Reduced efficacy of hemorrhagic enteritis virus vaccine in turkeys exposed to avian pneumovirus

Avian pneumovirus (APV) is an immunosuppressive respiratory pathogen of turkeys. We examined the effect of APV infection on the vaccine efficacy of hemorrhagic enteritis virus (HEV) vaccines. APV was inoculated in 2-wk-old turkeys. Two or four days later, an attenuated HEV vaccine (HEVp30) or marble spleen disease virus (MSDV) vaccine were administered. Virulent HEV challenge was given 19 days after HEV vaccination. APV exposure compromised the ability of HEVp30 and MSDV to protect turkeys against virulent HEV. The protective index values were as follows: MSDV (100%) versus APV + MSDV (0%) (P < 0.05); HEVp30 (60%) versus APV + HEVp30 (30%) (P < 0.05) (Experiment I) and HEVp30 (56%) versus APV + HEVp30 (20%) (P < 0.05) (Experiment II). These data indicated that APV reduced the efficacy of HEV vaccines in turkeys.     

Cold-adapted strain of avian pneumovirus as a vaccine in one-day-old turkeys and the effect of inoculation routes

To determine the optimum route of vaccination, we inoculated 1-day-old turkeys with a cold-adapted strain of avian pneumovirus (APV) by oculonasal, oral, or aerosol route. Another two groups served as nonvaccinated-challenged and nonvaccinated-nonchallenged groups. Birds in all vaccinated and nonvaccinated-challenged groups were challenged with virulent APV 3 wk postvaccination. After challenge, no vaccinated bird developed clinical signs or virus shedding, whereas nonvaccinated-challenged birds developed clinical signs (clinical score = 11.2/bird) and shed virus from their choanal cleft. Birds in all three vaccinated groups seroconverted at 3 wk postvaccination. The nonvaccinated-nonchallenged group remained free of clinical signs and virus shedding and did not develop APV antibodies throughout the course of the study. These results suggest that this cold-adapted strain of APV is safe and effective in 1-day-old turkeys when given by any of the three routes.     

Structural polypeptides of type II avian adenoviruses analyzed by monoclonal and polyclonal antibodies.

Polypeptides of hemorrhagic enteritis virus (HEV) of turkeys and marble spleen disease virus (MSDV) of pheasants were analyzed by immune precipitation and immunoblot assays. A total of 11 polypeptides ranging in molecular weight from 14,000 to 97,000 were detected in lysates of HEV-infected turkey cells analyzed by immunoblot assay using a polyclonal antibody against HEV. Identical patterns were observed with preparations of MSDV. Five monoclonal antibodies (MAbs) against HEV were chosen based on their virus neutralization activity and used for identification of neutralizing epitopes of these two viruses. Three MAbs precipitated a single 97,000-molecular-weight hexon polypeptide in an immune precipitation assay.     

Effects of infectious bursal disease on Marek's disease vaccination: suppression of antiviral immune response

Studies were made to determine whether infectious bursal disease virus (IBDV) infection would affect the response of chickens to turkey herpesvirus (HVT) vaccination in the development and level of HVT viremia and virus-neutralizing (VN) antibodies to HVT. The HVT viremia in the vaccinated chickens was not affected by IBDV, whether IBDV was inoculated simultaneously with HVT vaccination at one day of age or whether it was inoculated 3 weeks postvaccination with HVT. However, VN antibody response to HVT was significantly suppressed (P less than 0.001) when vaccinated chickens were exposed to IBDV either at the time of vaccination or at 3 weeks postvaccination. Such immunosuppression by IBDV of VN antibody response to HVT vaccination may result in a reduced antiviral immunity against Marek's disease virus.     

Field vaccination against hemorrhagic enteritis of turkeys by a cell-culture live-virus vaccine

A cell-culture-propagated (CC) live-virus hemorrhagic enteritis (HE) vaccine was evaluated for efficacy and safety in two field trials conducted in North Carolina (NC) and Minnesota (MN). At 4 or 5 1/2 weeks of age, 9,839 poults in NC and 15,857 poults in MN were vaccinated with a CC HE vaccine administered via the drinking water. A comparable number of poults were maintained as unvaccinated controls. Vaccinated and unvaccinated poults were compared for seroconversion, response to laboratory challenge with a virulent HE virus at 3 weeks postvaccination, livability, percentage graded A, and average weight at marketing. In both trials, vaccination with the CC HE vaccine resulted in immunity against HE as indicated by seroconversion and by resistance to HE lesions following laboratory challenge with virulent HE virus. Compared with unvaccinated groups, vaccinated groups had a significantly higher percentage of turkeys graded A in the NC trial and in two of three flocks in the MN trial (P less than 0.005). Further, in the NC trial, livability was significantly higher (P less than 0.005) in vaccinated turkeys than in unvaccinated turkeys. These data indicate that the CC HE vaccine is efficacious and safe to use in the field.     

Onset and duration of immunity and minimum dosage with CU cholera vaccine in turkeys via drinking water

Growing turkeys were partly protected against fowl cholera 4 days after vaccination with the live Clemson University (CU) strain of Pasteurella multocida administered in drinking water, and they were highly protected from 1 to 4 weeks after vaccination. The commercially available lyophilized vaccine and the freshly cultured vaccine of the CU strain did not differ in the level of immunity induced. Immunity was relatively high in turkeys vaccinated with 1:2 and 1:4 dilutions of the recommended dosage (4 X 10(8) P. multocida) but was significantly (P less than 0.05) lower in turkeys vaccinated with a 1:8 dilution of the recommended dosage. Immunity continued for 13 weeks after the last vaccination in turkeys vaccinated twice 3 weeks apart, but it persisted for only 8 weeks in those vaccinated only once.     

Relationship between anti-Pasteurella multocida antibody titers after CU vaccination and survival after challenge

The relationship between serum anti-Pasteurella multocida antibodies and survival rates after challenge was determined in turkeys vaccinated one or more times with the live avirulent Clemson University (CU) vaccine and then challenged with a virulent isolate (9481) of P. multocida in the drinking water. A microtiter agglutination test for assaying anti-P. multocida serum antibodies demonstrated a highly significant (P less than 0.001) correlation between the serum antibody titer 1 week after the initial or single vaccination and the survival rate after challenge, and a significant (P less than 0.01) correlation between the antibody titer immediately before challenge and the survival rate after challenge. A highly significant (P less than 0.0001) correlation was also observed between the antibody titer before vaccination and the survival rate after challenge. This relationship was considered the result of an anamnestic response by the CU vaccine to a previous sensitization by antigens of other microbial organisms, probably in the intestine and similar antigenically to P. multocida. In contrast, a significant (P less than 0.05) but negative correlation was seen between the antibody titer 1 week after challenge and the survival rate. This relationship was thought to be the result of a marked stimulation of the antibody titer by the systemic infection of P. multocida that subsequently killed the turkeys.     

Studies on Pasteurella multocida. IV. Immunofluorescence detection of the organisms in spleen and lungs of turkeys vaccinated with live oral vaccines

Oral vaccination of turkeys with live avirulent strains of P. multocida (M-2283 and CU strain) resulted in the local as well as systemic dissemination of the organisms. The persistence of P. multocida in the lungs and splenic tissues of these vaccinated turkeys was demonstrated by the indirect immunofluorescence technique. All of the tissues examined up to the first week post vaccination were P. multocida positive. Cryostat sections of lungs from birds vaccinated with the avirulent strain M-2283 were negative at 2 weeks post vaccination, while the spleen continued to be positive up to the third week post vaccination. In contrast to the group of turkeys vaccinated with strain M-2283, lung and spleen cryostat sections from turkeys vaccinated with strain CU remained positive up to the fourth week post vaccination. Tissues examined thereafter were negative for the presence of P. multocida from both groups.The major immune mechanism in the defense against fowl cholera is still unknown. If local immunity is primarily responsible, the CU strain may be the better vaccine strain as it persists in the lungs for 2 weeks longer than the M-2283 strain. However, if systemic immunity is chiefly responsible for immunity, both strains could protect equally, since they persist in the spleen for approximately the same period of time.     

In vitro DNA synthesis in lymphocytes from turkeys vaccinated with LaSota, TC, and inactivated Newcastle disease vaccines.

In vitro cultures of peripheral blood lymphocytes from turkeys vaccinated and revaccinated with Newcastle disease (ND) vaccines were stimulated to transformation when exposed to the homologous and heterologous strains of ND virus. The mitogenesis was measured by the uptake of 3H-thymidine into newly synthesized DNA. There was considerable difference in DNA synthesis by lymphocytes drawn 0, 2, 5, and 10 days after vaccination and revaccination with the three vaccines. Stimulation of DNA synthesis, evident as early as the 2nd day, was highest in lymphocytes from turkeys vaccinated or revaccinated with TCND intramuscularly. Stimulation was least in lymphocytes from turkeys vaccinated and revaccinated with LaSota vaccine by aersol. Stimulation was intermediate from an inactivated vaccine given subcutaneously. DNA synthesis was greater with the homologous than with the heterologous strains of NDV. Synthesis was even greater when the same strain was used as a viral suspension in allantoic or cell-culture fluid than the commercial vaccine. The bovine paramyxovirus (PI3) resulted in a minimum DNA synthesis or completely inhibited it. A many-fold (order of magnitude) stimulatory effect was observed when PHA was used as an antigen. The stimulation of DNA synthesis did not parallel the HI antibody response.     

Evaluation of a modified-live virus vaccine administered in ovo to protect chickens against Newcastle disease.

The B1 strain of Newcastle disease virus (NDV-B1), which is nonpathogenic for newly hatched chickens, killed embryos when it was used to inoculate chicken eggs at embryonation day 18. Treatment of NDV-B1 with an alkylating agent, ethylmethane sulfonate (EMS) markedly reduced the pathogenicity of the virus for 18-day-old chicken embryos. Eggs inoculated with the modified virus (NDV-B1-EMS) hatched, and the virus was isolated from lungs and spleen of 1-day-old chickens. The hatched chickens developed antibody to NDV and were protected against challenge exposure (at 4 weeks of age) with a highly virulent GB-Texas strain of NDV. Presence of maternal antibody to NDV in embryonating eggs did not influence the protective ability of NDV-B1-EMS, which also induced protective immunity when administered to 4-week-old chickens. The 50% protective dose of NDV-B1-EMS in maternal antibody-negative and -positive embryos was calculated to be 10.77 and 17.70 embryo 50% lethal doses, respectively. Results of the study indicated that NDV-B1-EMS may be used as an embryo vaccine to protect chickens against Newcastle disease.     

Bovine viral diarrhea virus type 1- and type 2-specific bovine T lymphocyte-subset responses following modified-live virus vaccination

Expression of CD25 (interleukin-2 receptor alpha chain) was used to monitor antigen-specific activation of T lymphocyte subsets (CD4+, CD8+, and gamma delta T cells) from cattle immunized with modified-live virus (MLV) bovine viral diarrhea virus (BVDV) vaccines. Two groups of 15 animals each were vaccinated with one dose of either BVDV genotype 1 (BVDV-1) or BVDV-1 and BVDV genotype 2 (BVDV-1/2). Six animals negative for both BVDV antibody and BVDV virus were used as negative controls. Three animals vaccinated 7 and 5 weeks before the start of the experiment with MLV BVDV-1 vaccine served as positive controls. Blood samples were taken from the negative control group, the positive control group, and the BVDV-1/2 group 0, 21, 35, 60, and 90 days after vaccination. Blood samples were taken from the BVDV-1 group 0, 21, and 90 days after vaccination. Isolated peripheral blood lymphocytes from immunized and control animals were incubated for 5 days with and without BVDV-1 or BVDV-2. Compared with nonvaccinated animals, a significant (P <.05) increase in expression of CD25 by CD4+ (60 days), CD8+, and gammadelta T (35 to 90 days) lymphocytes from the group given BVDV-1/2 was detected following in vitro exposure to BVDV-1 or BVDV-2 after vaccination. The CD8+ and gammadelta T cells from the group vaccinated with BVDV-1 had significantly (P <.05) increased expression of CD25 compared with nonvaccinates following postvaccination exposure to in vitro BVDV-1 but not to BVDV-2. There was no significant difference between the two vaccinated groups in CD25 expression on any of the T cell subsets in response to BVDV-1 or BVDV-2 exposure. A single administration of MLV BVDV vaccine may be more effective at stimulating CD8+ and gammadelta T cell-specific immune responses to the homologous genotype than to the heterologous genotype.     

The duration of immunity to an inactivated adjuvanted canine parvovirus vaccine. A 52 and 64 week postvaccination challenge study

Dogs were successfully isolated for a period of either 52 or 64 weeks following vaccination with an inactivated, adjuvanted canine parvovirus-2 vaccine. Antibody persisted in all ten vaccinated dogs, although in one case by 52 weeks postvaccination only virus neutralizing antibody, and not hemagglutination-inhibiting antibody, could be detected. Sentinel unvaccinated dogs housed alongside the vaccinated dogs throughout the study remained free of canine parvovirus-2 antibody until challenged. Upon oral challenge with canine parvovirus-2 infected material all unvaccinated dogs developed one or more signs of canine parvovirus-2 disease, shed virus and developed antibody. None of the vaccinated dogs became overtly sick. Of the five vaccinated dogs challenged 52 weeks after vaccination, three shed virus and one showed a significant rise in antibody. At 64 weeks after vaccination only one of the five challenged dogs shed virus and showed a boost in antibody titer.     

Nonspecific innate immunity against Escherichia coli infection in chickens induced by vaccine strains of Newcastle disease virus

The objective was to test the hypothesis that vaccine strains of Newcastle disease virus (NDV) induce nonspecific immunity against subsequent infection with Escherichia coli. White leghorn chickens at 5 wk of age were vaccinated with a NDV vaccine at various days before challenge exposure with O1:K1 strain of E. coli via an intra-air sac route. Immunity was determined on the basis of the viable number of E. coli in the spleen 24 hr after the infection. Roakin strain induced significant (P < 0.05) immunity against E. coli at 4, 6, and 8 days, and La Sota strain at 2, 4, and 8 days, postvaccination. Secondary NDV vaccination administered 14 days later failed to induce immunity against E. coli when chickens were infected 1 or 5 days after the vaccination. Significant (P < 0.05) suppression of this nonspecific immunity was observed in birds treated with corticosterone, 40 mg/kg in feed, given for three consecutive days immediately prior to the bacterial exposure but not in those treated prior to the period. The results indicate that innate immunity induced by the primary NDV vaccination may significantly suppress the multiplication of E. coli in chickens for a period of 2-8 days postvaccination. The NDV-induced immunity was inhibited by corticosterone, which is known to mediate physiological responses to stress.     

鸡新城疫重组鸡痘病毒活疫苗的免疫持续期和加强免疫研究

本研究旨在评价表达新城疫病毒（NDV）血凝素-神经氨酸酶（HN）基因的重组鸡痘病毒（rFPV-12LSHN）活疫苗的免疫持续期和加强免疫对疫苗免疫效力的影响。用rFPV-12LSHN活疫苗免疫14日龄SPF鸡,103PFU/羽,7d即可检测到NDV HI抗体应答,对NDV强毒F48E8株攻毒保护率达100%。一次免疫18周后,对NDV强毒攻击依然提供完全保护。鸡痘病毒（FPV）疫苗免疫4周,再接种rFPV-12LSHN活疫苗,攻毒保护率降低至50%。相反,rFPV-12LSHN免疫4周,随后二次免疫可显著提高对NDV的体液免疫应答水平（P〈0.01）,对NDV强毒攻击的保护率仍然为100%。结果表明,表达NDV HN基因的重组鸡痘病毒（rFPV-12LSHN）活疫苗,能够快速建立坚强免疫力,免疫持续期至少可达18周,rFPV-12LSHN的二次免疫可以提高疫苗的免疫力。     

Comparative serological evaluation of avian influenza vaccine in turkeys

Four- and six-week-old turkeys were vaccinated subcutaneously using avian influenza virus (AIV) A/Duck/613/MN/79 (H4N2) killed oil-emulsion vaccine. Sequential serological tests using agar gel precipitin (AGP), hemagglutination inhibition (HI), and enzyme-linked immunosorbent assay (ELISA) for measuring antibodies to AIV were performed up to 4 weeks postvaccination, when birds were challenged intranasally using A/Turkey/MN/80 (H4N2) live AIV. The ELISA was 25 to 1600 times more sensitive than the HI test and was able to detect antibody production earlier than the HI test. All turkeys with an ELISA titer of greater than or equal to 800 were protected against homologous challenge, as measured by virus recovery 3 days postchallenge. Four turkeys out of 20 serologically negative by AGP and HI tests but ELISA-positive were protected.     

Induction of humoral immune response and protective immunity in chickens against Salmonella enteritidis after a single dose of killed bacterium-loaded microspheres.

Formalin-inactivated Salmonella enteritidis phage type 4 strain 119/95 (SE) was encapsulated in biodegradable poly (DL-lactide co-glycolic acid) PLGA; (65:35) microspheres by a modified water-in-oil-in-water (w/o/w) double-emulsion solvent extraction/evaporation technique. These SE-loaded microspheres (SE-MS) were porous and spherical in shape with diameters of 0.4-10 microm and 20-80 microm in two preparations. SE-MS were subsequently used to vaccinate specific-pathogen-free chickens in a single dose in order to investigate the potency of a single-dose vaccination in inducing immune responses and protective immunity. In Experiment 1, 4-wk-old chickens that were vaccinated intramuscularly with 20-80-microm SE-MS generated long lasting (over 6 mo) and persistently high serum anti-SE immunoglobulin (Ig)G antibody response. In Experiment 2, 2-wk-old chickens were vaccinated orally with 0.4-10-microm or intramuscularly with 20-80-microm SE-MS and challenged with 10(9) colony-forming units of homologous SE strain at 6 wk postvaccination. When challenged intramuscularly, one each of the orally vaccinated (n = 10) and the intramuscularly vaccinated birds (n = 10) showed clinical signs and death, whereas all of the nonvaccinated control birds (n = 12) were sick and 11 of them were killed. When challenge was via oral route, 26.1% of cloacal swabs and 24.0% of organs (liver, spleen, and cecum) collected from orally vaccinated birds (n = 35) were positive for SE, comparable to 27.9% of feces and 18.7% of organs from the intramuscularly vaccinated birds (n = 35). These figures were significantly lower than those for nonvaccinated birds (n = 30) from which 59.3% of feces and 44.0% of organs tested SE positive (P < 0.05). The humoral immune response was also determined after vaccination with a single dose. The intramuscular vaccination elicited higher serum IgG response than oral administration, but the latter elicited a significant intestinal mucosal IgA antibody response. This is the first evidence that chickens vaccinated with killed SE-loaded PLGA microspheres, intramuscularly and orally in a single dose, developed systematic and local immune responses, thereby conferring protective immunity.     

Identification of a mutant bovine herpesvirus-1 (BHV-1) in post-arrival outbreaks of IBR in feedlot calves and protection with conventional vaccination.

Outbreaks of infectious bovine rhinotracheitis (IBR) have recently been observed in vaccinated feedlot calves in Alberta a few months post-arrival. To investigate the cause of these outbreaks, lung and tracheal tissues were collected from calves that died of IBR during a post-arrival outbreak of disease. Bovine herpesvirus-1 (BHV-1), the causative agent of IBR, was isolated from 6 out of 15 tissues. Of these 6 isolates, 5 failed to react with a monoclonal antibody specific for one of the epitopes on glycoprotein D, one of the most important antigens of BHV-1. The ability of one of these mutant BHV-1 isolates to cause disease in calves vaccinated with a modified-live IBR vaccine was assessed in an experimental challenge study. After one vaccination, the majority of the calves developed humoral and cellular immune responses. Secondary vaccination resulted in a substantially enhanced level of immunity in all animals. Three months after the second vaccination, calves were either challenged with one of the mutant isolates or with a conventional challenge strain of BHV-1. Regardless of the type of virus used for challenge, vaccinated calves experienced significantly (P < 0.05) less weight loss and temperature rises, had lower nasal scores, and shed less virus than non-vaccinated animals. The only statistically significant (P < 0.05) difference between the 2 challenge viruses was the amount of virus shed, which was higher in non-vaccinated calves challenged with the mutant virus than in those challenged with the conventional virus. These data show that calves vaccinated with a modified-live IBR vaccine are protected from challenge with either the mutant or the conventional virus.     

Antibody response and resistance of turkeys to Newcastle disease vaccine strain LaSota.

Studies were undertaken to determine the influence of repeated revaccination on the immune response in immuno-competent turkeys as measured by humoral antibody and resistance to challenge. Protection was better in turkeys given the LaSota spray vaccine at 4 weeks and 30 days later than in turkeys given one vaccination by spray or intramuscular route or exposed 4 times at 10-day intervals by the aerosol route. The anamnestic response, as measured by the HI tests to revaccination with the same immunogen, was not evident by the 3rd day postrevaccination but was observed on the 7th day. The interval between primary and secondary vaccination was found to be important to a true and optimal anamnestic response. Response was greater, however, in vaccinated turkeys exposed to VVND, a more virulent virus antigenically different from the vaccine strain. Exposure to LaSota vaccine by the intramuscular route gave a poorer HI response than LaSota given by aerosol.     

囊素对哺乳动物免疫促进作用的研究Ⅱ.不同剂量囊素对猪瘟疫苗接种猪抗体水平的影响

囊素是一种新型的免疫活性物质 ,为了研究其对哺乳动物的免疫促进作用 ,探索正确的使用方法。作者采用不同剂量 (0 .0 3 ,0 .0 6,0 .0 9m L/ kg)囊素与猪瘟疫苗同时接种 3 0日龄仔猪进行试验。在接种后 2周内 ,试验猪没有出现异常临床反应 ,表明囊素与猪瘟疫苗同时使用无不良影响。在接种后 6周内 ,每隔一周检测各组猪瘟抗体水平。结果表明 :囊素按 0 .0 6m L /kg和 0 .0 9m L/ kg剂量与猪瘟疫苗同时使用组其抗体水平明显高于对照组。通过抗体水平比较及统计学分析 ,表明囊素最佳使用剂量为0 .0 6m L/ kg。