Passive protection of mice pups through oral or intranasal immunization of dams with recombinant Lactobacillus casei vaccine against ETEC F41

Expression of heterologous heparan sulphate binding protein of Helicobacter pylori on the surface of Lactobacillus rhamnosus GG

Helicobacter pylori (H. pylori) is one of most commonly found pathogen in the stomach. In spite of emergence of different treatment strategies, H. pylori infection remains difficult to treat. The bioengineered probiotic lactobacilli that could displace H. pylori and simultaneously present immunogenic peptides such as heparan sulphate binding protein (Hsbp) to elicit immune response could emerge as a potential therapeutic agent. The aim of this study was to discover the anti-H. pylori activities and faster exclusion of H. pylori from host cells by the recombinant strain of Lactobacillus expressing the immunogenic Hsbp protein. The results were promising and showed a 65% reduction in H. pylori adhesion after two hours of pre-incubation with recombinant-LGG and HeLa S3 cells, followed by the adhesion of H. pylori pathogen (P < 0.002). Additionally, 36% and 39% reduction were examined in co-incubation and post-incubation with recombinant-LGG, respectively. When challenged with H. pylori, the proinflammatory cytokine expression was also down regulated in recombinant-LGG treated HeLa S3 cells. This promising result provides a new insight of bioengineered probiotic lactobacilli which could displace H. pylori and simultaneously has immunogenic properties thereby may be useful to prevent H. pylori infection.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03428-4.

Peptide-Based Vaccines for Tuberculosis

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis. As a result of the coronavirus disease 2019 (COVID-19) pandemic, the global TB mortality rate in 2020 is rising, making TB prevention and control more challenging. Vaccination has been considered the best approach to reduce the TB burden. Unfortunately, BCG, the only TB vaccine currently approved for use, offers some protection against childhood TB but is less effective in adults. Therefore, it is urgent to develop new TB vaccines that are more effective than BCG. Accumulating data indicated that peptides or epitopes play essential roles in bridging innate and adaptive immunity and triggering adaptive immunity. Furthermore, innovations in bioinformatics, immunoinformatics, synthetic technologies, new materials, and transgenic animal models have put wings on the research of peptide-based vaccines for TB. Hence, this review seeks to give an overview of current tools that can be used to design a peptide-based vaccine, the research status of peptide-based vaccines for TB, protein-based bacterial vaccine delivery systems, and animal models for the peptide-based vaccines. These explorations will provide approaches and strategies for developing safer and more effective peptide-based vaccines and contribute to achieving the WHO's End TB Strategy.

Prophylactic vaccine delivery systems against epidemic infectious diseases

Prophylactic vaccines have evolved from traditional whole-cell vaccines to safer subunit vaccines. However, subunit vaccines still face problems, such as poor immunogenicity and low efficiency, while traditional adjuvants are usually unable to meet specific response needs. Advanced delivery vectors are important to overcome these barriers; they have favorable safety and effectiveness, tunable properties, precise location, and immunomodulatory capabilities. Nevertheless, there has been no systematic summary of the delivery systems to cover a wide range of infectious pathogens. We herein summarized and compared the delivery systems for major or epidemic infectious diseases caused by bacteria, viruses, fungi, and parasites. We also included the newly licensed vaccines (e.g., COVID-19 vaccines) and those close to licensure. Furthermore, we highlighted advanced delivery systems with high efficiency, cross-protection, or long-term protection against epidemic pathogens, and we put forward prospects and thoughts on the development of future prophylactic vaccines.

Probiotics as Adjuvants in Vaccine Strategy: Is There More Room for Improvement?

BACKGROUND

It has been recognized that microbiota plays a key role in shaping immune system maturation and activity. Since probiotic administration influences the microbiota composition and acts as a biological response modifier, the efficacy of an adjuvant for boosting vaccine-specific immunity is investigated.

METHODS

A review of the literature was performed, starting from the mechanisms to laboratory and clinical evidence.

RESULTS

The mechanisms, and in vitro and animal models provide biological plausibility for microbiota use. Probiotics have been investigated as adjuvants in farm conditions and as models to understand their potential in human vaccinations with promising results. In human studies, although probiotics were effective in ameliorating seroconversion to vaccines for influenza, rotavirus and other micro-organisms, the results for clinical use are still controversial, especially in particular settings, such as during the last trimester of pregnancy.

CONCLUSION

Although this topic remains controversial, the use of probiotics as adjuvant factors in vaccination represents a strategic key for different applications. The available data are deeply influenced by heterogeneity among studies in terms of strains, timing and duration of administration, and patients. Although these do not allow us to draw definitive conclusions, probiotics as adjuvants in vaccination should be considered in future studies, especially in the elderly and in children, where vaccine effectiveness and duration of immunization really matter.

Re-evaluation of a Neonatal Mouse Model of Infection With Enterotoxigenic Escherichia coli

Enterotoxigenic E. coli (ETEC) is a common cause of diarrhea in children in low- and middle-income countries, and in travelers to these countries. ETEC is also an important cause of morbidity and premature mortality in piglets, calves, goat kids and lambs. The major virulence determinants of ETEC are enterotoxins and colonization factors, which enable the pathogen to colonize the small intestine and deliver enterotoxins, such as the heat-stable enterotoxins, STp and STh, to epithelial cells. Because most ETEC strains are host-specific, there are few convenient animal models to investigate the pathogenesis of ETEC infections or to evaluate specific anti-ETEC interventions, such as drugs and vaccines. An exception is ETEC strains bearing F41 pili, which mediate intestinal colonization of various young animals, including neonatal mice, to cause disease and in some cases death. In this study, we used the archetypal F41-producing bovine ETEC strain, B41 (O101:NM; K99, F41, STp) to validate and further explore the contribution of F41 and STp to bacterial virulence. By using targeted gene deletion and trans-complementation studies, augmented by whole genome sequencing, and in vitro and animal studies of virulence, we established that F41 mediates colonization of the mouse intestine and is essential for bacterial virulence. In addition, we showed for the first time that STp is as important as F41 for virulence. Together, these findings validate the use of neonatal mice to study the pathogenesis of F41-bearing ETEC and to investigate possible specific anti-ETEC interventions including vaccines that target heat-stable enterotoxins.

Harnessing the potential of Lactobacillus species for therapeutic delivery at the lumenal-mucosal interface

Lactobacillus species have been studied for over 30 years in their role as commensal organisms in the human gut. Recently there has been a surge of interest in their abilities to natively and recombinantly stimulate immune activities, and studies have identified strains and novel molecules that convey particular advantages for applications as both immune adjuvants and immunomodulators. In this review, we discuss the recent advances in Lactobacillus-related activity at the gut/microbiota interface, the efforts to probe the boundaries of the direct and indirect therapeutic potential of these bacteria, and highlight the continued interest in harnessing the native capacity for the production of biogenic compounds shown to influence nervous system activity. Taken together, these aspects underscore Lactobacillus species as versatile therapeutic delivery vehicles capable of effector production at the lumenal-mucosal interface, and further establish a foundation of efficacy upon which future engineered strains can expand.

Oral immunization with a recombinant Lactobacillus expressing CK6 fused with VP2 protein against IPNV in rainbow trout (Oncorhynchus mykiss)

Infectious pancreatic necrosis virus (IPNV) infects wild and cultured salmonid fish causing high mortality with serious economic losses to salmonid aquaculture. Ideally, the method of oral immunization should prevent the infection of rainbow trout juveniles with IPNV. In the present study, genetically engineered Lactobacillus casei 393 pPG-612-VP2/L. casei 393 and pPG-612-CK6-VP2/L. casei 393 constitutively expressing VP2 protein of IPNV were constructed. The recombinant strains pPG-612-CK6-VP2/L. casei 393 and pPG-612-VP2/L. casei 393 were orally administrated to juvenile rainbow trouts, and significant titers of IgM and IgT of pPG-612-CK6-VP2/L. casei 393 were observed. The results demonstrate that the recombinants could elicit both local mucosal and systemic immune responses. The proliferation of spleen lymphocytes in trouts immunized with pPG-612-CK6-VP2/L. casei 393 showed that the recombinant strain could induce a strong cellular immune response. The IL-1β, IL-8, CK6, MHC-II, Mx, β-defensin, and TNF-1α levels in the spleen and gut suggest that the target molecular chemokine has the ability to attract relevant immune cells to participate in the inflammatory response and enhance the function of the innate immune response. Additionally, the pPG-612-CK6-VP2/L. casei 393 induced the expression of cytokines, which have the effect of promoting inflammation to drive the differentiation of macrophages and clear target cells. After challenging with IPNV, the reduction in viral load caused by pPG-612-CK6-VP2/L. casei 393 was significantly higher than that of the other groups. Thus, the recombinant pPG-612-CK6-VP2/L. casei 393 is a promising candidate for the development of an oral vaccine against IPNV.

Lactobacillus Mucosal Vaccine Vectors: Immune Responses against Bacterial and Viral Antigens

Lactic acid bacteria (LAB) have been utilized since the 1990s for therapeutic heterologous gene expression. The ability of LAB to elicit an immune response against expressed foreign antigens has led to their exploration as potential mucosal vaccine candidates. LAB vaccine vectors offer many attractive advantages: simple, noninvasive administration (usually oral or intranasal), the acceptance and stability of genetic modifications, relatively low cost, and the highest level of safety possible. Experimentation using LAB of the genus Lactobacillus has become popular in recent years due to their ability to elicit strong systemic and mucosal immune responses. This article reviews Lactobacillus vaccine constructs, including Lactobacillus species, antigen expression, model organisms, and in vivo immune responses, with a primary focus on viral and bacterial antigens.

Gene editing and genetic engineering approaches for advanced probiotics: A review

The applications of probiotics are significant and thus resulted in need of genome analysis of probiotic strains. Various omics methods and systems biology approaches enables us to understand and optimize the metabolic processes. These techniques have increased the researcher's attention towards gut microbiome and provided a new source for the revelation of uncharacterized biosynthetic pathways which enables novel metabolic engineering approaches. In recent years, the broad and quantitative analysis of modified strains relies on systems biology tools such as in silico design which are commonly used methods for improving strain performance. The genetic manipulation of probiotic microorganisms is crucial for defining their role in intestinal microbiota and exploring their beneficial properties. This review describes an overview of gene editing and systems biology approaches, highlighting the advent of omics methods which allows the study of new routes for studying probiotic bacteria. We have also summarized gene editing tools like TALEN, ZFNs and CRISPR-Cas that edits or cleave the specific target DNA. Furthermore, in this review an overview of proposed design of advanced customized probiotic is also hypothesized to improvise the probiotics.

Development of an Escherichia coli-Lactobacillus casei shuttle vector for heterologous protein expression in Lactobacillus casei

There is an increasing interest to develop various lactic acid bacteria (LAB) species as mucosal delivery vehicles, for which the development of a variety of cloning and expression systems for these bacteria is of primary importance. This study reports the complete nucleotide sequence of the cryptic plasmid pRCEID7.6 derived from the chicken probiotic LAB strain Lactobacillus casei TISTR1341. Sequence analysis and comparison showed that pRCEID7.6 is composed of nine putative open reading frames. The replicon origin of pRCEID7.6 consisted of untranslated origin of replication and translated replication protein B sequences. This region was used to construct Escherichia coli/L. casei shuttle vectors carrying erythromycin and chloramphenicol resistance genes as selective markers. Segregation and structural stability of the vectors in L. casei was sufficient for most genetic applications. The feasibility of this vector for heterologous protein expression in L. casei was determined by cloning in pRCEID-LC7.6, the gene encoding the nucleocapsid protein (NP), from the influenza A virus under the control of the homologous promoter from the lactate dehydrogenase gene. L. casei carrying this recombinant plasmid was shown to successfully express the NP protein. Therefore, this shuttle vector can be used for further study in the development of mucosal delivery vehicles.