Efficacy of Lactococcus lactis Strain Plasma in Patients with Mild COVID-19: A Multicenter, Double-Blinded, Randomized-Controlled Trial (PLATEAU Study)

Abstract

Introduction: Coronavirus disease 2019 (COVID-19), caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), is still an ongoing public health threat. COVID-19 can be accompanied by prolonged symptoms, known as “long COVID”, however, no pharmaceutical treatments are currently available for these symptoms. Lactococcus lactis strain Plasma (LC-Plasma; Lactococcus lactis subsp. lactis JCM 5805) directly activates human plasmacytoid dendritic cells (pDCs) and triggers antiviral immune responses. We hypothesized that LC-Plasma reduced SARS-CoV-2 viral load and eased symptoms in patients with mild COVID-19. Methods: This PLATEAU study enrolled 100 patients with mild COVID-19 during Omicron BA.1 endemic, who were randomized into the LC-Plasma or placebo group in a 1:1 ratio and were observed for 14 days. The primary endpoint was change in total score of eight subjective symptoms (fatigue, anorexia, headache, cough, shortness of breath, chest pain, smell, and taste disturbance). Secondary endpoints included each symptom, SARS-CoV-2 viral load, and pDCs. Results: The primary endpoint did not show between-group differences. However, the proportion of patients without smell and taste disturbances was significantly higher in the LC-Plasma group on day 13 (p = 0.030). The LC-Plasma group showed a significantly earlier decrease in SARS-CoV-2 viral load on day 4 (p < 0.001) and an increase in pDCs on day 8 (p = 0.0498). Mild adverse events, such as diarrhea, cough-variant asthma, and urticaria, occurred in three (5.9%) patients in the LC-Plasma group. Conclusions: The intake of LC-Plasma in patients with mild COVID-19 activates pDC, decreases SARS-CoV-2 viral load earlier, and may improve smell and taste disorders more quickly. LC-Plasma could be a safe, inexpensive, and easily accessible tool for the treatment of mild COVID-19. Trial Registration: jRCTs071210097.