Category: Immune System

New Discovery Explains How SARS-CoV-2 Evades Anti-viral Immunity

Image by Fusion Medical on Unsplash

The novel coronavirus SARS-CoV-2 has an enzyme that can counteract a cell’s innate defence mechanism against viruses, explaining why it is more infectious than the previous SARS and MERS-causing viruses. This discovery, from Kobe University, may point the way to the development of more effective drugs against this and possibly similar, future diseases.

When a virus attacks, the body’s immune response has two basic layers of defence: the innate and the adaptive immune systems. While the adaptive immune system grows stronger against a specific pathogen as the body is exposed to it multiple times and which forms the basis of vaccinations, the innate immune system is an assortment of molecular mechanisms that work against a broad range of pathogens at a basic level. The Kobe University virologist SHOJI Ikuo says, “The new coronavirus, however, is so infectious that we wondered what clever mechanisms the virus employs to evade the innate immune system so effectively.”

Shoji’s team previously worked on the immune response to hepatitis viruses and investigated the role of a molecular tag called “ISG15” the innate immune system attaches to the virus’s building blocks. Having learned that the novel coronavirus has an enzyme that is especially effective in removing this tag, he decided to use his team’s expertise to elucidate the effect of the ISG15 tag on the coronavirus and the mechanism of the virus’s countermeasures.

In a paper in the Journal of Virology, the Kobe University-led team is now the first to report that the ISG15 tag gets attached to a specific location on the virus’s nucleocapsid protein, the scaffold that packages the pathogen’s genetic material. For the virus to assemble, many copies of the nucleocapsid protein need to attach to each other, but the ISG15 tag prevents this, which is the mechanism behind the tag’s antiviral action. “However, the novel coronavirus also has an enzyme that can remove the tags from its nucleocapsid, recovering its ability to assemble new viruses and thus overcoming the innate immune response,” explains Shoji.

The novel coronavirus shares many traits with the SARS and MERS viruses, which all belong to the same family of viruses – which also have an enzyme that can remove the ISG15 tag. But their versions are less efficient at it than the one in the novel coronavirus, Shoji’s team found. And in fact, it has been reported recently that the previous viruses’ enzymes have a different primary target. “These results suggest that the novel coronavirus is simply better at evading this aspect of the innate immune system’s defence mechanism, which explains why it is so infectious,” says Shoji.

But understanding just why the novel coronavirus is so effective also points the way to developing more effective treatments. The Kobe University researcher explains: “We may be able to develop new antiviral drugs if we can inhibit the function of the viral enzyme that removes the ISG15 tag. Future therapeutic strategies may also include antiviral agents that directly target the nucleocapsid protein, or a combination of these two approaches.”

Source: Kobe University

“Two for the Price of One” – New Process that Drives Anti-viral Immunity is Discovered

Scientists at Trinity College Dublin have discovered a new process in the immune system that leads to the production of an important family of anti-viral proteins called interferons. They hope the discovery will now lead to new, effective therapies for people with some autoimmune and infectious diseases.

Reporting in Nature Metabolism, Luke O’Neill, Professor of Biochemistry in the School of Biochemistry and Immunology at Trinity, and his team have found that a natural metabolite called Itaconate can stimulate immune cells to make interferons by blocking an enzyme called SDH. 

Co-lead author, Shane O’Carroll, from Trinity’s School of Biochemistry and Immunology, said: “We have linked the enzyme SDH to the production of interferons in an immune cell type called the macrophage. We hope our work will help the effort to develop better strategies to fight viruses because interferons are major players in how our innate immune system eliminates viruses – including COVID-19.” 

Co-lead author, Christian Peace, from Trinity’s School of Biochemistry and Immunology, added: “Itaconate is a fascinating molecule made by macrophages during infections. It’s already known to suppress damaging inflammation but now we have found how it promotes anti-viral interferons.”

Working with drug companies Eli Lilly and Sitryx Ltd, the next step is to test new therapies  based on Itaconate in various diseases, with some autoimmune diseases and some infectious diseases on the likely list. And the work potentially extends to other disease contexts in which SDH is inhibited, such as cancer, and could reveal a new therapeutic target for SDH-deficient tumours.

Prof O’Neill said: “With Itaconate you get two for the price of one – not only can it block harmful inflammation, but it can also help fight infections. We have discovered important mechanisms for both and the hope now is that patients will benefit from new therapies that exploit Itaconate and its impacts.” 

Clinical trials in patients are set to start next year.  

Source: Trinity College Dublin

Rip and Tear: How a Key Immune Protein Defeats Bacterial Membranes

Illustration of how GBP1 proteins (blue and purple) attach to the membrane of a bacterium (yellow), zoomed in from an image taken with an electron microscope (in grayscale). Credit: Delft University

The protein GBP1 is a vital immune system component which fights against bacteria and parasites by enveloping them in a protein coat, but how the substance manages to do this has remained unknown until now. Researchers from Delft University of Technology report in Nature Structural & Molecular Biology how this protein operates – ripping and tearing until the bacterial membrane is undone. Their findings could aid in the development of medications and therapies for individuals with weakened immune systems.

So-called Guanylate Binding Proteins (GBPs) play a crucial role in our innate immune system, explains biophysicist Arjen Jakobi: “GBPs form the first line of defence against various infectious diseases caused by bacteria and parasites. Examples of such diseases include dysentery, typhoid fever caused by Salmonella bacteria, and tuberculosis. The protein also plays a significant role in the sexually transmitted infection chlamydia as well as in toxoplasmosis, which is particularly dangerous during pregnancy and for unborn children.”

Coat around bacteria

In their publication, Jakobi and his colleagues describe for the first time how the innate immune system fights against bacteria using GBP1 proteins. “The protein surrounds bacteria by forming a sort of coat around them,” explains Tanja Kuhm, PhD candidate in Jakobi’s research group and the lead author of the article. “By pulling this coat tighter, it breaks the membrane of the bacteria – the protective layer surrounding the intruder – after which immune cells can clear the infection.”

Deciphering the defence strategy

To decode the defence strategy of GBPs, the researchers examined how GBP1 proteins bind to bacterial membranes using a cryogenic electron microscope. This allowed them to see the process in great detail down to the molecular level. Jakobi: “We were able to obtain a detailed three-dimensional image of how the protein coat forms. Together with biophysical experiments conducted in Sander Tans’ research group at research institute AMOLF, which enabled us to manipulate the system precisely, we succeeded in deciphering the mechanism of the antibacterial function.”

Medications

According to Jakobi, this research helps us understand better how our body is capable of combating bacterial infections. “If we can grasp this well, and we can specifically activate or deactivate the involved proteins through medication, it may offer opportunities to speed up getting rid of certain infections.”

Source: Delft University

New Approach to MS ‘Teaches’ Immune Cells not to Attack

Myelin sheath damage. Credit: Scientific Animations CC4.0

Researchers from have found a potential new way to improve the treatment of multiple sclerosis (MS) using a novel combined therapy. The results, published in the Journal of Clinical Investigation, builds on two harmonised Phase I clinical trials, focusing on the use of Vitamin D3 tolerogenic dendritic cells (VitD3-tolDCs) to regulate the immune response in MS patient.

Multiple Sclerosis (MS) is a long-term disease where the immune system mistakenly attacks the protective myelin sheath around nerve cells. This leads to nerve damage and worsening disability. Current treatments, like immunosuppressants, help reduce these harmful attacks but also weaken the overall immune system, leaving patients vulnerable to infections and cancer. Scientists are now exploring a more targeted therapy using special immune cells, called tolerogenic dendritic cells (tolDCs), from the same patients.

TolDCs can restore immune balance without affecting the body’s natural defences. However, since a hallmark of MS is precisely the dysfunction of the immune system, the effectiveness of these cells for auto transplantation might be compromised. Therefore, it is essential to better understand how the disease affects the starting material for this cellular therapy before it can be applied.

In this study, researchers from Barcelona’s Germans Trias i Pujol Institute and Josep Carreras Leukaemia Research Institute, examined CD14+ monocytes, mature dendritic cells (mDCs), and Vitamin D3-treated tolerogenic dendritic cells (VitD3-tolDCs) from MS patients who had not yet received treatment, as well as from healthy individuals. The clinical trials (NCT02618902 and NCT02903537) are designed to assess the effectiveness of VitD3-tolDCs, which are loaded with myelin antigens to help “teach” the immune system to stop attacking the nervous system. This approach is groundbreaking as it uses a patient’s own immune cells, modified to induce immune tolerance, in an effort to treat the autoimmune nature of MS.

The study, led by Dr Eva Martinez-Cáceres and Dr Esteban Ballestar, with Federico Fondelli as first author, found that the immune cells from MS patients (monocytes, precursors of tolDCs) have a persistent “pro-inflammatory” signature, even after being transformed into VitD3-tolDCs, the actual therapeutic cell type. This signature makes these cells less effective compared to those derived from healthy individuals, missing part of its potential benefits.

Using state-of-the-art research methodologies, the researchers identified a pathway, known as the Aryl Hydrocarbon Receptor (AhR), that is linked to this altered immune response. By using an AhR-modulating drug, the team was able to restore the normal function of VitD3-tolDCs from MS patients, in vitro. Interestingly, Dimethyl Fumarate, an already approved MS drug, was found to mimic the effect of AhR modulation and restore the cells’ full efficacy, with a safer toxic profile.

Finally, studies in MS animal models showed that a combination of VitD3-tolDCs and Dimethyl Fumarate led to better results than using either treatment on its own. This combination therapy significantly reduced symptoms in mice, suggesting enhanced potential for treating human patients.

These results could lead to a new, more potent treatment option for multiple sclerosis, offering hope to the millions of patients worldwide who suffer from this debilitating disease. This study represents a significant step forward in the use of personalised cell therapies for autoimmune diseases, potentially revolutionising how multiple sclerosis is treated.

The team is now preparing to move into Phase II trials to further explore these findings.

Source: Josep Carreras Leukaemia Research Institute

New Treatment for Pregnancy Loss Caused by Specific Autoantibody

Photo by SHVETS production

Amongst women who experience recurrent pregnancy loss, around 20% test positive for a specific autoantibody. A Kobe University-led research team now found a treatment using either of two common drugs that drastically increases these women’s chances of carrying to full-term without complications, reporting their findings in Frontiers in Immunology.

Recurrent pregnancy loss is a condition of women who have lost two or more pregnancies for non-obvious reasons. Kobe University obstetrician Tanimura Kenji and his team have previously found that in 20% of these women, they can detect a specific antibody in their blood that targets their own bodies: anti-β2-glycoprotein I/HLA-DR autoantibodies.

Tanimura explains: “There is no known treatment for this particular condition, but the antibodies have a similar target to those that play a role in a different condition that has an established treatment.” Therefore, he wanted to test whether that treatment also works in the cases with the newly discovered antibody.

Tanimura enlisted the help of obstetricians across five hospitals in Japan and over the course of two years analysed the blood of consenting women suffering from recurrent pregnancy loss for the antibodies. If any of these women got pregnant during this time frame, their doctors would offer treatment options also containing those drugs that are effective against the chemically similar condition, specifically, low-dose aspirin or heparin. The research team then observed how many of the women who included these drugs in their treatment had full-term live births or pregnancy complications and compared that to the pregnancy outcomes in women who did not take either of the two drugs.

They report that women who received the treatment were much more likely to have live births (87% did) compared to the ones without treatment (of which only 50% had live births). In addition, amongst the live births, the treatment reduced the likelihood of complications from 50% to 6%. “The sample size was rather small (39 women received the treatment and 8 did not), but the results still clearly show that a treatment with low-dose aspirin or heparin is very effective in preventing pregnancy loss or complications also in women who have these newly discovered self-targeting antibodies,” summarises Tanimura.

Many women who tested positive for the newly discovered self-targeting antibodies also tested positive for the previously known ones. However, the Kobe University-led team found that women who only had the newly discovered antibodies and who received the treatment were even more likely to have a live birth (93%) and, amongst these, none had pregnancy complications.

Looking ahead, Tanimura says: “The newly discovered self-targeting antibody has been demonstrated to be involved also in infertility and recurrent implantation failure, as well as a risk factor for arterial thrombosis in women with systemic rheumatic diseases. I therefore expect that studies about the effectivity of the treatment against a broader range of conditions might produce encouraging results.”

Source: Kobe University

Fever Drives Enhanced Activity and Mitochondrial Damage in Immune Cells

Photo by Kelly Sikkema on Unsplash

Fever temperatures accelerate immune cell metabolism, proliferation and activity, but in a particular subset of T cells, it also causes mitochondrial stress, DNA damage and cell death, Vanderbilt University Medical Center researchers have discovered. 

The findings, published in the journal Science Immunology, offer a mechanistic understanding for how cells respond to heat and could explain how chronic inflammation contributes to the development of cancer. 

The impact of fever temperatures on cells is a relatively understudied area, said Jeff Rathmell, PhD, Professor of Immunobiology and corresponding author of the new study. Most of the existing temperature-related research relates to agriculture and how extreme temperatures impact crops and livestock, he noted. It’s challenging to change the temperature of animal models without causing stress, and cells in the laboratory are generally cultured in incubators that are set at human body temperature: 37°C. 

“Standard body temperature is not actually the temperature for most inflammatory processes, but few have really gone to the trouble to see what happens when you change the temperature,” said Rathmell, who also directs the Vanderbilt Center for Immunobiology

Graduate student Darren Heintzman was interested in the impact of fevers for personal reasons: Before he joined the Rathmell lab, his father developed an autoimmune disease and had a constant fever for months on end. 

“I started thinking about what an increased set point temperature like that might do. It was intriguing,” Heintzman said. 

Heintzman cultured immune system T cells at 39°C. He found that heat increased helper T cell metabolism, proliferation and inflammatory effector activity and decreased regulatory T cell suppressive capacity. 

“If you think about a normal response to infection, it makes a lot of sense: You want effector (helper) T cells to be better at responding to the pathogen, and you want suppressor (regulatory) T cells to not suppress the immune response,” Heintzman said. 

But the researchers also made an unexpected discovery: that a certain subset of helper T cells, called Th1 cells, developed mitochondrial stress and DNA damage, and some of them died. The finding was confusing, the researchers said, because Th1 cells are involved in settings where there is often fever, like viral infections. Why would the cells that are needed to fight the infection die? 

The researchers discovered that only a portion of the Th1 cells die, and that the rest undergo an adaptation, change their mitochondria, and become more resistant to stress. 

“There’s a wave of stress, and some of the cells die, but the ones that adapt and survive are better – they proliferate more and make more cytokine (immune signaling molecules),” Rathmell said.

Heintzman was able to define the molecular events of the cell response to fever temperatures. He found that heat rapidly impaired electron transport chain complex 1 (ETC1), a mitochondrial protein complex that generates energy. ETC1 impairment set off signalling mechanisms that led to DNA damage and activation of the tumour suppressor protein p53, which aids DNA repair or triggers cell death to maintain genome integrity. Th1 cells were more sensitive to impaired ETC1 than other T cell subtypes.

 The researchers found Th1 cells with similar changes in sequencing databases for samples from patients with Crohn’s disease and rheumatoid arthritis, adding support to the molecular signaling pathway they defined. 

“We think this response is a fundamental way that cells can sense heat and respond to stress,” Rathmell said. “Temperature varies across tissues and changes all the time, and we don’t really know what it does. If temperature changes shift the way cells are forced to do metabolism because of ETC1, that’s going to have a big impact. This is fundamental textbook kind of stuff.” 

The findings suggest that heat can be mutagenic, when cells that respond with mitochondrial stress don’t properly repair the DNA damage or die. 

“Chronic inflammation with sustained periods of elevated tissue temperatures could explain how some cells become tumorigenic,” Heintzman said, noting that up to 25% of cancers are linked to chronic inflammation. 

“People ask me, ‘Is fever good or bad?’” Rathmell added. “The short answer is: A little bit of fever is good, but a lot of fever is bad. We already knew that, but now we have a mechanism for why it’s bad.” 

Source: Vanderbilt University Medical Center

Immune Cell Specialises its Roles in Different Tissues

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A newly published study in the scientific journal Science Immunology has investigating how MAIT cells (mucosa-associated invariant T cells) behave in different tissues. The Karolinska Institutet study shows that these immune cells, which play an important role in the body’s defence against microbes, exhibit different properties depending on the tissue they are in.

MAIT cells are a type of T cell that recognise by-products formed when microbes synthesise riboflavin. This makes them unique in the way they detect and fight infections. The researchers examined MAIT cells from blood, barrier tissues and lymphoid tissue samples from organ donors to understand how these cells function in different tissues.

Different MAIT cells in intestines and liver

“We found that MAIT cells in the intestines have a specialised immunoregulatory profile with high expression of the regulatory enzyme CD39, suggesting that they play a role in protecting the intestinal barrier,” says Johan Sandberg, Professor at the Center for Infectious Medicine (CIM), at the Department of Medicine, Huddinge, Karolinska Institutet.

“In the liver, on the other hand, MAIT cells predominantly exhibit high expression of the marker CD56 and an increased ability to fight microbes.”

The study also shows that the number of MAIT cells in the blood decreases with age but is preserved in the tissues. At the same time, tissue-adapted functions in the intestines and liver become increasingly evident with age.

“Our results highlight the functional heterogeneity of MAIT cells and their adaptation to different tissues.”

The results of the study add a new dimension to the understanding of the immune system and how different types of immune cells specialise to protect different tissues against infections.

“This gives us a better understanding of how this arm of the immune system works and can help us develop new treatments for infectious diseases,” says Johan Sandberg.

Source: Karolinska Institutet

How Cancer Reprograms Immune Cells to Join the Enemy

Squamous cancer cell being attacked by cytotoxic T cells. Image by National Cancer Institute on Unsplash

Cancer has been described as “a wound that does not heal,” implying that the immune system is unable to wipe out invading tumour cells. A new discovery reported in PNAS confirms that a key molecule can reprogram immune cells into turncoats that promote cancer growth.

Studying the behaviour of these “pro-tumour” immune cells is important because they could be targets for therapies that block their harmful activity, said Minsoo Kim, PhD, corresponding author of the study and a research leader at the Wilmot Cancer Institute.

Kim led a team of scientists investigating the dynamic interactions that occur between cells in the tumor environment, and the underlying factors that cause the harmful transformation of immune cells from good to bad.

They found that PAF (platelet-activating factor) is the key molecule that controls the destiny of the immune cells. PAF not only recruits cancer-promoting cells, but it also suppresses the immune system’s ability to fight back. In addition, they found that multiple cancers rely on the same PAF signals.

“This is what could be most significant,” said Kim. “Because if we find a treatment that could interfere with PAF, it could potentially apply to many types of cancer.”

Much of the team’s work focused on pancreatic cancer cells. It is one of the most deadly cancers, with a five-year survival rate of about 12%, and is notoriously hard to treat because pancreatic tumours are surrounded by a toxic stew of proteins and other tissues that protect the cancer from the immune system’s natural role to attack invaders. They also studied breast, ovarian, colorectal, and lung cancer cells, using advanced 3D imaging technology to watch the behaviour of immune cells as they swarmed to the cancerous region.

Source: University of Rochester Medical Center

New Research Explains Differences in Men’s and Women’s Immune Systems

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By analysing the immune system of female-to-male transgender individuals, Swedish researchers demonstrate the role of sex hormones in regulating the immune system. This newfound knowledge, published in Nature, explains differences between men and women, particularly in terms of immune signalling, and can be used to develop new immunological medications according to researchers.

Sex differences in the immune system are regulated both by genetics and by sex hormones. However, immunological comparisons between men and women can never fully distinguish the significance of genetic versus hormonal variations.

Now, three Swedish research groups led by Karolinska Institutet and Uppsala University has conducted a unique study analysing the regulation and adaptation of the immune system over time in 23 trans men who have undergone gender-affirming testosterone treatment, starting at the age of 18–37 years.

“We have followed individuals who were assigned female sex at birth and later received testosterone treatment in adulthood. Their genetic profile remains unchanged, while their hormone profile shifts entirely from typically female to male hormone levels,” says Petter Brodin, paediatrician and professor of paediatric immunology at the Department of Women’s and Children’s Health, Karolinska Institutet, who led the study together with Nils Landegren, assistant professor at Uppsala University, and Olle Kämpe, Professor at the Department of Medicine, Solna, Karolinska Institutet. “This unique change allows us, for the first time, to identify which parts of a person’s immune system are directly regulated by sex hormones rather than genetic sex differences.” 

The researchers can now demonstrate that increased testosterone levels and the accompanying reduction in oestrogen particularly affect the balance between two crucial immune signalling systems: antiviral interferon type 1 (IFN-1) and proinflammatory signals such as tumour necrosis factor alpha (TNFα).  

Specifically, they found that testosterone modulates a cross-regulated axis between type-I interferon and tumour necrosis factor. This is mediated by functional attenuation of type-I interferon responses in both plasmacytoid dendritic cells and monocytes. Conversely, testosterone potentiates monocyte responses leading to increased tumour necrosis factor, interleukin-6 and interleukin-15 production and downstream activation of nuclear factor kappa B-regulated genes and potentiation of interferon-γ responses, primarily in natural killer cells. 

The immune system changes throughout life

They also have a hypothesis about why the immune system needs to be dynamically regulated by hormones throughout life. 

“All individuals must be able to adjust their immune systems over the course of their lives to be optimally regulated for the conditions and challenges we face. During puberty and sexual maturation, new demands arise, and the immune system must be regulated differently to enable pregnancy in women and muscle growth in men,” says Petter Brodin. 

By regulating these key functions via sex hormones, this can be achieved, and in women, it is dynamically controlled even during a menstrual cycle,” he adds. 

The results of the study open an entirely new field of research, according to Nils Landegren. 

“The newfound knowledge will help us better influence people’s immune systems even without using sex hormones. For example, new drugs can be developed to impact these regulatory mechanisms and thus rebalance the immune response, especially for women with the autoimmune rheumatic disease SLE,” he explains. 

However, the results also have a more direct implications for transgender individuals. 

“This research is also of crucial for transgender individuals undergoing gender-affirming hormone therapy, and I believe that this group deserves significantly more scientific attention and follow-up to ensure their long-term health,” says Petter Brodin. 

Source: Karolinska Institutet

How the Brain Protects Itself Against Herpes Simplex Virus

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More than half of us are carriers of chronic herpesvirus infections. But even though the herpes simplex virus can infect nerve cells, it rarely causes serious infection of the brain. Researchers from Aarhus University have now discovered a key element of the explanation.

The researchers have discovered a previously unknown defence mechanism in the body that is the reason why herpes infection causes a serious and potentially fatal brain inflammation in only one out of 250 000 cases. The study has recently been published in the scientific journal Nature.

“The study has exciting perspectives because it gives us a better understanding of how the brain defends itself against viral infections,” says Professor Søren Riis Paludan from the Department of Biomedicine at Aarhus University. He is the article’s last author, a Lundbeck Foundation Professor and centre director of the Excellence Centre CiViA.

“We’ve discovered how our body prevents herpesvirus from entering into the brain, even though 50–80% of us are chronically infected with this particular virus. The idea behind CiViA is that we want to understand how the body fights infections without harming itself at the same time. The mechanism we’ve found doesn’t cause inflammatory reactions,” he says.

The answer lies in the protective TMEFF1 gene.

The brain uses a novel mechanism to keep the virus out

Many years of experimenting with the genome-wide CRISPR screening technology and development of mice that lacked the critical gene have finally convinced the researchers that TMEFF1 produces a protein that prevents herpesvirus from entering into nerve cells.   

The study in Nature is accompanied by another article describing two patients with brain inflammation caused by herpesvirus infection, called herpes encephalitic. In a collaborative study led by researchers in New York, the research group in Aarhus discovered that two children who developed herpes encephalitis were carrying a genetic defect that disabled the protective TMEFF1 gene.

“The new study is groundbreaking because it updates the basic understanding of immunity against viral infections,” explains Søren Riis Paludan.

 “This is interesting for immunologists because it illustrates that there are still many immunological mechanisms in the brain that we don’t know about. “The study is also relevant for neuroscience because it sheds light on how the brain, so to say, prevents unwanted visitors from intruding without causing harm to the brain itself, i.e. the neuronal cells,” he says.

May provide a better understanding of Alzheimer’s

Søren Riis Paludan hopes that the study is the first step towards revealing a completely new range of brain defence mechanisms. One of the tracks that the researchers will now investigate is what the discovery may mean for the development of dementia.

Research has already demonstrated a correlation between infection with herpesviruses and later development of Alzheimer’s disease.

“Perhaps our discovery of a new antiviral mechanism in the brain can help to clarify whether individual differences in this particular mechanism or similar mechanisms can give the virus access to the brain and accelerate neurodegenerative processes,” says Søren Riis Paludan.

Source: Aarhus University