COMPOSITIONS COMPRISING BACTERIAL STRAINS

1 .- 30 . (canceled)

31 . A method of enhancing an immune response to an antigen in a subject in need thereof comprising administering to the subject a composition comprising a bacterial strain of the species Bifidobacterium breve, wherein the bacterial strain comprises a 16s rRNA gene sequence having at least 95% sequence identity to the sequence of SEQ ID NO: 1.

32 . The method of claim 31 , wherein the antigen comprises a viral antigen, a bacterial antigen, a fungal antigen, a parasite antigen, or a tumor antigen.

33 . The method of claim 32 , wherein the viral antigen is an antigen of a virus selected from the group consisting of influenza virus, human immunodeficiency virus (HIV), hepatitis B virus, herpes simplex virus, rabies, respiratory syncytial virus, cytomegalovirus, a coronavirus, varicella zoster virus, Epstein Barr virus, and human papillomavirus.

34 . The method of claim 31 , wherein the subject has a disease caused by a pathogen from which the antigen is derived.

35 . The method of claim 31 , wherein the subject has a disease caused by a coronavirus.

36 . The method of claim 31 , wherein the bacterial strain expresses EPS on its surface.

37 . The method of claim 31 , wherein the bacterial strain expresses pullulanase.

38 . The method of claim 31 , wherein the bacterial strain has a biochemical profile that is positive for fermentation of one or more of α-galactosidase, β-galactosidase, α-glucosidase and β-glucosidase, α-arabinose, mannose, and raffinose as determined by an Analytical Profile Index test.

39 . The method of claim 31 , wherein the immune response comprises an immune response to a vaccine comprising the antigen.

40 . The method of claim 31 , wherein the bacterial strain stimulates TLR2 or NFκB and/or increases the expression level and/or activity of IL-12p70, IL-12p70, IFNγ, IL-4, TNF-α and/or IL-17α.

41 . The method of claim 31 , wherein the bacterial strain comprises a 16s rRNA gene sequence having at least 98% sequence identity to the sequence of SEQ ID NO: 1, as determined by a Smith-Waterman homology search algorithm using an affine gap search with a gap open penalty of 12 and a gap extension penalty of 2.

42 . The method of claim 31 , wherein the bacterial strain comprises a 16s rRNA gene sequence of SEQ ID NO: 1.

43 . The method of claim 31 , wherein the bacterial strain is the strain deposited under accession number 42380 at NCIMB.

44 . The method of claim 31 , wherein the sequence identity is determined by a Smith-Waterman homology search algorithm using an affine gap search with a gap open penalty of 12 and a gap extension penalty of 2.

45 . A method of treating an immunodeficiency in a subject in need thereof comprising administering to the subject a composition comprising a bacterial strain of the species Bifidobacterium breve, wherein the bacterial strain comprises a 16s rRNA gene sequence having at least 95% sequence identity to the sequence of SEQ ID NO: 1.

46 . The method of claim 45 , wherein the immunodeficiency comprises a primary immunodeficiency disease or a secondary immunodeficiency disease.

47 . The method of claim 46 , wherein the primary immunodeficiency disease comprises X linked agammaglobulinemia (XLA), chronic granulomatous disease (CGD), common variable immunodeficiency (CVID), or severe combined immunodeficiency (SCID).

48 . The method of claim 46 , wherein the secondary immunodeficiency disease comprises AIDS, a cancer of the immune system, or an immune-complex disease.

49 . A method of stimulating the immune system in a subject in need thereof comprising administering to the subject a composition comprising a bacterial strain of the species Bifidobacterium breve, wherein the bacterial strain comprises a 16s rRNA gene sequence having at least 95% sequence identity to the sequence of SEQ ID NO: 1, wherein the subject has a disease or a condition that is treatable by stimulating the immune system.

50 . The method of claim 49 , wherein the disease or the condition is caused by a coronavirus.