An immune system timeline for tuberculosis progression

An international team of researchers has defined the series of immune system changes that occur when tuberculosis (TB) transitions from a non-infectious state to active disease. The results, published online in PLOS pathogens, highlight changes in inflammatory processes that can be detected in the blood long before clinical symptoms arise. These findings have important implications for developing diagnostics, vaccines and treatments to battle the TB epidemic.

An estimated 1.7 billion people—one quarter of the world’s population—are infected with the bacterium that causes TB, but only ~10% develop active pulmonary disease. In the article, scientists from the South African TB Vaccine Initiative, the University of Cape Town, the Center for Infectious Disease Research and SomaLogic looked for changes in various molecules in blood that together could predict the risk of TB progression. The time between the initial blood collection and TB diagnosis ranged from 1 to 894 days, so the investigators could construct a timeline of changes that occurred as the disease evolved.

The blood analyses revealed that TB progression associated with sequential modifications of immunological processes. Some of these processes, such as type I/II interferon signaling and complement cascade, were elevated as early as 18 months before TB diagnosis.

Understanding the biology of progression from infection to active pulmonary TB opens the door to blood-based tests that may determine those who are at risk of developing active disease and who need early treatment. These findings could also help development of better vaccines and host-directed therapies that accelerate eradication of TB infection.

Ref: Scriba, TJ et al. (2017) “Sequential inflammatory processes define human progression from M. tuberculosis infection to tuberculosis disease”PLOS Pathogens 13(11): e1006687.

Protein profiling reveals immune system dysfunction in Down syndrome

An article published online in Scientific Reports shows that Down syndrome may be a form of chronic immune disorder. In the largest and most comprehensive study of its kind to date, investigators at the Crnic Institute for Down Syndrome, the Sie Center for Down Syndrome, the University of Colorado, and Somalogic measured the levels of over 3500 proteins in the blood of Down syndrome patients and compared them to non-Down syndrome controls. Their results provide a new framework for understanding the physiological mechanisms that drive the altered disease susceptibilities seen in individuals with Down syndrome, and suggest that individuals with Down syndrome could benefit from therapies that decrease or modulate immune responses.

Down syndrome, or Trisomy 21, is caused by having three copies of chromosome 21 instead of two. Although the genetics of Down syndrome have been known for 60 years, it is still unclear how having the extra chromosome leads to various Down syndrome traits, including changes in common disease susceptibilities (e.g., Down syndrome individuals are more likely to develop Alzheimer’s, leukemia and autoimmune disorders, but less likely to develop solid tumors and cardiovascular disease). Understanding the biology that underlies these differences could inform a wide range of medical conditions that affect not only Down syndrome individuals, but the entire population.

The researchers used the SOMAscan assay to compare levels of blood proteins in 165 individuals with Down syndrome and 98 controls, and they identified 299 proteins that differed significantly between the two groups. Surprisingly, most of these proteins are not encoded by genes located on chromosome 21, but are associated with immune system control. Down syndrome individuals appear to have something that resembles an autoinflammatory condition, with elevated levels of proteins that promote inflammation but deficiencies in proteins that help eliminate foreign pathogens. The findings provide a new way to think about Down syndrome and possible targets of therapies to improve the health and lifespan of those with Down syndrome as well as the general population.

Sullivan, KD et al. (2017) “Trisomy 21 causes changes in the circulating proteome indicative of chronic autoinflammation” Scientific Reports 7(1): 14818.

 

Modified DNA aptamer inhibits IL-1α signaling

Modified DNA aptamer inhibits IL-1α signaling

In an article published online in Nature Communications, scientists from SomaLogic and Yale University report that they have successfully generated a novel Slow Off-rate Modified Aptamer (SOMAmer) molecule that binds tightly to interleukin 1 alpha (IL-1α), an essential inflammatory protein implicated in cancer and other diseases. The SOMAmer (called SL1067) shows high specificity for IL-1α and can block its activity. SL1067 could therefore be a useful tool for elucidating IL-1α’s role in producing inflammation and regulating the immune system.

IL-1α/SL1067 structure with IL-1α in green. SL1067 is in cyan with naphthyl-modified residues in orange.

The researchers determined the three-dimensional structure of SL1067 bound to IL-1α, providing the first high-resolution structure of this essential protein. This is also the first crystal structure of a SOMAmer that contains bases modified with naphthyl groups, five of which are involved in IL-1α binding. The naphthyl modifications allow SL1067 to adopt a very compact structure with unusual three-dimensional shapes that have never been seen before. Since SL1067 is small (only 22 nucleotides in length), stable and easily synthesized, it serves as an excellent starting point for development of novel therapeutic molecules that target IL-1α.

 

Ren, X et al. (2017) “Structural basis for IL-1α recognition by a modified DNA aptamer that specifically inhibits IL-1α signaling” Nat Commun, epub ahead of print.
https://www.nature.com/articles/s41467-017-00864-2