The following is a summary of “SARS-CoV-2 infection of thymus induces loss of function that correlates with disease severity,” published in the APRIL 2023 issue of Allergy & Immunology by Rosichini, et al.

Patients with COVID-19 often exhibit lymphopenia, particularly in the T-cell compartment, which has been associated with disease severity. However, the underlying causes of T-cell decline and dysfunction in COVID-19 are not fully understood. For a study, researchers sought to investigate the impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on thymic function, as viral infections can directly affect the thymus and impair T-cell generation.

They quantified T-cell receptor excision circles and κ-deleting recombination excision circles, which are markers of T-cell and B-cell neogenesis, respectively, in SARS-CoV-2-infected patients. They also developed an in vitro culture system using primary human thymic epithelial cells (TECs) to study the effects of SARS-CoV-2 on TEC function.

The study revealed that patients with COVID-19 had reduced thymic function, and the severity of the disease was inversely associated with thymic function. They found that angiotensin-converting enzyme 2 (ACE2), the receptor through which SARS-CoV-2 enters host cells, was expressed in the thymic epithelium, particularly in medullary TECs. They also demonstrated that SARS-CoV-2 can target TECs and downregulate genes and pathways associated with epithelial cell adhesion and survival.

The findings indicated that SARS-CoV-2 directly affects the human thymus and alters thymic function following infection. The findings contributed to the understanding of the impact of SARS-CoV-2 on T-cell homeostasis. Monitoring thymic activity may serve as a useful marker for predicting disease severity and progression in COVID-19.

Source: jacionline.org/article/S0091-6749(23)00147-1/fulltext