Masters Degrees (Medical Virology)

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Browsing Masters Degrees (Medical Virology) by browse.metadata.advisor "Liebrich, Walter"

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    The relationship between Cytomegalovirusspecific cellular immune response and CD4+ T cell count in HIV positive individuals in a South African setting
    (Stellenbosch : University of Stellenbosch, 2011-03) Arendse, Germaine Veronique; Liebrich, Walter; Preiser, Wolfgang; University of Stellenbosch. Faculty of Health Sciences. Dept. of Pathology. Medical Virology.
    ENGLISH ABSTRACT: Introduction: Reactivation of human cytomegalovirus (HCMV) infection in individuals infected with human immunodeficiency virus (HIV) may lead to life-threatening end-organ diseases (EOD). The EOD becomes clinically apparent when a critical number of cells in the affected organs become damaged as a consequence of HCMV-infection. Treatment of the HCMV-associated disease at this point may not be effective. Therefore, early detection of HCMV reactivation may be useful to guide pre-emptive therapy. Aim: The aim of this study was to determine whether there is a point at which the HCMV-specific cellular immune response breaks down, as determined by the interferon-gamma (IFN-γ) enzyme-linked immunospot (ELISPOT) assay, and HCMV reactivation occurs in HIV-positive, antiretroviral therapy (ART)-naïve individuals in a South African setting. This was done in relation to the CD4+ T cell count and the HCMV viral load as determined by real-time polymerase chain reaction (qPCR). Materials and methods: Fifty-two (52) HIV-infected, ART-naïve subjects were recruited from primary healthcare centres that they attended for the management of their HIV infection. Heparinised blood samples were collected to quantify the HCMV-specific cellular immune response using the IFN-γ-ELISPOT assay and to determine the HCMV IgG serostatus. Ethylenediaminetetraacetic acid (EDTA) blood samples were collected for the determination of the CD4+ T cell counts and the HCMV viral loads. Results: All 52 subjects recruited were confirmed to be HIV-HCMV co-infected based on their HCMV IgG serostatus. The results of 34 subjects with completed data sets were analysed. The CD4+ T cell counts of these subjects ranged from 10 to 784 cells/μl. Twenty-two (22) (65%) subjects had positive HCMV IFN-γ-ELISPOT results with 94% having no detectable HCMV viral loads. All subjects (28) with a CD4+ T cell count above 100 cells/μl had undetectable HCMV viral loads. Two of the six subjects with CD4+ T cell counts <100 cells/μl had detectable HCMV viral loads. There was no statistically significant association between the CD4+ T cell counts and the HCMV IFN-γ-ELISPOT results. Conclusion: No specific point could be determined when there is loss of integrity of the HCMV-specific cellular immune response in HIV-positive individuals. Low CD4+ T cell counts did not correlate with HCMV IFN-γ-ELISPOT results suggesting that the HCMV-specific cellular immunity did not necessarily break down at low CD4+ T cell counts. Nevertheless, a CD4+ T cell count above 100 cells/μl appeared to be protective against viraemia as determined by the HCMV viral load qPCR. The IFN-γ-ELISPOT assay was employed as a tool to determine the integrity of the HCMV-specific cellular immune response in HIV-positive individuals. However, the IFN-γ-ELISPOT assay should be used in conjunction with the CD4+ T cell count and the HCMV viral load qPCR to determine when there is loss of integrity of the HCMV-specific cellular immune response and HCMV reactivation occurs. This may assist clinicians in their choice of management and appropriate pre-emptive treatment in the HIV-HCMV co-infected individual at a risk for HCMV reactivation.