Browsing by Author "Burgers, Wendy A."
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- ItemDetection of natural infection with Mycobacterium intracellulare in healthy wild-caught Chacma baboons (Papio ursinus)by ESAT-6 and CFP-10 IFN- ELISPOT tests following a tuberculosis outbreak(BioMed Central, 2008-02) Chege, Gerald K.; Warren, Robin M.; Gey van Pittius, Nico C.; Burgers, Wendy A.; Wilkinson, Robert J.; Shephard, Enid G.; Williamson, Anna-LiseBackground: Both tuberculous and non-tuberculous mycobacteria can cause infection in nonhuman primates (NHP), indicating the existence of potential zoonotic transmission between these animals and visitors to zoos or animal handlers in primate facilities. Screening of mycobacterial infections in NHP is traditionally done by tuberculin skin test (TST), which is unable to distinguish between pathogenic and non-pathogenic mycobacterial infections. In this study, we investigated the use of ESAT-6 and CFP-10 for detection of mycobacterial infections in a wild-caught baboon colony after one baboon died of tuberculosis (TB). Methods: Peripheral blood lymphocytes for interferon-gamma enzyme-linked immunospot assay (IFN-γ ELISPOT) assay were obtained from TST positive baboons and those in contact with tuberculous baboons before being euthanased, autopsied and lung tissues taken for histology and mycobacterial culture. Results: Both ESAT-6 and CFP-10 IFN-γ ELISPOT assays were able to detect early M. tuberculosis but also M. intracellulare infection. Although this indicates potential cross-reactivity with M. intracellulare antigens, the method was able to distinguish M. bovis BCG vaccination from M. tuberculosis infection. This assay performed better than the TST, which failed to detect one M. tuberculosis and two early M. intracellulare infections. Conclusion: These results suggest that the IFN-γ ELISPOT assay could improve the detection of M tuberculosis infections when screening NHP. There is some doubt, however, concerning specificity, as the assay scored positive three animals infected with M. intracellulare.
- ItemIntra- and inter-clade cross-reactivity by HIV-1 gag specific T-cells reveals exclusive and commonly targeted regions : implications for current vaccine trials(Public Library of Science, 2011-10-12) Zembe, Lycias; Burgers, Wendy A.; Jaspan, Heather B.; Bekker, Linda-Gail; Bredell, Helba; Stevens, Gwynneth; Gilmour, Jill; Cox, Josephine H.; Fast, Patricia; Hayes, Peter; Vardas, Eftyhia; Williamson, Carolyn; Gray, Clive M.ENGLISH ABSTRACT: The genetic diversity of HIV-1 across the globe is a major challenge for developing an HIV vaccine. To facilitate immunogen design, it is important to characterize clusters of commonly targeted T-cell epitopes across different HIV clades. To address this, we examined 39 HIV-1 clade C infected individuals for IFN-c Gag-specific T-cell responses using five sets of overlapping peptides, two sets matching clade C vaccine candidates derived from strains from South Africa and China, and three peptide sets corresponding to consensus clades A, B, and D sequences. The magnitude and breadth of T-cell responses against the two clade C peptide sets did not differ, however clade C peptides were preferentially recognized compared to the other peptide sets. A total of 84 peptides were recognized, of which 19 were exclusively from clade C, 8 exclusively from clade B, one peptide each from A and D and 17 were commonly recognized by clade A, B, C and D. The entropy of the exclusively recognized peptides was significantly higher than that of commonly recognized peptides (p = 0.0128) and the median peptide processing scores were significantly higher for the peptide variants recognized versus those not recognized (p = 0.0001). Consistent with these results, the predicted Major Histocompatibility Complex Class I IC50 values were significantly lower for the recognized peptide variants compared to those not recognized in the ELISPOT assay (p,0.0001), suggesting that peptide variation between clades, resulting in lack of cross-clade recognition, has been shaped by host immune selection pressure. Overall, our study shows that clade C infected individuals recognize clade C peptides with greater frequency and higher magnitude than other clades, and that a selection of highly conserved epitope regions within Gag are commonly recognized and give rise to cross-clade reactivities.
- ItemPD-1 expression on mycobacterium tuberculosis-specific CD4 T cells is associated with bacterial load in human tuberculosis(Frontiers Media, 2018) Day, Cheryl L.; Abrahams, Deborah A.; Bunjun, Rubina; Stone, Lynnett; De Kock, Marwou; Walzl, Gerhard; Wilkinson, Robert J.; Burgers, Wendy A.; Hanekom, Willem A.ENGLISH ABSTRACT: Persistent antigen stimulation in chronic infections has been associated with antigen-specific T cell dysfunction and upregulation of inhibitory receptors, including programmed cell death protein 1 (PD-1). Pulmonary tuberculosis (TB) disease is characterized by high levels of Mycobacterium tuberculosis (Mtb), yet the relationship between bacterial load, PD-1 expression, and Mtb-specific T cell function in human TB has not been well-defined. Using peripheral blood samples from adults with LTBI and with pulmonary TB disease, we tested the hypothesis that PD-1 expression is associated with bacterial load and functional capacity of Mtb-specific T cell responses. We found that PD-1 was expressed at significantly higher levels on Th1 cytokine-producing Mtb-specific CD4 T cells from patients with smear-positive TB, compared with smear-negative TB and LTBI, which decreased after completion of anti-TB treatment. By contrast, expression of PD-1 on Mtb-specific CD8 T cells was significantly lower than on Mtb-specific CD4 T cells and did not differ by Mtb infection and disease status. In vitro stimulation of PBMC with Mtb antigens demonstrated that PD-1 is induced on proliferating Mtb-specific CD4 T cells and that Th1 cytokine production capacity is preferentially maintained within PD-1+ proliferating CD4 T cells, compared with proliferating Mtb-specific CD4 T cells that lack PD-1 expression. Together, these data indicate that expression of PD-1 on Mtb-specific CD4 T cells is indicative of mycobacterial antigen exposure and identifies a population of effector cells with Th1 cytokine production capacity. These studies provide novel insights into the role of the PD-1 pathway in regulating CD4 and CD8 T cell responses in Mtb infection and provide rationale for future studies to evaluate PD-1 expression on antigen-specific CD4 T cells as a potential biomarker for bacterial load and treatment response in human TB.
- ItemT cell‑tropic HIV efciently infects alveolar macrophages through contact with infected CD4+T cells(Nature, 2021-02) Schiff, Abigail E.; Linder, Alice H.; Luhembo, Shillah N.; Banning, Stephanie; Deymier, Martin J.; Diefenbach, Thomas J.; Dickey, Amy K.; Tsibris, Athe M.; Balazs, Alejandro B.; Cho, Josalyn L.; Medoff, Benjamin D.; Walzl, Gerhard; Wilkinson, Robert J.; Burgers, Wendy A.; Corleis, Bjorn; Kwon, Douglas S.Alveolar macrophages (AMs) are critical for defense against airborne pathogens and AM dysfunction is thought to contribute to the increased burden of pulmonary infections observed in individuals living with HIV-1 (HIV). While HIV nucleic acids have been detected in AMs early in infection, circulating HIV during acute and chronic infection is usually CCR5 T cell-tropic (T-tropic) and enters macrophages inefficiently in vitro. The mechanism by which T-tropic viruses infect AMs remains unknown. We collected AMs by bronchoscopy performed in HIV-infected, antiretroviral therapy (ART)-naive and uninfected subjects. We found that viral constructs made with primary HIV envelope sequences isolated from both AMs and plasma were T-tropic and inefficiently infected macrophages. However, these isolates productively infected macrophages when co-cultured with HIV-infected CD4+ T cells. In addition, we provide evidence that T-tropic HIV is transmitted from infected CD4+ T cells to the AM cytosol. We conclude that AM-derived HIV isolates are T-tropic and can enter macrophages through contact with an infected CD4+ T cell, which results in productive infection of AMs. CD4+ T cell-dependent entry of HIV into AMs helps explain the presence of HIV in AMs despite inefficient cell-free infection, and may contribute to AM dysfunction in people living with HIV.