Targeting diseases with genetically engineeredLactococcus lactisand its course towards medical translation

Haemagglutinin displayed on the surface of Lactococcus lactis confers broad cross-clade protection against different H5N1 viruses in chickens

Background

The highly pathogenic avian influenza (HPAI) H5N1 virus poses a potential threat to the poultry industry. The currently available avian influenza H5N1 vaccines for poultry are clade-specific. Therefore, an effective vaccine for preventing and controlling H5N1 viruses belonging to different clades needs to be developed.

Results

Recombinant L. lactis/pNZ8148-Spax-HA was generated, and the influenza virus haemagglutinin (HA) protein of A/Vietnam/1203/2004 (H5N1) was displayed on the surface of Lactococcus lactis (L. lactis). Spax was used as an anchor protein. Chickens vaccinated orally with unadjuvanted L. lactis/pNZ8148-Spax-HA could produce significant humoral and mucosal responses and neutralizing activities against H5N1 viruses belonging to different clades. Importantly, unadjuvanted L. lactis/pNZ8148-Spax-HA conferred cross-clade protection against lethal challenge with different H5N1 viruses in the chicken model.

Conclusion

This study provides insights into the cross-clade protection conferred by unadjuvanted L. lactis/pNZ8148-Spax-HA, and the results might help the establishment of a promising platform for the development of a safe and effective H5N1 cross-clade vaccine for poultry.

Lactococcus lactis expressing sand fly PpSP15 salivary protein confers long-term protection against Leishmania major in BALB/c mice

Cutaneous leishmaniasisis a vector-borne disease transmitted by Leishmania infected sand flies. PpSP15 is an immunogenic salivary protein from the sand fly Phlebotomus papatasi. Immunization with PpSP15 was shown to protect against Leishmania major infection. Lactococcus lactis is a safe non-pathogenic delivery system that can be used to express antigens in situ. Here, the codon-optimized Ppsp15-egfp gene was cloned in pNZ8121 vector downstream of the PrtP signal peptide that is responsible for expression and secretion of the protein on the cell wall. Expression of PpSP15-EGFP recombinant protein was monitored by immunofluorescence, flow cytometry and Western blot. Also, expression of protein in cell wall compartment was verified using whole cell ELISA, Western blot and TEM microscopy. BALB/c mice were immunized three times with recombinant L. lactis-PpSP15-EGFPcwa, and the immune responses were followed up, at short-term (ST, 2 weeks) and long-term (LT, 6 months) periods. BALB/c mice were challenged with L. major plus P. papatasi Salivary Gland Homogenate. Evaluation of footpad thickness and parasite burden showed a delay in the development of the disease and significantly decreased parasite numbers in PpSP15 vaccinated animals as compared to control group. In addition, immunized mice showed Th1 type immune responses. Importantly, immunization with L. lactis-PpSP15-EGFPcwa stimulated the long-term memory in mice which lasted for at least 6 months.

Enhanced gastrointestinal survivability of recombinant Lactococcus lactis using a double coated mucoadhesive film approach

Vaccine administration via the oral route is preferable to parenteral routes due to ease of administration. To date, most available oral vaccines comprises of live attenuated pathogens as oppose to peptide-based vaccines due to its low bioavailability within the gastrointestinal (GI) tract. Over the years, probiotic-based peptide delivery vehicles comprising of lactic acid bacteria such as Lactococcus lactis has emerged as an interesting alternative due to its generally recognized as safe (GRAS) status, a fully sequenced genome, transient gut colonization time, and is an efficient cellular factory for heterologous protein production. However, its survivability through the GI tract is low, thus better delivery approaches are being explored to improve its bioavailability. In this study, we employ the incorporation of a double coated mucoadhesive film consisting of sodium alginate and Lycoat RS 720 film as the inner coat. The formulated film exhibits good mechanical properties of tensile strength and percent elongation for manipulation and handling with an entrapment yield of 93.14±2.74%. The formulated mucoadhesive film is subsequently loaded into gelatin capsules with an outer enteric Eudragit L100-55 coating capable of a pH-dependent breakdown above pH 5.5 to protect against gastric digestion. The final product and unprotected controls were subjected to in vitro simulated gastrointestinal digestions to assess its survivability. The product demonstrated enhanced protection with an increase of 69.22±0.67% (gastric) and 40.61±8.23% (intestinal) survivability compared to unprotected controls after 6 hours of sequential digestion. This translates to a 3.5 fold increase in overall survivability. Owing to this, the proposed oral delivery system has shown promising potential as a live gastrointestinal vaccine delivery host. Further studies involving in vivo gastrointestinal survivability and mice immunization tests are currently being carried out to assess the efficacy of this novel oral delivery system in comparison to parenteral routes.

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

The ORFs of both native and codon-optimized E7 genes were successfully fused to SPusp45 signal peptide and expressed by a nisin-controlled gene expression system in the NZ9000 strains of Lactococcus lactis. Recombinant strains were confirmed by Western blot analysis. To measure immune responses against the E7 antigen, specific-pathogen-free C57BL/6 mice were inoculated with L lactis harboring pNZ8123-rE7 by oral gavage. Then, specific antibodies and cytokines were measured by enzyme-linked immunosorbent assay and enzyme-linked immunospot assay, respectively. Oral administration of L lactis strains expressing rE7 elicited the highest levels of E7-specific antibody and greatest numbers of E7-specific CD4⁺ T helper and CD8⁺ T cell precursors. Our outcomes indicated that the HPV-16 E7 specific IL-2- and IFN-γ-secreting T cells in antigen-stimulated splenocytes and intestinal mucosal lymphocytes were significantly higher than the control groups. Our data also demonstrated that mice vaccinated with recombinant L lactis were able to generate potent protective effects against challenge with the E7-expressing tumor cell line (TC-1). Moreover, L lactis containing pNZ8123-HPV16-optiE7 showed strong therapeutic antitumor effects against established tumors in vivo. These findings demonstrate that recombinant L lactis induce both humoral and cellular immune responses in mice and are therefore recommended for therapeutic treatments in humans after oral administration.

Protection against Foot-and-Mouth Disease Virus in Guinea Pigs via Oral Administration of Recombinant Lactobacillus plantarum Expressing VP1

Mucosal vaccination is an effective strategy for generating antigen-specific immune responses against mucosal infections of foot-and-mouth disease virus (FMDV). In this study, Lactobacillus plantarum strains NC8 and WCFS1 were used as oral delivery vehicles containing a pSIP411-VP1 recombinant plasmid to initiate mucosal and systemic immune responses in guinea pigs. Guinea pigs were orally vaccinated (three doses) with NC8-pSIP411, NC8-pSIP411-VP1, WCFS1-pSIP411, WCFS1-pSIP411-VP1 or milk. Animals immunized with NC8-pSIP411-VP1 and WCFS1-pSIP411-VP1 developed high levels of antigen-specific serum IgG, IgA, IgM, mucosal secretory IgA (sIgA) and neutralizing antibodies, and revealed stronger cell-mediated immune responses and enhanced protection against FMDV challenge compared with control groups. The recombinant pSIP411-VP1 effectively improved immunoprotection against FMDV in guinea pigs.

Production of biologically active scFv and VHH antibody fragments in Bifidobacterium longum

Bifidobacteria constitute a significant part of healthy intestinal microbiota in adults and infants and present a promising platform for construction of genetically modified probiotic agents for treatment of gastrointestinal disorders. In this study, three strains of Bifidobacterium longum were constructed that express and secrete biologically active single-chain antibodies against human TNF-α and Clostridium difficile exotoxin A. Anti-TNF-α scFv antibody D2E7 was produced at the level of 25 μg L(-1) in broth culture and was mostly retained in the cytoplasm, while VHH-type antibodies A20.1 and A26.8 against C. difficile exotoxin A were produced at the levels of 0.3-1 mg L(-1) and secreted very efficiently. The biological activity of both antibody types was demonstrated in the mammalian cell-based assays. Expression of A20.1 and A26.8 was also observed in vivo after intragastric administration of transformed B. longum strains to (C57/BL6 × DBA/2)F1 mice. The obtained B. longum strains may serve as prototypes for construction of novel probiotic medications against inflammatory bowel disease and C. difficile-associated disease.

Pushing the Bacterial Envelope

Over the past three decades, a powerful array of techniques has been developed for expressing heterologous proteins and saccharides on the surface of bacteria. Surface-engineered bacteria, in turn, have proven useful in a variety of settings, including high-throughput screening, biofuel production, and vaccinology. In this chapter, we provide a comprehensive review of methods for displaying polypeptides and sugars on the bacterial cell surface, and discuss the many innovative applications these methods have found to date. While already an important biotechnological tool, we believe bacterial surface display may be further improved through integration with emerging methodology in other fields, such as protein engineering and synthetic chemistry. Ultimately, we envision bacterial display becoming a multidisciplinary platform with the potential to transform basic and applied research in bacteriology, biotechnology, and biomedicine.

Biological delivery approaches for gene therapy: strategies to potentiate efficacy and enhance specificity

Nowadays many therapeutic agents such as suicide genes, anti-angiogenesis agents, cytokines, chemokines and other therapeutic genes were delivered to cancer cells. Various biological delivery systems have been applied for directing therapeutic gene to target cells. Some of these successful preclinical studies, steps forward to clinical trials and a few are examined in phase III clinical trials. In this review, the biological gene delivery systems were categorized into microorganism and cell based delivery systems. Viral, bacterial, yeast and parasite are among microorganism based delivery systems which are expanded in this review. In cell based approach, different strategies such as tumor cells, stem cells, dendritic cells and sertoli cells will be discussed. Different drawbacks are associated with each delivery system; therefore, many strategies have been improved and potentiated their direction toward specific target cells. Herein, further to the principle of each delivery system, the progresses of these approaches for development of newer generation are discussed.

Manipulation of innate immunity by a bacterial secreted peptide: lantibiotic nisin Z is selectively immunomodulatory

Innate immunity is triggered by a variety of bacterial molecules, resulting in both protective and potentially harmful pro-inflammatory responses. Further, innate immunity also provides a mechanism for the maintenance of homeostasis between the host immune system and symbiotic or non-pathogenic microorganisms. However, the bacterial factors that mediate these protective effects have been incompletely defined. Here, it was demonstrated that the lantiobiotic nisin Z is able to modulate host immune responses and mediate protective host immunity. Nisin Z induced the secretion of the chemokines MCP-1, IL-8 and Gro-α, and significantly reduced TNF-α induction in response to bacterial LPS in human PBMC. The results correlated with the ability of nisin Z to confer protection against both the Gram-positive organism Staphylococcus aureus, and the Gram-negatives Salmonella enterica sv. Typhimurium and Escherichia coli in murine challenge models. Mechanistic studies revealed that nisin Z modulates host immunity through similar mechanisms as natural host defense peptides, engaging multiple signal transduction pathways and growth factor receptors. The results presented herein demonstrate that, in addition to nisin Z, other bacterial cationic peptides and, in particular, the lantibiotics, could represent a new class of secreted bacterial molecule with immunomodulatory activities.

Immunization against Leishmania major infection using LACK- and IL-12-expressing Lactococcus lactis induces delay in footpad swelling

BACKGROUND

Leishmania is a mammalian parasite affecting over 12 million individuals worldwide. Current treatments are expensive, cause severe side effects, and emerging drug resistance has been reported. Vaccination is the most cost-effective means to control infectious disease but currently there is no vaccine available against Leishmaniasis. Lactococcus lactis is a non-pathogenic, non-colonizing Gram-positive lactic acid bacterium commonly used in the dairy industry. Recently, L. lactis was used to express biologically active molecules including vaccine antigens and cytokines.

METHODOLOGY/PRINCIPAL FINDINGS

We report the generation of L. lactis strains expressing the protective Leishmania antigen, LACK, in the cytoplasm, secreted or anchored to the bacterial cell wall. L. lactis was also engineered to secrete biologically active single chain mouse IL-12. Subcutaneous immunization with live L. lactis expressing LACK anchored to the cell wall and L. lactis secreting IL-12 significantly delayed footpad swelling in Leishmania major infected BALB/c mice. The delay in footpad swelling correlated with a significant reduction of parasite burden in immunized animals compared to control groups. Immunization with these two L. lactis strains induced antigen-specific multifunctional T(H)1 CD4(+) and CD8(+) T cells and a systemic LACK-specific T(H)1 immune response. Further, protection in immunized animals correlated with a Leishmania-specific T(H)1 immune response post-challenge. L. lactis secreting mouse IL-12 was essential for directing immune responses to LACK towards a protective T(H)1 response.

CONCLUSIONS/SIGNIFICANCE

This report demonstrates the use of L. lactis as a live vaccine against L. major infection in BALB/c mice. The strains generated in this study provide the basis for the development of an inexpensive and safe vaccine against the human parasite Leishmania.

Vaccines displaying mycobacterial proteins on biopolyester beads stimulate cellular immunity and induce protection against tuberculosis

New improved vaccines are needed for control of both bovine and human tuberculosis. Tuberculosis protein vaccines have advantages with regard to safety and ease of manufacture, but efficacy against tuberculosis has been difficult to achieve. Protective cellular immune responses can be preferentially induced when antigens are displayed on small particles. In this study, Escherichia coli and Lactococcus lactis were engineered to produce spherical polyhydroxybutyrate (PHB) inclusions which displayed a fusion protein of Mycobacterium tuberculosis, antigen 85A (Ag85A)-early secreted antigenic target 6-kDa protein (ESAT-6). L. lactis was chosen as a possible production host due its extensive use in the food industry and reduced risk of lipopolysaccharide contamination. Mice were vaccinated with PHB bead vaccines with or without displaying Ag85A-ESAT-6, recombinant Ag85A-ESAT-6, or M. bovis BCG. Separate groups of mice were used to measure immune responses and assess protection against an aerosol M. bovis challenge. Increased amounts of antigen-specific gamma interferon, interleukin-17A (IL-17A), IL-6, and tumor necrosis factor alpha were produced from splenocytes postvaccination, but no or minimal IL-4, IL-5, or IL-10 was produced, indicating Th1- and Th17-biased T cell responses. Decreased lung bacterial counts and less extensive foci of inflammation were observed in lungs of mice receiving BCG or PHB bead vaccines displaying Ag85A-ESAT-6 produced in either E. coli or L. lactis compared to those observed in the lungs of phosphate-buffered saline-treated control mice. No differences between those receiving wild-type PHB beads and those receiving recombinant Ag85A-ESAT-6 were observed. This versatile particulate vaccine delivery system incorporates a relatively simple production process using safe bacteria, and the results show that it is an effective delivery system for a tuberculosis protein vaccine.