鸡传染性法氏囊病K株活疫苗的免疫实验

鸡传染性法氏囊病 ( IBD)是由鸡传染性法氏囊病病毒引起的一种以破坏鸡的重要免疫器官 -法氏囊为主的急性接触性传染病。每年对养鸡业都造成很大的损失。为了更好的防治本病 ,黑龙江化血研生物技术有限公司从日本国引进了新的法氏囊 K株活疫苗种毒 ,在该公司 GMP车间生产条件下     

Use of the caprinised strain of rinderpest virus for potency testing an attenuated cell culture rinderpest vaccine

The caprinised strain of rinderpest virus was inoculated into goats to produce a challenge stock. These goats were kept with control animals (goats, sheep, calves). In this trial the caprinised strain was shown to have a mild pathogenicity for goats and it spread to one of two contact goats but not from goats to other species. The caprinised strain was then tested on cattle where a febrile reaction was observed. The caprinised strain also did not spread between cattle. The cattle vaccinated with a freeze-dried vaccine produced from the attenuated Kabete RBKO strain on bovine kidney cells were then challenged with the caprinised strain with good results.     

Retrospective genome analysis of a live vaccine strain of bovine viral diarrhea virus

A live bovine viral diarrhea (BVDV) vaccine, marketed as a derivate of the Oregon C24V strain, was used between the end of the 1960s and the beginning of the 1990s in Central Europe. Since laboratory investigations of mucosal disease cases in vaccinated animals suggested recombinations between the vaccine and wild type variants of BVDV, and recombinational nucleotide sequences seemed distinct from BVDV Oregon C24V, the aim of the present retrospective study was to analyze the genomes of pre-registration (termed here BVDV-Xpre) and of marketed (BVDV-X) batches of the vaccine. The results of the complete genome analysis of BVDV-Xpre confirmed that the original virus strain used at the start of the vaccine production was Oregon C24V. Surprisingly, the analysis of the complete nucleotide sequence of the BVDV-X marketed vaccine revealed that this strain belongs to the BVDV 1b subgroup, with a 93.7% nucleotide sequence homology to BVDV reference strain Osloss. The homology to BVDV Oregon C24V was significantly lower (77.4%), and a thorough sequence scanning showed that the genome of BVDV-X had not derived from Oregon C24V. These data indicate the very likely scenario that a strain different to Oregon C24V was picked up during the in vitro or in vivo passages for vaccine development. Despite of the virus-switch, the BVDV-X vaccine continuously maintained its innocuity and efficacy, as proven by the regular quality testing data, and the presence of the foreign virus remained unnoticed over many years. The results of this work emphasize that the contamination of commercially available live vaccines with exogenous BVDV strains is a real risk factor, and a unequivocal analysis, including molecular methods, is needed to verify their authenticity.     

Establishment of an attenuated strain of bovine respiratory syncytial virus for live virus vaccine

To develop a live virus vaccine for the prevention of bovine respiratory syncytial (BRS) virus infection in calves, an attempt was made to produce an attenuated virus. The RS-52 strain of BRS virus, isolated from the nasal secretions of a naturally infected calf, was subjected to serial passages in adult hamster lung established (HAL) cells at 30 degrees C and the attenuated rs-52 strain as a live virus vaccine was established. The rs-52 strain multiplied better at 30 degrees C than at 34 or 37 degrees C in HAL cells. The differences in the highest virus titers of this strain between the culture temperature of 30 degrees C and that of 34 or 37 degrees C were more than 2.25 log TCID50. Colostrum-deprived newborn calves and 2 approximately 4 months old calves inoculated with the rs-52 strain manifested no abnormal clinical sings at all. However, all inoculated calves produced serum neutralization antibody. When the colostrum-deprived newborn calves immunized with the rs-52 strain were challenged with the virulent NMK7 strain of BRS virus, they exhibited no pyrexia or other abnormal clinical signs at all. An attempt was made to recover the virus from nasal secretions of these calves, but in vain. On the other hand, a nonimmunized control colostrum-deprived newborn calf developed slight fever, mild cough, and slight serous nasal discharge after challenge exposure. The virus was recovered from nasal secretions of this calf. From these results, it was considered that the rs-52 strain could be used as an attenuated live virus vaccine for prevention of BRS virus infection.     

The shedding of a virulent Kabete O strain of rinderpest virus by cattle

A Muguga substrain of the virulent Kabete O strain of rinderpest virus was demonstrated in the ocular, nasal, oral and rectal swabs collected from infected cattle. Ocular shedding was detected at the onset of viraemia and before the onset of clinical signs whilst virus shedding in nasal, oral and rectal discharges appeared at the same time as lesions. It is suggested that virus isolation from ocular and nasal swabs should be considered in the diagnosis of rinderpest in addition to the other methods currently employed, as virus was isolated from swabs collected from dead animals.     

鸡传染性支气管炎弱毒疫苗株安全性和免疫效力初步评价

通过对QX基因型IBV分离株SDZB0808进行鸡胚连续100次传代致弱后获得子代病毒P100。为了明确P100的的致弱效果和免疫原性,对其进行了安全性和免疫效力评价。安全性试验结果显示,P100以105.5 EID50/只的剂量对3日龄的SPF鸡进行免疫后试验,与正常对照组相比没有明显临床症状和病理变化,气管和肾脏组织也没有病理组织损伤。免疫效力试验结果发现,P100以104.5 EID50/只的剂量免疫3日龄SPF鸡,14d后对同源强毒SDZB0808和异源强毒SDIB821/2012的攻击都具有100%的临床保护,病理组织学检查发现P100免疫攻毒组试验鸡气管和肾脏与正常对照没有差异,排毒检测结果显示P100免疫攻毒组试验鸡内脏组织病毒检出率大大低于攻毒对照组。本研究结果表明P100对SPF鸡具有良好的安全性和免疫效力,可以作为IBV弱毒疫苗候选株。     

Evaluation of a modified live virus type-1a bovine viral diarrhea virus vaccine (Singer strain) against a type-2 (strain 890) challenge

Both type-1 and type-2 bovine viral diarrhea virus (BVDV) infections are responsible for major losses in the cattle industry. However, several commercial BVDV vaccines contain only a type-1 strain. A vaccine trial was conducted to evaluate the efficacy of BVDV type-1 (Singer strain; BVDV-1) vaccine for protecting calves challenged with virulent BVDV type-2 (890 strain; BVDV-2). Thirty-eight BVDV-negative calves were randomly allocated to four groups. One group was treated with a modified live virus (MLV) BVDV-1 vaccine by i.m. injection and another group was treated with the same vaccine by s.c. injection. Two groups served as nonvaccinated controls (one i.m. and one s.c.). Twenty-eight days following vaccination, the calves were challenged with BVDV-2 and monitored for 21 days. Clinical scores and body temperatures of vaccinated calves were significantly (P<.05) lower than for controls on several days, and peak differences occurred 8 days after challenge. The control calves had significantly (P<.05) lower leukocyte counts 3 through 8 days after challenge; leukocyte counts for vaccinated animals did not decline significantly from prechallenge levels. There were no differences in protection between the i.m. and s.c. routes of vaccination. The study demonstrated satisfactory cross protection of the BVDV-1 vaccine against BVDV-2 challenge.     

Efficacy of Fostera PRRS modified live virus vaccine against a Canadian heterologous virulent field strain of porcine reproductive and respiratory syndrome virus

Vaccination is a useful option to control infection with porcine reproductive and respiratory syndrome virus (PRRSV), and several modified live-PRRSV vaccines have been developed. These vaccines have shown some efficacy in reducing the incidence and severity of clinical disease as well as the duration of viremia and virus shedding but have failed to provide sterilizing immunity. The efficacy of modified live-virus (MLV) vaccines is greater against a homologous strain compared with heterologous PRRSV strains. The objective of this study was to evaluate the efficacy of Fostera PRRS MLV vaccine in protecting against challenge with a heterologous field strain widely circulating in the swine herds of eastern Canada. Forty-six piglets were divided into 4 groups: nonvaccinated-nonchallenged; nonvaccinated-challenged; vaccinated-challenged; and vaccinated-nonchallenged. The animals were vaccinated at 23 d of age with Fostera PRRS and challenged 23 d later with a heterologous field strain of PRRSV (FMV12-1425619). Overall, the vaccine showed some beneficial effects in the challenged animals by reducing the severity of clinical signs and the viral load. A significant difference between nonvaccinated and vaccinated animals was detected for some parameters starting 11 to 13 d after challenge, which suggested that the cell-mediated immune response or other delayed responses could be more important than pre-existing PRRSV antibodies in vaccinated animals within the context of protection against heterologous strains.     

Detection of wild-type Aujeszky's disease virus by polymerase chain reaction in sheep vaccinated with a modified live vaccine strain

An outbreak of Aujeszky's disease occurred in a flock of sheep which had been housed together with pigs. After the death of five sheep with clinical signs of Aujeszky's disease, the remaining sheep were vaccinated with the Bartha vaccine strain, and the pigs were vaccinated with the 783 vaccine strain of Aujeszky's disease virus. Despite vaccination, however, more sheep died. Brain tissues from four sheep were collected for virus isolation and for immunobistological examinations. Only vaccine virus (gE-negative) was detected in the tissue. After DNA restriction enzyme analysis of the isolated virus, DNA of one or both of the vaccine strains was detected in all sheep. In one sheep field virus DNA was also detected. However, when the polymerase chain reaction was performed on samples prepared from paraffin-embedded tissues, DNA of field virus (gE-positive) was detected in all four sheep. It was probable that the sheep had not yet mounted a sufficient immune response to the vaccine virus, or were already infected with field virus at the time of vaccination. We concluded that the sheep died from field virus infection and not from vaccine virus infection and that only the polymerase chain reaction made it possible to specifically detect even very small amounts of field virus DNA among vaccine virus DNA in all investigated sheep.     

Detection of bovine virus diarrhea virus in a live bovine herpes virus 1 marker vaccine

In February 1999, 12 Dutch herds were vaccinated with a live bovine herpesvirus 1 vaccine from which bovine virus diarrhea virus (BVDV) could be isolated. All vaccine batches that were on the Dutch market and that had not yet reached the expiry date were tested for BVDV. In total, seven of 82 batches tested were found positive. Batch numbers TX3607, VB3914, VB3915, VB4046, TW3391, and TV3294 were positive for BVDV type 1, and batch number WG4622 was positive for BVDV type 2. This latter batch induced clinical signs of BVDV in an animal experiment with susceptible animals.     

Derivation and characterization of a live attenuated equine influenza vaccine virus

OBJECTIVE: To develop and characterize a cold-adapted live attenuated equine-2 influenza virus effective as an intranasal vaccine. ANIMALS: 8 ponies approximately 18 months of age. PROCEDURES: A wild-type equine-2 virus, A/Equine/Kentucky/1/91 (H3N8), was serially passaged in embryonated chicken eggs at temperatures gradually reduced in a stepwise manner from 34 C to 30 C to 28 C to 26 C. At different passages, infected allantoic fluids were tested for the ability of progeny virus to replicate in Madin-Darby canine kidney (MDCK) cells at 34 C and 39.5 C. Virus clones that replicated at 26 C in eggs and at 34 C in MDCK cells, but not at 39.5 C in MDCK cells, were tested for stability of the cold-adapted, temperature-sensitive (ts), and protein synthesis phenotypes. A stable clone, P821, was evaluated for safety, ability to replicate, and immunogenicity after intranasal administration in ponies. RESULTS: Randomly selected clones from the 49th passage were all ts with plaquing efficiencies of < 10(-6) (ratio of 39.5 C:34 C) and retained this phenotype after 5 serial passages at 34 C in either embryonated eggs or MDCK cells. The clone selected as the vaccine candidate (P821) had the desired degree of attenuation. Administered intranasally to seronegative ponies, the virus caused no adverse reactions or overt signs of clinical disease, replicated in the upper portion of the respiratory tract, and induced a strong serum antibody response. CONCLUSION AND CLINICAL RELEVANCE: A candidate live attenuated influenza vaccine virus was derived by cold-adaptation of a wild-type equine-2 influenza virus, A/Equine/Kentucky/1/91, in embryonated eggs.     

Studies on failure of T strain live Babesia bovis vaccine

SUMMARY Field investigations of the protection afforded by the Australian live Babesia bovis vaccine used in the early 1990s (T strain) revealed inadequate vaccine-induced protection in certain herds. Vaccination/challenge trials using 207 experimental cattle were conducted to evaluate the protection afforded by T strain B bovis against field isolates from these herds. The trials investigated whether isolates that could ‘break-through’ T strain immunity were present in the field, the ability or inability of specific cattle to develop protective immunity after vaccination with T strain and the effect of attenuation and maintenance procedures on the immunogenicity of T strain. The results showed that B bovis parasites present early in the process of attenuation of T strain were more protective than those remaining late in the process. They also showed that cattle from properties experiencing vaccine failures were less protected by T strain vaccination than Bos taurus cattle randomly selected from the general population if vaccinated with highly attenuated T strain. A hypothesis is offered to explain these findings .     

Standardization of large scale production of homologous live attenuated PPR vaccine in India

Live attenuated homologous vaccine against peste des petits ruminants of sheep and goats was produced on a large scale basis in roller culture bottles using seed virus developed at the Indian Veterinary Research Institute, Muktheswar, India. Vero cells between 130–150 passages with six percent foetal calf serum were used for the production of vaccine. The cells were infected with 0.01 multiplicity of infection and harvested when the cytopathic effect was 80%. The vaccine was freezedried in order to maintain the stability of the vaccine. Identity test and titration was performed and the vaccine titre was monitored to be minimum of 10⁵/100 doses. In-house sterility tests and quality control tests using experimental animals and small ruminants were performed. The vacuum and moisture content of the vaccine were also regulated to be within the normal limits.