Probiotic supplementation has been part of the discussion on methods to enhance humoral immunity. Administration of Bifidobacterium bifidum OLB6378 (OLB6378) reduced the incidence of late-onset sepsis in infants. In this non-randomized study, we aimed to determine the effect of administration of live OLB6378 on infants' humoral immunity. Secondly, we tried to elucidate whether similar effects would be observed with administration of non-live OLB6378. Low birth weight (LBW) infants weighing 1500-2500 g were divided into three groups: Group N (no intervention), Group L (administered live OLB6378 concentrate), and Group H (administered non-live OLB6378 concentrate). The interventions were started within 48 h after birth and continued until six months of age. Serum immunoglobulin G (IgG) levels (IgG at one month/IgG at birth) were significantly higher in Group L than in Group N (p < 0.01). Group H exhibited significantly higher serum IgG levels (p < 0.01) at one month of age and significantly higher intestinal secretory immunoglobulin A (SIgA) levels (p < 0.05) at one and two months of age than Group N. No difference was observed in the mortality or morbidity between groups. Thus, OLB6378 administration in LBW infants enhanced humoral immunity, and non-live OLB6378, which is more useful as a food ingredient, showed a more marked effect than the viable bacteria.
Keywords: heat-treated; humoral immunity; non-live bacteria; probiotics; sepsis; serum IgG; stool secretory IgA.