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Thesis (Ph. D.)--University of Alabama at Birmingham, 2008. / Title from first page of PDF file (viewed June 6, 2008). Includes bibliographical references.

Thesis (Ph. D.)--University of Virginia, 2009. / Title from title page. Includes bibliographical references. Also available online through Digital Dissertations.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: New agents for the diagnosis, prevention and treatment of tuberculosis are urgently required. Yet, despite extensive tuberculosis research over recent years, no new drugs, vaccines or diagnostics have been identified to date. It is widely speculated that the major obstacle to the identification of new therapies is the lack of understanding of the hostpathogen interaction. This study has investigated whether patterns of antigen expression correlate with molecular epidemiological data and strain virulence through the analysis of protein expression and antigen recognition profiles of different M tuberculosis clinical isolates. Using polyacrylamide gel electrophoresis, enzyme-linked immunosorbent assay, and Western blotting, protein expression and antigen recognition by two genotypically different clinical strains that differed in their frequency in the study population have been compared. In addition to differences in protein expression and antigen recognition between the clinical strains and the reference strain H37Rv, protein expression differences between the clinical strains themselves were observed which may relate to strain frequency and virulence. Differential protein expression by M tuberculosis strains, may explain the heterogeneous host humoral immune response and why no fully effective serodiagnostic test has been developed to date. To explore this hypothesis, the potential of serodiagnosis in this community, where patients are infected with a wide variety of genotypically distinct strains, was investigated. IgG levels to three mycobacterial antigens showed that serodiagnosis of TB is possible in this community, despite infection by a wide variety of genotypically different M tuberculosis strains. Disease episode affected antibody levels, suggesting that care should be taken when evaluating serological diagnosis for repeat episode patients. This study has shown that M tuberculosis protein expression is dynamic and that the bacillus presents a hypervariabie array of antigens to the host immune system. It is likely that different antigens become immunodominant as antituberculosis chemotherapy progresses, and that these differentially expressed antigens may be tracked as predictors of treatment outcome. This hypothesis was tested by correlating Ag85-specific IgG with treatment response, as assessed by sputum smear conversion after two months of antimycobacterial chemotherapy. No significant correlation between antibody levels and treatment responses was observed, suggesting that antibodies may not be useful surrogate markers or that the incorrect antibody type or mycobacterial antigen were selected. Results were consistent with previous findings where patient-to-patient variation dictated the host humoral response. The results obtained in this study have demonstrated that although bacteriological factors may influence strain prevalence due to antigen variation and immune evasion, both bacteriological and host factors affect humoral immunity. Differential protein expression by M tuberculosis strains has potentially important implications for serodiagnosis and the development of subunit or DNA vaccines, by suggesting that multi-antigen cocktails should be used. Differential protein expression may also explain why patients do not develop adequate protective immunity and are susceptible to reinfection. / AFRIKAANSE OPSOMMING: Daar is 'n dringende behoefte vir nuwe middels vir die diagnosering, voorkoming en behandeling van tuberkulose. Ondanks intense tuberkulose navorsing gedurende die afgelope paar jaar, is daar geen nuwe tuberkulose medikasie, vaksines of diagnostiese metodes geïdentifiseer nie. Daar word gespekuleer dat die hoof struikelblok vir die identifisering van nuwe medikasie die onkunde oor die tuberkulose patogeen is. Deur die analise van proteien-uitdrukking en antigeen-erkenning profiele van verskillende M. tuberculosis kliniese isolate is daar tydens hierdie studie ondersoek ingestel of die patroon van antigeen uitdrukking korreleer met molekulêre epidemiologiese data and stam-virulensie. Proteien-uitdrukking en antigeen-erkenning deur twee genotipies verskillende kliniese stamme wat verskil in hul frekwensie in die bestudeerde populasie, is vergelyk deur middel van poli-akrielamied gel elektroforese, ensiem-gekoppelde immuunabsorberende analise en Westelike oordrag. Addisoneel tot die verskille in proteienuitdrukking en antigeen-ekenning tussen kliniese stamme en die verwysingstam H37Rv, is daar ook verskille aangedui tussen die kliniese stamme self wat kan dui op stam frekwensie en virulensie. Differensiële proteien-uitdrukking deur M. tuberculosis stamme, kan moontlik die heterogene gasheer se humorale immuunreaksie verduidelik en daarmee saam die rede waarom daar nie tot op hede 'n effektiewe sero-diagnostiese toets ontwikkel is nie. Daar is dus ondersoek ingestel na die potensiaal van sero-diagnose in 'n gemeenskap waar pasiënte geïnfekteer is met 'n wye verskeidenheid genotipiese stamme. Die IgG vlakke van drie mikobakteriële antigene het aangedui dat sero-diagnose van tuberkulose moontlik is in hierdie gemeenskap, ten spyte van infektering deur 'n wye verskeidenheid genotipies-verskillende M. tuberculosis stamme. Die tussenspel van die siekte het teenliggaampie-vlakke beïnvloed wat daarop dui dat daar versigtig moet gelet word tydens die evaluering van serologiese diagnose van geïnfekteerde pasiënte wat voorheen siek was. Hierdie studie toon dat M. tuberculosis proteïen-uitdrukking dinamies is en dat die bacillus 'n groot variëteit van antigene tot die immuun sisteem bied. Dit is moontlik dat verskillende antigene immuun dominant kan word soos wat antituberkulose chemoterapie toeneem, en dat hierdie verskillend-uitgedrukte antigene as 'n gevolg daarvan gebruik kan word as voorspellers vir behandeling. Hierdie hipotese is getoets deur die korrelering van Ag85-spesifieke IgG met die reaksie op behandeling soos geëvalueer deur speeksel-monster verandering na twee maande se anti-mikobakteriële chemoterapie. Daar was geen noemenswaardige korrelasie tussen teenliggaampie vlakke en die reaksie op behandeling nie, wat daarop dui dat die teenliggaampies nie toepaslike surrogaat merkers is nie of dat die verkeerde teenliggaampie-tipe of mikobakteriële antigeen geselekteer is. Hierdie resultate bevestig vorige bevindinge waar pasiënt-tot-pasiënt verskille die gasheer se humorale immuunreaksie gedikteer het. Die resultate wat uit hierdie studie volg dui dat alhoewel bakteriologiese faktore die stam-frekwensie kan beïnvloed as gevolg van antigeen-variasie en immuun-ontduiking, kan beide bakteriologiese en gasheer faktore die humorale immuunreaksie beïnvloed. Differensiële proteiën uitdrukking deur 'n verskeidenheid M. tuberculosis stamme het potensieël belangrike toepassings vir sero-diagnose en die ontwikkeling van subeenheid of DNS vaksines wat impliseer dat multi-antigeen mengsels gebruik moet word. Differensiële proteiën uitdrukking mag ook verduidelik waarom pasiënte nie 'n voldoende beskermende immuniteit opbou nie en sodoende ontvanklik is vir her-infeksie.

Thesis (MSc)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: HIV has attained a global distribution and the number of infected people reached an estimated 28.1 million in sub-Saharan Africa at the end of 2001. HIV-1 subtype C is overwhelmingly prevalent in Botswana and South Africa and to date no interventions have been successful enough to curb the rapid spread of the virus. A number of HIV-1 vaccine strategies are being developed, however the breadth and efficacy of such candidate vaccines, many of which are based on the HIV-1 structural genes pol, gag and env, have mostly been found to be inadequate. The HIV-1 accessory genes are attractive components of HIV vaccines due to their role in viral pathogenesis, early expression and the high ratio of conserved CTl epitopes. Yet, because of undesirable properties questions regarding their safety as vaccine components are raised. In this study candidate tat, rev and nefmutants were assessed for efficient expression and inactivation of undesirable functionality. / Plasmid constructs that encode the South African HIV-1 subtype C consensus Tat, Rev and Nef proteins were constructed. The coding sequences of the genes were codon-optimised for optimum protein expression and these synthetic genes were constructed using overlapping 50-mer oligonucleotides. Furthermore, the proteins were mutated at previously described sites by PCR-based site-directed mutagenesis to render them inactive for their respective functions. Corresponding wild-type Tat, Rev and Nef constructs were also made from viral isolates that were least dissimilar to the respective consensus amino acid sequences. tn vitro expression of the different constructs were assessed in 293 cells by Western blotting with polyclonal mouse sera, which were generated by DNA immunisation with one of the Tat, Rev and Nef constructs. The transactivation activity of Tat variants and Rev-mediated nuclear export activity of RRE-containing transcripts were studied in cotransfection experiments using reporter-gene-based assays while Nef functionality was assessed in a cotransfection assay with subsequent flow cytometric analysis of surface CD4 and MHC-I expression on 293 cells. Sequence analysis of the South African HIV-1 subtype C consensus sequences of Tat, Rev and Nef revealed a high degree of similarity with a consensus sequence that was drawn up from a large number of viruses from southern Africa. These consensus sequences were also closer to individual viral isolate sequences than any individual sequences were, indicating that the use of a consensus sequence may serve to reduce genetic diversity between a vaccine and circulating viruses. Expression levels of the sequence-modified tat and nef gene constructs were not significantly higher than the wild-type constructs, however, the codon-optimised rev mutant exhibited markedly higher expression than the wild-type rev construct. Immunoreactivity of the protein with the mouse sera demonstrates expression and immunogenicity of the Tat, Rev and Nef immunogens in mice. In the background of the subtype C Tat, a single C22 mutation was insufficient to inactivate l TRdependent CAT expression in 293T and Hela cells. Yet, this activity was significantly impaired using the single mutation, C3?, or the double mutation, C22C3? Compared to the wild-type Rev, the function of the Rev with a double mutation, M5M10, was completely abrogated. Similarly, while the wild-type Nef and native, codon-optimised consensus Nef proteins mediated CD4 and MHC-I downregulation, CD4 downregulation was completely abrogated in one of the mutants, while both Nef mutants were entirely deficient for MHC-I downregulation. These data demonstrate the high expression levels and impaired functionality of sequence-modified HIV-1 subtype C consensus Tat, Rev and Nef DNA immunogens that may be used as single-standing vaccine components or form part of a multicomponent HIV-1 vaccine. / AFRIKAANSE OPSOMMING: Sedert die eerste gevalle van MIV in die vroeë 1980's beskryf is het die virus wêreldwyd versprei en 'n beraamde 28.1 miljoen mense in sub-Sahara Afrika was teen die einde van 2001 geïnfekteer. MIV-1 subtipe C kom verreweg die meeste voor in Botswana en Suid-Afrika en tans is daar geen suksesvolle tussenkoms wat die vinnige verspreiding van die virus kan stuit nie. 'n Aantal MIV-1 subtipe C entstofstrategieë word tans ontwikkel maar die spektrum en effektiwiteit van sulke entstowwe, waarvan baie op die MIV strukturele gene gag, pol en env gebaseer is, is tans onvoldoende. Die MIV-1 bykomstige gene is aantreklike entstofkomponente omdat hulle vroeg uitgedruk word, 'n belangrike rol in virale patogenese speel en omdat hulle 'n hoë verhouding van gekonserveerde sitotoksiese T-limfosiet (STL) epitope tot grootte besit. Vanweë hierdie gene se verskeie ongewenste eienskappe word vrae ten opsigte van hul veilige insluiting in enstofstrategieë geopper. Hierdie studie omskryf die evaluasie van kandidaat tat, reven nef mutante vir doeltreffende proteïenuitdrukking en funksionele onaktiwiteit. Plasmiedkonstrukte wat vir die Suid-Afrikaanse MIV-1 subtipe C konsensus Tat, Rev en Nef proteïene kodeer is saamgestel. Die koderingsvolgordes van die gene is geoptimiseer vir optimale uitdrukking en die sintetiese gene is van oorvleuelende 50- mer oligonukleotiede vervaardig. Deur van PKR-gebaseerde site-directed mutagenese gebruik te maak is hierdie proteïene gemuteer op posisies wat voorheen geïdentifiseer is. Ooreenstemmende wilde-tipe Tat, Reven Nef konstrukte is gemaak vanaf virale isolate waarvan die aminosuurvolgordes die meeste ooreenstem met dié van die konsensusvolgorde. In vitro uitdrukking van die konstrukte in 293 selle is met behulp van immunoklad met poliklonale muissera bepaal. Die serum is gegenereer deur DNS immunisasie van muise met een elk van die Tat, Reven Nef konstrukte. Die transaktiverings-aktiwiteit van Tat variante en Rev bemiddelde uitvoer van RREbesittende transkripte uit die nukleus is in verklikkergeen kotransfeksie-eksperimente bestudeer. Nef se funksionaliteit is deur kotransfeksie en die daaropvolgende vloeisitometriese analise van 293 selle se oppervlak-CD4 en MHC-I uitdrukking bestudeer. Nukleotiedvolgorde-analise van die Suid-Afrikaanse MIV-1 subtipe C konsensus Tat, Reven Nef proteiëne toon 'n hoë vlak van ooreenkoms met 'n konsensusvolgorde wat afgelei is vanaf 'n groot aantal suider-Afrikaanse virusse. Hierdie konsensusvolgordes is ook meer soortgelyk aan individuele virale isolate as enige individuele volgordes. Vanuit hierdie data kan afgelei word dat die gebruik van so 'n konsensusvolgorde die genetiese diversiteit tussen 'n entstof en sirkuierende virusse kan verminder. Uitdrukkingsvlakke van die volgorde-geoptimiseerde tat en nef geenkonstrukte is nie merkbaar hoër as die van die wilde-tipe konstrukte nie. In teenstelling het die volgorde-geoptimiseerde rev mutant merkbaar hoër uitdrukkingsvlakke as die wildetipe getoon. Immunoreaktiwiteit van die proteïene met die muissera demonstreer dat die Tat, Reven Nef proteïene uitgedruk word en immunogenies in muise is. 'n Enkele C22 mutasie in Tat is nie genoeg om lTR-afhanklike CAT uitdrukking in 293T en Hela selle te inaktiveer nie. In teenstelling is hierdie aktiwiteit geïnhibeer vir Tat proteïene met die enkel mutasie C37 en die dubbel mutasie C22C37. In vergelyking met die funksionele aktiwiteit van die wilde-tipe Rev is dié van die Rev mutant M5M10 heeltemal geïnhibeer. Die wilde-tipe en geoptimiseerde, konsensus Nef proteïene het seloppervlak-CD4 en -MHC-I uitdrukking verlaag, maar hierdie effek van afregulering van CD4 uitdrukking was heeltemaal opgehef in een Nef mutant en van MHC-I uitdrukking in beide Nef mutante. Hierdie data demonstreer die hoë uitdrukkingsvlakke en geïnhibeerde funksionaliteit van volgorde-gemodifiseerde MIV-1 subtipe C konsensus Tat, Reven Nef DNS immunogene wat as enkelstaande enstof kan optree of deel kan uitmaak van 'n multi-komponent MIV-1 entstof.

published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Surgery / Master / Master of Philosophy

published_or_final_version / abstract / Microbiology / Doctoral / Doctor of Philosophy

published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

A HEp-2 cell culture model was used to investigate the invasive properties of Campylobacter species. Two of twenty-five Campylobacter isolates did not invade HEp-2 cells, and one of these isolates did not adhere to the epithelial cells. Penetration of HEp-2 epithelial cells by C. jejuni was significantly (P < 0.05) inhibited with C. jejuni lysates and a MAb (1B4) in competitive inhibition studies. Immunogold electron microscopic studies revealed that the 1B4 MAb bound to the flagella and cell surface of low passage (invasive) C. jejuni M 96, whereas only the flagella of high passage (non-invasive) C. jejuni were labelled. Western blot analysis revealed that the 1B4 MAb identified an epitope on antigens ranging in size from 66 to 44 kDa in invasive and non-invasive organisms. Antigens were also recognized in lysates prepared only from invasive strains from 42 to 38 kDa. Sodium meta-periodate chemical treatment of C. jejuni lysates significantly (P < 0.05) affected its inhibitory capacity. Additionally, proteinase K and sodium meta-periodate treatment of lysates changed the mobility of antigens recognized by the 1B4 MAb. This suggests that the antigens required for epithelial cell penetration by C. jejuni may be glycoprotein in nature and that the functional binding site is dependent upon an intact carbohydrate moiety. Co-infection of HEp-2 epithelial cells with coxsackievirus B3, echovirus 7, polio virus (LSc type 1), porcine enterovirus and Campylobacter isolates was performed to determine if a synergistic effect could be obtained. The invasiveness of C. jejuni was significantly increased for HEp-2 cells pre-infected with echovirus 7, coxsackievirus B3, and UV-inactivated (non-infectious) coxsackievirus B3 particles. Polio and porcine enterovirus had no effect on C. jejuni adherence and invasiveness. C. hyointestinalis and C. mucosalis, two non-invasive isolates, did not invade virus-infected HEp-2 cells. The increase of invasiveness of C. jejuni appears to be the result of specific interactions between the virus and the HEp-2 cell membrane. The data suggest that the invasiveness of Campylobacter is dependent upon the inherent properties of the organism. Virus-induced cell alterations can potentiate the invasiveness of virulent Campylobacter but are not sufficient to allow internalization by non-invasive bacteria.