Efficacies of Potential Probiotic Candidates Isolated from Traditional Fermented Korean Foods in Stimulating Immunoglobulin A Secretion

Abstract

The aim of this study was to evaluate efficacies of selected lactic acid bacteria (LAB) in inducing immunoglobulin A (IgA) secretion. Twenty-five different LAB isolated from traditional fermented Korean foods were characterized for their probiotic properties and screened to identify those that could stimulate lamina propria cells (LPCs) from Peyer's patch to secret IgA in vitro. Among them, four strains (Lactiplantibacillus plantarum CJW55-10, Lactiplantibacillus pentosus CJW18-6, L. pentosus CJW56-11, and Pediococcus acidilactici CJN2696) were found to be strong IgA inducers. The number of IgA positive B cells and soluble IgA level were increased when LPCs were co-cultured with these LAB. Expression levels of toll-like receptor (TLR) such as TLR2 and TLR4 and secretion of interleuckin-6 were augmented in LPCs treated with these LAB. Further, we determined whether oral intake of these LAB enhanced IgA production in vivo. After one-week of daily oral administration, these LAB feed mice increased mucosal IgA and serum IgA. In conclusion, selected strains of LAB could induce systemic IgA secretion by activating lamina propria B cells in Peyer's patch and oral intake of selected strains of LAB can enhance systemic immunity by inducing mucosal IgA secretion.

Keywords: Peyer’s patch; immunoglobulin A; interleukin-6; lactic acid bacteria; toll-like receptor.

Fig. 1.. Selected strains of LAB isolated from traditional fermented Korean foods can increase the frequency of IgA positive B cells within LPCs.

LPCs (2.5×10⁵ cells/well) from Peyer’s patches of Balb/c mice were co-cultured with each strain of heat-killed bacterium (5×10⁶ CFU/mL). After 7 days, flow cytometry analyses were performed with LPCs to detect (A) IgA positive B cells (IgA⁺B220⁺ cells) and (B) total B cells (B220⁺ cells) within LPCs. Control, no treatment. Data are shown as mean±SEM from three independent experiments. Significant differences compared with the control group are indicated by * p<0.05. IgA, immunoglobulin A; LAB, lactic acid bacteria; LPCs, lamina propria cells.

Fig. 2.. Selected strains of LAB isolated from traditional fermented Korean foods can increase expression levels of TLR2 and TLR4 and promote the secretion of IL-6 within LPCs.

LPCs (2.5×10⁵ cells/well) from Peyer’s patches of Balb/c mice were co-cultured with each strain of heat-killed bacteria (5×10⁶ CFU/mL). (A, B) After 7 days, quantitative real-time PCR analyses were performed with total RNAs isolated from LPCs to detect (A) Tlr2 and (B) Tlr4 expressions within LPCs. (C–E) After 7 days, ELISAs were performed with culture supernatant of co-culture to detect (C) IL-6, (D) TGF-β, and (E) pIgR. Control, no treatment. Data are shown as mean±SEM from three independent experiments. Significant differences compared with the control group are indicated by ^* p<0.05 or ^** p<0.01. TLR, toll-like receptor; IL-6, interleuckin-6; TGF-β, transforming growth factor-β; pIgR, poly Ig receptor; LAB, lactic acid bacteria; LPCs, lamina propria cells; PCR, polymerase chain reaction; ELISAs, enzyme‐linked immunosorbent assays.

Fig. 3.. Pediococcus acidilactici CJN2696 promotes IgA secretion of LPCs via TLR2 signaling pathway.

LPCs (2.5×10⁵ cells/well) from Peyer’s patches of wild-type TLR4 (C3H/HeN) mice or TLR4 null mice (C3H/HeJ) were co-cultured with P. acidilactici CJN2696 (5×10⁶ CFU/mL) in the absence or presence of anti-TLR2 neutralizing antibody (α-TLR2 Ab). After 7 days, (A) ELISAs were performed with culture supernatant of co-culture to detect IgA. (B) Flow cytometry analyses were performed for LPCs to detect IgA positive B cells (IgA⁺B220⁺ cells) within LPCs. PBS, LPC culture only; CJN2696, co-culture without antibody; CJN2696+α-TLR2 Ab, co-culture with antibody. Control, no treatment. Data are shown as mean±SEM from three independent experiments. Significant differences between two different groups are indicated by ^** p<0.01. IgA, immunoglobulin A; TLR, toll-like receptor; LPCs, lamina propria cells; ELISAs, enzyme‐linked immunosorbent assays.

Fig. 4.. Oral administration of selected LAB increases systemic IgA secretion.

Balb/c mice were randomly separated into ten groups (n=6 mice per group): Two control (PBS) groups and eight test (LAB) groups. For the two control groups, each mouse was orally administered 400 μL of PBS every day for 7 days or 21 days. For the eight test groups, each mouse was orally administered 400 μL of PBS containing LAB (CJW55-10, CJW18-6, CJW56-11, or CJN2696) every day for 7 days or 21 days. At 7 or 21 days after oral administration, mice were sacrificed for analysis. (A) Levels of GALT IgA, (B) levels of BALT IgA, (C) levels of serum IgA, (D) levels of serum IgG. Data are shown as means±SEM (n=6). Significant differences compared with the control group are indicated by * p<0.05. GALT, gut-associated lymphoid tissue; IgA, immunoglobulin A; BALT, bronchus-associated lymphoid tissue; LAB, lactic acid bacteria.