5 A composition in oral
dosage form comprises
tryptophan or at least one
tryptophan intermediate, and at least one bacterium that (a) expresses enzymes of the shikimate pathway and is capable of producing
tryptophan and / or (b) expresses enzymes of the indole pathway and is capable of producing one or more immunomodulatory metabolites. The composition may include a cohort of
bacteria 10 including at least one bacterium that (a) expresses enzymes of the shikimate pathway and is capable of producing tryptophan and at least one bacterium that (b) expresses enzymes of the indole pathway and is capable of producing one or more immunomodulatory metabolites. Typically, the cohort of
bacteria is capable of producing the immunomodulatory indole derivatives indole-3-
lactic acid (ILA), 15 indole-3-propionic acid (IPA) and indole
acrylic acid (IA). The composition finds utility in inhibition or prevention of immune-mediated inflammatory damage in subjects with an immune-mediated infectious or non-infectious
disease, and in particular can prevent a severe
inflammatory response or incidence of Long Covid in SARS-CoV-19 subjects. 20 (Figure 16)