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Thesis (PhD)--Stellenbosch University, 2012. / Bibliography / ENGLISH ABSTRACT: Most individuals latently infected with Mycobacterium tuberculosis (Mtb) contain the infection by a balance of effector and regulatory immune responses. However, this balance can be influenced by steroid hormones such as glucocorticoids (GCs), which are known to increase the risk of reactivation of TB. The contraceptive medroxyprogesterone acetate (MPA), which also possesses selective glucocorticoid activity, is widely used in developing countries with approximately 60% of women on contraceptives using MPA in our study cohort. Therefore, our aim was to investigate the effect of this hormone on protective immune responses to BCG in HIV negative household contacts of active TB patients. When PBMCs of TB household contacts were stimulated with BCG in the presence of 10 μM MPA; this hormone displayed both glucocorticoid as well as progestogenic properties. Similarly to cortisol, MPA suppressed antigen specific expression of a range of cytokines including IL-1α, IL-1ra, IL- 17, TNFα, IL-5 and IFNγ. Dose response curves showed that MPA can also alter expression of some cytokines at lower contraceptive doses (in the nano molar range). To assess whether this effect of MPA in vitro also occurs in women using this hormone as contraceptive the PBMCs of MPA users and controls were stimulated with BCG and the levels of up to 29 different cytokines measured by luminex analysis. PBMCs of MPA users produced significantly lower levels of cytokines involved in immune responses against Mtb such as IL-12p40, IL-1α, IL-10, IL-13 and G-CSF, which corresponds with lower numbers of circulating monocytes observed in these women. These findings warrant further investigation and clinical trials should investigate the risk of progression from latent to active TB disease in women using this contraceptive. These trials, however, require a large number of participants and are prohibitively expensive; therefore it was decided to setup an Mtb/MPA mouse model to determine the effect of MPA on the disease outcome. BALB/c and C57BL/6 mice were injected with a weekly dose of one mg MPA or PBS and infected with 30 colony forming units of Mtb H37Rv one week after commencing the hormonal treatment. Both strains were included to establish which strain best represents the human model. Three and eight weeks post infection the MPA treated C57BL/6 mice had a significantly higher bacterial load in their lungs compared to untreated mice, whereas no difference was found in the bacterial loads of the BALB/c mice. MPA treated C57BL/6 mice had significantly lower serum levels of IL-10 and G-CSF and MPA treated BALB/c mice lower serum levels of IFNγ, when compared to untreated mice. Furthermore, cells isolated from the MLNs of MPA treated C57BL/6 mice, produced significantly less TNFα, significantly more IP-10 and less IL-10 in response to PPD, while MLN cells of MPA treated BALB/c mice produced significantly less IFNγ, IL-2, IL-17, GM-CSF and MCP-1. Data of the C57BL/6 mouse strain correlated with our human data and can it therefore be said that the C57BL/6 mouse strain, together with the serum concentration of MPA used in these experiments, is a good model to determine the effect of MPA in the context of a low dose Mtb infection. To conclude MPA use could therefore alter susceptibility to TB, TB disease severity as well as change the efficacy of new BCG-based vaccines, especially prime-boost vaccine strategies which may be administered to adult of adolescent women in the future. / AFRIKAANSE OPSOMMING: Die meeste mense wat latent met Mycobacterium tuberculosis (Mtb) geïnfekteer is, hou die infeksie onder beheer deur ʼn balans te handhaaf tussen effektor en regulatoriese immuunresponse. Hierdie balans kan egter beïnvloed word deur steroïedhormone soos glukokortikoïede (GCs), wat bewys is om die risiko van die heraktivering van TB te verhoog. Die voorbehoedmiddel medroksiprogesteroon-asetaat (MPA), wat ook selektiewe glukokortikoïed-aktiwiteit toon, word wyd gebruik in ontwikkelende lande en omtrent 60% van die vrouens in ons studie-bevolking wat voorbehoedmiddels gebruik, gebruik MPA. Om dié rede wou ons die effek van hierdie hormoon op die beskermende immuun-response teenoor M.bovis Bacilli Calmette-Guérin (BCG) in HIV negatiewe huishoudelike kontakte (HHKe) van pasiënte met aktiewe TB ondersoek. Ons het gevind dat wanneer perifere bloed mononukleêre selle (PBMSe) met BCG gestimuleer word in die teenwoordigheid van 10 μM MPA, hierdie hormoon beide glukokortikoïede en progesterogeniese eienskappe toon. Soos kortisol het MPA die antigeenspesifieke-uitdrukking van ʼn reeks sitokiene, insluitend IL-1α, IL-1ra, IL-17, TNFα, IL-5 en IFNγ, onderdruk. Respons kurwes wat verskillende konsentrasies van hormoon insluit, het getoon dat MPA ook by laer (nano-molare) dosisse die uitdrukking van sommige sitokiene kon verander. Om te bepaal of hierdie in vitro effek van MPA ook in vrouens wat MPA as voorbehoedmiddel gebruik voorkom, het ons PBMSe van MPA-gebruikers and kontroles met BCG gestimuleer en die vlakke van tot 29 verskillende sitokiene met behulp van Luminexanalise gemeet. PBMSe van MPA-gebruikers produseer beduidende laer vlakke van IL-12p40, IL-1α, IL- 10, IL-13 en G-CSF, wat elk in imuunafweerreaksies teen Mtb betrokke is. Die afname in dié sitokiene het gepaard gegaan met laer hoeveelhede sirkulerende monosiete. Ons resultate regverdig verdere ondersoeke en kliniese proewe behoort die risiko van progressie vanaf latente tot aktiewe TB in vrouens wat hierdie voorbehoedmiddel gebruik te bepaal. Sulke proewe vereis egter groot getalle deelnemers en is skrikwekkend duur, om die rede het ons besluit om ʼn Mtb/MPA muis-model op te stel om sodoende die algehele effek van MPA op die uitkoms van die siekte te bepaal. BALB/c en C57BL/6 muise is met ʼn weeklikse dosis van een mg MPA of sout oplossing ingespuit en een week na die aanvang van die hormoon behandeling met 30 kolonie-vormende eenhede Mtb H37Rv geïnfekteer. Beide muis tipes was ingesluit om sodoende te bepaal watter tipe die mens data die beste verteenwoordig. Drie en agt weke na die infeksie het die MPA-behandelde C57BL/6 muise ‘n beduidende hoër bakteriële lading in hul longe gehad as die onbehandelde muise, maar was daar geen verskil in die bakteriële ladings in die longe van die BALB/c muise nie. MPA-behandelde C57BL/6 muise het beduidende laer serumvlakke van IL-10 en G-CSF gehad, terwyl MPA-behandelde BALB/c muise laer serumvlakke van IFNγ gehad het. Verder het ons gevind dat die geisoleerde limfosiete van MPA-behandelde C57BL/6 muise beduidend minder TNFα, beduidend meer IP-10 en minder IL-10 geproduseer het na stimulasie met PPD, terwyl die limfosiete van MPA-behandelde BALB/c muise beduidend minder IFNγ, IL-2, IL-17, GM-CSF en MCP-1 geproduseer het. Data van die C57BL/6 muise stem ooreen met die van ons mens studie en ons kan dus vermeld dat die C57BL/6 muise, tesame met die spesifieke serumkonsentrasie van MPA wat gebruik is, ʼn goeie model is om die effek van MPA in die konteks van ʼn lae-dosis Mtb-infeksie te bestudeer. MPA gebruik kan dus die vatbaarheid vir TB, asook die erns van die siekte verander en kan ook die effektiwiteit van nuwe BCG-gebaseerde entstowwe, veral prima-hupstoot enstowwe, wat moontlik in die nabye toekoms vir volwasse en adolessente vroue toegedien kan word, verander.

Thesis (MScMedSc)--University of Stellenbosch, 2011. / Please refer to full text to view abstract.