The Consumption of Lacticaseibacillus rhamnosus HDB1258 Changes Human Gut Microbiota and Induces Immune Enhancement Through NK Cell Activation.

The gut microbiota can play an important role in enhancing the host's complex immune system. In this regard, many studies indicate that probiotics consumption has a beneficial impact on alterations in the composition of the gut microbiota. Our previous study demonstrated that the oral administration of Lacticaseibacillus rhamnosus HDB1258 (HDB1258) enhances immune cell activity and alters the composition of gut microbiota in C57BL/6 mice, thereby showing its potential as a novel immunostimulatory ingredient. Therefore, this clinical trial assessed the effects of HDB1258 on human natural killer (NK) cell activity and changes in gut microbiota. It also investigated the correlation between gut microbiota and NK cell activity following HDB1258 supplementation. Participants (n = 71) were randomized into placebo and HDB1258 groups, and NK cell activity and gut microbiota were investigated at baseline (week 0) and endline (week 8). The present study showed that HDB1258 significantly increased NK cell activity and resulted in positive regulatory effects on the gut microbial balance in subjects compared to the placebo group. HDB1258 affected the gut microbial balance by inducing the growth of beneficial bacteria such as Lactococcus and Sutterella. Especially, the changes in Escherichia-Shigella composition were negatively correlated with the changes in NK cell activity after HDB1258 consumption. There was also a positive correlation between the NK cell activity in the HDB1258 group and the composition of Prevotella 9 and Adlercreutzia. These findings suggest that HDB1258 may improve the host's intestinal environment by regulating gut bacteria related to immune response and promote NK cell activation. This study was registered at clinical research information service (CRIS: KCT0008204).