Research Area: Human Disease

Vaccine Booster

Biologist Jianzhu Chen works to enhance immune response

Mark Wolverton | Spectrum
November 16, 2020

Jianzhu Chen, professor of biology and a member of the Koch Institute for Integrative Cancer Research at MIT, is pursuing a different strategy from most of his colleagues working on SARS-CoV-2, the virus that causes Covid-19. “We focus on the immune system and fundamental mechanisms as well as their application in cancer immunotherapy, vaccine development, and metabolic diseases,” he explains. Rather than trying to develop a specific vaccine, Chen is pursuing vaccine platform technologies that can be used to enhance any vaccine.

This effort is built on Chen’s previous work on dengue fever, a severe tropical disease transmitted by mosquitos. “We have been working to improve a vaccine against dengue virus infection,” he says, “which has this phenomenon called antibody-dependent enhancement,” in which “non-neutralizing” antibodies bind to the virus but do not destroy it. The immune system’s pathogen-eating macrophages then consume these virus-antibody complexes and become infected themselves, making a subsequent infection worse.

Chen’s team has identified vaccine adjuvants, or enhancing agents, that can increase neutralizing (that is, effective) antibodies while reducing non-neutralizing antibody response in mice and nonhuman primates. The team is confident that using a similar strategy against Covid-19 would improve any vaccine’s effectiveness.

Addressing cytokine storm

Chen is also focusing on the dangerous hyperinflammatory response seen in Covid-19: the cytokine storm that can result when the immune system overreacts to infection.

“We have been working on macrophage biology for quite some time,” Chen says. “SARS-CoV-2 infection is a hyperinflammatory response, and macrophages probably play a critical role in that response.”

“We have identified many compounds, including FDA-approved drugs, bioactive compounds, and natural products that can modulate macrophage activity to become anti-inflammatory,” he says. Such macrophage modulation would likely be used in conjunction with other treatments as a therapeutic strategy for already-infected patients.

A promising result from either research project could be used along with a Covid-19 vaccine to enhance immune response while preventing or reducing the severity of any possible reinfection. But it’s too early to tell what might happen. “We don’t have a vaccine yet,” Chen notes. “It’s not clear when we’ll have one. Even when we have one, it’s not clear how well it will work. It could be 95% protection; it could be 50%. Some of them may not confer much protection at all. But even 50% or 60% is a significant number of people.”

Another challenge, Chen acknowledges, is that medical research must move from theory to lab and ultimately into the real world. Vaccines can be designed and modeled on computers but eventually “we have to test them to see if they work as we expect,” he says. “You have to immunize mice or some other animals and then challenge them with SARS-CoV-2 to see whether the vaccine protects the animals from infection or dramatically minimize disease symptoms. These kinds of studies can’t be modeled computationally.”

Chen also hopes that his particular contributions will have benefits beyond the pandemic. “We’re aiming to develop a vaccine platform prototyped on SARS-CoV-2 that can be used for the development of many other vaccines as well, using the most appropriate technologies.” If that happens, science will have dug at least one substantial jewel out of the depths of an unprecedented public health crisis.

Two treatment methods enhance chemotherapy by the same means: cellular senescence
Raleigh McElvery
November 10, 2020

In 2019, cancer researchers from MIT found a drug that targeted an elusive molecular interaction previously considered “undruggable.” In so doing, they opened up a new realm of chemotherapy. This drug, called JH-RE-06, sensitized tumors to treatment, but the scientists didn’t fully understand how it exerted its effects. Now, in a pair of studies published in PNAS, the same team is closer to determining which cellular processes this drug alters to enhance cancer therapy.

Many widely-used chemotherapies, like cisplatin, kill tumors by damaging their DNA and inducing programmed cell death. But cells are resilient, and many can continue to function with the help of repair enzymes that simply bypass the damage and continue to replicate the DNA. As a result, some tumors not only defy death, but gain mutations that render them more resistant to treatment or spur new malignancies elsewhere.

“If you’re not making a patient better, it’s very likely you’re making them worse,” says Michael Hemann, associate professor of biology and co-author on both studies. Rather than fully replacing conventional DNA-damaging treatments — which could take decades — Hemann suggests an effective “medium-term” solution: augmenting low doses of cisplatin with safer agents that strengthen the chemotherapy’s tumor-killing capacity.

The team had tested this approach back in 2019, when they first identified JH-RE-06 and saw it enhanced chemotherapy treatment. These experiments revealed that JH-RE-06 bound to an especially shallow (and infamously undruggable) pocket of one DNA repair enzyme called REV1. This barred REV1 from interacting with another key enzyme, and prevented the cancer cells from recovering after cisplatin treatment. But what happened next to cause the tumors to shrink was unclear.

As they began their next round of experiments, the researchers expected to find that the drug would simply enhance the way cisplatin kills tumors via programmed cell death.

Nimrat Chatterjee, Walker’s former postdoc and lead author of the first study, treated mice and individual cells with a combination of cisplatin and JH-RE-06. She expected to see signs of programmed cell death, but for months, she saw no such markers.“We thought that if we blocked the DNA repair process with the JH compound, we’d see more programmed cell death,” says co-author Graham Walker, American Cancer Society Professor and Howard Hughes Medical Institute Professor. “As it turns out, we did see more cell death — just not the kind we were expecting.”

One evening, just as she was about to head home for the day, she peeked through her microscope at the cancer cells treated with JH-RE-06 and cisplatin. She noticed they were fluorescing a strange green color.

“At first, I didn’t know what I was seeing,” she recalls. But after some follow-up, it became clear that the mysterious green color was coming from lipid-containing residues that usually appear as cells age and stop dividing. The cells appeared to be in a permanently dormant state known as senescence — not yet dead but unable to proliferate. JH-RE-06 was altering cisplatin function by triggering a second molecular pathway independent of programmed cell death.

“That was one of the best ‘aha’ moments of my scientific career so far,” Chatterjee says. “REV1, the DNA repair enzyme that JH-RE-06 binds, may have other novel biological functions and a larger role in cancer cell etiology than we originally thought. We’re now grappling with more questions about REV1 than ever before.”

Around the same time, Faye-Marie Vassel PhD ’20, Walker and Hemann’s former joint graduate student and lead author of the second study, witnessed a similar phenomenon in her own experiments. She was investigating a different way of inhibiting the two key DNA repair enzymes that enable cancer cells to survive chemotherapy. Instead of probing JH-RE-06, which latches onto REV1, she tried deleting REV1’s binding partner, called REV7. This protein is particularly influential because it serves an important role in fixing double-stranded breaks in addition to interacting with REV1.

When Vassel deleted REV7 from mice with non-small cell lung cancer, the tumors became more sensitive to cisplatin, as expected. But, like Chatterjee, she saw signs of senescence rather than programmed cell death. The two studies had converged on a common biology: adding JH-RE-06 or deleting REV7 strengthened the effects of cisplatin by inducing this dormant state.

Cancer detection and treatment methods have improved dramatically in the last two decades, but drug-resistant cancers like non-small cell lung cancer remain difficult to combat, Vassel says. “Our experiments are the first to show that senescence induction is likely a consequence of REV7 inhibition,” she adds. “Inhibiting REV7 in tandem with cisplatin therapy may prove to be an effective strategy for enhancing a chemotherapeutic response.”

Chemotherapies that trigger programmed cell death have been the mainstay of cancer treatment for decades. But studies like these show that triggering senescence may be a promising complementary strategy. Most senescent cells are eventually cleared by the immune system, and the researchers suspect this is how cancer cells treated with JH-RE-06 or REV7 inhibitors would be eliminated from the body.

Walker and Hemann agree that, at the moment, their sister studies raise more questions than answers. As Walker explained, “We’ve pried open a new discovery, and hopefully set the stage for many exciting experiments to come.”

Top image: Genetically-engineered mouse model for lung cancer. Credit: Credit: National Cancer Institute, National Institutes of Health. NIH Image Gallery/Flickr (CC BY-NC)
The REV7 image was originally published in: “Structural basis of Rev1-mediated assembly of a quaternary vertebrate translesion polymerase complex consisting of Rev1, heterodimeric polymerase (Pol) ζ, and Pol κ.”
Journal of Biological Chemistry, online August 2, 2012, DOI: 10.1074/jbc.M112.394841
Jessica Wojtaszek, Chul-Jin Lee, Sanjay D’Souza, Brenda Minesinger, Hyungjin Kim, Alan D. D’Andrea, Graham C. Walker, and Pei Zhou.

Citations:
“REV1 inhibitor JH-RE-06 enhances tumor cell response to chemotherapy by triggering senescence hallmarks”
Proceedings of the National Academy of Sciences, online November 9, 2020, DOI: 10.1073/pnas.2016064117
Nimrat Chatterjee , Matthew A Whitman, A Harris , Sophia M Min , Oliver Jonas , Evan C Lien , Alba Luengo , Matthew G Vander Heiden , Jiyong Hong , Pei Zhou , Michael T Hemann , and Graham C Walker 

“Rev7 loss alters cisplatin response and increases drug efficacy in chemotherapy-resistant lung cancer”
Proceedings of the National Academy of Sciences, online November 3, 2020, DOI: 10.1073/pnas.2016067117
Faye-Marie Vassel, Ke Bian, Graham C. Walker, and Michael T. Hemann

Aspiring physician explores the many levels of human health

During her time at MIT, senior Ayesha Ng’s interests have expanded from cellular biology to the social systems that shape public health.

Alison Gold | School of Science
November 9, 2020

It was her childhood peanut allergy that first sparked senior Ayesha Ng’s fascination with the human body. “To see this severe reaction happen to my body and not know what was happening — that made me a lot more curious about biology and living systems,” Ng says.

She didn’t exactly plan it this way. But in her three and a half years at MIT, Ng, a biology and cognitive and brain sciences double major from the Los Angeles, California area, has conducted research and taken classes examining just about every level of human health — from cellular to societal.

Most recently, her passion for medicine and health equity led her to the National Foundation for the Centers for Disease Control and Prevention (CDC), where, this summer, she worked to develop guidelines for addressing health disparities on state and local health jurisdictions’ Covid-19 data dashboards. Now, as an aspiring physician amidst the medical school application process, Ng has a sense of how microbiological, physiological, and social systems interact to affect a person’s health.

Starting small

Throughout her entire first year at MIT, Ng studied the biology of health at a cellular level. Specifically, she researched the effects of fasting and aging on regeneration of intestinal stem cells, which are located in the human intestinal crypts and continuously self-divide and reproduce. Understanding these metabolic mechanisms is crucial, as their deregulation can lead to age-associated diseases such as cancer.

“That experience allowed me to broaden my technical skills, just getting used to so many different types of molecular biological techniques right away, which I really appreciated,” Ng says of her time at the Whitehead Institute for Biomedical Research in Professor David Sabatini’s lab.

“After some time, I realized that I also wanted to also study sciences at a broader, more macro level, instead of only the microbiology and molecular biology that we were studying in Course 7,” Ng says of her biology major.

In addition to studying the biology of cancer, Ng had developed a curiosity about the human brain and how it functions. “I was really interested in that, because my grandpa has dementia,” Ng says.

Seeing her grandfather’s cognitive decline, she was inspired to become involved in MIT BrainTrust, a student organization that offers a social support network for individuals from around the Boston, Massachusetts area who have brain injuries. “We have these meetings, in which I serve as one of only one or two students there to facilitate a safe space where we can have all these individuals with brain injury gather,” Ng says of the peer-support aspect of the program. “They can really share their mutual challenges and experiences.”

Investigating the brain

To pursue her interest in brain research and the societal impact of brain injuries, Ng traveled to the University of Hong Kong the summer after her first year as an MIT International Science and Technology Initiatives (MISTI) China Fung Scholar. Working with Professor Raymond Chang, she began to examine neurodegenerative disease and used tissue-clearing techniques to visualize 3D mouse brain structures at cellular resolution. “That was personally meaningful for me, to research about that and learn more about dementia,” Ng says.

Returning to MIT her sophomore year, Ng was certain that she wanted to continue studying the brain. She began working on Alzheimer’s research at the MIT Picower Institute for Learning and Memory in the lab of Professor Li-Huei Tsai, the Picower Professor of Neuroscience at MIT. Much existing research into Alzheimer’s disease has been at the bulk-tissue level, focusing on the neurons’ role in neurodegeneration associated with aging.

Ng’s work with Tsai considers the complexity of alterations across genes and less-abundant cell types, such as microglia, astrocytes, and other supporting glial cells that become dysregulated in the brains of patients with Alzheimer’s. Considering the interplay between and within cell types during neurodegeneration is most intriguing to her. While some molecular processes are protective, other damaging ones simultaneously occur and can exist even within the same cell type. This intricacy has made the mechanistic basis behind Alzheimer’s progression elusive and the research that much more crucial.

“It’s really interesting to see how heterogeneous and complex the responses are in Alzheimer’s brains,” Ng says of the research program with Tsai, a founding director of MIT’s Aging Brain Initiative. “I really think about these potential new drug targets to improve treatment for Alzheimer’s in the future because I have seen, with my grandpa especially, how treatment is really lacking in the neurodegeneration field. There’s no treatment that’s been able to stop or even slow the progression of Alzheimer’s disease.”

Her research project in the Tsai Lab relies on a technology called single-nucleus RNA sequencing (snRNA-seq), which extracts the genomic information contained in individual cells. This is followed by computational dimension reduction and clustering algorithms to examine how Alzheimer’s disease differentially affects genes and specific cell types.

“With that project, we’ve been able to use single-nucleus RNA sequencing to really look at the brains of human Alzheimer’s patients,” Ng says. “And with the single-cell technology, we’re able to look at brain tissue at a much higher resolution, allowing us to see that there’s so much heterogeneity within the brain.”

After conducting more than a year of Alzheimer’s research and then taking a human physiology class in her third year, Ng decided to add a second major in brain and cognitive sciences to gain deeper insight specifically into how the nervous system within the body functions.

“That class really allowed me to realize that I really love organ systems and wanted to study by looking at more physiological mechanisms,” Ng says. “It has been really great to, at the end of my college career, really delve more into a very specific system.”

Medicine and society

Having gained perspective on cellular and microbiology, and human organ systems, Ng decided to zoom out further, interning this past summer at the National Foundation for the CDC. She found the opportunity through MIT’s PKG Center, applied as one of 60 candidates, and was selected for a team of four. There, as a member of the CDC Foundation’s Health Equity Strike Team, she examined how to increase transparency of publicly available Covid-19 data on health disparities and how the narrative tied to health equity can be modified in public health messages. This involved harnessing data about the demographics of those most affected during Covid-19 — including how infection and mortality rates differ starkly based on social factors including housing conditions, socioeconomic status, race, and ethnicity.

“Thinking about all these factors, we compiled a set of best practices for how to present data about Covid-19, what data should be collected, and tried to push those out to help jurisdictions as best-practice recommendations,” Ng says. “That did really increase my interest in health equity and made me realize how important public health is as well.”

Amidst the Covid-19 pandemic, Ng is spending the first semester of her senior year at home with her family in the Los Angeles area. “I really miss the people and not being able to interact with not only other students and peers, but also faculty as well,” she says. “I really wanted to enjoy time with friends, and just explore more of MIT, too, which I didn’t always get the chance to do over the past few years.”

Still, she continues to participate in both BrainTrust and MIT’s Asian Dance team, remotely, through weekly practices on Zoom.

“I think dance is one of the biggest de-stressors for me; I had never done dance before going to college. Getting to meet this team and join this community allowed me not only to connect to my Asian cultural roots, but also just expose myself to this new art form where I could really learn how to express myself on stage,” Ng says. “And that really has been the source of relief for me to just liberate any worries that I have, and has increased my sense of self-awareness and self-confidence.”

Armed with the many experiences she has enjoyed at MIT, both in and out of the classroom, Ng plans to continue studying both medicine and public health. She’s excited to explore different potential specialties and is currently most intrigued by surgery. Whichever specialty she may choose, she is determined to include health equity and cultural sensitivity in her practice.

“Seeing surgeons, I personally think that being able to physically heal a patient with my own hands, that would be the most rewarding feeling,” Ng says. “I will strive to, as a physician, use whatever platform that I have to advocate for patients and really drive health-care systems to overcome disparities.”

Cancer researchers collaborate, target DNA damage repair pathways for cancer therapy

MIT researchers find blocking the expressions of the genes XPA and MK2 enhances the tumor-shrinking effects of platinum-based chemotherapies in p53-mutated cancers.

Koch Institute
October 2, 2020

Cancer therapies that target specific molecular defects arising from mutations in tumor cells are currently the focus of much anticancer drug development. However, due to the absence of good targets and to the genetic variation in tumors, platinum-based chemotherapies are still the mainstay in the treatment of many cancers, including those that have a mutated version of the tumor suppressor gene p53. P53 is mutated in a majority of cancers, which enables tumor cells to develop resistance to platinum-based chemotherapies. But these defects can still be exploited to selectively target tumor cells by targeting a second gene to take down the tumor cell, leveraging a phenomenon known as synthetic lethality.

Focused on understanding and targeting cell signaling in cancer, the laboratory of Michael Yaffe, the David H. Koch Professor Science and director of the MIT Center for Precision Cancer Medicine, seeks to identify pathways that are synthetic lethal with each other, and to develop therapeutic strategies that capitalize on that relationship. His group has already identified MK2 as a key signaling pathway in cancer and a partner to p53 in a synthetic lethal combination.

Now, working with a team of fellow researchers at MIT’s Koch Institute for Integrative Cancer Research, Yaffe’s lab added a new target, the gene XPA, to the combination. Appearing in Nature Communications, the work demonstrates the potential of “augmented synthetic lethality,” where depletion of a third gene product enhances a combination of targets already known to show synthetic lethality. Their work not only demonstrates the effectiveness of teaming up cancer targets, but also of the collaborative teamwork for which the Koch Institute is known.

P53 serves two functions: first, to give cells time to repair DNA damage by pausing cell division, and second, to induce cell death if DNA damage is too severe. Platinum-based chemotherapies work by inducing enough DNA damage to initiate the cell’s self-destruct mechanism. In their previous work, the Yaffe lab found that when cancer cells lose p53, they can re-wire their signaling circuitry to recruit MK2 as a backup pathway. However, MK2 only restores the ability to orchestrate DNA damage repair, but not to initiate cell death.

The Yaffe group reasoned that targeting MK2, which is only recruited when p53 function is absent, would be a unique way to create a synthetic lethality that specifically kills p53-defective tumors, by blocking their ability to coordinate DNA repair after chemotherapy. Indeed, the Yaffe Lab was able to show in pre-clinical models of non-small cell lung cancer tumors with mutations in p53, that silencing MK2 in combination with chemotherapy treatment caused the tumors to shrink significantly.

Although promising, MK2 has proven difficult to drug. Attempts to create target-specific, clinically viable small-molecule MK2 inhibitors have so far been unsuccessful. Researchers led by co-lead author Yi Wen Kong, then a postdoc in the Yaffe lab, have been exploring the use of RNA interference (siRNA) to stop expression of the MK2 gene, but siRNA’s tendency to degrade rapidly in the body presents new challenges.

Enter the potential of nanomaterials, and a team of nanotechnology experts in the laboratory of Paula Hammond, the David H. Koch Professor of Engineering, head of the MIT Department of Chemical Engineering, and the Yaffe group’s upstairs neighbor. There, Kong found a willing collaborator in then-postdoc Erik Dreaden, whose team had developed a delivery vehicle known as a nanoplex to protect siRNA until it gets to a cancer cell. In studies of non-small cell lung cancer models where mice were given the MK2-targeting nanocomplexes and standard chemotherapy, the combination clearly enhanced tumor cell response to chemotherapy. However, the overall increase in survival was significant, but relatively modest.

Meanwhile, Kong had identified XPA, a key protein involved in another DNA repair pathway called NER, as a potential addition to the MK2-p53 synthetic lethal combination. As with MK2, efforts to target XPA using traditional small-molecule drugs have not yet proven successful, and RNA interference emerged as the team’s tool of choice. The flexible and highly controllable nature of the Hammond group’s nanomaterials assembly technologies allowed Dreaden to incorporate siRNAs against both XPA and MK2 into the nanocomplexes.

Kong and Dreaden tested these dual-targeted nanocomplexes against established tumors in an immunocompetent, aggressive lung cancer model developed in collaboration between the laboratories of professor of biology Michael Hemann and Koch Institute Director Tyler Jacks. They let the tumors grow even larger before treatment than they had in their previous study, thus raising the bar for therapeutic intervention.

Tumors in mice treated with the dual-targeted nanocomplexes and chemotherapy were reduced by up to 20-fold over chemotherapy alone, and similarly improved over single-target nanocomplexes and chemotherapy. Mice treated with this regimen survived three times longer than with chemotherapy alone, and much longer than mice receiving nanocomplexes targeting MK2 or XPA alone.

Overall, these data demonstrate that identification and therapeutic targeting of augmented synthetic lethal relationships — in this case between p53, MK2 and XPA — can produce a safe and highly effective cancer therapy by re-wiring multiple DNA damage response pathways, the systemic inhibition of which may otherwise be toxic.

The nanocomplexes are modular and can be adapted to carry other siRNA combinations or for use against other cancers in which this augmented synthetic lethality combination is relevant. Beyond application in lung cancer, the researchers — including Kong, who is now a research scientist at the Koch Institute, and Dreaden, who is now an assistant professor at Georgia Tech and Emory School of Medicine — are working to test this strategy for use against ovarian and other cancers.

Additional collaborations and contributions were made to this project by the laboratories of Koch Institute members Stephen Lippard and Omer Yilmaz, the Eisen and Chang Career Development Professor.

This work was supported in part by a Mazumdar-Shaw International Oncology Fellowship, a postdoctoral fellowship from the S. Leslie Misrock (1949) Frontier Fund for Cancer Nanotechnology, and by the Charles and Marjorie Holloway Foundation, the Ovarian Cancer Research Foundation, and the Breast Cancer Alliance.

Type 1 diabetes from a beta cell’s perspective
Eva Frederick | Whitehead Institute
September 24, 2020

Type 1 diabetes is an autoimmune disease that occurs when T-cells in the immune system attack the body’s own insulin-producing cells, called beta cells, in the pancreas. Usually diagnosed in children and young adults, type 1 diabetes accounts for around five percent of all diabetes cases.

The underlying biology of type 1 diabetes is tricky to study for a number of reasons. For one thing, by the time a person begins to show symptoms, their T-cells have already been destroying beta cells for a long period — months or even years. Also, the initial trigger for the disease is often unclear; a number of beta cell proteins can set off the immune response.

In a study published Sept. 22 in Cell Reports Medicine, researchers in the lab of Whitehead Institute Founding Member Rudolf Jaenisch demonstrate a new experimental system for more precisely studying the mechanisms of type 1 diabetes, focusing on how a person’s beta cells respond to an attack from their own immune system. In doing so, they reveal features of the disease that could be targets for future therapeutics.

“Here our question was, let’s say the T cells get activated; what happens next from the perspective of beta cells? Could we find some potential intervention opportunities?” said Haiting Ma, a postdoctoral associate in Jaenisch’s lab and the first author of the study.

Ma, working with Jaenisch, also a professor of biology at MIT, and Jacob Jeppesen, Novo Nordisk’s Head of Diabetes and Metabolism Biology, took a synthetic biology approach to achieve this goal.

The researchers engineered a system by inducing human pluripotent stem cells to differentiate into functional pancreatic beta cells, and added a model antigen called CD19 to these cells using CRISPR techniques. They established that these cells functioned as insulin-producing beta cells by implanting them in diabetic mice; upon receiving the cells, the mice experienced an improvement in glucose levels.

They then replicated the autoimmune components of the disease using engineered immune cells called CAR-T cells. CAR-T cells are T-cells tailor-made to attack a certain type of cell; for example, they can be targeted to tumor cells to treat certain types of cancer. For the diabetes model, the researchers engineered the cells to contain receptors for the model antigen CD19.

When the researchers cocultured the synthetic beta cells and CAR-T cells, they found the system worked well to mimic a simplified version of type 1 diabetes: the CAR-T cells attacked the beta cells and caused them to enter the process of cell death. The researchers were also able to implement the strategy in humanized mice.

Using their new experimental system, the researchers were able to identify some interesting factors involved in the beta cells’ response to diabetic conditions. For one thing, they found that the beta cells cranked up production of protective mechanisms such as the protein PDL1. PDL1 is a protein found on non-harmful cells in the body that, in normal circumstances, prevents the immune system from attacking them.

Changes in PDL1 levels had been associated with type 1 diabetes in previous studies. Now, Ma wondered if it was possible to rescue the beta cells from the immune onslaught by inducing the expression of even more of the helpful protein. “We found that we can help beta cells by giving them a higher expression of PDL1,” he said. “When we do this, they can do better in the model.” If validated in human cells, increasing expression of PDL1 could be evaluated as a potential therapeutic method, Ma said.

Another finding concerned the way the cells died after T-cell attack. Ma found that the genes that were being upregulated as the beta cells were under attack were associated not with the usual form of cell death, apoptosis, but with a more inflammatory and violent kind of cell death called pyroptosis.

“The interesting thing about pyroptosis is that it causes the cells to release their contents,” Ma said. “This is in contrast to apoptosis, which is considered to be the main mechanism for autoimmune response. We think that pyroptosis could play a role in propelling this autoimmune reaction, because the contents from beta cells include multiple potential antigens. If these are released, they can be picked out by antigen presenting cells and start to crank up this autoimmunity.”

The process of pyroptosis in the context of beta cell autoimmunity could be linked to ER stress in beta cells, a highly secretory cell type. Indeed, an ER stress inducing chemical increased the marker of pyroptosis.

If researchers could find a way to inhibit the process of pyroptosis safely in humans, it could potentially lessen the severity of the autoimmune reaction that is the hallmark of type 1 diabetes. Pyroptosis is mediated by a protein called caspase-4, which can be inhibited in the lab. “If that can be validated in patient beta cells, that could indicate that modulating caspases could also be [a therapeutic mechanism],” Ma said.

Going forward, Ma and Jaenisch plan to investigate the immune mechanisms underlying autoimmunity in humans by using induced pluripotent stem cells from patients with type 1 diabetes. “These cells could be differentiated into immune cells such as T, B, macrophage, and dendritic cells, and we can investigate how they interact with beta cells,” Ma said.

They also plan to keep improving their new experimental system. “This system provides a very robust and tractable synthetic immune response that we can use to study type 1 diabetes,” said Jaenisch. “In the future it could be used to study other autoimmune diseases.”

This study was supported by a generous gift from Liliana and Hillel Bachrach, a collaborative research agreement from Novo Nordisk, and NIH grant 1R01-NS088538 (to R.J.).

***

Written by Eva Frederick

***

Citation:

Ma, H., Jeppesen, J, and Jaenisch, R. “Human T-cells expressing a CD19 CAR-T receptor provide insights into mechanisms of human CD19 positive cell destruction.” Cell Reports Medicine. Sept 22. https://doi.org/10.1016/j.xcrm.2020.100097

These genes help explain how malaria parasites survive treatment with common drug
Eva Frederick | Whitehead Institute
September 23, 2020

The essential malaria drug artemisinin acts like a “ticking time bomb” in parasite cells — but in the half a century since the drug was introduced, malaria-causing parasites have slowly grown less and less susceptible to the treatment, threatening attempts at global control over the disease.

In a paper published September 23 in Nature Communications, Whitehead Institute Member Sebastian Lourido and colleagues use genome screening techniques in the related parasite Toxoplasma gondii (T. gondii) to identify genes that affect the parasites’ susceptibility to artemisinin. Two genes stood out in the screen: one that makes the drug more lethal, and another that helps the parasite survive the treatment.

Artemisinin is derived from the extract of sweet wormwood (Artemisia annua), and is usually used against malaria as part of a combination therapy. “Artemisinin kills malaria-causing parasites super fast—it will wipe out 90 percent of parasites within 24 hours,” says former postdoctoral researcher and co-first author Clare Harding, now a research fellow at the University of Glasgow. Once the fast-acting drug clears out the bulk of the parasites—such as Plasmodium falciparum, the culprit in the deadliest forms of malaria—from the bloodstream, the second drug finishes off the stragglers, curing the infection.

“Artemisinin works differently than most antibiotics,” Lourido said. “You can think of it as a sort of bomb that needs to be turned on in order to work.” The molecule required to light the drug’s fuse is called heme. Heme is a small molecule that facilitates several cellular functions, including electron transport and the delivery of oxygen to tissues as a component of hemoglobin. When heme molecules encounter artemisinin, they activate the drug allowing the creation of small, toxic radicals which react with proteins, lipids and metabolites inside the parasite, leading to its death.

Lourido, Harding, and co-first authors Boryana Petrova and Saima Sidik (“We were the ‘Heme Team,’” Harding said) wanted to understand what mechanisms the less susceptible parasites were using to avoid activating the “bomb”. Previously, Lourido and his lab—which focuses on apicomplexan parasites, a group which includes both Toxoplasma gondii and the malaria-causing Plasmodium falciparum—had developed a method to screen the entire genome of T. gondii to discover beneficial and harmful mutations. For a number of reasons, the screen does not work on Plasmodium parasites, but Lourido hypothesized that the related parasites’ genomes were similar enough that the method could prove helpful.

After running the screen, two genes stood out to the researchers as important factors in the parasites’ susceptibility to artemisinin treatment. One, called Tmem14c, seemed to be protecting the parasites: when the gene was disrupted in the screen, the parasites became more susceptible to treatment with artemisinin. The gene is analogous to one in red blood cells that serves as a transporter for heme and its building blocks, shuttling them in and out of the mitochondrion.

“What could be happening here is that, in the absence of Tmem14c, heme, artemisinin’s activator, collects within the mitochondria where it is being synthesized, thereby rendering the mitochondria better at activating that ticking time bomb,” Lourido said. “Having that high concentration of heme in the mitochondria is like having a flame when there is a gas leak.”

The screen also identified one mutation that led to parasites being less sensitive to artemisinin. The mutation affected a gene called DegP2, the product of which interacts with several mitochondrial proteins and appears to play a role in heme metabolism. When less DegP2 was present, the cells contained a lower amount of heme, which in turn made it less likely that the parasites would be killed by artemisinin.

Both the findings support other research suggesting that heme metabolism is crucial for artemisinin susceptibility. “It is important to consider the role of heme when combining artemisinin with other therapies,” Lourido said. “You would want to avoid combination therapy that might inadvertently suppress the level of heme within the parasite and thereby reduce susceptibility to antiparasitic agents.”

The project also showed the potential of using the Toxoplasma screening method as a model to study other related parasites. The screen confirmed findings in Toxoplasma that had previously been shown in Plasmodium, suggesting that it could be a valuable tool in studying malaria and other diseases caused by apicomplexan parasites.

“Through the amazing screens and molecular biology that you can do in Toxoplasma, we can really learn a lot about the biology of this diverse group of parasites,” Lourido said. “Defeating malaria is going to take a lot of different and creative approaches, and the fundamental research that we can do in Toxoplasma can in fact inform many of the critical clinical questions we need to answer to control this disease.”

***

Written by Eva Frederick

***

Harding, C., Sidik, S, and Petrova, B., et al. “Genetic screens reveal a central role for heme metabolism in artemisinin susceptibility.” Nature Communications. DOI: https://doi.org/10.1038/s41467-020-18624-0

Covid-19 scientific leaders share expertise in new MIT class
Greta Friar | Whitehead Institute
September 9, 2020

As the Covid-19 pandemic swept across the globe, bringing everyday life to a screeching halt, researchers at MIT and its affiliates ramped down much of their lab work and stopped teaching classes in person, but refused to come to a standstill. Instead, they changed tacks and took action investigating the many unknowns of Covid-19 and the virus that causes it (SARS-CoV-2), organizing pandemic responses, and communicating with the public and each other about what they knew.

One result of this period was the advent of a new course, aimed at providing MIT students with information on the science of the pandemic. The MIT Department of Biology tapped two scientists with experience working on pandemics to spearhead a course, 7.00 (COVID-19, SARS-CoV-2 and the Pandemic), which began Sept. 1. Whitehead Institute member and MIT Professor Richard Young, who had been quick to organize Covid-19 related research efforts, and Ragon Institute Associate Director Facundo Batista, a resident expert on immunology and infectious disease, agreed to lead the course.

The class meets virtually on Tuesday mornings, and a public livestream and recordings are available for anyone who wants to watch the lectures. Students who are taking the course for credit also gain access to a weekly session led by Lena Afeyan, a teaching assistant and MIT graduate student in Young’s lab at the Whitehead Institute. The session provides relevant background information on the science before the lectures.

Getting students up to speed on what is and is not known about the pandemic is no easy task. The science is complex and, in these early days, full of unknowns. Experts in many fields must pool their knowledge; virologists, immunologists, epidemiologists, public health researchers, clinicians, and more are focused on important pieces of the puzzle. Therefore, Young and Batista reached out to the leaders in all of those fields to give lectures in the course. Students will hear from experts that include Anthony Fauci, the longtime director of the National Institute of Allergy and Infectious Diseases, as well as David Baltimore of Caltech; Kizzmekia Corbett of the National Institutes of Health; Britt Glaunsinger of the University of California at Berkeley; Akiko Iwasaki of Yale University; Eric Lander of the Broad Institute of MIT and Harvard; Michel Nussenzweig of Rockefeller University; Arlene Sharpe of Harvard Medical School and Brigham and Women’s Hospital; Bruce Walker of the Ragon Institute of Massachusetts General Hospital, MIT, and Harvard; and others at the forefront of Covid-19 efforts. The course faculty agree that the best way to get accurate information to students is to have the experts provide it directly.

Designing the course

For many of the students, Covid-19 may be their first serious encounter with a pandemic, but a number of the lecturers have worked on the AIDS pandemic or other widespread infectious diseases, which they draw on when teaching.

“I like to put the coronavirus in the context of viruses I know better, like flu and HIV and polio virus,” says David Baltimore, the Nobel laureate professor of biology and president emeritus at Caltech who was previously the first director of the Whitehead Institute and a professor at MIT. However, the scientists’ relevant backgrounds can only help so much. The new coronavirus is a unique and difficult research subject.

“It has no obvious evolutionary relationship to other viruses. It’s got a much longer RNA, many more genes, so more complexity of function, more complexity of genetics, and it’s received relatively little study up until recently,” Baltimore says. “There is a lot more work that needs to be done.”

When planning the class, Young wanted to give all of the information needed to understand what is likely the first pandemic to powerfully impact the lives of the undergraduates taking the course. His motives were pedagogical — and practical.

“If we give people knowledge of what’s known and not known about the virus, provided by experts whom they trust, they can help us come up with solutions,” Young says.

Young and Batista expect that some of their students will soon be conducting their own Covid-19 research. Batista hopes that this experience will encourage students to think even beyond the scope of the current pandemic.

“I think the U.S. and the Western world have underestimated the risk of infectious diseases because the big pandemics have been happening elsewhere. This class is about bringing people together on Covid-19, and more than that, [it is about] creating a consciousness about the threat of future infections,” Batista says.

Where to start?

The first lecture was given by Bruce Walker, director of the Ragon Institute. Walker provided an overview of the available information, including how the pandemic appears to have started, how the virus causes disease, and what the prospects are for treatment and vaccines. The level of the science is aimed at MIT undergraduates, but because the livestream audience may have different science backgrounds, Walker made sure to define basic terms and concepts as he went. The lecture was attended by 250 students, with more than 7,000 people watching the livestream.

Registered students can ask questions during a Q&A at the end of each lecture. Walker addressed students’ concerns about the U.S. response to the pandemic, the risk of reinfection, mutability of the virus, and challenges with new types of vaccines. With the aim of providing accurate information, his answers were not always reassuring. However, in spite of the many uncertainties that the scientists are grappling with, the course faculty’s message for students is an optimistic one.

“People have felt powerless in this pandemic,” Afeyan says. “A course like this can help people feel like they have the tools to do something about it. There is a plethora of problems that will stem from the pandemic, so there are lots of ways to get involved regardless of your field.”

Researchers have banded together across MIT, Whitehead Institute, Ragon Institute, and around the globe to address the pandemic. For students who want to join the research effort, the content of the lectures is paired with discussions during Afeyan’s sessions with researchers earlier in their careers, who can talk to the students about next steps should they choose to pursue one of the fields presented in the course.

As for students and audience members simply looking to understand the public health event that has so strongly impacted their world, the faculty hope that the course will provide them with the answers they need. Scientists are not the only ones dealing with lots of uncertainty these days, and there is value in learning what the experts know as they know it, straight from the source.

A computational approach to cancer

Toni-Ann Nelson transformed remote summer research into an opportunity to learn a new set of tools for analyzing tumors.

Raleigh McElvery
August 20, 2020

Toni-Ann Nelson has wanted to find a cure for cancer ever since she was nine years old and lost her grandfather to the disease. “I remember thinking there must be something that the doctors and scientists were missing,” she recalls. “It just couldn’t be that complicated.” Now one semester away from earning her degree in molecular biology, Nelson is realizing cancer is just that — complicated. After conducting cancer research during MIT’s Summer Research Program in Biology (MSRP-Bio), she understands much more about the intricacies of tumors and metastasis. But she’s also glimpsed just how many cellular puzzles remain to be solved.

Growing up in Jamaica, Nelson enjoyed all her science classes, but preferred biology because she knew it would provide the foundation to probe cancer. She graduated as the valedictorian of her high school class, and earned a scholarship to Alcorn State University in Mississippi, where she began in the spring of 2017.

Alcorn doesn’t have any cancer research facilities, so Nelson secured a position as an undergraduate researcher in Yan Meng’s plant tissue culture lab. For three years, Nelson aimed to improve viral disease resistance in sweet potatoes. Even though she wasn’t conducting clinical research, she mastered key molecular biology techniques like PCR, gel electrophoresis, and tissue culture.

“Fundamental research is important because many times finding a cure requires starting with the basics, and understanding what’s going on inside the cell,” she says.

When Nelson was accepted into MSRP-Bio as a Gould Fellow and assigned to work in Tyler Jacks’ lab, she was elated to get her first hands-on cancer research experience. But in April 2020 — two months before the program was slated to begin — MIT’s campus temporarily shut down due to the COVID-19 pandemic, and MSRP-Bio 2020 became a remote learning experience.

As a result, Nelson and her MSRP-Bio cohort conducted their research from home. She took on a computationally-intensive project that was conducive to remote work and required taking an online quantitative methods class. In a manner of weeks, she learned an entirely new set of skills, including programming languages like Python.

“I always thought that I wouldn’t need those types of computational tools as part of my cancer research,” she explains. “But working at MIT was enlightening, because it showed me that they are key to understanding disease. I can definitely see myself using them on my own projects in the future.”

Pink and purple histology image
Light micrograph of a lung adenocarcinoma. Credit: Vasilena Gocheva/Jacks Lab, Koch Institute

The Jacks lab studies the genetic events that contribute to cancer, and Nelson’s project centered on lung adenocarcinoma. The predominant form of non-small cell lung cancer, it begins in alveolar type II (AT2) cells. Past studies showed that, as the tumor progresses, AT2 cells change state and lose their original identity. Nelson wanted to determine which genes and proteins underlie this evolution. Her analyses showed that genetic markers characteristic of AT2 cells tend to decrease over time, while markers denoting faster-growing “high grade” tumors become more prevalent.

“The kinetics of these gene expression changes that are happening early on are still poorly understood,” she explains. “It just goes to show how complicated this pathology is, which I find even more fascinating.”

Once researchers can pinpoint the genes and proteins that drive changes in cancer cell state, they’ll be better equipped to design drugs that target and prevent metastatic processes.

Although Nelson couldn’t visit the lab in person, as on-campus research slowly began ramping up again, her graduate student mentor Amanda Cruz would show her around during their video conference calls. Cruz also helped Nelson explore the scientific literature, choose studies for the lab’s journal club, and perform computational analyses.

Given the unprecedented circumstances, Nelson says having a solid support system was key to her success. Nelson and her MSRP cohort also relied on one another for encouragement, and were each assigned a graduate student “pal” for guidance outside of lab.

“The program catered to our every need, and it’s structured to ensure that someone will always check up on you if you’re feeling alone,” Nelson says. “I never expected to get so much from this experience, especially because I’m not physically on campus. But what I learned this summer was so much more than I could ever have anticipated.”

Her time in the Jacks lab has solidified her fervor for cancer research, and she intends to apply to cancer biology PhD programs in order to continue this line of inquiry. “I’ve realized there’s still so much more to learn,” she says, “but we’re getting there.”

Top image courtesy of Toni-Ann Nelson
Posted: 8.19.20
SMART research enhances dengue vaccination in mice
Singapore-MIT Alliance for Research and Technology
August 13, 2020

Researchers from the Singapore-MIT Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore, have found a practical way to induce a strong and broad immunity to the dengue virus based on proof-of-concept studies in mice. Dengue is a mosquito-borne viral disease with an estimated 100 million symptomatic infections every year. It is endemic in over 100 countries in the world, from the United States to Africa and wide swathes of Asia. In Singapore, over 1,700 dengue new cases were reported recently.

The study is reported in a paper titled “Sequential immunization induces strong and broad immunity against all four dengue virus serotypes,” published in NPJ Vaccines. It is jointly published by SMART researchers Jue Hou, Shubham Shrivastava, Hooi Linn Loo, Lan Hiong Wong, Eng Eong Ooi, and Jianzhu Chen from SMART’s Infectious Diseases and Antimicrobial Resistance (AMR) interdisciplinary research groups (IRGs).

The dengue virus (DENV) consists of four antigenically distinct serotypes and there is no lasting immunity following infection with any of the DENV serotypes, meaning someone can be infected again by any of the remaining three variants of DENVs.

Today, Dengvaxia is the only vaccine available to combat dengue. It consists of four variant dengue antigens, one for each of the four serotypes of dengue, expressed from attenuated yellow-fever virus. The current three doses of immunization with the tetravalent vaccine induce only suboptimal protection against DENV1 and DENV2. Furthermore, in people who have not been infected by dengue, the vaccine induces a more severe dengue infection in the future. Therefore, in most of the world, the vaccination is only given to those who have been previously infected.

To help overcome these issues, SMART researchers tested on mice whether sequential immunization (or one serotype per dose) induces stronger and broader immunity against four DENV serotypes than tetravalent-formulated immunization — and found that sequential immunization induced significantly higher levels of virus-specific T cell responses than tetravalent immunization. Moreover, sequential immunization induced higher levels of neutralizing antibodies to all four DENV serotypes than tetravalent vaccination.

“The principle of sequential immunization generally aligns with the reality for individuals living in dengue-endemic areas, whose immune responses may become protective after multiple heterotypic exposures,” says Professor Eng Eong Ooi, SMART AMR principal investigator and senior author of the study. “We were able to find a similar effect based on the use of sequential immunization, which will pave the way for a safe and effective use of the vaccine and to combat the virus.”

Upon these promising results, the investigators will aim to test the sequential immunization in humans in the near future.

The work was supported by the National Research Foundation (NRF) Singapore through the SMART Infectious Disease Research Program and AMR IRG. SMART was established by MIT in partnership with the NRF Singapore in 2007. SMART is the first entity in the Campus for Research Excellence and Technological Enterprise (CREATE) developed by NRF.  SMART serves as an intellectual and innovation hub for research interactions between MIT and Singapore, performing cutting-edge research of interest to both Singapore and MIT. SMART currently comprises an Innovation Centre and five IRGs: AMR, Critical Analytics for Manufacturing Personalized-Medicine, Disruptive and Sustainable Technologies for Agricultural Precision, Future Urban Mobility, and Low Energy Electronic Systems. SMART research is funded by the NRF Singapore under the CREATE program.

The AMR IRG is a translational research and entrepreneurship program that tackles the growing threat of antimicrobial resistance. By leveraging talent and convergent technologies across Singapore and MIT, they aim to tackle AMR head-on by developing multiple innovative and disruptive approaches to identify, respond to, and treat drug-resistant microbial infections. Through strong scientific and clinical collaborations, they provide transformative, holistic solutions for Singapore and the world.