Drinking water vaccination against infectious laryngotracheitis.

Chickens varying in age from ten days to five years were vaccinated with 10(1.3), 10(2.3) and 10(3.3) EID50 per bird of a commercial infectious laryngotracheitis drinking water vaccine. The vaccine gave no adverse reaction in the dose range tested. Five weeks after administration of 10(3.3) EID50 per bird 70% were protected against the intratracheal challenge with virulent infectious laryngotracheitis virus. Doses of 10(1.3) and 10(2.3) EID50 per bird did not give protection. No serological response could be detected by the neutralization test even in the group that had received 10(3.3) EID50 per bird. No contact spread of virus was detected from 14 days post-vaccination. Carriers of vaccine virus could not be demonstrated.     

Protection induced by infectious laryngotracheitis virus vaccines alone and combined with Newcastle disease virus and/or infectious bronchitis virus vaccines

Two types of live attenuated vaccines have been used worldwide for the control of infectious laryngotracheitis virus (ILTV): 1) chicken embryo origin (CEO) vaccines; and 2) tissue culture origin vaccines (TCO). However, the disease persists in spite of extensive use of vaccination, particularly in areas of intense broiler production. Among the factors that may influence the efficiency of ILTV live attenuated vaccines is a possible interference of Newcastle Disease virus (NDV) and infectious bronchitis virus (IBV) vaccines with the protection induced by ILTV vaccines. The protection induced by CEO and TCO vaccines was evaluated when administered at 14 days of age alone or in combination with the B1 type strain of NDV (B1) and/or the Arkansas (ARK) and Massachusetts (MASS) serotypes of IBV vaccines. Two weeks after vaccination (28 days of age), the chickens were challenged with a virulent ILTV field strain (63140 isolate, group V genotype). Protection was evaluated at 5 and 7 days postchallenge by scoring clinical signs and quantifying the challenge virus load in the trachea using real-time PCR (qPCR). In addition, the viral load of the vaccine viruses (ILTV, NDV, and IBV) was quantified 3 and 5 days postvaccination also using qPCR. The results of this study indicate that the NDV (B1) and IBV (ARK) vaccines and a multivalent vaccine constituted by NDV (B1) and IBV (ARK and MASS) did not interfere with the protection induced by the CEO ILTV vaccine. However, the NDV (BI) and the multivalent (B1/MASS/ARK) vaccines interfered with the protection induced by the TCO vaccine (P < 0.05). Either in combination or by themselves, the NDV and IBV vaccines decreased the tracheal replication of the TCO vaccine and the protection induced by this vaccine, since the ILTV-vaccinated and -challenged chickens displayed significantly more severe clinical signs and ILTV load (P < 0.05) than chickens vaccinated with the TCO vaccine alone. Although NDV and IBV challenges were not performed, the antibody responses elicited by NDV and/or the IBV vaccinations were significantly reduced (P < 0.05) when applied in combination with the CEO vaccine.     

Safety and efficacy of in ovo administration of infectious bursal disease viral vaccines

In ovo vaccination against Marek's disease virus and infectious bursal disease virus (IBDV) in commercial broilers in the United States is common. Little information exists as to the safety and efficacy of intermediate IBDV vaccines given in ovo. Experiments were initiated to determine the safety and efficacy of three commercially available live intermediate IBDV vaccines by in ovo route. Commonly used vaccines were given at 18 days of embryonation to specific-pathogen-free (SPF) broiler embryos (first and second study) or to commercial broiler embryos (third study) that had maternal antibody against IBDV. When any of the antigenic standard vaccines was given at full dose to SPF embryos, embryonic and 3-wk posthatch mortality increased. Vaccines also caused significant microscopic lesions in the bursa of Fabricius at 1 and 3 wk posthatch. In contrast, there was no adverse effect on embryonic or posthatch mortality when vaccines were given at half dose to SPF or commercial broiler embryos. However, significant microscopic lesions were evident at 1 and 3 wk posthatch in the bursae of SPF embryos given the vaccines at half dose. When vaccines were given at half dose to commercial broiler embryos, lesions were evident at 1 but not 3 wk of age. In the third study, in ovo vaccinated chickens were challenged with either a virulent standard (APHIS) or antigenic variant (variant E) IBDV virus at 3 wk of age. All vaccines produced at least 87% protection against the standard and 60% protection against the variant challenge IBDV, as measured by bursal weight to body weight ratios. This study was the first to examine the safety and efficacy of the three commonly used intermediate IBDV vaccines given in ovo in protection against standard and antigenic variant IBDV challenge viruses.     

表达传染性喉气管炎病毒gB基因和新城疫病毒F基因重组鸡痘病毒疫苗免疫持续期试验

用表达传染性喉气管炎病毒gB基因和新城疫病毒F基因的重组鸡痘病毒（rFPV～gB—F）制备的疫苗免疫4周龄SPF鸡，免疫后的7、14、21、30、60、90、120、150、180d分别采血，分离血清，检测抗FPV和gB的抗体。结果表明重组疫苗免疫后14d，免疫鸡血清抗体已经全部阳转，免疫后的21d血清抗FPV的抗体出现峰值；此后便开始回落，到免疫后的6个月抗体水平已经接近阴性对照的水平。抗gB的抗体在免疫后的第二周达到阳性，之后的六个月都为阳性。在免疫后的每个月将免疫鸡取20只再分成两组。分别用新城疫强毒与传染性喉气管炎强毒的攻击。在免疫后的第一个月对新城疫的保护率为8／10，第2个月对新城疫的保护为7／10，第3个月为2／10，因此对新城疫的免疫保护期为2个月。在免疫后的5个月内可以使免疫鸡对传染性喉气管炎强毒攻击的保护率达到8／10以上，免疫后的6个月对ILT为8／13．因此rF—PV-gB—F对传染性喉气管炎的免疫保护期为5个月。     

Efficacy of live virus vaccines against infectious laryngotracheitis assessed by polymerase chain reaction-restriction fragment length polymorphism

The efficacy of four different commercial live vaccines (vaccines A, B, C, and D) against the infectious laryngotracheitis virus (ILTV) was assessed in specific-pathogen-free (SPF) chickens. SPF chickens were vaccinated intraocularly at 6 wk old with ILTV live vaccines and were challenged intratracheally with the N91B01 strain of virulent Korean ILTV 2 wk after vaccination. The immunity against ILTV live vaccines was assessed by the incidence of latent infection by the challenge virus in the chickens' tracheas and trigeminal ganglia, the reisolation rate of the challenge virus, and the clinical signs in the chickens challenged with the N91B01 strain of ILTV. The latent infection in chickens was assessed by nested polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Our data showed that the clinical signs and challenge virus isolation were negative in all chickens receiving four difference commercial ILTV live vaccines. The viral DNA of the vaccine strain, but not that of the challenge virus, was detected in chickens vaccinated with vaccine A by nested PCR-RFLP. The viral DNAs of both the vaccine and challenge strains were detected from chickens vaccinated with vaccines B, C, and D. This study showed that only vaccine A can protect chickens from latent infection with the field virulent ILTV. We speculate that the efficacy of infectious laryngotracheitis live vaccines to protect chickens from latent infection with virulent ILTVs can be assessed by nested PCR-RFLP analysis.     

Studies of infectious laryngotracheitis vaccines: immunity in layers

Ten-week-old layer chickens obtained from a commercial source were eye-drop vaccinated with chicken-embryo-origin (CEO) or tissue-culture-origin (TCO) vaccines for infectious laryngotracheitis (ILT). Controls were not vaccinated. Approximately one-third of the layers were challenged with virulent ILT virus at 21, 40, or 60 weeks of age. Serum samples taken from the layers before challenge were used in a virus neutralization (VN) test to determine vaccination titers at those three ages. Both vaccines induced low VN titers (geometric mean titer [GMT] less than 6). At 21 weeks of age, the titers produced by the two vaccines were not significantly different, but at 40 and 60 weeks of age the VN GMT of the CEO-vaccinated group was significantly greater than that of the TCO-vaccinated group. The VN GMTs did not drop over time in either group and actually rose between 21 and 60 weeks of age in the CEO group. Both vaccines protected layers against severe challenge with virulent ILT virus, neither being significantly better than the other under these experimental conditions. Unvaccinated sentinel chickens were maintained in contact with the vaccinated layers during three intervals between 1 day and 6 weeks post-vaccination. Diagnostic tests performed on the sentinels to detect lateral spread of vaccine virus from vaccinated to unvaccinated chickens showed scattered positive results.     

Studies of infectious laryngotracheitis vaccines: immunity in broilers

Broiler chickens were vaccinated at 18 days of age against infectious laryngotracheitis (ILT) using chicken-embryo-origin (CEO) and tissue-culture-origin (TCO) vaccines, each vaccine given either by drinking water, spray, or eyedrop. Controls were not vaccinated. The broilers were challenged 3 weeks later with virulent ILT virus (USDA challenge strain). Serum samples taken before challenge were analyzed by a virus neutralization (VN) test to determine titers due to vaccination. Both vaccines, regardless of route of administration, produced low VN titers, geometric mean titer (GMT) being less than 4.0 in all vaccinated groups. When administered by the same route, the CEO vaccine produced higher titers than the TCO vaccine. Titers following drinking-water or eyedrop administration of vaccines were higher than titers following spray vaccination. There was an inverse relationship between pre-challenge VN titers of groups of birds and the percentage of birds in the groups dying from ILT virus challenge. The drinking-water route of vaccination provided the most protection, while the spray provided the least.     

Protection of laying hens against infectious bronchitis with inactivated emulsion vaccines

Commercially-reared laying chickens were challenged at 31 weeks of age with a virulent infectious bronchitis (IB) virus. They showed a sharp drop in egg production, despite having been vaccinated at four and eight weeks old with live attenuated IB vaccines to a recommended schedule. In contrast, similar birds that had been further immunised at point-of-lay with inactivated oil emulsion IB vaccine, or with a combined IB/Newcastle disease (ND) emulsion vaccine, showed no detectable fall in egg production after the same challenge. Unvaccinated susceptible specific pathogen-free birds challenged at the same time stopped laying almost completely. In the birds revaccinated with emulsion vaccine, measurement of haemagglutination inhibition antibody levels to IB showed their geometric mean titres to be raised from less than 5 log2 at the time of vaccination to over 10 log2 four weeks later. Their antibody levels did not rise further followining the IB challenge whereas in the birds that had not been revaccinated antibody rises to nearly 10 log2 were detected after the same challenge. For pullets vaccinated earlier with live IB vaccine, revaccination with inactivated IB or IB/ND oil emulsion vaccine at point-of-lay provides a safe and effective way of protecting their egg production against IB infection.     

Protection by recombinant viral proteins against a respiratory challenge with virulent avian metapneumovirus

Protection by recombinant avian metapneumovirus (aMPV) N or M proteins against a respiratory challenge with virulent aMPV was examined. N, M or N+M proteins were administered intramuscularly (IM) with incomplete Freund's adjuvant (IFA) or by the oculonasal (ON) route with cholera toxin-B (CTB). Each turkey received 40 or 80 microg of each recombinant protein. Birds were considered protected against challenge if the challenge virus was not detectable in the choanal swabs by RT-PCR. At a dose of 40 microg/bird, N protein given with IFA by the IM route protected eight out of nine birds. M protein at the same dose protected three out of seven birds, while a combination of N+M proteins (40 microg each) protected three out of four birds. At a dose of 80 microg of each of N and M proteins per bird given with IFA by the IM route, 100% protection was achieved. ON immunization with a mixture of N and M proteins induced partial protection when the proteins were given with CTB; no detectable protection was noted without CTB. N and M proteins induced anti-aMPV antibodies, although protection against virulent virus challenge did not appear to be associated with the level or presence of antibodies.     

Detection of antibodies against infectious viral laryngotracheitis and parainfluenza 2 in dogs bred in Czechoslovakia

A total of 398 blood serums of dogs of various breeds and age categories, coming from 72 places in Bohemia and Slovakia, were examined for the content of haemagglutination-inhibiting (HI) antibodies to the infectious laryngotracheitis virus (CADV-2) and parainfluenza 2 virus (CPIV-2). Out of this total number, 203 serums (51.1%) reacted against CADV-2 in titres from 1:16 to 1:2048 and 115 serums (28.9%) against CPIV-2 in titres from 1:2 to 1:256. The results indicate that the dog population is considerably infected with viruses affecting the respiratory organs.     

Immunosuppression in specific-pathogen-free broilers administered infectious bursal disease virus vaccines by in ovo route

The effect of two infectious bursal disease virus (IBDV) vaccines (IBDV-immune complex [Icx] and IBDV-2512), administered in ovo, on the cell-mediated immunity of specific-pathogen-free (SPF) broilers was examined. A decrease (P < 0.05) in the T-cell mitogenic response occurred in birds vaccinated with both vaccines on days 9 and 21 post in ovo vaccination (PIOV), but an increase (P < 0.05) occurred on day 15 PIOV. The T cells from birds given the IBDV-2512 were less responsive. There were no significant differences in proportions of lymphocytes expressing CT4+CT8 and CT8+CT4- except on day 21 PIOV, where an increase (P < 0.05) in IBDV-2512-vaccinated birds and a decrease (P < 0.05) in percentage of CT4+CT8- in IBDV-Icx-vaccinated birds was observed. There was an increase (P < 0.05) in percentage of CT8+CT4- T cells on day 21 PIOV in both vaccinated groups. A decrease (P < 0.05) in B-cell percentage was observed on day 21 PIOV in birds given both vaccines. Results indicated that although humoral immunosuppression is associated with destruction of B cells (bursal atrophy), cell-mediated immunosuppression induced by these two IBDV vaccines in SPF birds was not associated with altered helper (CT4+CT8-) or cytotoxic (CT8+CT4-) subpopulations of T lymphocytes.     

In ovo vaccination of specific-pathogen-free chickens with vaccines containing multiple agents.

We used in ovo technology to protect chickens against multiple diseases by inoculating vaccines containing mixtures of live viral agents. A single in ovo injection of a vaccine containing serotypes 1, 2, and 3 of Marek's disease virus (MDV), a vaccine strain of serotype 1 infectious bursal disease virus (IBDV), and recombinant fowl pox vaccine with HN and F genes of Newcastle disease virus (rFP-NDV) induced protection against virulent MDV, IBDV, Newcastle disease virus, and fowl poxvirus. The multiple-agent vaccine induced specific antibodies against the viral agents present in the mixture and did not adversely affect the survival of hatched chickens. Inoculation of a vaccine containing serotypes 1, 2, and 3 of MDV and IBDV did not affect hatchability of eggs, although the addition of rFP-NDV to the mixture reduced hatchability by 23%-26%. In ovo vaccination with a vaccine containing MDV and IBDV vaccine viruses did not exacerbate the inhibitory effect of individual viral agents on humoral and cellular immune competence.     

Comparative analyses of humoral and cell-mediated immune responses upon vaccination with different commercially available single-dose porcine circovirus type 2 vaccines

The objective of this study was to compare the induction of humoral and cell-mediated immune responses by four commercially available single-dose porcine circovirus type 2 (PCV-2) vaccines. A total of 50 3-week-old piglets were assigned to five groups (10 pigs per group). Four commercial PCV-2 vaccines were administered according to the manufacturer's instructions and the piglets were observed for 154 days post vaccination (dpv). Inactivated chimeric PCV-1-2 vaccines induced higher levels of PCV-2-specific neutralizing antibodies (NA) and interferon-γ-secreting cells (IFN-γ-SC) in pigs than did the other three commercial PCV-2 vaccines. The proportions of CD4⁺ cells were significantly higher in animals vaccinated with inactivated chimeric PCV-1-2 and PCV-2 vaccines than in animals vaccinated with the two subunit vaccines. To our knowledge, this is the first comparison of humoral and cell-mediated immunity induced by four commercial single-dose PCV-2 vaccines under the same conditions. The results of this study demonstrated quantitative differences in the induction of humoral and cell-mediated immunity following vaccination.