Comparative evaluation of live marker vaccine candidates "CP7_E2alf" and "flc11" along with C-strain "Riems" after oral vaccination

Due to the tremendous socio-economic impact of classical swine fever (CSF) outbreaks, emergency vaccination scenarios are continuously under discussion. Unfortunately, all currently available vaccines show restrictions either in terms of marker capacities or immunogenicity. Recent research efforts were therefore directed at the design of new modified live marker vaccines. Among the most promising candidates the chimeric pestiviruses "CP7_E2alf" and "flc11" were identified. Within an international research project, these candidates were comparatively tested in challenge experiments after a single oral vaccination. Challenge infection was carried out with highly virulent CSF virus strain "Koslov", 14 or 21 days post vaccination (dpv), respectively. Safety, efficacy, and marker potential were addressed. All assessments were done in comparison with the conventional "gold standard" C-strain "Riems" vaccine. In addition to the challenge trials, multiple vaccinations with both candidates were performed to further assess their marker vaccine potential. All vaccines were safe and yielded full protection upon challenge 21 days post vaccination. Neither serological nor virological investigations showed major differences among the three vaccines. Whereas CP7_E2alf also provided clinical protection upon challenge at 14 days post vaccination, only 50% of animals vaccinated with flc11, and 83% vaccinated with C-strain "Riems" survived challenge at this time point. No marked differences were seen in protected animals. Despite the fact that all multiple-vaccinated animals stayed sero-negative in the accompanying marker test, the discriminatory assay remains a weak point due to delayed or inexistent detection of some of the vaccinated and subsequently infected animals. Nevertheless, the potential as live marker vaccines could be confirmed for both vaccine candidates. Future efforts will therefore be directed at the licensing of "Cp7_E2alf" as the first live marker vaccine for CSF.     

布鲁氏菌弱毒疫苗粘膜免疫及检测方法的研究

为研究布鲁氏菌弱毒疫苗粘膜免疫及其检测方法,本实验采用粘膜点眼途径对健康母羊接种布鲁氏杆菌猪2号疫苗(S2)、牛19号疫苗(A19)和羊强毒株(M16),筛选布鲁氏杆菌病鉴别检测方法。将12月龄～14月龄母羊60只随机分为3组,以常规疫苗推荐剂量进行半量粘膜点眼接种。采集血液、淋巴、脏器进行布鲁氏菌病血清学检测和细菌学分离以及PCR检测。结果表明:布鲁氏菌弱毒疫苗抗体水平持续6个月,其中血清学的试管凝集试验、半胱氨酸凝集试验与补体结合试验的阳性符合率达到100%。细菌分离期为6个月,乳腺、乳腺淋巴、髂淋巴分离率较高;而强毒株M16的抗体水平和细菌分离持续12个月以上。结果显示以常规血清学和细菌学检测方法在点眼免疫布鲁氏菌S2、A19苗6个月后可以进行野毒感染和疫苗免疫畜的鉴别诊断。     

基于新城疫病毒V蛋白鉴别鸡群感染与免疫的间接ELISA方法的建立

本研究以新城疫病毒(NDV)V蛋白羧基端结构域(Vc)的重组蛋白为包被抗原,建立了用于检测NDV V蛋白抗体的间接ELISA方法,并采用该方法检测了鸡群免疫或接毒后血清中的V蛋白抗体水平。结果显示:两组不同NDV灭活疫苗组在免疫后的3周内检测结果均为阴性;两组灭活疫苗免疫3周后再人工感染NDV强毒的鸡群,攻毒后第7、14和21 d,NDV阳性率分别为60%、80%、70%和50%、80%、70%;两组不同的NDV弱毒疫苗免疫组鸡群,仅在免疫后第21 d阳性率分别为20%和10%。以上结果表明,NDV疫苗免疫组与强毒感染组的V蛋白抗体阳性率存在明显差异,本方法可在群体水平上区分新城疫疫苗免疫与强毒感染鸡群,为NDV血清学诊断和流行病学调查提供了一种新的检测手段。     

Is there a benefit from an early booster vaccination in the control of equine influenza?

Conventional equine influenza vaccination schedules consist of a primary course of two vaccinations given 4-6 weeks apart followed by a third vaccination (booster) given approximately 5 months later. In between the primary course and the third vaccination, horses are generally considered not to be adequately protected against influenza. This study aimed to investigate whether Thoroughbred foals would benefit from a vaccination schedule in which the third vaccination was given earlier than in conventional vaccination schedules. The vaccines used were an inactivated whole virus equine influenza vaccine and an inactivated whole virus combination vaccine containing equine influenza and equine herpesvirus antigens. Four groups of foals were vaccinated with the two vaccines according to a conventional and an accelerated vaccination schedule in which the third vaccination was given 14 weeks after the first administration. In both groups, the fourth vaccination was given at the normally recommended interval of 26 weeks after the third vaccination for the combination vaccine and 52 weeks after the third vaccination with the influenza only vaccine. The horses were 4-11 months of age and seronegative for influenza. Immunological responses after vaccination were monitored for several months using the single radial haemolysis test. The results indicated that 28 weeks after the first vaccination, antibody levels in horses vaccinated according to the accelerated schedule were not significantly higher than in horses vaccinated according to the conventional schedule. In addition, the total level of antibody production (area under the curve) was not significantly different at that point although antibody titres were slightly higher (but not significantly so) between 16-30 weeks in the accelerated schedule. Between the third and fourth doses, horses vaccinated according to the accelerated schedule had antibodies against influenza below the level required for clinical protection for 39 and 18 weeks for the influenza only and the combination vaccine, respectively, whereas those vaccinated according to the conventional schedule had antibody titres below the level for clinical protection for 9-15 weeks in the corresponding period for both vaccines. Horses vaccinated according to the accelerated schedule with the combination vaccine had lower antibody titres after the fourth vaccination than those vaccinated according to the conventional schedule after the third vaccination, although antibody titres prior to vaccination were similar. For the influenza only vaccine, titres after the accelerated fourth administration were not different to those after the conventional third vaccination. There was no benefit from early booster vaccinations with the vaccines used in this study, so for these vaccines the conventional schedule provided better protection than the selected accelerated alternative. This may contrast with some other vaccine formulations, although a direct comparison using similar protocols has not been made.     

LABORATORY AND FIELD STUDIES WITH A BOVINE EPHEMERAL FEVER VACCINE

Bovine ephemeral fever (BEF) virus vaccines, prepared from the brains of suckling mice infected with strain 525 BEF virus, were evaluated in housed cattle and in the field. The virus in lyophilised preparations was stable for 6 months at -50 degrees C. Thirty-four calves, 5 to 18 months old, were used in laboratory vaccination trials. An increase in serum neutralising antibody was detected in 13 of 14 calves initially free of serum antibody, and all 13 failed to develop clinical illness following challenge with virulent BEF virus. Vaccination resulted in no detectable serum antibody increase in 4 calves, 5 months old, with pre-existing antibody of presumed maternal origin. Seven animals, 18 months of age with serum antibody presumed due to previous BEF infection, developed increased antibody titres following vaccination. In 3 animals vaccinated but not challenged, vaccine-induced antibodies decreased to low levels over 5 months. In contrast, the antibody titres following infection with virulent virus in 2 calves were maintained over 5 months. Field trials, involving 236 animals initially free of serum antibody, were conducted on 5 properties near Mackay and 4 properties near Brisbane. Most of 164 animals were vaccinated with a single dose of lyophilised vaccine containing aluminium hydroxide adjuvant. Only 4 animals failed to develop serum antibody and no adverse reactions to vaccination were reported. Natural infection with BEF occurred in 4 herds at Mackay and clinically mild BEF occurred in 3 of 109 vaccinated and 3 of 46 control animals. On the basis of measured serum antibody titres it was assumed that 8 of 53 animals receiving full vaccine volume, 20 of 40 animals receiving half vaccine volume and 18 of 40 control animals became infected with BEF virus. Two dairy herds in Brisbane became naturally infected with virulent BEF virus 7 months after vaccination. Clinical BEF was observed in 8 of 11 control animals and in 3 of 26 animals which received 2 doses of vaccine. Two strains of BEF virus were isolated from unvaccinated animals that developed clinically mild BEF in the field. These strains either failed to infect, or produced subclinical or very mild BEF, when inoculated intravenously into susceptible calves. The anitbody response to natural infection with apparently mild viruses was short-lived, similar to that produced by vaccination.     

Assessment of serological response of young and adult sheep to conjunctival vaccination with Rev-1 vaccine by fluorescence polarization assay (FPA) and other serological tests for B. melitensis

The serological response of young and adult sheep vaccinated conjunctivally with Rev-1 vaccine was assessed by fluorescence polarization assay (FPA), Rose Bengal test (RBT), complement fixation test (CFT), modified Rose Bengal test (m-RBT), indirect ELISA (i-ELISA) and competitive ELISA (c-ELISA), at different post vaccination intervals. One hundred and thirty six adult sheep and 64 lambs were used in the study. The vaccinated animals were bled prior to vaccination (0 day) and thereafter at 21st, 42nd, 35th, 63rd, 91st, 125th, 159th, and 223rd and 330th day post vaccination. The majority of animals (young and adult) showed positive reaction by FPA, RBT, CFT, m-RBT and c-ELISA 21 days post vaccination, whereas by i-ELISA at 42 days. All tests perform equal when animals vaccinated as young are tested 125 days (4 months) post vaccination. In case of animals vaccinated at adulthood, FPA, RBT, CFT and c-ELISA perform equal if the animals are tested 223 days (approximately 8 months) post vaccination. I-ELISA and m-RBT show low specificity if ewes vaccinated at adulthood are tested 330 days (11 months) post vaccination. If control of brucellosis in sheep is based on conjunctivally vaccination of lambs with Rev-1, the vaccinated animals can be tested by any test used for diagnosis of B.melitensis infection accurately at least 4 months post vaccination. If brucellosis control is based on mass vaccination the use of m-RBT and i-ELISA is not recommended for testing adult animals at least for 330 days (11 months) post vaccination due to tests low specificity. Further research is needed so the appropriate cut-offs to be established for FPA, c-ELISA or i-ELISA to become valuable tools for the eradication of Brucella spp. infection in small ruminants in areas where vaccination is practiced.     

Potency of an experimental DNA vaccine against Aujeszky's disease in pigs

Intradermal vaccination with plasmid DNA encoding envelope glycoprotein C (gC) of pseudorabies virus (PrV) conferred protection of pigs against Aujeszky's disease when challenged with strain 75V19, but proved to be inadequate for protection against the highly virulent strain NIA-3. To improve the performance of the DNA vaccine, animals were vaccinated intradermally with a combination of plasmids expressing PrV glycoproteins gB, gC, gD, or gE under control of the major immediate-early promotor/enhancer of human cytomegalovirus. 12.5 microg per plasmid were used per immunization of 5-week old piglets which were injected three times at biweekly intervals. Five out of six animals survived a lethal challenge with strain NIA-3 without exhibiting central nervous signs, whereas all the control animals succumbed to the disease. This result shows the increased protection afforded by administration of the plasmid mixture over vaccination with a gC expressing plasmid alone. A comparative trial was performed using commercially available inactivated and modified-live vaccines and a mixture of plasmids expressing gB, gC, and gD. gE was omitted to conform with current eradication strategies based on gE-deleted vaccines. All six animals vaccinated with the live vaccine survived the lethal NIA-3 challenge without showing severe clinical signs. In contrast, five of six animals immunized with the inactivated vaccine died, as did two non-vaccinated controls. In this test, three of six animals vaccinated with the DNA vaccine survived without severe clinical signs, whereas three succumbed to the disease. Comparing weight reduction and virus excretion, the DNA vaccine also ranged between the inactivated and modified-live vaccines. Thus, administration of DNA constructs expressing different PrV glycoproteins was superior to an adjuvanted inactivated vaccine but less effective than an attenuated live vaccine in protection of pigs against PrV infection. Our data suggest a potential use of DNA vaccination in circumstances which do not allow administration of live attenuated vaccines.     

含粘膜佐剂的鸡新城疫疫苗诱导雏鸡非特异性免疫应答的研究

为研究分析重组大肠杆菌不耐热肠毒素（labile enterotoxin,LT）作为粘膜佐剂,配伍鸡新城疫疫苗的冻干样品对免疫鸡非特异性免疫应答的影响,在前期已经构建的LTR72/G192基础上,选择2、4μg LTRG蛋白作为每羽份疫苗添加量,及降低新城疫病毒（Newcastle disease virus,NDV）50%抗原量等配伍条件。按照生产条件制备冻干疫苗,进行雏鸡免疫试验,免疫后24、48、72 h采集脾脏、胸腺淋巴结,检测几种非特异性细胞因子表达水平。结果表明：IL-6、INF-γ水平在各疫苗免疫后24h即升高,48 h达最高值;添加2、4μg LTRG蛋白的NDV疫苗组IFN-β、TNF-α水平在48 h左右显著升高,其中含4μg LTRG疫苗组与其他组差异具有极显著统计学意义（P〈0.01）;IL-6、IFN-γ转录水平有所增强,但各组间差异不具有显著统计学意义（P〉0.05）,72 h左右几种细胞因子水平均迅速下降,与NDV疫苗接种组相近。由此可见,LTRG能辅助抗原诱导免疫雏鸡的非特异性免疫应答,有利于对感染病毒的清除。     

Foot-and-mouth disease. Challenge of cattle after multiple vaccinations

Four groups of six cattle were vaccinated from two to five times at 6 month intervals with two different trivalent FMD vaccines licensed in the given year. The FMDV type A strains in the vaccines designated A5F and A5B were closely related. Three months after the last vaccination the cattle were challenged by contact with animals inoculated with the original field strain A5B. The inoculated animals developed typical FMD symptoms with vesicles in the mouth and on the feet. Those cattle which had received vaccines that did not contain strain A5B also became severely sick, even after five vaccinations. Animals vaccinated twice with type B containing vaccine were also not completely protected. A safe protection can obviously only be achieved for fairly short periods of time if vaccine and challenge strain are homologous. It is proposed to change the rules of licensing, to speed up the procedure to vaccinate in cases of outbreaks. The need for further research, especially into improving vaccines, is stressed.     

Vaccines against bluetongue in Europe

After the incursion of bluetongue virus (BTV) into European Mediterranean countries in 1998, vaccination was used in an effort to minimize direct economic losses to animal production, reduce virus circulation and allow safe movements of animals from endemic areas. Vaccination strategies in different countries were developed according to their individual policies, the geographic distribution of the incurring serotypes of BTV and the availability of appropriate vaccines. Four monovalent modified live virus (MLV) vaccines were imported from South Africa and subsequently used extensively in both cattle and sheep. MLVs were found to be immunogenic and capable of generating strong protective immunity in vaccinated ruminants. Adverse side effects were principally evident in sheep. Specifically, some vaccinated sheep developed signs of clinical bluetongue with fever, facial oedema and lameness. Lactating sheep that developed fever also had reduced milk production. More severe clinical signs occurred in large numbers of sheep that were vaccinated with vaccine combinations containing the BTV-16 MLV, and the use of the monovalent BTV-16 MLV was discontinued as a consequence. Abortion occurred in <0.5% of vaccinated animals. The length of viraemia in sheep and cattle that received MLVs did not exceed 35 days, with the single notable exception of a cow vaccinated with a multivalent BTV-2, -4, -9 and -16 vaccine in which viraemia persisted at least 78 days. Viraemia of sufficient titre to infect Culicoides insects was observed transiently in MLV-vaccinated ruminants, and natural transmission of MLV strains has been confirmed. An inactivated vaccine was first developed against BTV-2 and used in the field. An inactivated vaccine against BTV-4 as well as a bivalent vaccine against serotypes 2 and 4 were subsequently developed and used in Corsica, Spain, Portugal and Italy. These inactivated vaccines were generally safe although on few occasions reactions occurred at the site of inoculation. Two doses of these BTV inactivated vaccines provided complete, long-lasting immunity against both clinical signs and viraemia, whereas a single immunization with the BTV-4 inactivated vaccine gave only partial reduction of viraemia in vaccinated cattle when challenged with the homologous BTV serotype. Additional BTV inactivated vaccines are currently under development, as well as new generation vaccines including recombinant vaccines.     

Failure of foetal protection after vaccination against an experimental infection with bovine virus diarrhea virus

A protocol is described to measure the protection of the bovine fetus against an experimental bovine virus diarrhea virus (BVDV) infection after vaccination. Two inactivated experimental vaccines were applied twice with a 3 week interval. A mixture of three different Dutch field strains was used as challenge on mainly the 82nd day of gestation to vaccinated and unvaccinated control animals. The challenge was applied 5 months after completion of the two-fold vaccinations. All calves born from unvaccinated control animals were persistently infected. The calves born from dams vaccinated with the two different inactivated BVDV vaccines were persistently infected in 78 and 60%, respectively.     

Vaccination of older Bos taurus bulls against bovine babesiosis

Two separate groups of Bos taurus bulls, one of 106 and the second of 27 animals, imported to Israel from areas free of Babesia bovis and Babesia bigemina, were vaccinated against babesiosis with a bivalent live attenuated vaccine. In light of the fact that routine vaccination is recommended at the weaning age, these bulls--of highly susceptible breeds--were kept under close surveillance to prevent losses that might be caused by severe clinical reactions to their vaccination at the age of 16-18 months. Seven days after vaccination, about one-third of the 106 bulls in the first group developed clinical signs of B. bigemina infection, which peaked at day 9, and then diminished from day 11, when the patent period known for B. bovis infection was observed. Because of the severe clinical responses a total of 36% of the bulls required babesicidal treatment. Despite the treatment Babesia were not sterilized: 33 and 68% of the animals remained PCR positive for B. bigemina and B. bovis, respectively. To mitigate the severe responses to vaccination, the 27 bulls of the second group were vaccinated in two-steps: they were inoculated initially with avirulent culture-derived parasites and then vaccinated with the conventional donor-derived vaccine a month later. None of the bulls in the latter group developed clinical babesiosis, all were serologically positive to B. bigemina, and 67% showed seroconversion to B. bovis. In light of the experience described here, it is suggested that sensitive older cattle be vaccinated against babesiosis by priming them with avirulent in vitro-cultured parasites and then inoculating them with the conventional donor-derived vaccines.     

Duration of immunity induced by an adjuvanted and inactivated equine influenza, tetanus and equine herpesvirus 1 and 4 combination vaccine

An adjuvanted vaccine containing inactivated equine influenza, herpesvirus antigens, and tetanus toxoid was administered to young seronegative foals of 8 months of age by deep intramuscular injection in the neck (Group A). The first two vaccinations were given 4 weeks apart. The third was administered 6 months later. Another group of foals (Group B) was vaccinated according to the same scheme at the same time with monovalent equine herpes virus (EHV) vaccine (EHV1.4) vaccine. Antibody responses to the equine influenza (single radial haemolysis; SRH) and tetanus (ToBi ELISA) components of the vaccines were examined from first vaccination until 1 year after the third vaccination. The influenza components of the combination vaccine induced high antibody titres at two weeks after the second vaccination whereafter titres declined until the time of the third vaccination. After the third vaccination, the titres rose rapidly again to remain high for at least 1 year. Antibody titres against tetanus peaked only after the third vaccination but remained high enough to offer protective immunity for at least 1 year. Foals vaccinated with monovalent EHV1.4 remained seronegative for influenza and tetanus throughout the study. Four and a half months after the third vaccination of groups A and B, a third group of animals was vaccinated twice with monovalent EHV1.4 vaccine 4 weeks apart (Group C). Two weeks after the administration of the second dose in the later group, all groups (A, B, C and an unvaccinated control group D) were challenged with EHV-4. Vaccinated foals (Group A, B, C) showed a clear reduction of clinical symptoms and virus excretion after EHV-4 challenge compared with the unvaccinated control foals. No difference could be demonstrated among the vaccinated groups, suggesting that the combination vaccine protects as well as the monovalent vaccine. In EHV1.4-vaccinated foals both antigenic fractions induced clear protection up to 6 months after vaccination (9). It can therefore be anticipated that the efficacy of the combination vaccine against EHV-1 challenge is similar to the efficacy against EHV-1 induced by EHV1.4 vaccination.     

The effects of challenge on the humoral and cellular immune responses in pseudorabies vaccinated swine.

The effects of challenge exposure on the humoral and cellular immune responses in pseudorabies vaccinated swine were studied in 84 barrows. The pigs were divided into seven groups and challenge exposed to a virulent strain of pseudorabies virus on months 1, 3, 5, 8, 10, 12 and 14 after vaccination. The pigs were vaccinated with commercial attenuated and inactivated pseudorabies virus vaccines. The protection conferred by vaccination was equally effective with both types of vaccines. The levels of cellular and humoral immunity after challenge exposure in pigs vaccinated with either type of vaccine were similar. The cell-mediated immune response can be effectively used for the early detection of pigs exposed to pseudorabies virus. Virus isolation attempts from the brain and spleen in most of the vaccinated pigs were unsuccessful.     

Immunisation against ovine caseous lymphadenitis: efficacy of monocomponent Corynebacterium pseudotuberculosis toxoid vaccine and combined clostridial-corynebacterial vaccines

Sheep were immunised with Corynebacterium pseudotuberculosis toxoid formulated as a monocomponent vaccine with aluminium adjuvant or in combination with 5 clostridial antigens, and also in the combined form with sodium selenate. Immunised and control sheep were experimentally infected 16 days after vaccination and slaughtered and inspected after a further 3 months to determine their resistance to infection. All 3 vaccines afforded an equal and high level of protection; 91% of vaccinated sheep exhibiting no lesions of caseous lymphadenitis compared with 51.5% affected sheep in the control group. Average lesion counts were 1.2 per affected vaccinated sheep and 4.5 per affected control sheep. Antitoxin responses to the clostridial toxoids incorporated in the combined vaccines were not affected by inclusion of the C pseudotuberculosis toxoid or the sodium selenate.     

Determination of duration of immunity of calves vaccinated with the Theileria annulata schizont cell culture vaccine

Bovine tropical theileriosis caused by Theileria annulata is a serious haemoprotozoan disease of cattle affecting exotic cattle, their crossbreeds and young indigenous calves. Cell culture vaccines have been developed and used effectively in various countries for the control of this disease. However, the duration of immunity provided by these vaccines is poorly understood. The present experiments were planned to study the duration of immunity in animals after vaccination with the T. annulata (Hisar) schizont cell culture vaccine. Two groups of calves were vaccinated and challenged after a period of 3 and 6 months, respectively. There was no fever in any of the vaccinated calves after challenge. However, the vaccinated animals exhibited mild to moderate enlargement of lymph nodes and parasitological reactions. The parasitological reactions were very mild in calves challenged after 3 months and moderate in calves challenged after 6 months. There was a mild but significant decrease in the haematological values of calves after challenge. A significant rise in the anti-theilerial antibody titres was observed in all calves after vaccination, which increased further, by many folds after challenge. On the other hand, all the challenge control calves showed symptoms of acute theileriosis and died. The observations suggested that the T. annulata (Hisar) schizont cell culture vaccine provided immunity in vaccinated animals for at least 6 months in the absence of field tick challenge. However, there was some decline in immunity after 6 months, if the animals are not exposed to ticks during this period.     

Response of Bali cattle (Bos javanicus) to vaccination with Brucella abortus strain 19 in West Timor

A trial was conducted in two villages (one containing cattle infected with brucellosis and one not containing infected cattle) in Timor, Indonesia to determine the serological response to vaccination with Brucella abortus strain 19 in Bali cattle (Bos javanicus) (n = 599). Mature female cattle were immunised with low-dose strain 19 (2x10(8)-6x10(8) colony forming units) and calves (6-12 months) with high-dose strain 19 (4x10(10)-12x10(10) colony forming units). Other mature females and calves were inoculated with sterile vaccine diluent and formed a non-vaccinated in-contact control group. The seroprevalence and mean titres were highest in the vaccinated cattle 3 months after vaccination. These then receded, however, 1% of vaccinated calves and 1.9% of vaccinated cows from the village without infected cattle were still seropositive on the complement-fixation test (CFT) 24 months after vaccination. Non-vaccinated seropositive animals were more likely to have aborted or had a stillbirth and were less likely to have produced a calf than were seronegative cows from the village containing infected animals. We concluded that strain 19 vaccine induced protection in Bali cattle and that this vaccine might play an important role in the control of bovine brucellosis in Timor.     

Assessment using ELISA of the herd immunity levels induced in cattle by foot-and-mouth disease oil vaccines

The development of a liquid-phase blocking sandwich ELISA (LPBE) to measure antibodies (Ab) produced in cattle with the O, A and C foot-and-mouth disease virus (FMDV) types of commercial vaccines used in Argentina is described. The test was specific: 99% of naïve cattle sera (n = 130) gave titres below log₁₀ = 1.2, and none had a titre above log₁₀ = 1.5. Comparative studies with serum neutralization test (SNT) using sera from cattle which received one or more vaccine doses is reported. The overall rank correlation coefficient (Spearman's , r_s) between SNT and LPBE were highly significant (r_s > 0.67, P < 0.0001) for all vaccine strains. LBPE Ab titres on sera collected 90 days post vaccination were compared with results of cattle protection tests by applying a logistic regression. The minimum Ab titres at which 85% and 75% of the cattle were protected for each FMDV type were determined in order to interpret field Ab data in terms of protection. Application of this method allows large scale serological examinations to monitor antibody levels in vaccinated animals as an indirect indicator of the FMD control program status in the field. Its use in the evaluation of commercial batches of FMD vaccine is discussed.     

山羊痘灭活疫苗免疫持续期试验

将实验室制备的3批山羊痘油佐剂灭活疫苗,分别免疫接种一定数量无羊痘抗体的山羊,山羊于免疫接种后4.5个月、7个月、9.5个月和12个月用AV40株强毒进行攻击。结果显示,3批疫苗接种的山羊免后4.5个月攻毒均100%保护,免后7个月攻毒平均80%保护,免后9.5个月攻毒平均60%保护。实验表明,此山羊痘灭活疫苗免疫后6个月能够维持较高的抗体水平,其免疫持续期可规定为6个月。     

Vaccines against infection with bovine viral diarrhea virus/mucosal disease (BVDV/MD): a short overview

Various vaccine preparations against an infection with Bovine Viral Diarrhea Virus (BVDV) have been used since more than 30 years. To prevent reproduction failure and the generation of persistently infected animals, protection of heifers and cows against transplacental infection is the most important aim of BVDV vaccination. In principal, BVD vaccines with replication competent, attenuated BVDV (modified live vaccines) and vaccines with inactivated BVDV preparations (killed vaccines) are used. In Germany, modified live vaccines as well as killed vaccines are registered, however, only BVDV type I strains are included in both types of vaccines. This paper presents an short overview about the different BVD vaccines and their efficacy and safety. In addition, new vaccine types are mentioned and final conclusions are drawn.