A group from Division of Immunology, Transplantation and Infectious Diseases, IRCCS San Raffaele Scientific Institute, San Raffaele Via Olgettina 58, 20132, Milan, Italy, etc. has reported that Chitinase-3-like protein-1 at hospital admission predicts COVID-19 outcome.
It was found hat high levels of CHI3L1 were associated with an increased risk of adverse outcome, including transfer to the ICU or mortality, independently of age, sex, comorbidities, degree of respiratory insufficiency and systemic inflammation at admission, all known to be associated with COVID-19 clinical outcome.
The ideal biomarkers should not just reflect the overall inflammatory burden but disclose the events responsible for adverse disease evolution, such as vascular inflammation and lung remodeling. Moreover, since the interplay of antigen-presenting cells and T cells is crucial determinant of COVID-19 outcome, molecules involved in this process could be suitable candidates. Chitinase-3 like-protein-1 (CHI3L1), a member of the glycoside hydrolase family, meets these requirements. CHI3L1 binds to chitin, although being devoid of the ability to cleave the protein. It also binds to other substrates such as hyaluronic acid and heparin. Various signals that are activated in the early phases of COVID-19, including extracellular matrix (ECM) alterations, cell and tissue injury and response to cytokines and growth factors, elicit its synthesis by tissue cells and inflammatory leukocytes. In turn, CHI3L1 stimulates the expression of ACE-2 and viral spike protein priming proteases in pulmonary epithelial and vascular cells.
Since CHI3L1 is a recognized biomarker of kidney injury, CHI3L1 levels may at least in part reflect kidney damage, but it must be studied further.