Research Roundup: T-Cell Immune Response to COVID-19 Vaccines and More

Vaccine

Every week there are numerous scientific studies published. Here’s a look at some of the more interesting ones.

T-Cell Immune Response to COVID-19 Vaccines and Natural Infections

Much of the discussions and news reports about immune responses to vaccines and COVID-19 revolve around antibody levels. Much less has been said about T-cells, which provide longer-term protection. Researchers at Gladstone Institutes conducted a detailed T-cell survey before and after COVID-19 immunization, which they published in eLife. They concluded that the Pfizer-BioNTech and Moderna mRNA vaccines create long-term populations of T-cells that recognize multiple SARS-COV-2 virus variants. They also found key differences in the T-cell responses in people who had COVID-19 infections before vaccination compared to people who had never been infected.

“Overall, our data support the idea that vaccines are eliciting a very robust T-cell response in healthy individuals,” said Nadia Roan, senior author of the study and Gladstone Associate Investigator. “But they also suggest there may be some ways to improve them further, by getting more of the vaccine-elicited T-cells to park themselves in the respiratory tract.”

Antibodies produced by B-cells quickly recognize viruses, target them, and prevent infection by destroying the viruses. T-cells, however, identify and destroy cells that are already infected. Antibodies are better at stopping initial infection, but T-cells typically last longer after an initial infection or vaccine. At that point they are better at fighting off disease in its early stages, which prevents severe symptoms. But T-cells are very diverse and difficult to analyze. Some subsets respond differently to infected cells and behave differently, while others have different functions within the overall T-cell immune response.

One key finding was that in people who had not been previously infected, the T-cell responses become stronger in quantity and quality after the second dose of the vaccine. But in people who had previously had COVID-19, there was not much of a change between the first and second vaccine dose.

Blood Biomarkers Provide Warning Signs of Dementia

Investigators at the German Center for Neurodegenerative Diseases (DZNE) identified molecules in the blood that potentially warn of impending dementia. The research study included several university hospitals across Germany. The biomarkers were based on measuring levels of microRNAs. They say that the technique isn’t ready yet for practical use, but they hope to develop a simple blood test. MicroRNAs have regulatory properties, influencing protein production and metabolism. In tests in humans, mice and cell cultures, they found three microRNAs whose levels were linked to mental performance. The three microRNAs also influence neuro-inflammation and neuroplasticity, including the ability of neurons to establish connections with each other.

Stem Cell Population Essential for Bone Regeneration

Researchers at the University of Tsukuba, Japan, identified a subpopulation of mesenchymal stem cells that play a major role in bone healing. The stem cells are found in the bone marrow and express the marker CD73. When a bone fracture heals, it moves through a series of stages, including clotted blood forming at the fracture. This clot is replaced by fibrous tissue and cartilage, then by a hard bony callus. The bone is then remodeled, with regular bone replacing the hard callus. They found that the generation of the callus is critically dependent on recruiting MSCs from the surrounding tissue and bone marrow. They observed the CD73-positive MSCs migrating toward the fracture site and forming new cartilage and bone cells. When they grafted CD73-positive MSCs into the fracture, they noted enhanced healing processes.

Antiviral Molecule Prevents SARS-CoV-2 from Entering Cells

Scientists at Washington University School of Medicine in St. Louis developed a compound that prevents the SARS-CoV-2 virus, which causes COVID-19, from entering cells. The compound is called MM3122 and has been studied in cell cultures and in mice. MM3122 targets a key human protein called transmembrane serine protease 2 (TMPRSS2), which coronaviruses use to enter and infect human cells. Once the virus attached onto a cell in the epithelia of the airway, the TMPRSS2 protein cuts the viral spike protein, which activates the spike protein to mediate fusion of the viral and cellular membranes—starting the infection process. In cell cultures, MM3122 protected cells from viral damage better than remdesivir, Gilead Sciences’ antiviral against COVID-19; and an acute safety assay in mice demonstrated that large doses of MM3122 given for seven days did not cause noticeable issues. The compound also was effective against SARS-CoV, the virus behind SARS, and MERS-CoV, the coronavirus that causes MERS. The researchers are now working with researchers at the NIH to test it in animal models of COVID-19. They are also working on an oral version of the injectable compound.

Specific Personality Traits Might Signal Pending Alzheimer’s

Researchers at Florida State University found that specific changes in the brain linked with Alzheimer’s disease are often visible earlier in people with personality traits associated with the disease. The research focused on two traits: neuroticism, or a predisposition for negative emotions, and conscientiousness, linked to a tendency to be careful, organized, goal-directed and responsible. They found that people with amyloid and tau deposits, proteins linked to Alzheimer’s disease in the brain, were identified in participants who scored higher in neuroticism levels and lower in conscientiousness. The study suggests that personality traits might help protect against Alzheimer’s and other brain diseases by delaying or preventing the neuropathology for people strong in conscientiousness and low in neuroticism.

Why We Overeat

A study from the University of Washington School of Medicine/UW Medicine reported on the function of glutamatergic neurons in mice. These neurons communicate to the lateral habenula, a brain region associated with the pathophysiology of depression, and the ventral tegmental area, which is involved in motivation, reward and addiction. They found that when mice are eating, the neurons in the lateral habenula are more responsive than the neurons in the ventral tegmental area. They suggest that these neurons might play a bigger role in guiding feeding. In addition, they studied the influence of the leptin and ghrelin hormones, which are believed to regulate behavior via the mesolimbic dopamine system, part of the reward pathway. The research adds additional insight into satiety and why people — or at least mice — overeat.

“We found these cells are not a monolithic group, and that different flavors of these cells do different things,” said Garret Stuber, a joint UW professor of anesthesiology and pain medicine and pharmacology, the paper’s senior author.

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