New therapy extends breast cancer survival rate, prevents reoccurrence

Immunology – Functionality of immune cells in early life

  • January 21, 2021

Dendritic cells are a vital component of the innate immune system, which constitutes the body’s first line of defense against infectious agents and tumor cells. Their job is to activate the T-cell arm of the adaptive immune system, which confers specific and long-lasting protection against bacterial and viral infections. Dendritic cells engulf and degrade proteins that signal the presence of invasive pathogens. The resulting fragments (antigens) are displayed on their surfaces. T cells bearing the appropriate receptors are then activated to seek out and eliminate the pathogen. Newborns and young children have fewer dendritic cells than adults, and these juvenile cells also carry fewer antigen-presenting complexes on their surfaces. Based on these observations, immunologists have generally assumed that these cells are functionally immature. However, new work published by a research team led by Professor Barbara Schraml at LMU’s Biomedical Center has shown – using the mouse as a model system – that this assumption is in fact erroneous. Although early dendritic cells differ in their characteristics from those of mature mice, they are nevertheless quite capable of triggering effective immune reactions. The new findings suggest ways of boosting the efficacy of vaccines for young children.

With the help of fluorescent tags attached to specific proteins of interest, Schraml and her colleagues traced the origins and biological properties of dendritic cells in newborn and juvenile mice, and compared them with those of mature animals. These studies revealed that dendritic cells are derived from different source populations, depending on the age of the animal considered. Those found in neonatal animals develop from precursor cells produced in the fetal liver. As the mice get older, these cells are progressively replaced by cells arising from myeloid precursors, a class of white blood cells that originates from the bone marrow. “However, our experiments demonstrate that – in contrast to the conventional view – a particular subtype of dendritic cells named cDC2 cells is able to activate T-cells and express pro-inflammatory cytokines in young animals,” Schraml explains. “In other words, very young mice can indeed trigger immune reactions.”

Nevertheless, early cDC2 cells differ in some respects from those found in adult mice. For example, they show age-dependent differences in the sets of genes they express. It turns out that these differences reflect the fact that the signaling molecules (‘cytokines’) to which dendritic cells respond change as the mice get older. “Among other things, the array of receptors that recognize substances which are specific to pathogens changes with age,” says Schraml. “Another surprise for us was that early dendritic cells activate one specific subtype of T-cells more effectively than others. Interestingly, this subtype has been implicated in the development of inflammatory reactions.”

The results of the study represent a substantial contribution to our understanding of the functions of dendritic cells, and they could have implications for medical immunology. The immune system of newborns differs from that of more mature individuals insofar as immune responses in early life tend to be weaker than those invoked later in life. “Our data suggest that it might be possible to enhance the efficacy of vaccinations in childhood by, for example, adapting the properties of the immunizing antigen to the specific capabilities of the juvenile dendritic cells,” says Schraml.

###

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

Researchers develop new technique to more efficiently isolate and identify rare T cells

Putatively immature dendritic cells may induce robust immune responses in young children

  • January 20, 2021

A study by Ludwig-Maximilians-Universitaet (LMU) in Munich researchers shows that putatively immature dendritic cells found in young children are able to induce robust immune responses. The results could lead to improved vaccination protocols.

Dendritic cells are a vital component of the innate immune system, which constitutes the body’s first line of defense against infectious agents and tumor cells. Their job is to activate the T-cell arm of the adaptive immune system, which confers specific and long-lasting protection against bacterial and viral infections.

Dendritic cells engulf and degrade proteins that signal the presence of invasive pathogens. The resulting fragments (antigens) are displayed on their surfaces. T cells bearing the appropriate receptors are then activated to seek out and eliminate the pathogen.

Newborns and young children have fewer dendritic cells than adults, and these juvenile cells also carry fewer antigen-presenting complexes on their surfaces. Based on these observations, immunologists have generally assumed that these cells are functionally immature.

However, new work published by a research team led by Professor Barbara Schraml at LMU’s Biomedical Center has shown – using the mouse as a model system – that this assumption is in fact erroneous.

Although early dendritic cells differ in their characteristics from those of mature mice, they are nevertheless quite capable of triggering effective immune reactions. The new findings suggest ways of boosting the efficacy of vaccines for young children.

With the help of fluorescent tags attached to specific proteins of interest, Schraml and her colleagues traced the origins and biological properties of dendritic cells in newborn and juvenile mice and compared them with those of mature animals.

These studies revealed that dendritic cells are derived from different source populations, depending on the age of the animal considered. Those found in neonatal animals develop from precursor cells produced in the fetal liver.

As the mice get older, these cells are progressively replaced by cells arising from myeloid precursors, a class of white blood cells that originates from the bone marrow.

However, our experiments demonstrate that – in contrast to the conventional view – a particular subtype of dendritic cells named cDC2 cells is able to activate T-cells and express pro-inflammatory cytokines in young animals. In other words, very young mice can indeed trigger immune reactions.”


Barbara Schraml, Professor, Biomedical Center, Ludwig-Maximilians-Universitaet Muenchen (LMU)

Nevertheless, early cDC2 cells differ in some respects from those found in adult mice. For example, they show age-dependent differences in the sets of genes they express. It turns out that these differences reflect the fact that the signaling molecules (‘cytokines’) to which dendritic cells respond to change as the mice get older.

“Among other things, the array of receptors that recognize substances which are specific to pathogens changes with age,” says Schraml. “Another surprise for us was that early dendritic cells activate one specific subtype of T-cells more effectively than others. Interestingly, this subtype has been implicated in the development of inflammatory reactions.”

The results of the study represent a substantial contribution to our understanding of the functions of dendritic cells, and they could have implications for medical immunology. The immune system of newborns differs from that of more mature individuals insofar as immune responses in early life tend to be weaker than those invoked later in life.

“Our data suggest that it might be possible to enhance the efficacy of vaccinations in childhood by, for example, adapting the properties of the immunizing antigen to the specific capabilities of the juvenile dendritic cells,” says Schraml.

Source:

Journal reference:

Papaioannou, N. E., et al. (2021) Environmental signals rather than layered ontogeny imprint the function of type 2 conventional dendritic cells in young and adult mice. Nature Communications. doi.org/10.1038/s41467-020-20659-2.

Researchers develop new technique to more efficiently isolate and identify rare T cells

New technique may enable researchers to more efficiently isolate and identify rare T cells

  • January 13, 2021

Scientists from the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA have developed a technique that will enable researchers to more efficiently isolate and identify rare T cells that are capable of targeting viruses, cancer and other diseases.

The approach could increase scientists’ understanding of how these critical immune cells respond to a wide range of illnesses and advance the development of T cell therapies. This includes immunotherapies that aim to boost the function and quantity of cancer or virus-targeting T cells and therapies intended to regulate the activity of T cells that are overactive in autoimmune diseases such as diabetes and multiple sclerosis.

The study, published today in Proceedings of the National Academy of Sciences, describes how the new method, called CLInt-Seq, combines and improves upon existing techniques to collect and genetically sequence rare T cells.

“T cells are critical for protecting the body against both infections and cancers,” said Pavlo Nesterenko, first author of the new paper and a graduate student in the lab of Dr. Owen Witte. “They’re both the effectors and organizers of the body’s adaptive immune response, which means they can be used as therapeutics and studying their dynamics can shed light on overall immune activity.”

T cells stand out from other immune cells because they are equipped with molecules on their surfaces called T-cell receptors that recognize fragments of foreign proteins called antigens.

Our bodies produce millions and millions of T cells per day and each of these cells has its own distinct set of receptors. Every T-cell receptor is capable of recognizing one specific antigen. One T-cell receptor might recognize an antigen from the virus that causes the common cold while another might recognize an antigen from breast cancer, for example.

When a T cell encounters an antigen its receptor recognizes, it springs to action, producing large numbers of copies of itself and instructing other parts of the immune system to attack cells bearing that antigen.

Researchers around the world are exploring methods to collect T cells with receptors targeting cancer or other illnesses like the SARS-CoV-2 virus from patients, expand those cells in the lab and then return this larger population of targeted T cells to patients to boost their immune response.

The problem is that in most populations of cells we have access to, whether it be from peripheral blood or samples taken from other parts of the human body, T cells with receptors of interest are found in very low numbers. Existing methods for capturing and identifying these T cells are labor-intensive and need improvement.”


Dr. Owen Witte, Senior Author and Founding Director, UCLA Broad Stem Cell Research Center

Part of the reason this process is inefficient is that when T cells recognize the antigen for which they have the corresponding receptor, they send out signals that prompt other cells nearby to partially activate.

“These so-called bystander cells are excited by the activity around them, but are not really capable of reacting to the antigen that provoked the immune response,” said Witte, who holds the presidential chair in developmental immunology in the department of microbiology, immunology and molecular genetics and is a member of the UCLA Jonsson Comprehensive Cancer Center.

When researchers attempt to isolate T cells with specific receptors using traditional methods, they end up capturing many of these bystander cells. CLInt-Seq alleviates this problem by incorporating a technique that enables researchers to distinguish T cells with receptors of interest from most bystander cells.

Isolating T cells with specific receptors is only the first step. In order for these isolated cells to be useful, they need to be analyzed using droplet-based mRNA sequencing, also known as Drop-seq, which can measure messenger RNA expression in thousands of individual cells at once.

“Once you know the sequence of a T-cell receptor of interest, you can use that information to develop therapies that either make more of that cell in the case of fighting cancer and viruses or introduce regulatory T cells with this receptor sequence to curb an overactive immune response in a given area,” Nesterenko said.

The process of isolating T cells with specific receptors requires that the cells’ contents are fixed in place using chemicals that form bonds between the proteins inside each cell and their surroundings – this technique is known as cross-linking. Unfortunately, cross-linking degrades the T cells’ RNA, which makes Drop-seq analysis very challenging. CLInt-Seq overcomes this hurdle by utilizing a method of cross-linking that is reversible and thus preserves the T cells’ RNA.

“The innovation of this system is that it combines an improved method that identifies T-cell receptors with more specificity with a chemical adaptation that makes this process compatible with droplet-based mRNA sequencing,” Witte said. “This addresses challenges at the heart of finding T-cell receptors for treating cancer and other diseases as well as viral infections – from acute viruses like the virus that causes COVID-19 to chronic viruses like Epstein Barr or herpes.”

Moving forward, the Witte lab is utilizing this technology to address a number of scientific questions, including identifying T-cell receptors that react to the SARS-CoV-2 virus and developing T-cell therapies for prostate cancer.

Source:

Journal reference:

Nesterenko, P.A., et al. (2021) Droplet-based mRNA sequencing of fixed and permeabilized cells by CLInt-seq allows for antigen-specific TCR cloning. PNAS. doi.org/10.1073/pnas.2021190118.

Natural Killer Cells Could Play Key Role in Fight Against MM

Natural Killer Cells Could Play Key Role in Fight Against MM

  • January 12, 2021

Corresponding author Tony Reiman, MD, of the University of New Brunswick, and colleagues, explained that a wide array of emerging therapies, such as proteasome inhibitors, immunomodulatory drugs, and novel combination therapies, have significantly improved outcomes in patients with MM, but that the high rate of eventual relapse and the heterogeneity of the disease among patients have made it a particularly difficult cancer to fight.

“Additionally, MM is considered a disease of the immune system,” the investigators wrote. “Gradual immune dysregulation and impairment of NK cells, T cells, B cells, and dendritic cells allow malignant plasma cells to escape immunosurveillance.”

Reiman and colleagues proposed that a better understanding of the immune environment of MM could lead to strategies to reengage the immune system to inhibit MM growth. This is where NK cells potentially come into play.

These cells are considered the most active subset of innate lymphoid cells. Their name comes from their ability to target infected and malignant cells without prior sensitization. They cells have both activating and inhibitory receptors (IRs), and their activity is controlled by signals between the receptors.

One strategy for leveraging NKs is to use monoclonal antibodies to target IRs. This approach has shown benefits in other types of cancers, the authors wrote, and there is emerging evidence suggesting it is a viable option in MM as well.

They advocated paying particular attention “to understanding the heterogeneity of ligand expression both within and across patients with MM, the interplay between NK and T cells in response to IR blockade therapy, and how NK-targeted therapy can be combined with existing therapeutic options in MM patients.”

The authors said notable research has been published suggesting a role for several other IRs in MM biology: KIRs, NKG2A, TIGIT, TIM-3, PD-1, and LAG-3.

Of those, Reiman and colleagues singled out KIRs as the “most promising” target.“Not only were anti-KIR antibodies shown to be well tolerated, but they were also shown to enhance NK cell function,” they wrote.

Some of those IRs are also expressed on T cells, meaning therapies that target those receptors might boost the anticancer effects of both types of cells; however, the authors said most studies into the IRs have focused almost exclusively on T cells while ignoring NK cells.

Early failure of some clinical trials of IR blockades is likely due to intra- and interpatient heterogeneity, the authors noted. Any kind of IR-blockade therapy would likely need to be tailored to each particular patient’s expression of receptors, the investigators said, similar to what is done in solid tumors.

The investigators closed with a list of key steps they believe will need to be undertaken to bring NK-based therapy for MM close to fruition. Among those steps:

  • Profile NK cell receptors, subpopulations, cell activity, and cell function in MM
  • Profile the expression of NK cell receptor cognate ligands
  • Explore the integration of NK cell–based therapies and traditional therapies preclinically in order to optimize clinical trial design.

Reference

Alfarra H, Weir J, Grieve S, Reiman T. Targeting NK cell inhibitory receptors for precision multiple myeloma immunotherapy. Front Immunol. Published online November 12, 2020. doi:10.3389/fimmu.2020.575609

Researchers develop new technique to more efficiently isolate and identify rare T cells

Researchers develop new technique to more efficiently isolate and identify rare T cells

  • January 12, 2021

Scientists from the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA have developed a technique that will enable researchers to more efficiently isolate and identify rare T cells that are capable of targeting viruses, cancer and other diseases.

The approach could increase scientists’ understanding of how these critical immune cells respond to a wide range of illnesses and advance the development of T cell therapies. This includes immunotherapies that aim to boost the function and quantity of cancer or virus-targeting T cells and therapies intended to regulate the activity of T cells that are overactive in autoimmune diseases such as diabetes and multiple sclerosis.

The study, published today in Proceedings of the National Academy of Sciences, describes how the new method, called CLInt-Seq, combines and improves upon existing techniques to collect and genetically sequence rare T cells.

“T cells are critical for protecting the body against both infections and cancers,” said Pavlo Nesterenko, first author of the new paper and a graduate student in the lab of Dr. Owen Witte. “They’re both the effectors and organizers of the body’s adaptive immune response, which means they can be used as therapeutics and studying their dynamics can shed light on overall immune activity.”

T cells stand out from other immune cells because they are equipped with molecules on their surfaces called T-cell receptors that recognize fragments of foreign proteins called antigens.

Our bodies produce millions and millions of T cells per day and each of these cells has its own distinct set of receptors. Every T-cell receptor is capable of recognizing one specific antigen. One T-cell receptor might recognize an antigen from the virus that causes the common cold while another might recognize an antigen from breast cancer, for example.

When a T cell encounters an antigen its receptor recognizes, it springs to action, producing large numbers of copies of itself and instructing other parts of the immune system to attack cells bearing that antigen.

Researchers around the world are exploring methods to collect T cells with receptors targeting cancer or other illnesses like the SARS-CoV-2 virus from patients, expand those cells in the lab and then return this larger population of targeted T cells to patients to boost their immune response.

The problem is that in most populations of cells we have access to, whether it be from peripheral blood or samples taken from other parts of the human body, T cells with receptors of interest are found in very low numbers. Existing methods for capturing and identifying these T cells are labor-intensive and need improvement.”


Dr. Owen Witte, Study Senior Author and Founding Director, Broad Stem Cell Research Center, University of California, Los Angeles

Part of the reason this process is inefficient is that when T cells recognize the antigen for which they have the corresponding receptor, they send out signals that prompt other cells nearby to partially activate.

“These so-called bystander cells are excited by the activity around them, but are not really capable of reacting to the antigen that provoked the immune response,” said Witte, who holds the presidential chair in developmental immunology in the department of microbiology, immunology and molecular genetics and is a member of the UCLA Jonsson Comprehensive Cancer Center.

When researchers attempt to isolate T cells with specific receptors using traditional methods, they end up capturing many of these bystander cells. CLInt-Seq alleviates this problem by incorporating a technique that enables researchers to distinguish T cells with receptors of interest from most bystander cells.

Isolating T cells with specific receptors is only the first step. In order for these isolated cells to be useful, they need to be analyzed using droplet-based mRNA sequencing, also known as Drop-seq, which can measure messenger RNA expression in thousands of individual cells at once.

“Once you know the sequence of a T-cell receptor of interest, you can use that information to develop therapies that either make more of that cell in the case of fighting cancer and viruses or introduce regulatory T cells with this receptor sequence to curb an overactive immune response in a given area,” Nesterenko said.

The process of isolating T cells with specific receptors requires that the cells’ contents are fixed in place using chemicals that form bonds between the proteins inside each cell and their surroundings – this technique is known as cross-linking. Unfortunately, cross-linking degrades the T cells’ RNA, which makes Drop-seq analysis very challenging. CLInt-Seq overcomes this hurdle by utilizing a method of cross-linking that is reversible and thus preserves the T cells’ RNA.

“The innovation of this system is that it combines an improved method that identifies T-cell receptors with more specificity with a chemical adaptation that makes this process compatible with droplet-based mRNA sequencing,” Witte said. “This addresses challenges at the heart of finding T-cell receptors for treating cancer and other diseases as well as viral infections – from acute viruses like the virus that causes COVID-19 to chronic viruses like Epstein Barr or herpes.”

Source:

Journal reference:

Nesterenko, P.A., et al. (2021) Droplet-based mRNA sequencing of fixed and permeabilized cells by CLInt-seq allows for antigen-specific TCR cloning. Proceedings of the National Academy of Sciences. doi.org/10.1073/pnas.2021190118.

UCLA scientists develop method to more efficiently isolate and identify rare T cells

UCLA scientists develop method to more efficiently isolate and identify rare T cells

  • January 11, 2021

Newswise — Scientists from the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA have developed a technique that will enable researchers to more efficiently isolate and identify rare T cells that are capable of targeting viruses, cancer and other diseases.

The approach could increase scientists’ understanding of how these critical immune cells respond to a wide range of illnesses and advance the development of T cell therapies. This includes immunotherapies that aim to boost the function and quantity of cancer or virus-targeting T cells and therapies intended to regulate the activity of T cells that are overactive in autoimmune diseases such as diabetes and multiple sclerosis.

The study, published today in Proceedings of the National Academy of Sciences, describes how the new method, called CLInt-Seq, combines and improves upon existing techniques to collect and genetically sequence rare T cells.

“T cells are critical for protecting the body against both infections and cancers,” said Pavlo Nesterenko, first author of the new paper and a graduate student in the lab of Dr. Owen Witte. “They’re both the effectors and organizers of the body’s adaptive immune response, which means they can be used as therapeutics and studying their dynamics can shed light on overall immune activity.” 

T cells stand out from other immune cells because they are equipped with molecules on their surfaces called T-cell receptors that recognize fragments of foreign proteins called antigens.

Our bodies produce millions and millions of T cells per day and each of these cells has its own distinct set of receptors. Every T-cell receptor is capable of recognizing one specific antigen. One T-cell receptor might recognize an antigen from the virus that causes the common cold while another might recognize an antigen from breast cancer, for example.

When a T cell encounters an antigen its receptor recognizes, it springs to action, producing large numbers of copies of itself and instructing other parts of the immune system to attack cells bearing that antigen.

Researchers around the world are exploring methods to collect T cells with receptors targeting cancer or other illnesses like the SARS-CoV-2 virus from patients, expand those cells in the lab and then return this larger population of targeted T cells to patients to boost their immune response.

“The problem is that in most populations of cells we have access to, whether it be from peripheral blood or samples taken from other parts of the human body, T cells with receptors of interest are found in very low numbers,” said Witte, senior author of the paper and founding director of the UCLA Broad Stem Cell Research Center. “Existing methods for capturing and identifying these T cells are labor-intensive and need improvement.”

Part of the reason this process is inefficient is that when T cells recognize the antigen for which they have the corresponding receptor, they send out signals that prompt other cells nearby to partially activate.

“These so-called bystander cells are excited by the activity around them, but are not really capable of reacting to the antigen that provoked the immune response,” said Witte, who holds the presidential chair in developmental immunology in the department of microbiology, immunology and molecular genetics and is a member of the UCLA Jonsson Comprehensive Cancer Center.

When researchers attempt to isolate T cells with specific receptors using traditional methods, they end up capturing many of these bystander cells. CLInt-Seq alleviates this problem by incorporating a technique that enables researchers to distinguish T cells with receptors of interest from most bystander cells.

Isolating T cells with specific receptors is only the first step. In order for these isolated cells to be useful, they need to be analyzed using droplet-based mRNA sequencing, also known as Drop-seq, which can measure messenger RNA expression in thousands of individual cells at once.

“Once you know the sequence of a T-cell receptor of interest, you can use that information to develop therapies that either make more of that cell in the case of fighting cancer and viruses or introduce regulatory T cells with this receptor sequence to curb an overactive immune response in a given area,” Nesterenko said. 

The process of  isolating T cells with specific receptors requires that the cells’ contents are fixed in place using chemicals that form bonds between the proteins inside each cell and their surroundings – this technique is known as cross-linking. Unfortunately, cross-linking  degrades the T cells’ RNA, which makes Drop-seq analysis very challenging. CLInt-Seq overcomes this hurdle by utilizing a method of cross-linking that is reversible and thus preserves the T cells’ RNA.

“The innovation of this system is that it combines an improved method that identifies T-cell receptors with more specificity with a chemical adaptation that makes this process compatible with droplet-based mRNA sequencing,” Witte said. “This addresses challenges at the heart of finding T-cell receptors for treating cancer and other diseases as well as viral infections – from acute viruses like the virus that causes COVID-19 to chronic viruses like Epstein Barr or herpes.”

Moving forward, the Witte lab is utilizing this technology to address a number of scientific questions, including identifying T-cell receptors that react to the SARS-CoV-2 virus and developing T-cell therapies for prostate cancer.

This research was funded by the National Cancer Institute, the Parker Institute for Cancer Immunotherapy, a UCLA Tumor Immunology Training Grant and the UCLA Broad Stem Cell Research Center, including support from the Hal Gaba Director’s Fund for Cancer Stem Cell Research.

UCSF researchers discover a new way to control immune system's 'natural killer' cells

UCSF researchers discover a new way to control immune system’s ‘natural killer’ cells

  • January 10, 2021

UC San Francisco scientists have discovered a new way to control the immune system’s “natural killer” (NK) cells, a finding with implications for novel cell therapies and tissue implants that can evade immune rejection. The findings could also be used to enhance the ability of cancer immunotherapies to detect and destroy lurking tumors.

The study, published January 8, 2021 in the Journal of Experimental Medicine, addresses a major challenge for the field of regenerative medicine, said lead author Tobias Deuse, MD, the Julien I.E. Hoffman, MD, Endowed Chair in Cardiac Surgery in the UCSF Department of Surgery.

“As a cardiac surgeon, I would love to put myself out of business by being able to implant healthy cardiac cells to repair heart disease,” said Deuse, who is interim chair and director of minimally invasive cardiac surgery in the Division of Adult Cardiothoracic Surgery. “And there are tremendous hopes to one day have the ability to implant insulin-producing cells in patients with diabetes or to inject cancer patients with immune cells engineered to seek and destroy tumors. The major obstacle is how to do this in a way that avoids immediate rejection by the immune system.”

Deuse and Sonja Schrepfer, MD, PhD, also a professor in the Department of Surgery’s Transplant and Stem Cell Immunobiology Laboratory, study the immunobiology of stem cells. They are world leaders in a growing scientific subfield working to produce “hypoimmune” lab-grown cells and tissues — capable of evading detection and rejection by the immune system. One of the key methods for doing this is to engineer cells with molecular passcodes that activate immune cell “off switches” called immune checkpoints, which normally help prevent the immune system from attacking the body’s own cells and modulate the intensity of immune responses to avoid excess collateral damage.

Schrepfer and Deuse recently used gene modification tools to engineer hypoimmune stem cells in the lab that are effectively invisible to the immune system. Notably, as well as avoiding the body’s learned or “adaptive” immune responses, these cells could also evade the body’s automatic “innate” immune response against potential pathogens.

To achieve this, the researchers adapted a strategy used by cancer cells to keep innate immune cells at bay: They engineered their cells to express significant levels of a protein called CD47, which shuts down certain innate immune cells by avtivating a molecular switch found on these cells, called SIRPα. Their success became part of the founding technology of Sana Biotechnology, Inc, a company co-founded by Schrepfer, who now directs a team developing a platform based on these hypoimmune cells for clinical use.

But the researchers were left with a mystery on their hands — the technique was more successful than predicted. In particular, the field was puzzled that such engineered hypoimmune cells were able to deftly evade detection by NK cells, a type of innate immune cell that isn’t supposed to express a SIRPα checkpoint at all.

NK cells are a type of white blood cell that acts as an immunological first responder, quickly detecting and destroying any cells without proper molecular ID proving they are “self” — native body cells or at least permanent residents — which takes the form of highly individualized molecules called MHC class I (MHC-I).

When MHC-I is artificially knocked out to prevent transplant rejection, the cells become susceptible to accelerated NK cell killing, an immunological rejection that no one in the field had yet succeeded in inhibiting fully. Deuse and Schrepfer’s 2019 data, published in Nature Biotechnology, suggested they might have stumbled upon an off switch that could be used for that purpose.

All the literature said that NK cells don’t have this checkpoint, but when we looked at cells from human patients in the lab we found SIRPα there, clear as day. We can clearly demonstrate that stem cells we engineer to overexpress CD47 are able to shut down NK cells through this pathway.”


Sonja Schrepfer, MD, PhD, Professor, Department of Surgery’s Transplant and Stem Cell Immunobiology Laboratory

To explore their data, Deuse and Schrepfer approached Lewis Lanier, PhD, a world expert in NK cell biology. At first Lanier was sure there must be some mistake, because several groups had looked for SIRPα in NK cells already and it wasn’t there. But Schrepfer was confident in her team’s data.

“Finally it hit me,” Schrepfer said. “Most studies looking for checkpoints in NK cells were done in immortalized lab-grown cell lines, but we were studying primary cells directly from human patients. I knew that must be the difference.”

Further examination revealed that NK cells only begin to express SIRPα after they are activated by certain immune signaling molecules called cytokines. As a result, the researchers realized, this inducible immune checkpoint comes into effect only in already inflammatory environments and likely functions to modulate the intensity of NK cells’ attack on cells without proper MHC class I identification.

“NK cells have been a major barrier to the field’s growing interest in developing universal cell therapy products that can be transplanted “off the shelf” without rejection, so these results are extremely promising,” said Lanier, chair and J. Michael Bishop Distinguished Professor in the Department of Microbiology and Immunology.

In collaboration with Lanier, Deuse and Schrepfer comprehensively documented how CD47-expressing cells can silence NK cells via SIRPα. While other approaches can silence some NK cells, this was the first time anyone has been able to inhibit them completely. Notably, the team found that NK cells’ sensitivity to inhibition by CD47 is highly species-specific, in line with its function in distinguishing “self” from potentially dangerous “other”.

As a demonstration of this principle, the team engineered adult human stem cells with the rhesus macaque version of CD47, then implanted them into rhesus monkeys, where they successfully activated SIRPα in the monkeys’ NK cells, and avoided killing the transplanted human cells. In the future the same procedure could be performed in reverse, expressing human CD47 in pig cardiac cells, for instance, to prevent them from activating NK cells when transplanted into human patients.

“Currently engineered CAR T cell therapies for cancer and fledgling forms of regenerative medicine all rely on being able to extract cells from the patient, modify them in the lab, and then put them back in the patient. This avoids rejection of foreign cells, but is extremely laborious and expensive,” Schrepfer said. “Our goal in establishing a hypoimmune cell platform is to create off-the shelf products that can be used to treat disease in all patients everywhere.”

The findings could also have implications for cancer immunotherapy, as a way of boosting existing therapies that attempt to overcoming the immune checkpoints cancers use to evade immune detection. “Many tumors have low levels of self-identifying MHC-I protein and some compensate by overexpressing CD47 to keep immune cells at bay,” said Lanier, who is director of the Parker Institute for Cancer Immunotherapy at the UCSF Helen Diller Family Comprehensive Cancer Center. “This might be the sweet spot for antibody therapies that target CD47.”

Scientists gain new insight into how the immune system can be better used to destroy cancer cells

Scientists gain new insight into how the immune system can be better used to destroy cancer cells

  • January 10, 2021

Scientists at the University of Southampton’s Centre for Cancer Immunology have gained new insight into how the immune system can be better used to find and kill cancer cells.

Working with BioInvent International, a team led by Professor Mark Cragg and Dr Jane Willoughby from the Antibody and Vaccine Group, based at the Centre, have shown that antibodies, designed to target the molecule OX40, give a more active immune response when they bind closer to the cell membrane and can be modified to attack cancer in different ways.

OX40 is a ‘co-receptor’ that helps to stimulate the production of helper and killer T-cells during an immune response. One of the ways cancer avoids detection is by suppressing immune responses to stop functional tumour specific T-cells from being produced.

In the study, which has been published in Journal for ImmunoTherapy of Cancer, the team also discovered that switching the antibody’s isotype (the part of the antibody that engages with cells of the immune system) could change the way the antibody worked.

When the mIgG2a isotype was used, the antibody could delete cells called Treg cells which are suppressive in the immune system. When the mIgG1 isotype was present, the antibody could stimulate killer T-cells to increase and therefore kill more cancer cells.

Clinical trials with anti-OX40 antibodies have shown that the body can tolerate these drugs but unfortunately have also shown disappointing clinical responses. We need to understand why this is.


This new data shows us that when there is a cancer with lots of Tregs we could use the equivalent of the m2IgGa isotype and in patients where we feel we need better cytotoxic T cells we could use the equivalent of a mIgG1 isotype to boost the immune response. This information is important for developing the next generation of OX40 antibodies that we hope will be more effective in treating patients with cancer.”


Mark Cragg, Professor, University of Southampton

Source:

Journal reference:

Griffiths, J., et al. (2020) Domain binding and isotype dictate the activity of anti-human OX40 antibodies. Journal for ImmunoTherapy of Cancer. doi.org/10.1136/jitc-2020-001557.

Engineered stem cells that evade immune detection could boost cell therapy and I-O

Engineered stem cells that evade immune detection could boost cell therapy and I-O

  • January 8, 2021

Sana Biotechnology was founded in 2018 with a mission of solving some of the most difficult challenges in gene and cell therapy. Toward that end, the company is engineering “hypoimmune stem cells” that can evade detection and destruction by the immune system.

Now, some of Sana’s founders, who are scientists at the University of California, San Francisco (UCSF), are describing how these engineered stem cells are able to shut down the immune system’s natural killer (NK) cells. They believe their findings could enhance the development of implantable cell therapies, as well as cancer immunotherapies, they reported in the Journal of Experimental Medicine.

The ability to evade NK cells could enhance a range of experimental treatments, including implants of insulin-producing cells for patients with diabetes and cardiac cells to repair heart damage. These cells are typically rejected by the immune system—a problem hypoimmune stem cells were designed to circumvent.

Virtual Clinical Trials Summit

Virtual Clinical Trials Summit: The Premier Educational Event Focused on Decentralized Clinical Trials

In this virtual environment, we will look at current and future trends for ongoing virtual trials, diving into the many ways companies can improve patient engagement and trial behavior to enhance retention with a focus on emerging technology and harmonized data access across the clinical trial system.

The UCSF team used gene modification technology to design the cells so they avoid the immune responses that are either built into the body’s defense system or learned. The researchers achieved that feat by engineering the cells to express the protein CD47, which shuts down innate immune cells by activating signal regulatory protein alpha, or SIRP-alpha.

The researchers were surprised to discover that the hypoimmune stem cells were able to escape NK cells, even though NK cells were not previously known to express SIRP-alpha. Rather than studying lab-grown cell lines, they took cells directly from patients. That’s where they found SIRP-alpha.

What’s more, the UCSF team discovered that NK cells begin to express SIRP-alpha after they are activated by cytokines that are typically abundant in inflammatory states.

RELATED: Fierce Biotech’s 2020 Fierce 15 | Sana Biotechnology

To further prove out the utility of engineered stem cells, the UCSF researchers implanted cells with rhesus macaque CD47 into monkeys. They documented the activation of SIRP-alpha in NK cells. Those NK cells did not kill the transplanted cells.

A similar technique could be used, but in reverse, to implant pig cardiac cells into people, the UCSF team argued. If human CD47 were engineered into pig heart cells, they could be implanted into people without risking rejection by NK cells, they suggested.

Sana made waves in 2018 when it raised a whopping $700 million in a single venture round from the likes of Arch Venture Partners, Flagship Pioneering and Bezos Expeditions. “We believe that one of, if not the most, important thing happening in medicine over the next several decades is the ability to modulate genes, use cells as medicines, and engineer cells,” said Steve Harr, president and CEO of Sana, at the time.

Sana did not provide materials or funding for the new study, but it is now developing the hypoimmune stem cell technology for clinical testing.

The UCSF team believes their findings could also boost cancer immunotherapy. The engineered cells could help combat checkpoints that allow tumors to evade immune detection, they said.

“Many tumors have low levels of self-identifying MHC-I protein and some compensate by overexpressing CD47 to keep immune cells at bay,” said Lewis Lanier, Ph.D., director of the Parker Institute for Cancer Immunotherapy at the UCSF Helen Diller Family Comprehensive Cancer Center, in a statement. “This might be the sweet spot for antibody therapies that target CD47.”

Natural Killer Cell Destorying Cancer Cell Illustration

Scientists Discover a Way to Control the Immune System’s “Natural Killer” Cells With “Invisible” Stem Cells

  • January 8, 2021

Natural Killer Cell Destorying Cancer Cell Illustration

UC San Francisco scientists have discovered a new way to control the immune system’s “natural killer” (NK) cells, a finding with implications for novel cell therapies and tissue implants that can evade immune rejection. The findings could also be used to enhance the ability of cancer immunotherapies to detect and destroy lurking tumors.

The study, published today (January 8, 2021) in the Journal of Experimental Medicine, addresses a major challenge for the field of regenerative medicine, said lead author Tobias Deuse, MD, the Julien I.E. Hoffman, MD, Endowed Chair in Cardiac Surgery in the UCSF Department of Surgery.

“As a cardiac surgeon, I would love to put myself out of business by being able to implant healthy cardiac cells to repair heart disease,” said Deuse, who is interim chair and director of minimally invasive cardiac surgery in the Division of Adult Cardiothoracic Surgery. “And there are tremendous hopes to one day have the ability to implant insulin-producing cells in patients with diabetes or to inject cancer patients with immune cells engineered to seek and destroy tumors. The major obstacle is how to do this in a way that avoids immediate rejection by the immune system.”

Deuse and Sonja Schrepfer, MD, PhD, also a professor in the Department of Surgery’s Transplant and Stem Cell Immunobiology Laboratory, study the immunobiology of stem cells. They are world leaders in a growing scientific subfield working to produce “hypoimmune” lab-grown cells and tissues — capable of evading detection and rejection by the immune system. One of the key methods for doing this is to engineer cells with molecular passcodes that activate immune cell “off switches” called immune checkpoints, which normally help prevent the immune system from attacking the body’s own cells and modulate the intensity of immune responses to avoid excess collateral damage.

Schrepfer and Deuse recently used gene modification tools to engineer hypoimmune stem cells in the lab that are effectively invisible to the immune system. Notably, as well as avoiding the body’s learned or “adaptive” immune responses, these cells could also evade the body’s automatic “innate” immune response against potential pathogens. To achieve this, the researchers adapted a strategy used by cancer cells to keep innate immune cells at bay: They engineered their cells to express significant levels of a protein called CD47, which shuts down certain innate immune cells by activating a molecular switch found on these cells, called SIRPα. Their success became part of the founding technology of Sana Biotechnology, Inc, a company co-founded by Schrepfer, who now directs a team developing a platform based on these hypoimmune cells for clinical use.

But the researchers were left with a mystery on their hands — the technique was more successful than predicted. In particular, the field was puzzled that such engineered hypoimmune cells were able to deftly evade detection by NK cells, a type of innate immune cell that isn’t supposed to express a SIRPα checkpoint at all.

NK cells are a type of white blood cell that acts as an immunological first responder, quickly detecting and destroying any cells without proper molecular ID proving they are “self” — native body cells or at least permanent residents — which takes the form of highly individualized molecules called MHC class I (MHC-I). When MHC-I is artificially knocked out to prevent transplant rejection, the cells become susceptible to accelerated NK cell killing, an immunological rejection that no one in the field had yet succeeded in inhibiting fully. Deuse and Schrepfer’s 2019 data, published in Nature Biotechnology, suggested they might have stumbled upon an off switch that could be used for that purpose.

“All the literature said that NK cells don’t have this checkpoint, but when we looked at cells from human patients in the lab we found SIRPα there, clear as day,” Schrepfer recalled. “We can clearly demonstrate that stem cells we engineer to overexpress CD47 are able to shut down NK cells through this pathway.”

To explore their data, Deuse and Schrepfer approached Lewis Lanier, PhD, a world expert in NK cell biology. At first Lanier was sure there must be some mistake, because several groups had looked for SIRPα in NK cells already and it wasn’t there. But Schrepfer was confident in her team’s data.

“Finally it hit me,” Schrepfer said. “Most studies looking for checkpoints in NK cells were done in immortalized lab-grown cell lines, but we were studying primary cells directly from human patients. I knew that must be the difference.”

Further examination revealed that NK cells only begin to express SIRPα after they are activated by certain immune signaling molecules called cytokines. As a result, the researchers realized, this inducible immune checkpoint comes into effect only in already inflammatory environments and likely functions to modulate the intensity of NK cells’ attack on cells without proper MHC class I identification.

“NK cells have been a major barrier to the field’s growing interest in developing universal cell therapy products that can be transplanted “off the shelf” without rejection, so these results are extremely promising,” said Lanier, chair and J. Michael Bishop Distinguished Professor in the Department of Microbiology and Immunology.

In collaboration with Lanier, Deuse and Schrepfer comprehensively documented how CD47-expressing cells can silence NK cells via SIRPα. While other approaches can silence some NK cells, this was the first time anyone has been able to inhibit them completely. Notably, the team found that NK cells’ sensitivity to inhibition by CD47 is highly species-specific, in line with its function in distinguishing “self” from potentially dangerous “other.”

As a demonstration of this principle, the team engineered adult human stem cells with the rhesus macaque version of CD47, then implanted them into rhesus monkeys, where they successfully activated SIRPα in the monkeys’ NK cells, and avoided killing the transplanted human cells. In the future the same procedure could be performed in reverse, expressing human CD47 in pig cardiac cells, for instance, to prevent them from activating NK cells when transplanted into human patients.

“Currently engineered CAR T cell therapies for cancer and fledgling forms of regenerative medicine all rely on being able to extract cells from the patient, modify them in the lab, and then put them back in the patient. This avoids rejection of foreign cells, but is extremely laborious and expensive,” Schrepfer said. “Our goal in establishing a hypoimmune cell platform is to create off-the shelf products that can be used to treat disease in all patients everywhere.”

The findings could also have implications for cancer immunotherapy, as a way of boosting existing therapies that attempt to overcoming the immune checkpoints cancers use to evade immune detection. “Many tumors have low levels of self-identifying MHC-I protein and some compensate by overexpressing CD47 to keep immune cells at bay,” said Lanier, who is director of the Parker Institute for Cancer Immunotherapy at the UCSF Helen Diller Family Comprehensive Cancer Center. “This might be the sweet spot for antibody therapies that target CD47.”

Reference: 8 January 2021, Journal of Experimental Medicine.

Authors: The study’s lead authors were Deuse and UCSF TSI lab research scientist Xiaomeng Hu; Lanier and Schrepfer were the study’s senior authors, and Schrepfer is corresponding author. Other authors were Sean Agbor-Enoh of The Johns Hopkins School of Medicine and National Heart, Lung, and Blood Institute (NHLBI); Moon K. Jang at the NHLBI; Hannah Valantine at Stanford; Malik Alawi and Ceren Saygi of the University Medical Center Hamburg-Eppendorf in Germany; Alessia Gravina, Grigol Tediashvili, and Vinh Q. Nguyen of UCSF; and Yuan Liu of Georgia State University.

Funding: The research and researchers are supported by NHLBI (R01HL140236), the Parker Institute for Cancer Immunotherapy, and the US National Institutes of Health (NIH P30 DK063720 NIH S10 1S10OD021822-01).

Disclosures: Deuse is scientific co-founder and Schrepfer is scientific founder and Senior Vice President of Sana Biotechnology Inc. Xiaomeng Hu is now senior scientist at Sana Biotechnology Inc. Neither reagents nor any funding from Sana Biotechnology Inc. was used in this study. UCSF has filed patent applications that cover these inventions.

Do NOT follow this link or you will be banned from the site!