登革病毒3型病毒样颗粒在酵母体内的表达与鉴定

目的探讨登革病毒3型病毒样颗粒（DENV3-VLPs）的免疫原性。方法用PCR法扩增登革病毒3型prME基因,插入载体pGAPZaA构建重组质粒pGAPZaA-prME-D3,将其转化毕赤酵母X33构建转化子pGAPZaA-prME-D3/X33。对转化子表达上清和细胞裂解液进行SDS-PAGE和Western blotting分析。用蔗糖密度梯度离心纯化表达的DENV3-VLPs并进行鉴定和电镜观察。结果成功构建重组载体pGAPZaA-prME-D3,获得酵母转化子pGAPZaA-prME-D3/X33,并应用毕赤酵母表达了DENV3-VLPs,表达蛋白约50000Mr,电镜观察VLPs直径为20～50nm。结论应用酵母表达系统成功表达了DENV-3VLPs,经鉴定表明其具有免疫反应性,为后续免疫原性研究及四价登革VLPs疫苗的构建奠定了基础。     

柯萨奇病毒A组16型病毒样颗粒免疫原性的初步研究

目的 研究柯萨奇病毒A组16型（Coxsackievirus A16,CA16）病毒样颗粒（Virus-like particles,VLPs）的免疫原性.方法 利用杆状病毒-昆虫细胞表达系统共表达3CD及P1蛋白,制备CA16病毒样颗粒,通过SDS-PAGE及透射电镜等方法对VLPs进行鉴定,以氢氧化铝佐剂免疫ICR小鼠,并对乳鼠经颅腔攻毒.对病毒样颗粒疫苗的免疫原性及保护效果进行评价.结果 将重组CA163CD及P1蛋白的杆状病毒转染SF9细胞,可以产生类似CA16病毒颗粒的大小为27 ～ 30 nm的VLPs.小鼠免疫试验结果显示CA16 VLPs可以刺激产生较高水平的抗CA16病毒的特异性IgG抗体及中和抗体,乳鼠攻毒试验结果显示,母传抗体保护率高达90％.结论 CA16 VLPs可以刺激小鼠产生较高水平的体液免疫反应,并且母传抗体可以保护乳鼠抵御经颅腔的病毒攻击.     

两株登革2型病毒E基因重组质粒免疫BALB/c小鼠产生特异性抗体水平的比较

目的 用含登革2型病毒(Dengue type 2 virus,DEN2)B株和NGC株E基因部分序列pcDNA3.1重组质粒初次和加强免疫BALB/c小鼠,观察免疫小鼠体液免疫应答的差异.方法 用两株含DEN2 E基因部分序列(1～476 bp)的pcDNA3.1重组质粒与含有佐剂的重组质粒共同免疫BALB/c小鼠,初次免疫后第14天、28天分别加强免疫1次,共免疫3次.收集初次免疫后第14、28、42、70和98天外周血标本,间接ELISA法测定小鼠血浆特异性IgM/IgG类抗体水平,细胞病变抑制法检测特异性抗体水平.结果 不同DEN2毒株E基因部分序列的pcDNA3.1重组质粒初次和加强免疫BALB/c小鼠诱导特异性IgM、IgG类抗体的产生存在差异,B株重组质粒加强免疫小鼠后特异性抗体效价水平较高并持续较长时间.结论 DEN2两毒株E基因部分序列重组质粒免疫小鼠后诱生的特异性抗体类别、水平存在差异.     

登革2型病毒43株NS1基因重组质粒DNA的免疫原性及保护作用研究

目的 研究以pcDNA3.1为载体的登革2型病毒43株（D2－43）NS1基因重组DNA的免疫原性及对登革病毒感染所致小鼠神经毒的免疫保护作用。方法 将纯化的pcDNA-NS1重组质粒DNA采用肌肉多点注射途径免疫3周龄BALB／c小鼠，剂量为每只100μg/次，检测了免疫鼠血清抗体滴度及特异性细胞毒作用。并以D2－43病毒脑内攻击6周龄BALB/c小鼠产生的神经毒症状为实验模型，对pcDNA-NS1的免疫保护作用进行了初步探讨。结果 用间接ELISA测得pcDNA-NS1免疫后抗体滴度为1：800，在补体存在下，对D2－43病毒感染的BHK－21细胞特异性杀伤率可达到61．6％。由免疫的BALB／c小鼠脾制备的效应细胞在体外可特异性地杀伤D2－43感染的P－815细胞（H－2^d)。当效靶比（E／T）为20：1时，pcDNA-NS1质粒免疫后的特异性CTL杀伤百分率为22．6％。将100 LD50的D2－43病毒经脑内攻击BALB／c小鼠，结果表明免疫pcDNA-NS1组小鼠存活率最高（90．9％）；与免疫pcDNA3.1对照组比较，P值＜0．05。结论 pcDNA-NS1质粒免疫BALB／c小鼠不仅可诱导体液免疫，还可诱导特异性细胞免疫。初步结果还显示，用含NS1基因的重组质粒DNA免疫的小鼠能免受致死剂量登革病毒的攻击，为登革热新型疫苗的研究奠定了基础。     

登革3型病毒prM-E和NS1多基因重组质粒DNA免疫原性增强效果观察

目的　观察登革 3型病毒的prM E和NS1基因重组质粒DNA混合免疫对免疫原性的增强作用 ,为登革DNA疫苗混合免疫提供实验依据。方法　将登革 3型病毒的prM E和NS1基因重组质粒DNA分别混合及单独免疫BALB/c小鼠 ,采用中和试验及MTT法检测免疫小鼠血清中和抗体及脾细胞特异性CTL(cytotoxicT lymphocytes)杀伤率。结果　混合重组质粒DNA免疫组与单一prM E基因重组质粒DNA免疫组均在末次免疫后第 14天检测到中和抗体 ,在第 33天达到高峰 ,为 1∶32。在末次免疫后第 4 1天 ,当效靶比为 4 0∶1时 ,混合重组质粒DNA免疫组的特异性CTL杀伤率为 15 % ,而 2个单质粒DNA组分别为 10 .9%和 12 .4 %。结论　重组质粒DNA混合免疫可同时诱发小鼠产生体液免疫和细胞免疫 ,而且细胞免疫应答具有一定的增强作用 ,但没有出现特异性CTL杀伤率的协同增强效果。     

登革2型病毒ZS01/01株E蛋白在真核细胞中的分泌表达研究

目的 对登革2型病毒(DENV-2)ZS01/01株E蛋白在哺乳动物细胞及昆虫细胞中的分泌表达进行研究.方法 RT-PCR扩增DENV-2 prM/E基因,通过融合PCR在prM基因前添加来自乙型脑炎病毒的信号肽序列,并将E基因羧基末端20%区域缺失或替换为乙型脑炎病毒SA14-14-2株E基因相应序列,将上述基因元件分别克隆入哺乳动物细胞表达载体pcDNA5/FRT及昆虫细胞表达载体pAcUW51-M中,将重组质粒转染293T细胞或S19细胞,利用间接免疫荧光(Immunofluoreseence assay,IFA)及Western Blot检测E蛋白的表达与分泌.结果 各重组质粒分别转染293T细胞或Sf9细胞后,E蛋白在细胞内均有效表达,而仅有携带乙脑信号肽且缺失或替换E基因羧基末端20%区域的重组质粒转染293T细胞后,上清中可检测到明显的E蛋白分泌.结论 信号肽及E基因羧基末端20%区域对登革病毒E蛋白的分泌至关重要,宿主细胞对其亦有一定影响.     

登革2型病毒ZS01/01株E蛋白在真核细胞中的分泌表达研究

目的 对登革2型病毒(DENV-2)ZS01/01株E蛋白在哺乳动物细胞及昆虫细胞中的分泌表达进行研究.方法 RT-PCR扩增DENV-2 prM/E基因,通过融合PCR在prM基因前添加来自乙型脑炎病毒的信号肽序列,并将E基因羧基末端20%区域缺失或替换为乙型脑炎病毒SA14-14-2株E基因相应序列,将上述基因元件分别克隆入哺乳动物细胞表达载体pcDNA5/FRT及昆虫细胞表达载体pAcUW51-M中,将重组质粒转染293T细胞或S19细胞,利用间接免疫荧光(Immunofluoreseence assay,IFA)及Western Blot检测E蛋白的表达与分泌.结果 各重组质粒分别转染293T细胞或Sf9细胞后,E蛋白在细胞内均有效表达,而仅有携带乙脑信号肽且缺失或替换E基因羧基末端20%区域的重组质粒转染293T细胞后,上清中可检测到明显的E蛋白分泌.结论 信号肽及E基因羧基末端20%区域对登革病毒E蛋白的分泌至关重要,宿主细胞对其亦有一定影响.     

登革病毒1、2型单、双价病毒样颗粒的免疫原性研究

目的初步研究登革病毒1、2型单、双价病毒样颗粒（VLP）的免疫原性。方法表达纯化各型VLP。用纯化好的VLP免疫BALB／c小鼠,将BALB／c小鼠随机分PBS组、灭活DENV1、灭活DENV2、纯化VLP1、纯化VLP2、纯化VLP1＋2组,以灭活病毒为阳性对照,PBS为阴性对照。ELISA法检测小鼠血清抗vLP抗体效价以及血清IFN-1、TNF-α细胞因子水平,流式细胞术检测小鼠脾细胞CD4＋细胞和CD8＋细胞数。结果登革病毒1、2型单、双价VLP均能刺激免疫小鼠产生一定程度的抗血清效价,VLP1的抗体水平较VLP2的低,双价VLP组针对DENV2抗原的抗体水平上升明显,是单价VLP2的2-3倍;攻毒后。灭活DENV1和VLP2可以产生高水平的IFN-1,分别为60和35pg／ml,双价VLP组的较低;VLV2组的TNF-α一直保持较高水平,双价vLP组中攻DENV2组的TNF咀水平较DENVl组高;三次免疫后,各实验组较之PBS组CD4＋细胞的比例都有下降,而CD8＋细胞变化不大,除灭活DENV1组有增加,其余各组都有减少。结论无论单、双价VLP均能刺激小鼠产生一定程度的体液免疫和细胞免疫反应,联合免疫有一定程度的协同性。     

呼吸道合胞病毒样颗粒疫苗制备及免疫效果研究

目的利用昆虫表达系统表达以流感病毒基质蛋白M1为骨架制备的嵌合呼吸道合胞病毒(RSV)融合蛋白F和表面糖蛋白G蛋白的呼吸道合胞病毒样颗粒(RSV-F/G VLPs)疫苗候选株,并滴鼻免疫Balb/c小鼠,评价其免疫原性与免疫保护性。方法通过基因重组技术制备以流感基质蛋白M1为骨架,并嵌合RSV F/G蛋白的RSV-F/G VLPs,经超滤浓缩、蔗糖密度梯度离心纯化VLP,滴鼻免疫Balb/c小鼠,检测血清抗体IgG、IgG1、IgG2a,黏膜sIgA效价以及细胞因子IL-4、INF-γ等,评价候选疫苗的免疫原性;二免后2周RSV A2株攻毒,通过检测小鼠体质量变化,肺病毒载量及肺病理切片来评价候选疫苗的免疫保护性。结果成功制备了RSV-F VLPs、RSV-G VLPs疫苗抗原,动物实验结果证实,候选疫苗株RSV-F/G VLPs可刺激机体产生特异性Th1型细胞免疫及黏膜免疫;攻毒实验结果表明候选疫苗株RSV-F/G VLPs针对RSV A2株的攻击可以产生一定的保护效果。结论成功制备了RSV-F VLPs、RSV-G VLPs候选疫苗抗原,并通过动物实验证明RSV-F/G VLPs具有良好的免疫原性和免疫保护性,为发展新型RSV疫苗提供实验依据。     

我国登革2型／4型病毒株嵌合E基因免疫原性的研究

目的 构建含有我国登革2型／4型病毒株嵌合E基因片段的真核表达质粒,观察重组质粒DNA的免疫原性,为登革多价疫苗的研究提供依据。方法 首先将包含我国登革2型病毒43株E蛋白Ⅰ/Ⅱ抗原区和4型病毒B5株E蛋白Ⅲ抗原区的嵌合E基因片段克隆至真核表达载体pcDNA3.1中,通过测定确定嵌合基因序列的正确性。然后将重组质粒以肌肉注射途径,免疫Balb/C小鼠。通过间接免疫荧光法对采集的鼠血清中的病毒特异抗体进行检测。结果 构建的含有我国登革2型／4型病毒株嵌合E基因的真核表达质粒pcDNA-D2/4,经序列测定表明,导入的嵌合E基因片段的序列是正确的。将重组质粒DNA免疫小鼠,在初次免疫后的第3周,可同时检测到针对登革2型和4型病毒的特异荧光。结论 所构建的含有不同血清型的我国登革病毒株嵌合E基因片段的真核重组质粒,可诱导小鼠同时产生针对两个血清型病毒的特异抗体,该研究为新型登革多价疫苗的研制提供了依据。     

Immunogenicity of recombinant human bocavirus‐1,2 VP2 gene virus‐like particles in mice

Human bocavirus (HBoV), a recently identified pathogen with a worldwide distribution is closely related to paediatric acute respiratory infection and gastroenteritis. The present study was performed to evaluate the immunogenicity of HBoV1 and HBoV2 virus‐like particles (VLPs) as vaccine candidates in mice. Both HBoV1 and HBoV2 VLPs were expressed in the bacmid virus–SF9 cell system. Mice were inoculated three times at 3‐week intervals with HBoV VLPs at one dose intramuscular (i.m.) or intradermal (i.d.) with or without the addition of the alum adjuvant. ELISA was used to detected antibody, and ELISPOT was used to test cellular immune responses. HBoV‐specific IgG antibodies were induced and alum adjuvant improved the antibody titres and avidity, while the inoculation pathway had no influence. T helper type 1/ type 2 immune responses were balanced induced by HBoV1 VLPs but not HBoV2 VLPs. Serum IgG antibody cross‐reactivity rates of the two subtypes were similar, but cross‐reactions of HBoV1 immunization groups were higher. The single i.m. group had more interferon‐γ‐secreting splenocytes. These data indicate that HBoV VP2 VLPs have good immunogenicity with induction of strong humoral and cellular immune responses, and they may be potential candidate vaccines for HBoV infection.     

Human immunodeficiency virus-like particles activate multiple types of immune cells

The rapid spread of human immunodeficiency virus (HIV) worldwide makes it a high priority to develop an effective vaccine. Since live attenuated or inactivated HIV is not likely to be approved as a vaccine due to safety concerns, HIV virus like particles (VLPs) offer an attractive alternative because they are safe due to the lack of a viral genome. Although HIV VLPs have been shown to induce humoral and cellular immune responses, it is important to understand the mechanisms by which they induce such responses and to improve their immunogenicity. We generated HIV VLPs, and VLPs containing Flt3 ligand (FL), a dendritic cell growth factor, to target VLPs to dendritic cells, and investigated the roles of these VLPs in the initiation of adaptive immune responses in vitro and in vivo. We found that HIV-1 VLPs induced maturation of dendritic cells and monocyte/macrophage populations in vitro and in vivo, with enhanced expression of maturation markers and cytokines. Dendritic cells pulsed with VLPs induced activation of splenocytes resulting in increased production of cytokines. VLPs containing FL were found to increase dendritic cells and monocyte/macrophage populations in the spleen when administered to mice. Administration of VLPs induced acute activation of multiple types of cells including T and B cells as indicated by enhanced expression of the early activation marker CD69 and down-regulation of the homing receptor CD62L. VLPs containing FL were an effective form of antigen in activating immune cells via dendritic cells, and immunization with HIV VLPs containing FL resulted in enhanced T helper type 2-like immune responses.     

Ebola virus-like particles produced in insect cells exhibit dendritic cell stimulating activity and induce neutralizing antibodies

Recombinant baculoviruses (rBV) expressing Ebola virus VP40 (rBV-VP40) or GP (rBV-GP) proteins were generated. Infection of Sf9 insect cells by rBV-VP40 led to assembly and budding of filamentous particles from the cell surface as shown by electron microscopy. Ebola virus-like particles (VLPs) were produced by coinfection of Sf9 cells with rBV-VP40 and rBV-GP, and incorporation of Ebola GP into VLPs was demonstrated by SDS-PAGE and Western blot analysis. Recombinant baculovirus infection of insect cells yielded high levels of VLPs, which were shown to stimulate cytokine secretion from human dendritic cells similar to VLPs produced in mammalian cells. The immunogenicity of Ebola VLPs produced in insect cells was evaluated by immunization of mice. Analysis of antibody responses showed that most of the GP-specific antibodies were of the IgG2a subtype, while no significant level of IgG1 subtype antibodies specific for GP was induced, indicating the induction of a Th1-biased immune response. Furthermore, sera from Ebola VLP immunized mice were able to block infection by Ebola GP pseudotyped HIV virus in a single round infection assay, indicating that a neutralizing antibody against the Ebola GP protein was induced. These results show that production of Ebola VLPs in insect cells using recombinant baculoviruses represents a promising approach for vaccine development against Ebola virus infection.     

Immune responses against severe acute respiratory syndrome coronavirus induced by virus-like particles in mice

Virus-like particles (VLPs) represent a promising vaccine against severe acute respiratory syndrome coronavirus (SARS CoV). In this study, recombinant baculovirus vAcS and vAcME were constructed to express the S protein and the M and E proteins of SARS CoV, respectively. Electron microscope analysis demonstrated the formation of VLPs in vAcME and vAcS coinfected insect cells. Mice immunized four times with VLPs developed high antibody titres against SARS CoV. In addition, VLPs elicited cell-mediated immunity as demonstrated by enhanced interferon-gamma and interleukin-4 production. VLPs also conferred protective immunity against the infection of Spike protein pseudotyped murine leukaemia virus. Our findings demonstrate that SARS CoV VLPs are immunogenic and can elicit strong SARS CoV-specific humoral and cellular immune responses in mice. This is the first study describing the immunogenicity of SARS CoV VLPs, providing valuable data for developing a protective vaccine against SARS CoV infection.     

Murine immune responses to liver-stage antigen 1 protein FMP011, a malaria vaccine candidate, delivered with adjuvant AS01B or AS02A

Liver-stage antigen 1 (LSA1) is expressed by Plasmodium falciparum only during the intrahepatic cell stage of the parasite's development. Immunoepidemiological studies in regions where malaria is endemic suggested an association between the level of LSA1-specific humoral and cell-mediated immune responses and susceptibility to clinical malaria. A recombinant LSA1 protein, FMP011, has been manufactured as a preerythrocytic vaccine to induce an immune response that would have the effect of controlling parasitemia and disease in humans. To evaluate the immunogenicity of FMP011, we analyzed the immune response of three inbred strains of mice to antigen immunization using two different adjuvant formulations, AS01B and AS02A. We report here the ability of BALB/c and A/J mice, but not C57BL/6J mice, to mount FMP011-specific humoral (antibody titer) and cellular (gamma interferon [IFN-gamma] production) responses following immunization with FMP011 formulated in AS01B or AS02A. Immunization of BALB/c and A/J mice with FMP011/AS01B induced more antigen-specific IFN-gamma-producing splenocytes than immunization with FMP011/AS02A. A slightly higher titer of antibody was induced using AS02A than AS01B in both strains. C57BL/6J mice did not respond with any detectable FMP011-specific IFN-gamma splenocytes or antibody when immunized with FMP011 in AS01B or AS02A. Intracellular staining of cells isolated from FMP011/AS01B-immunized BALB/c mice indicated that CD4(+) cells, but not CD8(+) cells, were the main IFN-gamma-producing splenocyte. However, inclusion of blocking anti-CD4(+) antibody during the in vitro restimulation ELISpot analysis failed to completely abolish IFN-gamma production, indicating that while CD4(+) T cells were the major source of IFN-gamma, other cell types also were involved.     

Dynamics of cellular immune responses in the acute phase of dengue virus infection

In this study, we examined the dynamics of cellular immune responses in the acute phase of dengue virus (DENV) infection in a marmoset model. Here, we found that DENV infection in marmosets greatly induced responses of CD4/CD8 central memory T and NKT cells. Interestingly, the strength of the immune response was greater in animals infected with a dengue fever strain than in those infected with a dengue hemorrhagic fever strain of DENV. In contrast, when animals were re-challenged with the same DENV strain used for primary infection, the neutralizing antibody induced appeared to play a critical role in sterilizing inhibition against viral replication, resulting in strong but delayed responses of CD4/CD8 central memory T and NKT cells. The results in this study may help to better understand the dynamics of cellular and humoral immune responses in the control of DENV infection.     

Enhancement of mucosal immune responses by chimeric influenza HA/SHIV virus-like particles

To enhance mucosal immune responses using simian/human immunodeficiency virus-like particles (SHIV VLPs), we have produced novel phenotypically mixed chimeric influenza HA/SHIV VLPs and used them to immunize C57BL/6J mice intranasally. Antibody and cytotoxic T-cell (CTL) responses as well as cytokine production in both systemic and mucosal sites were compared after immunization with SHIV VLPs or chimeric HA/SHIV VLPs. By using enzyme-linked immunosorbent assay (ELISA), the levels of serum IgG and mucosal IgA to the HIV envelope protein (Env) were found to be highest in the group immunized with chimeric HA/SHIV VLPs. Furthermore, the highest titer of serum neutralizing antibody against HIV Env was found with the group immunized with chimeric HA/SHIV VLPs. Analysis of the IgG1/IgG2a ratio indicated that a T(H)1-oriented immune response resulted from these VLP immunizations. HA/SHIV VLP-immunized mice also showed significantly higher CTL responses than those observed in SHIV VLP-immunized mice. Moreover, a MHC class I restricted T-cell activation ELISPOT assay showed a mixed type of T(H)1/T(H)2 cytokines in the HA/SHIV VLP-immunized mice, indicating that the chimeric VLPs can enhance both humoral and cellular immune responses to the HIV Env protein at multiple mucosal and systemic sites. The results indicate that incorporation of influenza HA into heterotypic VLPs may be highly effective for targeting vaccines to mucosal surfaces.     

Enhancement of mucosal immune responses by chimeric influenza HA/SHIV virus-like particles

To enhance mucosal immune responses using simian-human immunodeficiency virus-like particles (SHIV VLPs) as a mucosal HIV vaccine, we have produced phenotypically mixed, chimeric influenza HA/SHIV 89.6 VLPs and used them to immunize C57B/6J mice intranasally. Systemic and mucosal antibody responses, as well as cytotoxic T cell (CTL) responses, were compared in groups immunized with SHIV 89.6 VLPs or HA/SHIV 89.6 VLPs. Intranasal immunizations were given using VLPs either with or without the addition of the mucosal adjuvant cholera toxin. Total serum IgG, IgG1 and IgG2a, and IgA in saliva, vaginal lavage, lung wash, and fecal extracts were evaluated by enzyme-linked immunosorbent assay (ELISA). The level of serum IgG production to HIV Env was highest in the group immunized with chimeric HA/SHIV 89.6 VLPs. Similarly, mucosal IgA production was also enhanced in the mucosal HA/SHIV 89.6 VLP-immunized group. Analysis of the IgG1/IgG2a ratio indicated that a Th1-oriented immune response resulted from these VLP immunizations. High levels of serum IgG and mucosal IgA against influenza virus were also detected in mice immunized with HA/SHIV VLPs. HA/SHIV 89.6 VLP-immunized mice also showed significantly higher CTL responses than those observed in SHIV 89.6 VLP-immunized mice. Furthermore, a Major Histocompatibility Complex (MHC)-class-I-restricted T cell activation ELISPOT assay showed elevated interferon-gamma, interleukin-2, and interleukin-12 production in HA/SHIV 89.6 VLP-immunized mice, indicating that phenotypically mixed HA/SHIV 89.6 VLPs can enhance both humoral and cellular immune responses at multiple mucosal sites. Therefore, chimeric HA-containing VLPs represent a potential approach for mucosal immunization for prevention of HIV infection.