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Litter in a room which had housed chickens and turkeys actively infected with velogenic viscerotropic Newcastle disease was no longer infectious for susceptible chickens placed there 10 to 14 days later.
Avian infectious bronchitis virus (IBV) interfered with the lethal effects of velogenic Newcastle disease virus (NDV) and embryo adapted IBV in eggs previously inoculated with non-lethal IBV. Greater interference was noted in eggs superinfected with embryo adapted IBV than velogenic NDV. The interference could be eliminated by treating the initial IBV with homologous anti-IBV serum.
A recombinant fowlpox virus expressing the hemagglutinin-neuraminidase (HN) protein of Newcastle disease virus (NDV) strain Texas was generated. Immunoprecipitation with chicken anti-NDV serum confirmed authentic expression of the HN protein. Protection of chickens from infection with NDV was observed when birds were immunized with the recombinant HN fowlpox virus by the intramuscular route after one or two inoculations. Vaccination by the ocular route with a mixture of fowlpox recombinants expressing the fusion and HN proteins did not show added protection over that seen with the individual viruses.
The effect of carrageenan (CGN) treatment on the generation of humoral and protective immune response to Newcastle disease virus vaccine was investigated in chicks. Carrageenan treatment significantly impaired the primary humoral immune response in vaccinated chicks. Further, the protective immune response in CGN-treated chicks was only 50% of that in the control vaccinated chicks. However, the post-challenge response was not altered by drug treatment. Indomethacin, a potent inhibitor of prostaglandin synthesis, was able to reverse the immunosuppressive effect of CGN. This finding suggests that prostaglandins might be involved in CGN-mediated immunosuppression in chicks.
Sera of patients with infectious mononucleosis (IM) and various other diseases were studied for agglutinins against Newcastle disease virus (NDV)-modified human group O red blood cells (NDVO) and antibodies to the NDV preparations. In agreement with previous studies, the NDVO antibodies are found in a wide variety of diseases in addition to IM, including Japanese IM-like syndrome (22%), syphilis (24%), lepromatous leprosy (30%), systemic lupus erythematosus (29%), multiple sclerosis (18%) and cancer (17%); these antibodies were also found in patients with renal allografts (29%). It was also noted that the Victoria (VIC), Roakin and Herts strains, but not B1 strain of NDV are active in the NDVO agglutination, and VIC and Roakin strains, but not B1 strain in the immunodiffusion. Immunodiffusion and enzyme immunoassay with various preparations of the VIC strain revealed that the major antigen(s) of the virus under study is carried by the hemagglutinin-neuraminidase (H-N) glycoproteins. The H-N molecule was also shown to be able to modify human erythrocytes for the agglutination by the pathologic sera.
The effects of a mesogenic strain of Newcastle disease virus on ocular and paraocular structures were studied in 10-to-12-week-old chickens inoculated conjunctivally, intraocularly, intracerebrally, or intravenously. Paraffin-embedded tissues were examined by light and fluorescent microscopy using conventional staining and immunohistochemistry. Lesions were most severe in intraocularly inoculated chickens, where a marked iridocyclochoroiditis was evident from 8-12 hours up to 21 days postinfection. Viral antigens were detected in the iris, ciliary body, Schlemm's canal, and occasionally the lens, choroid, and base of the pecten. Although optic neuritis and iridocyclochoroiditis were found in intracerebrally inoculated birds, no viral antigens were detected in the optic nerve.
An antigen has been isolated from Namalwa cells, a Burkitt lymphoma line, that was induced by Newcastle disease virus (NDV) for interferon production. The antigen was extracted by 3 M NaCl from ribonucleoprotein particles (RNP), obtained from the nuclear 0.01 M Tris extract, and was purified by hydroxylapatite chromatography, phosphocellulose chromatography, and preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Its molecular weight was 38 kilodalton (kDa) as determined by SDS-PAGE. The tryptic peptide map of 125I-labeled antigen contained seven major peptides. The antigen was not found in HeLa cells, normal human liver or in Namalwa cells that had not been induced by the virus. This result suggests that this antigen was produced in Namalwa cells as a result of induction by the NDV virus.
The clinical response of 7-day-old chickens to Newcastle disease vaccine strains V4, B1 and La Sota administered by the aerosol method was used to study the residual virulence of the strains. Parameters used to assess the severity of the clinical response were the number of sneezes recorded and the weight gain of chickens in the 10 day test period. The demeanour of the chickens was also observed. Strain V4 was less pathogenic for chickens than strain B1 which was less virulent than strain La Sota. Statistically significant differences were recorded in weight gain and the number of sneezes detected in each group. An unexpected mild respiratory disease recorded in chickens dosed with strain V4 may have been associated with administration of virus as a fine particle aerosol.
Many millions of doses of Newcastle disease vaccine have been given to chickens by two non-parenteral routes; in aerosols and in drinking water. These vaccines, that reach either or both the respiratory and digestive tracts, have afforded protection against disabling disease for millions of chickens but not without irregularity in the adequacy and duration of the response induced. Among the factors that affect the response are the nature of the delivery system (i.e. aerosol particle size), the dose received, the time involved in delivery, the environmental circumstances (i.e. ambient temperature) and the precondition of the host from the withholding of feed and water and from handling and crowding. The site of initial replication is critical, presumably because by inducing nonspecific or specific blockage of other replication sites, it shapes the immune response. Most events in the development of a vaccine-induced infection are dependent upon both thresholds and inherent periodicities. Individual host responsiveness is an interplay between the virus, environmental factors and intrinsic systems of the host.
All chickens infected by intranasal and conjunctival routes with a neurovirulent strain of Newcastle disease virus (NDV) developed pneumonitis by 4 days after infection. This was followed 6 to 12 days later by the appearance of severe encephalitis in a significant number of survivors. Histologically, the encephalitis was characterized by neuronal degeneration and perivascular inflammation. In addition, a proliferative vasculitis in the molecular layer of the cerebellum was noted after 30 days, and this persisted for at least 200 days. Although CNS signs were absent during the pneumonic stage, significant amounts of virus were present in the brains of all birds at this time, and viral antigens were easily demonstrable in neurons, glial cells, and endothelial cells. However, when the CNS disease became apparent, viral antigens could not be detected in brains and NDV could regularly be recovered only by application of cocultivation techniques. At this time, the agent was selectively present in birds exhibiting neurologic signs. No evidence for immunopathologic processes was obtained, although hemagglutination inhibiting antibody levels to NDV were elevated in birds with CNS disease. Studies of an avirulent strain of NDV that replicated in the CNS but produced no disease provided evidence that the histologic lesions and the neurologic disease were related to virus multiplication in the brain parenchyma. A mechanism of the pathogenesis of NDV encephalitis is proposed and the disease is discussed relative to other paramyxovirus-induced encephalitic syndromes.
Because of the fact that South Africa is a Newcastle disease virus (NDV)-endemic country, major concerns exist that the export of ostrich meat could transmit velogenic strains of this disease. The ability to transmit the virus could be reduced by effective vaccination of South African ostriches. In this study, two vaccination trials were conducted to assess serum antibody production in response to vaccination with La Sota strain NDV vaccines. To this end, a commercially available chicken anti-NDV enzyme-linked immunosorbent assay (ELISA) was modified for the detection of anti-NDV antibodies in ostrich serum. The results obtained with this ELISA were verified by comparison with an indirect ELISA. In the first trial, ostriches were immunized subcutaneously four times with different volumes of an inactivated vaccine and their immune response was determined from 2.5 mo up to the ideal slaughter age of 14 mo. Results indicated that ostriches responded in a dose-dependent manner and gave support for the vaccination schedule currently recommended to South African farmers. In a second trial, immunization by eyedrop with a live La Sota vaccine of 5-wk-old ostriches did not elicit a humoral immune response. The results indicate that it is highly unlikely that ostriches that have been vaccinated according to the recommended vaccination schedule can transmit the virus.
The nucleocapsid (NP) protein of Newcastle disease virus (NDV) self-assembled in Escherichia coli as ring-like and herringbone-like particles. Several chimeric NP proteins were constructed in which the antigenic regions of the hemagglutinin-neuraminidase (HN) and fusion (F) proteins of NDV, myc epitope, and six histidines (a hexa-His tag) were linked to the C-terminus of the NP monomer. These chimeric proteins were expressed efficiently in soluble form in E. coli as detected by Western blot analysis. Electron microscopy of the purified products revealed that they self-assembled into ring-like particles. These chimeric particles exhibited antigenicity of the myc epitope, suggesting that the foreign sequences were exposed on the surface of the particles. Chickens inoculated with the chimeric particles mounted an immune response against NDV, suggesting the possibility of use of the ring-like particle as a carrier of immunogens in subunit vaccines and immunological reagents.
Virus strain and age of chicken influenced the transmissibility of lentogenic strains of Newcastle disease virus (NDV). The ability of LaSota, B1, V4, CT, F, and Ulster strains to spread from cages of oronasally inoculated chickens to adjacent cages of susceptible chickens was assessed by virus isolation, serology, and immunity to challenge with virulent NDV. Although all inoculated chickens were immune to challenge, the immunity of contact chickens ranged from 100% for LaSota and CT strains to 0% for Ulster strain. The transmissibility of B1 and V4 strains for chickens 1, 4, 8, and 16 weeks old was assessed by within-cage contact infection, exposure to contaminated food and water containers, and exposure to air from infected chickens. Serology and immunity to challenge with virulent virus were used as criteria. Differences in transmissibility were observed for the strain of virus used, route of exposure, and age of chickens. Care must be used in interpreting the significance of strain differences until the effect of variables can be minimized by further improvements in design of the test procedure.
Newcastle disease virus (NDV) remains a major pathogen of poultry where highly virulent strains require reporting to the Office of International Epizootes. NDV is a paramyxovirus existing as different strains classified on the basis of severity of the disease they cause. The present study was conducted in Argentina to determine the prevalence of highly virulent velogenic NDV strains in commercial poultry farms. Tracheal and cloacal swabs from 693 flocks, representing 14% of the broiler production, were collected and pooled. A pool amplified twice in embryonated eggs presented a limited hemagglutination titer. We performed reverse transcription coupled to polymerase chain reaction to amplify fusion and matrix protein gene sequences of the isolate and the strain Trenque Lauquen, isolated in Argentina during an outbreak in 1970-71 and previously characterized as velogenic viscerotropic by biological methods. The amino acid sequences were deduced from nucleotide sequences of the amplification products and the pathotype predicted according to the sequences obtained. From the samples analyzed, we found only one type of NDV, being the isolate identified as lentogenic NDV. This strain is probably the one used in vaccination of flocks where that sample was obtained. These data have allowed us to consider a velogenic NDV-free status in Argentina's commercial poultry.
The potency of each batch of inactivated Newcastle disease virus (NDV) vaccine is measured in either a vaccination-serology or a vaccination-challenge experiment. We have developed an antigen quantification assay as an in vitro alternative for these currently prescribed in vivo potency assays. The in vitro assay consists of extraction of the viral antigens from the oil emulsion vaccines by isopropylmyristate, followed by quantification of the NDV HN-antigen in an ELISA. The analysis of 20 inactivated vaccines, representing the most common NDV-vaccines in Western Europe, indicated that large differences in antigen content exist between these vaccines. A comparison of the antigen content with the serological response after vaccination with 1/50 vaccine dose demonstrated that a reliable estimate of the potency can be made, based on the HN-antigen content of the vaccine. We therefore present our antigen quantification assay for NDV as a candidate in vitro potency assay. An international feasibility and validation study will be needed to prove the suitability and reliability of this candidate in vitro potency assay for inactivated NDV vaccines.
A sensitive and specific RT-nested PCR coupled with an ELISA detection system for detecting Newcastle disease virus is described. Two nested pairs of primer which were highly specific to all the three different pathotypes of NDV were designed from the consensus fusion gene sequence. No cross-reactions with other avian infectious agents such as infectious bronchitis virus, infectious bursal disease virus, influenza virus, and fowl pox virus were observed. Based on agarose electrophoresis detection, the RT-nested PCR was about 100 times more sensitive compared to that of a non-nested RT-PCR. To facilitate the detection of the PCR product, an ELISA detection method was then developed to detect the amplified PCR products and it was shown to be ten times more sensitive than gel electrophoresis. The efficacy of the nested PCR-ELISA was also compared with the conventional NDV detection method (HA test) and non-nested RT-PCR by testing against a total of 35 tissue specimens collected from ND-symptomatic chickens. The RT-nested PCR ELISA found NDV positive in 21 (60%) tissue specimens, while only eight (22.9%) and two (5.7%) out of 35 tissue specimens were tested NDV positive by both the non-nested RT-PCR and conventional HA test, respectively. Due to its high sensitivity for the detection of NDV from tissue specimens, this PCR-ELISA based diagnostic test may be useful for screening large number of samples.
Three-to-seven-week-old broiler-type chickens were inoculated with Newcastle disease virus (NDV) by eye-drop (ED) or intratracheally (IT), and virus isolation was attempted from oropharyngeal (oral) swabs and medium harvested from tracheal explant cultures (TEC). The TEC were maintained in screw-capped tissue-culture flasks for at least 1 month, and medium harvested at regular feeding times was assayed for NDV and NDV antibody. The earliest and latest sample times were 3 and 21 days after NDV inoculation. The three experiments done were: Expt. 1, infection of nonvaccinates with NDV strain La Sota; Expt. 2, infection of NDV vaccinates and nonvaccinates with NDV strain Largo; and Expt. 3, infection of NDV vaccinates and nonvaccinates with NDV wild-type strain Kansas-Manhattan (KM) and two temperature-sensitive (ts) clones derived by J. S. Youngner from the KM strain. All experiments yielded similar results. On day 3 postinoculation (PI), most chickens were shedding virus recoverable by oral swabs and detectable in harvests from TEC prepared on that day. On day 7 PI, there was a sharp reduction in the frequency of virus-positive oral swabs, but there was no decline in the frequency of virus-positive TEC. On day 14 PI or later, all oral swabs and TEC were virus-negative, except for one chicken in Expt. 3 that was oral-swab-positive. There was no evidence of NDV persistence in the TEC of oral-swab-negative chickens on or after day 14 PI. The results of these experiments are in contrast with previous reports of the detection of latent NDV by virus isolation from harvests of TEC prepared 18 or more days PI. The ts clones of strain KM used in Expt. 3 induced a markedly poorer antibody response and were shed for a shorter time than the KM parental virus.
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