The Immunomodulatory Effects and Applications of Probiotic Lactiplantibacillus plantarum in Vaccine Development

Lactiplantibacillus plantarum (previously known as Lactobacillus plantarum) is a lactic acid bacterium that exists in various niches. L. plantarum is a food-grade microorganism that is commonly considered a safe and beneficial microorganism. It is widely used in food fermentation, agricultural enhancement, and environmental protection. L. plantarum is also part of the normal flora that can regulate the intestinal microflora and promote intestinal health. Some strains of L. plantarum are powerful probiotics that induce and modulate the innate and adaptive immune responses. Due to its outstanding immunoregulatory capacities, an increasing number of studies have examined the use of probiotic L. plantarum strains as natural immune adjuvants or alternative live vaccine carriers. The present review summarizes the main immunomodulatory characteristics of L. plantarum and discusses the preliminary immunological effects of L. plantarum as a vaccine adjuvant and delivery carrier. Different methods for improving the immune capacities of recombinant vector vaccines are also discussed.

Immunoprotective effect of recombinant Lactobacillus plantarum expressing largemouth bass virus MCP on largemouth bass

Largemouth bass virus (LMBV) is an infectious pathogen that causes high mortality rates in largemouth bass, and outbreaks of this virus can significantly harm the aquaculture industry. Currently, no vaccine has been developed that can effectively prevent the transmission of LMBV. In this study, we constructed a recombinant Lactobacillus plantarum (L. plantarum) strain capable of expressing the MCP gene of LMBV and displaying this protein on its surface; then, we evaluated the immunoprotective effect of this recombinant bacterium on largemouth bass. Western blotting, immunofluorescence, and flow cytometry confirmed that MCP was successfully expressed and anchored on the surfaces of NC8 cells. Immunization of largemouth bass with NC8-pSIP409-pgsA'-MCP via the oral feeding route induced CD4, CD8, IL-1β, and IL-6 gene expression. In addition, NC8-pSIP409-pgsA'-MCP at different CFUs increased the survival of largemouth bass after LMBV infection; in particular, NC8-pSIP409-pgsA'-MCP (109 CFU) resulted in approximately 30 % survival. NC8-pSIP409-pgsA'-MCP immunization alleviated the pathological changes in the liver and spleen, exerting a more advantageous protective effect. These data suggest that the recombinant L. plantarum strain NC8-pSIP409-pgsA'-MCP can increase the resistance of largemouth bass to LMBV infection and that this strain is a promising candidate oral vaccine for the prevention of LMBV infection.

Complete genome sequence and anti-obesity potential of Lactiplantibacillus plantarum HOM2217 in 3T3-L1 cells and high-fat diet-fed rats

The global prevalence of obesity is rising year by year, which has become a public health problem worldwide. Many animal and clinical studies have shown that Lactiplantibacillus plantarum is considered an ideal probiotic and potential supplement for the treatment of obesity. In this study, we aimed to complete the genome sequence of L. plantarum HOM2217, which was isolated from human milk, and study its physiological characteristics and anti-obesity effects in 3T3-L1 cells and rats fed a high-fat diet (HFD) to determine its potential as a starter for functional food products. Whole-genome analysis demonstrated that HOM2217 contained a single circular chromosome of 3,267,529 bp with a GC content of 44.5% and one plasmid (62,350 bp) with a GC content of 38.5%. Compared to the reference strains, HOM2217 demonstrated superior tolerance to gastrointestinal conditions, higher adhesion to intestinal epithelial cell lines, potent antimicrobial activity against Enterobacter cloacae ATCC 13047, and effective cholesterol removal ability in vitro. Treatment with heat-killed HOM2217 significantly reduced lipid accumulation and intracellular triglyceride production in 3T3-L1 adipocytes. Daily treatment of HFD-fed rats with HOM2217 for 7 weeks decreased body weight, body weight gain, and body fat without changes in food intake. HOM2217 also significantly increased the serum high-density lipoprotein cholesterol (HDL-C) level, decreased the serum tumor necrosis factor (TNF-α) and increased short-chain fatty acid (SCFA) (formic acid, acetic acid, and butyric acid) levels in the cecum. Thus, HOM2217 could potentially prevent obesity in rats by inhibiting inflammatory responses and regulating lipid metabolism and SCFAs expression. Therefore, HOM2217 has potential as an alternative treatment for obesity.

Complete genome analysis of Lactiplantibacillus plantarum VHProbi P06, a novel probiotic that resists Streptococcus pneumoniae in the upper respiratory tract

The purpose of this study was to screen lactic acid bacteria active against Streptococcus pneumoniae and to analyze the genetic basis of their probiotic functions from the genome. We isolated a novel Lactiplantibacillus plantarum VHProbi P06 from pickles, which showed strong antibacterial activity against S. pneumoniae, adhesion to 5-8F cells, and inhibition of S. pneumoniae colonization in the respiratory tract. Genome of VHProbi P06 was analyzed, we found one class II bacteriocin synthesis gene cluster. Genome of the strain contained 42 adhesion-related protein-coding genes, and implicated three exopolysaccharide biosynthesis gene clusters with low homologous to L. plantarum WCFS1. Moreover, VHProbi P06 possessed 3 intact phage regions and 117 Carbohydrate Active Enzyme genes. By comparing the genomes of five L. plantarum, 275 unique genes were found in VHProbi P06. Finally, the gene prediction was verified, the bacteriocin PlnJK produced by P06 was identified by LC-MS/MS, and the laminar exopolysaccharide with a weight-averaged molecular of 125.37 KDa was also found. This study provides a theoretical basis for the application of VHProbi P06 to the upper respiratory tract to resist pathogenic bacteria.

Bioinformatics and its role in the study of the evolution and probiotic potential of lactic acid bacteria

Due to their numerous well-established applications in the food industry, there have been many studies regarding the adaptation and evolution of lactic acid bacteria (LAB) in a wide variety of hosts and environments. Progress in sequencing technology and continual decreases in its costs have led to the availability of LAB genome sequence data. Bioinformatics has been central to the extraction of valuable information from these raw genome sequence data. This paper presents the roles of bioinformatics tools and databases in understanding the adaptation and evolution of LAB, as well as the bioinformatics methods used in the initial screening of LAB for probiotic potential. Moreover, the advantages, challenges, and limitations of employing bioinformatics for these purposes are discussed.

Effects of novel microecologics combined with traditional Chinese medicine and probiotics on growth performance and health of broilers

In this study, we prepared a kind of novel microecologics, namely Chinese medicine-probiotic compound microecological preparation (CPCMP), which is composed of 5 traditional Chinese medicine herbs (Galla Chinensis, Andrographis paniculata, Arctii Fructus, Glycyrrhizae Radix, and Schizonepeta tenuifolia) fermented by Aspergillus niger and a kind of compound probiotics (Lactobacillus plantarum A37 and L. plantarum MIII). The effects of the CPCMP in broilers on growth performance, serum parameters, immune function, and intestinal health were investigated. A total of 450 one-day-old male Arbor Acres broilers were randomly divided into 6 treatment groups with 5 replicates, 15 birds per replicate. Treatments consisted of: blank control, CPCMP, positive control, commercial CPCMP, traditional Chinese medicine, and probiotics groups, which were birds fed with basal diet supplemented with no extra additives, 0.2% CPCMP, 0.0035% chlortetracycline, 0.2% commercially available CPCMP, 0.2% fermented traditional Chinese medicines, and 0.2% compound probiotics, respectively. CPCMP obviously increased the average body weight and average daily gain (P < 0.05, compared with any other group) and decreased the feed:gain ratio of broilers (P < 0.05, compared with the blank control, commercial CPCMP, traditional Chinese medicine, or probiotics group). Moreover, it significantly increased glutathione peroxidase and secretory immunoglobulin A levels and spleen/bursa indices (P < 0.05 for all, compared with the blank control, commercial CPCMP, traditional Chinese medicine, or probiotics group). Villus heights in duodenum, jejunum, and ileum were also elevated by CPCMP treatment (P < 0.05, compared with any other group). Furthermore, CPCMP substantially increased jejunal mRNA levels of occludin and zonula occludens-1 (P < 0.05, compared with the blank control, positive control, or probiotics group) and facilitated the growth and colonization of beneficial cecal bacteria, such as Olsenella, Barnesiella, and Lactobacillus. Overall results show that the CPCMP prepared in our work contributes to improving growth performance, serum parameters, immune function, and intestinal health of broilers and exerts synergistic effects of traditional Chinese medicines and probiotics to some extent. Our findings suggest that CPCMP is a promising antibiotic substitute in the livestock and poultry industry in the future.

Boosting Vaccine-Elicited Respiratory Mucosal and Systemic COVID-19 Immunity in Mice With the Oral Lactobacillus plantarum

Boosting and prolonging SARS-CoV-2 vaccine-elicited immunity is paramount for containing the COVID-19 pandemic, which wanes substantially within months after vaccination. Here we demonstrate that the unique strain of probiotic Lactobacillus plantarum GUANKE (LPG) could promote SARS-CoV-2-specific immune responses in both effective and memory phases through enhancing interferon signaling and suppressing apoptotic and inflammatory pathways. Interestingly, oral LPG administration promoted SARS-CoV-2 neutralization antibodies even 6 months after immunization. Furthermore, when LPG was given immediately after SARS-CoV-2 vaccine inoculation, specific neutralization antibodies could be boosted >8-fold in bronchoalveolar lavage (BAL) and >2-fold in sera, T-cell responses were persistent and stable for a prolonged period both in BAL and the spleen. Transcriptional analyses showed that oral application of LPG mobilized immune responses in the mucosal and systemic compartments; in particular, gut-spleen and gut-lung immune axes were observed. These results suggest that LPG could be applied in combination with SARS-CoV-2 vaccines to boost and prolong both the effective and memory immune responses in mucosal and systemic compartments, thereby improving the efficacy of SARS-CoV-2 vaccination.

Complete genome analysis of Lactobacillus fermentum YLF016 and its probiotic characteristics

Lactobacillus fermentum (L. fermentum) YLF016 is a well-characterized probiotic with several favorable characteristics. This study aimed to analyze the probiotic characteristics of L. fermentum and uncover the genes implicated in its potential probiotic ability on the base of its genomics features. The complete genome of L. fermentum YLF016 was found to have a circular chromosome of 2,094,354 bp, and 51.46% G + C content without any plasmid. Its chromosome contained 2,130 predicted protein-encoding genes, 58 tRNA, and 15 rRNA-encoding genes. Also, it was found to have many other probiotic properties, such as a high survival rate in the gastrointestinal tract with strong adherence to intestinal cells, antibacterial activity against pathogens, and antioxidant activity. Moreover, the genome sequence analysis demonstrated specific genes coding for carbon metabolism pathway, genetic adaption, stress resistance, and adhesive ability. Further analysis revealed its non-hemolytic activity and its non-functional ability of virulence factors. In conclusion, L. fermentum YLF016 possesses many valuable probiotic properties that refer to its potential probiotic ability.

Application of Lactic Acid Bacteria in Fermentation Processes to Obtain Tannases Using Agro-Industrial Wastes

Bacteria have been used in the food industry to produce flavors, dyes, thickeners, and to increase food value, because bacterial fermentations favor the obtention of different metabolites such as tannins and different nutritional compounds in food. Lactiplantibacillus plantarum was one the first species to be studied for industrial purposes, and its efficacy to obtaining tannins using fermentation processes. Bacterial fermentation helps to obtain a product with an added value of better quality and without the need to use strong solvents that can reduce their quality and safety. To release tannins, it is necessary to subject the substrate to different conditions to activate the enzyme tannin acyl hydrolase (tannase). The tannase-released compounds can have beneficial effects on health such as antioxidant, anticancer and cardioprotective properties, among others. Therefore, this review analyzes tannase release and other metabolites by fermentation processes.