The Role of Vhl in T cell mediated control of Mtb infection
(2020) MOBN03 20192Degree Projects in Molecular Biology
- Abstract
- Development of a successful prophylactic or therapeutic treatment for active Tuberculosis (TB) has been hampered by the bacilli’s ability to evade, tolerate, subvert host immunity and persist in a hypoxic intracellular niche. Upon infection with M. tuberculosis (Mtb), there is an increased demand for metabolites by cells to respond to the robust immune activation, which is met with a shift of metabolism to high energy yielding aerobic glycolysis among other changes. A master regulator of metabolic changes is the Hypoxia Inducible Factor-1 (HIF-1) transcription factor, which is negatively regulated by Von-hippel Lindau factor (VHL). In this study, we address the role of VHL and HIF-1 in T cell mediated control of Mtb infection using a mouse... (More)
- Development of a successful prophylactic or therapeutic treatment for active Tuberculosis (TB) has been hampered by the bacilli’s ability to evade, tolerate, subvert host immunity and persist in a hypoxic intracellular niche. Upon infection with M. tuberculosis (Mtb), there is an increased demand for metabolites by cells to respond to the robust immune activation, which is met with a shift of metabolism to high energy yielding aerobic glycolysis among other changes. A master regulator of metabolic changes is the Hypoxia Inducible Factor-1 (HIF-1) transcription factor, which is negatively regulated by Von-hippel Lindau factor (VHL). In this study, we address the role of VHL and HIF-1 in T cell mediated control of Mtb infection using a mouse model where Vhl and Hif1a were conditionally knocked out using loxP-CRE system. We observed increased bacterial levels in the lung and spleen of Vhlfl/flCd4 CRE+ mice 6- and 8-weeks after-aerosol Mtb infection. CD4 T cells were reduced in the lungs of infected mutant mice compared to WT. Mtb specific TB10.4+CD8 T cells and ESAT-6+CD4 T cells were found to be diminished in Vhlfl/flCd4 CRE+ mice. We also showed that IFN-γ specific effector responses after stimulation with peptides TB10.4(4-11) and ESAT-6(1-15) were compromised in Vhlfl/flCd4 CRE+ mice. We observed a consistent decrease in frequency of FoxP3 expressing CD4 Tregs in the lung, spleen, and lymph node of infected mutant mice in comparison to WT mice. Instead, hif1a fl/fl dlck cre showed no alterations in T cell frequencies or the outcome of infection as compared with WT-infected controls. These results were in line with in-vitro stimulation of total and isolated naïve CD4 T cells from mutant and wild type animals. We demonstrated impaired frequencies of IL-17 secretion by T cells derived from Vhlfl/flCd4 CRE+ in an uninfected model. As predicted, cells derived from Vhlfl/flCd4 CRE+ showed diminished proliferation and increased levels of apoptosis than controls. We summarize that Vhl, but not Hif1α, in T cells is critical for T cell-mediated control of Mtb infection and, in general, favor the idea that these immunometabolic shifts dictate downstream signaling events and fate of T cell activation program. (Less)
- Popular Abstract
- Tuberculosis (TB), caused by the bacterium Mycobacterium tuberculosis (Mtb) is one of the deadliest diseases (along with COVID-19) due to which every year around 1.5 million people die in the modern world. Typically, the bacterium spreads through air and as a person inhales, it enters the lung via airways and resides there. The bacteria form characteristic lesions in the lung known as granuloma from which they could actively move to different parts of the body and perhaps even infect other individuals. Our body has specialized cells called immune cells that surround the bacteria at this local site and contain them. For instance, macrophages are a type of immune cell that detect and internalize Mtb. These macrophages that contain Mtb are... (More)
- Tuberculosis (TB), caused by the bacterium Mycobacterium tuberculosis (Mtb) is one of the deadliest diseases (along with COVID-19) due to which every year around 1.5 million people die in the modern world. Typically, the bacterium spreads through air and as a person inhales, it enters the lung via airways and resides there. The bacteria form characteristic lesions in the lung known as granuloma from which they could actively move to different parts of the body and perhaps even infect other individuals. Our body has specialized cells called immune cells that surround the bacteria at this local site and contain them. For instance, macrophages are a type of immune cell that detect and internalize Mtb. These macrophages that contain Mtb are then helped by other specialized cells called T cells, which initiate killing. However, Mtb evades these robust host immune responses and persists within the host in ways that are not well characterized.
Because of the formation of a rigid, complex granuloma, the cells in this tissue become tightly packed and thus are not supplied with enough oxygen for their regular cellular activities. Fortunately, our cells happen to have a protein called as HIF, which helps them to survive when in oxygen deprivation. HIF is degraded by another protein called VHL when there is enough oxygen for the cells. Based on observations, we predicted that VHL is essential for immune cells to kill Mtb effectively, and without VHL the disease progression is much severe.
To test this theory, we used mice models in which we deleted VHL and HIF separately using genetic tools and infected them with Mtb. We used an experiment known as flow cytometry staining and analysis to detect the immune cells in the tissues derived from the mice. This is done using specific fluorescent markers which when attaches to the cell of choice emits a particular color which is then read by the flow cytometer instrument. By this we would know the exact percentages of immune subsets in the tissues. In our study we show that the mice that lack VHL had high levels of bacteria in the lung together with poor levels of T cells, which are essential in killing the bacteria. We also found that immune cells that do not have VHL are more prone to enter a self-destruct program than cells that have VHL. The proliferative capacity of immune cells that lacked VHL was compromised consistent with our other results.
Our study results stand as novel findings showing the importance of VHL in controlling Mtb infection and contributes to better understanding of host-pathogen interaction. With a rise of infectious diseases every year, our study could pave way for prophylactic and therapeutic interventions to such deadly infectious diseases. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9029325
- author
- Venkita Subramani, Mahadevan
- supervisor
- organization
- course
- MOBN03 20192
- year
- 2020
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9029325
- date added to LUP
- 2020-09-15 11:57:04
- date last changed
- 2020-09-15 11:57:04
@misc{9029325,
abstract = {{Development of a successful prophylactic or therapeutic treatment for active Tuberculosis (TB) has been hampered by the bacilli’s ability to evade, tolerate, subvert host immunity and persist in a hypoxic intracellular niche. Upon infection with M. tuberculosis (Mtb), there is an increased demand for metabolites by cells to respond to the robust immune activation, which is met with a shift of metabolism to high energy yielding aerobic glycolysis among other changes. A master regulator of metabolic changes is the Hypoxia Inducible Factor-1 (HIF-1) transcription factor, which is negatively regulated by Von-hippel Lindau factor (VHL). In this study, we address the role of VHL and HIF-1 in T cell mediated control of Mtb infection using a mouse model where Vhl and Hif1a were conditionally knocked out using loxP-CRE system. We observed increased bacterial levels in the lung and spleen of Vhlfl/flCd4 CRE+ mice 6- and 8-weeks after-aerosol Mtb infection. CD4 T cells were reduced in the lungs of infected mutant mice compared to WT. Mtb specific TB10.4+CD8 T cells and ESAT-6+CD4 T cells were found to be diminished in Vhlfl/flCd4 CRE+ mice. We also showed that IFN-γ specific effector responses after stimulation with peptides TB10.4(4-11) and ESAT-6(1-15) were compromised in Vhlfl/flCd4 CRE+ mice. We observed a consistent decrease in frequency of FoxP3 expressing CD4 Tregs in the lung, spleen, and lymph node of infected mutant mice in comparison to WT mice. Instead, hif1a fl/fl dlck cre showed no alterations in T cell frequencies or the outcome of infection as compared with WT-infected controls. These results were in line with in-vitro stimulation of total and isolated naïve CD4 T cells from mutant and wild type animals. We demonstrated impaired frequencies of IL-17 secretion by T cells derived from Vhlfl/flCd4 CRE+ in an uninfected model. As predicted, cells derived from Vhlfl/flCd4 CRE+ showed diminished proliferation and increased levels of apoptosis than controls. We summarize that Vhl, but not Hif1α, in T cells is critical for T cell-mediated control of Mtb infection and, in general, favor the idea that these immunometabolic shifts dictate downstream signaling events and fate of T cell activation program.}},
author = {{Venkita Subramani, Mahadevan}},
language = {{eng}},
note = {{Student Paper}},
title = {{The Role of Vhl in T cell mediated control of Mtb infection}},
year = {{2020}},
}