Probiotic Effect on SARS‐CoV2 Immunity Is Associated to Type‐1 Interferons: A Post‐Hoc Analysis of a Randomized, Placebo‐Controlled Trial

Gut microbiota has been reported to protect from lung viral infection in animal models by stimulating type-I interferon signaling. Type-I interferons can have direct antiviral activity while also stimulating antibody-producing B cells. Antibodies against Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV2) have been correlated to faster infection clearance and protection against reinfection. A specific 4-strain probiotic combination (Pediococcus acidilactici CECT7483 plus Lactoplantibacillus plantarum CECT7484, CECT7485 and CECT30292) was recently studied in a randomized, quadruple-blinded, placebo-controlled trial in 300 SARS-CoV2-infected, symptomatic ambulatory patients (NCT04517422). Study subjects did not receive corticosteroids or antivirals. Compared to placebo, probiotic intervention (2x109 cfu/day for 30 days) achieved faster symptom clearance and increased SARS-CoV2-specific immunoglobulins M and G (IgM and IgG). We hypothesize these effects could be related to increased type-I interferon signaling.A random subset of 70 subjects (35 probiotic and 35 placebo) was selected out of the 300 participants in the clinical study. Stored serum samples collected on day 0 (baseline), 15 and 30 (end of intervention) were analyzed for interferon-alpha 2a (IFNa) and interferon-beta 1a (IFNb) using enzyme-linked immunosorbent assay. Demographic data, baseline viral load, symptom duration and SARS-CoV2-specific IgM and IgG serum titers were retrieved from patient case report forms. Differences between probiotic and placebo were compared using Mann-Whitney or Chi-squared tests, as appropriate. Correlations between type-I interferons and other variables were assessed by Spearman correlation. All procedures on study subjects had been approved by the Internal Review Board of Hospital General Dr. Manuel Gea (Mexico City) and adhered to Helsinki Declaration.In the selected subset of patients, study groups were comparable at baseline (all p>0.10, Table 1). Probiotic treatment was associated to a larger increase of IFNa on day 30 (p=0.007) and of IFNb on days 15 and 30 (both p<0.001), compared to placebo (Figure 1). Similarly, SARS-CoV2-specific IgM and IgG were higher on days 15 and 30 (all p<0.001) and duration of fever, cough, headache and myalgia were shorter (all p<0.05) in probiotic compared to placebo. Increase in IFNb across the study correlated to increase in SARS-CoV2-specific IgM (rho=0.55, p<0.001) and IgG (rho=0.61, p<0.001), and inversely correlated to duration of cough (rho=-0.26, p=0.033) and fever (rho=-0.24, p=0.042). Conversely, increase in IFNa correlated to increase in SARS-CoV2-specific IgM (rho=0.33, p=0.005) only. Neither increase in IFNa nor IFNb correlated to age, number of metabolic comorbidities or days from onset of symptoms.Compared to placebo, oral administration of a specific 4-strain probiotic combination resulted in significant increase in type-I interferons in serum, especially IFNb, correlating to higher SARS-CoV2-specific IgM and IgG antibodies and faster clearance of some symptoms.