表达猪瘟病毒E2蛋白的重组腺病毒对猪的免疫效力评价

为了进一步验证含有猪瘟病毒E2基因的重组腺病毒（rAdV—E2）在猪体上的免疫效力,将rAdV—E2按108TCID50／头接种猪2次,同时用野生型腺病毒wtAdV作为阴性对照,当抗体上升到一定程度后用致死剂量的猪瘟强毒石门株进行攻击。结果表明,rAdV—E2免疫组（n=5）所有免疫猪在加强免疫后均产生了猪瘟特异性中和抗体,并于加强免疫后3w达到峰值,攻毒后所有猪只抗体迅速升高,除了一头猪短期体温升高外,未出现任何其它临床症状;而野生型腺病毒wtAdV免疫组（n=5）猪只在攻毒前一直没有检出特异性抗体,攻毒后全部出现典型的猪瘟临床症状和严重的病毒血症,剖检时可见典型猪瘟病理变化。这表明构建的猪瘟病毒E2基因重组腺病毒rAdV—E2免疫猪后产生了很好的免疫效果,有望成为具有开发价值的活载体疫苗。     

猪圆环病毒2型感染对猪瘟疫苗体液免疫应答的影响

采用ELISA方法对单独接种猪瘟疫苗组(CSFV组,n=3)、PCV2感染且出现病毒血症后接种猪瘟疫苗组(PCV2/CSFV组,n=3)及PCV2感染同时接种猪瘟疫苗组(CSFV/PCV2组,n=3)不同时相血清中的猪瘟抗体进行检测;并对PCV2感染对照组(PCV2组)及PCV2/CSFV和CSFV/PCV2组血清中PCV2特异的抗体和核酸分别进行ELISA和PCR检测.结果表明,在接种后52 d CSFV组血清中抗体的阻断值显著高于CSFV/PCV2组(P<0.05);接种后42 d和52 d CSFV组平均抗体效价明显高于PCV2/CSFV和CSFV/PCV2组,其中在52 d CSFV组抗体阳性率这100%(3/3)而PCV2/CSFV和CSFV/PCV2在相应时相抗体阳性率仅为67%(2/3).结果提示PCV2感染可在一定程度上抑制猪瘟疫苗特异性的抗体反应.     

Two newly developed Erns-based ELISAs allow the differentiation of Classical Swine Fever virus-infected from marker-vaccinated animals and the discrimination of pestivirus antibodies

New generations of Classical Swine Fever virus (CSFV) marker vaccines have recently been developed in order to make emergency vaccination in case of a CSF outbreak more feasible. However, the application of a marker vaccine is dependent on the availability of an accompanying discriminatory test allowing differentiation of infected from vaccinated animals (DIVA). CP7_E2alf, the most promising live marker vaccine candidate currently available, is a genetically modified Bovine Viral Diarrhea virus expressing the E2 glycoprotein of CSFV strain Alfort/187. The DIVA principle going along with CP7_E2alf is based on the detection of CSFV E^rns-specific antibodies that are raised in the host upon CSFV infection but not after vaccination with the marker vaccine. The aim of this study was to develop novel DIVA tests to be used in combination with CP7_E2alf. Two indirect ELISAs (one for screening, the other one for confirmation purposes) using bacterially expressed recombinant E^rns proteins were designed and evaluated. Both ELISAs detected CSFV-specific antibodies against a broad range of strains and genotypes, and as early as 10 days after infection. They were able to distinguish CSFV-infected pigs from pigs vaccinated with CP7_E2alf and allowed discrimination of antibodies against ruminant pestiviruses in both, sera from domestic pigs and wild boar. Sensitivity and specificity of the screening ELISA was ≥95%. Thus, the ELISAs represent promising DIVA diagnostic tools, as well as an alternative to traditional pestivirus antibody differentiation by serum neutralization test.     

The influence of maternal immunity on the efficacy of a classical swine fever vaccine against classical swine fever virus,genogroup 2.2, infection

In Thailand, where vaccination is routinely employed, there has been an increased incidence of chronic classical swine fever (CSF) outbreaks during the past decade. The major causative virus has been identified to be the moderate virulence, classical swine fever virus (CSFV) of the genogroup 2.2. An investigation was made into the efficacy of a CSF vaccine against this genogroup 2.2 challenge. Five-week-old pigs, grouped by their level of passive antibody titer were immunized with lapinized Chinese-strain CSF vaccine and challenged with CSFV genogroup 2.2, 13 days after vaccination. The group containing passive titers of lower than 64 at the time of immunization, had significantly higher number of CSFV-specific IFN-gamma secreting cells and was completely protected against the challenge. Interestingly, both cellular and antibody responses were inhibited in the pigs with the higher passive titer. Furthermore, following challenge, CSFV could be isolated from 50% of the pigs in this group. It was demonstrated that the CSF vaccine could induce complete protection in pigs, provided that the maternal derived titer at the time of vaccination was lower than 64. The result implied that an increase in CSFV outbreaks might be due to the inappropriate timing of vaccination as well as the nature of the CSFV genogroup 2.2.     

Immunomodulatory effect of swine CCL20 chemokine in DNA vaccination against CSFV

The objective of this work was to explore whether a plasmid expressing CCL20 chemokine could improve the immune response against CSFV in co-administration with a DNA vaccine expressing the E2 protein. The immunization of pigs with the DNA vaccine formulation, that contains swine CCL20 chemokine, resulted in the homogenous induction of detectable levels of CSFV antibodies at 36 days after the first injection. Remarkably, immunized animals with E2 DNA vaccine in co-administration with the plasmid containing swine CCL20 developed high titers of neutralizing antibodies against homologous and heterologous CSFV strains and were totally protected upon a lethal viral challenge (sterilizing protection). Our results confirm the role of CCL20 to increase antibody-mediated responses. At the same time suggest the ability of CCL20 to enhance the T helper cell response associated with the induction of neutralizing antibodies against CSFV in pigs previously reported. Systemic replication of virulent CSFV in vivo during the acute phase of infection induces type I IFN. Lower average values of IFN alpha were detected in the serum of pigs immunized with pE2 and pCCL20 at 3 days after challenge. The levels of IFN-alpha detected in pigs immunized with pE2 and principally in non-vaccinated challenged animals can be related to viral load in serum at 3 and 7 days post infection and the clinical signs observed. Our results emphasized the capacity of swine CCL20 chemokine to enhance cellular, humoral and anti viral response with an adjuvant effect in the immune response elicited by E2-DNA vaccination against CSFV. To our knowledge, this is the first report demonstrating the adjuvant effect of swine CCL20 to effectively enhance the potential of DNA vaccine in the immune induction and protection against virus challenge in swine infection model.     

Classical swine fever virus isolates from Cuba form a new subgenotype 1.4

Identification and classification of classical swine fever virus (CSFV) on the basis of nucleotide sequencing and phylogenetic analysis have become an important tool to study the epidemiology and to control CSF disease. According to phylogenetic analyses of short sequences from the 5′nontranslated region (150 nt) and the E2 (190 nt), most CSFV isolates from South and Central America have been assorted to the subgenotypes 1.1 and 1.3, while CSFV isolates from Cuba have been allocated to subgenotype 1.2. Here we demonstrate that determination and comparison of full-length E2 sequences as well as of the sequences encoding for N^pro, C, E^rns, E1 and E2 (3361 nt) do not support segregation of Cuban CSFV isolates to subgenotype 1.2. In fact, our analysis revealed that the Cuban isolates are more divergent from other so far known CSFV subgenotype 1 isolates and form a novel separate subgenotype that is proposed to be designated subgenotype 1.4.     

Generation and efficacy evaluation of a recombinant adenovirus expressing the E2 protein of classical swine fever virus

Classical swine fever virus (CSFV) is the causative agent of classical swine fever (CSF), which causes significant economic losses to the pig industry worldwide. The E2 glycoprotein of CSFV is the main target for neutralizing antibodies. This study was aimed to develop a recombinant human adenovirus type 5 expressing the CSFV E2 gene (rAdV-E2) and evaluate its efficacy in rabbits and pigs. The results showed that the rabbits and the pigs immunized with the rAdV-E2 developed high-level CSFV-specific neutralizing antibodies. The rAdV-E2-immunized rabbits were protected from fever induced by infection with C-strain, which is pathogenic to the rabbit, and the rAdV-E2-immunized pigs were protected from lethal challenge with highly virulent Shimen strain. This indicates that the recombinant adenovirus can be an attractive candidate vaccine for preventing CSF.     

A promising multiple-epitope recombinant vaccine against classical swine fever virus

Classical swine fever (CSF) is a highly contagious and often fatal disease of swine. It is caused by classical swine fever virus (CSFV), one of the members of the genus Pestivirus of the Flaviviridae family. The development of a safe and effective vaccine against the CSF is critical to pandemic control, this article shows a tandem-repeat multiple-epitope recombinant vaccine can protect pigs from CSFV challenge. That was composed as following: two copies each of glycoprotein E2 residues 693–707, 241–276 and 770–781, and two copies amino acid residues 1446–1460 of the non-structural protein NS2-3. In the challenge test, all of the swine vaccinated with Chinese vaccine strain (C-strain) were fully protected from a challenge with CSFV. However, after three successive vaccinations with the multiple-epitope recombinant vaccine, three out of five pigs were protected from challenge with CSFV (in terms of both clinical signs and viremia). These results demonstrate that multiple-epitope recombinant vaccine which carrying the major CSFV epitopes can induce a high level of epitope-specific antibodies and exhibit a protective capability that parallels induced by C-strain to a certain extent.     

Efficacy of a live attenuated vaccine in classical swine fever virus postnatally persistently infected pigs

Classical swine fever (CSF) causes major losses in pig farming, with various degrees of disease severity. Efficient live attenuated vaccines against classical swine fever virus (CSFV) are used routinely in endemic countries. However, despite intensive vaccination programs in these areas for more than 20 years, CSF has not been eradicated. Molecular epidemiology studies in these regions suggests that the virus circulating in the field has evolved under the positive selection pressure exerted by the immune response to the vaccine, leading to new attenuated viral variants. Recent work by our group demonstrated that a high proportion of persistently infected piglets can be generated by early postnatal infection with low and moderately virulent CSFV strains. Here, we studied the immune response to a hog cholera lapinised virus vaccine (HCLV), C-strain, in six-week-old persistently infected pigs following post-natal infection. CSFV-negative pigs were vaccinated as controls. The humoral and interferon gamma responses as well as the CSFV RNA loads were monitored for 21 days post-vaccination. No vaccine viral RNA was detected in the serum samples and tonsils from CSFV postnatally persistently infected pigs for 21 days post-vaccination. Furthermore, no E2-specific antibody response or neutralising antibody titres were shown in CSFV persistently infected vaccinated animals. Likewise, no of IFN-gamma producing cell response against CSFV or PHA was observed. To our knowledge, this is the first report demonstrating the absence of a response to vaccination in CSFV persistently infected pigs.     

Duration of the protection of an E2 subunit marker vaccine against classical swine fever after a single vaccination

The period during which pigs are protected after vaccination is important for the successful usage of a marker vaccine against classical swine fever virus (CSFV) in an eradication programme. In four animal experiments with different vaccination-challenge intervals we determined the duration of protection of an E2 subunit marker vaccine in pigs after a single vaccination. Unvaccinated pigs were included in each group to detect transmission of the challenge virus.Three groups of six pigs were vaccinated once and subsequently inoculated with the virulent CSFV strain Brescia after a vaccination-challenge interval of 3, 51/2, 6 or 13 months. All vaccinated pigs, 16 out of 18, with neutralising antibodies against CSFV at the moment of challenge, 3, 51/2, 6 or 13 months later, survived, whereas unvaccinated control pigs died from acute CSF or were killed being moribund. A proportion of the vaccinated pigs did however develop fever or cytopenia after challenge and two vaccinated pigs were viremic after challenge. Virus transmission of vaccinated and challenged pigs to unvaccinated sentinel pigs did not occur in groups of pigs which were challenged 3 or 6 months after a single vaccination. Two out of eight vaccinated pigs that were found negative for CSFV neutralising antibody at 13 months after vaccination died after subsequent challenge.The findings in this study demonstrate that pigs can be protected against a lethal challenge of CSFV for up to 13 months after a single vaccination with an E2 subunit marker vaccine.     

Development of a classical swine fever subunit marker vaccine and companion diagnostic test

The development of a classical swine fever (CSF) subunit marker vaccine, based on viral envelope glycoprotein E2, and a companion diagnostic test, based on a second viral envelope glycoprotein E(RNS), will be described. Important properties of the vaccine, such as onset and duration of immunity, and prevention of horizontal and vertical transmission of virus were evaluated. A single dose of the vaccine protected pigs against clinical signs of CSF, following intranasal challenge with 100LD(50) of virulent classical swine fever virus (CSFV) at 2 weeks after vaccination. However, challenge virus transmission to unvaccinated sentinels was not always completely inhibited at this time point. From 3 weeks up to 6 months after vaccination, pigs were protected against clinical signs of CSF, and no longer transmitted challenge virus to unvaccinated sentinels. In contrast, unvaccinated control pigs died within 2 weeks after challenge. We also evaluated transmission of challenge virus in a setup enabling determination of the reproduction ratio (R value) of the virus. In such an experiment, transmission of challenge virus is determined in a fully vaccinated population at different time points after vaccination. Pigs challenged at 1 week after immunization died of CSF, whereas the vaccinated sentinels became infected, seroconverted for E(RNS) antibodies, but survived. At 2 weeks after vaccination, the challenged pigs seroconverted for E(RNS) antibodies, but none of the vaccinated sentinels did. Thus, at 1 week after vaccination, R1, and at 2 weeks, R=0, implying no control or control of an outbreak, respectively. Vertical transmission of CSFV to the immune-incompetent fetus may lead to the birth of highly viraemic, persistently infected piglets which are one of the major sources of virus spread. Protection against transplacental transmission of CSFV in vaccinated sows was, therefore, tested in once and twice vaccinated sows. Only one out of nine once-vaccinated sows transmitted challenge virus to the fetus, whereas none of the nine twice-vaccinated sows did. Finally, our data show that the E(RNS) test detects CSFV-specific antibodies in vaccinated or unvaccinated pigs as early as 14 days after infection with a virulent CSF strain. This indicates that the E2 vaccine and companion test fully comply with the marker vaccine concept. This concept implies the possibility of detecting infected animals within a vaccinated population.     

Classical swine fever (CSF) marker vaccine. Trial I. Challenge studies in weaner pigs

Two commercial marker vaccines against classical swine fever virus (CSFV) and companion diagnostic tests were examined in 160 conventional pigs. To test the vaccines in a "worst case scenario", group of 10 weaners were vaccinated using a single dose of an E2 (gp55) based vaccine at days -21, -14, -10 or -7, and subsequently challenged at day 0. The challenge virus was CSFV 277, originating from a recent outbreak of classical swine fever (CSF) in Germany. In all groups, only 5 out of 10 pigs were challenged; the remaining 5 pigs served as vaccinated contact controls. Also, three control groups, each consisting of 10 non-vaccinated pigs, were challenged in parallel to the vaccinated animals. CSFV could be isolated from all non-vaccinated pigs. Among these pigs 40% displayed a chronic course of the infection (virus positive for more than 10 days). Pigs vaccinated 21 or 14 days before challenge displayed no clinical signs of CSFV after challenge. However, they were still able to replicate CSFV when challenged, as measured by reisolation of CSFV from leukocytes of the directly challenged pigs. CSFV could be isolated from the leucocytes of 25% of the pigs vaccinated 21 days before challenge and 50% of the pigs vaccinated 14 days before challenge. Chronic infection was not observed, but transmission to one vaccinated contact pig occurred. From all pigs vaccinated 10 or 7 days before challenge, CSFV could be reisolated. We observed a chronic course of infection in 5% of pigs vaccinated 10 days before challenge and in 30% of pigs vaccinated 7 days before challenge. The mortality rate was 20% in the pigs vaccinated 10 days before challenge, and varied between 20 and 80% in pigs vaccinated 7 days prior to challenge. The contact animals had lower mortality (0-20%) than directly challenged pigs, probably mirroring the delayed time point of infection. There was thus some protection against clinical illness by both marker vaccines, but not a solid protection against infection and virus shedding. The efficacy of the vaccine was best if used 3 weeks before challenge and a clear correlation between time interval from vaccination to challenge and the level of virus shedding was observed. Each vaccine had its own accompanying discriminatory ELISA, but 18% of the virus positive pigs never seroconverted in these tests.     

Npro of classical swine fever virus contributes to pathogenicity in pigs by preventing type I interferon induction at local replication sites

Classical swine fever (CSF) caused by CSF virus (CSFV) is a highly contagious disease of pigs. The viral protein N^pro of CSFV interferes with alpha- and beta-interferon (IFN-α/β) induction by promoting the degradation of interferon regulatory factor 3 (IRF3). During the establishment of the live attenuated CSF vaccine strain GPE^-, N^pro acquired a mutation that abolished its capacity to bind and degrade IRF3, rendering it unable to prevent IFN-α/β induction. In a previous study, we showed that the GPE^- vaccine virus became pathogenic after forced serial passages in pigs, which was attributed to the amino acid substitutions T830A in the viral proteins E2 and V2475A and A2563V in NS4B. Interestingly, during the re-adaptation of the GPE^- vaccine virus in pigs, the IRF3-degrading function of N^pro was not recovered. Therefore, we examined whether restoring the ability of N^pro to block IFN-α/β induction of both the avirulent and moderately virulent GPE^--derived virus would enhance pathogenicity in pigs. Viruses carrying the N136D substitution in N^pro regained the ability to degrade IRF3 and suppress IFN-α/β induction in vitro. In pigs, functional N^pro significantly reduced the local IFN-α mRNA expression in lymphoid organs while it increased quantities of IFN-α/β in the circulation, and enhanced pathogenicity of the moderately virulent virus. In conclusion, the present study demonstrates that functional N^pro influences the innate immune response at local sites of virus replication in pigs and contributes to pathogenicity of CSFV in synergy with viral replication.     

Phylogenetic analysis of recent classical swine fever virus (CSFV) isolates from Assam, India

Classical swine fever (CSF), a highly contagious viral disease of pigs, is endemic in India. As there is no information concerning the accurate genetic typing of classical swine fever virus (CSFV) isolates in India, 16 CSF viruses isolated during 2005-2007 from domestic pigs in different districts of Assam were typed in 5′ UTR (150 nucleotides). To confirm the genetic typing results and to study the genetic variability, selected viruses were also analyzed in E2 (190 nt) and NS5B gene (409 nt) regions. Phylogenetic analysis revealed that all the 16 CSFV isolates analyzed belonged to group 1 and subgroup 1.1 in contrast to the situation in other Asian countries. Additionally, analysis in E2 and NS5B region placed the Indian isolates in a clearly separated clade within subgroup 1.1. The results suggest that subgroup 1.1 CSF viruses are currently circulating in India, which is important for epidemiology and control of CSF.     

Vaccination of weaner pigs against classical swine fever with the subunit vaccine "Porcilis Pesti": influence of different immunization plans on excretion and transmission of challenge virus

Excretion and transmission of CSFV after vaccination with the CSF subunit marker vaccine "Porcilis Pesti" have been studied using the following different vaccination schedules: Group A--two vaccinations with an interval of 28 d, challenge 14 d after second vaccination (p.v2.); group B--two vaccinations with an interval of 14 d, challenge 14 d later; group C--two vaccinations with an interval of 28 d, challenge at time of booster vaccination; group D--two vaccinations with an interval of 14 d, challenge 7 d p.v2.; group E--single vaccination and infection 14 d later. After infection one sentinel pig was added to the vaccinated and infected pigs of each group. A single vaccination did not induce protective immunity against a CSFV challenge. Double vaccination at a four-week interval protected piglets from clinical infection, and neither viraemia and leukopenia nor virus excretion were detected if infected 14 d p.v2. Two vaccinations at a two-week interval followed by a challenge 7 d p.v2. led to a short viraemia on day 5 p.i. but without excretion of CSFV. Though all other vaccination schedules induced a reduction in virus shedding and a decrease in CSFV replication, in all these cases in-contact controls became infected. The results of transmission of CSFV are discussed in relation to a potential use of subunit marker vaccines in CSF control.     

Characterization of C-strain "Riems" TAV-epitope escape variants obtained through selective antibody pressure in cell culture

ABSTRACT: Classical swine fever virus (CSFV) C-strain "Riems" escape variants generated under selective antibody pressure with monoclonal antibodies and a peptide-specific antiserum in cell culture were investigated. Candidates with up to three amino acid exchanges in the immunodominant and highly conserved linear TAV-epitope of the E2-glycoprotein, and additional mutations in the envelope proteins ERNS and E1, were characterized both in vitro and in vivo.It was further demonstrated, that intramuscular immunization of weaner pigs with variants selected after a series of passages elicited full protection against lethal CSFV challenge infection. These novel CSFV C-strain variants with exchanges in the TAV-epitope present potential marker vaccine candidates. The DIVA (differentiating infected from vaccinated animals) principle was tested for those variants using commercially available E2 antibody detection ELISA. Moreover, direct virus differentiation is possible using a real-time RT-PCR system specific for the new C-strain virus escape variants or using differential immunofluorescence staining.     

猪瘟疫苗在猪圆环病毒2型阳性猪场的免疫效果观察

为了研究猪圆环病毒2型(PCV-2)感染对猪瘟疫苗免疫效力的影响,对PCR证实为PCV-2阳性的试验猪进行猪瘟疫苗的免疫,分别在免疫后第1、3、7、14、21、28和63天对试验猪进行猪瘟病毒(CSFV)和PCV-2的抗体检测。检测结果表明PCV-2阳性猪在猪瘟疫苗免疫后均未能产生有效的CSFV抗体,从免疫猪的血液和内脏组织中也未能检测到CSFV核酸。虽然只能从1头PCV-2阳性猪的血清中检测到PCV-2抗体,但是却能从全部实验猪的淋巴结中检测到PCV-2的核酸。试验猪的病理组织学观察和白细胞计数也表明PCV-2阳性猪的淋巴结呈典型的PCV-2感染的病理变化,且白细胞数量显著低于健康猪。表明PCV-2的感染会对猪的免疫系统造成损害从而抑制猪瘟疫苗的免疫效果。     

Cytokine and immunoglobulin isotype profiles during CP7_E2alf vaccination against a challenge with the highly virulent Koslov strain of classical swine fever virus

CP7_E2alf is a promising marker vaccine candidate against classical swine fever (CSF). To better understand the mechanisms of protection, cytokine and isotype-specific antibody profiles were investigated in CP7_E2alf vaccinated pigs before and after challenge with the highly virulent CSFV strain “Koslov” at 14 days or 6 months post-vaccination. The interference of vaccination with CSFV pathogeny-related cytokine responses, previously described following a moderately virulent challenge, was confirmed. However, the levels of additional cytokines, TNF-α and IL-6, were significantly attenuated by vaccination following highly virulent challenge. This vaccine interference with cytokine response was not dependent on the immunization route or the consequence of competition between vaccine and challenge strain. Interestingly, IFN-γ enhancement and persistent high IgG2 levels suggested an important role of cell-mediated immunity in long-term protection against CSFV induced by CP7_E2alf vaccination. IgA production also revealed a stimulation of mucosal immunity, especially after oral administration of the vaccine.     

A prime-boost vaccination strategy using naked DNA followed by recombinant porcine adenovirus protects pigs from classical swine fever

Weaned pigs (6-week-old) and 7-day-old pre-weaned piglets were vaccinated with naked plasmid DNA expressing the gp55/E2 gene from classical swine fever virus (CSFV). Both groups of pigs were then given a booster dose of recombinant porcine adenovirus expressing the gp55 gene (rPAV-gp55). Following challenge with CSFV, 100% of weaned pigs and 75% pre-weaned piglets were protected from disease. Weaned pigs given a single dose of rPAV-gp55 were also protected, but showed a slight increase in temperature immediately post-challenge. However, weaned animals given a DNA prime before rPAV-gp55 showed no fluctuation in body temperature following challenge and no pathology in spleen or lymph nodes upon post-mortem. In addition, no CSFV could be re-isolated from the rPAV vaccinated group and from only one pig in the prime-boost group following challenge, suggesting that both vaccination regimes have the potential to reduce or prevent virus shedding following experimental challenge.     

无针注射器接种猪瘟活疫苗对猪免疫效果评价

为了评定无针注射器接种猪瘟活疫苗的免疫效果,将300头非免仔猪随机分为6个组,其中3组用无针注射器分别免疫1头份、1/2头份剂量的瘟倍安以及1头份剂量的STTM猪瘟活疫苗,剩下的3组将无针注射器替换成传统的有针注射器进行免疫。30日龄进行首次免疫,55日龄进行二次免疫,免疫后一周内观察猪有无不良反应。首免后第14天、二免后第25天分别采血、分离血清,ELISA试剂盒检测CSFV抗体,计算每组猪抗体阻断率及免疫合格率,统计分析各组之间的差异。实验结果显示,无针注射器与有针注射器接种疫苗均未对猪精神状态、采食、运动造成影响,无针注射器接种部位炎症发生率也低于有针注射器;无针注射器免疫组抗体滴度明显高于有针注射器接种组,即使疫苗使用剂量减半也能达到很好的免疫效果。