature naïve (MN: CD21+CD27-), or tissue-like memory (TLM: CD21loCD27lo). In addition expression of markers of B-cell activation (CD126, CD86, CD38, CD284, CD287), inhibition (CD72, CD85j, CD300a, CD305, CD307d), and apoptosis signaling (CD95), was assessed ex vivo by flow cytometry (BD FACSCanto II). For determination of functional responsiveness isolated B-cells (RosetteSep, Stemcell Technologies) were cultured for 18h (37°C, 5%CO2) without stimulation or stimulated with TLR ligands (LPS or R848). Stimulation experiments were also performed in the presence or absence of VIP. Results: Chronic HIV-1 infection affected B-cell subset distribution. The percentage (%) of TLM was increased by 59.24%, and %RM was decreased by 22.73% (both p<0.01). Total expression of the VIP receptor VPAC2 was decreased by 47.35% (p=0.0296). Subsets had a mixed phenotype ex vivo; HIV infection upregulated CD38 (by 59.56%, p=0.0004), CD72 (by 60.70%, p=0.0396), CD307d (by 68.63%, p=0.0015) on AM, while RM B-cells had increased expression of TLR4 (by 107.04%, p=0.0057) and TLR7 (by 208.14%, p=0.0199). TLM B cells (i.e. exhausted phenotype) displayed upregulated TLR7 (by 550%, p=0.0128) and CD307d (by 72.40% p=0.045) expression. MN B-cells had increased CD72 expression (by 70.98%, p=0.0026). R848 upregulated CD86 expression by 42.20% on AM (p<0.01), and by 56.06% on RM B-cells (p<0.01), which was significantly downregulated with VIP inhibition (both p<0.05). Similarly, CD95 expression on RM, TLM, and MN B-cells increased by 31.10% (p<0.001), 21.46% (p<0.01), and 39.92% (p<0.01) with R848 stimulation respectively, which was also significantly downregulated with VIP inhibition. Conclusion: These data indicate that B-cells in untreated HIV infection display increased levels of activation, and also the potential for increased susceptibility to apoptosis as evidenced by increased FAS (CD95) expression. VIP significantly down-regulated markers of activation, inhibition, and apoptosis signaling. Dysregulation of B-cells is thus apparent in asymptomatic stable chronic HIV-1 infection, which may impact on both inefficient neutralizing antibody production and hypergammaglobulinemia. The ability of VIP to prevent stimulationassociated marker upregulation may indicate that VIP is a potential therapeutic agent. Its immuno-modulatory properties were demonstrated to limit B-cell hyperactivation, and selectively down-regulate apoptosis and mark it out for further investigation. / AFRIKAANSE OPSOMMING: Inleiding: Immunaktivering en ongekoppelde immuun-homeostase is kenmerke van chroniese MIVinfeksie. Ons het perifere bloed B-sel subgroep-verspreiding, en veranderinge in die uitdrukking van merkers van aktivering, inhibisie, en apoptose in 'n onbehandelde MIV-1 besmettende groep ondersoek (in vergelyk met 'n gesonde onbesmettende kontrole). Die immuun-moduleerder, vasoaktiewe intestinale peptied (VIP) is bekend om aktivasie van geaktiveerde CD4+ T-selle te verminder, maar tot ons kennis, is daar geen studies wat die effek van VIP-inhibisie op B-sel aktivering ondersoek het, in die konteks van MIV-1 infeksie. Materiaal & Metodes: MIV+we individue (CD4-telling >250 selle/µl) , en MIVwe kontroles is gewerf uit die vrywillige toetsing en berading Emavundleni kliniek, Crossroads, Westelike Provinsie, Suid-Afrika. Bsel subgroepe is gedefinieer as geaktiveerde geheue (AM: CD21- CD27+ ), rusende geheue (RM: CD21+ CD27+ ), volwasse naïef (MN: CD21+ CD27- ), of weefsel-agtige geheue (TLM: CD21loCD27lo). Merkers van aktivering (CD126, CD86, CD38, CD284, CD287), inhibisie (CD72, CD85j, CD300a, CD305, CD307d), en apoptose signalering (CD95) is via vloeisitometrie (BD FACSCanto II) op B-selle ex vivo en ook op geïsoleerde B-selle (RosetteSep, Cell Technologies) ondersoek. Vir die bepaling van funksionele responsiwiteit, geïsoleerde B-selle (RosetteSep, StemCell Technologies) was vir 18h (37°C, 5%CO2) gekweek, sonder stimulasie of gestimuleer met TLR ligande (LPS of R848). Stimulasie eksperimente het ook in die teenwoordigheid of afwesigheid van VIP plaasgevind. Resultate: Chroniese MIV-1 infeksie het B-sel subset verspreiding geraak. Die persentasie (%) van TLM is verhoog deur 59,24%, en% RM het met 22.73% afgeneem (beide p <0,01). Totale uitdrukking van die VIP reseptor VPAC2 het met 47,35% afgeneem (p = 0,0296). Subgroepe het 'n gemengde ex vivo fenotipe; MIV-infeksie het CD38 (deur 59,56%, p=0,0004), CD72 (deur 60,70%, p=0,0396), CD307d (deur 68,63%, p=0,0015) op AM verhoog, terwyl RM Bselle het verhoogde uitdrukking van TLR4 (deur 107,04%, p=0,0057) en TLR7 (deur 208,14%, p=0,0199). TLM B-selle (die uitgeputtende fenotiep) het verhoogde TLR7 (deur 550%, p=0,0128) en CD307d (deur 72,40% p=0.045) uitdrukking gewys. MN B-selle het verhoogde uitdrukking van CD72 (deur 70,98%, p = 0,0026). R848 het CD86 uitdrukking op AM deur 42,20%, en op RM deur 56,06% toegeneem (beide p <0,01). Dit het met VIP inhibisie beduidend afgeneem (beide p <0.05). CD95 uitdrukking was soortgelyk verhoog op RM, TLM, en MN B-selle met 31.10% (p <0.001), 21,46% (p <0,01), en 39,92% (p <0,01) met R848 stimulasie. Al drie het beduidend afgeneem met VIP inhibisie. Gevolgtrekking: Hierdie data dui daarop dat B-selle in onbehandelde MIV-infeksie vertoon verhoogde aktiveringsvlakke, en ook die potensiaal vir verhoogde vatbaarheid vir apoptose soos bewys deur verhoogde uitdrukking van FAS (CD95). VIP het beduidend merkers van aktivering, inhibisie, en apoptose af-gereguleer. Wanfunksie van B-selle is dus in asimptomatiese stabiele chroniese MIV-1 infeksie duidelik, wat impak kan hê op beide oneffektiewe neutraliserende teenliggaampie produksie, en hiepergammaglobulinimie. Die vermoë van VIP stimulasie-verwante merker opregulasie te voorkom kan aandui dat VIP 'n potensiële terapeutiese agent is. VIP se immuno-moduleerende eiendomme is gedemonstreer om Bsel hieperaktiveering te beperk, en selektief apoptose afreguleer, en merk dit vir verdere ondersoek.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: HIV infection is one of the world’s biggest health problems, with millions of people infected worldwide. HIV infects cells in the immune system, where it primarily targets CD4+ T helper cells and without treatment, the disease leads to the collapse of the host immune system and ultimately death. Mathematical models have been used extensively to study the epidemiology of HIV/AIDS. They have proven to be effective tools in studying the transmission dynamics of HIV. These models provide predictions that can help better our understanding of the epidemiological patterns of HIV, especially the mechanism associated with the spread of the disease. In this thesis we made a functional comparison between existing epidemiological models for HIV, with the focus of the comparison on the force of infection (FOI). The spread of infection is a crucial part of any infectious disease, as the dynamics of the disease depends greatly on the rate of transmission from an infectious individual to a susceptible individual. First, a review was done to see what deterministic epidemiological models exist. We found that many manuscripts do not provide the necessary information to recreate the authors’ results and only a small amount of the models could be simulated. The reason for this is mainly due to a lack of information or due to mistakes in the article. The models were divided into four categories for the analysis. On the basis of the FOI, we distinguished between frequency- or density-dependent transmission, and as a second criterion we distinguished models on the sexual activity of the AIDS group. Subsequently, the models were compared in terms of their FOI, within and between these classes. We showed that for larger populations, frequency-dependent transmission should be used. This is the case for HIV, where the disease is mainly spread through sexual contact. Inclusion of AIDS patients in the group of infectious individuals is important for the accuracy of transmission dynamics. More than half of the studies that were selected in the review assumed that AIDS patients are too sick to engage in risky sexual behaviour. We see that including AIDS patients in the infectious individuals class has a significant effect on the FOI when the value for the probability of transmission for an individual with AIDS is bigger than that of the other classes. The analysis shows that the FOI can vary depending on the parameter values and the assumptions made. Many models compress various parameter values into one, most often the transmission probability. Not showing the parameter values separately makes it difficult to understand how the FOI works, since there are unknown factors that have an influence. Improving the accuracy of the FOI can help us to better understand what factors influence it, and also produce more realistic results. Writing the probability of transmission as a function of the viral load can help to make the FOI more accurate and also help in the understanding of the effects that viral dynamics have on the population transmission dynamics. / AFRIKAANSE OPSOMMING: MIV-infeksie is een van die wêreld se grootste gesondheidsprobleme, met miljoene mense wat wêreldwyd geïnfekteer is. MIV infekteer selle in die immuunstelsel, waar dit hoofsaaklik CD4+ T-helperselle teiken. Sonder behandeling lei die siekte tot die ineenstorting van die gasheer se immuunstelsel en uiteindelik sy dood. Wiskundige modelle word breedvoerig gebruik om die epidemiologie van MIV/vigs te bestudeer. Die modelle is doeltreffende instrumente in die studie van die oordrag-dinamika van MIV. Hulle lewer voorspellings wat kan help om ons begrip van epidemiologiese patrone van MIV, veral die meganisme wat verband hou met die verspreiding van die siekte, te verbeter. In hierdie tesis het ons ‘n funksionele vergelyking tussen bestaande epidemiologiese modelle vir MIV gedoen, met die fokus van die vergelyking op die tempo van infeksie (TVI). Die verspreiding van infeksie is ‘n belangrike deel van enige aansteeklike siekte, aangesien die dinamika van die siekte grootliks afhang van die tempo van oordrag van ‘n aansteeklike persoon na ‘n vatbare persoon. ‘n Oorsig is gedoen om te sien watter kompartementele epidemiologiese modelle alreeds bestaan. Ons het gevind dat baie van die manuskripte nie die nodige inligting voorsien wat nodig is om die resultate van die skrywers te repliseer nie, en slegs ‘n klein hoeveelheid van die modelle kon gesimuleer word. Die rede hiervoor is hoofsaaklik as gevolg van ‘n gebrek aan inligting of van foute in die artikel. Die modelle is in vier kategorieë vir die analise verdeel. Op grond van die TVI het ons tussen frekwensie- of digtheidsafhanklike oordrag onderskei, en as ‘n tweede kriterium het ons die modelle op die seksuele aktiwiteit van die vigs-groep onderskei. Daarna is die modelle binne en tussen die klasse vergelyk in terme van hul TVIs. Daar is gewys dat frekwensie-afhanklike oordrag gebruik moet word vir groter bevolkings. Dit is die geval van MIV, waar die siekte hoofsaaklik versprei word deur seksuele kontak. Die insluiting van die vigs-pasiënte in die groep van aansteeklike individue is belangrik vir die akkuraatheid van die oordrag-dinamika van MIV. Meer as helfte van die uitgesoekte studies aanvaar dat vigs-pasiënte te siek is om betrokke te raak by riskante seksuele gedrag. Ons sien dat die insluiting van vigs-pasiënte in die groep van aansteeklike individue ‘n beduidende uitwerking op die TVI het wanneer die waarde van die waarskynlikheid van oordrag van ‘n individu met vigs groter is as dié van die ander klasse. Die analise toon dat die TVI kan wissel afhangende van die parameter waardes en die aannames wat gemaak is. Baie modelle voeg verskeie parameter waardes bymekaar vir die waarskynlikheid van oordrag. Wanneer die parameter waardes nie apart gewys word nie, is dit moeilik om die werking van die TVI te verstaan, want daar is onbekende faktore wat ‘n invloed op die TVI het. Die verbetering van die akkuraatheid van die TVI kan ons help om die faktore wat dit beïnvloed beter te verstaan, en dit kan ook help om meer realistiese resultate te produseer. Om die waarskynlikheid van oordrag as ‘n funksie van die viruslading te skryf kan help om die TVI meer akkuraat te maak en dit kan ook help om die effek wat virale dinamika op die bevolkingsoordrag-dinamika het, beter te verstaan.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: A simple and rapid scatter-based flow cytometric assay was developed to detect apoptosis in CD4+ and CD8+ T cells from a mixed population of cells. The assay was suitable for children. Apoptotic PBMCs were confirmed by morphologic assessment in clinical samples ex vivo and after overnight culture. The scatter-based assay was validated in a number of ways. Firstly, PBMCs were irradiated with 500 rads and cultured overnight to induce apoptosis. Thereafter, PBMCs were labeled with a CD4 MAb. CD4+ cells were sorted into apoptotic and viable populations by scatter characteristics (diminished forward and increased side scatter). Morphology was assessed by fluorescence microscopy. The majority of cells with apoptotic scatter characteristics had apoptotic morphology (chromatin condensation) (80.6%). Ninety-two percent of cells from the viable region had normal morphology. CD4+ T cell apoptosis measured by scatter was then correlated with the TdT assay for DNA fragmentation. Lastly, CD4+ T cell apoptosis by scatter and annexin V uptake were also shown to correlate. In the latter experiments, PBMC morphology and cell death by trypan blue uptake were studied simultaneously and confirmed the two flow cytometric assays. Apoptosis of CD4+ and CD8+ T cells has been shown in PBMCs from HIV infected adults analyzed after overnight culture. Since cell death may be an artifact of in vitro culture, and because there is little information on apoptosis in paediatric HIV disease, I undertook a cross-sectional analysis in PBMCs analyzed immediately ex vivo from HIV infected children and adults. Patients were studied in Denver, CO, USA. PBMCs from 21 children, 4 adolescents and 9 adults and seronegative age-matched controls were stained for CD4 and CD8 surface markers. Apoptotic cells were detected in a newly characterized flow cytometric assay by diminished forward and increased side scatter. For the scatter assay, PBMCs had been labeled initially by an indirect method involving an intermediary incubation in the presence of biotinylated MAbs at 37°C for 30 minutes prior to incubating with streptavidin-FITC at 4°C for 20 minutes. Thereafter, the intermediary incubation step was removed and PBMCs were incubated with PE-conjugated CD4+ and CD8+ MAbs. Both CD4+ and CD8+ T cell apoptosis appeared enhanced in the indirect method. The significant differences were abolished after subtraction of data from simultaneously studied time-matched controls. CD4+ and CD8+ T cell apoptosis were significantly higher in HIV-infected study subjects than in simultaneously studied seronegative controls. PBMCs were assayed immediately ex vivo and after overnight culture after stimulation by an anti-TCR MAb as well as spontaneously. There was a direct correlation between CD4+ and CD8+ T cell apoptosis and CD4+ T cell depletion. A significant correlation was also shown between apoptosis immediately ex vivo and after overnight culture. I then studied apoptosis in a South African population comprising 18 symptomatic children and 4 seroreverters. CD4+ and CD8+ T cell apoptosis were significantly higher in symptomatic HIV-1-infected children than in seroreverters and seronegative controls. CD4+ T cell apoptosis correlated with depletion of CD4+ T cell percentage in symptomatic HIV-1-infected children. I also noted elevated CD4+ T cell apoptosis in patients recovering from intercurrent disease in comparison to those who were either acutely ill or relatively asymptomatic outpatient attendees. Lastly, I compared CD4+ and CD8+ T cell apoptosis in cohorts from Denver, CO and Tygerberg Children’s Hospital, South Africa. I selected only patients with moderate or severe HIV infection from both centers. South African patients were significantly younger, more malnourished, had higher gamma globulin levels and were less likely to receive ART. CD8+ T cell apoptosis was higher in North American patients suggesting a possible impairment in CD8+ activity in the South African study subjects. / AFRIKAANSE OPSOMMING: ‘n Eenvoudige en vinnige vloei sitometriese toets is ontwikkel om apoptose aan te toon vanuit ‘n gemengde populasie selle. Dit moes geskik wees vir kinders van wie net klein volumes bloed getrek kan word. Die teenwoordigheid van apoptotiese perifere bloed mononuklere selle (PBMS) was vasgestel deur morfologiese beoordeling in kliniese monsters ex vivo en na oornag kultuur. Die ondersoek is gebasseer op die verstrooings patroon van bestraalde PBMS wat apoptose induseer. PBMS is gemerk met a CD4 MAb. CD4+ selle is gesorteer in apoptotiese en lewensvatbare populasies deur verstrooings karakteristieke. Morfologie is beoordeel deur fluoreserende mikroskopie. Die meerderheid van selle met apoptotiese verstrooings karakteristieke (verminderde voorwaartse en verhoogde sywaartse verstrooings patroon) het apoptotiese karakteristieke gehad (80.6%). Twee-en-negentig persent van selle van die lewensvatbare area het normale morfologie gehad. Verstrooings patroon is ook gekorreleer met die TdT meting vir DNA fragmentasie in kliniese monsters van MIV-geinfekteerde kinders. Daarna is Annexin V gekorreleer met verstrooings patroon, apoptotiese morfologie en trypan blou opname in selle wat blootgestel is na verskillende konsentrasies van beauvericin. Apoptose van CD4+ en CD8+ T-selle is bewys in PBMS van MIV-geinfekteerde volwassenes na oornag kultuur. Omdat sel dood ‘n artefak van in vitro kultuur kan wees, en omdat daar min inligting is oor apoptose in paediatriese MIV siekte, het ek onderneem om ‘n deursnee analiese te doen in PBMS wat onmiddelik ex vivo geanaliseer is vanaf MlV-geinfekteerde kinders en volwassenes. Die pasiente is bestudeer in Denver, Colorado, VS A. PBMS van 22 kinders, 4 adolessente en 9 volwassenes en seronegatiewe ouderdoms-gepasde kontroles is gekleur vir CD4+ en CD8+ oppervlaksmerkers. Apoptotiese selle is vloeisitometries aangedui deur verandering in verstrooings patroon. Vir die doeleindes van die verstrooings assay is die PBMS aanvanklik deur ‘n indirekte metode gemerk, wat ‘n intermediere inkubasie in die teenwoordigheid van biogetinileerde MAbs by 37°C vir 30 minute voor dit geinkubeer is met streptavidin- FITC by 4°C vir 20 minute behels. Daarna is die intermediere inkubasie stap verwyder en PBMC is geinkubeer met PE - gekonjugeerde CD4+ and CD8+ MAbs. Beide die CD4+ en CD8+ T-sel apoptose het verhoog voorgekom met die indirekte metode. Die betekenisvolle verskille het verdwyn na data van gelyktydige tyd - gepaarde kontroles afgetrek is. CD4+ en CD8+ T-sel apoptose was betekenisvol hoër in MIV-geinfekteerde studie gevalle as in gelyktydig bestudeerde seronegatiewe kontroles. PBMS assays is gedoen onmiddelik ex vivo en na oornag inkubasie na stimulasie deur ‘n anti-TCR MAb, sowel as spontaan. Daar was ‘n direkte korrelasie tussen CD4+ en CD8+ T sel apoptosis en CD4+ T sel vermindering. ‘n Beduidende korrelasie is ook getoon tussen apoptose onmiddelik ex vivo en na oornag kultuur. Daaropvolgend het ek apoptose in ‘n Suid Afrikaanse populasie van 18 simptomatiese kinders en 4 serologies terukerende gevalle bestudeer. CD4+ en CD8+ T sel apoptose was aansienlik hoër in siptomatiese MIV - 1-geinfekteerde kinders as in die serologies terukerende gevalle en seronegatiewe kontroles. CD4+ T sel apoptose het gekorrelleer met vermindering van CD4+ T sel persentasie. Ek het ook opgemerk dat daar ‘n tendens bestaan het tot verhoogde CD4+ T sel apoptose in pasiente wat besig was om te herstel van bykomende siektes. Ek het CD4+ en CD8+ T sel apoptose in kohorte van Denver, Colorado en Tygerberg, Suid Afrika vergelyk. Suid Afrikaanse pasiente was jonger en meer wangevoed as hul Noord Amerikaanse ewekniee. Suid Afrikaanse kinders het ook meer gevorderde siekte gehad. Wanneer pasiente gepas is vir die graad van ernstigheid van siekte en slegs die minder ernstige (B) en ernstige siekte (C) vergelyk is, was CD8+ T sel apoptose beduidend hoër in Noord Amerikaanse pasiente. Hierdie waarneming ondersteun die hipotese dat CD 8+ T sel aktiwiteit moontlik onderdruk mag wees in simptomatiese Suid Afrikaanse MIV-1-geinfekteerde kinders.

Thesis (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The risk of human immunodeficiency virus type-1 (HIV-1) infection and rate of progression towards development of the acquired immunodeficiency syndrome (AIDS) is determined by a combination of viral characteristics, immune function and host genetic variation. Although mutations of the chemokine and chemokine co-receptor genes and allelic variation of the major histocompatibility complex (MHC) have been studied extensively, variation in these host genetic factors does not explain the differences in HIV/AIDS susceptibility in all cases. This study represents the first analysis of new candidate genes implicated in iron metabolism and immune function in relation to HIV-1 disease in the African context. Both case-control association studies and genotype-phenotype correlations were performed to determine the potential functional significance of genetic variants that may be involved, either directly or indirectly, in susceptibility to HIV-1 disease in the South African population. Genotyping was performed to identify potentially important polymorphisms in the solute carrier family 11 member 1 (SLC11A 1), haemochromatosis (HFE) and protein-tyrosine phosphatase receptor-type C (PTPRC/CD45) genes in HIV-seropositive versus HIVseronegative individuals. This was followed by HLA-B27 genotyping in HIV-1 infected individuals with known disease status to determine the potential impact of combined genotypes for different mutations identified in the same study cohort. Preferential association with any of the mutations screened for in the CCR5, SLC 11A1, HFE or CD45 genes were not detected in HLA-B27 positive individuals identified. These findings were in accordance with the independent protective role of HLA-B27 in relation to disease progression in HIV-1 infected individuals. Although differences in allelic distribution were not significant between the study groups, an apparently African-specific mutation 32A~G, identified in an exonic splicing silencer element (ESS-1) of the CD45 gene, appeared to predominate in HIV-1 infected subjects with WHO Class I disease status and slow progression to AIDS. This mutation was present in 35.7% (5/14) of HIV-seropositive individuals with WHO Class I disease status, whilst absent in 22 HIV-seropositive patients with rapid disease progression. This finding may be related to differences in proportions of both CD4+ and CD8+ subsets observed following flow cytometry (FACs) analys.s in two HIV-seropositive individuals with mutation 32A~G, compared with an HIV-seropositive individual without this mutation. Analysis of the iron-related SLC11A1 and HFE genes did not reveal significant associations with modified risk of HIV-1 infection or progression to AIDS in our predominantly African study population. However, the effect of the virus on iron metabolism was demonstrated for the first time at the DNA level. Haemoglobin levels were significantly reduced in both HIV-seropositive (P=O.004) and HIV-seronegative (P=O.02) Black Africans with mutation IVS3-48c~g in the HFE gene, compared with mutationnegative individuals in both groups. Since this effect was more pronounced in HIV-infected individuals compared with controls, presence of the HFE mutation seems to result in an even stronger effect on haemoglobin levels, which may be related to the acute phase response following virus infection. This effect possibly results from genetic variation in a nearby gene involved in innate immunity, most likely in the HLA region on chromosome 6. It therefore seems possible that genetic variation in any of the host molecules involved in response to infection could contribute to clinical outcome. The significance of the multitude of host genetic factors investigated in this study, or previously implicated in susceptibility to HIV-1 infection and disease progression, revealed a complex interrelationship between the host and HIV-1. In some instances the disease process following HIV-1 infection depends on combined effects of different mutations occurring in the same individual, while independent effects of specific genes in conjunction with environmental influences may explain diverse clinical outcomes in others. / AFRIKAANSE OPSOMMING: Die risiko vir menslike immuniteitsgebrek virus tipe-1 (MIV-1) infeksie en die progressietempo vir ontwikkeling van die verworwe immuniteits gebrek sindroom (VIGS) word hoofsaaklik deur fn kombinasie van virale eienskappe, immuunfunksie en gasheer genetiese variasie bepaal. Alhoewel mutasies van die chemokien en chemokien koreseptor gene en alleliese variasie van die major weefsel-verenigbaarheidskompleks (MWVK) reeds omvattend bestudeer is, verklaar variasie van hierdie gasheer genetiese faktore nie noodwendig verskille in vatbaarheid vir MIVNIGS in alle gevalle nie. Hierdie studie verteenwoordig die eerste analise van nuwe kandidaatgene, geïmpliseer in yster metabolisme en immuunfunksie in die konteks van MIV-1 siekte in Swart bevolkingsgroepe. Beide gevalle-kontrole assosiasie-studies en genotipe-fenotipe korrelasies is uitgevoer om moontlik betekenisvolle verwantskappe met genetiese variante te bepaal, wat moontlik direk of indirek betrokke mag wees in vatbaarheid vir MIV-1 siekte in die Suid Afrikaanse populasie. Genotipering van die solute draer familie 11 lid 1 (SLC11A1), hemochromatose (HFE) en protein-tirosien fosfatase reseptor-tipe C (PTFRC/CD45) gene is uitgevoer in beide MIVseropositiewe en MIV-seronegatiewe individue. Daaropvolgend is genotipering van die menslike leukosien antigeen-B27 (MLA-B27) uitgevoer in MIV-1 geïnfekteerde individue met bekende siekte-status, om die potensiële impak van gekombineerde genotipes te bepaal vir verskillende mutasies wat in dieselfde studie populasie geïdentifiseer is. Voorkeur-assosiasie is nie waargeneem vir enige van die mutasies waarvoor geanaliseer is in die CCR5, SLC11A1, HFE of CD45 gene nie. Hierdie bevinding is in ooreenstemming met die onafhanklike rol van MLA-B27 in verwantskap met siekte progressie in MIV-1 geïnfekteerde individue. Alhoewel die alleelverspreiding van In Afrika-spesifieke mutasie 32A~GI wat in In eksoniese splytingsdemper-element (ESS-1) van die CD45 geen geïdentifiseer is, nie statisties betekenisvolle verskille getoon het tussen studiegroepe nie, is die mutasie oorheersend waargeneem in MIV-1 geïnfekteerde individue met WGO Klas I siektestatus en stadige progressie na VIGS. Hierdie mutasie was teenwoordig in 35.7% (5/14) van HIV-seropositiewe individue met WGO Klas I siekte-status, terwyl dit afwesig was in 22 HIV-seropositiewe pasiënte met vinnige siekteprogressie. Hierdie bevinding mag moontlik verband hou met verskille in verhoudings van beide die CD4+ en CD8+ substelle, soos waargeneem gedurende vloei sitometriese (VAS, FACs) analise in twee HIV-seropositiewe individue met mutasie 32A---+G, in vergelyking met en HIV-seropositiewe individu sonder hierdie mutasie. Analise van die yster-verwante SLC11A 1 en HFE gene het nie betekenisvolle assosiasies opgelewer met gemodifiseerde risiko vir MIV-1 siekte of progressie na VIGS in die hoofsaaklik Swart studie-populasie nie. Die effek van die virus op ystermetabolisme is wel vir die eerste keer op DNS vlak gedemonstreer. Hemoglobien vlakke was betekenisvol verlaag in beide MIV-seropositiewe (P=O.004) en MIV-seronegatiewe (P=O.02) Swart individue met die HFE geen IVS3-48C---+G mutasie, in vergelyking met mutasie-negatiewe individue in beide groepe. Aangesien hierdie effek meer uitgesproke was in MIVgeïnfekteerde individue as in kontroles, blyk dit dat die teenwoordigheid van die HFE mutasie die hemoglobienvlakke tot engroter mate beïnvloed weens die akute fase respons wat verband hou met die virusinfeksie. Hierdie effek kan moontlik toegeskryf word aan genetiese variasie in ennaasliggende geen wat in aangebore immuniteit betrokke is, heel moontlik in die MLA gebied van chromosoom 6. Dit wil dus voorkom asof genetiese variasie in enige van die gasheer molekules betrokke by respons op infeksie kan bydra tot die kliniese uitkoms. Die belangrike rol van die veelvuldige gasheer genetiese faktore wat in hierdie studie bestudeer is, of wat voorheen geïmpliseer is in vatbaarheid vir MIV-1 infeksie en siekte progressie, het enkomplekse inter-verwantskap tussen gasheer en MIV-1 geopenbaar. In sommige gevalle is die siekte-proses na MIV-1 infeksie afhanklik van gekombineerde effekte van verskillende mutasies in dieselfde individu, terwylonafhanklike effekte van spesifieke gene tesame met omgewings-invloede uiteenlopende kliniese uitkomste in ander mag verklaar.

published_or_final_version / abstract / Paediatrics and Adolescent Medicine / Doctoral / Doctor of Philosophy