Evaluation and Mechanistic Investigation of Human Milk Oligosaccharide against SARS-CoV-2

3-Fucosyllactose Prevents Nonalcoholic Fatty Liver Disease by Modulating the Gut Microbiota-Derived Pantothenate in Mice

Nonalcoholic fatty liver disease (NAFLD) is a growing global health threat. Human milk oligosaccharides (HMOs) exhibit prebiotic properties that may alleviate NAFLD progression. Herein, our study demonstrates that 3-fucosyllactose (3-FL), a distinctive and crucial HMO, significantly attenuates body weight gain, enhances hepatic lipid metabolism, and reduces inflammation in a high-fat diet (HFD)-induced NAFLD mouse model. These findings suggest its potential as a dietary supplement for preventing and alleviating NAFLD progression. Subsequently, fecal metagenomic and nontargeted metabolomics analyses revealed that 3-FL treatment significantly alleviated HFD-induced gut microbiota dysbiosis, with a specific enhancement of the pantothenate (vitamin B5) metabolic pathways. Our targeted metabolite analysis further revealed a significant increase in both hepatic and fecal pantothenate concentrations, which contributed to the enhancement of the coenzyme A (CoA)-mediated lipid metabolism pathway. Furthermore, the subsequent population cohort analyses revealed a significant correlation between serum pantothenate levels and the progression of NAFLD, thereby reinforcing its candidacy as a noninvasive diagnostic biomarker. These findings show that 3-FL acts as an effective prebiotic to alleviate NAFLD symptoms, in part by enhancing the gut microbiota-mediated pantothenate/CoA metabolic pathway.

In Vivo Evidence on the Emerging Potential of Non-Digestible Oligosaccharides as Therapeutic Agents in Bacterial and Viral Infections

The issue of antibiotic-resistant bacterial infections, coupled with the rise in viral pandemics and the slow development of new antibacterial and antiviral treatments, underscores the critical need for novel strategies to mitigate the spread of drug-resistant pathogens, enhance the efficacy of existing therapies, and accelerate the discovery and deployment of innovative antimicrobial and antiviral solutions. One promising approach to address these challenges is the dietary supplementation of non-digestible oligosaccharides (NDOs). NDOs, including human milk oligosaccharides (HMOs), play a vital role in shaping and sustaining a healthy gut microbiota. Beyond stimulating the growth and activity of beneficial gut bacteria, NDOs can also interact directly with pathogenic bacteria and viruses. Their antiviral and antibacterial properties arise from their unique interactions with pathogens and their ability to modulate the host's immune system. NDOs can function as decoy receptors, inhibit pathogen growth, bind to bacterial toxins, stimulate the host immune response, exhibit anti-biofilm properties, and enhance barrier protection. However, a notable gap exists in the comprehensive assessment of in vivo and clinical data on this topic. This review aims to provide an in-depth overview of the in vivo evidence related to the antiviral and antibacterial effects of various NDOs and HMOs, with a focus on discussing their possible mechanisms of action.

2'-Fucosyllactose inhibits human norovirus replication in human intestinal enteroids

Human noroviruses (HuNoVs) are the leading cause of acute gastroenteritis worldwide. Currently, there are no targeted antivirals for the treatment of HuNoV infection. Histo-blood group antigens (HBGAs) on the intestinal epithelium are cellular attachment factors for HuNoVs; molecules that block the binding of HuNoVs to HBGAs thus have the potential to be developed as antivirals. Human milk oligosaccharides (HMOs) are glycans in human milk with structures analogous to HBGAs. HMOs have been shown to act as decoy receptors to prevent the attachment of multiple enteric pathogens to host cells. Previous X-ray crystallography studies have demonstrated the binding of HMO 2'-fucosyllactose (2'FL) in the same pocket as HBGAs for some HuNoV strains. We evaluated the effect of 2'FL on the replication of a globally dominant GII.4 Sydney [P16] HuNoV strain using human intestinal enteroids (HIEs) from adults and children. A significant reduction in GII.4 Sydney [P16] replication was seen in duodenal and jejunal HIEs from multiple adult donors, all segments of the small intestine from an adult organ donor, and in two pediatric duodenal HIEs. However, 2'FL did not inhibit HuNoV replication in two infant jejunal HIEs that had significantly lower expression of α1-2-fucosylated glycans. 2'FL can be synthesized in large scale, and safety and tolerance have been assessed previously. Our data suggest that 2'FL has the potential to be developed as a therapeutic for HuNoV gastroenteritis.

IMPORTANCE

Human noroviruses infect the gastrointestinal tract and are a leading cause of acute gastroenteritis worldwide. Common symptoms of norovirus include diarrhea, vomiting, and stomach cramps. Virus shedding and symptoms are prolonged and debilitating in immunocompromised patients. Currently, there are no approved vaccines or targeted antivirals for treating human norovirus infection. Human intestinal enteroids derived from intestinal stem cells allow the successful replication of norovirus in the laboratory and can be used as a physiologically relevant model system to evaluate antivirals. We discovered that 2'-fucosyllactose (2'FL), an oligosaccharide naturally occurring in human milk, inhibits GII.4 norovirus replication in HIEs from multiple donors and thus has the potential to be developed as a therapeutic for human norovirus. These findings have high translational potential since 2'FL from several manufacturers has a "generally recognized as safe" status and can be synthesized on a large scale for immediate application.

Interactions of human milk oligosaccharides with the immune system

Human milk oligosaccharides (HMOs) are abundant, diverse and complex sugars present in human breast milk. HMOs are well-characterized barriers to microbial infection and by modulating the human microbiome they are also thought to be nutritionally beneficial to the infant. The structural variety of over 200 HMOs, including neutral, fucosylated and sialylated forms, allows them to interact with the immune system in various ways. Clinically, HMOs impact allergic diseases, reducing autoimmune and inflammatory responses, and offer beneficial support to the preterm infant immune health. This review examines the HMO composition and associated immunomodulatory effects, including interactions with immune cell receptors and gut-associated immune responses. These immunomodulatory properties highlight the potential for HMO use in early stage immune development and for use as novel immunotherapeutics. HMO research is rapidly evolving and promises innovative treatments for immune-related conditions and improved health outcomes.

Biological effects of combinations of structurally diverse human milk oligosaccharides

Human milk oligosaccharides (HMOs) are a diverse group of structures and an abundant bioactive component of breastmilk that contribute to infant health and development. Preclinical studies indicate roles for HMOs in shaping the infant gut microbiota, inhibiting pathogens, modulating the immune system, and influencing cognitive development. In the past decade, several industrially produced HMOs have become available to fortify infant formula. Clinical intervention trials with manufactured HMOs have begun to corroborate some of the physiological effects reported in preclinical studies, especially modulation of the gut microbiota in the direction of breastfed infants. As more HMOs become commercially available and as HMOs have some shared mechanisms of action, there is a need to better understand the unique and differential effects of individual HMOs and the benefits of combining multiple HMOs. This review focuses on the differential effects of different HMO structural classes and individual structures and presents a scientific rationale for why combining multiple structurally diverse HMOs is expected to exert greater biological effects.

Recent advances of 3-fucosyllactose in health effects and production

Human milk oligosaccharides (HMOs) have been recognized as gold standard for infant development. 3-Fucosyllactose (3-FL), being one of the Generally Recognized as Safe HMOs, represents a core trisaccharide within the realm of HMOs; however, it has received comparatively less attention in contrast to extensively studied 2'-fucosyllactose. The objective of this review is to comprehensively summarize the health effects of 3-FL, including its impact on gut microbiota proliferation, antimicrobial effects, immune regulation, antiviral protection, and brain maturation. Additionally, the discussion also covers the commercial application and regulatory approval status of 3-FL. Lastly, an organized presentation of large-scale production methods for 3-FL aims to provide a comprehensive guide that highlights current strategies and challenges in optimization.

3-Fucosyllactose-mediated modulation of immune response against virus infection

Viral pathogens, particularly influenza and SARS-CoV-2, pose a significant global health challenge. Given the immunomodulatory properties of human milk oligosaccharides, in particular 2'-fucosyllactose and 3-fucosyllactose (3-FL), we investigated their dietary supplementation effects on antiviral responses in mouse models. This study revealed distinct immune modulations induced by 3-FL. RNA-sequencing data showed that 3-FL increased the expression of interferon receptors, such as Interferon Alpha and Beta Receptor (IFNAR) and Interferon Gamma Receptor (IFNGR), while simultaneously downregulating interferons and interferon-stimulated genes, an effect not observed with 2'-fucosyllactose supplementation. Such modulation enhanced antiviral responses in both cell culture and animal models while attenuating pre-emptive inflammatory responses. Nitric oxide concentrations in 3-FL-supplemented A549 cells and mouse lung tissues were elevated exclusively upon infection, reaching 5.8- and 1.9-fold increases over control groups, respectively. In addition, 3-FL promoted leukocyte infiltration into the site of infection upon viral challenge. 3-FL supplementation provided protective efficacy against lethal influenza challenge in mice. The demonstrated antiviral efficacy spanned multiple influenza strains and extended to SARS-CoV-2. In conclusion, 3-FL is a unique immunomodulator that helps protect the host from viral infection while suppressing inflammation prior to infection.

2'-Fucosyllactose Inhibits Human Norovirus Replication in Human Intestinal Enteroids

Human noroviruses (HuNoVs) are the leading cause of acute gastroenteritis worldwide. Currently, there are no targeted antivirals for the treatment of HuNoV infection. Histo-blood group antigens (HBGAs) on the intestinal epithelium are cellular attachment factors for HuNoVs; molecules that block the binding of HuNoVs to HBGAs thus have the potential to be developed as antivirals. Human milk oligosaccharides (HMOs) are glycans in human milk with structures analogous to HBGAs. HMOs have been shown to act as decoy receptors to prevent the attachment of multiple enteric pathogens to host cells. Previous X-ray crystallography studies have demonstrated the binding of HMO 2'-fucosyllactose (2'FL) in the same pocket as HBGAs for some HuNoV strains. We evaluated the effect of 2'FL on the replication of a globally dominant GII.4 Sydney [P16] HuNoV strain using human intestinal enteroids (HIEs) from adults and children. A significant reduction in GII.4 Sydney [P16] replication was seen in duodenal and jejunal HIEs from multiple adult donors, all segments of the small intestine from an adult organ donor and in two pediatric duodenal HIEs. However, 2'FL did not inhibit HuNoV replication in two infant jejunal HIEs that had significantly lower expression of α1-2-fucosylated glycans. 2'FL can be synthesized in large scale, and safety and tolerance have been assessed previously. Our data suggest that 2'FL has the potential to be developed as a therapeutic for HuNoV gastroenteritis.

Targeting host-virus interactions: in silico analysis of the binding of human milk oligosaccharides to viral proteins involved in respiratory infections

Respiratory viral infections, a major public health concern, necessitate continuous development of novel antiviral strategies, particularly in the face of emerging and re-emerging pathogens. In this study, we explored the potential of human milk oligosaccharides (HMOs) as broad-spectrum antiviral agents against key respiratory viruses. By examining the structural mimicry of host cell receptors and their known biological functions, including antiviral activities, we assessed the ability of HMOs to bind and potentially inhibit viral proteins crucial for host cell entry. Our in silico analysis focused on viral proteins integral to host-virus interactions, namely the hemagglutinin protein of influenza, fusion proteins of respiratory syncytial and human metapneumovirus, and the spike protein of SARS-CoV-2. Using molecular docking and simulation studies, we demonstrated that HMOs exhibit varying binding affinities to these viral proteins, suggesting their potential as viral entry inhibitors. This study identified several HMOs with promising binding profiles, highlighting their potential in antiviral drug development. This research provides a foundation for utilizing HMOs as a natural source for designing new therapeutics, offering a novel approach in the fight against respiratory viral infections.