Ageing, or senescent cells, which stop dividing but don’t die, can accumulate in the body over the years and fuel chronic inflammation that contributes to conditions such as cancer and degenerative disorders.

In mice, eliminating senescent cells from aging tissues can restore tissue balance and increase healthy lifespan. Now a team led by investigators at Massachusetts General Hospital (MGH), a founding member of Mass General Brigham (MGB), has found that the immune response to a virus that is ubiquitously present in human tissues can detect and eliminate senescent cells in the skin.

For the study, which is published in Cell, the scientists analyzed young and old human skin samples to learn more about the clearance of senescent cells in human tissue.

The researchers found more senescent cells in the old skin compared with young skin samples. However, in the samples from old individuals, the number of senescent cells did not increase as individuals got progressively older, suggesting that some type of mechanism kicks in to keep them in check.

Experiments suggested that once a person becomes elderly, certain immune cells called killer CD4+ T cells are responsible for keeping senescent cells from increasing. Indeed, higher numbers of killer CD4+ T cells in tissue samples were associated with reduced numbers of senescent cells in old skin.

When they assessed how killer CD4+ T cells keep senescent cells in check, the researchers found that aging skin cells express a protein, or antigen, produced by human cytomegalovirus, a pervasive herpesvirus that establishes lifelong latent infection in most humans without any symptoms. By expressing this protein, senescent cells become targets for attack by killer CD4+ T cells.

“Our study has revealed that immune responses to human cytomegalovirus contribute to maintaining the balance of aging organs,” says senior author Shawn Demehri, MD, PhD, director of the High Risk Skin Cancer Clinic at MGH and an associate professor of Dermatology at Harvard Medical School. “Most of us are infected with human cytomegalovirus, and our immune system has evolved to eliminate cells, including senescent cells, that upregulate the expression of cytomegalovirus antigens.”

These findings, which highlight a beneficial function of viruses living in our body, could have a variety of clinical applications. “Our research enables a new therapeutic approach to eliminate aging cells by boosting the anti-viral immune response,” says Demehri. “We are interested in utilizing the immune response to cytomegalovirus as a therapy to eliminate senescent cells in diseases like cancer, fibrosis and degenerative diseases.”

Demehri notes that the work may also lead to advances in cosmetic dermatology, for example in the development of new treatments to make skin look younger.

A new study from researchers at Uppsala University and Karolinska Institutet shows that children who go on to develop symptoms of autism have different activity in their brain’s visual cortex from as early as five months when looking at certain types of movement. This finding may indicate that autistic people perceive their surroundings differently, even from a very young age, which could affect their development and learning.

Autism is defined by challenges with social communication and restricted and repetitive features in behaviour and interests. However, research shows that autistic people also have different perceptions of and reactions to various stimuli. In particular, many studies have shown a connection between autism and difficulties in perceiving whole units in visual movement patterns – such as when a flock of birds forms a common movement in the sky. Integrating movement signals into an overall figure is important in correctly perceiving how objects and surfaces move in relation to the viewer.

The new study examined activity in the brains of five-month-old infants sitting on their parent’s laps while viewing different types of visual information. The researchers measured how the brain reacted to simple visual changes in light (such as a line changing direction) and more complex patterns where the ability to see whole units were tested. The assessment used EEG technology, which records weak electrical signals created naturally in the brain’s cerebral cortex when processing information. The signals were measured using electrodes placed around the head on a specially adapted cap.

The infants who later on – at age three – exhibited many of the classic symptoms of autism had different brain activity when complex movement patterns were shown on the screen. This suggests that the brains of autistic people process visual motion differently from early infancy. On the other hand, simpler visual changes produced a clear and similar response in all of the children’s brains.

“Seeing this difference several years before the symptoms of autism develop is something completely new and contributes to our understanding of what early development looks like in autism. Autism has a strong hereditary component, and the differences we see in visual perception in infancy are likely connected to genetic differences,” explains Terje Falck-Ytter, Professor at the Department of Psychology at Uppsala University and principal of the study.

“We can only guess at the infant’s subjective experience of visual motion. However, given the results and previous studies of the relationship between brain activity and experience in adults with the diagnosis, it is plausible to believe that they experience it differently. It is also possible that this finding relates to the perception of complex social movements, such as the interpretation of facial expressions. This is something we want to investigate in future studies.”

The study is part of the larger research project EASE (Early Autism Sweden), a collaboration between Uppsala University and the Center of Neurodevelopmental Disorders at Karolinska Institutet (KIND). When the children were three years old, a standardised play observation was carried out with a psychologist based on this. Each child received a score corresponding to symptoms of autism. The study also included a control group of over 400 infants, meaning the researchers had good knowledge of how children’s brains usually react to these stimuli.

“Autism cannot currently be diagnosed with good accuracy until around 2–3 years of age, but we hope that more knowledge about early development will enable us to make these assessments earlier. This would make it easier for families to get support and hopefully individualised training sooner. It could also stimulate completely new research into early interventions. The results of this study showed statistically significant differences between groups. Still, it is important to emphasise that the EEG measurement’s accuracy was too low to predict the development of individual children. It is, therefore, too early to tell whether this method will have clinical value for early detection, for example,” concludes Falck-Ytter.