Novel approaches to the diagnosis of Mycobacterium bovis infection in African buffaloes (Syncerus caffer)

Bernitz, Netanya (2019-12)

Thesis (PhD)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: Mycobacterium bovis(M. bovis) is the pathogen that causes bovine tuberculosis (bTB) in a wide range of host species including livestock and wildlife. Globally, the control of M. bovisinfection is hindered by the existence of wildlife maintenance hosts. In South Africa, African buffaloes (Syncerus caffer) are considered maintenance hosts of bTB, and therefore control in this species will facilitate control in other sympatric wildlife species and livestock. With the limited availability of diagnostic tools and their suboptimal test performancesto detectM. bovisinfection in buffaloes, it is imperative to develop novel approaches to improve the detection ofinfected buffaloes. In this study, the QuantiFERON®TB-Gold (QFT) system in combination with the cattletype®IFN-gamma ELISA, the QFT interferon gamma (IFN-γ)release assay (IGRA), was shown to have high specificity but poor sensitivity in detecting M. bovisinfection in buffaloes. The sensitivityof the QFT IGRA was improved by measuring the chemokineIFN-γ-inducible protein-10 (IP-10)in theQFTIP-10release assay (IPRA). When both cytokines IFN-γ and IP-10 were measured in parallel in the QFT system, sensitivity was further improved and the specificityof the individual assays were maintained. The concentrations of IFN-γ and IP-10 in QFT tubes were used to predictthe presence of macroscopic pathology in M. bovis-infected buffaloes. Lastly, the immunophenotyping of cattle whole blood identified cellular subsets of bovine leukocytes,however, the production of IP-10 in these cells wasnot confirmed. This study has demonstrated that the QFT system is a highly practical stimulation platform to detect M. bovisinfection in buffaloes with high specificity. The QFT system and novel cattletype®IFN-gammaELISA is anIGRA with high specificity that can be used to detect M. bovisinfection in buffalo populations. The cytokine IP-10 is a more sensitive biomarker than IFN-γ and when these two cytokines are measured in parallel in the QFT system, the detection of infected buffaloes is maximised, the specificityis high and the testing procedure is simplified. Finally, the magnitude of IP-10 and IFN-γ concentrations in QFT-processed whole blood can be usedas indicators of bTB pathology in M. bovis-infected buffaloes

AFRIKAANSE OPSOMMING: Die patogeen Mycobacterium bovis(M. bovis) veroorsaak beestuberkulose (bTB) in ‘n wye reeks gashere wat vee en wild insluit. Wereldwyd word die beheer van M. bovisinfeksie bemoeilik as gevolg van die teenwoordigheid van nstandhoudingsgashere in die wildsbevolking. Afrikabuffels (Syncerus caffer)word as belangrike instandhoudingsgashere van bTB in Suid Afrika beskou met die gevolg dat siektebeheer in hierdie spesie die beheer van bTB in ander simpatriese wildsoorte en vee sal fasiliteer. Met die beperkte beskikbaarheid van diagnostiese tegnieke engepaardgaande suboptimale toets prestasie, het dit dus noodsaaklik geword om nuwe benaderings wat verbeterde opsporing van M. bovisin buffels sal teweegbring, te ontwikkel. Hierdie studie het getoon dat die QuantiFERON®-TB Gold (QFT) interferon gamma (IFN-γ) vrystellingstoets (IGRA), ’n kombinasie van die QFT sisteem en die cattletype®IFN-gamma ELISA,hoë spesifisiteit maar swak sensitiwiteit vir die opsporing van M. bovisin buffelshet. Die sensitiwiteit van die QFT IGRA kon verhoog word deur die chemokien interferongamma-geïnduseerde proteïen-10 (IP-10) te meet met dieQFT IP-10 vrystellingstoets (IPRA). Deur beide IFN-γ en IP-10 in parallel te meet in die QFT sisteem, is die sensitiwiteit verder verbeter sonder verlies van spesifisiteit van die toets. Die konsentrasies van IFN-γ en IP-10 in QFT buise kon die teenwoordigheid van makroskopiese letsels in M. bovisbesmette buffels voorspel. Laastens is subgroepe van beesleukosiete deur immunofenotipering van heel beesbloed geidentifiseer, alhoewel die produksie van IP-10 deur hierdie selle nie bevestig kon word nie. Hierdie studie het gedemonstreer dat die QFT sisteem ‘n uiterse praktiese stimulasieplatform is om M. bovismet spesifisiteit te diagnoseer. Die kombinasie van die QFT sisteem met die nuwe cattletype®IFN-gamma ELISA lewer ‘n hoogs spesifisiteitIGRA wat gebruik kan word om M. bovisinfeksie in buffelbevolkings te diagnoseer. Die chemokien IP-10 is ‘n meer sensitiewe biomerker as IFN-γ, maar wanneer hulle in parallel gemeet word in die QFT sisteem, lei dit tot die maksimum opsporing van besmette buffels met ‘n hoë spesifisiteit terwyl die toetstegniek vereenvoudig is. Ter afsluiting, die vlak van IP-10 en IFN-γ konsentrasies wat in heel beesbloed in die QFT sisteem gemeet is, kan as aanwyser dien om siekteletsels in M. bovisbesmette buffels te voorspel.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/106922
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