A novel inactivated enterovirus 71 vaccine can elicit cross-protective immunity against coxsackievirus A16 in mice

Hand, foot, and mouth disease (HFMD) is a highly contagious disease that mainly affects infants and children. Enterovirus 71 (EV71) and coxsackievirus A16 (CA16) are the major pathogens of HFMD. Two EV71 vaccines were recently licensed in China and the administration of the EV71 vaccines is believed to significantly reduce the number of HFMD-related severe or fatal cases. However, a monovalent EV71 vaccine cannot cross-protect against CA16 infection, this may result in that it cannot effectively control the overall HFMD epidemic. In this study, a chimeric EV71, whose VP1/210–225 epitope was replaced by that of CA16, was constructed using a reverse genetics technique to produce a candidate EV71/CA16 bivalent vaccine strain. The chimeric EV71 was infectious and showed similar growth characteristics as its parental strain. The replacement of the VP1/210–225 epitope did not significantly affect the antigenicity and immunogenicity of EV71. More importantly, the chimeric EV71 could induce protective immunity against both EV71 and CA16, and protect neonatal mice against either EV71 or CA16 lethal infections, the chimeric EV71 constructed in this study was shown to be a feasible and promising candidate bivalent vaccine against both EV71 and CA16. The construction of a chimeric enterovirus also provides an alternative platform for broad-spectrum HFMD vaccines development.     

Active immunization with a Coxsackievirus A16 experimental inactivated vaccine induces neutralizing antibodies and protects mice against lethal infection

Coxsackievirus A16 (CA16) is one of the main pathogens that cause hand, foot and mouth disease, which frequently occurs in young children. A small percentage of patients infected with CA16 may suffer from severe neurological complications that could also lead to death. Recent epidemiological data shows the increase in both the total number and the incidence rate of severe CA16-associated cases in China, indicating that CA16 should be targeted for vaccine development. In this article, we report the immunogenicity and protective efficacy of experimental inactivated CA16 vaccines in mice. We show that immunization with β-propiolactone-inactivated whole-virus vaccines derived from two CA16 clinical isolates were able to induce CA16-specific antibody and IFN-secreting T-cell responses in mice. The resulting anti-CA16 mouse sera neutralized both homologous and heterologous CA16 clinical isolates, as well as a mouse-adapted strain called CA16-MAV, which is capable of infecting 14-day-old mice. Passive transfer of anti-CA16 neutralizing sera partially protected neonatal mice from lethal challenge by a clinical isolate CA16-G08. More significantly, active immunization of mice with the inactivated vaccines conferred complete protection against lethal infection with CA16-MAV. Collectively, these results provide a solid foundation for further development of inactivated whole-virus CA16 vaccines for human use.     

A virus-like particle based bivalent vaccine confers dual protection against enterovirus 71 and coxsackievirus A16 infections in mice

Enterovirus 71(EV71) and coxsackievirus A16 (CA16) are responsible for hand, foot and mouth disease which has been prevalent in Asia-Pacific regions, causing significant morbidity and mortality in young children. Co-circulation of and co-infection by both viruses underscores the importance and urgency of developing vaccines against both viruses simultaneously. Here we report the immunogenicity and protective efficacy of a bivalent combination vaccine comprised of EV71 and CA16 virus-like particles (VLPs). We show that monovalent EV71- or CA16-VLPs-elicited serum antibodies exhibited potent neutralization effect on the homotypic virus but little or no effect on the heterotypic one, whereas the antisera against the bivalent vaccine formulation were able to efficiently neutralize both EV71 and CA16, indicating there is no immunological interference between the two antigens with respect to their ability to induce virus-specific neutralizing antibodies. Passive immunization with monovalent VLP vaccines protected mice against a homotypic virus challenge but not heterotypic infection. Surprisingly, antibody-dependent enhancement (ADE) of disease was observed in mice passively transferred with mono-specific anti-CA16 VLP sera and subsequently challenged with EV71. In contrast, the bivalent VLP vaccine conferred full protection against lethal challenge by either EV71 or CA16, thus eliminating the potential of ADE. Taken together, our results demonstrate for the first time that the bivalent VLP approach represents a safe and efficacious vaccine strategy for both EV71 and CA16.     

A combination vaccine comprising of inactivated enterovirus 71 and coxsackievirus A16 elicits balanced protective immunity against both viruses

Enterovirus 71 (EV71) and coxsackievirus A16 (CA16) are the two major causative agents of hand, foot and mouth disease (HFMD), which is an infectious disease frequently occurring in children. A bivalent vaccine against both EV71 and CA16 is highly desirable. In the present study, we compare monovalent inactivated EV71, monovalent inactivated CA16, and a combination vaccine candidate comprising of both inactivated EV71 and CA16, for their immunogenicity and in vivo protective efficacy. The two monovalent vaccines were found to elicit serum antibodies that potently neutralized the homologous virus but had no or weak neutralization activity against the heterologous one; in contrast, the bivalent vaccine immunized sera efficiently neutralized both EV71 and CA16. More importantly, passive immunization with the bivalent vaccine protected mice against either EV71 or CA16 lethal infections, whereas the monovalent vaccines only prevented the homologous but not the heterologous challenges. Together, our results demonstrate that the experimental bivalent vaccine comprising of inactivated EV71 and CA16 induces a balanced protective immunity against both EV71 and CA16, and thus provide proof-of-concept for further development of multivalent vaccines for broad protection against HFMD.     

Chimeric enterovirus 71 virus-like particle displaying conserved coxsackievirus A16 epitopes elicits potent immune responses and protects mice against lethal EV71 and CA16 infection

Hand-foot-and-mouth disease (HFMD) is an infectious disease of infants and young children frequently caused by the enterovirus A species, mainly enterovirus 71 (EV71) and coxsackievirus A16 (CA16). In this study, we prepared the EV71 virus-like particle (EV71-VLP) and its chimeras using recombinant baculovirus (Bac-P1-3CD) co-expressing EV71 P1 (under polyhedrin promoter) and 3CD (under CMV-IE promoter) proteins in Sf9 cells. EV71-VLP chimera ChiEV71(1E)-VLP or ChiEV71(4E)-VLP displayed single CA16 PEP71 epitope in VP1 or four conserved CA16 neutralizing epitopes (PEP71 in VP1, aa136-150 in VP2, aa176-190 in VP3 and aa48-62 in VP4) by substitution of the corresponding regions of EV71 structure proteins, respectively. In mice, EV71-VLP and its chimeras elicited similar EV71-specific IgG and neutralizing antibody (NAb) titers compared to inactivated EV71. Expectedly, vaccination of ChiEV71(1E)-VLP or ChiEV71(4E)-VLP resulted in significantly increased CA16-specific IgG and NAb production and improved cross-protection against CA16 infection compared to EV71-VLP. Interestingly, the VLPs induced potent cellular immune responses and significantly decreased Th2 type (IL-4 and IL-10) cytokines secretion in the splenocytes of immunized mice compared to inactivated EV71 or inactivated CA16. Neonatal mice born to dams immunized with the chimeric VLPs or neonatal mice passively transferred with sera of immunized mice were completely protected from lethal EV71 challenge and partially protected from lethal CA16 infection. Our study provides a novel bivalent or multivalent vaccine strategy to prevent EV71 and related-enterovirus infections.     

2015年昆明市柯萨奇病毒A16型VP1区基因特征分析

目的 研究昆明市2015-2016年手足口病患儿肠道病毒分子流行病学及探讨柯萨奇病毒A组16型（coxsackievirus A16,CVA16）VP1基因遗传变异与其时间和空间分布模式的相关性。方法 采集患儿的咽拭子和肛拭子样本,采用逆转录聚合酶链式反应分子鉴定法分别扩增肠道病毒71型和CVA16的VP1基因全长,随机选取2015年9份CVA16阳性样本进行测序并与数据库参考株构建系统进化树。对不同年份来源的CVA16病毒株间遗传距离与分离年份时间进行相关性和回归分析,并分析不同地理群体间的遗传距离与地理距离的相关性（Mantel检测）。结果 采样年度中大多数患儿为CVA16感染（咽拭子和肛拭子检出率分别为29.41%和15.69%）,其与肠道病毒71型感染的比率分别为2.5 ∶1和2.0 ∶1。VP1基因系统进化分析显示9株CVA16昆明分离株均属于B基因型B1b亚型,且进一步划分成两个亚簇;种系进化及统计学分析显示VP1基因变异与时间推移和地理距离均具有正相关关系（均有P<0.05）。结论 2015年昆明市9株CVA16分离株为新生成的变异毒株,提示CVA16在昆明存在一定的地域流行特点。     

A virus-like particle vaccine for coxsackievirus A16 potently elicits neutralizing antibodies that protect mice against lethal challenge

Coxsackievirus A16 (CVA16) is one of the main causative agents of hand, foot and mouth disease (HFMD), which has been prevalent in the Asia-Pacific region over the last several years. However, no vaccine is yet available to prevent HFMD. Here we report the development of a virus-like particle (VLP) based experimental CVA16 vaccine. CVA16 VLPs were produced in insect cells by co-expression of the P1 and 3CD proteins of CVA16 using recombinant baculoviruses. Biochemical and biophysical analyses showed that CVA16 VLPs consisted of processed VP0, VP1 and VP3, and were present as ∼30 nm spherical particles. Immunization with VLPs potently elicited CVA16-specific serum antibody responses in mice. Anti-VLP sera strongly neutralized in vitro both the homologous and heterologous strains of CVA16. More importantly, passive immunization with anti-VLP sera conferred protection against lethal CVA16 challenge in neonate mice, indicating a humoral mechanism of protection. Collectively, our results represent a successful first step toward the development of a safe and effective vaccine against CVA16 infection.     

微量细胞病变法检测健康人群EV71和CVA16中和抗体水平

目的了解深圳市福田区健康人群中肠道病毒71型(EV71)和柯萨奇A16型(CVA16)隐性感染情况。方法应用微量细胞病变法,对2011年和2012年一般人群流感抗体水平调查采集的471份血清标本进行EV71和CVA16中和抗体检测,并对检测结果进行统计学分析。结果 471份健康人群血清中EV71和CVA16中和抗体阳性率分别为25.50%和33.10%;EV71抗体由0～岁组的7.14%上升至15～岁组的42.65%(χ2=42.12,P<0.01),上升5.97倍,抗体几何平均滴度(GMT)呈缓慢上升趋势;CVA16抗体由0～岁组的9.18%上升至5～岁组的58.73%(χ2=61.87,P<0.01),上升6.39倍,抗体GMT呈波峰状;各年龄组两种抗体混合感染阳性率为11.25%(χ2=64.95,P<0.01)。结论本地区健康人群中存在肠道病毒隐性感染,各年龄组CVA16抗体阳性率均高于EV71;5～25年龄人群EV71和CVA16中和抗体阳性率、GMT和混合感染情况均高于其他年龄组,应加强5～25年龄人群的流行病学监测。     

Inactivated coxsackievirus A10 experimental vaccines protect mice against lethal viral challenge

Coxsackievirus A10 (CVA10) has become one of the major causative agents of hand, foot and mouth disease (HFMD). It is now recognized that CVA10 should be targeted for vaccine development. We report here that β-propiolactone inactivated whole-virus based CVA10 vaccines can elicit protective immunity in mice. We prepared two inactivated CVA10 experimental vaccines derived from the prototype strain CVA10/Kowalik and from a clinical isolate CVA10/S0148b, respectively. Immunization with the experimental vaccines elicited CVA10-specific serum antibodies in mice. The antisera from vaccinated mice could potently neutralize in vitro infection with either homologous or heterologous CVA10 strains. Importantly, passive transfer of the anti-CVA10 sera protected recipient mice against CVA10/Kowalik or CVA10/S0148b infections. Moreover, active immunization with the inactivated vaccines also conferred protection against homologous and heterologous infections in mice. Collectively, our results demonstrate the proof-of-concept for inactivated whole-virus based CVA10 vaccines.     

Hepatitis B virus core particles containing multiple epitopes confer protection against enterovirus 71 and coxsackievirus A16 infection in mice

Human enterovirus 71 (EV71) and coxsackievirus A16 (CA16) are the two major causative agents of hand-foot-and-mouth disease (HFMD). To investigate novel combined vaccines to prevent EV71 and CA16 infection, we constructed chimeric virus-like particles (tHBc/SPA or tHBc/SP VLPs) displaying conserved epitopes of EV71 (aa 208–222 of VP1 and aa 248–263 of VP2) and CA16 (aa271-285 of VP1) using a truncated hepatitis B virus core carrier (tHBc). Immunization with the chimeric VLPs induced epitope- or virus-specific IgG and neutralization antibodies against EV71 and CA16 in the mice. Compared with inactivated EV71, the chimeric VLPs induced significantly increased Th1 cytokine (IFN-γ, IL-2) production and decreased Th2 cytokine (IL-4, IL-10) responses. Neonatal mice born to dams immunized with the recombinant particles were completely protected from lethal EV71 and partially protected from CA16 infection. Co-expression of the conserved human MHC class I CD4+ T cell epitope (aa248-263 of VP2) did not improve the antiviral immunity of the chimeric VLP vaccine in mice. Our results demonstrate that experimental combination vaccines comprised of EV71 and CA16 epitopes induce both humoral and cellular immune responses and therefore support further preclinical and clinical development of a bivalent VLP vaccine targeting both CA16 and EV71.     

肠道病毒71型和柯萨奇病毒A16型细胞受体的研究进展

近几年手足口病在亚太地区的流行大幅上升并伴随严重的中枢神经系统并发症,而针对其主要致病原肠道病毒71型和柯萨奇病毒A16型现在还缺乏有效的预防疫苗和抗病毒制剂.确定它们的特异性细胞受体对于进一步阐明病毒与宿主细胞早期互相作用的分子机制及其致病机制至关重要.过去一年中,P-选择素糖蛋白配体-1、B类清道夫受体Ⅱ和唾液酸化...     

盐城地区柯萨奇病毒A组16型分离株VP1区基因分子生物信息学分析

目的 分析盐城地区柯萨奇病毒A组16型(coxsackievirus A16,CVA16)VP1区蛋白结构和B细胞表位。方法 基于盐城地区2017年CVA16分离株J837 VP1区蛋白序列,采用分子生物信息学软件预测蛋白质理化特性、亲水性、二级结构和抗原表位等。结果 盐城地区CVA16分离株VP1区编码蛋白为亲水蛋白,无信号肽,有1个跨膜螺旋区域,二级结构以无规则卷曲为主,存在7个潜在的B细胞抗原表位。结论 本文成功预测了CVA16分离株VP1区蛋白二级结构和B细胞优势表位,为CVA16疫苗研研发提供了科学依据。     

Identification of a novel linear epitope in tetanus toxin recognized by a protective monoclonal antibody: Implications for vaccine design

Tetanus, a severe infectious disease, is caused by tetanus toxin (TT) from Clostridium tetani, which remains one of the most critical unsolved health problems despite preventive strategies. The carboxyl terminal of TT (TTC) is responsible for the binding of TT to neurons and for its toxicity and has been proven to be immunogenic and protective in various forms. It would therefore be extremely interesting to identify the epitope on TTC at a molecular level. In this study, we generated a neutralizing monoclonal antibody, 5C4, which inhibited TT binding to its receptor and was efficiently protective at 73.7 IU/mg. Moreover, 5C4 recognized a novel linear epitope on TT, namely TC_{(1155–1171)}, which spans from Lys1155 to Val1171. In addition, TC_{(1155–1171)} was shown to elicit the production of a serum IgG that protected mice against a challenge with TT. These results suggested that TC_{(1155–1171)} and the monoclonal antibody 5C4 are good candidates for the development of epitope-based vaccines and therapeutic antibodies against tetanus.     

Identification of B-cell epitopes in urease B subunit of Helicobacter pylori bound by neutralizing antibodies

To identify linear B-cell epitopes of urease B (UreB), a series of 19 partially overlapping fragments of the UreB gene were expressed. Three MAbs against UreB of Helicobacter pylori (H. pylori), A1H10, A3C10, and B3D9, were tested for their reactivity to the truncated proteins by Western blot and enzyme-linked immunosorbent assay (ELISA). Three linear B-cell epitopes were identified covering a stretch of 15 amino acid (aa) residues and localized in the aa regions 158–172, 181–195, and 349–363 of UreB. ELISA also showed that the three synthetic peptides containing epitope sequences (UP32: GGGTGPADGTNATTI, UP35: WMLRAAEEYSMNLGF, and UP38: TLHDMGIFSITSSDS) were recognized by the corresponding MAbs and H. pylori positive sera from H. pylori infected patients. Mice immunized with glutathione S-transferase (GST) fusion peptides showed that epitope-specific antibodies were capable of inhibiting urease enzymatic activity. These results should be useful in clinical applications and highlight the potential importance of these epitopes as the targets for development of epitope-based vaccines against H. pylori.     

An adult gerbil model for evaluating potential coxsackievirus A16 vaccine candidates

A suitable animal model of CVA16 infection is crucial in order to understand its pathogenesis and to help develop antiviral vaccines or screen therapeutic drugs. The neonatal mouse model has a short sensitivity period to CA16 infection, which is a major limitation. In this study, we demonstrate that adult (60-day-old) gerbils are susceptible to CVA16 infection at high doses (10^8.0 TCID₅₀). A clinical isolate strain of CVA16 was inoculated intraperitoneally into adult gerbils, which subsequently developed significant clinical symptoms, including hind limb weakness, paralysis of one or both hind limbs, tremors, and eventual death from neurological disorders. Real-time RT-PCR revealed that viral loads in the spinal cord and brainstem were higher than those in other organs/tissues. Histopathological changes, such as neuronal degeneration, neuronal loss, and neuronophagia, were observed in the spinal cord, brainstem, and heart muscle, along with necrotizing myositis. Gerbils receiving both prime and boost immunizations of alum adjuvant inactivated vaccine exhibited no clinical signs of disease or mortality following challenge by CVA16, whereas 80% of control animals showed obvious clinical signs, including slowness, paralysis of one or both hind limbs, and eventual death, suggesting that the CVA16 vaccine can fully protect gerbils against CVA16 challenge. These results demonstrate that an adult gerbil model provides us with a useful tool for studying the pathogenesis and evaluating antiviral reagents of CVA16 infection. The development of this animal model would also be conducive to screening promising CVA16 vaccine candidates as well as further vaccination evaluation.     

2008年柯萨奇病毒A组16型昆明分离株KMM08全基因组序列分析

目的 分析柯萨奇病毒A组16型(CA16)昆明分离株KMM08全基因序列,了解其遗传特性.方法 设计针对CA16引物,提取病毒RNA,RT-PCR扩增和产物直接测序获得序列.利用Mega 4.1,RDP3和SimPlot 3.5.1等软件分析全基因序列.结果 获得KMM08全基因组核苷酸序列长度为7409bp,编码含2193个氨基酸残基的多聚蛋白;与其他CA16参考株核苷酸和氨基酸同源性分别为79.0％～ 98.2％和94.5％ ～ 99.3％,其中SZ-HK08-3与国际标准株G10核苷酸和氨基酸同源性分别79.1％和94.8％;而与肠道病毒71型(EV71)标准株BrCr同源性分别为78.7％和89.0％.在各个区段上,KMM08与SZ-HK08-3的核苷酸和氨基酸同源性分别为97.0％～99.0％和98.0％～100.0％,同源性最高;与G10的核苷酸和氨基酸同源性分别为74.2％ ～ 86.9％和90.9％ ～97.0％;与EV71 BrCr核苷酸和氨基酸同源性分别在65.0％ ～ 84.9％和71.0％～95.2％.进化分析发现KMM08属于B基因型的一个分支.RDP3和SimPlot 3.5.1软件分析发现Tainan-5079-98序列发现重组信号,而KMM08未发现.结论 KMM08分离株为B基因型;CA16与EV71在非结构区发生重组.     

Efficacy of an inactivated bivalent vaccine for enterovirus 71 and coxsackievirus A16 in mice immunized intradermally

Human hand, foot, and mouth disease (HFMD), an important infectious disease in children, is caused mainly by enterovirus 71 (EV71) and coxsackievirus A16 (CA16). In this study, a bivalent inactivated EV71/CA16 vaccine is developed and evaluated in immunized BALB/c mice injected through the intradermal route. Q-RT-PCR detection of the mRNA of immune signal molecules in local epithelial tissues inoculated with the vaccine indicates activation of innate immunity, which includes upregulation of immune-related chemokines, interferons and CD molecules. Further, the finding that neutralizing antibodies and specific T cellular responses were elicited in adult mice after two immunizations with the vaccine at a 28-day interval, which endowed offspring mice to defend a viral challenge, suggests the successful induction of specific protective antiviral immunity. All these data suggest that immunization with this bivalent EV71/CA16 vaccine via the intradermal route elicits effective immunity against EV71 and CA16 infection.     

南京市20 1 0年柯萨奇病毒A组1 6型VPl区基因特征分析

柯萨奇病毒A组16型(CAl6)是引起手足El病的常见病原之一,与另一种手足口病的致病原--人肠道病毒7l型(EV71)相比,CAl6所致手足口病症状相对较轻?。近几年研究发现,CAl6感染可能引起严重并发症、21,偶尔引起新生儿死亡。本研究对20lo年从南京地区分离的CAl6进行VPl区序列测定和分析,以了解CAl6的流行情况及分子生物学特征。     

多重荧光逆转录PCR同时检测肠道病毒71型和柯萨奇病毒A16型

目的建立多重荧光逆转录PCR（RT-PCR）同时检测肠道病毒71型和柯萨奇病毒A16型的方法。方法在肠道病毒71型和柯萨奇病毒A16型VP1基因的保守区序列分别设计特异性引物和Taqman探针,建立优化多重荧光RT-PCR反应体系,评价所建多重荧光RT-PCR反应体系的特异性、敏感性和稳定性,并应用于临床样品检测。结果该方法对肠道病毒71型和柯萨奇病毒A16型检测具有高度特异性,检出限分别为0.1 TCID50和1 TCID50,具有较好的稳定性,可直接应用于临床样品的检测。结论本研究建立的多重荧光RT-PCR可以同时准确检测肠道病毒71型和柯萨奇病毒A16型,灵敏度高,稳定性好,是一种快速检测肠道病毒71型和柯萨奇病毒A16型的新方法。     

北京地区柯萨奇病毒A组6型、肠道病毒EV71型和柯萨奇病毒A组16型手足口病流行特征及临床特点比较

目的 了解柯萨奇病毒A组6型、肠道病毒71型和柯萨奇A组16型手足口病流行特征、临床特点,为指导临床诊断,调整手足口病防控策略提供科学依据.方法 采用前瞻性调查的方法,采集2013年8月至2015年9月在北京市儿童医院诊断的手足口病临床确诊病例的咽拭子,将手足口病原核酸检测阳性的病例分为CA6、EV71、CA16 3组,分析比较3组的临床特点、流行特征、预后及影响因素.结果 共采集HFMD临床诊断病例574例患儿咽拭子,CA6入组122例,EV71入组107例,CA16入组124例.①3组年龄、性别分布一致,差异无统计学意义.②不同年份流行主要毒株不同,但3种病原体引起的手足口病高峰均在夏季.③CA6组发热比例高达78.69％,明显高于EV71组(35.51％)和CA16组(37.90％) (P ＜0.001),平均体温约为38.78℃.CA6组表现大疱疹(9.01％)、结痂(8.20％)、皮疹部位疼痛(29.51％)、恢复期脱皮(38.52％)、脱甲(35.25％)、色素沉着(11.47％)比例高于EV71组、CA16(P ＜0.001).④3组在卫生学指标方面差异无统计学意义.结论 CA6、EV71和CA16感染所致的HFMD发病高峰季节一致;与EV71、CA16感染相比,CA6感染引起的高热比例较高,部分病例可表现为大疱疹,疼痛、脱皮、脱甲、色素沉着、结痂发生率高,预后较好.