H7N9亚型重组禽流感病毒rGD76株灭活疫苗的研制

利用H7N9亚型重组禽流感病毒rGD76株进行灭活疫苗的研制,并对疫苗的免疫效果进行评价,为家禽H7N9亚型流感的防控提供科学数据及手段。将AIV-rGD76株用灭菌生理盐水作104倍稀释后,接种11日龄非免疫鸡胚,37℃孵育72h后收获感染鸡胚尿囊液,经甲醛灭活后,加矿物油佐剂乳化制成油乳剂灭活疫苗,对制备疫苗的性状、安全性、免疫效力等进行检验。结果显示,制备的3批重组禽流感病毒灭活疫苗(H7N9亚型,rGD76株)均为油包水型,黏度均在50cP以内,对3批疫苗取样,样品经3000r/min离心15min,管底无水相析出。安全性试验结果显示,将疫苗按1mL/只超剂量接种3周龄SPF鸡,试验鸡在观察期内全部健活,未出现局部或全身不良反应,表明疫苗对SPF鸡具有良好的安全性;免疫效力及攻毒保护试验结果显示,用疫苗按0.3mL/只的剂量免疫接种3周龄SPF鸡1次,免疫接种后21d试验鸡血清中rGD76株的HI抗体平均效价可达8log2以上,使用H7N9亚型高致病性禽流感病毒GD16株滴鼻接种0.2mL/只(含100LD50)对免疫鸡进行攻毒,疫苗对免疫鸡的保护率均为100%。在实验室条件下研制出重组禽流感病毒灭活疫苗(H7N9亚型,rGD76株),疫苗的各项指标均符合标准。     

经鸡胚感染的ALV-J对新城疫弱毒疫苗免疫的抑制作用及疫苗株对病毒载量的影响

为了解经鸡胚感染携带J亚群禽白血病病毒(ALV-J)的雏鸡体内ALV-J对新城疫(ND)弱毒疫苗(La Sota株)免疫的抑制作用以及疫苗免疫后增强ALV-J对雏鸡致病作用的可能性,随机选择50个SPF鸡胚经卵黄囊接种模拟ALV-J感染,同时选取等量SPF鸡胚以相同方式接种PBS作为对照。出雏后于接毒组和对照组各取20只SPF鸡在7日龄时免疫ND弱毒疫苗(La Sota株)。2～6周龄时,记录各组鸡的体重和免疫器官指数,并对雏鸡的NDV抗体水平和血液ALV-J病毒载量进行动态检测。结果显示,感染ALV-J的SPF鸡5、6周龄时体重显著低于PBS对照组(P0.05),而感染ALV-J再免疫新城疫弱毒疫苗后SPF鸡体重进一步降低(P0.05);与PBS对照组相比,6周龄时感染ALV-J的SPF雏鸡胸腺萎缩和脾脏肿大(P0.05),免疫新城疫弱毒疫苗后胸腺和脾脏损伤加剧(P0.05);3、4周龄时感染ALV-J再免疫ND弱毒疫苗组的雏鸡NDV抗体水平极显著低于仅免疫ND弱毒疫苗组(P0.01);4周龄时免疫弱毒疫苗后的SPF鸡血液中ALV-J病毒载量高于未免疫组(P0.01)。研究表明,感染ALV-J的雏鸡在免疫ND弱毒疫苗(La Sota株)后增强了ALV-J对SPF雏鸡的致病作用,提示净化种源的重要性。     

4型禽腺病毒HLJ1701株灭活疫苗的研制

利用4型禽腺病毒HLJ1701株进行灭活疫苗的研制,并对疫苗的免疫效果进行评价,为家禽4型禽腺病毒的防控提供数据及参考。将HLJ1701株用灭菌生理盐水作10~4倍稀释后,接种9日龄SPF鸡胚,37℃孵育72 h后收获感染鸡胚尿囊液,经甲醛灭活后,加白油佐剂乳化制成油乳剂灭活疫苗,对制备疫苗的性状、安全性、免疫效力等进行检验。结果显示,制备的3批4型禽腺病毒灭活疫苗(HLJ1701株)均为油包水型,黏度均在50 cP以内,对3批疫苗取样,样品经3000 r/min离心15 min,管底无水相析出。安全性试验结果显示,将疫苗按1 mL/只超剂量接种3周龄SPF鸡,试验鸡在观察期内全部健活,未出现局部或全身不良反应,表明疫苗对SPF鸡具有良好的安全性;免疫效力及攻毒保护试验结果显示,用疫苗按0.2 mL/只的剂量免疫接种3周龄SPF鸡1次,免疫接种后21d试验鸡血清中HLJ1701株的抗体平均效价可达2~8以上,使用4型禽腺病毒(HLJ1701株)接种0.2 mL/只(100 LD_(50))对免疫鸡进行攻毒,疫苗对免疫鸡的保护率均为100%。研究表明,实验室条件下研制的4型禽腺病毒(HLJ1701株)灭活疫苗的各项指标均符合标准。     

H9N2亚型禽流感病毒HA蛋白S145N变异株致病性及抗原特性

为确定近年来H9N2亚型禽流感病毒(AIV) HA蛋白S145N点突变对病毒毒力变化和抗原性变异的影响,笔者对从全国不同地区分离的12株H9N2亚型AIV HA蛋白S145N变异株和HP疫苗参考株进行了半数鸡胚感染量(EID50)、半数鸡胚致死量(ELD50)、平均鸡胚致死时间(MDT)、雏鸡脑内致病指数(ICPI)、鸡静脉致病指数(IVPI)和8周龄SPF鸡感染排毒试验,并与抗H9N2亚型AIV HP参考株HA蛋白单抗2A4和F6的血凝抑制(HI)和中和反应特性进行测定.结果发现,H9N2亚型AIV HA蛋白S145N变异株毒力偏强,能引起部分SPF鸡发病和死亡,感染8周龄SPF鸡排毒时间更早,排毒期更长.单抗2A4和F6不能抑制H9N2亚型AIV HA蛋白S145N变异株的血凝特性,也不能中和病毒感染CEF细胞.研究结果表明,H9N2亚型AIV呈现变异趋势,有毒力增强和抗原性变异毒株出现.S145为H9N2亚型AIV HA蛋白的1个抗原位点,是血凝抑制抗体结合的位点,但有该位点漂变导致抗原变异毒株出现,并可逃避免疫作用.这提示该病的防控面临着新的挑战.     

H5N1亚型禽流感变异株灭活疫苗种毒Re-4株的生物学特性及免疫原性研究

本实验对经反向遗传方法构建的重组禽流感H5N1亚型变异株灭活疫苗种毒Re-4株的生物学特性及免疫效力进行研究.将Re-4株接种SPF鸡胚后37℃培养72 h,鸡胚存活,无病变,HA滴度达29;以0.1 mL(106.0EID50/0.1 mE)的剂量鼻腔感染4周龄SPF鸡7 d后血清HI抗体转阳,无任何症状,也不排毒;SPF鸡静脉致病指数(IVPI)为0;以Re-4重组株为种毒制备灭活疫苗,免疫SPF鸡后,3周后平均HI抗体效价达8.75 log2:免疫鸡对亲本强毒株CKSX/06,以及变异株CKNX/06和流行株GSGD/96攻击提供完全保护.以上结果表明变异株灭活疫苗种毒Re-4株对SPF鸡胚和SPF鸡无致病性、适合鸡胚增殖、抗原针对性强,并且以该毒株制备的灭活疫苗具有良好的免疫效力,是研制预防H5N1亚型禽流感病毒山西变异株的理想疫苗种毒株.     

H9N2亚型禽流感病毒细胞高产株的拯救

为构建能够在MDCK细胞中高水平复制的H9N2亚型禽流感病毒(AIV)疫苗株,本研究在对病毒生长特性及HA基因遗传进化分析的基础上,筛选出一株细胞高度适应的国内流行株A/chicken/Shanghai/11/2011(H9N2) (SH11),并通过反向遗传操作技术拯救出全部基因均来自亲本株的AIV rSH11株.生物学试验结果表明rSH11在鸡胚半数感染量(EID50)、组织培养半数感染量(TCID50)、遗传稳定性等方面均与亲本株保持一致,rSH11经MDCK细胞连续传5代后血凝价稳定在1∶1024,表明该病毒株具有细胞高度增殖的特性.采用rSH11株制备油乳剂灭活苗免疫4周龄SPF鸡,免疫一周即可以检测出HI抗体,免疫3周后HI抗体平均效价高于1∶700,表明其具有良好的免疫原性.rSH11疫苗对不同的H9N2病毒株能够产生良好的免疫保护作用,显著抑制免疫鸡排毒.H9N2亚型AIV细胞高产株的拯救为该亚型AIV细胞苗的研制奠定了基础.     

2株H7N9亚型重组禽流感病毒的生物学特性和免疫原性研究

为评估经反向遗传构建的H7N9亚型重组禽流感病毒(AIV)H7-Re1株和H7-Re2株的生物学特性及免疫原性,本研究将这2株病毒分别以104倍稀释接种10日龄SPF鸡胚后,36℃培养,观察鸡胚存活情况并检测病毒HA效价,结果显示96 h时,2株病毒接种的鸡胚全部存活,培养至72 h时其HA效价均为9 log2,均显著高于亲本分离株。测定2株病毒的静脉内接种致病指数(IVPI),结果显示均为0。将2株病毒分别以10~6EID_(50)剂量鼻腔内接种5周龄SPF鸡,进行致病性试验,结果显示,接种后14 d内,2株病毒接种鸡均无临床症状,也不排毒。以2株病毒为种毒分别制备油乳剂灭活疫苗,以0.3 mL/只接种3周龄SPF鸡后3周时检测免疫鸡血清中HI抗体,结果显示,两种疫苗免疫鸡平均HI效价均可达到8.0 log2。于免疫后21 d,H7-Re1株免疫组鸡分别攻击10~6EID_(50)的H7N9亚型低致病力AIV(PG/SHH/S1069/13株)和10~5EID_(50)的高致病力AIV(CK/GX/SD098/17株),进行攻毒试验,结果显示两种病毒攻毒后免疫鸡均全部存活,且无发病和排毒出现。H7-Re2株免疫组鸡于免疫后21 d分别以10~5EID_(50)的剂量进行高致病力H7N9亚型AIV(CK/GX/SD098/17株)和H7N2亚型AIV(DK/FJ/SE0195/18株)的攻毒保护试验,结果显示两种病毒攻毒后免疫鸡均不发病、不死亡、不排毒。以上结果表明,以H1N1亚型A/Puerto Rico/8/34株病毒为内部基因供体、经反向遗传学方法构建的H7-Re1株和H7-Re2株均具有生长滴度高、生物安全性高和免疫原性好的特点。本研究为H7N9亚型禽流感疫苗的研制和应用奠定了基础。     

H9N2亚型禽流感疫苗株的筛选及其免疫效果评价

通过交叉血凝试验,疫苗备用毒株免疫SPF鸡后再用同源和异源毒株攻毒,评价疫苗备用毒株对SPF鸡保护效果。结果显示,H9N2疫苗备用株免疫SPF鸡后,再用H9亚型流感病毒流行株攻毒,SPF鸡咽喉和泄殖腔排毒量大大降低。结果表明,本试验筛选的疫苗备用毒株对H9N2亚型流感病毒具有一定的保护率,完全符合疫苗株要求。     

H5N1亚型禽流感病毒A/goose/Guangdong/1/96的NS基因对鸡致病能力的影响

为了解H5N1亚型禽流感病毒经自然途径感染SPF鸡后，病毒的致病能力与NS基因的关系，本文主要从病理学角度比较了两株利用反向基因操作技术拯救的病毒RGSGD／1／96和RGSGD／1／2NS的致病能力。虽然只有NS基因不同，但是这两株病毒经鼻腔感染4周龄SPF鸡后表现出完全不同的致病能力，RGSGD／1／96对鸡的致死率为100％，感染鸡只的各组织脏器均可发现严重的病理损伤，该病毒在鸡体内复制能力很强，感染后3d、6d，各组织脏器均可发现大量的病毒抗原；GSGD／1／2NS对鸡的致死率为0，病毒在感染鸡体内只引起肺间质少量淋巴细胞浸润，免疫组织化学检查未发现病毒抗原信号。由于两株病毒只有NS基因不同，说明NS基因决定了H5N1亚型禽流感病毒A／goose／Guangdong／1／96对SPF鸡的致病能力。     

H9N2亚型禽流感病毒冷适应株的培育及SPF鸡胚感染后的免疫应答分析

H9N2亚型禽流感病毒(H9N2AIV)冷适应疫苗可以弥补灭活疫苗临床保护效果的不足。为明确宿主对冷适应疫苗的免疫应答效应,本研究将H9N2AIV(A/chicken/Shandong/903/2013,CK/903/2013)接种10日龄SPF鸡胚连续降温传代,获得在25℃能够稳定复制的冷适应株Ca30。实验结果显示:Ca30株具备冷适应性和温度敏感性,在传代过程中病毒HA蛋白出现多个位点的氨基酸突变,在25℃传代20次后已经获得稳定的氨基酸突变。动物感染试验结果显示,以106.0EID50的剂量鼻腔感染1周龄SPF鸡,Ca30株仅在喉气管中低水平复制,病毒接种后第3周SPF鸡血清针对Ca30株、异源病毒株1167的血凝抑制效价均达到最高,分别为8.2log2和5.8log2,接种后第4周针对母本病毒CK/903/2013的血凝抑制效价达到最高值7.6log2。qPCR检测结果显示,Ca30在25℃时能够在鸡胚肺脏、肝脏和心脏中复制,对肺脏的亲和力最强。利用qPCR检测冷适应株Ca30接种鸡胚后各脏器细胞因子的转录水平,结果显示,Ca30株感染鸡胚后,引起鸡胚肺脏中IL-1β、IL-6、IL-12、IL-8、OAS和MDA5转录水平上调,上调4.18~16.47倍;感染后8h引起鸡胚心脏中IL-1β、IL-6、IL-12、IL-8、OAS和MDA5的转录水平上调,之后降低甚至下调;72h时引起鸡胚肝脏中IL-1β、IL-6、IL-8和OAS转录水平上调,上调4.28~6.53倍;在鸡胚脑组织中,各类细胞因子的转录水平变化无明显的规律。本研究培育了一株H9N2AIV冷适应毒株Ca30,为深入研究冷适应弱毒疫苗的免疫保护机制提供了素材。     

Generation and evaluation of reassortant influenza vaccines made by reverse genetics for H9N2 avian influenza in Korea

The prevalence and continuous evolution of H9N2 avian influenza viruses in poultry have necessitated the use of vaccines in veterinary medicine. Because of the inadequate growth properties of some strains, additional steps are needed for producing vaccine seed virus. In this study, we generated three H9N2/PR8 reassortant viruses using a total cDNA plasmid-transfection system, as an alternative strategy for developing an avian influenza vaccine for animals. We investigated the vaccine potency of the reassortant viruses compared with the existing vaccine strain which was adapted by the 20th serial passages in embryonated eggs with A/Ck/Kor/01310/01 (H9N2). The H9N2/PR8 reassortant viruses, containing the internal genes of the high-yielding PR8 strain and the surface gene of the A/Ck/Kor/01310/01 strain, could be propagated in eggs to the same extent as existing vaccine strain without additional processing. Similar to vaccine strain, the H9N2/PR8 reassortant viruses induced hemagglutination-inhibiting antibodies in chickens and prevented virus shedding and replication in multiple organs in response to homologous infection. However, due to the continuing evolution and increasing biologic diversity of H9N2 influenza in Korea, the vaccine provided only partial protection against currently isolates. Taken together, our results suggest that the H9N2/PR8 reassortant virus can be used as a seed virus for avian influenza vaccines in poultry farm. Considering the constant genetic changes in H9 strains isolated in Korea, this reverse genetic system may offer a prompt and simple way to change the vaccine seed virus and mitigate the impact of unexpected influenza outbreaks.     

A single dose of inactivated oil-emulsion bivalent H5N8/H5N1 vaccine protects chickens against the lethal challenge of both highly pathogenic avian influenza viruses

In this study, two highly pathogenic avian influenza (HPAI) H5N8 viruses were isolated from chicken and geese in 2018 and 2019 (Chicken/ME-2018 and Geese/Egypt/MG4/2019). The hemagglutinin and neuraminidase gene analyses revealed their close relatedness to the clade-2.3.4.4b H5N8 viruses isolated from Egypt and Eurasian countries. A monovalent inactivated oil-emulsion vaccine containing a reassortant virus with HA gene of the Chicken/ME-2018/H5N8 strain and a bivalent vaccine containing same reassortant virus plus a previously generated reassortant H5N1 strain (CK/Eg/RG-173CAL/17). The safety of both vaccines was evaluated in specific-pathogen-free (SPF) chickens. To evaluate the efficacy of the prepared vaccines, 2-week-old SPF chickens were vaccinated with 0.5 mL of a vaccine formula containing 10⁸/EID₅₀ /dose from each strain via the subcutaneous route. Vaccinated birds were challenged with either wild-type HPAI-H5N8 or H5N1 viruses separately at 3 weeks post-vaccine. Results revealed that both vaccines induced protective hemagglutination-inhibiting (HI) antibody titers as early as 2 weeks PV (≥5.0 log₂). Vaccinated birds were protected clinically against both subtypes (100 % protection). HPAI-H5N1 virus shedding was significantly reduced in birds that were vaccinated with the bivalent vaccine; meanwhile, HPAI-H5N8 virus shedding was completely neutralized in both tracheal and cloacal swabs after 3 days post-infection in birds that had been vaccinated with either vaccine. In conclusion, the developed bivalent vaccine proved to be efficient in protecting chickens clinically and reduced virus shedding via the respiratory and digestive tracts. The applicability of the multivalent avian influenza vaccines further supported their value to facilitate vaccination programs in endemic countries.     

口蹄疫纳米乳疫苗免疫持续期的试验研究

试验用同一批次相同抗原含量的口蹄疫病毒灭活抗原,分别采用纳米乳佐剂和ISA206佐剂配制口蹄疫O型、A型双价灭活疫苗,并对仔猪进行免疫,免疫后6个月内用液相阻断ELISA方法检测O型、A型免疫抗体效价(lg)。结果:免疫后6个月内纳米乳疫苗免疫猪产生的抗体lg平均值均高于ISA206佐剂疫苗,抗体水平在免疫后1个月达到最高。免疫后第6个月,纳米乳疫苗O型抗体lg平均值为2.19,A型抗体lg平均值为2.175,按液相阻断ELISA试剂盒的判定标准免疫猪抗体lg≥1.8,具有99%以上保护效力,纳米乳疫苗属于完全保护范围,而ISA206佐剂疫苗属于不完全保护范围。     

几种法氏囊活疫苗对鸡法氏囊损伤及免疫抑制作用的比较

探讨了鸡传染性法氏囊病（ＩＢＤ）活疫苗对鸡新城疫活苗免疫的影响。将四种ＩＢＤ活苗分别接种３０日龄ＳＰＦ公雏,４天后再免疫鸡新城疫ＬａＳｏｔａ系活疫苗,同时法氏囊损伤情况。试验结果表明,所选ＩＢＤ活疫苗对雏鸡法氏囊均有不同程度地损伤,并且诱导产生ＮＤ－ＨＩ抗体的时间被推迟。     

Antigenic and genetic variations in European and North American equine influenza virus strains (H3N8) isolated from 2006 to 2007

Equine influenza virus (EIV) surveillance is important in the management of equine influenza. It provides data on circulating and newly emerging strains for vaccine strain selection. To this end, antigenic characterisation by haemaggluttination inhibition (HI) assay and phylogenetic analysis was carried out on 28 EIV strains isolated in North America and Europe during 2006 and 2007. In the UK, 20 viruses were isolated from 28 nasopharyngeal swabs that tested positive by enzyme-linked immunosorbent assay. All except two of the UK viruses were characterised as members of the Florida sublineage with similarity to A/eq/Newmarket/5/03 (clade 2). One isolate, A/eq/Cheshire/1/06, was characterised as an American lineage strain similar to viruses isolated up to 10 years earlier. A second isolate, A/eq/Lincolnshire/1/07 was characterised as a member of the Florida sublineage (clade 1) with similarity to A/eq/Wisconsin/03. Furthermore, A/eq/Lincolnshire/1/06 was a member of the Florida sublineage (clade 2) by haemagglutinin (HA) gene sequence, but appeared to be a member of the Eurasian lineage by the non-structural gene (NS) sequence suggesting that reassortment had occurred. A/eq/Switzerland/P112/07 was characterised as a member of the Eurasian lineage, the first time since 2005 that isolation of a virus from this lineage has been reported. Seven viruses from North America were classified as members of the Florida sublineage (clade 1), similar to A/eq/Wisconsin/03. In conclusion, a variety of antigenically distinct EIVs continue to circulate worldwide. Florida sublineage clade 1 viruses appear to predominate in North America, clade 2 viruses in Europe.     

大型繁育猪场应用TGE弱毒疫苗和PED灭活疫苗的效果观察

某大型猪场临床仔猪见不明原因腹泻,发病率高,而对妊娠母猪普遍接种ＴＧＥ和ＰＥＤ疫苗后收到了明显的防病效果。     

The Seroprevalence of Canine Influenza Virus H3N8 in Dogs Participating in a Flyball Tournament in Pennsylvania in 2010: A Follow‐Up Study

Background

Canine influenza virus (CIV) H3N8 infection is thought to be highly contagious and potentially deadly. Low seroprevalence in dogs participating in the sport of flyball in 2009 was reported. It remains unknown if prevalence is changing in dogs at risk.

Objective

To determine seroprevalence of antibodies to CIV H3N8 in a population of pet dogs that participated in an indoor flyball tournament in Pennsylvania in November 2010.

Animals

Dogs participating in a flyball tournament.

Methods

Medical, travel, and activity histories for previous 10.5 months were obtained from consenting owners and serum samples were collected from dogs. Antibodies to CIV H3N8 were measured using hemagglutination inhibition.

Results

Of 251 competing dogs, 103 dogs were tested. Overall, seroprevalence of CIV H3N8 in dogs participating in flyball was 1.9% (95% CI, 0.05–6.8%). Thirty‐five dogs were tested in both 2009 (all titers <8) and 2010 (all titers <8). Ten of 103 dogs had been vaccinated for CIV H3N8. Two dogs had positive titers (>8) and both had been vaccinated twice in the previous month. Titers in remaining 8 vaccinated dogs were undetectable. Seroprevalence in vaccinated dogs was 20% (95% CI, 5.7–50.1%), whereas in unvaccinated dogs it was 0% (95% CI, 0–4.0%). Although 7 dogs had history of respiratory signs, only 1, which was vaccinated, was serologically positive for CIV H3N8.

Conclusions

Consistent with low prevalence of CIV H3N8 exposure previously reported in flyball dogs, unvaccinated dogs had 0% prevalence, suggesting a stable exposure rate. However, low seroprevalence may result in unprotected flyball dogs at risk for developing CIV H3N8.     

Assessing the Existing Information on the Efficacy of Bovine Vaccination against Escherichia coli O157:H7 – A Systematic Review and Meta‐analysis

The objective of this study was to conduct a systematic review and meta‐analysis to evaluate the existing information on the efficacy of commercial vaccination to reduce the prevalence of Escherichia coli O157:H7 in weaned cattle in beef feedlot finishing systems under commercial conditions. Currently, only two commercial vaccines exist, and thus, only publications reporting the use of vaccines targeting type III secreted proteins and/or siderophore receptor and porin proteins (SRP) were considered relevant. A total of 18 studies reporting 45 comparisons were included in this review. Meta‐analyses were conducted variously on (i) pre‐harvest outcomes, (ii) at‐harvest outcomes and (iii) both pre‐harvest and at‐harvest outcomes combined. Overall, efficacy of vaccination was consistently observed. Efficacy and homogeneity of the results was demonstrated for the two‐dose regimen, allowing us to conclude with confidence that the two‐dose approach is efficacious. For pre‐harvest outcomes and two‐dose regimens, the odds ratios (OR) were 0.53 (95% CI = 0.45–0.62) for the two vaccines combined and 0.49 (95% CI = 0.40–0.60) for vaccine targeting type III secreted proteins. The test for heterogeneity among studies yielded a Q test P = 0.354 for the two vaccines combined and Q test P = 0.269 for the vaccine targeting type III secreted proteins, indicating homogeneity in both cases. For pre‐ and at‐harvest outcomes combined and two‐dose regimens, the odds ratios (OR) were 0.52 (95% CI = 0.44–0.61) for the two vaccines combined and 0.45 (95% CI = 0.34–0.60) for vaccine targeting type III secreted proteins. The test for heterogeneity among studies yielded a Q test P = 0.134 for the two vaccines combined indicating homogeneity and Q test P = 0.089 for the vaccine targeting type III secreted proteins indicating heterogeneity. Based on this meta‐analysis, bovine vaccination appears to be an effective approach to the pre‐harvest control of E. coli O157:H7.     

锥虫疫苗的研究进展

为了掌握锥虫病免疫预防苗的研究概况和今后研究方向，对国内外有关文献资料作了综述，包括锥虫弱毒苗、强毒苗、亚单位苗、抗独特型抗体苗、基因工程苗等各类疫苗的制备方法和使用效果，还包括免疫佐剂和免疫接种方法等方面内容，并分析了未能成为实用疫苗的原因，指出了今后研制疫苗的途径。