## 4 Discussion
The low colonization frequency of GMNL _Lactobacillus_ strains in our trial might be due to the insufficiency in oral consumption duration or dosage, low efficiency of the detection method, or a low Nugent score of the enrolled participants. Matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI TOF-MS) was used for determination of the presence of orally consumed _Lactobacillus_ in vagina. [PERSON] et al. reported that the detection rate of _L. rhamnus_ GR-1 was 11% but without detectable _L. reuteri_ RC-14, using MALDI TOF-MS in pregnant women at a high risk for preterm birth with normal vaginal flora (Nugent score \(\leq 3\)), after a 2-month consumption [30]. The lowdetection rate of GMNL _Lactobacillus_ strains in the vaginal swabss of our trial suggests the existence of other possibilities in addition to vaginal colonization of supplemented probiotics, such as immunomododulation or competitive inhibition of pathogens in the gastrointestinal tract. _G. vaginalis_ infection might cause gut microbiota dysbiosis and inflammation through the upregulation of NF-kB, TNF-\(\alpha\), or myeloperoxidase in vivo. In a mouse study, the oral gavage of _L. plantarum_ NK3 and B. longum NK49, which are anti-inflammatory probiotics, displayed inhibitory effects on NF-kB activation and TNF-\(\alpha\) production and decreased _G. vaginalis_ population in the vagina [31]. These findings suggest that the anti-inflammation activity of probiotics can be a mechanism for BV intervention. The induction of IL-10 and interferon (IFN)-\(\gamma\) through the four GMNL _Lactobacillus_ strains was observed in healthy peripheral blood mononuclear cells (PMBCs) (Figure S5). [PERSON] et al. previously observed that the treatment of IFN-\(\gamma\) rescued the _S. aureus_-induced severe injury of endothelial cells [32]. The IFN-\(\gamma\) production by neutrophils can facilitate bacterial clearance in a mouse model of bacterial pneumonia [33]. Although IFN-\(\gamma\) concentration in vaginal lavage fluid from BV women did not show significant changes in comparison with healthy women with vaginal pH less than 4.5, the IFN-\(\gamma\) level significantly decreased in the vaginal lavage fluid from healthy women with vaginal pH greater than 4.5 [34]. Thus, the induction of IFN-\(\gamma\) production from PMBCs through GMNL _Lactobacillus_ strains might assist in the control of vaginal bacterial infection. [PERSON] et al. noted a 100-fold decrease in IL-10 in pregnant women with adverse pregnancy outcome, in comparison with healthy controls [35]. The effects of VGA-1 or VGA-2 in pregnant women with BV should be studied in the future. IL-6 significantly increased in endocervical secretion of BV patients without human papilloma virus infection. [PERSON] et al. noted that the 174 G > C polymorphism of IL-6 gene increased the risk for BV [36]. These reports suggest that IL-6 might serve as a pathogenic factor in BV. [PERSON] et al. recently observed that _G. vaginalis_ induced IL-6 production in the VK2 endocervical cell line, and this phenomenon could be reduced by _Lactobacillus_ isolates of women with optimal vaginal microflora [37]. Here, we observed the decreased IL-6 expression in vaginal swabs after 4-week-consupmtion of VGA-1 or VGA-2, which might reflect the status of normal-like vaginal microflora among participants. The abundance of _Lactobacillus_ species benefits vaginal health by preventing the colonizations of pathogenic bacteria with activity for lactic acid or H\({}_{2}\)O\({}_{2}\) production [38; 39]. The loss of diversity of _Lactobacillus_ species is thought to be a biomarker for BV, and _Lactobacillus_ profiling is used as a diagnosis tool for BV. [PERSON] et al. reported that the main composition of vaginal _Lactobacillus_ strains included _L. crispatus_ (56%), _L. jensenii_ (26%), and _L. gasseri_ (18%) [40]. All _Lactobacillus_ isolates displayed antagonistic activity against _G. vaginalis_ or _E. coli_ and resistance to metronidazolezoe [40], one of the current antibiotics used in BV treatment.