People with Down syndrome have less-frequent viral infections, however when current, these infections result in extra extreme illness. New findings publishing on October 14 within the journal Immunity present that that is brought on by elevated expression of an antiviral cytokine kind I interferon (IFN-I), which is partially coded for by chromosome 21. Elevated IFN-I ranges result in hyperactivity of the immune response initially, however the physique overcorrects for this to cut back irritation, resulting in elevated vulnerability later within the viral assault.
Often an excessive amount of irritation means autoimmune illness, and immune suppression normally means susceptibility to infections. What’s uncommon is that people with Down syndrome are each infected and immunosuppressed, a paradox of kinds. Right here, we found how that is attainable.”
Dusan Bogunovic, Senior Examine Writer, Icahn College of Medication at Mount Sinai
Down syndrome is often brought on by triplication of chromosome 21. This syndrome impacts a number of organ methods, inflicting a combined medical presentation that features mental incapacity, developmental delays, congenital coronary heart and gastrointestinal abnormalities, and Alzheimer’s illness in older people.
Lately, it has change into clear that atypical antiviral responses are one other essential characteristic of Down syndrome. Elevated charges of hospitalization of individuals with Down syndrome have been documented for influenza A virus, respiratory syncytial virus, and extreme acute respiratory syndrome on account of coronavirus (SARS-CoV-2) infections.
Whereas individuals with Down syndrome present clear indicators of immune disturbance, it has but to be elucidated how a supernumerary chromosome 21 results in dysregulation of viral defenses. To handle this data hole, the researchers in contrast fibroblasts and white blood cells derived from people with and with out Down syndrome, at each the mRNA and protein ranges. They targeted on the potent antiviral cytokine IFN-I receptor subunits IFNAR1 and IFNAR2, that are positioned on chromosome 21.
The researchers discovered that elevated IFNAR2 expression was enough for the hypersensitivity to IFN-I noticed in Down syndrome, unbiased of trisomy 21. However subsequently, the hyper-active IFN-I signaling cascade triggered extreme detrimental suggestions by way of a protein known as USP18, which is a potent IFNAR detrimental regulator. This course of, in flip, suppressed additional responses to IFN-I and antiviral responses. Taken collectively, the findings unveil oscillations of hyper- and hypo-responses to IFN-I in Down syndrome, predisposing to each decrease incidence of viral illness and elevated infection-related morbidity and mortality.
“We have now much more to do to utterly perceive the complexities of the immune system in Down syndrome,” says first writer Louise Malle of the Icahn College of Medication at Mount Sinai. “We have now right here, partly, defined the susceptibility to extreme viral illness, however that is solely the tip of the iceberg.”
Malle, L., et al. (2022) Extreme Adverse Regulation of Kind I Interferon Disrupts Viral Management in People with Down Syndrome. Immunity. doi.org/10.1016/j.immuni.2022.09.007.