Skip to main content

immunology

Teaching the Immune System to Attack Cancer with Greater Precision

Posted on by

Needle in a vial. Cancer cell in the background
Credit: PhotobyTawat/Shutterstock/Tom Deerink, National Institute of General Medical Sciences, NIH

To protect humans from COVID-19, the Pfizer and Moderna mRNA vaccines program human cells to translate the injected synthetic messenger RNA into the coronavirus spike protein, which then primes the immune system to arm itself against future appearances of that protein. It turns out that the immune system can also be trained to spot and attack distinctive proteins on cancer cells, killing them and leaving healthy cells potentially untouched.

While these precision cancer vaccines remain experimental, researchers continue to make basic discoveries that move the field forward. That includes a recent NIH-funded study in mice that helps to refine the selection of protein targets on tumors as a way to boost the immune response [1]. To enable this boost, the researchers first had to discover a possible solution to a longstanding challenge in developing precision cancer vaccines: T cell exhaustion.

The term refers to the immune system’s complement of T cells and their capacity to learn to recognize foreign proteins, also known as neoantigens, and attack them on cancer cells to shrink tumors. But these responding T cells can exhaust themselves attacking tumors, limiting the immune response and making its benefits short-lived.

In this latest study, published in the journal Cell, Tyler Jacks and Megan Burger, Massachusetts Institute of Technology, Cambridge, help to explain this phenomenon of T cell exhaustion. The researchers found in mice with lung tumors that the immune system initially responds as it should. It produces lots of T cells that target many different cancer-specific proteins.

Yet there’s a problem: various subsets of T cells get in each other’s way. They compete until, eventually, one of those subsets becomes the dominant T cell type. Even when those dominant T cells grow exhausted, they still remain in the tumor and keep out other T cells, which might otherwise attack different neoantigens in the cancer.

Building on this basic discovery, the researchers came up with a strategy for developing cancer vaccines that can “awaken” T cells and reinvigorate the body’s natural cancer-fighting abilities. The strategy might seem counterintuitive. The researchers vaccinated mice with neoantigens that provide a weak but encouraging signal to the immune cells responsible for presenting the distinctive cancer protein target, or antigen, to T cells. It’s those T cells that tend to get suppressed in competition with other T cells.

When the researchers vaccinated the mice with one of those neoantigens, the otherwise suppressed T cells grew in numbers and better targeted the tumor. What’s more, the tumors shrank by more than 25 percent on average.

Research on this new strategy remains in its early stages. The researchers hope to learn if this approach to cancer vaccines might work even better when used in combination with immunotherapy drugs, which unleash the immune system against cancer in other ways.

It’s also possible that the recent and revolutionary success of mRNA vaccines for preventing COVID-19 actually could help. An important advantage of mRNA is that it’s easy for researchers to synthesize once they know the specific nucleic acid sequence of a protein target, and they can even combine different mRNA sequences to make a multiplex vaccine that primes the immune system to recognize multiple neoantigens. Now that we’ve seen how well mRNA vaccines work to prompt a desired immune response against COVID-19, this same technology can be used to speed the development and testing of future vaccines, including those designed precisely to fight cancer.

Reference:

[1] Antigen dominance hierarchies shape TCF1+ progenitor CD8 T cell phenotypes in tumors. Burger ML, Cruz AM, Crossland GE, Gaglia G, Ritch CC, Blatt SE, Bhutkar A, Canner D, Kienka T, Tavana SZ, Barandiaran AL, Garmilla A, Schenkel JM, Hillman M, de Los Rios Kobara I, Li A, Jaeger AM, Hwang WL, Westcott PMK, Manos MP, Holovatska MM, Hodi FS, Regev A, Santagata S, Jacks T. Cell. 2021 Sep 16;184(19):4996-5014.e26.

Links:

Cancer Treatment Vaccines (National Cancer Institute/NIH)

The Jacks Lab (Massachusetts Institute of Technology, Cambridge)

NIH Support: National Cancer Institute; National Heart, Lung, and Blood Institute


The Hidden Beauty of Intestinal Villi

Posted on by

Credit: Amy Engevik, Medical University of South Carolina, Charleston.

The human small intestine, though modest in diameter and folded compactly to fit into the abdomen, is anything but small. It measures on average about 20 feet from end to end and plays a big role in the gastrointestinal tract, breaking down food and drink from the stomach to absorb the water and nutrients.

Also anything but small is the total surface area of the organ’s inner lining, where millions of U-shaped folds in the mucosal tissue triple the available space to absorb the water and nutrients that keep our bodies nourished. If these folds, packed with finger-like absorptive cells called villi, were flattened out, they would be the size of a tennis court!

That’s what makes this this microscopic image so interesting. It shows in cross section the symmetrical pattern of the villi (its cells outlined by yellow) that pack these folds. Each cell’s nucleus contains DNA (teal), and the villi themselves are fringed by thousands of tiny bristles, called microvilli (magenta), which are too small to see individually here. Collectively, microvilli make up an absorptive surface, called the brush border, where digested nutrients in the fluid passing through the intestine can enter cells via transport channels.

Amy Engevik, a researcher at the Medical University of South Carolina, Charleston, took this snapshot to show what a healthy intestinal cellular landscape looks like in a young mouse. The Engevik lab studies the dynamic movement of ions, water, and proteins in the intestine—a process that goes wrong in humans born with a rare disorder called microvillus inclusion disease (MVID).

MVID causes chronic gastrointestinal problems in newborn babies, due to defects in a protein that transports various cellular components. Because they cannot properly absorb nutrition from food, these tiny patients require intravenous feeding almost immediately, which carries a high risk for sepsis and intestinal injury.

Engevik and her team study this disease using a mouse model that replicates many of the characteristics of the disorder in humans [1]. Interestingly, when Engevik gets together with her family, she isn’t the only one talking about MVID and villi. Her two sisters, Mindy and Kristen, also study the basic science of gastrointestinal disorders! Instead of sibling rivalry, though, this close alliance has strengthened the quality of her research, says Amy, who is the middle child.

Beyond advancing science and nurturing sisterhood in science, Engevik’s work also captured the fancy of the judges for the Federation of American Societies for Experimental Biology’s annual BioArt Scientific Image and Video Competition. Her image was one of 10 winners announced in December 2020.

Because multiple models are useful for understanding fundamentals of diseases like MVID, Engevik has also developed a large-animal model (pig) that has many features of the human disease [2]. She hopes that her efforts will help to improve our understanding of MVID and other digestive diseases, as well as lead to new, potentially life-saving treatments for babies suffering from MVID.

References:

[1] Loss of MYO5B Leads to reductions in Na+ absorption with maintenance of CFTR-dependent Cl- secretion in enterocytes. Engevik AC, Kaji I, Engevik MA, Meyer AR, Weis VG, Goldstein A, Hess MW, Müller T, Koepsell H, Dudeja PK, Tyska M, Huber LA, Shub MD, Ameen N, Goldenring JR. Gastroenterology. 2018 Dec;155(6):1883-1897.e10.

[2] Editing myosin VB gene to create porcine model of microvillus inclusion disease, with microvillus-lined inclusions and alterations in sodium transporters. Engevik AC, Coutts AW, Kaji I, Rodriguez P, Ongaratto F, Saqui-Salces M, Medida RL, Meyer AR, Kolobova E, Engevik MA, Williams JA, Shub MD, Carlson DF, Melkamu T, Goldenring JR. Gastroenterology. 2020 Jun;158(8):2236-2249.e9.

Links:

Microvillus inclusion disease (Genetic and Rare Diseases Center/NIH)

Digestive Diseases (National Institute of Diabetes and Digestive and Kidney Diseases/NIH)

Amy Engevik (Medical University of South Carolina, Charleston)

Podcast: A Tale of Three Sisters featuring Drs. Mindy, Amy, and Kristen Engevik (The Immunology Podcast, April 29, 2021)

BioArt Scientific Image and Video Competition (Federation of American Societies for Experimental Biology, Bethesda, MD)

NIH Support: National Institute of Diabetes and Digestive and Kidney Diseases


Immune Macrophages Use Their Own ‘Morse Code’

Posted on by

Credit: Hoffmann Lab, UCLA

In the language of Morse code, the letter “S” is three short sounds and the letter “O” is three longer sounds. Put them together in the right order and you have a cry for help: S.O.S. Now an NIH-funded team of researchers has cracked a comparable code that specialized immune cells called macrophages use to signal and respond to a threat.

In fact, by “listening in” on thousands of macrophages over time, one by one, the researchers have identified not just a lone distress signal, or “word,” but a vocabulary of six words. Their studies show that macrophages use these six words at different times to launch an appropriate response. What’s more, they have evidence that autoimmune conditions can arise when immune cells misuse certain words in this vocabulary. This bad communication can cause them incorrectly to attack substances produced by the immune system itself as if they were a foreign invaders.

The findings, published recently in the journal Immunity, come from a University of California, Los Angeles (UCLA) team led by Alexander Hoffmann and Adewunmi Adelaja. As an example of this language of immunity, the video above shows in both frames many immune macrophages (blue and red). You may need to watch the video four times to see what’s happening (I did). Each time you run the video, focus on one of the highlighted cells (outlined in white or green), and note how its nuclear signal intensity varies over time. That signal intensity is plotted in the rectangular box at the bottom.

The macrophages come from a mouse engineered in such a way that cells throughout its body light up to reveal the internal dynamics of an important immune signaling protein called nuclear NFκB. With the cells illuminated, the researchers could watch, or “listen in,” on this important immune signal within hundreds of individual macrophages over time to attempt to recognize and begin to interpret potentially meaningful patterns.

On the left side, macrophages are responding to an immune activating molecule called TNF. On the right, they’re responding to a bacterial toxin called LPS. While the researchers could listen to hundreds of cells at once, in the video they’ve randomly selected two cells (outlined in white or green) on each side to focus on in this example.

As shown in the box in the lower portion of each frame, the cells didn’t respond in precisely the same way to the same threat, just like two people might pronounce the same word slightly differently. But their responses nevertheless show distinct and recognizable patterns. Each of those distinct patterns could be decomposed into six code words. Together these six code words serve as a previously unrecognized immune language!

Overall, the researchers analyzed how more than 12,000 macrophage cells communicated in response to 27 different immune threats. Based on the possible arrangement of temporal nuclear NFκB dynamics, they then generated a list of more than 900 pattern features that could be potential “code words.”

Using an algorithm developed decades ago for the telecommunications industry, they then monitored which of the potential words showed up reliably when macrophages responded to a particular threatening stimulus, such as a bacterial or viral toxin. This narrowed their list to six specific features, or “words,” that correlated with a particular response.

To confirm that these pattern features contained meaning, the team turned to machine learning. If they taught a computer just those six words, they asked, could it distinguish the external threats to which the computerized cells were responding? The answer was yes.

But what if the computer had five words available, instead of six? The researchers found that the computer made more mistakes in recognizing the stimulus, leading the team to conclude that all six words are indeed needed for reliable cellular communication.

To begin to explore the implications of their findings for understanding autoimmune diseases, the researchers conducted similar studies in macrophages from a mouse model of Sjögren’s syndrome, a systemic condition in which the immune system often misguidedly attacks cells that produce saliva and tears. When they listened in on these cells, they found that they used two of the six words incorrectly. As a result, they activated the wrong responses, causing the body to mistakenly perceive a serious threat and attack itself.

While previous studies have proposed that immune cells employ a language, this is the first to identify words in that language, and to show what can happen when those words are misused. Now that researchers have a list of words, the next step is to figure out their precise definitions and interpretations [2] and, ultimately, how their misuse may be corrected to treat immunological diseases.

References:

[1] Six distinct NFκB signaling codons convey discrete information to distinguish stimuli and enable appropriate macrophage responses. Adelaja A, Taylor B, Sheu KM, Liu Y, Luecke S, Hoffmann A. Immunity. 2021 May 11;54(5):916-930.e7.

[2] NF-κB dynamics determine the stimulus specificity of epigenomic reprogramming in macrophages. Cheng QJ, Ohta S, Sheu KM, Spreafico R, Adelaja A, Taylor B, Hoffmann A. Science. 2021 Jun 18;372(6548):1349-1353.

Links:

Overview of the Immune System (National Institute of Allergy and Infectious Diseases/NIH)

Sjögren’s Syndrome (National Institute of Dental and Craniofacial Research/NIH)

Alexander Hoffmann (UCLA)

NIH Support: National Institute of General Medical Sciences; National Institute of Allergy and Infectious Diseases


Human Antibodies Target Many Parts of Coronavirus Spike Protein

Posted on by

Viral spike with labels Receptor-binding domain (RBD) antibody, N-terminal domain (NTD) antibody, S2 subunit antibody
Caption: People who recovered from mild COVID-19 infections produced antibodies circulating in their blood that target three different parts of the coronavirus’s spike protein (gray). Credit: University of Texas at Austin

For many people who’ve had COVID-19, the infections were thankfully mild and relatively brief. But these individuals’ immune systems still hold onto enduring clues about how best to neutralize SARS-CoV-2, the coronavirus that causes COVID-19. Discovering these clues could point the way for researchers to design highly targeted treatments that could help to save the lives of folks with more severe infections.

An NIH-funded study, published recently in the journal Science, offers the most-detailed picture yet of the array of antibodies against SARS-CoV-2 found in people who’ve fully recovered from mild cases of COVID-19. This picture suggests that an effective neutralizing immune response targets a wider swath of the virus’ now-infamous spike protein than previously recognized.

To date, most studies of natural antibodies that block SARS-CoV-2 have zeroed in on those that target a specific portion of the spike protein known as the receptor-binding domain (RBD)—and with good reason. The RBD is the portion of the spike that attaches directly to human cells. As a result, antibodies specifically targeting the RBD were an excellent place to begin the search for antibodies capable of fending off SARS-CoV-2.

The new study, led by Gregory Ippolito and Jason Lavinder, The University of Texas at Austin, took a different approach. Rather than narrowing the search, Ippolito, Lavinder, and colleagues analyzed the complete repertoire of antibodies against the spike protein from four people soon after their recoveries from mild COVID-19.

What the researchers found was a bit of a surprise: the vast majority of antibodies—about 84 percent—targeted other portions of the spike protein than the RBD. This suggests a successful immune response doesn’t concentrate on the RBD. It involves production of antibodies capable of covering areas across the entire spike.

The researchers liken the spike protein to an umbrella, with the RBD at the tip of the “canopy.” While some antibodies do bind RBD at the tip, many others apparently target the protein’s canopy, known as the N-terminal domain (NTD).

Further study in cell culture showed that NTD-directed antibodies do indeed neutralize the virus. They also prevented a lethal mouse-adapted version of the coronavirus from infecting mice.

One reason these findings are particularly noteworthy is that the NTD is one part of the viral spike protein that has mutated frequently, especially in several emerging variants of concern, including the B.1.1.7 “U.K. variant” and the B.1.351 “South African variant.” It suggests that one reason these variants are so effective at evading our immune systems to cause breakthrough infections, or re-infections, is that they’ve mutated their way around some of the human antibodies that had been most successful in combating the original coronavirus variant.

Also noteworthy, about 40 percent of the circulating antibodies target yet another portion of the spike called the S2 subunit. This finding is especially encouraging because this portion of SARS-CoV-2 does not seem as mutable as the NTD segment, suggesting that S2-directed antibodies might offer a layer of protection against a wider array of variants. What’s more, the S2 subunit may make an ideal target for a possible pan-coronavirus vaccine since this portion of the spike is widely conserved in SARS-CoV-2 and related coronaviruses.

Taken together, these findings will prove useful for designing COVID-19 vaccine booster shots or future vaccines tailored to combat SARS-COV-2 variants of concern. The findings also drive home the conclusion that the more we learn about SARS-CoV-2 and the immune system’s response to neutralize it, the better position we all will be in to thwart this novel coronavirus and any others that might emerge in the future.

Reference:

[1] Prevalent, protective, and convergent IgG recognition of SARS-CoV-2 non-RBD spike epitopes. Voss WN, Hou YJ, Johnson NV, Delidakis G, Kim JE, Javanmardi K, Horton AP, Bartzoka F, Paresi CJ, Tanno Y, Chou CW, Abbasi SA, Pickens W, George K, Boutz DR, Towers DM, McDaniel JR, Billick D, Goike J, Rowe L, Batra D, Pohl J, Lee J, Gangappa S, Sambhara S, Gadush M, Wang N, Person MD, Iverson BL, Gollihar JD, Dye J, Herbert A, Finkelstein IJ, Baric RS, McLellan JS, Georgiou G, Lavinder JJ, Ippolito GC. Science. 2021 May 4:eabg5268.

Links:

COVID-19 Research (NIH)

Gregory Ippolito (University of Texas at Austin)

NIH Support: National Institute of Allergy and Infectious Diseases; National Cancer Institute; National Institute of General Medical Sciences; National Center for Advancing Translational Sciences


Finding New Ways to Fight Coronavirus … From Studying Bats

Posted on by

David Veesler/Credit: University of Washington Medicine, Seattle
 

David Veesler has spent nearly 20 years imaging in near-atomic detail the parts of various viruses, including coronaviruses, that enable them to infect Homo sapiens. In fact, his lab at the University of Washington, Seattle, was the first to elucidate the 3D architecture of the now infamous spike protein, which coronaviruses use to gain entry into human cells [1]. He uses these fundamental insights to guide the design of vaccines and therapeutics, including promising monoclonal antibodies.

Now, Veesler and his lab are turning to another mammal in their search for new leads for the next generation of antiviral treatments, including ones aimed at the coronavirus that causes COVID-19, SARS-CoV-2. With support from a 2020 NIH Director’s Pioneer Award, Veesler will study members of the order Chiroptera. Or, more colloquially, bats.

Why bats? Veesler says bats are remarkable creatures. They are the only mammals capable of sustained flight. They rarely get cancer and live unusually long lives for such small creatures. More importantly for Veesler’s research, bats host a wide range of viruses—more than any other mammal species. Despite carrying all of these viruses, bats rarely show symptoms of being sick. Yet they are the source for many of the viruses that have spilled over into humans with devastating effect, including rabies, Ebola virus, Nipah and Hendra viruses, severe acute respiratory syndrome coronavirus (SARS-CoV), and, likely, SARS-CoV-2.

Beyond what is already known about bats’ intriguing qualities, Veesler says humans still have much to discover about these flying mammals, including how their immune systems cope with such an onslaught of viral invaders. For example, it turns out that a bat’s learned, or adaptive, immune system is, for the most part, uncharted territory. As such, it offers an untapped source of potentially promising viral inhibitors just waiting to be unearthed, fully characterized, and then used to guide the development of new kinds of anti-viral therapeutics.

In his studies, Veesler will work with collaborators studying bats around the world to characterize their antibody production. He wants to learn how these antibodies contribute to bats’ impressive ability to tolerate viruses and other pathogens. What is it about the structure of bat antibodies that make them different from human antibodies? And, how can those structural differences serve as blueprints for promising new treatments to combat many potentially deadly viruses?

Interestingly, Veesler’s original grant proposal makes no mention of SARS-CoV-2 or COVID-19. That’s because he submitted it just months before the first reports of the novel coronavirus in Wuhan, China. But Veesler doesn’t consider himself a visionary by expanding his research to bats. He and others had been working on closely related coronaviruses for years, inspired by earlier outbreaks, including SARS in 2002 and Middle East respiratory syndrome (MERS) in 2012 (although MERS apparently came from camels). The researcher didn’t see SARS-CoV-2 coming, but he recognized the potential for some kind of novel coronavirus outbreak in the future.

These days, the Veesler lab has been hard at work to understand SARS-CoV-2 and the human immune response to the virus. His team showed that SARS-CoV-2 uses the human receptor ACE2 to gain entry into our cells [2]. He’s also a member of the international research team that identified a human antibody, called S309, from a person who’d been infected with SARS in 2003. This antibody is showing promise for treating COVID-19 [3], now in a phase 3 clinical trial in the United States.

In another recent study, reported as a pre-print in bioRxiv, Veesler’s team mapped dozens of distinct human antibodies capable of neutralizing SARS-CoV-2 by their ability to hit viral targets outside of the well-known spike protein [4]. Such discoveries may form the basis for new and promising combinations of antibodies to treat COVID-19 that won’t be disabled by concerning new variations in the SARS-CoV-2 spike protein. Perhaps, in the future, such therapeutic cocktails may include modified bat-inspired antibodies too.

References:

[1] Cryo-electron microscopy structure of a coronavirus spike glycoprotein trimer. Walls AC, Tortorici MA, Bosch BJ, Frenz B, Rottier PJM, DiMaio F, Rey FA, Veesler D. Nature. 2016 Mar 3;531(7592):114-117.

[2] Structure, function, and antigenicity of the SARS-CoV-2 spike glycoprotein. Walls AC, Park YJ, Tortorici MA, Wall A, McGuire AT, Veesler D. Cell. 2020 Apr 16;181(2):281-292.e6.

[3] Cross-neutralization of SARS-CoV-2 by a human monoclonal SARS-CoV antibody. Pinto D, Park YJ, Beltramello M, Veesler D, Cortil D, et al. Nature.18 May 2020 [Epub ahead of print]

[4] N-terminal domain antigenic mapping reveals a site of vulnerability for SARS-CoV-2. McCallum M, Marco A, Lempp F, Tortorici MA, Pinto D, Walls AC, Whelan SPJ, Virgin HW, Corti D, Pizzuto MS, Veesler D, et al. bioRxiv. 2021 Jan 14.

Links:

COVID-19 Research (NIH)

Veesler Lab (University of Washington, Seattle)

Veesler Project Information (NIH RePORTER)

NIH Director’s Pioneer Award Program (Common Fund)

NIH Support: Common Fund; National Institute of Allergy and Infectious Diseases


Next Page