Browsing by Author "Ndlovu, Hlumani"

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    Dikakapa everday heroes - African journeys to success
    (2013) Xulu, Khethelo; Kiravu, Agano; Nofemela, Andile; Ndlovu, Hlumani; Moholisa, Retsilisitsoe; Abera, Aron
    This book, Dikakapa Everyday Heroes: African journeys to success, is the proud initiative of a social intervention project called Dikakapa: Every-day Heroes. "Dikakapa Everyday Heroes: African journeys to success" is a collection of short personal stories by young Africans. In the book, the authors exercise self introspection and examination to reflect on how they navigated the formal education system (matric and/or tertiary level) to emerge as winners in their chosen career paths. It is a motivational tool for those aspiring to join tertiary institutions and is an invaluable resource for new university entrants who often struggle to balance their new found independence with the demands and discipline that varsity requires.
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    IL-4Rα-associated antigen processing by B cells promotes immunity in Nippostrongylus brasiliensis infection
    (Public Library of Science, 2013) Horsnell, William G C; Darby, Matthew G; Hoving, Jennifer C; Nieuwenhuizen, Natalie; McSorley, Henry J; Ndlovu, Hlumani; Bobat, Saeeda; Kimberg, Matti; Kirstein, Frank; Cutler, Anthony J
    In this study, B cell function in protective TH2 immunity against N. brasiliensis infection was investigated. Protection against secondary infection depended on IL-4Rα and IL-13; but not IL-4. Protection did not associate with parasite specific antibody responses. Re-infection of B cell-specific IL-4Rα−/− mice resulted in increased worm burdens compared to control mice, despite their equivalent capacity to control primary infection. Impaired protection correlated with reduced lymphocyte IL-13 production and B cell MHC class II and CD86 surface expression. Adoptive transfer of in vivo N. brasiliensis primed IL-4Rα expressing B cells into naïve BALB/c mice, but not IL-4Rα or IL-13 deficient B cells, conferred protection against primary N. brasiliensis infection. This protection required MHC class II compatibility on B cells suggesting cognate interactions by B cells with CD4+ T cells were important to co-ordinate immunity. Furthermore, the rapid nature of these protective effects by B cells suggested non-BCR mediated mechanisms, such as via Toll Like Receptors, was involved, and this was supported by transfer experiments using antigen pulsed Myd88−/− B cells. These data suggest TLR dependent antigen processing by IL-4Rα-responsive B cells producing IL-13 contribute significantly to CD4+ T cell-mediated protective immunity against N. brasiliensis infection.
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    Inducible deletion of CD28 prior to secondary nippostrongylus brasiliensis infection impairs worm expulsion and recall of protective memory CD4 (+) T cell responses
    (Public Library of Science, 2014) Ndlovu, Hlumani; Darby, Mathew; Froelich, Monika; Horsnell, William; Lühder, Fred; Hünig, Thomas; Brombacher, Frank
    IL-13 driven Th2 immunity is indispensable for host protection against infection with the gastrointestinal nematode Nippostronglus brasiliensis. Disruption of CD28 mediated costimulation impairs development of adequate Th2 immunity, showing an importance for CD28 during the initiation of an immune response against this pathogen. In this study, we used global CD28−/− mice and a recently established mouse model that allows for inducible deletion of the cd28 gene by oral administration of tamoxifen (CD28−/loxCre+/−+TM) to resolve the controversy surrounding the requirement of CD28 costimulation for recall of protective memory responses against pathogenic infections. Following primary infection with N. brasiliensis, CD28−/− mice had delayed expulsion of adult worms in the small intestine compared to wild-type C57BL/6 mice that cleared the infection by day 9 post-infection. Delayed expulsion was associated with reduced production of IL-13 and reduced serum levels of antigen specific IgG1 and total IgE. Interestingly, abrogation of CD28 costimulation in CD28−/loxCre+/− mice by oral administration of tamoxifen prior to secondary infection with N. brasiliensis resulted in impaired worm expulsion, similarly to infected CD28−/− mice. This was associated with reduced production of the Th2 cytokines IL-13 and IL-4, diminished serum titres of antigen specific IgG1 and total IgE and a reduced CXCR5+ TFH cell population. Furthermore, total number of CD4+ T cells and B220+ B cells secreting Th1 and Th2 cytokines were significantly reduced in CD28−/− mice and tamoxifen treated CD28−/loxCre+/− mice compared to C57BL/6 mice. Importantly, interfering with CD28 costimulatory signalling before re-infection impaired the recruitment and/or expansion of central and effector memory CD4+ T cells and follicular B cells to the draining lymph node of tamoxifen treated CD28−/loxCre+/− mice. Therefore, it can be concluded that CD28 costimulation is essential for conferring host protection during secondary N. brasiliensis infection.
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    Investigating the anti-inflammatory effects of plant derived compounds in tuberculosis using the THP-1 macrophage model
    (2023) Rajh, Caryn; Ndlovu, Hlumani
    Background Tuberculosis (TB) is a highly communicable disease that is caused by the bacillus, Mycobacterium tuberculosis. TB is responsible for devastating morbidity and mortality worldwide, especially in the developing world. TB can be effectively treated with the currently available drugs; however, poor adherence to therapy and the emergence of drug resistant bacteria has significantly impaired efforts to eradicate TB. Therefore, new therapies and therapeutic strategies are required to combat TB. One of the proposed new strategies is to develop host-directed therapies (HDTs) that are aimed at boosting the host's innate ability to fight the infection and ameliorate the deleterious tissue pathology associated with advanced TB. Repurposed drugs and plant-derived compounds with antiinflammatory effects have been explored for potential use as HDT's. Objectives To evaluate the anti-inflammatory effects of plant-derived compounds in macrophages infected with live Mtb strain H37Rv. Results We found that Ruscogenin failed to modulate cytokine secretion in macrophages that were either infected with live Mtb strain H37Rv or macrophages that were pre-treated with the compound prior to infection with Mtb, except for lowering IL-6 secretion. Leonurine significantly lowered the levels of IL-1β, TNF and IL-6 in macrophages that were pre-treated with the compound for 24 hours prior to infection with live Mtb. We also showed that Withaferin A decreased IL-1β and IL-6 secretion in macrophages infected with Mtb prior to treatment with the compound. Finally, pre-treating macrophages with Withaferin A prior to infection with Mtb decreased the secretion of TNF and IL-6 compared to the untreated and infected macrophages. Conclusion Leonurine and Withaferin A appear to possess anti-inflammatory effects in macrophages infected with live Mtb. Their potential use as HDTs needs to be explored further in animal models.
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    Investigation of mycobacterial cell wall genes and their requirement for survival in immune related stressful conditions
    (2020) Samuels, Veneshley; Marakalala, Mohlopheni Jackson; Ndlovu, Hlumani
    Tuberculosis (TB) disease, caused by the pathogen Mycobacterium tuberculosis (Mtb), remains a major global health problem claiming 1.5-2 million lives annually. One of the major factors contributing towards Mtb's success as a pathogen is its unique cell wall and its ability to counteract various arms of the host's immune response. Understanding these survival mechanisms will help us develop new therapeutic interventions that can enhance the capacity of the immune system to kill the pathogen. A recent genome scale study profiled a list of candidate genes that are predicted to be essential for Mtb survival of host mediated responses. One candidate was ftsEX, a protein complex comprised of an ATP binding domain, FtsE, and a transmembrane domain, FtsX. FtsEX functions through interaction with a periplasmic hydrolase, RipC. FtsEX homologs in other bacteria have been linked to a key role in regulation of PG hydrolysis during elongation and division. Using M. smegmatis as a model, we hypothesised that FtsEX and RipC are required in the regulation of PG hydrolysis during normal cell wall elongation and division under stressful conditions in vitro. Antibiotic sensitivity was confirmed using Alamar blue MIC determination assays, which showed that ftsEX and ripC had increased sensitivity to chloramphenicol and not to rifampicin, isoniazid and ethambutol. Our growth curve analysis showed that ftsEX and ripC are not essential for survival in normal growth conditions. However, ftsEX and ripC are conditionally essential for M. smegmatis in low salt media. Growth defects in this condition were characterized by short and bulgy cells, as well as elongated filamentous cells with visible chaining. Major morphological changes were seen under nitrosative stress. A higher proportion of cells struggled to divide normally and formed chains. Lateral branching was also observed in ΔftsE, ΔftsX and ΔftsEX but not in ΔripC. The protein complex was also required for survival in media containing rifampicin. Treatment with the drug exacerbated growth defects of all the mutants, which were much shorter than WT cells, indicating impairment in the elongation process. Collectively, mutants are much shorter in length with an exception of a few extremely lengthy cells, suggesting that ftsEX and ripC are required for both normal cell elongation and division and ultimately for survival in stressful conditions.
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    Investigation of the potential of Spleen Tyrosine Kinase (SYK) as a target for host-directed therapy during mycobacterial infection in macrophages
    (2022) Mohapi, Sephekana Samuel; Marakalala, Mohlopheni Jackson; Ndlovu, Hlumani
    Tuberculosis (TB) is a communicable disease caused by a single infectious agent, Mycobacterium tuberculosis (Mtb). TB affects mostly the lungs and despite treatment being available, it still causes long term functional disability due to collateral tissue damage. The TBburden is exacerbated by the lengthy treatment period of 6-12 months which may result in issues of toxicity and poor adherence. Novel therapeutics are therefore urgently needed. Host directed therapies (HDT) are currently a promising way forward for limiting tissue pathology caused by Mtb. Spleen tyrosine kinase (SYK) plays an important role in innate immune signalling. It is expressed on innate immune cells such as macrophages. Macrophages play a critical role in thepathophysiology of TB. They are the first responders to Mtb infection and are phagocytic cells that engulf and destroy Mtb. They also produce inflammatory cytokines such as TNF and IL- 1β. Recent studies have suggested an involvement of SYK in the inflammatory signalling cascade linked to necrotic and caseous regions of granulomas of TB patients. However, it is unclear what role SYK plays in the pathophysiology of TB and whether its inhibition would result in resolution of excessive tissue damage in the lungs. Our study is based on an in vitro infection model of Thp-1 derived macrophages. We differentiated Thp-1 monocytes into macrophages and infected them with BCG or the pathogenic laboratory strain Mtb H37Rv. We then treated infected macrophages with SYK inhibitors; Fostamatinib and Piceatennol, collected supernatants and analyzed cytokine production using enzyme-linked immunosorbent assay (ELISA). Moreover, we also evaluatedwhether SYK inhibition with Fostamatinib or Piceatennol might affect the intracellular survival of Mtb in macrophages. We also attempted to confirm the reduced expression of SYK at geneand protein level after treating infected cells with Fostamatinib. Our data showed that Fostamatinib reduced the production of inflammatory cytokines IL-6, IL- 1β and TNF- in macrophages infected with BCG. Similarly, these findings were also observedin macrophages that were infected with Mtb H37Rv, with the exception of IL-1β that was unaltered in macrophages treated with Fostamatinib. Moreover, Fostamatinib reduced the production of anti-inflammatory cytokine IL-10 and the chemokine monocyte chemotactic protein-1 (MCP-1) in macrophages infected with Mtb H37Rv. We observed that Fostamatinibrescued macrophages from cell death induced by both BCG and Mtb H37Rv. Finally, we showed that treatment with Fostamatinib also reduced bacterial loads inside macrophages. In essence, our study showed that SYK inhibition attenuate Mtb induced inflammatory profile in macrophages and aids in macrophage anti-mycobacterial effects. Further, it suggests that SYK inhibition might be an attractive avenue to explore further as a potential host-directed therapy for TB.
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    The role of Cysteinyl leukotriene receptor-1 during experimental helminth infections in murine model
    (2021) Mosala, Paballo Pertunia; Brombacher, Frank; Ndlovu, Hlumani
    Cysteinyl leukotrienes (cysLTs) are potent inflammatory lipid mediators that play a major role in the pathophysiology of inflammatory diseases. They signal primarily through cysteinyl leukotriene receptor-1 (cysLTR1) and have been reported to drive Th2 immune responses. Initiation and amplification of robust Th2 immune responses is crucial for conferring protective immunity to helminth (Schistosoma mansoni and Nippostrongylus brasiliensis) infection in mice. The role played by cysLTs in the development of protective immune responses to helminth infections is not well documented. Hence in the present study, we investigated the role of cysLTs during helminth infection using cysteinyl leukotriene receptor-1 deficient (cysLTR1-/- ) mice. Under steady state conditions, young naïve cysLTR1-/- mice did not reveal any significant alteration of the cellular, tissue and phenotypic profile although we did observe expansion of central memory T cells (Tcm) in secondary lymphoid organs in cysLTR1-/- as compared to wildtype mice. Primary infection with N. brasiliensis indicated increased worm burden in cysLTR1-/- mice at day 7 post infection and a delay in the resolution of infection by day 9 post infection when compared to wild type mice. Furthermore, we observed reduced Th2 immune responses as well as impaired contractility of the small intestine, which are key features required for protective immunity to N. brasiliensis infection. Furthermore, recall of memory responses to N. brasiliensis was abrogated in cysLTR1 -/- mice, with higher numbers of adult worms recovered at day 5 post re-infection in cysLTR1-/- mice comparison with wild type mice. Additionally, cysLTR1-/- mice exhibited impaired production of IL-13 in the lungs and draining lymph nodes compared with wildtype mice. Finally, there was reduced recruitment of effector CD4+ T cells and central memory CD4+ T cells in the lungs of cysLTR1 deficient mice compared to control mice. Taken together, these data demonstrated an essential role played by cysLTR1 in clearance and resolution of N. brasiliensis infection. CysLTR1-/- mice survived acute S. mansoni infection similarly to wildtype mice. In addition, cysLTR1-/- mice displayed reduced granulomatous inflammation and reduced cellular responses in the liver compared with wildtype mice. Further analysis revealed reduced gut fibrosis but cytokine production, immune cell recruitment in the gut and both type 1 and type 2 antibodies were found to be comparable between wildtype and knockout mice, demonstrating that cysLTs signaling through cysLTR1 contribute to granuloma formation in the liver. Similar to acute schistosomiasis, cysLTR1-/- mice were not susceptible to chronic schistosomiasis and indicated by prolonged host survival. This increased host survival observed in cysLTR1-/- mice was associated with reduced granulomatous inflammation, reduced fibrosis and hepatocellular damage, impaired production of IL-4 in the liver, and reduced intracellular secretion of IL4 by CD4+ T cells and ILC2s in cysLTR1-/- mice compared with wildtype mice. Furthermore, we observed reduced granulomatous inflammation in the lungs of chronically infected cysLTR1-/- mice despite the heightened Th2 immune response in the lungs. Collectively, these data revealed that disruption of cysLTR1 leads to reduced granulomatous inflammation and reduced production of IL-4 in the liver during chronic schistosomiasis. In conclusion, the current study demonstrated both positive and negative roles for cysLTs signaling through cysLTR1 during different helminth infection models. Absence of cysLTR1 during N. brasiliensis leads to delayed expulsion of adult worms and impaired recall of memory responses, indicating that cysteinyl leukotriene signaling via cysLTR1 is essential for orchestrating host protective responses. On the other hand, signaling via cysLTR1 appears to be dispensable for the development of host protective responses during acute schistosomiasis in mice. However, mice deficient of cysLTR1 had reduced liver pathology during chronic schistosomiasis, suggesting that inhibition of this receptor could be a potential therapy for reducing granulomatous liver pathology.