Microbiology & Immunology - Research Publications
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ItemDevelopment of Plasmodium-specific liver-resident memory CD8+ T cells after heat-killed sporozoite immunization in mice(WILEY, 2021-05)Malaria remains a major cause of mortality in the world and an efficient vaccine is the best chance of reducing the disease burden. Vaccination strategies for the liver stage of disease that utilise injection of live radiation-attenuated sporozoites (RAS) confer sterile immunity, which is mediated by CD8+ memory T cells, with liver-resident memory T cells (TRM ) being particularly important. We have previously described a TCR transgenic mouse, termed PbT-I, where all CD8+ T cells recognize a specific peptide from Plasmodium. PbT-I form liver TRM cells upon RAS injection and are capable of protecting mice against challenge infection. Here, we utilize this transgenic system to examine whether nonliving sporozoites, killed by heat treatment (HKS), could trigger the development of Plasmodium-specific liver TRM cells. We found that HKS vaccination induced the formation of memory CD8+ T cells in the spleen and liver, and importantly, liver TRM cells were fewer in number than that induced by RAS. Crucially, we showed the number of TRM cells was significantly higher when HKS were combined with the glycolipid α-galactosylceramide as an adjuvant. In the future, this work could lead to development of an antimalaria vaccination strategy that does not require live sporozoites, providing greater utility.
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ItemNo Preview AvailableDiscontinuation of nucleot(s)ide analogue therapy in HBeAg-negative chronic hepatitis B: a meta-analysis(BMJ PUBLISHING GROUP, 2022-08)BACKGROUND AND AIMS: Sustained virological suppression and hepatitis B surface antigen (HBsAg) loss have been described after nucleot(s)ide analogue (NA) discontinuation for patients with hepatitis B e antigen (HBeAg)-negative chronic hepatitis B (CHB). We performed a meta-analysis of the clinical outcomes after NA discontinuation for HBeAg-negative CHB. METHODS: Studies involving NA cessation in HBeAg-negative CHB individuals with a median follow-up of ≥12 months were included. Participants were HBeAg-negative at the time of NA initiation. Random effects meta-analyses were performed for the following clinical outcomes: (1) virological relapse (VR) at 6 and 12 months; (2) clinical relapse (CR) at 6 and 12 months and (3) HBsAg loss. Effect of other variables was estimated using subgroup analysis and meta-regression. Studies including patients stopping entecavir (ETV) and/or tenofovir disoproxil fumarate (TDF) were considered separately to studies including patients stopping older generation NA. RESULTS: N=37 studies met inclusion criteria. Cumulative incidence of VR and CR after stopping ETV/TDF was 44% and 17% at 6 months and 63% and 35% at 12 months. Similar relapse rates were observed after stopping older NAs. Among patients stopping ETV/TDF, TDF cessation was associated with increased CR rates at 6 months versus ETV. There was an association between follow-up ≥4 years and HBsAg loss rates when stopping older NAs. Hepatic decompensation and hepatocellular carcinoma were rare but occurred more frequently in studies including cirrhotic individuals. CONCLUSION: VR is common after NA discontinuation, however, CR was only seen in one-third of patients at 12 months. Stopping NA therapy can be followed by HBsAg clearance, and rates are higher with longer follow-up.
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ItemTightly Constrained Genome Reduction and Relaxation of Purifying Selection during Secondary Plastid Endosymbiosis(OXFORD UNIV PRESS, 2022-01-07)Endosymbiosis, the establishment of a former free-living prokaryotic or eukaryotic cell as an organelle inside a host cell, can dramatically alter the genomic architecture of the endosymbiont. Plastids or chloroplasts, the light-harvesting organelle of photosynthetic eukaryotes, are excellent models to study this phenomenon because plastid origin has occurred multiple times in evolution. Here, we investigate the genomic signature of molecular processes acting through secondary plastid endosymbiosis-the origination of a new plastid from a free-living eukaryotic alga. We used phylogenetic comparative methods to study gene loss and changes in selective regimes on plastid genomes, focusing on green algae that have given rise to three independent lineages with secondary plastids (euglenophytes, chlorarachniophytes, and Lepidodinium). Our results show an overall increase in gene loss associated with secondary endosymbiosis, but this loss is tightly constrained by the retention of genes essential for plastid function. The data show that secondary plastids have experienced temporary relaxation of purifying selection during secondary endosymbiosis. However, this process is tightly constrained, with selection relaxed only relative to the background in primary plastids. Purifying selection remains strong in absolute terms even during the endosymbiosis events. Selection intensity rebounds to pre-endosymbiosis levels following endosymbiosis events, demonstrating the changes in selection efficiency during different origin phases of secondary plastids. Independent endosymbiosis events in the euglenophytes, chlorarachniophytes, and Lepidodinium differ in their degree of relaxation of selection, highlighting the different evolutionary contexts of these events. This study reveals the selection-drift interplay during secondary endosymbiosis and evolutionary parallels during organellogenesis.
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ItemHUMAN CLEC9A ANTIBODIES DELIVER NY-ESO-1 ANTIGEN TO CD141+DENDRITIC CELLS TO ACTIVATE NAIVE AND MEMORY NY-ESO-1-SPECIFIC CD8+T CELLS(BMJ PUBLISHING GROUP, 2020-11)Background Dendritic cells (DC) are crucial for the efficacy of cancer vaccines, but current vaccines do not harness the key cDC1 subtype required for effective CD8+ T cell mediated tumor immune responses. Vaccine immunogenicity could be enhanced by specific delivery of immunogenic tumor antigens to CD141+ DC, the human cDC1 equivalent. CD141+ DC exclusively express the C-type-lectin-like receptor CLEC9A, which is important for the regulation of CD8+ T cell responses. This study developed a new vaccine that harnesses a human anti-CLEC9A antibody to specifically deliver the immunogenic tumor antigen, NY-ESO-1 to human CD141+ DC. The ability of the CLEC9A-NY-ESO-1 antibody to activate NY-ESO-1 specific naïve and memory CD8+ T cells was examined and compared to a vaccine comprised of a human DEC-205-NY-ESO-1 antibody that targets all human DC. Methods Human anti-CLEC9A, anti-DEC-205 and isotype control IgG4 antibodies were genetically fused to NY-ESO-1 polypeptide. Cross-presentation to NY-ESO-1- epitope specific CD8+ T cells and reactivity of T cell responses in melanoma patients was assessed by IFNγ production following incubation of CD141+ DC and patient peripheral blood mononuclear cells with targeting antibodies. Humanized mice containing human DC subsets and a repertoire of naïve NY-ESO-1-specific CD8+ T cells were used to investigate naïve T cell priming. T cell effector function was measured by expression of IFNγ, MIP-1β, TNF and CD107a and by lysis of target tumor cells. Results CLEC9A-NY-ESO-1 Ab were effective at mediating delivery and cross-presentation of multiple NY-ESO-1 epitopes by CD141+ DC for activation of NY-ESO-1-specific CD8+ T cells. When benchmarked to NY-ESO-1 conjugated to an untargeted control antibody or to anti-human DEC-205, CLEC9A-NY-ESO-1 was superior at ex vivo reactivation of NY-ESO-1-specific T cell responses in melanoma patients. Moreover, CLEC9A-NY-ESO-1 induced priming of naïve NY-ESO-1-specific CD8+ T cells with polyclonal effector function and potent tumor killing capacity in vitro. Conclusions These data advocate human CLEC9A-NY-ESO-1 antibody as an attractive strategy for specific targeting of CD141+ DC to enhance tumour immunogenicity in NY-ESO-1-expressing malignancies. Ethics Approval Written informed consent was obtained for human sample acquisition in line with standards established by the Declaration of Helsinki. Study approval was granted by the Mater Human Research Ethics Committee (HREC13/MHS/83 and HREC13/MHS/86) and The U.S. Army Medical Research and Materiel Command (USAMRMC) Office of Research Protections, Human Research Protection Office (HRPO; A-18738.1, A-18738.2, A-18738.3). All animal experiments were approved by the University of Queensland Animal Ethics Committee and conducted in accordance with the Australian Code for the Care and Use of Animals for Scientific Purposes in addition to the laws of the United States and regulations of the Department of Agriculture.