Oral immunization with recombinant Lactococcus lactis NZ9000 expressing human papillomavirus type 16 E7 antigen and evaluation of its immune effects in female C57BL/6 mice

Recombinant L. lactis vaccine LL-plSAM-WAE targeting four virulence factors provides mucosal immunity against H. pylori infection

BACKGROUND

Helicobacter pylori (H. pylori) causes chronic gastric disease. An efficient oral vaccine would be mucosa-targeted and offer defense against colonization of invasive infection in the digestive system. Proteolytic enzymes and acidic environment in the gastrointestinal tract (GT) can, however, reduce the effectiveness of oral vaccinations. For the creation of an edible vaccine, L. lactis has been proposed as a means of delivering vaccine antigens.

RESULTS

We developed a plSAM (pNZ8148-SAM) that expresses a multiepitope vaccine antigen SAM-WAE containing Urease, HpaA, HSP60, and NAP extracellularly (named LL-plSAM-WAE) to increase the efficacy of oral vaccinations. We then investigated the immunogenicity of LL-plSAM-WAE in Balb/c mice. Mice that received LL-plSAM-WAE or SAM-WAE with adjuvant showed increased levels of antibodies against H. pylori, including IgG and sIgA, and resulted in significant reductions in H. pylori colonization. Furthermore, we show that SAM-WAE and LL-plSAM-WAE improved the capacity to target the vaccine to M cells.

CONCLUSIONS

These findings suggest that recombinant L. lactis could be a promising oral mucosa vaccination for preventing H. pylori infection.

SARS-CoV-2 Spike Protein-Expressing Enterococcus for Oral Vaccination: Immunogenicity and Protection

The declaration of the conclusion of the COVID-19 pandemic notwithstanding, coronavirus remains prevalent in circulation, and the potential emergence of novel variants of concern introduces the possibility of new outbreaks. Moreover, it is not clear how quickly and to what extent the effectiveness of vaccination will decline as the virus continues to mutate. One possible solution to combat the rapidly mutating coronavirus is the creation of safe vaccine platforms that can be rapidly adapted to deliver new, specific antigens in response to viral mutations. Recombinant probiotic microorganisms that can produce viral antigens by inserting specific viral DNA fragments into their genome show promise as a platform and vector for mucosal vaccine antigen delivery. The authors of this study have developed a convenient and universal technique for inserting the DNA sequences of pathogenic bacteria and viruses into the gene that encodes the pili protein of the probiotic strain E. faecium L3. The paper presents data on the immunogenic properties of two E. faecium L3 vaccine strains, which produce two different fragments of the coronavirus S1 protein, and provides an assessment of the protective efficacy of these oral vaccines against coronavirus infection in Syrian hamsters.

The potential use of bacteria and bacterial derivatives as drug delivery systems for viral infection

Viral infections in humans are responsible for fatalities worldwide and contribute to the incidence of various human ailments. Controllable targeted medicine delivery against many illnesses, including viral infection, may be significantly aided by using bacteria and bacteria-derived products. They may accumulate in diseased tissues despite physical obstacles, where they can launch antiviral immunity. The ability to genetically and chemically modify them means that vaccinations against viral infections may be manufactured and delivered to affected tissues more safely and effectively. The objective of this study is to provide an overview of the latest advancements in the field of utilizing bacteria and bacterial derivatives as carriers for administering medication to treat viral diseases such as SARS-CoV-2, hepatitis B virus, hepatitis C virus, human immunodeficiency virus, human papillomavirus, influenza, and Ebola virus.

Potential links between the microbiota and T cell immunity determine the tumor cell fate

The central role of the microbiota as a pivotal factor regulating anti-tumor immune responses has recently been appreciated. Increasing evidence has put a spotlight on the connection of microbiota to T cells, by showing impaired effector and/or memory responses in germ-free (GF) mice or in the presence of dysbiotic communities, and association with tumor growth and overall survival (OS). These observations also have significant implications for anti-tumor therapy and vaccination, suggesting that the communication between T cells and the microbiota involves soluble mediators (microbiota-derived metabolites) that influence various functions of T cells. In addition, there is growing appreciation of the role of bacterial translocation into the peritumoral milieu from the intestinal tract, as well as of locally developed tumor microbial communities, spatially separated from the gut microbiota, in shaping the tumor microbiome. Collectively, these findings have added new support to the idea that tonic inputs mirroring the existence of tumor microbiome could regulate the function of tumor-infiltrating T cells and tissue-resident memory T (TRM) cells. In this review, we focus on recent advances and aspects of these active areas of investigation and provide a comprehensive overview of the unique mechanisms that play a pivotal role in the regulation of anti-tumor immunity by the microbiota, some of which could be of particular relevance for addressing problems caused by tumor heterogeneity. It is our hope that this review will provide a theoretical foundation for future investigations in this area.

Mucosal vaccination: onward and upward

INTRODUCTION

The unique mucosal immune system allows the generation of robust protective immune responses at the front line of pathogen encounters. The needle-free delivery route and cold chain-free logistic requirements also provide additional advantages in ease and economy. However, the development of mucosal vaccines faces several challenges, and only a handful of mucosal vaccines are currently licensed. These vaccines are all in the form of live attenuated or inactivated whole organisms, whereas no subunit-based mucosal vaccine is available.

AREAS COVERED

The selection of antigen, delivery vehicle, route and adjuvants for mucosal vaccination are highly important. This is particularly crucial for subunit vaccines, as they often fail to elicit strong immune responses. Emerging research is providing new insights into the biological and immunological uniqueness of mucosal tissues. However, many aspects of the mucosal immunology still await to be investigated.

EXPERT OPINION

This article provides an overview of the current understanding of mucosal vaccination and discusses the remaining knowledge gaps. We emphasize that because of the potential benefits mucosal vaccines can bring from the biomedical, social and economic standpoints, the unmet goal to achieve mucosal vaccine success is worth the effort.

Immunomodulatory action of Lactococcuslactis

Fermented foods are gaining popularity due to health-promoting properties with high levels of nutrients, phytochemicals, bioactive compounds, and probiotic microorganisms. Due to its unique fermentation process, Lactococcus lactis plays a key role in the food business, notably in the manufacturing of dairy products. The superior biological activities of L. lactis in these functional foods include anti-inflammatory and immunomodulatory capabilities. L. lactis boosted growth performance, controlled amino acid profiles, intestinal immunology, and microbiota. Besides that, the administration of L. lactis increased the rate of infection clearance. Innate and acquired immune responses would be upregulated in both local and systemic compartments, resulting in these consequences. L. lactis is often employed in the food sector and is currently being exploited as a delivery vehicle for biological research. These bacteria are being eyed as potential candidates for biotechnological applications. With this in mind, we reviewed the immunomodulatory effects of different L. lactis strains.

Current Status and Future Directions of Bacteria-Based Immunotherapy

With the in-depth understanding of the anti-cancer immunity, immunotherapy has become a promising cancer treatment after surgery, radiotherapy, and chemotherapy. As natural immunogenicity substances, some bacteria can preferentially colonize and proliferate inside tumor tissues to interact with the host and exert anti-tumor effect. However, further research is hampered by the infection-associated toxicity and their unpredictable behaviors in vivo. Due to modern advances in genetic engineering, synthetic biology, and material science, modifying bacteria to minimize the toxicity and constructing a bacteria-based immunotherapy platform has become a hotspot in recent research. This review will cover the inherent advantages of unedited bacteria, highlight how bacteria can be engineered to provide greater tumor-targeting properties, enhanced immune-modulation effect, and improved safety. Successful applications of engineered bacteria in cancer immunotherapy or as part of the combination therapy are discussed as well as the bacteria based immunotherapy in different cancer types. In the end, we highlight the future directions and potential opportunities of this emerging field.

Bacterial membrane vesicles for vaccine applications

Vaccines have been highly successful in the management of many diseases. However, there are still numerous illnesses, both infectious and noncommunicable, for which there are no clinically approved vaccine formulations. While there are unique difficulties that must be overcome in the case of each specific disease, there are also a number of common challenges that have to be addressed for effective vaccine development. In recent years, bacterial membrane vesicles (BMVs) have received increased attention as a potent and versatile vaccine platform. BMVs are inherently immunostimulatory and are able to activate both innate and adaptive immune responses. Additionally, BMVs can be readily taken up and processed by immune cells due to their nanoscale size. Finally, BMVs can be modified in a variety of ways, including by genetic engineering, cargo loading, and nanoparticle coating, in order to create multifunctional platforms that can be leveraged against different diseases. Here, an overview of the interactions between BMVs and immune cells is provided, followed by discussion on the applications of BMV vaccine nanotechnology against bacterial infections, viral infections, and cancers.

Light-Sensitive Lactococcus lactis for Microbe-Gut-Brain Axis Regulating via Upconversion Optogenetic Micro-Nano System

The discovery of the gut-brain axis has proven that brain functions can be affected by the gut microbiota's metabolites, so there are significant opportunities to explore new tools to regulate gut microbiota and thus work on the brain functions. Meanwhile, engineered bacteria as oral live biotherapeutic agents to regulate the host's healthy homeostasis have attracted much attention in microbial therapy. However, whether this strategy is able to remotely regulate the host's brain function in vivo has not been investigated. Here, we engineered three blue-light-responsive probiotics as oral live biotherapeutic agents. They are spatiotemporally delivered and controlled by the upconversion optogenetic micro-nano system. This micro-nano system promotes the small intestine targeting and production of the exogenous L. lactis in the intestines, which realizes precise manipulation of brain functions including anxiety behavior, Parkinson's disease, and vagal afferent. The noninvasive and real-time probiotic intervention strategy makes the communiation from the gut to the host more controllable, which will enable the potential for engineered microbes accurately and effectively regulating a host's health.

Probiotic-Based Vaccines May Provide Effective Protection against COVID-19 Acute Respiratory Disease

Severe acute respiratory syndrome coronavirus 2 virus (SARS-CoV-2) infection, the causative agent of COVID-19, now represents the sixth Public Health Emergency of International Concern (PHEIC)—as declared by the World Health Organization (WHO) since 2009. Considering that SARS-CoV-2 is mainly transmitted via the mucosal route, a therapy administered by this same route may represent a desirable approach to fight SARS-CoV-2 infection. It is now widely accepted that genetically modified microorganisms, including probiotics, represent attractive vehicles for oral or nasal mucosal delivery of therapeutic molecules. Previous studies have shown that the mucosal administration of therapeutic molecules is able to induce an immune response mediated by specific serum IgG and mucosal IgA antibodies along with mucosal cell-mediated immune responses, which effectively concur to neutralize and eradicate infections. Therefore, advances in the modulation of mucosal immune responses, and in particular the use of probiotics as live delivery vectors, may encourage prospective studies to assess the effectiveness of genetically modified probiotics for SARS-CoV-2 infection. Emerging trends in the ever-progressing field of vaccine development re-emphasize the contribution of adjuvants, along with optimization of codon usage (when designing a synthetic gene), expression level, and inoculation dose to elicit specific and potent protective immune responses. In this review, we will highlight the existing pre-clinical and clinical information on the use of genetically modified microorganisms in control strategies against respiratory and non-respiratory viruses. In addition, we will discuss some controversial aspects of the use of genetically modified probiotics in modulating the cross-talk between mucosal delivery of therapeutics and immune system modulation.

Plasmid Replicons for the Production of Pharmaceutical-Grade pDNA, Proteins and Antigens by Lactococcus lactis Cell Factories

The Lactococcus lactis bacterium found in different natural environments is traditionally associated with the fermented food industry. But recently, its applications have been spreading to the pharmaceutical industry, which has exploited its probiotic characteristics and is moving towards its use as cell factories for the production of added-value recombinant proteins and plasmid DNA (pDNA) for DNA vaccination, as a safer and industrially profitable alternative to the traditional Escherichia coli host. Additionally, due to its food-grade and generally recognized safe status, there have been an increasing number of studies about its use in live mucosal vaccination. In this review, we critically systematize the plasmid replicons available for the production of pharmaceutical-grade pDNA and recombinant proteins by L. lactis. A plasmid vector is an easily customized component when the goal is to engineer bacteria in order to produce a heterologous compound in industrially significant amounts, as an alternative to genomic DNA modifications. The additional burden to the cell depends on plasmid copy number and on the expression level, targeting location and type of protein expressed. For live mucosal vaccination applications, besides the presence of the necessary regulatory sequences, it is imperative that cells produce the antigen of interest in sufficient yields. The cell wall anchored antigens had shown more promising results in live mucosal vaccination studies, when compared with intracellular or secreted antigens. On the other side, engineering L. lactis to express membrane proteins, especially if they have a eukaryotic background, increases the overall cellular burden. The different alternative replicons for live mucosal vaccination, using L. lactis as the DNA vaccine carrier or the antigen producer, are critically reviewed, as a starting platform to choose or engineer the best vector for each application.

Twenty years of research on HPV vaccines based on genetically modified lactic acid bacteria: an overview on the gut-vagina axis

Most cervical cancer (CxCa) are related to persistent infection with high-risk human papillomavirus (HR-HPV) in the cervical mucosa, suggesting that an induction of mucosal cell-mediated immunity against HR-HPV oncoproteins can be a promising strategy to fight HPV-associated CxCa. From this perspective, many pre-clinical and clinical trials have proved the potential of lactic acid bacteria (LAB) genetically modified to deliver recombinant antigens to induce mucosal, humoral and cellular immunity in the host. Altogether, the outcomes of these studies suggest that there are several key factors to consider that may offer guidance on improvement protein yield and improving immune response. Overall, these findings showed that oral LAB-based mucosal HPV vaccines expressing inducible surface-anchored antigens display a higher potential to induce particularly specific systemic and mucosal cytotoxic cellular immune responses. In this review, we describe all LAB-based HPV vaccine investigations by reviewing databases from international studies between 2000 and 2020. Our aim is to promote the therapeutic HPV vaccines knowledge and to complete the gaps in this field to empower scientists worldwide to make proper decisions regarding the best strategies for the development of therapeutic HPV vaccines.

A cutting-edge immunoinformatics approach for design of multi-epitope oral vaccine against dreadful human malaria

Human malaria is a pathogenic disease mainly caused by Plasmodium falciparum, which was responsible for about 405,000 deaths globally in the year 2018. To date, several vaccine candidates have been evaluated for prevention, which failed to produce optimal output at various preclinical/clinical stages. This study is based on designing of polypeptide vaccines (PVs) against human malaria that cover almost all stages of life-cycle of Plasmodium and for the same 5 genome derived predicted antigenic proteins (GDPAP) have been used. For the development of a multi-immune inducer, 15 PVs were initially designed using T-cell epitope ensemble, which covered >99% human population as well as linear B-cell epitopes with or without adjuvants. The immune simulation of PVs showed higher levels of T-cell and B-cell activities compared to positive and negative vaccine controls. Furthermore, in silico cloning of PVs and codon optimization followed by enhanced expression within Lactococcus lactis host system was also explored. Although, the study has sound theoretical and in silico findings, the in vitro/in vivo evaluation seems imperative to warrant the immunogenicity and safety of PVs towards management of P. falciparum infection in the future.

The First Clinical Use of a Recombinant Lactococcus lactis Expressing Human Papillomavirus Type 16 E7 Oncogene Oral Vaccine: A Phase I Safety and Immunogenicity Trial in Healthy Women Volunteers

A dose-escalation, randomized, double-blind, placebo-controlled phase I clinical trial was performed in healthy Iranian volunteer women to assess the safety, tolerability, and immunogenicity of NZ8123-HPV16-optiE7 vaccine involving recombinant Lactococcus lactis expressing the codon-optimized human papillomavirus (HPV)-16 E7 oncogene. Fifty-five eligible subjects were divided into 6 cohorts based on the dosages (1 × 10⁹, 5 × 10⁹, and 1 × 10¹⁰ CFU/mL) of either vaccine or placebo, which were administrated orally a total of 4 times at weeks 1, 2, 4, and 8. Then, adverse events, specific serum IgG and vaginal IgA, and E7-specific IFNγ-secreting CD8⁺ CTL responses were evaluated. The vaccination was well tolerated by 40 subjects who completed the immunization schedule, and no serious adverse effects were reported. The IgG and IgA levels peaked at day 60, and the levels for the 5 × 10⁹ CFU/mL and 1 × 10¹⁰ CFU/mL dose groups were higher than those for the 1 × 10⁹ CFU/mL dose group. Time-to-peak stimulation in E7-specific IFNγ-secreting CD8⁺ CTL responses was seen in cervical lymphocytes 1 month after the last vaccination. Again, no significant increase was seen in the peripheral blood mononuclear cells (PBMC) of the same volunteers. CTL responses in cervical lymphocytes and PBMCs at day 90 were markedly higher in the 5 × 10⁹ and 1 × 10¹⁰ CFU/mL groups than in the 1 × 10⁹ CFU/mL group, demonstrating the dose dependency of NZ8123-HPV16-optiE7 vaccine following oral administration. The 6-month follow-up revealed that antibody levels decreased up to day 240; nevertheless, long-term E7-specific IFNγ-secreting CD8⁺ CTL responses were recorded during follow-up. Overall, the safety and immunogenicity profile achieved in this study encourages further phase II trials with the 5 × 10⁹ CFU/mL dose vaccine.

Phase 1 Safety and Immunogenicity Trial of Recombinant Lactococcus lactis Expressing Human Papillomavirus Type 16 E6 Oncoprotein Vaccine

The present study purposed to investigate the safety, tolerability, and immunogenicity of the therapeutic NZ8123-HPV16-optiE6 vaccine, following oral vaccination. The safety and tolerability were evaluated. Specific serum immunoglobulin G (IgG) and vaginal IgA antibodies were calculated by ELISA, and E6-specific IFN-γ-secreting T cells were counted by enzyme-linked immune absorbent spot (ELISpot) assay in cervical lymphocytes and PBMC samples. The vaccine was well tolerated, and no serious adverse effects were observed in vaccine recipients. Statistical analysis showed that all vaccine groups had significant increases in antibody levels at day 60 after baseline. The time to peak activation in E6-specific IFN-γ-secreting CD8⁺ CTL responses was seen at month 1 after last vaccination. According to the results, the humoral immune and cell-mediated responses for the vaccine groups that received 5 × 10⁹ and 1 × 10¹⁰ CFU/mL of vaccine were similar and were higher than those of the 1 × 10⁹ CFU/mL group, indicating the dose-dependency of the NZ8123-HPV16-optiE6 vaccine following oral administration. Low antibody levels compared with the placebo groups were recorded at month 6 after the last vaccination. Interestingly, long-term E6-specific CTL responses were observed during follow-up. It was concluded that oral immunization with the NZ8123-HPV-16-optiE6 vaccine is safe, induces persistent immunity, and is reasonably well tolerated.

E. coli Enterotoxin LtB Enhances Vaccine-Induced Anti-H. pylori Protection by Promoting Leukocyte Migration into Gastric Mucus via Inflammatory Lesions

Current studies indicate that the anti-H. pylori protective efficacy of oral vaccines to a large extent depends on using mucosal adjuvants like E. coli heat-lable enterotoxin B unit (LtB). However, the mechanism by which Th17/Th1-driven cellular immunity kills H. pylori and the role of LtB remains unclear. Here, two L.lactis strains, expressing H. pylori NapA and LtB, respectively, were orally administrated to mice. As observed, the administration of LtB significantly enhanced the fecal SIgA level and decreased gastric H. pylori colonization, but also markedly aggravated gastric inflammatory injury. Both NapA group and NapA+LtB group had elevated splenocyte production of IL-8, IL-10, IL-12, IL-17, IL-23 and INF-γ. Notably, gastric leukocytes' migration or leakage into the mucus was observed more frequently in NapA+LtB group than in NapA group. This report is the first that discusses how LtB enhances vaccine-induced anti-H. pylori efficacy by aggravating gastric injury and leukocytes' movement into the mucus layer. Significantly, it brings up a novel explanation for the mechanism underlying mucosal cellular immunity destroying the non-invasive pathogens. More importantly, the findings suggest the necessity to further evaluate LtB's potential hazards to humans before extending its applications. Thus, this report can provide considerable impact on the fields of mucosal immunology and vaccinology.

Recombinant invasive Lactobacillus plantarum expressing fibronectin binding protein A induce specific humoral immune response by stimulating differentiation of dendritic cells

Recombinant lactic acid bacteria (LAB), especially Lactococcus lactis, have been genetically engineered to express heterogeneous invasion proteins, such as the fibronectin binding protein A (FnBPA) from Staphylococcus aureus, to increase the invasion ability of the host strains, indicating a promising approach for DNA vaccine delivery. The presence of FnBPA has been also shown to be an adjuvant for co-delivered antigens, however, the underlying mechanisms are still not clear. To explore the above underlying mechanisms, in this study, we constructed a novel Lactobacillus plantarum strain with surface displayed FnBPA, which could significantly improve the adhesion and invasion ratios of L. plantarum strain on a porcine intestinal epithelial cell line (IPEC-J2) about two-fold compared with the empty vector. At the same time, the presence of FnBPA significantly stimulated the differentiation of bone marrow-derived dendritic cells (DCs) and increased the secretion of interleukin (IL)-6 and mRNA level of IL-6 gene, which were proved by flow cytometry, enzyme-linked immunosorbent assay (ELISA) and quantitative reverse transcription PCR (qRT-PCR). With regard to in vivo study, the presence of FnBPA significantly stimulated the differentiation of DCs in the Peyer's patch (PP) and the percentages of IL-4⁺ and IL-17A⁺ T helper (Th) cells of splenocytes in flow cytometry assay. In consistent with these results, the levels of IL-4 and IL-17A in serum as measured via ELISA also increased in mice treated with FnBPA⁺ L. plantarum. Finally, the FnBPA strain increased the production of B220⁺ B cells in mesenteric lymph node (MLN) and PP and the levels of FnBPA-specific IgG and sIgA antibodies, indicating the its possible application in vaccine field. This study demonstrated that the invasive L. plantarum with surface displayed FnBPA could modulate host immune response by stimulating the differentiation of DCs and Th cells which could possibly be responsive for the adjuvant effects of FnBPA.

Extracellular overproduction of E7 oncoprotein of Iranian human papillomavirus type 16 by genetically engineered Lactococcus lactis

Background

We aimed at constructing Lactococcus lactis strains expressing HPV-16 recombinant E7 (rE7) oncoprotein and examining its overproduction ability followed by optimizing batch and fed-batch fermentations. Thereafter, in order to assess the immunogenicity of recombinant L. lactis cells, C57BL/6 mice were immunized by oral gavage.

Results

The results suggested that recombinant strains harboring optiE7 and E7 genes produced a maximum of 4.84 and 1.91 μg/mL of rE7 in static flask experiments, while the corresponding strains gave a maximum yield of 35.49 and 14.24 μg/mL in batch experiments, respectively. Fed-batch study indicated that the concentration of rE7 protein significantly increased after feeding yeast extract plus GM17 medium. The rE7 production of the best performing strains was 2.09- and 1.48-fold higher than that of the strains during the batch fermentation. Furthermore, biomass levels were 1.98- and 1.92-fold higher than those in batch cultivation. Oral immunization of C57BL/6 mice with recombinant L. lactis produced significant specific IgG and IgA antibody responses in serum and vaginal fluids, respectively. Our outcomes suggest that vaccination with L. lactis expressing rE7 can generate significant protective effects against E7-expressing cell line. Also, our study provides evidence that the presence of large amounts of E7-specific CD4⁺ T helper and CD8⁺ T cell precursors was stimulated. Significantly higher frequencies of HPV-16 E7 specific IL-2- and IFN-γ-secreting T cells were detected in antigen-stimulated splenocytes and intestinal mucosal lymphocytes, when compared to the control groups.

Conclusions

We conclude that optimization of culture conditions along with recombinant protein expression can highly stimulate both specific humoral and cell-mediated immune responses in mice after oral immunization. These promising results represent a step towards fast-tracking a vaccine against HPV-16-associated cervical cancer.