Zhang L.1,2,3, Xu Z.1,2.3, Mak J.W.Y.1,2,3, Chan F.K.L.1,2,3 Ng S.C.1,2,3

Background : Gut dysbiosis is associated with immune dysfunction and severity of COVID-19. Whether targeting dysbiosis will improve outcomes of COVID-19 is unknown.

Aim : To assess the effects of a novel microbiome formula (SIM01) as an adjuvant therapy on immunological responses and changes in gut microbiota of hospitalised COVID-19 patients.

Methods : This was an open-label, proof-of-concept study. Consecutive COVID-19 patients admitted to an infectious disease referral centre in Hong Kong were given a novel formula of Bifidobacteria strains, galactooligosaccharides, xylooligosaccharide, and resistant dextrin (SIM01). The latter was derived from metagenomic databases of COVID-19 patients and healthy population. COVID-19 patients who were admitted under another independent infectious disease team during the similar period without receiving the SIM01 formula acted as controls. All patients received standard treatments for COVID-19 according to the hospital protocol. We assessed antibody response, proinflammatory markers and faecal microbiota profile from admission up to Week 5.

Results : Twenty-five consecutive patients received SIM01 for 28 days; 30 patients without receiving the formula acted as controls. Significantly more patients receiving SIM01 than the control group developed antibody (88% vs. 63.3%; p =0.037) by Day 16. One (4%) patient in the SIM01 group and 8 (26.7%) in the control group did not develop positive IgG antibody upon discharge. At Week 5, plasma levels of interleukin (IL)-6, monocyte chemoattractant protein-1 (MCP-1), macrophage colony-stimulating factor (M-CSF), tumour necrosis factor (TNF-α), and IL-1RA dropped significantly in the SIM01 group but not in the control group. Metagenomic analysis showed that the bacterial species of the SIM01 formula were found in greater abundance, leading to enrichment of commensal bacteria and suppression of opportunistic pathogens in COVID-19 patients by Week 4 and Week 5.

Conclusion : The use of a novel microbiome formula SIM01 hastened antibody formation against SARS-CoV-2, reduced pro-inflammatory immune markers and restored gut dysbiosis in hospitalised COVID-19 patients.

Keywords : Gut microbiota, SARS-CoV-2, immunity, probiotics