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(HealthDay News) — Individuals with post-acute infection syndrome after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (long COVID [LC]) have differences in immune and hormone function compared with those without LC, according to a study published online Sept. 25 in Nature.

Jon Klein, from the Yale School of Medicine in New Haven, CT, and colleagues enrolled 273 individuals with or without LC in a cross-sectional study to examine the biological processes associated with the development and persistence of symptoms of LC. The study included multidimensional immune phenotyping and unbiased machine learning methods.

The researchers identified marked differences in circulating myeloid and lymphocyte populations relative to matched controls and evidence of exaggerated humoral responses directed against SARS-CoV-2 among those with LC. Individuals with LC had higher antibody responses directed against non-SARS-CoV-2 viral pathogens, especially Epstein-Barr virus. Variation was seen in the levels of soluble immune mediators and hormones among the groups, with lower cortisol levels noted among those with LC.

“We are excited to see such clear differences in the immune phenotypes in people with and without long COVID,” coauthor Akiko Iwasaki, PhD, also from the Yale School of Medicine, said in a statement. “These markers need to be validated in larger studies, but provide a first step in dissecting the disease pathogenesis of long COVID.”

Several authors disclosed ties to the pharmaceutical and information technology industries.

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