Bacterial Vector Research Articles

Pyrite cloning: a single tube and programmed reaction cloning with restriction enzymes

BackgroundInsertion of engineered DNA fragments into bacterial vectors is the foundation of recombinant DNA technology, yet existing methods are still laborious, require many steps, depend on specific vector configuration, or require expensive reagents.ResultsWe have developed a method, called “Pyrite” cloning that combines the traditional restriction enzyme digestion and ligation reaction in a single tube and uses a programmed thermocycler reaction, allowing rapid and flexible cloning in a single tube. After the Pyrite reaction and transformation, approximately 50% colonies contain the expected insert, which can be easily and quickly determined by colony PCR or blue-white colony screening. We also demonstrated that Pyrite cloning can be applied for different cloning purposes.ConclusionsThe Pyrite cloning method reported here is a single tube and programmed reaction cloning with restriction enzymes. Compared to other cloning methods, Pyrite cloning is flexible, inexpensive, simple, and highly efficient.

Effective mucosal live attenuated Salmonella vaccine by deleting phosphotransferase system component genes ptsI and crr.

Salmonella enterica is a major human pathogen that causes invasive non-typhoidal Salmonellosis (iNTS), resulting in significant morbidity and mortality. Although a number of pre-clinical and clinical studies have reported on the feasibility of developing a safe and effective vaccine against iNTS, there have been no licensed Salmonella vaccines available to protect against NTS strains. Vaccine formulations of highest priority for NTS are live attenuated vaccines, which can elicit effective induction of intestinal mucosal and intracellular bacteria-specific cell mediated immune responses. Since glucose is crucial for intracellular survival and replication in host cells, we constructed strains with mutations in components of the glucose uptake system, called the phosphotransferase system (PTS), and compared the relative virulence and immune responses in mice. In this study, we found that the strain with mutations in both ptsI and crr (KST0556) was the most attenuated strain among the tested strains, and proved to be highly effective in inducing a mucosal immune response that can protect against NTS infections in mice. Thus, we suggest here that KST0556 (ΔptsIΔcrr) is a potential live vaccine candidate for NTS, and may also be a candidate for a live delivery vector for heterologous antigens. Moreover, since PTS is a well-conserved glucose transporter system in both Gramnegative and Gram-positive bacteria, the ptsI and crr genes may be potential targets for creating live bacterial vectors or vaccine strains.

Cancer Immunotherapy: Priming the Host Immune Response with Live Attenuated Salmonella enterica.

In recent years, cancer immunotherapy has undergone great advances because of our understanding of the immune response and the mechanisms through which tumor cells evade it. A century after the first immunotherapy attempt based on bacterial products described by William Coley, the use of live attenuated bacterial vectors has become a promising alternative in the fight against cancer. This review describes the role of live attenuated Salmonella enterica as an oncolytic and immunotherapeutic agent, due to its high affinity for tumor tissue and its ability to activate innate and adaptive antitumor immune response. Furthermore, its potential use as delivery system of tumor antigens and immunomodulatory molecules that induce tumor regression is also reviewed.

Abstract LB-149: Targeting shared hotspot cancer mutations with a Listeria monocytogenes immunotherapy induce potent anti-tumor immunity

Abstract Introduction: Virtually all tumors contain somatic mutations that can result in novel antigenic sequences that may be targeted by the host cellular immune response. Some of these mutations occur in preferential regions of specific genes commonly referred to as hotspot mutations. Hotspot mutations are commonly shared by cancer patients both within and across multiple tumor types. These hotspot mutations often confer loss or gain of function contributing to oncogenesis, which makes them promising therapeutic targets. One such mutation commonly found in several human tumor types is an aspartic acid substitution for glycine at position 12 (G12D) in KRAS. This same mutation occurs in the CT26 murine colorectal tumor model. To determine if expression of the KRAS G12D sequence in a bacterial immunotherapy vector can control tumor growth in the CT26 murine model, the Advaxis Listeria monocytogenes (Lm)-based platform was engineered to express a 21-amino acid KRAS sequence peptide containing the G12D mutation (Lm-Hot KRAS_G12D). In addition, we evaluated control of tumor growth using an ADXS-HOT construct (ADXS-503) that expresses multiple shared human hotspot and tumor-associated antigens, including the G12D KRAS. The ADXS-HOT clinical program is comprised of several Lm-based immunotherapies designed to target multiple shared hotspot and tumor-associated antigens commonly found in specific cancer types. In this study, we demonstrate control of tumor growth in a mouse model by targeting a commonly shared hotspot mutation using an Lm-based immunotherapy. Results: We show that the Lm-HOT KRAS_G12D therapy significantly delayed tumor growth and improved long-term survival in the murine CT26 colon carcinoma model. This response was associated with an increase in the frequency of tumor infiltrating antigen-specific CD8 T cells and γδ T cells within the tumor microenvironment and a decrease in the frequency of intratumoral regulatory T cells (Tregs). Furthermore, tumor-specific CD8 T cells displayed lower expression of exhaustion markers as well as increased functionality upon restimulation. Interestingly, our proprietary ADXS-503 (a clinical ADXS-HOT construct) which includes KRAS G12D as one of its multiple targets, was also capable of significantly suppressing tumor growth in the CT26 tumor model. Conclusion: These results suggest that our ADXS-HOT platform is a promising approach to target shared hotspot mutations. That ADXS Lm constructs targeting a single hotspot mutation can significantly control tumor growth whether it is in a single or multi-target construct. These data describe an exciting translatable discovery with the potential for broad utility across multiple tumor types and patients who share common hotspot mutations. Citation Format: Daniel Villarreal, Brandon Coder, Susan Armington, Andrew L'Huillier, Cristina Mottershead, Elena Filippova, Nithya Thambi, Kim Ramos, David Balli, Robert Petit, Michael Princiotta. Targeting shared hotspot cancer mutations with a Listeria monocytogenes immunotherapy induce potent anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-149.

Abstract LB-150: Neoantigens that fail to elicit measurable T cell responses following peptide immunization can control tumor growth when delivered using a Listeria-based immunotherapy platform

Abstract Introduction: Recent advances in the field of cancer immunotherapy have identified CD8+ T cell responses against tumor-specific neoantigens as a key driver of tumor regression and prolonged survival. ADXS-NEO is a personalized Listeria monocytogenes (Lm)-based immunotherapy designed to generate immune responses against mutation-derived tumor-specific neoantigens. Advaxis' Lm-based immunotherapies consist of live highly-attenuated bacterial vectors that are bioengineered to secrete a fusion protein consisting of a truncated non-hemolytic fragment of listeriolysin O, which has adjuvant properties, and tumor-specific neoantigens that harbor nonsynonymous point mutations (NSMs). The objective of this study is to demonstrate the feasibility of using the ADXS-NEO platform to target tumor-specific point mutations to generate neoantigen-specific T cells and control tumor growth. Results: Whole-exome sequencing of the MC38 mouse tumor cell line identified 2870 unique NSMs. Among these, the IC50 of 138 NSMs were predicted to be less than 500 nM by the netMHCcons algorithm. We evaluated the immunogenicity of 37 NSMs, and found that 12 immunogenic NSMs elicited a CD8+ T cell response following peptide immunization. Moreover, we identified 10 additional immunogenic NSMs in MC38-bearing mice treated with a check point inhibitor. Altogether, we identified 22 immunogenic and 23 non-immunogenic NSMs. Two ADXS-NEO vectors were constructed, Lm-19 & Lm-20, targeting 19 non-immunogenic and 20 immunogenic NSMs respectively. The ability of Lm-19 and Lm-20 to control MC38 tumor growth was evaluated in C57BL/6J mice. We found that both Lm-19 & Lm-20 led to an accumulation of neoantigen-specific CD8+ TILs and significantly slowed tumor growth. Moreover, both Lm-19 and Lm-20 decreased the frequency and absolute number of intratumoral Tregs, TAMs, and MDSCs and increased the frequency and absolute number of effector CD8+ T cells. Interestingly, expression of PD-L1 was decreased in TAMs and MDSCs and the frequency and total number of granzyme A+ CD8+ effector T cells was increased. Furthermore, the proportion of phenotypically exhausted PD-1hiLAG3+ TILs was decreased. Together, these data suggest the tumor microenvironment in mice receiving Lm-19 and Lm-20 becomes more cytotoxic and less suppressive. Conclusion: ADXS-NEO is a potent immunotherapy capable of driving immune responses against tumor-specific mutations and leading to tumor control. The effectiveness of the Lm platform is demonstrated by the generation of neoantigen-specific T cells to peptide sequences that were identified as “non-immunogenic” using a conventional peptide-adjuvant immunization. This study is a clear demonstration that T cell mediated anti-tumor responses can be generated by targeting tumor-derived NSMs with the ADXS-NEO Listeria monocytogenes vector. Citation Format: Brandon Coder, Hyewon Phee, Cristina Mottershead, Dipti Kelkar, Elena Filippova, Xiaoming Ju, Bryan Vander Lugt, Olga Pryshchep, Justin Lesch, Xian Liu, Jason DeVoss, Keegan Cooke, Claret Liu, Jinghui Zhan, Petia Mitchell, Kim Ramos, Daniel O. Villarreal, Jim Johnston, Robert Petit, Michael Princiotta. Neoantigens that fail to elicit measurable T cell responses following peptide immunization can control tumor growth when delivered using a Listeria-based immunotherapy platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-150.

Abstract LB-148: Targeting frameshift mutations with a Listeria monocytogenes immunotherapy drives neoantigen-specific antitumor immunity in the MC38 and CT26 mouse tumor models

Abstract Introduction: Neoantigens derived from tumor-specific mutations have been shown to drive tumor specific CD8+ T cell responses leading to tumor regression and extending overall survival. Frameshift mutations are estimated to generate up to nine times more neoantigens per mutation compared to in-frame mutations. However, it is not clear if vaccination against frameshift mutations induces neoantigen-specific CD8+ T cell responses that result in control of tumor growth. ADXS-NEO is a personalized Listeria monocytogenes (Lm)-based immunotherapy designed to target mutation-derived tumor-specific neoantigens. Advaxis' Lm-based immunotherapies consist of live attenuated bacterial vectors that are bioengineered to secrete an antigen-adjuvant fusion protein consisting of a truncated non-hemolytic fragment of listeriolysin O, which has adjuvant properties, and tumor-specific antigens. Here, we demonstrate the feasibility of using the ADXS-NEO platform to target tumor-specific frameshift mutations in order to generate neoantigen-specific T cells that control tumor growth. Results: Whole-exome sequencing of the CT26 and MC38 mouse tumor cell lines identified 30 and 31 unique frameshift mutations respectively. Individual frameshift mutations ranged in size from 12 to as many as 150 amino acids (aa). Lm vectors targeting the two longest frameshift mutations were constructed for each tumor model. The therapeutic efficacy of Lm vectors expressing either a single 57 aa (Lm-57) or a single 150 aa (Lm-150) MC38 frameshift mutation were evaluated in C57BL/6J mice. Both Lm vectors generated multiple unique frameshift-specific TILs and slowed tumor growth. Furthermore, we evaluated the tumor microenvironment following Lm-57 or Lm-150 treatment and observed a decrease in the frequency and absolute number of Tregs, TAMs, and MDSCs and an increase in the frequency and absolute number of total cytotoxic granzyme A+ effector CD8+ T cells. Similarly, Lm vectors expressing either a 64 aa (Lm-64) or a 93 aa (Lm-93) CT26 frameshift mutation were evaluated in the CT26 tumor model. Both Lm-64 and Lm-93 significantly controlled tumor growth. Additionally, an influx of neoantigen-specific TILs and a significant decrease in the frequency of intratumoral Tregs was observed. Conclusion: ADXS-NEO induced potent immune responses against tumor-specific frameshift mutations and controlled tumor growth. Advaxis' Lm platform is able to target frameshift mutations ≥150 aa and generate multiple neoantigen-specific T cells per frameshift. ADXS-NEO controls tumor growth via multiple mechanisms, including the generation of tumor-specific cytotoxic TILs, by secreting tumor-derived neoantigens directly into dendritic cells and by attenuating the suppressive tumor microenvironment. Citation Format: Brandon Coder, Daniel O. Villarreal, Susan Armington, Elena Filippova, Andrew L'Huillier, Dipti Kelkar, Xiaoming Ju, Cristina Mottershead, David Balli, Kim Ramos, Hyewon Phee, Jim Johnston, Robert Petit, Michael Princiotta. Targeting frameshift mutations with a Listeria monocytogenes immunotherapy drives neoantigen-specific antitumor immunity in the MC38 and CT26 mouse tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-148.

Conserved cysteines in Mason–Pfizer monkey virus capsid protein are essential for infectious mature particle formation

Retrovirus assembly is driven mostly by Gag polyprotein oligomerization, which is mediated by inter and intra protein–protein interactions among its capsid (CA) domains. Mason-Pfizer monkey virus (M-PMV) CA contains three cysteines (C82, C193 and C213), where the latter two are highly conserved among most retroviruses. To determine the importance of these cysteines, we introduced mutations of these residues in both bacterial and proviral vectors and studied their impact on the M-PMV life cycle. These studies revealed that the presence of both conserved cysteines of M-PMV CA is necessary for both proper assembly and virus infectivity. Our findings suggest a crucial role of these cysteines in the formation of infectious mature particles.

Nanowire Arrays as Force Sensors with Super‐Resolved Localization Position Detection: Application to Optical Measurement of Bacterial Adhesion Forces

AbstractThe design and application of indium phosphide (InP) nanowire arrays to acquire Xylella fastidiosa bacterial cell vector force maps are discussed. The nanowire deflections are measured with subdiffraction localization confocal laser scanning microscopy (CLSM). The nanowire mechanical stability in air and liquid media as well as methods to average out thermally induced oscillations are investigated. The accuracy of center determination of the CLSM reflected laser intensity profile at nanowire apex is studied using Gaussian fitting and localization microscopy techniques. These results show that the method is reliable for measuring nanowire displacements above ≈25 nm. Corresponding force ranges probed by this method can be customized depending on nanowire geometry and array configuration. The method is applied to explore X. fastidiosa cell adhesion forces on the InP nanowire surface, and in situ probes the effect of N‐acetylcysteine on adhered cells. Future perspectives for application of this method in microbiology studies are also outlined.

An Effective Recombinant Protein Expression and Purification System in Saccharomyces cerevisiae.

The expression and purification of recombinant proteins using bacterial vectors is a mature and preferred system to obtain folded and stable proteins. However, functional post-translational protein modifications, such as glycosylation or phosphorylation, can only be achieved using eukaryotic expression systems. In addition, insolubility is another challenge when using proteins expressed in Escherichia coli, such as certain intrinsically disordered proteins, which are more prone to aggregation than folded proteins. Eukaryotic protein expression systems, including human cells, baculovirus/insect cells, and yeast, have become indispensable for the production of functional eukaryotic proteins. This article describes a detailed protocol for performing cytosolic protein expression, protein purification, and protein characterization using the budding yeast Saccharomyces cerevisiae. The introduced protein expression and purification system in yeast are advantageous due to the low cost, high yield, high protein solubility, and minimal expertise required. © 2018 by John Wiley & Sons, Inc.

Live Attenuated Tularemia Vaccines for Protection Against Respiratory Challenge With Virulent F. tularensis subsp. tularensis.

Francisella tularensis is the causative agent of tularemia and a Tier I bioterrorism agent. In the 1900s, several vaccines were developed against tularemia including the killed “Foshay” vaccine, subunit vaccines comprising F. tularensis protein(s) or lipoproteins(s) in an adjuvant formulation, and the F. tularensis Live Vaccine Strain (LVS); none were licensed in the U.S.A. or European Union. The LVS vaccine retains toxicity in humans and animals—especially mice—but has demonstrated efficacy in humans, and thus serves as the current gold standard for vaccine efficacy studies. The U.S.A. 2001 anthrax bioterrorism attack spawned renewed interest in vaccines against potential biowarfare agents including F. tularensis. Since live attenuated—but not killed or subunit—vaccines have shown promising efficacy and since vaccine efficacy against respiratory challenge with less virulent subspecies holarctica or F. novicida, or against non-respiratory challenge with virulent subsp. tularensis (Type A) does not reliably predict vaccine efficacy against respiratory challenge with virulent subsp. tularensis, the route of transmission and species of greatest concern in a bioterrorist attack, in this review, we focus on live attenuated tularemia vaccine candidates tested against respiratory challenge with virulent Type A strains, including homologous vaccines derived from mutants of subsp. holarctica, F. novicida, and subsp. tularensis, and heterologous vaccines developed using viral or bacterial vectors to express F. tularensis immunoprotective antigens. We compare the virulence and efficacy of these vaccine candidates with that of LVS and discuss factors that can significantly impact the development and evaluation of live attenuated tularemia vaccines. Several vaccines meet what we would consider the minimum criteria for vaccines to go forward into clinical development—safety greater than LVS and efficacy at least as great as LVS, and of these, several meet the higher standard of having efficacy ≥LVS in the demanding mouse model of tularemia. These latter include LVS with deletions in purMCD, sodBFt, capB or wzy; LVS ΔcapB that also overexpresses Type VI Secretion System (T6SS) proteins; FSC200 with a deletion in clpB; the single deletional purMCD mutant of F. tularensis SCHU S4, and a heterologous prime-boost vaccine comprising LVS ΔcapB and Listeria monocytogenes expressing T6SS proteins.

Development of an Effective Cancer Vaccine Platform Using Attenuated Salmonella typhi

Abstract Poor antigen delivery is one of the major limitations of modern cancer vaccine vectors. To overcome this challenge, we exploited Salmonella Pathogenicity Island 2 and type III secretion system to deliver tumor-associated antigen (TAAs) into the cytosol of antigen-presenting cells in situ. In a recent report, we demonstrated that an attenuated strain of S. typhimurium, which was engineered to express SPI2-regulated oncoprotein survivin (SVN), induced potent CD8 T-cell-mediated antitumor response that was curative in a murine model of highly aggressive lymphoma. In further development of this technology for clinical use, the vaccine has been transferred from an experimental strain to a clinically validated strain of S. typhi, CVD908. To adapt CVD908 to stably express recombinant antigens without antibiotic-dependent selection, we used a recently reported plasmid stabilization system that encodes the single-stranded binding protein (SSB), an essential protein in DNA metabolism, which was deleted from the bacterial chromosome. The SPI2-regulated expression cassette was then cloned into the SSB plasmid, so that the resultant construct maintained bacterial vector stability while expressing and translocating TAAs. We found that CVD908Δssb vector effectively infects human dendritic cells in vitro and translocates recombinant SVN and MYCN oncoproteins into their cytosol. Furthermore, CVD908Δssb remains stable in mice and induces generation of antigen-specific CD8 T cells. Therapeutic vaccination of tumor-bearing mice with SVN or MYCN vaccine produced potent antitumor activity in murine models of lymphoma or neuroblastoma. The results justify clinical testing of CVD908Δssb-based SVN and MYCN vaccines in cancer patients.

Live Bacterial Vectors-A Promising DNA Vaccine Delivery System.

Vaccination is one of the most successful immunology applications that has considerably improved human health. The DNA vaccine is a new vaccine being developed since the early 1990s. Although the DNA vaccine is promising, no human DNA vaccine has been approved to date. The main problem facing DNA vaccine efficacy is the lack of a DNA vaccine delivery system. Several studies explored this limitation. One of the best DNA vaccine delivery systems uses a live bacterial vector as the carrier. The live bacterial vector induces a robust immune response due to its natural characteristics that are recognized by the immune system. Moreover, the route of administration used by the live bacterial vector is through the mucosal route that beneficially induces both mucosal and systemic immune responses. The mucosal route is not invasive, making the vaccine easy to administer, increasing the patient’s acceptance. Lactic acid bacterium is one of the most promising bacteria used as a live bacterial vector. However, some other attenuated pathogenic bacteria, such as Salmonella spp. and Shigella spp., have been used as DNA vaccine carriers. Numerous studies showed that live bacterial vectors are a promising candidate to deliver DNA vaccines.

Safety implication of Salmonella based Brucella vaccine candidate in mice and in vitro human cell culture

An anti-Brucella vaccine candidate comprising rough Salmonella vector delivering Brucella antigens was developed. This system provides a platform for live Brucella-free vaccine development as it can mimic active-intracellular infection of Brucella organism. Exploiting this phenomenon thus provides significant protection at a single dose and also re-assured the safety. To date, no human anti-Brucella vaccines are available, owing to the lack of safe and effective formulation. This study investigated the safety of the vaccine formulation in mice model and in vitro human cell cultures. The experiment was designed to determine the LD50 of the vaccine formulation. The vaccine formulation did not induce any mortality even when mice were administered at 8 × 109 CFU per oral or per subcutaneous (SC), which was 100-times more than the actual vaccine dose intended for mice model. In contrast, wild-type (WT) Salmonella positive control strain induced 100% mortality at 8 × 107 CFU per mice via oral or SC routes. Interaction of the vaccine with phagocytic (THP-1 derived macrophage) and non-phagocytic (Caco-2) human cell lines as well as human PBMC was investigated. In in vitro experiments, inflammatory and pyretic cytokines TNF-α, and IL-1β inductions were significantly lower in vaccine group as compared to WT group. Further, apoptosis, nitric oxide synthase and cytotoxicity inductions were comparable and not exacerbated, given that the strain is based on a rough bacterial vector that may have endotoxic lipid-A more readily exposed. These findings corroborated that the vaccine formulation is highly safe in mice model and is relatively mild in the induction of inflammatory cytokines and cellular changes in human cell lines.

Persistence of plasmid-mediated expression of transgenes in human mesenchymal stem cells depends primarily on CpG levels of both vector and transgene.

Gene therapy and cell modification for clinical applications using plasmid vectors are considered to be a safe and promising strategy. One of the major problems with plasmid vector-based constructs is a rapid decline of transgene expression in cells in vitro and in vivo. An important role of CpG motifs or bacterial vector backbone in expression silencing has been suggested. To address the effects of CpG motifs on transgene expression maintenance in stem cells in vitro, we constructed a novel pMBR2 plasmid vector containing 13 CpG motifs only. pMBR2 constructs with CpG-free and CpG-replete firefly luciferase inserts were introduced into cultured human adipose-derived mesenchymal stem (MSCs) by electroporation, and luciferase expression levels were monitored for 3weeks. The pMBR2 vector with CpG-free luciferase insert demonstrated the highest persistence of expression, whereas the wild-type luciferase insert containing 97 CpG motifs demonstrated lower expression maintenance in the same vector. In comparison, the same inserts in the CpG-replete pCDNA3 vector demonstrated significantly lower expression levels and only a minimal persistence of expression. β-galactosidase and enhanced green fluorescent protein genes inserted into pMBR2 vector also demonstrated higher expression levels and better maintenance compared to the same genes in pCDNA3 vector. The persistence of plasmid vector expression in human MSCs is determined primarily by CpG content of both vector and transgene. The data obtained in the present study indicate that the pMBR2 vector with a minimized number of CpG motifs is appropriate for extended plasmid-mediated expression of transgenes in MSCs and possibly other types of stem cells.

A novel food‐grade lactococcal expression system and its use for secretion and delivery of an oral vaccine antigen

AbstractBACKGROUNDFood‐grade bacterial expression systems are relatively rare, and increasing evidence indicates that subcellular location of antigens in bacterial vector vaccines may markedly affect the immune efficacy.RESULTSThis study developed a novel food‐grade secretory expression system for heterologous protein production and oral vaccine delivery. Furthermore, by using the expression system, an engineered L. lactis strain secreting H. pylori UreB was constructed, and used to vaccinate SPF BALB/c mice. As results, the UreB expressed in L. lactis was detected in both cell lysates and culture supernatant of the engineered strain, constituting roughly 50% of the culture supernatant proteins, and recognized by mouse anti‐H. pylori sera. Oral vaccination with the engineered L. lactis produced a significantly elevated anti‐UreB serum antibody level in mice (P < 0.05).CONCLUSIONThese data show a novel food‐grade L. lactis secretory expression system, which may have distinct potential impact on edible and medicinal protein production and oral vaccine development. Moreover, this is the first report on secretory expression of a H. pylori antigen via using a food‐grade lactococcal expression system, and the engineered strain secreting UreB can be a hopeful H. pylori vaccine candidate. © 2017 Society of Chemical Industry

Ectopic Expression of O Antigen in Bordetella pertussis by a Novel Genomic Integration System.

We describe a novel genome integration system that enables the introduction of DNA fragments as large as 50kbp into the chromosomes of recipient bacteria. This system, named BPI, comprises a bacterial artificial chromosome vector and phage-derived gene integration machinery. We introduced the wbm locus of Bordetella bronchiseptica, which is required for O antigen biosynthesis, into the chromosome of B.pertussis, which intrinsically lacks O antigen, using the BPI system. After the introduction of the wbm locus, B.pertussis presented an additional substance in the lipooligosaccharide fraction that was specifically recognized by the anti-B.bronchiseptica antibody but not the anti-B. pertussis antibody, indicating that B. pertussis expressed O antigen corresponding to that of B.bronchiseptica. O antigen-expressing B. pertussis was less sensitive to the bactericidal effects of serum and polymyxin B than the isogenic parental strain. In addition, an in vivo competitive infection assay showed that O antigen-expressing B.pertussis dominantly colonized the mouse respiratory tract over the parental strain. These results indicate that the BPI system provides a means to alter the phenotypes of bacteria by introducing large exogenous DNA fragments. IMPORTANCE Some bacterial phenotypes emerge through the cooperative functions of a number of genes residing within a large genetic locus. To transfer the phenotype of one bacterium to another, a means to introduce the large genetic locus into the recipient bacterium is needed. Therefore, we developed a novel system by combining the advantages of a bacterial artificial chromosome vector and phage-derived gene integration machinery. In this study, we succeeded for the first time in introducing a gene locus involved in O antigen biosynthesis of Bordetella bronchiseptica into the chromosome of B.pertussis, which intrinsically lacks O antigen, and using this system we analyzed phenotypic alterations in the resultant mutant strain of B.pertussis. The present results demonstrate that this system successfully accomplished the above-described purpose. We consider this system to be applicable to a number of bacteria other than Bordetella.

Engineered Salmonella enterica serovar Typhimurium overcomes limitations of anti-bacterial immunity in bacteria-mediated tumor therapy

ABSTRACT Cancer is one of the leading causes of death in the industrialized world and represents a tremendous social and economic burden. As conventional therapies fail to provide a sustainable cure for most cancer patients, the emerging unique immune therapeutic approach of bacteria-mediated tumor therapy (BMTT) is marching towards a feasible solution. Although promising results have been obtained with BMTT using various preclinical tumor models, for advancement a major concern is immunity against the bacterial vector itself. Pre-exposure to the therapeutic agent under field conditions is a reasonable expectation and may limit the therapeutic efficacy of BMTT. In the present study, we investigated the therapeutic potential of Salmonella and E. coli vector strains in naïve and immunized tumor bearing mice. Pre-exposure to the therapeutic agent caused a significant aberrant phenotype of the microenvironment of colonized tumors and limited the in vivo efficacy of established BMTT vector strains Salmonella SL7207 and E. coli Symbioflor-2. Using targeted genetic engineering, we generated the optimized auxotrophic Salmonella vector strain SF200 (ΔlpxR9 ΔpagL7 ΔpagP8 ΔaroA ΔydiV ΔfliF) harboring modifications in Lipid A and flagella synthesis. This combination of mutations resulted in an increased immune-stimulatory capacity and as such the strain was able to overcome the efficacy-limiting effects of pre-exposure. Thus, we conclude that any limitations of BMTT concerning anti-bacterial immunity may be countered by strategies that optimize the immune-stimulatory capacity of the attenuated vector strains.

Abstract 1477: Melatonin regulates the tumor suppressor miR-148a-3p involved in angiogenesis and metastasis of breast cancer

Abstract Women with breast cancer has the tumor progression and angiogenesis-induced metastasis as the main cause of death. MicroRNAs (miRNAs) are small noncoding mRNA molecules that play an important role in gene regulation and once deregulated, these molecules may be involved with the progression of different human tumor types, including breast cancer. These miRNAs play an oncostatic role on tumor suppressor genes and regulate the process of angiogenesis, tumor growth and metastasis. So as new possible adjuvant treatment against breast cancer our group have shown melatonin, that is a hormone secreted by the pineal gland, by exhibiting several anti-tumor and antiangiogenic effects. Therefore, the aim of this study was to evaluate the potential therapeutic of melatonin on miRNAs regulation to verify breast cancer progression and potent tumor suppressor miR-148a-3p. In silico analysis was performed for selection of miRNAs involved in breast cancer. The MDA-MB-231 breast cancer cell line (metastatic negative estrogen receptor) was grown and separated in two different experimental conditions maintained for 24 hours: control group and melatonin-treated group (concentration of 1 mM). After this period the extraction of total RNA was performed (Qiagen®) and the total concentration of miRNAs of each sample was determined (NanoDrop Spectrophotometer 2000C - Thermo Scientific®). Differential expressions of these miRNAs was evaluate using miScript miRNA PCR-Array (Qiagen®) containing 84 miRNAs associated with breast cancer. The overexpression of miR-148a-3p in MDA-MB-231 cells was performed by bacterial cloning vector and the relative quantification of gene expression of their target IGF-1R and VEGF by real-time PCR. Moreover, the quantification of protein expression was performed by immunocytochemistry of IGF-1R and VEGF. Lastly, the migration and invasion cell assays were carried out to assess the potential capacity of these cells to undergo metastasis. The analysis of miRNAs MDA-MB-231 cell line by PCR-array showed 24 upregulated miRNAs and 8 miRNAs downregulated after the treatment with melatonin. Relative quantification shows that the melatonin treatment increases the gene expression of miR-148a-3p and decreases the gene and protein levels of IGF-1R and VEGF. The capability of migration and invasion of the breast cancer cells decreased after treatment with melatonin and overexpression of miR-148a-3p. Our results confirm the action of melatonin on the miR-148a-3p regulation known being involved in the progression of breast cancer. Thus the establishment of this therapeutic protocols can control these cellular events essential for the prognosis of patients with breast cancer. Citation Format: Debora Zuccari, Jéssica Zani Lacerda, Lívia Carvalho Ferreira, Beatriz Camargo Lopes, Andrés Felipe Aristizábal-Pachón, Marcio Chaim Bajgelman. Melatonin regulates the tumor suppressor miR-148a-3p involved in angiogenesis and metastasis of breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1477. doi:10.1158/1538-7445.AM2017-1477

Live-attenuated auxotrophic mutant of Salmonella Typhimurium expressing immunogenic HA1 protein enhances immunity and protective efficacy against H1N1 influenza virus infection.

To evaluate the efficacy of attenuated Salmonella Typhimurium (JOL912) as a live bacterial vaccine vector. The JOL912 engineered to deliver HA1 protein from influenza A/Puerto Rico/8/1934 (H1N1; PR8) virus was coined as JOL1635 and further evaluated for immunogenicity and protective efficacy. The JOL1635 stably harbored the HA1 gene within pMMP65 plasmid with periplasmic expression and effective delivery of HA1 protein to RAW264.7 cells. The JOL1635 immunized chickens showed the significant increase in HA1-specific IgG, sIgA antibody, IFN-γ, IL-6 cytokine and cellular immune responses. The postoral challenge, the JOL1635-immunized chickens showed a faster clearance of PR8 virus cloacal shedding than the control group. Generated JOL1635 can establish specific immunogenicity and protection against the PR8 virus in chickens.

Vaccine self-assembling immune matrix is a non-viral delivery platform that improves overall vaccine performance while maintaining safety and stability

Abstract Vaccination remains the most effective public health tool to prevent infectious disease. Many vaccines are marginally effective, and are less so when administered to immune-compromised populations. To enhance vaccine immunogenicity, we exploited the biphasic property of the (RADA)4 synthetic oligopeptide to create a new vaccine delivery method, VacSIM® (vaccine self-assembling immune matrix). Vaccine components are mixed with the VacSIM® solution for injection, after which the (RADA)4 peptides self-assemble into hydrated nanofiber gel-matrices, forming a vaccine depot with the vaccine antigens in the aqueous phase, allowing for slow-release of vaccine components over time. Thus, we have a non-viral, inert, biodegradable delivery system, not requiring formulation that can deliver various types of vaccines. We hypothesize that slow-release of vaccine components provides antigen persistence, driving enhanced vaccine-specific responses that are improved in both quantity and quality. We have tested VacSIM® with live bacterial vectors, inactivated virus and multiple recombinant protein vaccines. VacSIM® delivery of different protein immunogens, including Hepatitis B and HIV Envelope, is superior to delivery in licensed and unlicensed adjuvants and requires only a single injection. VacSIM® improves existing vaccines by reducing the number of injections needed, improving vaccine performance, especially in difficult-to-protect populations like the elderly and immune compromised, and reducing unwelcome side effects. VacSIM® can be stockpiled and stored without a cold chain, which is especially beneficial in resource-limited settings where vaccine access and compliance are issues.