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- Andersson, Anna-Maria, 1990-
(författare)
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Mycobacterium tuberculosis and HIV coinfection : Effects on innate immunity and strategies to boost the immune response
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tuberculosis (TB) still remains a big threat today, being the leading cause of death by a single infectious agent. The TB epidemic is fueled by HIV along with the increasing drug-resistance which prolongs the already long treatment duration and decreases the success rate for curing TB. In most cases an infection results in latency but HIV patients have a 20-30 times higher risk of developing active TB. There are around 36.9 million people living with HIV globally, with the highest burden in Africa. Although there are effective treatments against the disease, there is no cure for AIDS and the availability of the lifelong treatment is limited in low-income countries were the burden is highest. HIV infection causes an immunodeficiency characterized by the progressive loss of CD4 T cells which increases the risk of opportunistic infections, and infection by Mycobacterium tuberculosis (Mtb), the causative agent of TB. Mtb spreads through aerosols from one person with active tuberculosis to a healthy person. Upon inhalation the bacteria are phagocytosed by alveolar macrophages that secrete cytokines and chemokines to recruit more cells, such as dendritic cells, macrophages and lymphocytes, leading to the formation of a granuloma. During a single TB infection the bacteria are usually contained within the granuloma, but HIV can disrupt the stable granuloma, causing a rupture and dissemination of Mtb. This inflammatory site is also beneficial to HIV since it promotes replication of the virus within infected cells. HIV and Mtb are two successful intracellular pathogens able to avoid immune defense mechanisms both of the innate and adaptive immunity in order to persist and replicate. Their virulence factors can manipulate or inhibit cell signaling, phagosome maturation, autophagy, ROS production, apoptosis and antigen presentation, to promote survival. Boosting of immune defenses with host-directed therapies (HDT) has been proposed as a treatment strategy against TB, either alone or adjunctive to the current regimen.In this thesis, ways to boost the innate immune responses in Mtb and HIV coinfected macrophages were investigated, along with studies of the effect of HIV on Mtb antigen presentation in coinfected dendritic cells. The initial hypothesis was that autophagy induction through inhibition of mammalian target of rapamycin (mTOR) could suppress Mtb growth in HIV coinfected macrophages. However, during a low grade infection, autophagy induction increased Mtb replication due to a decreased autophagic flux and acidification of Mtb phagosomes. A general autophagic flux was induced, although not localized to the Mtb phagosomes, thus not inducing a xenophagy (autophagy of intracellular pathogens). Other ways of inducing autophagy or boosting the response in coinfected macrophages might be more beneficial and therefore the effect of efferocytosis was investigated. Uptake of apoptotic neutrophils by coinfected macrophages did not induce autophagy but enhanced the control of Mtb by other means. Upon efferocytosis, the macrophages acquired active myeloperoxidase (MPO) from the neutrophils that suppressed Mtb growth. The coinfected macrophages also produced more ROS after efferocytosis. The inhibition of Mtb growth could thus be mediated by MPO and the increased ROS production either directly or indirectly.The possibility to boost the innate immunity could prove to be important during an HIV coinfection, when the adaptive immunity is deficient. In addition to the well-known decline in CD4 T cells during the course of HIV progression, we found that HIV infection of dendritic cells inhibited antigen presentation by suppressing the expression of HLA-DR and co-stimulatory molecules on coinfected dendritic cells. Furthermore, HIV reduced secretion of pro-inflammatory cytokines and suppressed antigen processing through inhibition of autophagy. This impaired antigen presentation in coinfected dendritic cells resulted in a decreased activation and response of Mtb-specific CD4 T cells.In conclusion, this thesis shows how HIV can manipulate antigen presentation in Mtb coinfected dendritic cells and subsequently inhibit the adaptive immune response. It also contributes to insights on how efferocytosis of apoptotic neutrophils can boost the innate immune responses during coinfection. Lastly, autophagy induction through mTOR inhibition does not enhance protection against TB. Induction of autophagy should therefore be handled with care, particularly during HIV coinfection.
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| 2. |
- Persson, Alexander, 1978-, et al.
(författare)
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Mycobacterium tuberculosis-induced apoptotic neutrophils trigger a pro-inflammatory response in macrophages through release of heat shock protein 72, acting in synergy with the bacteria
- 2008
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Ingår i: Microbes and infection. - : elsevier. - 1286-4579 .- 1769-714X. ; 10:3, s. 233-240
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Tidskriftsartikel (refereegranskat)abstract
- Mycobacterium tuberculosis (Mtb) survive inside macrophages by manipulating microbicidal functions such as phago-lysosome fusion, production of reactive oxygen species and nitric oxide, and by rendering macrophages non-responsive to IFN-γ. Mtb-infected lung tissue does however not only contain macrophages, but also significant numbers of infiltrating polymorphonuclear neutrophils (PMN). These are able to phagocytose and kill ingested Mtb, but are short-lived cells that constantly need to be removed from tissues to avoid tissue damage. Phagocytosis of aged or UV-induced apoptotic PMN by macrophages induce an anti-inflammatory response in macrophages. However, in the present study, we show that engulfment of Mtb-induced apoptotic PMN by macrophages initiates secretion of TNF-α from the macrophages, reflecting a pro-inflammatory response. Moreover, Mtb-induced apoptotic PMN up-regulate heat shock proteins 60 and 72 (Hsp60, Hsp72) intracellularly and also release Hsp72 extracellularly. We found that both recombinant Hsp72 and released Hsp72 enhanced the pro-inflammatory response to both Mtb-induced apoptotic PMN and Mtb. This stimulatory effect of the supernatant was abrogated by depleting the Hsp72 with immunoprecipitation. These findings indicate that released Hsp72 from Mtb-infected PMN can trigger macrophage activation during the early stage of Mtb infections, thereby creating a link between innate and adaptive immunity.
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| 3. |
- Verma, Deepti, et al.
(författare)
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Gene polymorphisms in the NALP3 inflammasome are associated with interleukin-1 production and severe inflammation : relation to common inflammatory diseases?
- 2008
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Ingår i: Arthritis and Rheumatism. - New York, NY : John Wiley & Sons. - 0004-3591 .- 1529-0131. ; 58:3, s. 888-894
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: NALP3, ASC, and TUCAN are components of the NALP3 inflammasome, which triggers caspase 1-mediated interleukin-1beta (IL-1beta) release. Activating mutations in the gene encoding NALP3 (NLRP3) have recently been linked to familial periodic fever syndromes. We undertook this study to determine whether a patient with arthritis and antibiotic-resistant fever carried mutations in the genes encoding the NALP3 inflammasome. METHODS: Genetic analysis of NLRP3 and the gene encoding TUCAN (CARD-8) was performed on genomic DNA from the patient and from a population-based collection of DNA (806 subjects). For in vitro studies of IL-1beta production and caspase 1 activity, blood was obtained from the patient at different time points after administration of anakinra, an IL-1 receptor antagonist, as well as from 5 healthy age- and sex-matched control subjects. RESULTS: Mutation analysis of the patient's genes encoding NALP3, ASC, and TUCAN revealed variations in the NLRP3 (Q705K) and CARD-8 (C10X) genes. The allele frequencies of these single-nucleotide polymorphisms (SNPs) in the population were 6.5% and 34%, respectively. The elevated activity of caspase 1 and the high levels of IL-1beta measured in samples from the patient returned to normal levels after treatment with anakinra. CONCLUSION: Our results indicate that the patient's symptoms were due to elevated levels of IL-1beta, since treatment with anakinra effectively abolished the symptoms. The compound SNPs may explain the increased IL-1beta levels and inflammatory symptoms observed, but further studies are needed to reveal a functional relationship. The prevalence of the polymorphisms (4% of the population carry both SNPs) in the general population may suggest a genetic predisposition for common inflammatory disorders.
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