Effects of avian infectious bronchitis virus (Arkansas strain) on vaccinated laying chickens

Twenty-four-week-old white leghorn layers were inoculated subcutaneously with a killed Newcastle-infectious bronchitis (Massachusetts type) virus (MIBV) vaccine. The birds were challenged 194 days later intraocularly with Arkansas strain of infectious bronchitis virus (AIBV). The challenged hens laid significantly (P less than 0.005) fewer eggs than the unchallenged layers, and the eggs laid by the challenged groups weighed significantly less (P less than 0.001) than those laid by the unchallenged groups. Further, the internal quality (Haugh units) and shell quality of eggs laid by the challenged hens were significantly (P less than 0.005) inferior to the quality of eggs from unchallenged hens, and the challenged hens laid more soft-shelled, misshapen, and small-sized eggs than the unchallenged hens. The Arkansas serum hemagglutination-inhibition (AIBV-HI) titers of challenged birds increased continuously through 29 days post-challenge. The MIBV hemagglutination-inhibition (MIBV-HI) titers of killed-MIBV-vaccinated birds decreased during the same period. The study indicates that killed MIBV vaccine offered no protection to birds exposed to AIBV. The same vaccine was quite effective against a homologous (MIBV) virus challenge.     

Efficacy of infectious bronchitis virus vaccines against heterologous challenge

Twenty-four-week-old white Leghorn layers were inoculated subcutaneously with a killed Newcastle disease-infectious bronchitis (Massachusetts type) virus (MIBV) vaccine. Twenty-eight weeks after vaccination, the birds were challenged intraocularly with the Arkansas strain of infectious bronchitis virus (AIBV) to determine the effects of heterologous virus exposure on egg production, egg quality and serum antibody response of the birds. The challenged hens laid significantly (P less than 0.005) fewer eggs than the unchallenged layers. Eggs laid by the unchallenged groups weighed significantly more (P less than 0.005) than those laid by the challenged groups. Further, the internal quality (Haugh units) and shell quality of eggs laid by the AIBV-challenged hens was significantly (P less than 0.005) inferior to those from the unchallenged hens. In addition, the AIBV-challenged hens laid more soft-shell, misshapen and small eggs than the unchallenged hens. The Arkansas serum haemagglutination inhibition (AIBV-HI) titres of AIBV challenged birds increased up to four weeks after challenge. The corresponding MIBV haemagglutination-inhibition (MIBV-HI) titres decreased during the same period. The study indicates that killed MIBV vaccine offered no protection to birds exposed to heterologous AIBV.     

CAV与REV共感染SPF鸡对疫苗免疫反应的抑制作用

用1日龄SPF鸡人工感染鸡贫血病毒(CAV)和禽网状内皮增生病病毒(REV),探讨病毒感染对鸡体疫苗免疫反应的影响。结果表明,在用禽流感病毒(AIV,H5和H9)疫苗免疫后,CAV与REV单独感染均显著抑制了鸡体对H5和H9亚型禽流感病毒灭活疫苗的HI抗体反应,在CAV与REV共感染后,这种抑制作用更为明显。CAV单独感染后鸡体对新城疫病毒(NDV)和传染性法氏囊病病毒(IBDV)疫苗的免疫反应受到抑制,但与对照组在统计学上的差异不显著,然而,CAV可以显著加重REV感染对鸡体在NDV和IBDV疫苗免疫后抗体反应的抑制作用。从而证实CAV与REV共感染在疫苗免疫抑制上有协同作用。     

REV和ALV-J感染对肉用型鸡细胞免疫反应的影响

以网状内皮增生症病毒（REV）和禽白血病病毒J亚群（ALV-J）单一感染和共感染1日龄商品代AA肉鸡后不同时间,采用3H-TdR掺入法测定血液和脾脏的淋巴细胞对ConA的增殖反应能力。结果表明,血液淋巴细胞对ConA增殖反应能力在REV和ALV-J共感染后7 d均下降,REV单一感染组在感染后17、37 d均极显著低于对照组（P〈0.01）,ALV-J单一感染组也呈现下降趋势。在脾淋巴细胞反应中,REV感染组在感染后37 d极显著降低（P〈0.01）,ALV-J组显著降低（P〈0.05）。REV和ALV-J共感染抑制淋巴细胞对ConA增殖反应较单一感染强,效应期也较长,在感染后37 d,共感染对血液和脾淋巴细胞反应的抑制作用均大于REV和ALV-J的单一感染（P〈0.05）。在感染后273、7 d检测NDV抗体,单一感染组降低显著（P〈0.05）,而共感染组下降极显著（P〈0.01）,且显著低于单一感染组（P〈0.05）。本研究表明REV、ALV-J感染不仅能抑制体液免疫反应,也能抑制细胞免疫反应,且共感染比单一感染的抑制作用更强。     

鸽新城疫病毒的分离及鸽群自然感染状况的调查

将在北京某信鸽群采集的两只具神经症状的病鸽脑组织悬液接种ＳＰＦ鸡胚后，分离出二株病毒分离物ＰＢ９６０１和ＰＢ９６０２，通过对鸡红血球的血球凝集试验，用已知鸡新城疫病毒（ＮＤＶ）高免血清任务在球凝集抑制试验（ＨＩ）及２～３月龄鸽的攻毒试验，证明这两个毒株为对鸽呈高致病性的ＮＤＶ。交叉ＨＩ试验表明，鸽ＮＤＶ分离株与鸡ＬａＳｏｔａ株间有很高的血清交叉反应，但也存在着一定抗原性差异。对扬州地区若鸽群中２－     

Hemagglutination by psittacine beak and feather disease virus and use of hemagglutination inhibition for detection of antibodies against the virus.

Conditions for psittacine beak and feather disease (PBFD) virus hemagglutination and hemagglutination-inhibition (HI) test reactions are defined. The PBFD virus was found to hemagglutinate cockatoo and some guinea pig erythrocytes. The HI test was used to assay serum antibody titer in birds with active PBFD virus infections and in others that had been exposed to diseased birds. On the basis of HI antibody titers in psittacine birds that had been exposed to PBFD virus, but remained clinically normal, we suggest that some birds exposed to the virus are able to mount an effective immune response. Birds with active PBFD virus infections had lower antibody values than did birds that had been exposed to the virus, but remained clinically normal. On the basis of these findings, the ability to develop a suitable HI antibody response may be crucial in determining the disease status of susceptible birds exposed to the PBFD virus. If HI antibodies are found to have neutralizing activity, then the fact that a high HI titer was induced in birds inoculated with purified PBFD virus might suggest that an immunization program would be effective in preventing PBFD virus infections.     

Indirect method for prediction of hemagglutination inhibition antibody titers to Newcastle disease virus in chickens by titration of antibodies in egg yolk.

Attempts were made to establish methods for indirect prediction of hemagglutination inhibition (HI) antibody titers to Newcastle disease virus (NDV) in sera of laying hens and day-old chicks by determining if these are correlated to HI titers in egg yolks. For this purpose, geometric means of HI antibody titers in sera from 60 hens, yolks from 60 matched eggs, and sera from 180 day-old chicks of an identical vaccination program were measured and plotted. There was a significant correlation between HI antibody titers in yolks (X) and hens (Y), with a linear regression of Y = 23.24 + 0.47X and a correlation coefficient of r = 0.65. The linear regression between HI antibody titers in yolks (X) and chicks (Y) was Y = 6.33 + 0.36X (r = 0.58). Immunity to NDV in hens and their offspring can be maintained effectively, and the proper time for the vaccination or booster can be determined by reference to HI titers predicted from the linear regression in the present study. The approach of testing egg yolk for HI titers provides a feasible alternative to determining HI titers from blood samples and eliminates stress in birds during blood sampling.     

Improvements to the hemagglutination inhibition test for serological assessment of recombinant fowlpox-H5-avian-influenza vaccination in chickens and its use along with an agar gel immunodiffusion test for differentiating infected from noninfected vaccinated animals

In general, avian influenza (AI) vaccines protect chickens from morbidity and mortality and reduce, but do not completely prevent, replication of wild AI viruses in the respiratory and intestinal tracts of vaccinated chickens. Therefore, surveillance programs based on serological testing must be developed to differentiate vaccinated flocks infected with wild strains of AI virus from noninfected vaccinated flocks in order to evaluate the success of vaccination in a control program and allow continuation of national and international commerce of poultry and poultry products. In this study, chickens were immunized with a commercial recombinant fowlpox virus vaccine containing an H5 hemagglutinin gene from A/turkey/Ireland/83 (H5N8) avian influenza (AI) virus (rFP-H5) and evaluated for correlation of immunological response by hemagglutination inhibition (HI) or agar gel immunodiffusion (AGID) tests and determination of protection following challenge with a high pathogenicity AI (HPAI) virus. In two different trials, chickens immunized with the rFP-H5 vaccine did not develop AGID antibodies because the vaccine lacks AI nucleoprotein and matrix genes, but 0%-100% had HI antibodies, depending on the AI virus strain used in the HI test, the HI antigen inactivation procedure, and whether the birds had been preimmunized against fowlpox virus. The most consistent and highest HI titers were observed when using A/turkey/Ireland/83 (H5N8) HPAI virus strain as the beta-propiolactone (BPL)-inactivated HI test antigen, which matched the hemagglutinin gene insert in the rFP-H5 vaccine. In addition, higher HI titers were observed if ether or a combination of ether and BPL-inactivated virus was used in place of the BPL-inactivated virus. The rFP-H5 vaccinated chickens survived HPAI challenge and antibodies were detected by both AGID and HI tests. In conclusion, we demonstrated that the rFP-H5 vaccine allowed easy serological differentiation of infected from noninfected birds in vaccinated populations of chickens when using standard AGID and HI tests.     

Serological examination and egg production of progeny of fowl experimentally infected with egg drop syndrome 1976 virus

Following EDS'76 virus (BC14 virus) infection of breeder chickens by the conjunctival route, vertical transmission occurred in the first week after infection. In the progeny which had been infected with EDS'76 virus by the vertical route, increasing haemagglutination inhibiting (HI) titres to BC14 virus and increasing numbers of birds with HI titres were observed from 3 weeks to 15 weeks of age. Sixty-one per cent of the hens and 77 per cent of the cocks had 2 log HI BC14 virus titres exceeding 4 at an age of 15 weeks. Some birds which han been serologically negative throughout the rearing period, seroconverted between 25 and 28 weeks of age. This phenomenon occurred in hens as well as in cocks. Simulation of stress twice during the laying period by injection of corticosteroid hormone did not increase the number of birds serologically positive to EDS'76 virus. EDS'76 was observed in the group of hens that was vertically infected, since egg production was significantly depressed between 28 and 34 weeks of age. Probably this was mainly the results of a production drop in the hens showing serconversion at 27 or 28 weeks of age. In this group of fowl vertically infected with EDs'76 virus, serologically positive birds appeared to be protected for the greater part to BC14 virus challenge at 50 weeks of age, while negative birds seemed to be fully susceptible. Chicks hatched from eggs collected in the third and fourth week after infection of the dams had maternal antibodies. Fertility and hatchability of apparently normally shelled eggs seemed not to be affected after BC14 virus infection of the dams. Intensive contact with contaminated faeces is probably an indispensable condition for lateral transmission of the virus.     

新城疫单抗ELISA试剂盒监测免疫鸡群中新城疫强毒

应用新城疫（ND）单抗ELISA试剂盒对2个免疫鸡群中ND强毒感染情况及个体感染强毒后排毒动态跟踪监测，并平等测定其HI抗体效价。共采集泄殖腔棉拭子和血液对应样品2317份。结果表明：HI效价2－14之间的个体均可检出强毒，其中HI效价在6以下和11以上的个体强毒检出率都较高。HI效价在6以上的个体仍角感染强毒，强毒感染导致HI抗体水平上升，且感染前低者上升速度较快，幅度亦较大；并且发现排毒个体的高水平抗体是强毒感染所致。个体感染强毒后排毒过程可长达3周，而且感染前抗体水平低者排毒时间相对较长。强毒一旦侵入鸡群便可在群内巡回传播，长期维持下来。     

Serological examination and egg production of progeny of fowl experimentally infected with Egg Drop Syndrome 1976 virus

Summary

Following EDS'76 virus (BC14 virus) infection of breeder chickens by the conjunctival route, vertical transmission occurred in the first week after infection. In the progeny which had been infected with EDS'76 virus by the vertical route, increasing haemagglutination inhibiting (HI) litres to BC14 virus and increasing numbers of birds with HI litres were observed from 3 weeks to 15 weeks of age. Sixty‐one per cent of the hens and 77 per cent of the cocks had ²log HI BC14 virus litres exceeding 4 at an age of 15 weeks.

Some birds which had been serologically negative throughout the rearing period, seroconverted between 25 and 28 weeks of age. This phenomenon occurred in hens as well as in cocks. Simulation of stress twice during the laying period by injection of corticosteroid hormone did not increase the number of birds serologically positive to EDS'76 virus.

EDS'76 was observed in the group of hens that was vertically infected, since egg production was significantly depressed between 28 and 34 weeks of age. Probably this was mainly the result of a production drop in the hens showing seroconversion at 27 or 28 weeks of age.

In the group of fowl vertically infected with EDS'76 virus, serologically positive birds appeared to be protected for the greater part to BC14 virus challenge at 50 weeks of age, while negative birds seemed to be fully susceptible. Chicks hatched from eggs collected in the third and fourth week after infection of the dams had maternal antibodies. Fertility and hatchability of apparently normally shelled eggs seemed not to be affected after BC14 virus infection of the dams. Intensive contact with contaminated faeces is probably an indispensable condition for lateral transmission of the virus.     

Evaluation of different methods of inactivation of Newcastle disease virus and avian influenza virus in egg fluids and serum

Viruses conveyed in shipments of eggs, viral diagnostic reagents, or avian serum samples are a potential hazard for susceptible poultry. Different methods of treatment of those materials to eliminate the hazard of virulent and avirulent strains of Newcastle disease virus (NDV) or avian influenza virus (AIV) were evaluated. The NDV strains tested were more thermostable than the AIV strains. The results suggest that standard pasteurization methods would not reliably inactivate the concentrations of NDV used. beta-Propiolactone (BPL) (greater than or equal to 0.025%) inactivated NDV or AIV in allantoic fluid, but higher concentrations were needed to inactivate virus diluted in serum. Hemagglutination (HA) of NDV and AIV and hemolysis (HL) activity of NDV were reduced or eliminated by 0.4% BPL. Formalin (greater than or equal to 0.04%) inactivated either virus but adversely affected HA and HL activity. NDV or AIV was inactivated by binary ethylenimine (BEI) (0.01 M) with no adverse effect on HA or HL. Heat (56 C) or BEI (0.01 M) had no apparent effect on hemagglutination-inhibition (HI) titers of NDV and AIV antisera, the effect of formalin (0.1%) was variable, and BPL (greater than or equal to 0.25%) depressed the HI titers of both antisera. The optimum method should achieve virus inactivation without harming the treated material.     

Protection of chickens against highly pathogenic avian influenza virus (H5N2) by recombinant fowlpox viruses.

Two recombinant fowlpox viruses containing the avian influenza H5 hemaglutinin (HA) gene were evaluated for their ability to protect chickens against challenge with a highly pathogenic isolate of avian influenza virus (H5N2). Susceptible chickens were vaccinated with the parent fowlpox vaccine virus or recombinant viruses either by wing-web puncture or comb scarification. Following challenge 4 weeks later with highly pathogenic avian influenza virus, all birds vaccinated by the wing-web method were protected by both recombinants, while 50% and 70% mortality occurred in the two groups of birds vaccinated by comb scarification. Birds vaccinated with the unaltered parent fowlpox vaccine virus or unvaccinated controls experienced 90% and 100% mortality, respectively, following challenge. Hemagglutination-inhibition (HI) antibody levels were low, and agar-gel precipitin results were negative before challenge. Very high HI titers and positive precipitating antibody responses were observed in all survivors following challenge.     

Use of egg yolk to determine antibody levels in chickens inoculated with a hemagglutinating duck adenovirus (adenovirus 127-like)

Chickens were experimentally infected with a duck adenovirus that has been shown to be serologically indistinguishable from Adenovirus 127. Sera and eggs were collected at intervals after exposure for antibody determination by the hemagglutination-inhibition (HI) test, the enzyme-linked immunosorbent assay (ELISA), and the immunodiffusion (ID) test. Egg yolks were processed for use in the serological tests by (a) dilution in phosphate-buffered saline (PBS), (b) extraction of the water-soluble fraction with chloroform, or (c) freezing and thawing PBS-diluted yolks and testing the supernatant fluid. HI antibody titers from serum and extracted yolk were similar except during the initial 2 weeks, when yolk antibody levels were low or absent. Chloroform-extracted yolks were suitable material for the HI, ELISA, and ID tests. Heat inactivation of the chloroform-extracted yolk had no effect on titers.     

Evaluation of the infectivity, length of infection, and immune response of a low-pathogenicity H7N2 avian influenza virus in specific-pathogen-free chickens

The H7N2 subtype of avian influenza virus (AIV) field isolate (H7N2/chicken/PA/3779-2/97), which caused the 1997-98 AIV outbreak in Pennsylvania, was evaluated for its infectivity, length of infection, and immune response in specific-pathogen-free (SPF) chickens. The composite findings of three clinical trials with various concentrations of virus indicated that this H7N2 subtype contained minimal pathogenicity for chickens. The concentration of the virus in the inoculum proved critical in the establishment of a productive infection in a chicken. Seven-day-old SPF chickens were not infected when inoculated with 10(0.7-2.0) mean embryo lethal dose (ELD50) of the H7N2 virus per bird. At this dose level, the immune response to this virus was not detected by the hemagglutination-inhibition (HI) test. Nonetheless, chickens at ages of 5 and 23 wk old tested were successfully infected when exposed to 10(4.7-5.7) ELD50 of H7N2 infectious doses per bird by various routes of administration and also by direct contact. Infected birds started shedding virus as early as 2 days postinoculation, and the period of virus shedding occurred mostly within 1 or 2 wk postinoculation (WPI). This H7N2 subtype of AIV induced a measurable immune response in all birds within 2 wk after virus exposure. Antibody titers were associated with AIV infectious doses and age of exposure of birds. Challenge of these infected birds with the same H7N2 virus at 5 and 10 WPI indicated the infective virus was recoverable from cloacal swabs at 3 days postchallenge and disappeared thereafter. In these challenged birds, the antibody levels as measured by the HI test spiked within 1-2 wk.     

Hemagglutination-inhibition test applied to the study of akabane virus infection in domestic animals

Some factors affecting the hemagglutination-inhibition (HI) reaction with Akabane virus were investigated and an HI test developed. The test was proven to be useful in studies of antibody responses in cattle and other domestic animals infected with Akabane virus. HI antibody titers of individual animals were shown to be closely correlated with their neutralizing antibody titers and to remain undiminished for a relatively long time. In some early sera from domestic animals infected with Akabane virus, HI antibody sensitive to 2-mercaptoethanol was demonstrated.     

Passive immunization using purified IgYs against infectious bursal disease of chickens in Pakistan

Infectious bursal disease (IBD) is an acute and highly contagious disease of young chickens caused by Birnavirus. Mortality of infected birds can be best prevented if injected with antibodies. The present study was an attempt to raise specific hyper-immune polyclonal antibodies against IBD virus in Pakistan. Commercial layers divided into four groups were injected with IBD vaccine subcutaneously according to four different treatment regimens. Eggs were collected daily and antibodies were purified from yolk with dextran sulphate. Titers of antibodies in serum and yolk were evaluated with enzyme linked immunosorbant assay and agar gel precipitation test. Antibody titers were significantly higher in yolk than serum. Eggs collected at 28 days post-vaccination had maximum antibody titers. Of treatment regimens, T₃ was found to be most effective for hyperimmunization. Lyophilized antibodies stored at 4℃ did not lose their activity till the end of experiment. IBD virus infected birds were injected with purified antibodies which induced 92% recovery as compared to control birds. The study implicates that the purified antibodies may be useful as a therapeutic agent to cure IBD infected birds.     

Generation of a genotype VII Newcastle disease virus vaccine candidate with high yield in embryonated chicken eggs

To generate a genotype VII Newcastle disease virus (NDV) vaccine with high yield in embryonated chicken eggs, we selected genotype VII NDV strain JS5/05, which possesses a high virus titer in embryos as the parental virus. Using reverse genetics, we generated a genetically tagged derivative (NDV/AI4) of JS5/05 by changing the amino acid sequence of the cleavage site of the F0 protein. Pathogenicity tests showed that NDV/AI4 was completely avirulent. NDV/AI4 was genetically stable and replicated efficiently during 10 consecutive passages in embryos. More importantly, serologic assays showed that oil-emulsion NDV/AI4 induced higher hemagglutination inhibition (HI) titers against the prevalent virus than oil-emulsion LaSota vaccine in chickens and geese. Moreover, NDV/AI4-induced HI titers rose faster than those elicited by LaSota in chickens. Both NDV/AI4 and LaSota provided protection against clinical disease and mortality after the challenge with the genotype VII NDV strain JS3/05. However, NDV/AI4 significantly reduced virus shedding from the vaccinated birds compared to LaSota. Taken together, these results suggest that NDV/AI4 can provide better protection than LaSota and is a promising vaccine candidate against genotype VII NDV.     

Protection levels of vaccinated pigeons (<Emphasis Type="Italic">Columba livia)</Emphasis> against a highly pathogenic newcastle disease virus strain

The purposes of this study were to model a vaccination regimen for Newcastle disease virus (NDV) in pigeons, and to evaluate the susceptibility and behavior of vaccinated birds against a highly pathogenic NDV Brazilian strain. Antibody response was assessed by means of hemagglutination inhibition test (HI), and viral genome excretion by means of RT-PCR. Vaccinal strains (La Sota and Ulster) induced high antibody titers without any adverse effects, both in inoculated and in sentinel birds. A viral strain pathogenic for chickens did not produce clinical signs of the disease in experimentally infected pigeons. Only 4 out of 10 vaccinated pigeons shed NDV genome, and just for two days. Results confirmed the high infectivity of the vaccinal strains used, as all nonvaccinated pigeons showed antibody titers as high as those of vaccinated birds.     

Immune response to avian leukosis virus infection in chickens: Sequential expression of serum immunoglobulins and viral antibodies

Chickens of a 15I₅ × 7₂ cross that produces endogenous Rous associated virus (RAV-0) were infected with subgroup A lymphoid leukosis virus (RAV-1). Within 3 weeks, before RAV-1 neutralizing antibodies were detected, significantly higher levels of serum immunoglobulin G (IgG) were found in infected birds than in uninoculated hatchmates. Immunoglobulin M was significantly elevated only during the late leukotic state. Although most of the inoculated birds tested had RAV-1 neutralizing antibodies, no correlation was found between IgG levels and antibody titers. Tolerance to endogenous virus (RAV-0) and viral group-specific antigen was apparently abrogated by RAV-1 inoculation because significantly higher percentages of iodinated envelope glycoprotein (gpE) of RAV-0 and a viral structural antigen of mol. wt 19,000 daltons (p 19) were precipitated by sera from inoculated birds than from control birds.