Antimicrobial peptide levels may gauge COVID-19 progression risk

The levels of serum levels of LL-37, an antimicrobial peptide whose expression is stimulated by vitamin D, may help assess the risk of disease progression in COVID-19 patients, reports a recent study.

The study included 78 COVID-19 patients (mean age 62 years, 54 percent men) from whom blood samples were collected between days 1 and 3 of clinical admission. A sandwich enzyme-linked immunosorbent assay was used to quantify serum LL-37 levels, which were expressed as the ratio between LL-37 and leukocyte count.

Participants were then divided into five groups according to disease severity: asymptomatic (n=10), with mild symptoms (n=13), not invasively ventilated (n=26), mechanically ventilated (n=13), and deceased (n=16).

Overall, the average LL-37 serum concentration was 68 ng/mL and ranged from 1–148 ng/mL. Mean serum LL-37 levels were highest in the asymptomatic group at 87 ng/mL, with values dropping to 57 ng/mL in those who needed mechanical ventilation. However, researchers pointed out that such a correlation did not reach statistical significance.

Meanwhile, a similar pattern was observed when LL-37 levels were taken as a function of leukocyte count. The LL-37/leukocyte count ratio was statistically and inversely correlated with COVID-19 severity (p<0.001), with ratio values peaking in asymptomatic patients (mean, 81) and being lowest in the deceased and mechanically ventilated patients (mean, 8).

“Our results indicate that the progression of COVID-19 could be assessed using the LL-37/leukocyte count ratio as an early marker at the beginning of an inpatient stay,” the researchers said.