Antimicrobial peptides and other potential biomarkers of critical illness in Sars-CoV-2 patients with acute kidney injury

Antimicrobial peptides (AMPs) are a complex network of 10-100 amino acid sequence molecules, widely distributed in Nature. Even though more than 300 AMPs have been described in mammals, cathelicidins and defensins remain the most investigated to date. Some publications examined the role of AMPs in COVID-19, but the findings are preliminary and in vivo studies are still lacking. Here, we report the plasma levels of five AMPs (LL-37, α-defensin 1, α-defensin 3, β-defensin 1 and β-defensin 3) and five cytokines (tumor necrosis factor-α, interleukin-1β, interleukin-6, interleukin-10, interferon-γ and monocyte chemoattractant protein-1), in 15 healthy volunteers, 36 COVID-19 patients without Acute Kidney Injury (AKI) and 17 COVID-19 patients with AKI, since AKI is a well-known marker of worse prognosis in Sars-CoV-2 infections. We found increased levels of α-defensin 1, α-defensin 3 and β-defensin 3, but not LL-37 or β-defensin 3, in our COVID-19 population, when compared with the healthy controls, in conjunction with higher levels of interleukin-6, interleukin-10, interferon-γ and monocyte chemoattractant protein-1, putting in evidence that these AMPs and cytokines may have an important role in the systemic inflammatory response and tissue damage that characterizes severe COVID-19. Graphic Abstract