重组痘苗病毒嵌合巨蛋白的免疫学研究

目的　pSFJ1 6与pSFJ38均是以牛痘病毒包涵体 (ATI)启动子和分别串联的 1 6个和 38个p7 5突变型早期启动子为基本构件组成的复合型启动子 (ATI-p7 5)、痘苗病毒复制非必需区血凝素 (HA)基因为侧翼的痘苗病毒表达载体。分别插入编码艾滋病病毒 (HIV - 1 )外膜蛋白env、核心蛋白gag与编码干扰素 (IFNα - 2b)基因 ,观察其表达产物诱导的机体内产生抗体效价的变化规律。方法　利用分子克隆技术构建重组质粒 ,经脂质体转染与野生型痘苗病毒在Cos- 7细胞内同源重组 ,筛选、纯化、获得重组痘苗病毒vJ1 6env/IFNα - 2b和vJ38gag/IFNα - 2b。免疫小鼠后 ,经间接ELISA分折免疫小鼠血清抗体的OD4 90 值变化。结果　免疫小鼠后体内抗体的OD4 90 值 ,实验组与阴性对照组平均数有显著性差异 (P <0 0 5) ,实验组与阳性对照组之间无显著性差异 (P >0 0 5)。结论　重组痘苗病毒vJ1 6env/IFNα - 2b和vJ38gag/IFNα- 2b免疫小鼠后可诱导机体产生高滴度的抗HIV - 1env、gag与IFNα - 2b巨蛋白抗原的抗体 ,蛋白稀释度与血清抗体OD4 90 值呈负相关     

流感病毒血凝素茎部螺旋区和串联重复M2蛋白胞外区域融合蛋白的免疫效果研究

目的探索含有流感病毒血凝素茎部α螺旋区(HAα)和6个串联重复M2蛋白胞外区域(6M2e)的融合蛋白的表达和制备方法, 并对其在小鼠体内的免疫效果进行评价。方法采用去除高变区的鞭毛蛋白序列, 将HAα和6M2e插入到原高变区位点, 构建重组质粒pET28a-FljBΔD2D3-HAα-6M2e。在大肠埃希菌中诱导表达后进行纯化和鉴定, 并评估其细胞毒性。最后将制备的融合蛋白免疫BALB/c小鼠, 采用ELISA方法检测小鼠血清特异性抗体效价, 实时荧光PCR法检测小鼠IL-2、IL-4、IL-6、IFN-γ、TNF-ɑ的mRNA水平, CCK-8法检测脾细胞的增殖。结果成功构建重组质粒pET28a-FljBΔD2D3-HAα-6M2e, 蛋白表达最适条件为1 mmol/L异丙基-β-D-硫代半乳糖苷(IPTG)37 ℃诱导10 h, 通过镍柱纯化获得高纯度的无毒融合蛋白。免疫小鼠后抗M2e-IgG和抗HAα-IgG的抗体ELISA效价均达到1∶102 400, 且与对照组相比差异有统计学意义(t=0.33, P=0.774;t=7.60, P=0.001)。各类细胞因子的mRNA水平升...     

淋球菌膜蛋白疫苗的研究

目的设计淋球菌膜蛋白疫苗并构建原核表达系统,测定表达蛋白的免疫活性.方法PCR扩增淋球菌膜蛋白(PIA)基因片段,构建重组质粒,重组质粒宿主菌经IPTG诱导,用SDS-PAGE分析PIA的表达情况.淋球菌标准株免疫BALB/c小鼠,体外凝集检测动物血清的免疫效果及ELISA法检测PIA的免疫活性.结果成功构建表达PIA蛋白的重组质粒,SDS-PAGE电泳图上显示1条相对分子量(Mr)约为40KDa的新生条带,能与免疫血清发生特异性结合反应.结论淋球菌膜蛋白疫苗原核表达系统的设计和构建正确,表达蛋白PIA具有免疫活性,为淋病疫苗的开发奠定了基础.     

埃可病毒9型VP1蛋白的原核表达及多克隆抗体制备

目的原核表达并纯化埃可病毒9型(ECHO9)VP1蛋白,免疫兔子制备多克隆抗体,鉴定重组蛋白的免疫活性,为ECHO9血清学检测试剂和疫苗研究提供依据。方法 PCR方法扩增VP1基因,构建原核表达质粒p ET28a-VP1并转化到大肠杆菌(E.coli BL21),诱导表达并纯化VP1重组蛋白,免疫兔子制备抗VP1多克隆抗体,ELISA检测抗VP1抗体效价,Western blot鉴定抗体特异性。病毒中和试验鉴定抗体中和ECHO9病毒的能力。结果 VP1重组蛋白在大肠杆菌BL21中高效表达,制备的抗VP1抗体效价为1∶105。Western blot检测结果显示,抗VP1多克隆抗体可以识别原核表达的VP1蛋白。中和试验显示抗体对ECHO9病毒有中和作用,其效价为1∶10。结论本研究成功原核表达了ECHO9的VP1蛋白并制备出抗VP1多克隆抗体,有助于ECHO9的临床诊断、疫苗开发和分子病毒学研究。     

淋球菌膜蛋白疫苗的研究

目的 :设计淋球菌膜蛋白疫苗并构建原核表达系统 ,测定表达蛋白的免疫活性。方法 :PCR扩增淋球菌膜蛋白( PIA)基因片段 ,构建重组质粒 ,重组质粒宿主菌经 IPTG诱导 ,用 SDS- PAGE分析 PIA的表达情况。淋球菌标准株免疫 BAL B/c小鼠 ,体外凝集检测动物血清的免疫效果及 EL ISA法检测 PIA的免疫活性。结果 :成功构建表达 PIA蛋白的重组质粒 ,SDS-PAGE电泳图上显示 1条相对分子量 ( Mr)约为 4 0 KDa的新生条带 ,能与免疫血清发生特异性结合反应。结论 :淋球菌膜蛋白疫苗原核表达系统的设计和构建正确 ,表达蛋白 PIA具有免疫活性 ,为淋病疫苗的开发奠定了基础     

武汉市美沙酮门诊治疗者丙型肝炎病毒基因分型

目的 探讨武汉市美沙酮门诊治疗者丙型肝炎病毒(HCV)及不同基因型感染状况.方法 用酶标记免疫(ELISA)法检测抗-HCV抗体,在86份抗-HCV抗体阳性的血清标本中,分别提取HCV RNA,通过逆转录巢式聚合酶链反应(RT-nested PCR)扩增C基因的羧基至E1基因的氨基端长度为474 bp的片段,测定其核苷酸序列,与GenBank中已知的HCV序列进行系谱分析,确定HCV基因型.结果 武汉市美沙酮门诊332名治疗者中抗-HCV IgG阳性率为94.3%;其中86份血清的HCV序列通过系谱显示6a型71例,占82.5%;3b 7例,占8.2%;1a 5例,占5.8%;1b 3例,占3.5%.结论 武汉市美沙酮门诊入组的吸毒者HCV感染以6a型为优势株,其次为3b,吸毒者中HCV感染率较高,且基因亚型呈现多样性.     

食源性致病菌六联融合毒素的构建及免疫学特性研究

[目的]构建4种食源性致病菌融合毒素基因及重组表达载体,制备六联融合毒素的血清抗体. [方法]采用柔性Linker序列(G-G-G-G-S)对目的基因进行串联(HblA-VT1B-SEA-VT2B-BoNTaHc-SEB),构建重组表达质粒pET-22b(+)-F6并在E.coli BL21中进行表达,将表达蛋白纯化后免疫豚鼠制备血清抗体,利用ELISA和琼脂扩散试验验证抗体的特异性与敏感性. [结果]成功构建了重组表达质粒pET-22b(+)-F6并在E.coli BL21中成功表达,37℃表达蛋白主要以包涵体形式存在(表达量10.2%),基因序列全长3 384bp,编码1 127个氨基酸,蛋白分子量为127 205,测序结果与设计序列一致性为100%.ELISA和琼脂扩散试验表明,融合毒素F6与4种食源性致病菌有良好的反应原性,与多种非目标菌不反应. [结论]成功构建了多联融合毒素基因的表达质粒及制备了抗血清,为利用融合毒素的方法检测食源性致病菌,进而建立食源性致病菌广谱、快速的检测方法奠定基础.     

基于克隆表达的芳香烃受体系统的二噁(口英)生物检测方法研究

目的 研究人工克隆表达的芳香烃受体核转位蛋白(ARNT)与天然芳香烃受体(AhR)特异性结合及其对制备的多克隆抗体识别的情况,通过两者结合与二噁(口英)(TCDD)的剂量反应关系,探索TCDD生物检测方法.方法 (1)以小鼠肝组织总RNA为模板,通过RT-PCR扩增目的 基因AhR-PAS[periodicity(Per)/Aryl hydrocarbon nuclear translocatar(ARNT)/single-minded(Sim)]端、AhR羧基末端(AhR-C端)、ARNT-PAS端,构建含有目的 基因的pGEX-5X1重组表达质粒,并采用大肠杆菌原核系统进行克隆表达.(2)用上述克隆表达的AhR片段蛋白(AhR-PAS、AhR-C)作为抗原免疫家兔,制备多克隆抗体.(3)从C57BL/6J纯系小鼠肝组织中提取具有结合活性的天然AhR复合物,将天然AhR复合物与结合在谷胱甘肽硫转移酶(GST)上面的融合蛋白GST-ARNT-PAS,分别在0.25、0.50、1.00、2.00 pmol TCDD存在的条件下进行结合,通过亲和吸附和免疫印迹观察所形成的蛋白复合物的量.结果 (1)成功构建含有目的 基因AhR-PAS、AhR-C和ARNT-PAS的重组质粒,并通过大肠杆菌原核系统表达出具有结合活性的目的 蛋白;(2)免疫家兔制得的多克隆抗体AhR-PAS、AhR-C的检测下限分别为5、1 ng;(3)测得该法制备的小鼠肝脏匀浆中总蛋白质的浓度为60.5 mg/ml;在TCDD存在的条件下,克隆得到的融合蛋白GST-ARNT-PAS能够与天然AhR复合物特异性地结合,并测得检测下限为0.25 pmol,约80 Pg TCDD.结论 成功地建立了基于克隆表达的芳香烃受体系统的TCDD生物检测方法,且检测下限达到pg级别.     

鹦鹉热衣原体Mip基因原核表达载体的构建及多克隆抗体的制备

目的克隆鹦鹉热衣原体巨噬细胞感染增强蛋白(Microphage infectivity potentiator,Mip)基因,构建原核重组质粒,诱导表达重组蛋白,并免疫BALB/c小鼠,制备多克隆抗体,为进一步研究其功能奠定了基础。方法提取鹦鹉热衣原体6BC基因组DNA,PCR扩增Mip基因,克隆至p ET-30a(+),构建原核表达载体p ET-30a(+)-Cps Mip。PCR、酶切及测序鉴定后,IPTG诱导p ET-30a(+)-Cps Mip在E.coli BL21中表达目的蛋白。融合蛋白纯化后免疫BALB/c小鼠,ELISA检测小鼠血清中抗Mip抗体的效价。结果 PCR扩增得到大小约为768 bp左右的Mip目的片段;经PCR、酶切及测序鉴定,证明构建的原核重组质粒中插入的片段为Cps Mip基因,测序结果经BLAST分析,与Genbank上登录序列完全一致。经IPTG诱导,重组工程菌表达一相对分子量(Mr)约为34 k D的目的蛋白;ELISA检测免疫小鼠血清效价为1:128 000。结论成功构建了鹦鹉热衣原体Mip基因原核表达载体,并表达了相应可溶性蛋白,制备了高效价的鼠抗Mip多克隆抗体。     

rBCG-HPV16L1-E7疫苗的构建和免疫原性研究

[目的]构建以BCG为载体的rBCG-HPV16L1-E7疫苗,研究rBCG-HPV16L1-E7重组表达体嵌合乳头状瘤病毒样颗粒（VLPs）对小鼠免疫功能的影响,初步评价此疫苗对HPV相关肿瘤（宫颈癌）的预防作用.[方法]电穿孔法将pIJ702-HPV16L1-E7分泌型穿梭表达质粒导入BCG中表达,构成rBCG-HPV16L1-E7疫苗.Western blot检测E7蛋白的表达.采用rBCG-HPV16L1-E7疫苗皮下注射于C57BL/6小鼠,^51Cr释放法体外分析免疫鼠的细胞毒性T淋巴细胞活性（cytotoxic T lymphocyte,CTL）,ELISA法检测免疫鼠血清中E7特异性抗体和细胞因子的表达水平.[结果]Western blot法分析证实,该重组疫苗能特异地表达HPV16 E7蛋白.以rBCG-HPV16L1-E7免疫小鼠后,检测到的细胞因子IL-2、IFNγ及E7抗体的含量明显升高,诱导机体产生特异的抗体反应以及CTL反应.[结论]rBCG-HPV16L1-E7能增强小鼠的细胞和体液免疫反应,可作为HPV16预防性疫苗.     

Hepatitis C virus envelope glycoprotein immunization of rodents elicits cross-reactive neutralizing antibodies

Neutralizing antibody responses elicited during infection generally confer protection from infection. Hepatitis C virus (HCV) encodes two glycoproteins E1 and E2 that are essential for virus entry and are the major target for neutralizing antibodies. To assess whether both glycoproteins are required for the generation of a neutralizing antibody response, rodents were immunized with a series of glycoproteins comprising full length and truncated versions. Guinea pigs immunized with HCV-1 genotype 1a E1E2p7, E1E2 or E2 generated high titer anti-glycoprotein antibody responses that neutralized the infectivity of HCVpp and HCVcc expressing gps of the same genotype as the immunizing antigen. Less potent neutralization of viruses bearing the genotype 2 strain J6 gps was observed. In contrast, immunized mice demonstrated reduced anti-gp antibody responses, consistent with their minimal neutralizing activity. Immunization with E2 alone was sufficient to induce a high titer response that neutralized HCV pseudoparticles (HCVpp) bearing diverse glycoproteins and cell culture grown HCV (HCVcc). The neutralization titer was reduced 3-fold by the presence of lipoproteins in human sera. Cross-competition of the guinea pig anti-E1E2 immune sera with a panel of epitope mapped anti-E2 monoclonal antibodies for binding E2 identified a series of epitopes within the N-terminal domain that may be immunogenic in the immunized rodents. These data demonstrate that recombinant E2 and E1E2 can induce polyclonal antibody responses with cross-reactive neutralizing activity, supporting the future development of prophylactic and therapeutic vaccines.     

New neutralizing antibody epitopes in hepatitis C virus envelope glycoproteins are revealed by dissecting peptide recognition profiles

One of the greatest challenges to HCV vaccine development is the induction of effective immune responses using recombinant proteins or vectors. In order to better understand which vaccine-induced antibodies contribute to neutralization of HCV the quality of polyclonal anti-E1E2 antibody responses in immunized mice and chimpanzees was assessed at the level of epitope recognition using peptide scanning and neutralization of chimeric 1a/2a, 1b/2a and 2a HCVcc after blocking or affinity elution of specific antibodies. Mice and chimpanzees were immunized with genotype 1a (H77) HCV gpE1E2; all samples contained cross-neutralizing antibody against HCVcc. By functionally dissecting the polyclonal immune responses we identified three new regions important for neutralization within E1 (aa264-318) and E2 (aa448-483 and aa496-515) of the HCV glycoproteins, the third of which (aa496-515) is highly conserved (85-95%) amongst genotypes. Antibodies to aa496-515 were isolated by affinity binding and elution from the serum of a vaccinated chimpanzee and found to specifically neutralize chimeric 1a/2a, 1b/2a and 2a HCVcc. IC50 titres (IgG ng/mL) for the aa496-515 eluate were calculated as 142.1, 239.37 and 487.62 against 1a/2a, 1b/2a and 2a HCVcc, respectively. Further analysis demonstrated that although antibody to this new, conserved neutralization epitope is efficiently induced with recombinant proteins in mice and chimpanzees; it is poorly induced during natural infection in patients and chimpanzees (7 out of 68 samples positive) suggesting the epitope is poorly presented to the immune system in the context of the viral particle. These findings have important implications for the development of HCV vaccines and strategies designed to protect against heterologous viruses. The data also suggest that recombinant or synthetic antigens may be more efficient at inducing neutralizing antibodies to certain epitopes and that screening virally infected patients may not be the best approach for finding new cross-reactive epitopes.     

Oral immunization with attenuated Salmonella carrying a co-expression plasmid encoding the core and E2 proteins of hepatitis C virus capable of inducing cellular immune responses and neutralizing antibodies in mice

Hepatitis C virus (HCV) core protein has long been considered an attractive candidate for inclusion in a protective vaccine. However, this protein may hamper the development of systemic immune responses because of its immune suppressive properties. We previously reported that immune responses to HCV core protein could be efficiently induced by attenuated Salmonella carrying the HCV core protein, but not the HCV core DNA vaccine. To optimize the combination of the core protein and envelope protein 2 (E2) into a vaccine formulation to induce cellular immune responses and neutralizing antibodies, we constructed a plasmid containing two expression cassettes. One expression cassette was included to regulate the expression of HCV core protein by an inducible in vivo-activated Salmonella promoter, the other was included to regulate the expression of HCV E2 protein by the cytomegalovirus enhancer/promoter. Oral immunization of BALB/c mice with the attenuated Salmonella strain SL7207 carrying this plasmid efficiently induced HCV core and E2-specific cellular immune responses and antibodies. IgG purified from immunized mice could neutralize the infectivity of HCV pseudoparticles (HCVpp) of both the autologous Con 1 isolate and the heterologous H77 isolate, and cell culture produced HCV (HCVcc) of Con1-JFH1 chimera. These results indicated that this vaccine strategy can effectively deliver core and E2 protein to the immune system and provide a promising approach for the development of prophylactic and therapeutic vaccines against HCV infection.     

DNA immunization of mice and macaques with plasmids encoding hepatitis C virus envelope E2 protein expressed intracellularly and on the cell surface

We analyzed the humoral immune response elicited by hepatitis C virus (HCV) E2 protein expressed in vivo after injection of plasmid DNA into mice and rhesus macaques. Three plasmids were used for immunization: a plasmid containing the entire sequence of the E2 and p7 genes (pE2); a plasmid encoding a truncated form of the E2 protein targeted to the cell surface (pE2surf); a control plasmid (pDisplay) lacking an HCV insert. Each plasmid was injected intramuscularly into 5 mice and intraepidermally (via gene gun) into 5 mice. Immunization was repeated three times at three week intervals. Five macaques were injected intramuscularly (two with pE2, two with pE2surf and one with pDisplay) and immunization was repeated after 8 weeks. All mice immunized via gene gun with pE2 or pE2surf developed anti-E2. The animals immunized with pE2surf developed an earlier and stronger humoral immune response than those immunized with pE2. Only 2 of the mice injected by the intramuscular route, both immunized with pE2surf, developed detectable anti-E2. One of the two macaques immunized with pE2 and both macaques immunized with pE2surf developed anti-E2; the humoral immune response was much stronger in the animals immunized with pE2surf. Our results suggest that presentation of HCV E2 on the cell surface may increase its immunogenicity while preserving its ability to react with antibodies generated during a natural infection.     

A recombinant envelope protein vaccine against West Nile virus

West Nile (WN) virus is a flavivirus that first appeared in North America in 1999. Since then, more than 600 human deaths and 22,000 equine infections have been attributed to the virus in the United States. We expressed a truncated form of WN virus envelope (E) protein in Drosophila S2 cells. This soluble recombinant E protein was recognized by antibodies from naturally infected horses, indicating that it contains native epitopes. Mice and horses produced high-titer antibodies when immunized with recombinant E protein combined with aluminum hydroxide. Immunized mice were resistant to challenge with a lethal viral dose. Sera from immunized horses, administered to naive mice, conferred resistance against a lethal WN viral challenge. In addition, sera of immunized horses neutralized West Nile virus in vitro, as demonstrated by plaque reduction assays. This recombinant form of E protein, combined with aluminum hydroxide, is a candidate vaccine that may protect humans and horses against WN virus infections.     

Immunogenicity of the E1E2 proteins of hepatitis C virus expressed by recombinant adenoviruses

The E1 and E2 proteins of hepatitis C virus (HCV) are believed to be the viral envelope glycoproteins that are major candidate antigens for HCV vaccine development. We reported previously that the replication-competent recombinant adenovirus encoding core-E1-E2 genes of HCV (Ad/HCV) produces serologically reactive E1 and E2 proteins forming a heterodimer in substantial amounts. Here, we examined immunogenicity of the E1E2 proteins copurified from HeLa cells infected with Ad/HCV virus in mice. Furthermore, we constructed a replication-defective recombinant adenovirus encoding the core-E1-E2 genes of HCV (Ad.CMV.HCV) and examined immunogenicity of the virus in mice. The mice immunized intraperitoneally with the copurified E1E2 proteins induced mainly antibodies to E2, but not to E1 by Western blot analysis. The sera of mice immunized with the E1E2 inhibited the binding of E2 protein to the major extracellular loop of human CD81. E2-specific cytotoxic T cells (CTLs), but not antibodies to the E1E2 antigens were induced in the mice intramuscularly immunized with Ad.CMV.HCV virus. When immunized with both Ad.CMV.HCV virus and the E1E2, mice elicited E2-specific CTLs and antibodies to the E1E2 antigens. The results suggest that immunization of Ad.CMV.HCV virus combined with E2 protein is an effective modality to induce humoral as well as cellular immune response to E2 antigen.     

Hepatitis C virus soluble E2 in combination with QuilA and CpG ODN induces neutralizing antibodies in mice

Several studies have emphasized the importance of an early, highly neutralizing antibody response in the clearance of Hepatitis C virus (HCV) infection. The envelope glycoprotein E2 is a major target for HCV neutralizing antibodies. Here, we compared antibody responses in mice immunized with native soluble E2 (sE2) from the H77 1a isolate coupled with different adjuvants or combinations of adjuvants. Adjuvanting sE2 with Freund's, monophosphoryl lipid A (MPL), cytosine phosphorothioate guanine oligodeoxynucleotide (CpG ODN), or alpha-galactosylceramide (αGalCer) derivatives elicited only moderate antibody responses. In contrast, immunizations with sE2 and QuilA elicited exceptionally high anti-E2 antibody titers. Sera from these mice effectively neutralized HCV pseudoparticles (HCVpp) 1a entry. Moreover, the combination of QuilA and CpG ODN further enhanced neutralizing antibody titers wherein cross-neutralization of HCVpp 4 was observed. We conclude that the combination of QuilA and CpG ODN is a promising adjuvant combination that should be further explored for the development of an HCV subunit vaccine. Our work also emphasizes that the ideal combination of adjuvant and immunogen has to be determined empirically.     

Murine neutralizing antibody response and toxicity to synthetic peptides derived from E1 and E2 proteins of hepatitis C virus

Introduction

The highest estimated prevalence of HCV infection has been reported in Egypt, nearly 12% mostly type 4. Currently, a commercial vaccine to protect this high risk population as well as global HCV infected patients is not available.

Objectives

In the present study, we aim at: (1) examining the viral binding capacities of purified monospecific polyclonal murine antibodies raised against genetically conserved viral protein sequences, i.e. synthetic peptides derived from those sequences located within envelope proteins and (2) assessment of immunogenic properties and safety parameters of those peptides individually and in a vaccine format in mice.

Methods

Purified IgG Abs from immunized mice were used in immunocapture RT-PCR experiments to test viral neutralization by Abs raised against each of 4 peptides termed p35 (E1), p36 (E2), p37 (E2) and p38 (E2). Swiss mice were immunized with each of the 3 peptides (p35, p37 and p38) which generated neutralizing antibodies in immunocapture experiments. Antibody responses to corresponding peptides were determined using different routes of administration, different adjuvants, different doses and at different time points post-injection. To explore the dose range for future pharmacological studies, three doses namely 50 ng, 10 μg and 50 μg/25 gm mouse body weight were tested for biochemical and histopathological changes in several organs.

Results

Murine Abs against p35, p37 and p38 but not p36 showed HCV neutralization in immunocapture experiments. Subcutaneous injection of peptides elicited higher responses than i.m. and i.p. Immunization with Multiple Antigenic Peptide (MAP) form or coupled to Al PO4 elicited the highest Ab responses. Peptide doses of 50 ng/25 gm body weight or less were effective and safe, however dose assessment still requires further study. Histopathological changes were observed in animals that received doses ∼1000 times higher than the potential therapeutic dose.

Conclusion

Exploration of humoral immunogenicity, neutralization capacity and safety suggested that the peptides presented herein are candidate vaccine components for further preclinical assessment.     

Induction of protective antibodies against dengue virus by tetravalent DNA immunization of mice with domain III of the envelope protein

Dengue fever is a growing public health concern around the world and despite vaccine development efforts, there are currently no effective dengue vaccines. In the present study we report the induction of protective antibodies against dengue virus by DNA immunization with domain III (DIII) region of the envelope protein (E) in a mouse model. The DIII region of all four dengue virus serotypes were cloned separately into pcDNA 3 plasmid. Protein expression was tested in COS-7 cells. Each plasmid, or a tetravalent combination, were used to immunize BALB/c mice by intramuscular route. Presence of specific antibodies was evaluated by ELISA, and neutralizing antibodies were tested using a cytopathogenic effect (CPE) inhibition assay in BHK-21 cells, as well as in newborn mice challenged intracranially with dengue 2 virus. Mice immunized with individual DIII constructs or the tetravalent formulation developed antibodies against each corresponding dengue serotype. Antibody titers by ELISA were similar for all serotypes and no significant differences were observed when boosters were administered, although antibody responses were dose-dependent. CPE inhibition assays using Den-2 virus showed neutralization titers of 1:10 in mice immunized with individual DIII plasmid or those immunized with the tetravalent formulations. 43% of newborn mice challenged with Den-2 in combination with sera from mice immunized with Den-2 DIII plasmid were protected, whereas sera from mice immunized with the tetravalent formulation conferred 87% protection. Our results suggest that DIII can be used as a tetravalent DNA formulation to induce neutralizing and protective antibodies against dengue virus.     

Immunogenicity of recombinant HBsAg/HCV particles in mice pre-immunised with hepatitis B virus-specific vaccine

Due to their spatial structure virus-like particles (VLPs) generally induce effective immune responses. VLPs derived from the small envelope protein (HBsAg-S) of hepatitis B virus (HBV) comprise the HBV vaccine. Modified HBsAs-S VLPs, carrying the immunodominant hypervariable region (HVR1) of the hepatitis C virus (HCV) envelope protein E2 within the exposed 'a'-determinant region (HBsAg/HVR1-VLPs), elicited HVR1-specific antibodies in mice. A high percentage of the human population is positive for anti-HBsAg antibodies (anti-HBs), either through vaccination or natural infection. We, therefore, determined if pre-existing anti-HBs could influence immunisation with modified VLPs. Mice were immunised with a commercial HBV vaccine, monitored to ensure an anti-HBs response, then immunised with HBsAg/HVR1-VLPs. The resulting anti-HVR1 antibody titre was similar in mice with or without pre-existing anti-HBs. This suggests that HBsAg/HVR1-VLPs induce a primary immune response to HVR1 in anti-HBs positive mice and, hence, they may be used successfully in individuals already immunised with the HBV vaccine.