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1.
The effect of low-dose challenge of immunity with pseudorabies virus (PRV) on subunit-vaccinated pigs was studied in 2 experiments. In the first experiment, we studied the effect of challenge dose on the antibody response to an early excreted 98-kilodalton PRV-glycoprotein that was used as a diagnostic antigen in the ELISA. In the second experiment, we studied the effect of low doses of virus on the establishment of latent infections in subunit-vaccinated pigs. The relationship of virus exposure dose and vaccine dose to the response of pigs to diagnostic antigen was studied in 18 pigs. Two groups of 3 pigs were vaccinated with a total of 200 micrograms of a lectin-derived PRV subunit vaccine over a 5-week period. Two groups of 3 pigs were similarly vaccinated with a total of 100 micrograms. Two groups of 3 pigs served as nonvaccinated controls. One group of pigs from each of the preceding categories was intranasally exposed to 10(6.0) and 10(2.7) plaque-forming units (PFU) of virus. Antibody to diagnostic antigen was detected by the ELISA and radioimmunoprecipitation 3 to 7 days earlier in pigs exposed to 10(6.0) PFU, demonstrating that the size of the virus challenge dose affects the antibody response to diagnostic antigen. The establishment of latent infections by low PRV doses and the ability to detect these infections was studied in 10 subunit-vaccinated pigs. Each pig was intranasally exposed to 10(2.3) PFU of virus (day 0).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

2.
The ability of pseudorabies virus (PRV) to infect and establish latency in pigs with passively acquired (maternal) antibody for PRV was tested by exposing such pigs to the virus and subsequently attempting to reactivate latent virus by administering large doses of dexamethasone. Pigs of each of 4 litters that had nursed gilts with relatively high (512, gilts 1 and 2), moderate (32, gilt 3), and no (less than 2, gilt 4) serum titers of virus-neutralizing (VN) antibodies for PRV were allotted to 3 treatment groups (A, B, C) when they were 2 weeks old. Group-A pigs were separated from littermates and dam and thereafter kept in isolation; group-B pigs were experimentally exposed oronasally to PRV and 1 hour later returned to their dam; group-C pigs were kept with their dam and potentially exposed to PRV by contact with littermates of group B. Sera obtained from pigs at selected intervals until they were 17 weeks old were tested for VN activity and for precipitating activity for radiolabeled viral proteins. All group-A pigs remained clinically normal throughout the experiment. Depending on the initial amount of passively acquired antibody, little or no serum VN or precipitating activity remained by the time these pigs were 17 weeks old. Group-B and -C pigs, with relatively high amounts of passively acquired antibody when exposed to PRV, also remained clinically normal. However, most became latently infected as subsequently evidenced by either dexamethasone-induced or noninduced virus reactivation. Noninduced reactivation may have been initiated by weaning the pigs when they were about 8 weeks old.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

3.
It has recently been shown that the antibody response to glycoprotein I (gI) of Aujeszky's disease virus can be used to distinguish infected from vaccinated pigs. To examine whether pigs exposed to low doses of a mildly virulent strain of Aujeszky's disease virus produce antibody to gI four groups of four pigs were inoculated intranasally with 10, 10(2), 10(3) or 10(4) plaque forming units (PFU) of the Sterksel strain. Two unvaccinated pigs and two pigs vaccinated intranasally with Bartha's K strain, a gI-negative vaccine, were placed in contact with each group. The pigs given 10 PFU and the in-contact pigs in this group did not become infected. The inoculated and the unvaccinated in-contact pigs in the other groups developed mild signs of illness and produced antibody to gI. Four of six vaccinated in-contact pigs that became infected showed neither clinical signs nor virus shedding and still produced antibody to gI. The other two vaccinated pigs appeared to be resistant to contact-challenge. The antibody response to gI persisted for at least seven months. These results support the idea that Aujeszky's disease virus may be eradicated by a programme based on vaccination with gI-negative vaccines, in conjunction with the detection and subsequent removal of gI-antibody positive, infected, pigs.  相似文献   

4.
A pseudorabies virus (PRV) mutant with deletions in genes for glycoprotein X (gX) and thymidine kinase, designated delta GX delta TK, was constructed and evaluated as a vaccine for protecting swine against PRV-induced mortality. Doses greater than or equal to 10(3) plaque-forming units (PFU) of this strain given to mice provided protection from challenge exposure with virulent PRV. Sera tested from mice inoculated with delta GX delta TK had high titers of neutralizing antibody to PRV, but reactivity in the same sera was not significantly different from that in sera from noninoculated mice (controls) when sera from both groups were evaluated by use of an ELISA with gX antigen produced in Escherichia coli. Compared with noninoculated pigs (controls), those given delta GX delta TK (greater than or equal to 10(2) PFU) were protected completely from lethal challenge exposure, without experiencing adverse effects on weight gain and with reduction of shedding of virulent challenge virus. Serotest results indicated that, although inoculated pigs responded with strong neutralizing antibody titers, the response of delta GX delta TK-inoculated pigs to gX, as determined by ELISA before challenge exposure, was not significantly greater than the ELISA values obtained from control pigs. The ELISA values from a group of pigs inoculated with a commercially available vaccine were significantly (P less than 0.05) higher than those of control pigs. The experimental vaccine, delta GX delta TK, was avirulent for mice, swine, and sheep, but was mildly virulent for calves (mortality, 1 of 12) and more virulent for dogs (mortality, 3 of 6) and cats (mortality, 2 of 6).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
Evaluation in swine of a subunit vaccine against pseudorabies   总被引：2，自引：0，他引：2  
A subunit vaccine against pseudorabies virus (PRV) was prepared by treating a mixture of pelleted virions and infected cells with the nonionic detergent Nonidet P-40 and emulsifying the extracted proteins incomplete Freund's adjuvant. Three 7-week-old pigs without antibodies against PRV were given 2 IM doses of this vaccine 3 weeks apart. Thirty days after the 2nd vaccination, 10(6) median tissue culture infective doses (TCID50) of a virulent strain of PRV were administered intranasally. Tonsillar and nasal swabs were collected daily between 2 and 10 days after challenge exposure. The pigs vaccinated with the subunit vaccine were not found to shed virulent PRV. Two groups of five 7-week-old pigs vaccinated with commercially available vaccines, either live-modified or inactivated virus, and subsequently exposed to 10(6) TCID50 of virulent PRV, shed virulent virus for up to 8 days. The subunit vaccine induced significantly higher virus-neutralizing antibody titers than either the live-modified or inactivated virus vaccine.  相似文献   

6.
Pigs (9 [+/- 1] weeks old) were inoculated with Streptococcus suis type 2, pseudorabies virus (PRV), or both. For each pig of groups A, B, and C the inoculum of S suis was 10(9) colony-forming units. For each pig of groups A, B, and D the inoculum of PRV was 5 x 10(3) TCID50 of either PRV strain 4892 (group A, n = 9) or PRV isolate B (group B, n = 9). The PRV strain 4892 is a highly virulent strain; isolate B causes mild clinical signs of infection in inoculated pigs. Group-C pigs (n = 9) were given S suis alone, and group-D pigs (n = 3) were inoculated only with PRV isolate B. Clinical signs of infection and development of lesions were readily seen in pigs of groups A, B, and C. Duration and severity of clinical signs of disease and lesions were reduced in pigs of group C, compared with those of the other 2 groups. Lesions, such as polyarthritis and fibrinous pericarditis, were more abundant and acute in the groups of pigs given mixed challenge exposure, compared with pigs inoculated exclusively with S suis type 2 (group C). The group of pigs inoculated with PRV isolate B alone did not manifest clinical signs of disease or lesions. Average daily gain for group-C pigs was higher, compared with that of other groups; the difference was statistically significant at P less than 0.02 and P less than 0.05 for groups B and D, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

7.
The aim of this study was to investigate the effects of a porcine reproductive and respiratory syndrome virus (PRRSV) infection on the development of the immune response after pseudorabies virus (PRV) vaccination in pigs. Pigs were intranasally inoculated with the European PRRSV strain, Lelystad virus ter Huurne, and were vaccinated intramuscularly with PRV 2 weeks later (LV-PRV group). Control pigs were vaccinated with PRV only (PRV group). Eight weeks after PRV vaccination, pigs from both groups were challenged intranasally with wild-type PRV. We measured the lymphoproliferative, and the cytolytic responses to PRV of peripheral blood mononuclear cells (PBMC), isolated from blood samples. In addition, serum samples were examined for antibodies against PRV and LV. One week after PRV vaccination, PBMC proliferated abundantly to PRV in both groups. However, in the LV-PRV group the lymphoproliferative response declined after 1 week, whereas, in the PRV group, the lymphoproliferative response was high for 3 weeks and declined thereafter (P<0.05). After challenge, the lymphoproliferative response was 1 week earlier and was consistently and significantly higher in the PRV group than in the LV-PRV group. The PRV-specific killing was higher at 3 weeks after PRV vaccination and 5 weeks after PRV challenge 19+/-3 and 24+/-6%, respectively, in the PRV group, compared to 7+/-4 and 6+/-9%, respectively, in the LV-PRV group (P<0.05). However, later after vaccination and challenge the cytolytic response was identical in both groups. The antibody titre against PRV developed equally in both groups. After challenge, no PRV virus was isolated from both groups. From these results we conclude that, although PRRSV infection did cause changes in the time course of the T-lymphocyte response after PRV vaccination, PRRSV infection did not inhibit the development of vaccine-induced protection after PRV.  相似文献   

8.
Latency of pseudorabies virus (PRV) was established in 8 of 9 pigs born to 2 vaccinated sows. Pigs had high, low, or no maternal antibody titers at the time of the initial inoculation. At postinoculation months 3 to 4, latent PRV could be reactivated in vivo by the administration of large doses of corticosteroids. In most pigs, the stress-simulating treatment resulted in recrudescence of virus shedding after lag periods of 4 to 11 days. In 3 pigs, virus shedding was without clinical signs of disease, whereas clinical signs that developed in 4 pigs appeared to be due to the corticosteroid treatment, rather than to the reactivation of PRV. Pigs with a log10 neutralizing antibody titer of less than or equal to 2.55 at the onset of corticosteroid treatment had a booster response. Reactivated PRV spread to sentinel pigs housed with the inoculated pigs. Reactivation of PRV was also demonstrated in vitro. Explant cultures of trigeminal ganglia from pigs killed between postinoculation months 4 to 5 produced infectious virus. Restriction endonuclease analysis indicated that the reactivated PRV was indistinguishable from virus isolated shortly after the primary infection. Seemingly, pigs with maternal antibodies can become latently infected and therefore may be regarded as potential sources of dissemination of PRV.  相似文献   

9.
BackgroundPseudorabies (PR), caused by the pseudorabies virus (PRV), is an endemic disease in some regions of China. Although there are many reports on epidemiological investigations into pseudorabies, information on PRV gI antibody dynamics in one pig farm is sparse.ObjectivesTo diagnose PR and analyze the course of PR eradication in one pig farm.MethodsTen brains and 1,513 serum samples from different groups of pigs in a pig farm were collected to detect PRV gE gene and PRV gI antibody presence using real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.ResultsThe July 2015 results indicated that almost all brain samples were PRV gE gene positive, but PRV gI antibody results in the serum samples of the same piglets were all negative. In the boar herd, from October 2015 to July 2018 three positive individuals were culled in October 2015, and the negative status of the remaining boars was maintained in the following tests. In the sow herd, the PRV gI antibody positive rate was always more than 70% from October 2015 to October 2017; however, it decreased to 27% in January 2018 but increased to 40% and 52% in April and July 2018, respectively. The PRV gI antibody positive rate in 100-day pigs markedly decreased in October 2016 and was maintained at less than 30% in the following tests. For 150-day pigs, the PRV gI antibody positive rate decreased notably to 10% in April 2017 and maintained a negative status from July 2017. The positive trend of PRV gI antibody with an increase in pig age remarkably decreased in three tests in 2018.ConclusionsThe results indicate that serological testing is not sensitive in the early stage of a PRV infection and that gilt introduction is a risk factor for a PRV-negative pig farm. The data on PRV gI antibody dynamics can provide reference information for pig farms wanting to eradicate PR.  相似文献   

10.
The immune response was compared in pigs given inactivated pseudorabies virus (PRV) antigens (with or without adjuvant) or PRV antigens covalently conjugated with a fatty acid (lauric acid) to enhance delayed-type hypersensitivity. The pigs were given 2 inoculations, 14 days apart, and were challenge exposed 28 days after the 1st inoculation. Pibs inoculated with PRV antigens, with or without adjuvant, had significant virus-neutralizing (VN) antibodies before challenge exposure, but the pigs inoculated with lipid-conjugated PRV antigens had no detectable VN antibodies, with the exception of 1 pig. All inoculated pigs were positive by the microimmunodiffusion test at postinoculation day 14 and remained positive throughout the experiment. The inoculated pigs had delayed-type hypersensitivity reactions when skin tested a postinoculation day 25; the pigs inoculated with lipid-conjugated PRV antigens had a more pronounced reaction. Inoculated pigs had mild respiratory signs on the 3rd through the 6th days after challange exposure, with no observable difference in severity between the inoculated groups. The control pigs had acute signs of PRV, and 3 or 4 pigs died 5 to 8 days after challenge exposure. The average VN titers of the different inoculated groups of pigs were nearly equal 2 weeks after challenge exposure. Results indicated that both humoral antibodies and cell-mediated immunity have a role in PRV infections in swine.  相似文献   

11.
为了解浙江省猪主要病毒性传染病的流行情况及变化规律,本试验对2017-2020年浙江省不同地区规模化猪场送检的血清和病料样品进行猪繁殖与呼吸综合征病毒(PRRSV)、猪瘟病毒(CSFV)、猪圆环病毒2型(PCV2)和猪伪狂犬病病毒(PRV)4种疫病病原和抗体检测。抗体检测结果显示：PRRSV、CSFV、PCV2、PRV-gE/gI、PRV-gB的抗体平均阳性率分别为81.4%,83.6%,91.4%,36.1%,94.3%;不同年份中,CSFV和PCV2抗体水平一直呈稳中上升趋势,2020年PRRSV和PRV-gE/gI抗体水平下降明显。病原检测结果显示：PRRSV、CSFV、PCV2和PRV的感染具有普遍性,病原平均阳性率分别为22.9%,2.5%,17.3%,6.6%,其中PRRSV/PCV2双重感染较多,阳性率为9.7%;不同日龄中,PRRSV、PCV2和CSFV保育猪病原阳性率最高,育肥猪次之,而PRV产房仔猪阳性率最高;此外,2019-2020年CSFV、PCV2和PRV的病原阳性率下降明显。  相似文献   

12.
The capacity of a TK-negative (TK-) and gI/gE-negative (gI/gE-) pseudorabies virus (PRV) mutant to protect pigs against Aujeszky's disease carried out by experimental infection with a virulent PRV strain, was tested. There were three groups, each of four susceptible pigs which were inoculated twice by two different schedules. Group 1 received the modified virus by the intradermal (first inoculation)-intramuscular (second inoculation) routes; group 2 was treated by the intranasal (first inoculation)-intramuscular (second inoculation) routes. The third group was left untreated as the control. All of the pigs were challenged intranasally with a virulent PRV strain and they were subsequently injected with dexamethasone. Two pigs in each group were necropsied on days 5 and 15 after dexamethasone inoculation. The challenge exposure resulted in mild clinical signs, increase in growth and a shorter period of virus shedding in vaccinated pigs, whereas the control group showed severe signs of Aujeszky's disease. No difference in the titre of the virulent virus which was excreted by pigs of all three groups, was observed and all animals seroconverted. Both the mutant strain and the wild-type virus established a latent infection although only the latter was reactivated and shed. Slight lesions were observed in target tissues of the vaccinated animals and no significant differences were detected between the two inoculation schedules.  相似文献   

13.
Different deleted Aujeszky's disease vaccines were compared for their ability to induce an immunity which suppresses virus excretion optimally upon infection. Groups of pigs were vaccinated once with attenuated deleted Aujeszky's disease vaccine (gI, gX or gp63 negative), suspended in phosphate buffered saline. Two additional groups were vaccinated with a gI deleted vaccine virus suspended in an oil-in-water emulsion. Other groups were vaccinated twice with gI deleted inactivated vaccines. The three control groups included were: pigs immune after infection, unvaccinated pigs and pigs receiving vaccine without known deletion in the envelope. Experimental challenge took place 3 or 4 weeks after the only or the last vaccination. The number of excreting pigs, the duration of excretion and the virus titers excreted, were determined for all the groups. All the pigs vaccinated with glycoprotein deletion vaccines suspended in phosphate buffered saline, excreted virus for 2 to 6 days after challenge. A 100 to 1000 fold reduction in excreted virus titers was obtained in vaccinated pigs compared to unvaccinated ones. Some vaccines suppressed virus excretion better than others, but no correlation could be made between the type of deletion (gI, gX or gp63) and the degree of reduction in virus excretion. Similar results were obtained with two applications of inactivated vaccines. The lowest number of excreting pigs, the lowest duration of excretion and the lowest titers were obtained in groups vaccinated with the attenuated vaccine suspended in an oil-in-water emulsion. No vaccine suppressed virus excretion totally.  相似文献   

14.
The humoral antibody response of pseudorabies-immune pigs to reactivation of latent pseudorabies virus (PRV) was compared with the response following direct exposure to virulent PRV. Nine pigs that had been vaccinated for pseudorabies and later exposed to virulent virus to establish latent infection were given dexamethasone to reactivate latent virus (3 pigs), were exposed oronasally and parenterally to virulent virus (3 pigs), or were kept as nontreated controls (3 pigs). Sera collected from all 9 pigs just before and 3 weeks after treatment were tested by virus neutralization and radioimmunoprecipitation. The 3 pigs exposed directly to virulent virus and 2 of the 3 pigs given dexamethasone had a 4-fold or greater increase in neutralizing antibody titer. All 6 of these pigs had an increase in precipitating antibody activity. Precipitation patterns changed both quantitatively and qualitatively, especially for virus-coded proteins of relatively low molecular weight (less than 46 K). There were some differences in the precipitation patterns associated with sera of individual pigs. However, there was no clear indication of any difference between the 2 treatment groups and therefore no evidence that reactivation of latent virus is associated with any unique immunologic response that could be detected by radioimmunoprecipitation and used diagnostically. Clinical signs were limited to the 3 pigs that were exposed oronasally and parenterally to virulent virus even though the dexamethasone-treated pigs shed more virus for much longer than did those exposed directly to virus.  相似文献   

15.
Pseudorabies virus (PRV) antibodies, detectable by indirect radioimmunoassay (IRIA), serum-virus neutralization test (NT), or microimmunodiffusion test (MIDT) were developed within 8 days after pigs were inoculated with virulent PRV or attenuated PRV vaccine. Indirect radioimmunoassay and NT titers in pigs inoculated with virulent PRV were developed at the same rate, with IRIA titers being higher than NT titers. Pigs inoculated with attenuated or inactivated PRV vaccine developed peak mean prechallenge NT antibody titers of 4 and 1 (reciprocals of serum dilutions), respectively. Pigs inoculated with attenuated PRV vaccine had peak mean prechallenge IRIA antibody titers of 6, whereas pigs inoculated with inactivated PRV vaccine had mean IRIA antibody titers of 64. Challenge exposure of swine inoculated with attenuated or inactivated PRV vaccine elicited quantitatively equivalent responses, as measured by IRIA or NT, which were higher than prechallenge titers. There were no false-positive IRIA, NT, or MIDT results obtained when sera from nonvaccinated, nonchallenge-exposed pigs were tested. It appears that the PRV infection status of a seropositive swine herd could be ascertained by serologically monitoring several representative animals from a herd, using the NT. If 2 or more tests of representative animals at 14-day intervals were done and the mean NT titer was 4 or less, it could be concluded that the herd was vaccinated against, but not infected with, virulent virus.  相似文献   

16.
12 Large-White-Landrace piglets were subdivided in four groups of 3 and housed in separate units. The piglets of three groups were inoculated with the 86/27V 6C2 thymidine kinase negative (TK-) mutant of pseudorabies virus (PRV), by different routes. A second inoculation with the same mutant was given to the pigs 21 days later. The animals of a fourth group were left as uninoculated controls. 21 days following the second inoculation with the TK- mutant all pigs were challenge infected with the virulent PRV. On post challenge day (PCD) 30 all pigs were killed and samples for virus detection and histology were taken from several organs. The inoculated TK- mutant of PRV did not induce any ill effects in the pigs except a transient febrile reaction in some animals. Virus was recovered from nasal swabbings from one pig 2 days after the first inoculation of the mutant. After challenge exposure with virulent PRV, the TK- mutant-inoculated pigs were apparently protected, whereas the control pigs all were severely affected and recovered very slowly over 3 weeks. Virus was isolated from the nasal swabbings from the TK- mutant-inoculated pigs on PCDs 2 and 4, whereas the nasal swabbings from the control piglets were all positive for virus from PCD 2 through PCD 10. DNA analysis of the virus recovered showed a pattern identical to that of the virulent PRV. Histologic lesions were found in the respiratory and the central nervous systems, however, the lesions in the TK- mutant-inoculated pigs were much milder compared to those registered for the control pigs. Virus was not isolated from any of the tissue samples that were tested, but viral DNA with sequences typical of PRV genome was detected by PCR in all samples of trigeminal ganglia from either the TK- mutant-inoculated pigs or from the controls.  相似文献   

17.
A thymidine kinase (TK)-negative (TK-) deletion mutant of the Bucharest (BUK) strain of pseudorabies virus (PRV) was isolated. The mutant, designated as PRV (BUK d13), did not revert to TK-positive (TK+), even when propagated in medium that selected for TK+ viruses. The mutant also replicated equally well at 39.1 C and 34.5 C, and was easily distinguished from other PRV strains by molecular hybridization experiments, restriction nuclease fingerprints, and plaque autoradiography or other assays for the TK phenotype. The PRV (BUK d13) had greatly reduced virulence for mice and rabbits, compared with parental TK+ strains, PRV (BUK-5) and PRV (BUK-5A-R1), and provided mice with solid protection against the TK+ BUK and Aujeszky strains of PRV. Experiments were done in 5- to 6-week-old pigs to assess the safety and efficacy of PRV (BUK d13) in the natural host. In one experiment, pigs were vaccinated IM with 7.5 X 10(8) plaque-forming units of TK- PRV (BUK d13), and were then challenge exposed intranasally (IN) with 4.3 X 10(8) TCID50 of virulent PRV [Indiana-Funkhauser (IND-F)]. Vaccinated pigs did not have clinical signs of illness after vaccination or after challenge exposure. One nonvaccinated control pig died on postchallenge day 4; a 2nd nonvaccinated control pig became moribund, but eventually recovered. Pigs developed virus-neutralizing antibodies after vaccination, and had a secondary immunologic response after challenge exposure; however, PRV was not isolated from the tonsils or trigeminal ganglia of vaccinated pigs at postchallenge exposure day 11.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

18.
The capacity of a TK‐negative (TK ‐) and gI/gE‐negative (gI/gE ‐) pseudorabies virus (PRV) mutant to protect pigs against Aujeszky's disease carried out by experimental infection with a virulent PRV strain, was tested. There were three groups, each of four susceptible pigs which were inoculated twice by two different schedules. Group 1 received the modified virus by the intradermal (first inoculation)‐intramuscular (second inoculation) routes; group 2 was treated by the intranasal (first inoculation)‐intramuscular (second inoculation) routes. The third group was left untreated as the control. All of the pigs were challenged intranasally with a virulent PRV strain and they were subsequently injected with dexamethasone. Two pigs in each group were necropsied on days 5 and 15 after dexamethasone inoculation. The challenge exposure resulted in mild clinical signs, increase in growth and a shorter period of virus shedding in vaccinated pigs, whereas the control group showed severe signs of Aujeszky's disease. No difference in the titre of the virulent virus which was excreted by pigs of all three groups, was observed and all animals seroconverted. Both the mutant strain and the wild‐type virus established a latent infection although only the latter was reactivated and shed. Slight lesions were observed in target tissues of the vaccinated animals and no significant differences were detected between the two inoculation schedules.  相似文献   

19.
A blocking enzyme-linked immunosorbent assay (ELISA) test has been developed to distinguish pseudorabies virus (PRV)-infected pigs from those immunized with a glycoprotein g92(gIII) deletion mutant, PRV(dlg92dltk). The blocking ELISA utilizes 96-well microtiter test plates coated with a cloned PRV g92(gIII) antigen, a mouse monoclonal antibody against gIII antigen (moMCAgIII): horseradish peroxidase (HRPO) conjugate, and undiluted test sera. Analyses can be completed in less than 3 hours with results printed out by an automated plate reader. Analyses on over 300 pig sera from PRV-free farms, on sera from other species, and on control sera containing antibodies to microorganisms other than PRV showed that the ratio of the optical density at 405 nm for the test sample to the optical density at 405 nm for the negative control (S/N value) was greater than 0.7 for all sera. No false positives were identified. Likewise, the S/N values were greater than 0.7 for over 400 sera obtained from pigs vaccinated twice with more than 1,000 times the standard PRV (dlg92dltk) dose or 1-4 times with the standard dose (2 x 10(5) TCID50/pig). Following challenge exposure to virulent PRV, the S/N values of the vaccinates were 0.1, showing that g92(gIII) antibodies in the sera of experimentally challenged pigs strongly blocked the binding of the moMCAgIII:HRPO conjugate to the antigen-coated wells. Sera of 233 pigs from PRV-infected herds with virus neutralization (VN) titers of 1:4 or greater were tested. All except 2 of these sera had S/N values less than 0.7 and more than 175 had S/N values less than 0.1. Sixteen sera from fetal pigs with VN titers of 1:4 or greater had S/N values of 0.24 or less, but 2 sera with VN titers of 1:4 when tested 5 years prior to the PRV g92(gIII) blocking ELISA test gave false negative S/N values. Twenty-four of 29 pig sera from PRV-infected herds with VN titers less than 1:4 were positive for g92(gIII) antibodies, illustrating the sensitivity of the PRV g92(gIII) blocking ELISA test. Analyses on 7 sera with VN titers of 1:4-1:64 showed that titers obtained with the PRV g92(gIII) blocking ELISA test were from 2- to 16-fold greater than the VN titers. The accuracy and sensitivity of the PRV g92(gIII) blocking ELISA test was further demonstrated by analyses of 40 unknown sera supplied in the National Veterinary Services Laboratories 1988 PRV check test kit.  相似文献   

20.
Sequential changes in the humoral immune response of pigs to pseudorabies virus (PRV) after each of several exposures to the virus were evaluated by determining virus neutralization (VN) and radioimmunoprecipitation (RIP) activities of sera collected at selected intervals. Pigs were vaccinated intramuscularly with live attenuated virus (6 pigs), inactivated attenuated virus (6 pigs), or inactivated virulent virus (6 pigs). All pigs were challenged oronasally with virulent virus 3 weeks later and 12 (4 pigs of each vaccine group) were subsequently treated with dexamethasone in an attempt to reactivate latent virus. The relatively low serum titers of VN antibody that were raised by vaccination (titers ranged from 2 to 32) increased markedly (at least 16-fold) for all pigs after exposure to virulent virus. After dexamethasone treatment, the VN titers of 2 pigs increased 16-fold, whereas those of the other 10 dexamethasone-treated pigs and the 6 nontreated pigs either remained the same or increased only minimally (i.e., no more than 2-fold). The results of RIP using 35S-methionine-labeled viral proteins were initially similar to those of VN in that the low levels of serum RIP activity detected after vaccination increased markedly after subsequent exposure to virulent virus. In contrast to VN, however, most pigs (11 of 12) treated with dexamethasone had a clear increase in serum RIP activity. The increase was particularly striking for viral proteins of relatively low (less than 46K) molecular weight. Precipitating activity for 14C-glucosamine-labeled viral glycoproteins was not detected until after pigs were exposed to virulent virus. The increase in RIP activity detected after dexamethasone treatment was likely due to an additional antigenic stimulus associated with virus reactivation. However, virus was isolated from nasal swabs of only 4 of the 12 treated pigs. None of the results appeared to be affected appreciably by the type of vaccine used for initial immunization.  相似文献   

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