The human’s natural immune system (called complement) has been found to be associated with the severity of COVID disease in people with age-related macular degeneration (AMD), according to a new study published in Nature Medicine. A hyperactive complement system is known to be directly related to development of AMD.
In a retrospective observational study of patients with SARS-CoV-2 infection, researchers at Columbia University Irving Medical Center found that people with AMD are at greater risk of developing more serious complications and dying from COVID than people who have normally-functioning complement systems. In the study, out of 88 people identified with AMD, over 25% died from the virus, compared to the average mortality rate of 8.5 per cent. Additionally, about 20% required intubation.
One explanation is provided by researchers Sagi Shapira, PhD, MPH, and Nicholas Tatonetti, PhD (professors at Columbia University Vagelos College of Physicians and Surgeons). Corona viruses have been found to be proficient at mimicking proteins, particularly those involved in coagulation and those that make up the complement system. Such proteins are normally beneficial, as they help eliminate pathogens like bacteria and viruses. Hyperactivity of the proteins, however, can also increase coagulation and inflammation in the body, causing more harm than good. The new coronavirus, COVID-19, may be doing just that.
It is important to remember that these are early results from a small retrospective study, which shows only an association between AMD and severity of COVID disease. Further analysis with larger clinical cohorts is warranted before a causal relationship can be established. Meanwhile, people with AMD might be well-advised to take extra precautions against exposure to the COVID-19 virus.
SOURCE: Ramlall, V., Thangaraj, P.M., Meydan, C. et al. Immune complement and coagulation dysfunction in adverse outcomes of SARS-CoV-2 infection. Nat Med (2020). https://doi.org/10.1038/s41591-020-1021-2