Periodic Reporting for period 1 - GammaDelta (DECIPHERING THE MEMORY OF gd T CELLS: DOES IT HAVE A ROLE IN CROSS-PROTECTION OF BACILLE CALMETTE-GUERIN VACCINATION?)
Periodo di rendicontazione: 2018-05-03 al 2020-05-02
Recent events of SARS-Cov2 pandemic, which has claimed life of over 500 000 people worldwide within only half a year (according to Johns Hopkins Coronavirus Resource Center) and is still accelerating, have shown how threatening the infectious diseases can be in the era of globalization and how important it is to develop effective vaccination strategies. The efficacy of vaccines relies on the ability of immune cells to “memorize” previous invaders and in consequence to respond more efficiently to the secondary exposure to the pathogen. This phenomenon is called immunological memory. While vaccines are designed to protect against a specific pathogen, it has been shown that some of them have a cross-protective effect, meaning that they can protect against non-targeted infections. One example of a vaccine with known heterologous effects is bacillus Calmette-Guerin (BCG) vaccine developed to protect against tuberculosis caused by Mycobacterium tuberculosis. Based on its potency to enhance immune responses towards various pathogens and the urgency to combat SARS-Cov2 pandemic, clinical trials are currently ongoing to evaluate its protective effects against SARS-Cov2 infection. The molecular basis of cross-protective effect can be explained by, among others, “trained immunity”. Trained immunity is the ability of innate immune cells (such as macrophages or natural killer cells) to “remember” primary stimulations (for example by BCG) and to respond more effectively to the secondary challenge, thus generating memory-like immune responses. While the immune memory has been for decades attributed solely to the adaptive immune cells (B and T cells) and is known to be antigen-specific, trained immunity has been described recently and is not antigen-specific. Therefore it can be cross-protective. It has been established that cells of the adaptive immune system develop immunological memory and some cells of the innate immune system develop trained immunity. Yet, it remains to be determined what kind of immune memory: adaptive or innate-like characterizes immune cells which share features of both: adaptive and innate immune cells and what is their contribution to immune memory responses?
This project aimed to assess the memory character of innate-like T cells, called gamma delta (gd) T cells, and its contribution to the immune memory responses upon BCG vaccination. gd T cells are classified as adaptive immune cells based on the expression of T cell receptor (TCR), similarly to conventional alpha beta (ab) T cells. However their immune responses are of innate character: not pathogen-specific and fast. BCG vaccination has been shown to generate memory gd T cells however their memory character was only assessed in a pathogen-specific context. In this study we examined the gd T cell immune responses to heterologous stimuli and show that despite the innate character, gd T cells do not develop trained immunity therefore they can only account for pathogen-specific memory responses.
This project aimed to assess the memory character of innate-like T cells, called gamma delta (gd) T cells, and its contribution to the immune memory responses upon BCG vaccination. gd T cells are classified as adaptive immune cells based on the expression of T cell receptor (TCR), similarly to conventional alpha beta (ab) T cells. However their immune responses are of innate character: not pathogen-specific and fast. BCG vaccination has been shown to generate memory gd T cells however their memory character was only assessed in a pathogen-specific context. In this study we examined the gd T cell immune responses to heterologous stimuli and show that despite the innate character, gd T cells do not develop trained immunity therefore they can only account for pathogen-specific memory responses.
In order to determine the memory character of gd T cells we first attempted to establish in vitro gd T cell memory formation assays using various stimulating agents. Immune memory responses of gd T cells in adult peripheral blood mononuclear cells (PBMCs) cultures as well as cord blood PBMCs were assessed based on activation status, cytokine produced, proliferative and cytotoxic activities. We observed a huge variability between healthy donors in terms of gd T cell responses to stimulation and indicating that gd T cells in some donors may develop trained immunity. To further investigate this observation we determined the formation of trained immunity by gd T cells in vivo. In order to address this question we took a part in a clinical trial performed at the Radboud University Medical Center in Nijmegen, Netherlands, where healthy volunteers were vaccinated with BCG. We looked at gd T cell memory responses to heterologous challenges before and weeks after vaccination. We found that gd T cell responses to infectious agents in terms of cytokine production were not enhanced by BCG vaccination. Therefore we concluded that human circulating gd T cells do not develop trained immunity and therefore do not contribute to the cross-protective effect of vaccines.
We did observe however a distinct cytokine production profile and therefore functional responses of gd T cell when PBMC cultures were incubated with different stimuli. For example primary stimulation with phosphoantigen results in functionally potent gd T cells upon restimulation while zolendronic acid stimulation results in compromised cytokine production by gd T cell upon rechallange indicating that the primary stimuli generate functionally different gd T cells. We are currently investigating epigenetic landscape of differentially challenged gd T cells at genome-wide scale using next generation sequencing based technologies.
The project was conveyed to the Life and Medical Sciences Institute (LIMES) members in the interview as well as a short article for the internal magazine LIMES Klaaf. Furthermore, the project was communicated to the broader public in a blog article “Marie Curie and her actions”, which was awarded the “IITB travel grant 3: Blog support”, at the Young Investigator’s Science Blog of the ImmunoSensation Cluster of Excellence. The results were disseminated in a form of poster on several scientific national and international conferences including: The New Frontiers in Innate Immunity and Inflammation 2018 in Cluj-Napoca, Romania, ImmunoSensation Days 2019 in Bonn, Germany as well as on The 4th International Trained Immunity Conference 2019 in Nijmegen, the Netherlands. The preliminary results of the project were also announced during an invited seminar “From epigenetics of alpha beta T cells to the memory of gamma delta T cells” by the Women in Science Committee of the LIMES institute as well as informal retreat of research groups focused on innate immune cell biology. The fellowship resulted in three review articles shared with coauthors and published in peer-reviewed journals:
1. Netea MG, Schlitzer A, Placek K, Joosten LAB, Schultze LS (2019) ‘Innate and adaptive immune memory: an evolutionary continuum.’ Cell Host Microbe 25: 13-26.
2. Placek K, Schultze LS, Netea MG (2019) ‘Immune memory characteristics of innate lymphoid cells.’ Curr Opin Infect Dis 32: 196-203.
3. Placek K, Schultze LS, Aschenbrenner AC (2019) ‘Epigenetic reprogramming of immune cells in injury, repair and resolution.’ J Clin Invest 129: 2994-3005.
The results of the project have been submitted to a peer-reviewed journal.
We did observe however a distinct cytokine production profile and therefore functional responses of gd T cell when PBMC cultures were incubated with different stimuli. For example primary stimulation with phosphoantigen results in functionally potent gd T cells upon restimulation while zolendronic acid stimulation results in compromised cytokine production by gd T cell upon rechallange indicating that the primary stimuli generate functionally different gd T cells. We are currently investigating epigenetic landscape of differentially challenged gd T cells at genome-wide scale using next generation sequencing based technologies.
The project was conveyed to the Life and Medical Sciences Institute (LIMES) members in the interview as well as a short article for the internal magazine LIMES Klaaf. Furthermore, the project was communicated to the broader public in a blog article “Marie Curie and her actions”, which was awarded the “IITB travel grant 3: Blog support”, at the Young Investigator’s Science Blog of the ImmunoSensation Cluster of Excellence. The results were disseminated in a form of poster on several scientific national and international conferences including: The New Frontiers in Innate Immunity and Inflammation 2018 in Cluj-Napoca, Romania, ImmunoSensation Days 2019 in Bonn, Germany as well as on The 4th International Trained Immunity Conference 2019 in Nijmegen, the Netherlands. The preliminary results of the project were also announced during an invited seminar “From epigenetics of alpha beta T cells to the memory of gamma delta T cells” by the Women in Science Committee of the LIMES institute as well as informal retreat of research groups focused on innate immune cell biology. The fellowship resulted in three review articles shared with coauthors and published in peer-reviewed journals:
1. Netea MG, Schlitzer A, Placek K, Joosten LAB, Schultze LS (2019) ‘Innate and adaptive immune memory: an evolutionary continuum.’ Cell Host Microbe 25: 13-26.
2. Placek K, Schultze LS, Netea MG (2019) ‘Immune memory characteristics of innate lymphoid cells.’ Curr Opin Infect Dis 32: 196-203.
3. Placek K, Schultze LS, Aschenbrenner AC (2019) ‘Epigenetic reprogramming of immune cells in injury, repair and resolution.’ J Clin Invest 129: 2994-3005.
The results of the project have been submitted to a peer-reviewed journal.
It has been known for decades that BCG vaccine induces memory gd T cells and can protect from other infectious diseases than tuberculosis. However the role of gd T cells in the cross-protection of BCG has not been addressed so far. Our observations indicate that gd T cells do not develop trained immunity, a feature has not reported so far. The results of the project are of importance for the vaccine design and use. For example, targeting gd T cell memory formation might be not of importance for the development of vaccines with cross-protective effects but might be beneficial for the development of pathogen-specific vaccines.