Oral immunization with recombinant Lactococcus lactis confers protection against respiratory pneumococcal infection

In the present work, we evaluated if oral immunization with the pneumococcal protective protein A (PppA), expressed in the cell wall of Lactococcus lactis (L. lactis PppA+), was able to confer protective immunity against Streptococcus pneumoniae. Mice were immunized orally with L. lactis PppA+ for 5 consecutive days. Vaccination was performed one (nonboosted group) or 2 times with a 2 week interval between each immunization (boosted group). Oral priming with L. lactis PppA+ induced the production of anti-PppA IgM, IgG, and IgA antibodies in serum and in bronchoalveolar (BAL) and intestinal (IF) lavage fluids. Boosting with L. lactis PppA+ increased the levels of mucosal and systemic immunoglobulins. Moreover, the avidity and the opsonophagocytic activity of anti-PppA antibodies were significantly improved in the boosted group. The presence of both IgG1 and IgG2a anti-PppA antibodies in serum and BAL and the production of both interferon gamma and interleukin-4 by spleen cells from immunized mice indicated that L. lactis PppA+ stimulated a mixture of Th1 and Th2 responses. The ability of L. lactis PppA+ to confer cross-protective immunity was evaluated using challenge assays with serotypes 3, 6B, 14, and 23F. Lung bacterial cell counts and hemocultures showed that immunization with L. lactis PppA+ improved resistance against all the serotypes assessed, including serotype 3, which was highly virulent in our experimental animal model. To our knowledge, this is the first demonstration of protection against respiratory pneumococcal infection induced by oral administration of a recombinant lactococcal vaccine.     

Oral immunization of mice with Saccharomyces cerevisiae expressing a neutralizing epitope of ApxIIA exotoxin from Actinobacillus pleuropneumoniae induces systemic and mucosal immune responses

An oral delivery system based on ApxIIA#5‐expressed on Saccharomyces cerevisiae was studied for its potential to induce immune responses in mice. Murine bone marrow‐derived dendritic cells (DCs) stimulated in vitro with ApxIIA#5‐expressed on S. cerevisiae upregulated the expression of maturation and activation markers, leading to production of tumor necrosis factor‐α, interleukin (IL)‐1β, IL‐12p70 and IL‐10. Presentation of these activated DCs to cluster of differentiation CD4+ T cells collected from mice that had been orally immunized with the ApxIIA#5‐expressed on S. cerevisiae elicited specific T‐cell proliferation. In addition, the orally immunized mice had stronger antigen‐specific serum IgG and IgA antibody responses and larger numbers of antigen‐specific IgG and IgA antibody‐secreting cells in their spleens, Peyer's patches and lamina propria than did those immunized with vector‐only S. cerevisiae or those not immunized. Furthermore, oral immunization induced T helper 1‐type immune responses mediated via increased serum concentrations of IgG2a and an increase predominantly of IFN‐γ‐producing cells in their spleens and lamina propria. Our findings suggest that surface‐displayed ApxIIA#5‐expressed on S. cerevisiae may be a promising candidate for an oral vaccine delivery system for eliciting systemic and mucosal immunity.     

Oral vaccination of mice against Helicobacter pylori with recombinant Lactococcus lactis expressing urease subunit B

To determine whether a protective immune response could be elicited by oral delivery of a recombinant live bacterial vaccine, Helicobacter pylori urease subunit B (UreB) was expressed for extracellular expression in food-grade bacterium Lactococcus lactis . The UreB-producing strains were then administered orally to mice, and the immune response to UreB was examined. Orally vaccinated mice produced a significant UreB-specific serum immunoglobulin G (IgG) response. Specific anti-UreB IgA responses could be detected in the feces of mice immunized with the secreting lactococcal strain. Mice vaccinated orally were significantly protected against gastric Helicobacter infection following a challenge with H. pylori strain SS1. In conclusion, mucosal vaccination with L. lactis expressing UreB produced serum IgG and UreB-specific fecal IgA, and prevented gastric infection with H. pylori .     

Oral administration of Lactococcus lactis expressing Helicobacter pylori Cag7-ct383 protein induces systemic anti-Cag7 immune response in mice

To express the 3'-region (1152 bp) of the cag7 gene of Helicobacter pylori 51 strain, encoding the C-terminal 383 amino acid (ct383 aa) region of Cag7 protein that is known to cover the needle region of T4SS, in a live delivery vehicle Lactococcus lactis , the cag7-ct383 gene was amplified by PCR. DNA sequence analysis revealed that the amino acid sequence of Cag7-ct383 of H. pylori 51 shared 98.4% and 97.4% identity with H. pylori 26695 and J99, respectively. Intramuscular injection of the GST-Cag7-ct383 fusion protein into a rat could raise the anti-Cag7 antibody, indicating the immunogenicity of the Cag7-ct383 protein. When the cag7-ct383 gene was cloned in Escherichia coli–L. lactis shuttle vector (pMG36e) and transformed into L. lactis , the transformant could produce the Cag7-ct383 protein, as evidenced by Western blot analysis. The Cag7-ct383 protein level in the L. lactis transformant reached a maximum at the early stationary phase without extracellular secretion. The oral administration of the L. lactis transformant into mice generated anti-Cag7 antibody in serum in five of five mice. These results suggest that L. lactis transformant expressing Cag7-ct383 protein may be applicable as an oral vaccine to induce mucosal and systemic immunity to H. pylori .     

Sublingual immunization with an engineered Bacillus subtilis strain expressing tetanus toxin fragment C induces systemic and mucosal immune responses in piglets

Sublingual (SL) and intranasal (IN) administration of a Bacillus subtilis-based tetanus vaccine was tested in piglets, which more closely mimic the human immune system than mice. Piglets were immunized by the SL, IN or oral routes with vaccine expressing tetanus toxin fragment C, or commercial tetanus vaccine given by intramuscular injection as a control. Tetanus toxoid specific ELISA and passive neutralization tests were used to measure IgG and IgA levels in serum and mucosal secretions, and assess protective serum antibodies, respectively. The nature of the immune response was explored by MHC Class II, TGF-β1 expression, and ELISA assays for multiple cytokines. SL or IN immunization of piglets induced neutralizing tetanus toxoid specific serum antibody and local salivary and vaginal IgA responses. Standard tetanus vaccine resulted in systemic antibodies, whereas oral administration of the Bacillus-based vaccine was ineffective. Further analyses indicated a balanced Th1/Th2 response to SL or IN immunization. CONCLUSION: This study demonstrates for the first time that SL or IN administration is effective for inducing both systemic and mucosal responses in a piglet model, indicating that SL or IN delivery of a B. subtilis-based tetanus vaccine can be a simple, non-invasive, low cost strategy to induce immunity to tetanus.     

Oral immunization with transgenic rice seeds expressing VP2 protein of infectious bursal disease virus induces protective immune responses in chickens

The expression of infectious bursal disease virus (IBDV) host-protective immunogen VP2 protein in rice seeds, its immunogenicity and protective capability in chickens were investigated. The VP2 cDNA of IBDV strain ZJ2000 was cloned downstream of the Gt1 promoter of the rice glutelin GluA-2 gene in the binary expression vector, pCambia1301-Gt1. Agrobacterium tumefaciens containing the recombinant vector was used to transform rice embryogenic calli, and 121 transgenic lines were obtained and grown to maturity in a greenhouse. The expression level of VP2 protein in transgenic rice seeds varied from 0.678% to 4.521% µg/mg of the total soluble seed protein. Specific pathogen-free chickens orally vaccinated with transgenic rice seeds expressing VP2 protein produced neutralizing antibodies against IBDV and were protected when challenged with a highly virulent IBDV strain, BC6/85. These results demonstrate that transgenic rice seeds expressing IBDV VP2 can be used as an effective, safe and inexpensive vaccine against IBDV.     

Oral immunization of mice with transgenic tomato fruit expressing respiratory syncytial virus-F protein induces a systemic immune response

Respiratory syncytial virus (RSV) is one of the most important pathogens of infancy and early childhood. Here a fruit-based edible subunit vaccine against RSV was developed by expressing the RSV fusion (F) protein gene in transgenic tomato plants. The F-gene was expressed in ripening tomato fruit under the control of the fruit-specific E8 promoter. Oral immunization of mice with ripe transgenic tomato fruits led to the induction of both serum and mucosal RSV-F specific antibodies. The ratio of immunoglobulin subclasses produced in response to immunization suggested that a type 1 T-helper cell immune response was preferentially induced. Serum antibodies showed an increased titer when the immunized mice were exposed to inactivated RSV antigen.     

Oral immunization of mice with plant-derived fimbrial adhesin FaeG induces systemic and mucosal K88ad enterotoxigenic Escherichia coli-specific immune responses

The importance of adhesins in pathogenicity has resulted in them being useful targets in the defense against bacterial infections. To produce edible vaccines against piglet diarrhea caused by enterotoxigenic Escherichia coli (ETEC), plants were genetically engineered to produce recombinant fimbrial adhesin FaeG. To evaluate the efficacy of the edible vaccine FaeG in mice, the soluble protein extracts were examined by about 15 microg recombinant FaeG for each oral immunization dose per mouse. After four doses of vaccination, both IgG and IgA antibodies specific to K88ad fimbriae were elicited in serum, and specific IgA antibodies were also evoked in feces of the immunized mice. Moreover, visible K88ad ETEC agglutination by the specific serum from the immunized mice was observed, implying the antibody was highly specific and effective. Results from an in vitro villous-adhesion assay further confirmed that serum antibodies of the immunized mice could inhibit K88ad ETEC from adhering to pig intestinal receptors, further demonstrating the oral immune efficacy of the plant-derived FaeG. This study provides a promising, noninvasive method for vaccinating swine by feeding supplements of transgenic plant. Moreover, the low cost and ease of delivery of this edible ETEC vaccine will facilitate its application in economically disadvantaged regions.     

DNA-plasmids of HIV-1 induce systemic and mucosal immune responses

DNA-based immunization has been shown to induce protective immunity against several microbial pathogens including HIV-1. Several routes of DNA vaccination have been exploited. However, the properties of the immune responses seem to differ with the different routes used for DNA delivery, ultimately affecting the outcome of experimental challenge. We measured the primary immune response following one vaccination. This report presents differences associated with three different DNA delivery routes: intramuscular injection, intranasal application, and gene-gun based immunization. Induction of systemic humoral immune responses was achieved most efficiently by either intranasal or gene-gun mediated immunization, followed by intramuscular injection. Mucosal IgA was reproducibly induced by intranasal instillation of the DNA, and found in lung washings, faeces, and vaginal washings. Cytotoxic T cells were not induced by a single immunization, but were observed after three immunizations using intramuscular injections.     

DNA immunization with HIV-1 tat mutated in the trans activation domain induces humoral and cellular immune responses against wild-type Tat

Intramuscular immunization of mice with plasmids encoding two transdominant negative mutants of the HIV-1 Tat protein (Tat22 and Tat22/37) elicited a humoral response to wild-type Tat that is comparable to that induced by inoculation of wild-type tat DNA or Tat protein. The percentage of the responders and the Ab titers continued to increase after three additional DNA boosts and pretreatment with bupivacaine at the site of inoculation, without a significant difference (p > 0.05) among the three groups of mice immunized with mutant and wild-type tat genes. By utilizing synthetic peptides representing the amino acid sequence of Tat, one major B cell epitope was defined within the cysteine-rich domain of Tat. Anti-Tat IgG Abs directed against this epitope were found in mice immunized with all tat DNA constructs, whereas different Tat epitopes were detected in mice immunized with the Tat protein. Similarly, IgG2a was the predominant isotype in DNA-immunized mice, with both mutants and wild-type tat genes, as compared with protein immunization, which induced mostly IgG1 and IgG3. Sera from most immunized mice neutralized the effect of extracellular Tat in activating HIV-1 replication. A cellular response was also elicited as indicated by the proliferation of splenocytes when stimulated with wild-type Tat. These results indicate that the wild-type Tat Ag is recognized by Abs and T cells induced by DNA immunization with mutated tat genes, suggesting the possible use of these Tat transdominant mutants, lacking viral trans activation activity and capable of blocking wild-type Tat activity, in the development of an anti-HIV-1 vaccine.     

Intranasal immunization of mice with CpG DNA induces strong systemic and mucosal responses that are influenced by other mucosal adjuvants and antigen distribution

BACKGROUND: Synthetic oligodeoxynucleotides (ODN) containing immunostimulatory cytosine-guanine phosphate-linked dinucleotide (CpG) motifs are potent systemic and mucosal adjuvants in mice that have synergistic action with numerous other adjuvants, including alum and cholera toxin (CT). Herein, we evaluate CpG ODN with intranasal (IN) delivery of purified hepatitis B surface antigen (HBsAg), relative to and in combination with CT, Escherichia coli heat labile enterotoxin (LT), the B subunit of CT (CTB), and a nontoxic derivative of LT (LTK63). MATERIALS AND METHODS: BALB/c mice were immunized by IN administration of HBsAg, alone or combined with CT, LT, CTB, or LTK63, and/or CpG ODN, or non-CpG control ODN. In addition, the effect of low-or high-volume administration was assessed, in order to target upper respiratory or entire respiratory tract, respectively. HBsAg-specific systemic (immunoglobulins: IgG, IgG1, IgG2a in plasma) and mucosal (IgA in fecal, lung, vaginal, saliva, and gut samples) humoral responses, as well as cell-mediated immune responses including T-cell proliferation and cytokines (interleukins: IL-4, IL-5; interferon: IFN-gamma) were evaluated. RESULTS: CpG ODN, CT, and LT augmented anti-HBs titers equally, and more so than did CTB or LTK63. CpG ODN acted synergistically with CT and LT, but not CTB or LTK63 to enhance anti-HBs titers. Nevertheless, CpG ODN induced a more Th1-like response for all combinations, compared with the same formulation without CpG. Strength of induced systemic and mucosal immune responses was better with IN delivery of a large volume. A small volume required multiple administrations and higher doses of antigen and adjuvant for equal results. This suggests that delivery of antigen to the lung and/or diges-tive system is superior to delivery to the nasal cavity. CONCLUSIONS: Our results suggest that the synergy between CpG ODN and native toxins (CT, LT) may depend on their enzymatic activity and that the lack of synergy with nontoxic derivatives (LTB, LTK63) arises, since they do not have enzymatic activity. Because both CT and LT are too toxic for use in humans, it is possible that CpG ODN may be combined with bacterial toxin mutants that retain some enzymatic activity to optimize immune augmentation.     

Newcastle disease virus expressing human immunodeficiency virus type 1 envelope glycoprotein induces strong mucosal and serum antibody responses in Guinea pigs

Human immunodeficiency virus type 1 (HIV-1) is transmitted mainly through mucosal sites. Optimum strategies to elicit both systemic and mucosal immunity are critical for the development of vaccines against HIV-1. We therefore sought to evaluate the induction of systemic and mucosal immune responses by the use of Newcastle disease virus (NDV) as a vaccine vector. We generated a recombinant NDV, designated rLaSota/gp160, expressing the gp160 envelope (Env) protein of HIV-1 from an added gene. The gp160 protein expressed by rLaSota/gp160 virus was detected on an infected cell surface and was incorporated into the NDV virion. Biochemical studies showed that gp160 present in infected cells and in the virion formed a higher-order oligomer that retained recognition by conformationally sensitive monoclonal antibodies. Expression of gp160 did not increase the virulence of recombinant NDV (rNDV) strain LaSota. Guinea pigs were administered rLaSota/gp160 via the intranasal (i.n.) or intramuscular (i.m.) route in different prime-boost combinations. Systemic and mucosal antibody responses specific to the HIV-1 envelope protein were assessed in serum and vaginal washes, respectively. Two or three immunizations via the i.n. or i.m. route induced a more potent systemic and mucosal immune response than a single immunization by either route. Priming by the i.n. route was more immunogenic than by the i.m. route, and the same was true for the boosts. Furthermore, immunization with rLaSota/gp160 by any route or combination of routes induced a Th1-type response, as reflected by the induction of stronger antigen-specific IgG2a than IgG1 antibody responses. Additionally, i.n. immunization elicited a stronger neutralizing serum antibody response to laboratory-adapted HIV-1 strain MN.3. These data illustrate that it is feasible to use NDV as a vaccine vector to elicit potent humoral and mucosal responses to the HIV-1 envelope protein.     

Rectal immunization with rotavirus virus-like particles induces systemic and mucosal humoral immune responses and protects mice against rotavirus infection

To evaluate whether the rectal route of immunization may be used to provide appropriate protection against enteric pathogens such as rotaviruses (RV), we studied the antibody response and the protection induced by rectal immunization of mice with RV virus-like particles (VLP). For this purpose, 6-week-old BALBc mice were rectally immunized twice with RV 8-2/6/7-VLP derived from the bovine RV RF81 strain either alone or combined with various adjuvants including four toxins [cholera toxin (CT) and three attenuated Escherichia coli-derived heat-labile toxins (LTs), LT(R192G), LT(R72), and LT(K63)] and two Toll-like receptor-targeting adjuvants (CpG and resiquimod). Six weeks after the second immunization, mice were challenged with murine RV strain ECw. RV VLP administered alone were not immunogenic and did not protect mice against RV challenge. By contrast, RV VLP combined with any of the toxin adjuvants were immunogenic (mice developed significant titers of anti-RV immunoglobulin A [IgA] in both serum and feces and of anti-RV IgG in serum) and either efficiently induced complete protection of the mice (no detectable fecal virus shedding) or, for LT(K63), reduced the amount of fecal virus shedding after RV challenge. When combined with RV VLP, CpG and resiquimod failed to achieve protection, although CpG efficiently induced an antibody response to RV. These results support the consideration of the rectal route for the development of new immunization strategies against RV infection. Rectal delivery of a VLP-based vaccine might allow the use of adjuvants less toxic than, but as efficient as, CT.     

Prime-boost vaccination with HIV-1 Gag protein and cytosine phosphate guanosine oligodeoxynucleotide,followed by adenovirus,induces sustained and robust humoral and cellular immune responses

A prophylactic vaccine for HIV-1 will probably require the induction and maintenance of both humoral and cellular immunity. One current strategy to achieve such long term immune responses is a prime-boost vaccination approach using a DNA priming inoculation, followed by recombinant viral boost. In this report we use a novel prime-boost approach in which the priming injections consist of recombinant HIV-1 Gag protein mixed with cytosine phosphate guanosine oligodeoxynucleotide (CpG ODN), followed by recombinant adenoviral boost expressing HIV-1 Gag. Analysis of the immune responses indicates that HIV-1 Gag protein plus CpG ODN immunization alone induces potent humoral as well as Th1 and CD8+ T cell responses. Boosting with recombinant adenovirus strikingly enhances CD8+, but not Th1, T cell responses, resulting in CD8+ T cell responses far greater in magnitude than Th1 responses. Furthermore, the Th1 and CD8+ T cell responses following prime-boost immunization were seen in both lymphoid and peripheral mucosal organs and were sustained over several months. Together, these data suggest a new immunization approach for elicitation of long term humoral and cellular immune responses.     

重组乳酸乳球菌表达禽流感病毒HA1基因载体的构建及在禽流感病毒防治领域的应用

目的构建以重组乳酸乳球菌为基础的黏膜输送载体。方法以高致病性禽流感病毒H5N1的HA1基因作为研究对象,利用nisin诱导表达控制系统,构建分泌型与非分泌型重组乳酸乳球菌表达载体,经口服灌胃途径免疫BALB/c小鼠,通过ELISA检测小鼠血清IgG和粪便IgA,最后,对免疫后的小鼠进行H5N1病毒攻击实验,进而比较分泌型与非分泌型重组乳酸乳球菌表达载体的免疫效率。结果分泌型重组乳酸乳球菌免疫小鼠后产生的抗体水平（IgG和IgA）高于非分泌型重组乳酸乳球菌,经过同型H5N1病毒攻击后,分泌型重组乳酸乳球菌免疫的小鼠的存活率为80%,而非分泌型重组乳酸乳球菌免疫的小鼠的存活率为60%。结论本研究为防治高致病性禽流感病毒提供可行的思路与方法。     

Expansion and diversification of virus-specific T cells following immunization of human immunodeficiency virus type 1 (HIV-1)-infected individuals with a recombinant modified vaccinia virus Ankara/HIV-1 Gag vaccine

Affordable therapeutic strategies that induce sustained control of human immunodeficiency virus type 1 (HIV-1) replication and are tailored to the developing world are urgently needed. Since CD8(+) and CD4(+) T cells are crucial to HIV-1 control, stimulation of potent cellular responses by therapeutic vaccination might be exploited to reduce antiretroviral drug exposure. However, therapeutic vaccines tested to date have shown modest immunogenicity. In this study, we performed a comprehensive analysis of the changes in virus-specific CD8(+) and CD4(+) T-cell responses occurring after vaccination of 16 HIV-1-infected individuals with a recombinant modified vaccinia virus Ankara-vectored vaccine expressing the consensus HIV-1 clade A Gag p24/p17 sequences and multiple CD8(+) T-cell epitopes during highly active antiretroviral therapy. We observed significant amplification and broadening of CD8(+) and CD4(+) gamma interferon responses to vaccine-derived epitopes in the vaccinees, without rebound viremia, but not in two unvaccinated controls followed simultaneously. Vaccine-driven CD8(+) T-cell expansions were also detected by tetramer reactivity, predominantly in the CD45RA(-) CCR7(+) or CD45RA(-) CCR7(-) compartments, and persisted for at least 1 year. Expansion was associated with a marked but transient up-regulation of CD38 and perforin within days of vaccination. Gag-specific CD8(+) and CD4(+) T-cell proliferation also increased postvaccination. These data suggest that immunization with MVA.HIVA is a feasible strategy to enhance potentially protective T-cell responses in individuals with chronic HIV-1 infection.     

Copolymer-1 induces adaptive immune anti-inflammatory glial and neuroprotective responses in a murine model of HIV-1 encephalitis

Copolymer-1 (COP-1) elicits neuroprotective activities in a wide range of neurodegenerative disorders. This occurs, in part, by adaptive immune-mediated suppression of microglial inflammatory responses. Because HIV infection and immune activation of perivascular macrophages and microglia drive a metabolic encephalopathy, we reasoned that COP-1 could be developed as an adjunctive therapy for disease. To test this, we developed a novel animal model system that reflects HIV-1 encephalitis in rodents with both innate and adaptive arms of the immune system. Bone marrow-derived macrophages were infected with HIV-1/vesicular stomatitis-pseudotyped virus and stereotactically injected into the basal ganglia of syngeneic mice. HIV-1 pseudotyped with vesicular stomatitis virus envelope-infected bone marrow-derived macrophages induced significant neuroinflammation, including astrogliosis and microglial activation with subsequent neuronal damage. Importantly, COP-1 immunization reduced astro- and microgliosis while diminishing neurodegeneration. Hippocampal neurogenesis was, in part, restored. This paralleled reductions in proinflammatory cytokines, including TNF-alpha and IL-1beta, and inducible NO synthase, and increases in brain-derived neurotrophic factor. Ingress of Foxp3- and IL-4-expressing lymphocytes into brains of COP-1-immunized animals was observed. We conclude that COP-1 may warrant therapeutic consideration for HIV-1-associated cognitive impairments.     

Attenuation of simian immunodeficiency virus SIVmac239 infection by prophylactic immunization with dna and recombinant adenoviral vaccine vectors expressing Gag

The prophylactic efficacy of DNA and replication-incompetent adenovirus serotype 5 (Ad5) vaccine vectors expressing simian immunodeficiency virus (SIV) Gag was examined in rhesus macaques using an SIVmac239 challenge. Cohorts of either Mamu-A*01(+) or Mamu-A*01(-) macaques were immunized with a DNA prime-Ad5 boost regimen; for comparison, a third cohort consisting of Mamu-A*01(+) monkeys was immunized using the Ad5 vector alone for both prime and boost. All animals, along with unvaccinated control cohorts of Mamu-A*01(+) and Mamu-A*01(-) macaques, were challenged intrarectally with SIVmac239. Viral loads were measured in both peripheral and lymphoid compartments. Only the DNA prime-Ad5-boosted Mamu-A*01(+) cohort exhibited a notable reduction in peak plasma viral load (sevenfold) as well as in early set-point viral burdens in both plasma and lymphoid tissues (10-fold) relative to those observed in the control monkeys sharing the same Mamu-A*01 allele. The degree of control in each animal correlated with the levels of Gag-specific immunity before virus challenge. However, virus control was short-lived, and indications of viral escape were evident as early as 6 months postinfection. The implications of these results in vaccine design and clinical testing are discussed.