A DNA Vaccine against Yellow Fever Virus: Development and Evaluation

Attenuated yellow fever (YF) virus 17D/17DD vaccines are the only available protection from YF infection, which remains a significant source of morbidity and mortality in the tropical areas of the world. The attenuated YF virus vaccine, which is used worldwide, generates both long-lasting neutralizing antibodies and strong T-cell responses. However, on rare occasions, this vaccine has toxic side effects that can be fatal. This study presents the design of two non-viral DNA-based antigen formulations and the characterization of their expression and immunological properties. The two antigen formulations consist of DNA encoding the full-length envelope protein (p/YFE) or the full-length envelope protein fused to the lysosomal-associated membrane protein signal, LAMP-1 (pL/YFE), aimed at diverting antigen processing/presentation through the major histocompatibility complex II precursor compartments. The immune responses triggered by these formulations were evaluated in H2b and H2d backgrounds, corresponding to the C57Bl/6 and BALB/c mice strains, respectively. Both DNA constructs were able to induce very strong T-cell responses of similar magnitude against almost all epitopes that are also generated by the YF 17DD vaccine. The pL/YFE formulation performed best overall. In addition to the T-cell response, it was also able to stimulate high titers of anti-YF neutralizing antibodies comparable to the levels elicited by the 17DD vaccine. More importantly, the pL/YFE vaccine conferred 100% protection against the YF virus in intracerebrally challenged mice. These results indicate that pL/YFE DNA is an excellent vaccine candidate and should be considered for further developmental studies.     

Immunization of Pigs with a Particle-Mediated DNA Vaccine to Influenza A Virus Protects against Challenge with Homologous Virus

Particle-mediated delivery of a DNA expression vector encoding the hemagglutinin (HA) of an H1N1 influenza virus (A/Swine/Indiana/1726/88) to porcine epidermis elicits a humoral immune response and accelerates the clearance of virus in pigs following a homotypic challenge. Mucosal administration of the HA expression plasmid elicits an immune response that is qualitatively different than that elicited by the epidermal vaccination in terms of inhibition of the initial virus infection. In contrast, delivery of a plasmid encoding an influenza virus nucleoprotein from A/PR/8/34 (H1N1) to the epidermis elicits a strong humoral response but no detectable protection in terms of nasal virus shed. The efficacy of the HA DNA vaccine was compared with that of a commercially available inactivated whole-virus vaccine as well as with the level of immunity afforded by previous infection. The HA DNA and inactivated viral vaccines elicited similar protection in that initial infection was not prevented, but subsequent amplification of the infection is limited, resulting in early clearance of the virus. Convalescent animals which recovered from exposure to virulent swine influenza virus were completely resistant to infection when challenged. The porcine influenza A virus system is a relevant preclinical model for humans in terms of both disease and gene transfer to the epidermis and thus provides a basis for advancing the development of DNA-based vaccines.     

Electroporation-Mediated Immunization of a Candidate DNA Vaccine Expressing Dengue Virus Serotype 4 prM-E Antigen Confers Long-Term Protection in Mice

Dengue fever, caused by dengue viruses(DENVs), is a widespread mosquito-borne zoonotic disease; however, there is no available anti-dengue vaccine for worldwide use. In the current study, a DNA vaccine candidate(pV-D4 ME) expressing prM-E protein of DENV serotype 4(DENV-4) was constructed, and its immunogenicity and protection were evaluated in immunocompetent BALB/c mice. The pV-D4 ME candidate vaccine induced effective humoral and cellular immunity of mice against DENV-4 in vivo when administered both at 50 μg and 5 μg through electroporation. Two weeks after receiving three immunizations, both doses of pV-D4 ME DNA were shown to confer effective protection against lethal DENV-4 challenge. Notably, at 6 months after the three immunizations, 50 μg, but not 5 μg, of pV-D4 ME could provide stable protection(100% survival rate) against DENV-4 lethal challenge without any obvious clinical signs. These results suggest that immunization with 50 μg pV-D4 ME through electroporation could confer effective and long-term protection against DENV-4, offering a promising approach for development of a novel DNA vaccine against DENVs.     

Oral Immunization of Macaques with Attenuated Vaccine Virus Induces Protection against Vaginally Transmitted AIDS

The chimeric simian-human immunodeficiency virus SHIV_KU-1, bearing the envelope of human immunodeficiency virus type 1 (HIV-1), causes fulminant infection with subtotal loss of CD4⁺ T cells followed by development of AIDS in intravaginally inoculated macaques and thus provides a highly relevant model of sexually transmitted disease caused by HIV-1 in human beings. Previous studies using this SHIV model had shown that the vpu and nef genes were important in pathogenesis of the infection, and so we deleted portions of these genes to create two vaccines, ΔvpuΔnefSHIV-4 (vaccine 1) and ΔvpuSHIV_PPc (vaccine 2). Six adult macaques were immunized subcutaneously with vaccine 1, and six were immunized orally with vaccine 2. Both viruses caused infection in all inoculated animals, but whereas vaccine 1 virus caused only a nonproductive type of infection, vaccine 2 virus replicated productively but transiently for a 6- to 10-week period. Both groups were challenged 6 to 7 months later with pathogenic SHIV_KU-1 by the intravaginal route. All four unvaccinated controls developed low CD4⁺ T-cell counts (<200/μl) and AIDS. The 12 vaccinated animals all became infected with SHIV_KU-1, and two in group 1 developed a persistent productive infection followed by development of AIDS in one. The other 10 have maintained almost complete control over virus replication even though spliced viral RNA was detected in lymph nodes. This suppression of virus replication correlated with robust antiviral cell-mediated immune responses. This is the first demonstration of protection against virulent SHIV administered by the intravaginal route. This study supports the concept that sexually transmitted HIV disease can be prevented by parenteral or oral immunization.     

Construction and Characterization of a Single-Cycle Chimeric Flavivirus Vaccine Candidate That Protects Mice against Lethal Challenge with Dengue Virus Type 2

We have previously described a novel flavivirus vaccine technology based on a single-cycle, capsid (C) gene-deleted flavivirus called RepliVAX. RepliVAX can be propagated in cells that express high levels of C but undergoes only a single cycle of infection in vaccinated hosts. Here we report that we have adapted our RepliVAX technology to produce a dengue vaccine by replacing the prM/E genes of RepliVAX WN (a West Nile virus [WNV] RepliVAX) with the same genes of dengue virus type 2 (DENV2). Our first RepliVAX construct for dengue virus (RepliVAX D2) replicated poorly in WNV C-expressing cells. However, addition of mutations in prM and E that were selected during blind passage of a RepliVAX D2 derivative was used to produce a second-generation RepliVAX D2 (designated D2.2) that displayed acceptable growth in WNV C-expressing cells. RepliVAX D2.2 grew better in DENV2 C-expressing cells than WNV C-expressing cells, but after several passages in DENV2 C-expressing cells it acquired further mutations that permitted efficient growth in WNV C-expressing cells. We tested the potency and efficacy of RepliVAX D2.2 in a well-described immunodeficient mouse model for dengue (strain AG129; lacking the receptors for both type I and type II interferons). These mice produced dose-dependent DENV2-neutralizing antibody responses when vaccinated with RepliVAX D2.2. When challenged with 240 50% lethal doses of DENV2, mice given a single inoculation of RepliVAX D2.2 survived significantly longer than sham-vaccinated animals, although some of these severely immunocompromised mice eventually died from the challenge. Taken together these studies indicate that the RepliVAX technology shows promise for use in the development of vaccines that can be used to prevent dengue.     

An Epitope-Substituted DNA Vaccine Improves Safety and Immunogenicity against Dengue Virus Type 2

Dengue virus (DENV), a global disease, is divided into four serotypes (DENV1-4). Cross-reactive and non-neutralizing antibodies against envelope (E) protein of DENV bind to the Fcγ receptors (FcγR) of cells, and thereby exacerbate viral infection by heterologous serotypes via antibody-dependent enhancement (ADE). Identification and modification of enhancing epitopes may mitigate enhancement of DENV infection. In this study, we characterized the cross-reactive DB21-6 and DB39-2 monoclonal antibodies (mAbs) against domain I-II of DENV; these antibodies poorly neutralized and potently enhanced DENV infection both in vitro and in vivo. In addition, two enhancing mAbs, DB21-6 and DB39-2, were observed to compete with sera antibodies from patients infected with dengue. The epitopes of these enhancing mAbs were identified using phage display, structural prediction, and mapping of virus-like particle (VLP) mutants. N8, R9, V12, and E13 are the reactive residues of DB21-6, while N8, R9, and E13 are the reactive residues of DB39-2. N8 substitution tends to maintain VLP secretion, and decreases the binding activity of DB21-6 and DB39-2. The immunized sera from N8 substitution (N8R) DNA vaccine exerted greater neutralizing and protective activity than wild-type (WT)-immunized sera, both in vitro and in vivo. Furthermore, treatment with N8R-immunized sera reduced the enhancement of mortality in AG129 mice. These results support identification and substitution of enhancing epitope as a novel strategy for developing safe dengue vaccines.     

Protective Efficacy of a Single Immunization of a Chimeric Adenovirus Vector-Based Vaccine against Simian Immunodeficiency Virus Challenge in Rhesus Monkeys

Rare serotype and chimeric recombinant adenovirus (rAd) vectors that evade anti-Ad5 immunity are currently being evaluated as potential vaccine vectors for human immunodeficiency virus type 1 and other pathogens. We have recently reported that a heterologous rAd prime-boost regimen expressing simian immunodeficiency virus (SIV) Gag afforded durable partial immune control of an SIV challenge in rhesus monkeys. However, single-shot immunization may ultimately be preferable for global vaccine delivery. We therefore evaluated the immunogenicity and protective efficacy of a single immunization of chimeric rAd5 hexon hypervariable region 48 (rAd5HVR48) vectors expressing SIV Gag, Pol, Nef, and Env against a homologous SIV challenge in rhesus monkeys. Inclusion of Env resulted in improved control of peak and set point SIV RNA levels following challenge. In contrast, DNA vaccine priming did not further improve the protective efficacy of rAd5HVR48 vectors in this system.Heterologous prime-boost vaccine regimens have proven substantially more immunogenic than single vector immunizations in a variety of experimental models, but a single-shot vaccine would presumably be ideal for eventual global delivery. The potential utility of single-shot vaccines against pathogenic simian immunodeficiency virus (SIV) challenges in rhesus monkeys has not been well characterized. We therefore evaluated the protective efficacy of a single immunization of recombinant chimeric adenovirus type 5 (rAd5) hexon hypervariable region 48 (rAd5HVR48) vectors (15) expressing SIV Gag, Pol, Nef, and Env against a pathogenic SIV challenge in rhesus monkeys. These vectors contain the HVRs of the rare Ad48 serotype and have been shown to evade dominant Ad5 hexon-specific neutralizing antibodies (NAbs) (15). We also assessed the potential utility of inclusion of Env as an immunogen (6, 7, 17) and the degree to which DNA vaccine priming would enhance the protective efficacy afforded by a single rAd5HVR48 immunization (2, 7, 18, 21).Thirty adult rhesus monkeys (n = 6/group) lacking the Mamu-A*01, Mamu-B*17, and Mamu-B*08 class I alleles were primed with plasmid DNA vaccines and boosted with rAd5HVR48 vectors as follows: (1) adjuvanted DNA prime, rAd5HVR48 boost; (2) DNA prime, rAd5HVR48 boost; (3) rAd5HVR48 alone; (4) rAd5HVR48 alone (excluding Env); and (5) sham controls. Monkeys in groups 1 to 3 received vectors expressing SIVmac239 Gag, Pol, Nef, and Env, whereas monkeys in group 4 received vectors expressing only Gag, Pol, and Nef. The DNA vaccine adjuvants in group 1 were plasmids expressing the rhesus chemokine MIP-1α and Flt3L, which have been shown to increase recruitment of dendritic cells and to improve DNA vaccine immunogenicity (20). Monkeys were primed intramuscularly with a total dose of 4 mg of DNA vaccines at weeks 0, 4, and 8. All animals then received a single intramuscular immunization of 4 × 10¹⁰ viral particles (vp) of rAd5HVR48 at week 24. At week 52, animals were challenged intravenously (i.v.) with 100 monkey infectious doses of SIVmac251 (7, 10).     

Limited Protection from a Pathogenic Chimeric Simian-Human Immunodeficiency Virus Challenge following Immunization with Attenuated Simian Immunodeficiency Virus

Two live attenuated single-deletion mutant simian immunodeficiency virus (SIV) constructs, SIV_239Δnef and SIV_PBj6.6Δnef, were tested for their abilities to stimulate protective immunity in macaques. During the immunization period the animals were examined for specific immune responses and virus growth. Each construct generated high levels of specific immunity in all of the immunized animals. The SIV_239Δnef construct was found to grow to high levels in all immunized animals, with some animals remaining positive for virus isolation and plasma RNA throughout the immunization period. The SIV_PBj6.6Δnef was effectively controlled by all of the immunized animals, with virus mostly isolated only during the first few months following immunization and plasma RNA never detected. Following an extended period of immunization of over 80 weeks, the animals were challenged with a pathogenic simian-human immunodeficiency virus (SHIV) isolate, SIV_89.6PD, by intravenous injection. All of the SIV_239Δnef-immunized animals became infected with the SHIV isolate; two of five animals eventually controlled the challenge and three of five animals, which failed to check the immunizing virus, progressed to disease state before the unvaccinated controls. One of five animals immunized with SIV_PBj6.6Δnef totally resisted infection by the challenge virus, while three others limited its growth and the remaining animal became persistently infected and eventually died of a pulmonary thrombus. These data indicate that vaccination with attenuated SIV can protect macaques from disease and in some cases from infection by a divergent SHIV. However, if animals are unable to control the immunizing virus, potential damage that can accelerate the disease course of a pathogenic challenge virus may occur.     

乙脑/登革2型嵌合病毒的构建

在乙脑病毒SA14-14-2株复制子载体pPartial△prM/E中克隆入DV2(Dengue virus serotype 2)的prM/E基因,构建乙脑/登革2型嵌合体克隆。将嵌合体克隆线性化后体外转录,获得的RNA转染BHK-21细胞,5～7d可观察到CPE。收获病毒上清液分别感染BHK-21细胞及C6/36细胞。接种于C6/36细胞中的嵌合病毒可使细胞出现CPE,RT-PCR、间接免疫荧光和Western blot检测显示:获得的嵌合病毒具有预期嵌合性核酸并能表达DV2的包膜蛋白,但不能在BHK-21细胞中传代培养。成功构建的乙脑/登革2型感染性克隆为进一步研究登革病毒疫苗奠定了基础。     

A Chimeric Dengue Virus Vaccine using Japanese Encephalitis Virus Vaccine Strain SA14-14-2 as Backbone Is Immunogenic and Protective against Either Parental Virus in Mice and Nonhuman Primates

The development of a safe and efficient dengue vaccine represents a global challenge in public health. Chimeric dengue viruses (DENV) based on an attenuated flavivirus have been well developed as vaccine candidates by using reverse genetics. In this study, based on the full-length infectious cDNA clone of the well-known Japanese encephalitis virus live vaccine strain SA14-14-2 as a backbone, a novel chimeric dengue virus (named ChinDENV) was rationally designed and constructed by replacement with the premembrane and envelope genes of dengue 2 virus. The recovered chimeric virus showed growth and plaque properties similar to those of the parental DENV in mammalian and mosquito cells. ChinDENV was highly attenuated in mice, and no viremia was induced in rhesus monkeys upon subcutaneous inoculation. ChinDENV retained its genetic stability and attenuation phenotype after serial 15 passages in cultured cells. A single immunization with various doses of ChinDENV elicited strong neutralizing antibodies in a dose-dependent manner. When vaccinated monkeys were challenged with wild-type DENV, all animals except one that received the lower dose were protected against the development of viremia. Furthermore, immunization with ChinDENV conferred efficient cross protection against lethal JEV challenge in mice in association with robust cellular immunity induced by the replicating nonstructural proteins. Taken together, the results of this preclinical study well demonstrate the great potential of ChinDENV for further development as a dengue vaccine candidate, and this kind of chimeric flavivirus based on JE vaccine virus represents a powerful tool to deliver foreign antigens.     

Yellow Fever Vaccine. II. Antigenicity and Neurovirulence of a Vaccine Seed Free from Avian Leukosis Virus

Avian leukosis virus (ALV)-free candidate primary and secondary seed lots were indistinguishable from corresponding ALV-contaminated lots with respect to (i) potency as measured by titration in newborn and weanling mice and in the MA-104 plaque system, (ii) degree of viscerotropism as measured by viremia in monkeys, (iii) neurotropism as determined by the monkey neurovirulence test, and (iv) potency as determined by antibody response in monkeys inoculated by the intracerebral route.     

Construction, Safety, and Immunogenicity in Nonhuman Primates of a Chimeric Yellow Fever-Dengue Virus Tetravalent Vaccine

We previously reported construction of a chimeric yellow fever-dengue type 2 virus (YF/DEN2) and determined its safety and protective efficacy in rhesus monkeys (F. Guirakhoo et al., J. Virol. 74:5477-5485, 2000). In this paper, we describe construction of three additional YF/DEN chimeras using premembrane (prM) and envelope (E) genes of wild-type (WT) clinical isolates: DEN1 (strain PUO359, isolated in 1980 in Thailand), DEN3 (strain PaH881/88, isolated in 1988 in Thailand), and DEN4 (strain 1228, isolated in 1978 in Indonesia). These chimeric viruses (YF/DEN1, YF/DEN3, and YF/DEN4) replicated to ~7.5 log(10) PFU/ml in Vero cells, were not neurovirulent in 3- to 4-week-old ICR mice inoculated by the intracerebral route, and were immunogenic in monkeys. All rhesus monkeys inoculated subcutaneously with one dose of these chimeric viruses (as monovalent or tetravalent formulation) developed viremia with magnitudes similar to that of the YF 17D vaccine strain (YF-VAX) but significantly lower than those of their parent WT viruses. Eight of nine monkeys inoculated with monovalent YF/DEN1 -3, or -4 vaccine and six of six monkeys inoculated with tetravalent YF/DEN1-4 vaccine seroconverted after a single dose. When monkeys were boosted with a tetravalent YF/DEN1-4 dose 6 months later, four of nine monkeys in the monovalent YF/DEN groups developed low levels of viremia, whereas no viremia was detected in any animals previously inoculated with either YF/DEN1-4 vaccine or WT DEN virus. An anamnestic response was observed in all monkeys after the second dose. No statistically significant difference in levels of neutralizing antibodies was observed between YF virus-immune and nonimmune monkeys which received the tetravalent YF/DEN1-4 vaccine or between tetravalent YF/DEN1-4-immune and nonimmune monkeys which received the YF-VAX. However, preimmune monkeys developed either no detectable viremia or a level of viremia lower than that in nonimmune controls. This is the first recombinant tetravalent dengue vaccine successfully evaluated in nonhuman primates.     

鼠巨细胞病毒 IE-1核酸疫苗和灭活疫苗联合免疫抗病毒感染的研究

巨细胞病毒（Cytomegalovirus,CMV）在人群中感染普遍,对婴幼儿及免疫低下人群中造成严重疾病,目前还没有针对该病毒的商品化疫苗。本研究以BALB/c小鼠为动物模型,探讨鼠巨细胞病毒（Murine cytomega-lovirus,MCMV）IE-1 DNA疫苗和MCMV灭活疫苗联合免疫抗MCMV感染的免疫保护效果。将编码IE-1基因的DNA疫苗（pIE-1）通过肌肉注射辅以电穿孔的方式对小鼠进行初免,再用全病毒灭活疫苗单独或者辅以MF59佐剂进行加强免疫,分别通过ELISA和ELISPOT方法检测到联合免疫策略在免疫组小鼠体内诱导了MC-MV特异性的抗体应答和CTL应答;免疫两周后用3＆#215;LD50致死剂量MCMV感染小鼠,疫苗对小鼠的免疫保护通过检测小鼠存活率、重要器官中的病毒滴度及体重丢失率来评价。结果显示,与单独免疫DNA疫苗或灭活疫苗相比,IE-1 DNA疫苗联合灭活疫苗组能同时在小鼠体内诱导体液免疫和细胞免疫应答,并提供小鼠完全保护;而且MF59辅以灭活疫苗免疫小鼠能增强疫苗的免疫效果。     

Sublingual Immunization of Trivalent Human Papillomavirus DNA Vaccine in Baculovirus Nanovector for Protection against Vaginal Challenge

Here, we report the immunogenicity of a sublingually delivered, trivalent human papillomavirus (HPV) DNA vaccine encapsidated in a human endogenous retrovirus (HERV) envelope-coated, nonreplicable, baculovirus nanovector. The HERV envelope-coated, nonreplicable, baculovirus-based DNA vaccine, encoding HPV16L1, -18L1 and -58L1 (AcHERV-triHPV), was constructed and sublingually administered to mice without adjuvant. Following sublingual (SL) administration, AcHERV-triHPV was absorbed and distributed throughout the body. At 15 minutes and 1 day post-dose, the distribution of AcHERV-triHPV to the lung was higher than that to other tissues. At 30 days post-dose, the levels of AcHERV-triHPV had diminished throughout the body. Six weeks after the first of three doses, 1×10⁸ copies of SL AcHERV-triHPV induced HPV type-specific serum IgG and neutralizing antibodies to a degree comparable to that of IM immunization with 1×10⁹ copies. AcHERV-triHPV induced HPV type-specific vaginal IgA titers in a dose-dependent manner. SL immunization with 1×10¹⁰ copies of AcHERV-triHPV induced Th1 and Th2 cellular responses comparable to IM immunization with 1×10⁹ copies. Molecular imaging revealed that SL AcHERV-triHPV in mice provided complete protection against vaginal challenge with HPV16, HPV18, and HPV58 pseudoviruses. These results support the potential of SL immunization using multivalent DNA vaccine in baculovirus nanovector for induction of mucosal, systemic, and cellular immune responses.     

含2A片段的重组黄热病毒17D疫苗表达载体的构建

黄热疫苗是一种减毒的黄热病毒17D(YF-17D)活疫苗,是现有疫苗中最安全、最有效的疫苗之一,适于发展为疫苗载体。用RT-PCR法扩增出覆盖YF-17D全长基因组的3个cDNA片段:5′cDNA(A)、3′cDNA(B)和中间cDNA(C),同时引入SP6增强子序列、酶切位点和重复序列。顺序将A和B同E.coli-yeast穿梭质粒pRS424连接,再与C共转染酵母菌,利用缺少色氨酸和尿嘧啶的选择性固体培养基筛选出含YF-17D全长基因组的cDNA质粒。以该质粒为模板,经过DNA重组和酵母同源重组,获得含有口蹄疫病毒蛋白水解酶2A片段的重组YF-17D表达载体。将该表达载体体外转录后,电击转染BHK-21细胞。间接免疫荧光检测结果表明,RNA转录体在BHK-21细胞中进行了稳定的表达;滴度测定与形态学观察结果表明,重组病毒在细胞中的生长曲线等特征同母本YF-17D十分相似。结果提示,利用酵母菌同源重组在2A部位引入异种抗原基因,重组YF-17D表达载体pRS-YF-2A1具有成为高效活疫苗表达载体的潜力。     

DNA Vaccine Encoding the Chimeric Form of Schistosoma mansoni Sm-TSP2 and Sm29 Confers Partial Protection against Challenge Infection

Schistosomiasis is an important parasitic disease worldwide that affects more than 207 million people in 76 countries and causes approximately 250,000 deaths per year. The best long-term strategy to control schistosomiasis is through immunization combined with drug treatment. Due to the ability of DNA vaccines to generate humoral and cellular immune responses, such vaccines are considered a promising approach against schistosomiasis. Sm29 and tetraspanin-2 (Sm-TSP2) are two proteins that are located in the S. mansoni tegument of adult worms and schistosomula and induce high levels of protection through recombinant protein immunization. In this study, we transfected BHK-21 cells with plasmids encoding Sm29, Sm-TSP2 or a chimera containing both genes. Using RT-PCR analysis and western blot, we confirmed that the DNA vaccine constructs were transcribed and translated, respectively, in BHK-21 cells. After immunization of mice, we evaluated the reduction in worm burden. We observed worm burden reductions of 17-22%, 22%, 31-32% and 24-32% in animals immunized with the pUMVC3/Sm29, pUMVC3/SmTSP-2, pUMVC3/Chimera and pUMVC3/Sm29 + pUMVC3/SmTSP-2 plasmids, respectively. We evaluated the humoral response elicited by DNA vaccines, and animals immunized with pUMVC3/Sm29 and pUMVC3/Sm29 + pUMVC3/SmTSP-2 showed higher titers of anti-Sm29 antibodies. The cytokine profile produced by the spleen cells of immunized mice was then evaluated. We observed higher production of Th1 cytokines, such as TNF-α and IFN-γ, in vaccinated mice and no significant production of IL-4 and IL-5. The DNA vaccines tested in this study showed the ability to generate a protective immune response against schistosomiasis, probably through the production of Th1 cytokines. However, future strategies aiming to optimize the protective response induced by a chimeric DNA construct need to be developed.     

马传染性贫血强/弱毒嵌合病毒的体外构建

马传染性贫血病毒(equine infectious anemia virus,EIAV)引起马传染性贫血(简称马传贫),导致马持续性感染和反复病毒血症[1].EIAV与人免疫缺陷病毒Ⅰ型(HIV-1)同属反转录病毒科慢病毒属,二者有很多相似的特性[2].在反转录病毒前病毒基因组两端含有长末端重复序列(long terminal repeat,LTR).LTR含有真核启动子,其中含有病毒转录调控顺式作用位点,病毒编码的反式作用因子与其结合后可以反式激活基因的表达,对病毒基因的表达和其它生命活动起重要调控作用[3,4].因此,LTR序列的变异可能会引起病毒转录和复制方式的改变,进而引起其细胞嗜性和致病性的改变[5,6].为了探讨LTR在EIAV病毒复制和转录过程中的作用,并进一步研究EIAV的致病和免疫机制,用EIAV强毒L株LTR置换了以前构建的EIAV DLA(弱毒)感染性分子克隆中的LTR,构建了马传贫强/弱毒嵌合分子克隆,并获得了具有感染性的强/弱毒嵌合病毒.     

Management of Hepatitis E Virus (HEV) Zoonotic Transmission: Protection of Rabbits against HEV Challenge following Immunization with HEV 239 Vaccine

Hepatitis E virus (HEV) constitutes a significant health burden worldwide, with an estimated approximately 33% of the world’s population exposed to the pathogen. The recent licensed HEV 239 vaccine in China showed excellent protective efficacy against HEV of genotypes 1 and 4 in the general population and pregnant women. Because hepatitis E is a zoonosis, it is also necessary to ascertain whether this vaccine can serve to manage animal sources of human HEV infection. To test the efficacy of the HEV 239 vaccine in protecting animal reservoirs of HEV against HEV infection, twelve specific-pathogen-free (SPF) rabbits were divided randomly into two groups of 6 animals and inoculated intramuscularly with HEV 239 and placebo (PBS). All animals were challenged intravenously with swine HEV of genotype 4 or rabbit HEV seven weeks after the initial immunization. The course of infection was monitored for 10 weeks by serum ALT levels, duration of viremia and fecal virus excretion and HEV antibody responses. All rabbits immunized with HEV 239 developed high titers of anti-HEV and no signs of HEV infection were observed throughout the experiment, while rabbits inoculated with PBS developed viral hepatitis following challenge, with liver enzyme elevations, viremia, and fecal virus shedding. Our data indicated that the HEV 239 vaccine is highly immunogenic for rabbits and that it can completely protect rabbits against homologous and heterologous HEV infections. These findings could facilitate the prevention of food-borne sporadic HEV infection in both developing and industrialized countries.     

CD40L-Adjuvanted DNA/Modified Vaccinia Virus Ankara Simian Immunodeficiency Virus (SIV) Vaccine Enhances Protection against Neutralization-Resistant Mucosal SIV Infection

Here, we show that a CD40L-adjuvanted DNA/modified vaccinia virus Ankara (MVA) simian immunodeficiency virus (SIV) vaccine enhances protection against a pathogenic neutralization-resistant mucosal SIV infection, improves long-term viral control, and prevents AIDS. Analyses of serum IgG antibodies to linear peptides of SIV Env revealed a strong response to V2, with targeting of fewer epitopes in the immunodominant region of gp41 (gp41-ID) and the V1 region as a correlate for enhanced protection. Greater expansion of antiviral CD8 T cells in the gut correlated with long-term viral control.